anus

eXVlI, Summer 2974

Energy and the Sea

Solar flare, estimated to contain
more energy than all that used
on Earth during several
decades. Photo was taken
aboard Skylab on June 15, 1973.
(The Perkin-Elmer Corporation)

Until quite recently, concern over the world's energy problems has centered on
production and conservation of fossil and fission fuels. Energy from the sea has been
thought of principally in terms of intensifying the search for oil and gas on the continental
shelves.

Today, with conventional supplies trammeled by natural and political constraints,
the suspicion is growing that the energy crisis we have been experiencing is merely a
prelude to what will surely come in the absence of sustained efforts to husband
nonrenewable resources while developing renewable ones. The seas become far more
important in this context. There is extractable, renewable energy in their tides, currents,
and temperature differences, in the winds that blow over them, in the very waters
themselves. There is, as well, the likelihood of significant oil finds under the ocean floor
and the possibility of siting nuclear power plants offshore.

Scientists and engineers have known of the marine energy potential for years,
in some instances for centuries. It has taken the spur of shortages and embargoes to
translate that knowledge into programs that in time may give a new meaning to the old
term of "sea power." Now that we have the desire to extract energy from the oceans,
it remains to be seen if we have the stewardship to do so wisely.

William H. MacLeish
Editor

COVER: William G. Metcalf

NOTE: Readers who rubbed their eyes over last issue's cover
were right to rub. The photograph of Hurricane Ava was
reversed for design purposes, but the explanatory caption was
not included.

Oceanus

Volume XVII, Summer 1974

The Woods Hole Oceanogiaphic Institution
Woods Hole, Massachusetts

ENERGY: NATURAL LIMITS AND ABUNDANCES
by William S. von Arx -- We have to learn to live
with the earth, not just on it. O

PROVINCES OF PROMISE by K. O. Emery
Despite natural and governmental hostility,
new supplies of oil and gas are likely to be
developed, some under the deep ocean floor. 1/1

USING TWO RENEWABLES by William E.
Heronemus -- Wit idpo we r and ocean thermal
differences are under intense study as energy
sources free of depletion problems.

HYDROGEN TO BURN by Howard P. Harrenstien
Abundantly available in salt water and fresh,
hydrogen comes close to being the ideal
synthetic fuel. Q Q

TIME AND TIDE by F. L. Law ton

Tidal power is once again attracting attention,

thanks in part to recent shifts in power

economics.

CURRENT FROM THE CURRENT by Harris
B. Stewart, Jr. - The Florida Current is being
studied as a source of supplementary power
for booming south Florida. -sX

SEA VS. STRUCTURE by Stephen C. Dexter
Protecting metals from the environment is a
cost not to be overlooked when doing
business at sea.

OFFSHORE NUCLEAR POWER STATIONS
by Michael W. Golay — Nuclear power plants
soon may be located offshore if legal,
financial, and safety problems can be resolved. A /C

Copyright © 1974 by Woods Hole Oceanographic Institution

Energy:

^Natural Limits

^ itei JL A.-kJU-

William S. vonArx

V V ith the decline of ancient civilization -
the sucessive incinerations of the great
Library of Alexandria in the fourth century
and the Moslem conquest of Egypt in the
seventh — it remained for Persian and Arabian
scholars to assemble, record, and continue to
enlarge knowledge. The western world became

aware of this heritage during the Crusades of
the twelfth century when translations of
Arabic records became available in Latin and
various other tongues. These events provided
the intellectual fuel for the Renaissance and
eventually the industrial revolution, which,
according to some, has about run its course.

Today, the Arabs are again influencing
history. They are making us realize that
industrialized society is critically dependent
upon the natural abundance of fuels. Indeed,
by their petroleum export policies, they have
forced us to reexamine our patterns of living
and our demands upon the resources of the
earth.

Water power, wood, coal, and later
petroleum and natural gas provided the energy
needed to advance the industrial revolution
and the profound social and ethical changes it
provoked. Now we have a new social order,
but the fuels we use to support it are running
low. In the past century we probably have
consumed more than half of the oil and gas
in the geologic column and a smaller fraction
of its coal. However much remains, the
accumulation rate of these resources is so
slow that they must be considered finite. So,
too, must nuclear fuels. Any finite resource,
however carefully husbanded, will eventually
become exhausted. What we need is sustained,
renewable energy and the self-discipline to
live within its limits of abundance.

But first, what is energy? In physics the
word means "a capacity for performing
work.'1 But the definition doesn't say how
long it takes to get the work done. When
energy is expended or work is done in a
specific interval of time, the "rate of doing
work" is called power, and that is really the
subject of this article.

Power can be expressed in a variety of
units. All are exactly related and can be
converted one to another; but it is simplest
to use just one, the watt, as the unit of power.
One watt is energy received or delivered at
the rate of one joule per second. The joule is
a metric unit of work or energy, and the
second is, for present purposes, the interval
of time swept out on the dials of ordinary
clocks and watches. Briefly then, one watt
of power is one joule of "energy" per second.

A watt isn't very much power — think of
a 100-watt reading lamp, then of a 140-
horsepower automobile delivering a little over
100,000 watts of power. In contrast, global

power levels are very large, so large that they
will be expressed here in powers of ten - - 103
being a thousand watts, 106 a million, 109 a
billion, and so on -- the exponent giving the
number of zeros involved. The power of the
sunshine reaching the earth is some 1017
watts; the present power demand of world
civilization is close to 1013 watts; and the
hydroelectric power we use totals about 1011
watts. (The words "some" and "about"
represent uncertainty of precise numbers.
Actual power levels may be double, triple, or
quadruple these estimates, but not ten times
as great; they thus remain within the same
order of magnitude.)

It may be helpful to recognize that
hydroelectric power, even if doubled or
tripled, still yields 1011 watts, or only about
one percent of present needs. It would take
a one-hundred-fold increase in developed
water power to run our world at present
power levels, but there simply isn't that much
more water power available — even if all the
snow and rainfall over the globe were taken into
account. This does not mean that hydroelectric
generators cannot add to the world supply of
very useful power; but it suggests quite
emphatically that the world's power demand
cannot be satisfied by that "means alone, and
that a search for alternative resources is best
guided by the total power available in various
other natural systems. The word "natural"
is used advisedly.

The power consumed in our industrialized
and urbanized societies is all finally transformed
into heat. If this heat is added to that provided
by the sun, it too must be radiated away into
space. The balance of heating and cooling in
nature is maintained by energetic exchanges
within the solid earth, oceans, and
atmosphere, and in the growth and decay
cycles of life and death among plants and
animals. Modern civilization operates at a
power level of 1013 watts, with a consequent
heat production (mainly from fossil fuels)

Hydroelectric power, even if doubled or tripled, could
provide only about one percent of current global needs.
(EPA-Documerica, Lyntha Scott Eiler)

HP • JBBW . " .,._

I i

which disturbs the solar-terrestrial heat
balance by only 0.01 percent — seemingly a
tolerable level except, possibly, in instances
of unusual heat concentration, such as the
thermal islands produced by large cities. Were
our power production to be increased to 1014
(0.1 percent of the heat balance) or 1015 (one
percent) watts by adding heat to the solar-
terrestrial balance, significant alterations of
climate could ensue. Whether these could be
beneficial or harmful depends on factors
outside the scope of this article.

It seems important, then, that the fossil
fuel era has shown us the tolerable upper
limit in the addition of heat to the earth and
taught us that further power demand must be
placed on diversionary methods applied to
cycles of energy exchange maintained
naturally by the solar-terrestrial heat balance.
The latter instruction tells us what to look
for in the way of alternatives, and what upper
limits of power production can be sustained.
We would be very clever indeed if we could
divert as much as 10 percent of the solar-
terrestrial energy flux at the earth's surface
into technologically useful forms. This
would amount to some 1015 watts, which may
be considered our "power ceiling" by
diversionary methods. For nuclear and other
exotic methods that add heat to the system,
the power ceiling probably should not be
above 1013 watts to preserve the balance of
climate.

World climates are fragile, especially in
the polar regions. The atmosphere is probably
the most sensitively balanced part of the
world system, one which can show strongly
nonlinear responses to energetic change (see
Oceanus, Spring 1974). The latent heat of
evaporation and precipitation is particularly
important to the regimen of weather. The
oceans store heat and serve as a ponderous
buffer in the atmospheric water balance, thus
stabilizing its behavior. But the resources of
heat in the oceans cannot be overly taxed, if
their store of heat is too greatly altered, their
circulations will be disturbed and in turn
disturb the atmosphere and the regimen of

climate. On land, it is the rocky surfaces, soil
color and moisture, vegetation, and even the
works of man which enter this complicated
scheme of balances — all driven by the solar
flux. It can be seen, therefore, how carefully
energy diversion must be practiced at power
levels approaching that of the solar flux. But
how much power does nature provide on a
renewable basis?

The disc of the earth intercepts about
1017 watts of solar energy, of which some

'Ml

Man uses a tiny fraction of power recoverable from agricultt-

1016 watts is received at the rotating surface.
The earth's surface is also warmed by
radiogenic and primordial heat from its
interior. A good deal of energy is involved
in these latter processes, but the flux is not
large — about 1010 watts — and is accessible
only in certain tectonically active regions,
such as the "ring of fire" around the Pacific
Basin, the East African rift, and in the mid-
ocean ridge system and its branches into the

Mediterranean Sea. Another source of
energy is gravitation -- the power of the
luni-solar tide, especially as it moves the body
of the ocean waters relative to the solid
earth (see page 30). Here again, we find a
total energy of some 1010 watts, and that's
all there is on a day-to-day basis!

Demographic projections also enter the
picture. Within a century, the world
population may grow from the present 4
billion to perhaps 10 billion. Some 1012 watts

oduce.

EPA-Documerica, Charles O'Rear

will be needed as food for the subsistence of
10 billion souls, and 1014 watts if they all are
to live what we now consider a "good life."
The question before us is: how can we meet
these demands and do so without adding
more than 1013 watts of "new" energy to the
solar-terrestrial balance?

To begin with, we can rule out as general
solutions to the energy problem all those
resources having a world total yield below the

subsistence requirements of 10 billion people.
This metabolic energy demand can be provided
by the solar flux in the production of edible
carbohydrates, proteins, and fats in plants at
the base of the food chain. But the good life
requires more than subsistence levels of
energy. However large these demands may
be, there are several possible ways of meeting
them, wholly or in part:

Source

Direct solar energy (received at

earth's surface)
Photosynthesis
Organic decomposition
Available ocean heat
Available wind energy
Precipitation
Hydroelectric power

Total Power in Watts

1016

10I3+

1013+

1013

1012

1012

10n

This does not mean that geothermal energy at
1010 watts, the kinetic energy of ocean
currents or tides at 1010 watts, and other
"renewable" resources are to be overlooked.
Each can serve local needs and reduce
some of the remaining demand. But our
quarry in this discussion is the identification
of possible alternative resources which are
clean, renewable, and capable of sustaining us
indefinitely at least at present levels of power
demand.

Direct conversion of solar energy into
electrical or other more useful forms of power
is attractive because the present world power
demand could be met by dedicating less than
one percent of the world's surface area to
this process. But there are difficulties with
the day-night effect, which requires
enormous storage facilities. The production
of hydrogen gas by electrolysis of water is
often suggested as a practical means of both
storage and distribution. There are economic
problems, too, in that the present technology
of collection and conversion is not easily
extended to large-scale operations at
reasonable costs. For these reasons, it seems
better to await developments rather than to
discuss the problem of direct conversion of
solar energy at this writing. Instead, we will
look into the natural processes that derive

their energies from the sun to see what they
have to offer.

Surface air flow (see page 20) has been
used as a source of power for ships since the
rise of civilization and, on land, for milling
grain and pumping water since about the
12th century. It is surprising that this power
source has not been the subject of intensive
exploitation and technological innovation
until recently, and even now it is employed
only on a domestic or light industrial scale.
Adaptations of the controllable pitch
propeller and the air turbine have been shown
to produce power in significant quantities
when the wind blows. However, owing to the
variability of wind speed and incidence of
calm, it has been necessary in electrical
systems to provide a buffer between the
generator and the load. Several kinds of
buffer have been proposed. One is simply a
bank of batteries. More recently it has been
suggested that energy be stored in high-
capacity rotors and even transported by
them. Electric power may also be stored by
electrolyzing fresh water into its component
gases, hydrogen and oxygen, which when
liquefied and bottled, or simply pumped
through pipelines, could be burned at the
place and time of demand to produce not
only energy but much needed pure water.
But is the wind energetic enough to satisfy
our needs?

The kinetic energy of the world's wind
systems amounts to a staggering 1020 watts.
This represents a stored resource, however,
which can be drained at no more than its
replenishment rate if it is to perform as a
renewable resource. Thus, we are concerned
with the "available" kinetic energy of winds,
replenished at a power level not exceeding
the solar flux at the surface, 1016 watts,
because the atmospheric circulation is driven
mainly by heating from below.

Meteorological evidence shows that the
world average wind speed in the lower
atmosphere is about 10 meters per second.
The density of surface air being near 1.1
kilograms per cubic meter, it follows that the

maximum available kinetic energy of wind
power averages near 500 watts per square
meter of collected flow.

At higher levels in the atmosphere, the
average wind speed is increased, but the air
density is decreased according to the Gas Law.
The increase of wind speed with height is
approximately logarithmic in the boundary
layer but may rise to 100 meters per second
or more in the jet stream. The height of this
feature is so great, near 10 kilometers, that it
is difficult to imagine reasonable methods for
capturing its kinetic energy. Moreover, the
flow meanders across a wide band of middle
latitudes. Alternatively, there are valley winds
and orographic effects, such as the "Bishop
wave" in the lee of the Sierra Nevada, which
are accessible at mountain-top level. Mountain
peaks in general are noted for their windy
conditions, but the high ones are also famous
for snow, icing, and rime formation.

The steadiest winds are found in the
Trade Wind zone. Icing is not a problem
below the inversion layer, but hurricanes can
be troublesome in certain areas. A judicious
choice of sites can minimize the risk of these
natural hazards.

The main problem in wind power collection
is its scale. To meet present world energy
demands, some 10,000 collectors would be
required, each of 1000-megawatt capacity.
Clearly, this matter lies in the provinces of
bankers and engineers, but the power needed
is there if we can manage to capture it.

Another promising resource may be found
in the thermal contrasts involved in the
structure of the world oceans (see page 20).
Knowledge of this is not at all new and has a
distinguished history. It was in 1814 that von
Humboldt wrote that water is cold at great
depths in the tropics and explained this as a
consequence of sinking and outflow of surface
water conditioned in the polar regions. In
1881, D'Arsonval predicted that man would
someday "mine" the tropical oceans for heat
to power his civilization, rather than mine
the earth for fossil fuels. Georges Claude
made an attempt to operate a water vapor

8

turbine in this way in 1930, and the recent
technical and economic treatments of the
prospect have been given as late as the past
year by Clarence Zener. With this great
weight of prestige and scholarship behind
the scheme, ocean thermal power may well
emerge as one qualified solution of the
energy problem.

There is an enormous resource of solar
energy stored as heat in the surface layers
of the subtropical oceans, which, if released
in one second, would produce about 1028
watts. This warm water overlies much colder
water at depths which vary with latitude
from 1000 meters near 30°N and S to only
a little more than 100 meters near the
equator. The thermodynamic efficiency of
the temperature differences is small (about
3 percent), but the water volumes are truly
enormous. The problem is that of
"concentrating" the heat, as is done
naturally by the Gulf Stream or Kuroshio,
or proliferating the points of its extraction.
In the latter course, it has been estimated
that with several hundred large floating
or island-based "solar sea-power" generating
plants, it should be possible to provide the
world with some 1013 watts of power at
reasonable cost. At this level of heat
extraction, it is predicted that the ocean
surface layer would be cooled by about
1°C.

Here a cautionary remark might be
appropriate: some investigators have estimated
that a 2°C drop in world average temperature
would precipitate a glacial readvance. If true,
this would place an upper limit on ocean
thermal energy conversion at about 1013 watt
level.

Another resource involving the ocean-
atmosphere system is hydroelectric power, a
singularly clean and environmentally agreeable
way of serving our energy needs. Unfortunately,
hydroelectric power is already about 25
percent developed, and therefore even an
order of magnitude increase above its 1011
watt production level cannofbe realized.
But present installations work at or above sea

level. Is there something to be gained by
arranging for water to fall into sinks below
sea level in climates where they could be
emptied by evaporation?

The average height of land is about 840
meters above sea level. This may be regarded
as the average head available in successive
steps for conventional hydroelectric operations.
No single step is that large, to be sure, but
heads of as much as 100 meters exist. Natural
depressions below sea level can be almost as
deep, but what they lack in head, they may
make up in receiving area, and hence in total
discharge through turbines.

It has been suggested that the Red Sea
might be dammed at the Strait of Bab el
Mandeb and at the Suez end so that in the
course of a few decades, its level would be
lowered by evaporation about 100 meters
below that of the Indian Ocean and the
Mediterranean Sea. Hydroelectric power
plants at either, or both, ends of the Red Sea
could allow water to flow in at rates which
would compensate for evaporation and thus
maintain the head at a constant value. The
flow would amount to some 105 cubic
meters per second and produce some 1011
watts. This would double the world supply
of hydroelectric power, but at what risk?

The Red Sea is part of the East African
Rift system, which is seismically active.
Removing the weight of 100 meters of water
from this part of the crust would reduce the
pressure on it by 10 bars.* In that the
strength of the earth's crust is questionable
at 100 bars, and the region is already under
stress, it is conceivable that the reduction of
load might have seismic (not to mention
political) repercussions, which, to say the
least, are not very good for dams.

To look at this proposal in another way,
in the Mediterranean and Red seas the
evaporative losses are so great that there is
a powerful net flow of sea water into their
basins. Owing to the rotation of the earth
and their northern latitudes, the inflow is

* One bar equals 106 dynes/cm2, or very nearly the standard
atmospheric pressure.

stronger and deeper on the right-hand sides of
the Straits of Gibralter and Bab el Mandeb.
There is also an outflow of brines, strongest
on the opposite side and above sill depth,
which makes room for even more water to
join the inflow. These currents have
sufficient kinetic energy to produce some
109 watts without foreseeable risk. "Tide
mills" in channels arranged to engage the
incoming and outgoing flows could be used
to good effect in these straits until enough is
known about rock mechanics and large-scale
crustal behavior under changing loads to risk
building dams across them.

The beauty of hydroelectric power is that
it forms a pacific diversion of gravitational
and thermal energy that is returned to the
natural cycles of water and heat flow that go
on from day to day anyway. Another such
process is photosynthesis.

Green plants from tiny mosses to giant
trees thrive over two-thirds of the world's
land masses, and phytoplankton abound in
better than one-tenth of its oceans. All of
these use the energy of sunlight to fix carbon
in the form of protein, fats, and carbohydrates
which supply the bottom of the food chain.
The power involved in agricultural
photosynthesis is about 1013 watts, but the
human population utilizes only one percent
of it. We reap grains, fruits and berries,
tubers and roots, certain leaves, and
occasional saps. The rest is either
abandoned, burned, or plowed under to
restore the land. Yet the very things we
reject have produced, by anaerobic
decomposition, our fossil coal, oil, and gas
fuels, although very slowly and haphazardly.
A basic question is: can we assist this
natural process to produce sustained
"renewable" power?

In our system of life, we harvest, process,
package, deliver, consume, and eventually
excrete foodstuffs. The energy required to go
through this cycle in industrialized nations is
said to be ten times greater than the energy
derived from the food itself— about 1012
watts in all. The wastes of garbage, sewage,

packaging, and the energy of the disposal
systems are regarded as unproductive expenses.
Yet, we know, and have demonstrated, that
all the unharvested vegetable matter left in the
fields, the garbage, sewage, and rubbish of
feeding a population can be digested
anaerobically (or more precisely "anoxically")
to produce excellent fertilizer, and methane,
a very high quality fuel. In other words, we
could turn an open-ended problem into a
closed cycle of food regeneration, going from

Anaerobic digestion of phytoplankton could provide methane j

solar heat to human heat and amenities in a
natural way.

In the world today, about ten million
square kilometers of land are under
cultivation — about 6 percent of the earth's
land area and 2 percent of the whole globe.
This seems a small percentage of use, but whole
regions are not farmed because of permafrost,
jungle, desert conditions, mountain masses,
brackish or insufficient water. Elsewhere, the

10

human inhabitants can survive on natural
abundances. Be that as it may, the land under
cultivation produces vegetable matter having
a power equivalent of 1012 watts; of this, some
1011 watts is food, mostly grains.

Practical efficiencies generally being low,
it will be assumed that 10 percent is
reasonable for methane production by
anaerobic digestion. If 100 tons of vegetable
matter are grown on each square kilometer,
and perhaps one-tenth harvested for food,

ir fishing vessels.

Howard A. S chuck, NMFS

we are still left with about one billion tons of
material for anaerobic digestion. The
resulting weight of fertilizer would be about
90 percent of that of the raw charge, and the
methane produced at 10 percent efficiency
would be ten million tons, which is 10 percent
of the present world consumption of natural
gas. Upon combustion, this volume of gas
could produce 1017 watts of power. This may
seem to be getting something for nothing, but

it must be remembered that vegetation is
integrating solar energy over the whole growing
season, and this yield is computed as though
it were all expended in one second. Over a
year, the power flux from agriculture alone
would be near 1011 watts — quite enough to
keep mechanized farms fueled indefinitely.

These power estimates, based on vegetable
production on arable lands alone, are certainly
conservative and, moreover, ignore the sea.
Phytoplankton production in the oceans
amounts to some 1010 tons (dry weight) per
year, which, if harvested for power alone,
would produce 1014 watts -- ten times more
than that needed on a sustained basis to
supply civilization. We have assumed a
methane production efficiency of 10 percent
in these calculations. If the catching, or
culturing, efficiency is of the same order, the
power production falls to 1013 watts, which is
still sufficient to meet present world power
needs. This suggests that, initially at least,
plankton gathering and anaerobic digestion
might be a practical way to provide fuel for
ships at sea, especially fishing vessels, which
ply the plankton-rich waters where fish also
abound.

Returning attention to the land, it is
estimated that domestic animals produce about
two billion tons of manure per year. If this
were subjected to anaerobic digestion, it could
provide some 1012 watts of power for the
mechanical operations in meat growing,
processing, and distribution.

In cities, where a large fraction of the food
is consumed, metabolized, and excreted, there
is a power resource of some 1010 watts in
sewage and garbage. This resource would turn
a costly local disposal problem into an asset
and close the natural cycle of energy exchange
between the sun and earth, plants and animals,
without putting "new" energy into the system.
Since cities are to become more numerous as
the world population increases, and they take
a lot of power to be run comfortably, it would
be highly desirable in urban planning to design
a closed cycle of foods, power, and wastes.

In cold climates, if aerobic as well as

11

anaerobic digesters are operated within the
city limits, the heat of aerobic decomposition
could be utilized to hasten anaerobic
decomposition. The solid residues, which tend
to be rich in heavy metals, and thus unsuitable
as fertilizers, could be used as clean fill or
building materials. In these ways, even a city
could be made to function as a more "natural"
part of the earth.

In recent centuries, we have learned a
great deal about the earth but not much about
our relationship to it. It is becoming clear
that we now have to learn to live with the
earth and not just on it. Moreover, we are
wasteful. In our present practices, we reject
more than half of the energy produced from
fuels. For example, electric power plants
take in three times as much energy in fuel as
they put out in electric power, and much of
the machinery operated by electricity is less
than 50 percent efficient. Steam plants and
internal combustion engines are
thermodynamically inefficient because their
exhaust temperatures are high above absolute
zero. There is not much that can be done
about that except to reexamine how
effectively such machines are used. For
example, there could be almost no such
thing as "waste heat" if energy-consuming
processes were to be arranged in an orderly
cascade of decreasing input-output
temperatures.

The magnitude of our present energy

demand, when considered against the solar-
terrestrial heat balance, is truly small -- about
0.01 percent of the earth's budget. It seems
probable that we may learn to divert to our
uses as much as 0.1 percent of the energy
present in natural cycles. But if we do, it will
become mandatory to put things back in ways
that fit the natural regimen, to provide loops
in our uses of materials, foods and energy so
that the balances of the earth are preserved.
Energy management will not only present an
engineering challenge but also require some
fundamental readjustment of present patterns
in economic and political decision-making -
an adjustment of our ways of life to stay
within the capacities of the earth to sustain us.

Conservation of energy may be not so
much a matter of belt-tightening as a mature
reappraisal of values in its uses. In a world of
naturally governed abundances of energy,
supplies may not be harshly limited, but there
will be no room in our ways of life for
opportunism or profligacy. The words
"change" or "reassignment" must be
substituted for "growth," although economic
growth and increasing comfort in living
standards may well result from sensible
humanistic planning. Life in the era of
natural abundances will be a different but
probably satisfying adventure -- one that will
draw upon the same thoughtful and resilient
qualities of human nature that our parents under-
stood and that our children urge us to reassert.

William S. von Arx is a Senior Scientist in the Institution's
Department of Physical Oceanography. For further reading
in this field: Bates, Marston, The Forest and the Sea,
Random House, New York, I960; Brown, Harrison, The
Challenge of Man's Future, Viking Press, New York, 1954;
Brown, Lester JR., World Without Borders, Vintage (929),
New York, 1973; Cloud, Preston, ed., Resources and Man,
Pub. No. 1703, National Academy of Sciences, W, H.
Freeman and Co., San Francisco, 1969; Udall, Stewart,
The Quiet Crisis, Avon Books, New York, 1963.

12

Focusing the Surf

Ordinary wind waves are another possible
source of energy, though the process of
extraction poses some problems. When the
water depth is less than one-quarter wavelength,
the celerity of surface wave propagation is
proportional to the inverse square of the
wavelength. This effect causes wave crest
lines to turn toward the shoreline and, in the
end, to "fit" the coast. The energy density
per unit crest length is modified by the sense
of curvature.

Here, then, is an opportunity to produce
focused wave energy along coastlines abutting
broad continental shelves. An artificial shoal
some tens of wavelengths long, measured
parallel to the coast, and properly shaped
(it would resemble a crescentic shoal, convex
seaward), could focus the energy of swell on
a "horn" designed to accept the amplified
surge. With further amplification in this
receiver, a head of some tens of meters might
be achieved and the water stored for a
time to supply hydroelectric
turbogenerators and thus yield power for
transmission. Such a system would have to
be replicated again and again along a coast
to have a usefully large effective aperture. The
array would operate only as a supplementary
power source, however, being active just when
suitable storm systems pass over the adjacent
sea. This may amount to a week at a time
for each storm and thus keep the array in
practically continuous service during the
winter months in middle latitudes, but not
so in the milder seasons. It is difficult to
estimate the amount of power such a system
could provide, but a rough estimate places
the yield in the order of 10 megawatts* per
kilometer of coastline. The length of suitable
* One megawatt equals one million watts.

coastline in the world is about five thousand
kilometers. Owing to the alternation of
winter seasons between hemispheres and the
contemporaneous occurrence of mild
periods during the equinoxes, it would be
incorrect to multiply these two figures to
obtain a grand total.

Generally, wave erosion of coasts has so
redistributed loose materials on the bottom
and along the beaches that a minimum of
sediment transport is required to absorb the
incoming wave energy. An array of "lenses"
and "horns" to capture wave energy could
upset this balance disastrously.

It may be well to mention that another
kind of wave exists in the oceans, the internal
wave, which is not often thought of as a
power-producing resource. Internal waves
can exist in the presence of vertical gradients
of water density but are most easily detected
where they propagate on a sharp interface
between layers of water having distinctly
different temperatures. They are slow-moving
because of the "reduced gravity" effect of
buoyancy forces, but they are large in
amplitude — as much as 100 meters in some
instances. Like surface waves, they may be
reflected, refracted, develop interference
patterns, and, under some conditions,
"break." That these waves possess impressive
power is clearly indicated by the "diving
ballast and trim" records of submarines.
But again, their energy density per unit crest
length is low in comparison with that of the
whole wave system. This requires some sort
of arrangement to concentrate their energy.
Submarine canyons may be useful as "horn"
collectors, but it may be even better to look
for bottom topography that could produce
focusing effects.

W. S. von A.

13

Distance in Kilometers

..d*-

D

•*

*

•'••MttWjjn,...

A

B

.

4**

D

Provinces of Promise

K O PWWY)

-t\.V^/. _L(r rIC'f y

Present offshore production of oil and gas is
approaching 20 percent of total world
production, and there is every prospect that
both the quantity and the percentage will
increase considerably during the next decade.
Limits to the rate of increase appear to be due
to high dollar costs of drilling (partly offset by
lower costs of marine geophysical exploration),
to sociopolitical fears of some nations, but
probably not to possible environmental costs.

About 97 percent of the offshore
production is by oil companies (from industrial
nations) which have obtained concessions or
leases from host governments. Government
bureaus in centrally planned economies
handle most of the remainder. Their output
is small, probably because of lesser know-how
and greater fear of unrewarded risks. (In this
context, national companies such as British
Petroleum and Compagnie Francais du Petrol
are considered non-government, as the
government control is limited to ownership
of the majority of the stock and not to
geological operations.)

The work of universities and oceanographic
institutions involving offshore petroleum is,
of course, different from that of the oil
companies. Academic and research scientists
study the sources and accumulation of

Pagoda structures on abyssal plains and lower continental
rises off western Africa. White triangles (sections of cones)
are believed to have been cemented by methane hydrates,
or clathrates. Seismic reflection shows basement-sediment
interface at roughly 4700 meters (A), 4600 meters (B) and
(C), and 3850 meters (D).

petroleum, investigate the causes and
distribution of petroleum provinces, and
attempt to learn the origin of continents and
ocean basins and the composition and history
of continental margins. (Oil companies
undertake such studies and investigations, but
because the findings of oil-company geologists
in this area are not likely to be approved by
management for open publication, their
efforts are not widely recognized.) During the
course of their studies, oceanographers may
discover large sedimentary basins or other
potential petroleum provinces. But if oil is
to be found, it is the oil companies that must
make the closely spaced and expensive
geophysical traverses in order to obtain the
necessary ''drill-here" information.

Present production of oil and gas from the
continental shelves of the world is fairly
localized (Figure 1). At least 95 percent of it
represents oceanward extensions of oil
provinces previously known and exploited on
the adjacent land (see Oceauiis, Spring 1973).
There is little doubt that most of the
undiscovered oil and gas on the shelves lies in
provinces not closely related to those on land.
The best known of these are off Australia,
where a decade ago the government recognized
the futility of expecting large production on
land and offered tax concessions for offshore
exploration and exploitation. Some of the
North Sea structures that produce Tertiary
oil also are unrelated to those of the land.

Similar sites likely to be proven productive

15

PRODUCTION

OF CRUDE OIL

1972

in the near future are on the Atlantic
continental shelf of North America (Figure 2),
the Atlantic shelves of southwestern and
northwestern Africa (Figure 3), and the Pacific
shelf off eastern Asia (Figure 4). All three
areas have been investigated by oceanographers
(and by some companies), who have found
thick prisms of fine-grained as well as coarse-
grained sediment underlying the continental
shelves. The linearity of the American and
African deposits appears to be typical of
continental margins that border the Atlantic
Ocean, where crustal plates include both the
continents and the adjacent ocean floor. In
contrast, the continental shelf off eastern
Asia is an area ot convergence between
continental and oceanic crustal plates, with
consequent active block faulting and folding
of the continental margin.

Many continental margins remain
unexplored because of inhospitality of
climate (drifting ice in high latitudes) or of
governments. The latter constitutes a complex
problem. Some governments are moved by
ideological considerations to keep their
shelves to themselves. Others fear that the
ten or so nations possessing the advanced
geophysical tools and methods necessary for
offshore exploration may use this knowledge
as an entering wedge of colonialistic
exploitation. This in spite of the fact that the
most advanced among developing nations

FIGURE 1. Distribution of crude oil production on the
continental shelves of the world. Numbers denote the
millions of tons of oil produced during 1972 from fields on
different segments of the shelves. Areas believed to have
the greatest potential for oilandgas are shown in solid black;
many of these potential petroleum provinces are still unexplored
because of hostile climates or fearful adjacent nations.

appear to be those which have welcomed oil
company interest. Whatever the motivation,
governmental hostility to offshore exploration
has resulted in severe limitation of knowledge
concerning the continental shelves that border
many nations -- including those off India,
mainland China, the Soviet Union and its
satellite nations. The result is that roughly
three quarters of the published studies of
geophysical traverses and bottom samples of
the world's shelves deal with areas off the
United States and Europe - all open industrial
nations. In short, shelf areas of high petroleum
potential (inferred from general geological
knowledge) are far larger than those where
petroleum production has begun; yet for one
reason or another, most of these areas remain
unexplored by modern geological methods.
Production of oil and gas from parts of
the continental margin* deeper than the
continental shelves has been impeded mainly
through lack of reliable methods for ocean-
floor well completions. Most likely these

* The continental margin comprises the continental shelf,
the continental slope (descending from the edge of the
shelf), and the continental rise (a gentler declivity
extending out to the abyssal plains).

16

FIGURE 2. Total thickness of sediments (in kilometers)
above basement along the Atlantic continental margin of
North America, based on geophysical studies at Woods Hole
Oceanographic Institution, Lamont-Doherty Geological
Observatory, and other organizations during the past three
decades. Except off eastern Canada and in the Gulf of
Mexico, this province remains undrilled and untested,
owing to fears of oil spills during drilling and production.

technological problems will be solved during
the coming decade, and oil and gas can then
be produced economically from far greater
water depths than at present. One such deep-
water environment is represented by small
marginal basins, nearly all of which are
located near Pacific Ocean coasts. Examples
are the many basins off southern California,
several of which (the Los Angeles and
Ventura basins) have been filled to overflowing
with sediments similar to those that have
produced about 15 percent of the United
States' oil and gas. The most promising are
adjacent to the shore and thus have received
thick layers of land-derived sands that serve as
oil reservoir beds. Santa Barbara is the best
known. Oil production from its shallower
parts has been curtailed temporarily for
environmental reasons. Basins farther from
shore are unlikely to be very productive
because they lack reservoir sands.

Quite a different kind of marginal feature
is the China Basin on the opposite side of the
Pacific Ocean (Figure 4). Prominent fold ridges
cross the floor of this basin, and coral reefs on
the ridges reach close enough to the surface

FIGURE 3. Total thickness of sediments (in kilometers)
above basement along the Atlantic continental margin of
Africa, based mainly on studies by Woods Hole
Oceanographic Institution during 1972-73 as part of
the International Decade of Ocean Exploration. Black
areas denote belts of salt diapirs. Most of the prospective
areas are in water depths beyond the capacity of present
drilling and production technology.

FIGURE 4. Distribution of thick sediments (in kilometers)
within basins off eastern Asia, based on a series of studies
by the U.S. Naval Oceanographic Office and Woods Hole
Oceanographic Institution between 1968 and 1971.
Double hatching denotes filled basins beneath the
continental shelf; single hatching, partly filled basins
beneath deep water. Single hatching in the sinuous patterns
in the China Basin (west of the Philippine Islands just south
of the middle of the figure) denotes fold ridges that rise
above the otherwise flat basin floor. Production as yet is
almost entirely restricted to the southernmost part, owing
to conflicting claims to the sea floor by adjacent nations.

17

to serve as natural drilling platforms. Whether
or not oil and gas are present is unknown.
However, the expectations of nearby nations
are such that confrontations between South
Vietnam, Philippines, and mainland China
occurred earlier this year, resulting in the
sinking of several ships.

Another deep-water province of high
petroleum potential is the continental rise,
perhaps the major sedimentary depositional
feature of Earth. It is best developed in
the Atlantic and Indian oceans, where its
growth is unimpeded by the thrusting of the
ocean floor beneath the continents, such as
that which occurs around the Pacific Ocean
(Figure 5). Production of oil and gas from
this feature is likely to be extremely difficult,
owing to great depth of water and distance
from shore, but these same factors may
immunize the offshore fields from the
various forms of nationalization that are
plaguing petroleum development on land in
many nations of Africa and South America.

Deep-water salt diapirs offer high
potential as traps for oil and gas. These
structures are common on both sides of the
Atlantic Ocean, having begun as thick beds
of salt and gypsum deposited as evaporites
160 to 200 million years ago within long
narrow arms of the ocean formed when North
America and South America began to move
away from Africa and Europe. Later
deposition atop the evaporites of denser
sediments from the land areas caused masses
of salt to rise upward through the sediments
in the form of salt domes or diapirs. Best
known are belts of diapirs beneath the land
and the continental shelf in the Gulf of
Mexico; these have produced about 15 per
cent of the United States' oil and gas. They
continue farther oceanward beneath the
continental slope and rise, and even occur
beneath the abyssal plains. Similar belts have
been found and mapped off western Africa;
others are known to exist off eastern Canada
and eastern Brazil, in the Mediterranean Sea,
and beneath the continental shelf of the
North Sea. Production from the deep-water

diapirs is likely to have the same sort of
difficulties as production from the
continental rises, with which they are
closely associated.

Lastly, rather peculiar structures were
observed on the otherwise flat and smooth
abyssal plains and lower continental rises
during geophysical studies conducted by
Woods Hole Oceanographic Institution
scientists off western Africa during 1972 and
1973. The term "pagoda structures" has been
applied to them because of their shape -- like
the roofs of pagodas (see page 14). They were
observed along nearly halt the total length of
geophysical traverses of sediment-covered
ocean floor. Their seemingly greater
abundance off Africa than in other parts of
the world is attributed to the use of particularly
good 3.5 kilohertz seismic recording equipment
during the African cruises. While the origin of
the features is by no means established, they
may represent partial cementation of the
bottom sediments by gas hydrates or clathrates,
a form of gas (probably methane) that exists
as a solid under the high pressure and low
temperature of the depths. If more detailed
investigations show that the pagoda structures
really do contain considerable methane, they
may become useful reserves of gas for the
energy -hungry nations of the world.

Annual production of oil and gas from
most land areas may have passed its peak, but
production from the ocean floor still is
expanding and probably will surpass that
from the land within a decade. The dimensions
of peak production from the ocean and the
time of its achievement will depend upon a
number of factors:

1. The rate at which exploration of new
ocean areas can be completed (largely political
in nature).

2. Development of means to overcome
ice damage to installations on the shelves at
high latitudes (technological in nature).

3. Continued improvement in preventing
oil spills, particularly those associated with
shipboard transport of oil (both legal and

18

technological).

4. Development of methods for well
completions and production in water depths
beyond the shelf edge (technological).

5. The rate at which substitute sources
of energy, particularly oil from shale and
coal, can become practical (chiefly a matter
of economics and technology).

These scientific, technological, political,
legal, sociological, and economic limitations
are likely to be steadily overcome in ways that
may not now be visualized. Barring large
increases in consumption, fossil oil and gas are
thus likely to continue as major sources of fuel
for more than one hundred years.

FIGURE 5 . Distribution of continental rises throughout
the world ocean, compiled from topographic charts guided
by geophysical traverses from many sources. Chevrons
show positions of crustal plate convergences where the
ocean floor is thrust beneath continental margins and where
continental rises cannot accumulate.

K. O. Emery is a Senior Scientist in the Institution's
Department of Geology and Geophysics.

19

William E. Heromnms

I

I

Windpower can be used on small as well as large scale.
Device above, made from a bicycle wheel, powers radio at
New Alchemy farm in Falmouth, Mass. (Vicky Briscoe)

Those who have lived with the sea are keenly
aware of a vast energy of motion and of the
marked differences in heat content at different
locations in the water column and in the
overlying atmosphere. It is at this ancient
interface, with its 800-to-l difference in
weight density, that a large portion of each
day's new ration of solar radiation is
received, and from which much of the
degraded long-wave radiation begins its return
to outer space. Along with the kinetic energy
in air and water particles, we also find natural
mechanisms which in certain places can create
large increases in the potential energy of the
water mass; energy fluctuations which can be
trapped in tidal power extraction systems;
and the potential energy stored in wind waves.

For many centuries and with varying
degrees of success, inventive man has used
motions of wind and sea to propel his
machines. Today, there is increasingly strong
evidence that the wealthiest and most
technically sophisticated of current societies
should once again direct its sights toward
these tradiational energy sources. Why?
First, because they can do useful work with
very little, if any, resultant pollution; second,
because their potential is vast compared to
the total result of all of mankind's frenzied
and expensive efforts with combustion and
fission; third, because they are renewable
resources whose use would be effected through
processes which would not limit the
improvement in material well-being of other
nations or of future generations.

The major input which sustains these
processes is solar energy, received at the
surface of the earth's atmosphere at a rate of
about 5000 quintillion British thermal units of
energy per year (one quintillion, or one Q,
equals 1018). The secondary inputs are the
work done on water and air by the
gravitational fields of sun and moon and by
the spinning of the earth. Each year about
65 Q of these inputs finally manifests itself
as kinetic energy in moving particles of air -
the winds. The annual energy inputs into
tidal flows and oceanic currents are probably

two orders of magnitude smaller than 65 Q,
whereas that taking the form of heat stored
in the surface layers of the ocean is one order
of magnitude larger. If we wish to order the
processes by their energy potential, we would
thus place the heat stored in the oceans first,
the kinetic energy stored in the winds second,
the potential and kinetic energy in wind
waves third, and the potential and kinetic
energy in tidal flows and in oceanic currents
fourth. It remains to discuss the feasibility,
technical and economic, of extracting any of
this energy for our direct use.

Winds, even those blowing over the seas,
are regional phenomena. Every man of the
sea knows of the nor'easter, the roaring
forties, the doldrums, the horse latitudes.
There are at least 57 winds recognized by
name. Each wind has its own characteristics:
there are the rather moderate but very steady
trades, and there are the westerlies, sometimes
blustering, sometimes flat calm. They appear
random and capricious, yet when one studies
the wind from the viewpoint of energy
content -- taking measurements at fixed
locations and heights for periods of a year -
one finds the wind to be a remarkably
reproducible phenomenon.

When winds at specific sites are examined
for energy content, it is soon apparent that
the most energetic of them are over the oceans.
Winds leaving a land mass, moving out over
open water, show a marked ability to intensify
in velocity after passing over a relatively short
fetch of open water. The large-scale
atmospheric processes which produce such
features as the generally low-pressure area over
the northern Atlantic and the similar "pressure-
sink" over the northern Pacific occur in regions
rather unfriendly to man. But the winds they
create manifest themselves on or close to
many shores accessible as work sites.

The rate at which the atmospheric processes
create and sustain the winds does seem to
vary regionally. Whereas the horse latitudes*
are large earth-girdling zones in which a

* The area roughly between 30° N and S, characterized by
calm and light variable winds.

21

Winds over Mt. Washington, New Hampshire, and their
seaward extension are testing ground for large-scale
windpower usage. (Jonathan Lingel, Mt. Washington
Observatory)

steady, moderate conversion of solar energy
to kinetic energy seems to persist, the belt of
land comprising the northern United States
and southern Canada, from the Rockies
eastward appears to be one in which a rapid
but seasonally variational rate of kinetic
energy conversion occurs. Winds off this
belt reach very high velocities over the top
of Mount Washington and across the French
islands to the south of Newfoundland. By
the time they have reached the fishing banks,
they are usually quite fresh, except during
August and September, when warming of the
sea surface in that area is near its peak.

In 1970, the winds over New England
and their seaward extension, the offshore
westerlies, became the testing ground for a
major feasibility study of windpower as a
large-scale source of energy. The idea that
windpower could -- indeed should -- provide
a major portion of the electricity demanded
by a modern industrial society was already
well documented. Many competent men and
serious-minded organizations in a number of
different countries had worked on the
technology of windpower conversion for
several decades — had shown clearly that the
resource was huge and that utilization was
technically quite practical. But they had
been unable to demonstrate that wind-generated
electricity could compete economically with
electricity generated by heat engines burning
$2.50-per-ton coal or ten-cent-per-gallon
diesel oil or three-cent-per-gallon residual -
costs that pertained some fifteen years ago
when these fuels were thought to be nearly
inexhaustible. The promise of even less
expensive electricity from large numbers of
nuclear plants caused the abandonment of
all windpower programs.

We at the University of Massachusetts
reopened the issue primarily because we
thought that this country was headed toward
a more realistic concept of capitalistic

Jan Hahn

economics in which the externalities associated
with energy-industry pollution would be costed
so that the energy consumer would pay more
of the total cost of that energy. Given that
eventuality, we argued, pollution-free, wind-
generated electricity might be shown to be
economically competitive. It was also decided
that the economics of earlier windpower
systems had been unfavorable because no one
had attempted to sell electricity on demand,
thus taking advantage of the entire breadth
of the rate structure. Earlier schemes had
attempted to compete with the differential
cost of fuel, saving fuel only when the wind
blew.

We knew of the relative freshness of the
offshore winds; excellent long-term velocity
data taken at three Texas towers corroborated
the intensification-over-water hypothesis.
So it was decided that a concept for a large
windpower electricity generating system,
offshore in the westerlies, capable of selling
electricity on demand, would be set down for
analysis. The resulting Offshore Windpower
System (OWPS) was shown to be large
enough to provide most of the New England
electricity market projected for 1990. Later
studies showed that the system could easily
be twice as large, selling up to 360 billion

kilowatt-hours of electricity per year,
transmitted and delivered throughout the
six-state New England region. This first
concept was an all-hydrogen system; all
electricity was to be used to create hydrogen
gas, a storable as well as a low-cost energy
transmission agent (see page 28).

The cost of delivered product from that
first OWPS — average revenue per kilowatt-
hour of electricity delivered on demand -
was not competitive with the 28.3 mills per
kilowatt-hour average required revenue
prevailing in 1972. Those who had studied
the overall problem of generation and
transmission of electricity in New England
in 1968-1970 were convinced that the
average required revenue per kilowatt-hour
would decrease steadily beyond 1968 as it
had actually done prior to 1968. However,
they were quite wrong in their estimate of
that situation. Subsequent studies of the
360 billion kilowatt-hours per year and of a
smaller OWPS using both electricity-in-cable
and pipeline hydrogen gas energy
transmission, have shown that the 1972
OWPS average required revenue per
kilowatt-hour of about 31 mills could be

m

"

dropped to 26 to 28 mills. At the same
time, the average required revenue for
conventional power in New England turned
upward; it passed 31 mills in 1972 and is
now well over 36 mills, when averaged over
the entire region. (It must be clearly
understood that the competitive price for
electricity generated by windpower systems
depends upon large-scale manufacture of all
components of the system — something that
would be entirely feasible and proper.)

Where, other than on the front porch of
New England, could the winds over the
oceans provide large amounts of electricity
or synthetic fuel (hydrogen, methanol) or
fertilizer (ammonia)? There are many
oceanic sites sufficiently near shore, and in
shallow enough water, to be connected to
the consuming market by pipeline or cable
umbilicals. A partial list: the shelf off our
middle-Atlantic states; the shelf off Nova
Scotia; the shelf to the westward of Ireland;
the Irish Sea; the eastward edges of the North
Sea; the near-shore portion of the Baltic off
Sweden and Finland; the shelf adjacent to
the entire Aleutian Archipelago; the narrow
shelf west of and the broader shelf east of
South Africa; the shelf south of Australia;
and the shelf adjacent to the Kurils. Any of
the islands in the stronger trade regimes and
those, like the Falklands and the Prince
Edwards, in the roaring forties are excellent
sites.

Extraction of energy from the winds
could proceed afloat on the high seas in
the most favorable wind regimes, the wind
generator platform doubling as a self-propelled
tank ship equipped to generate and liquify
electrolytically produced hydrogen. A new
concept along this line, which includes wind
propulsion, is under investigation by the
author. Further, great amounts of energy
could be extracted over a region like the
Great Bahama Bank from a forest of wind
generators, installed in a way that would
accomplish negligible harm to the bank or the
biota living thereon. What a magnificent
export product for that small nation!

Wind-generated electricity at many sites
throughout the West Indies could provide
ecologically pure energy to expanded resort
communities and, in some places, could lead
to clean industries such as the electrolytic
refining of aluminum and the electric
remelting of high-alloy steel products. In
the oceanic winds, we have a huge energy
resource that modern technology can harness
to serve our needs on demand. It could be
put to use in the very near term, economically,
in an aesthetically satisfactory way, and with
no pollution of any kind.

Important as winds are, however, it will
be remembered that first priority among the
sources of potential energy listed earlier went
to the collection of energy in the surface layer
of the tropical seas. Those who know their
geography are aware that the ocean accounts
for 90 percent of the earth's surface between
the Tropic of Cancer and the Tropic of
Capricorn. That is where the most intense
solar radiation reaches earth. The heat
capacity of water is greater than that of any
other liquid and, indeed, is one of those
properties which distinguishes water as the
most remarkable of our earthly compounds.
But the sun cannot penetrate very deeply
into the seas. That fact plus the many
phenomena which, combined, create the
gross circulation of the oceans, produce the
cold water which underlies even the hottest
of the tropical seas. Whereas an astronomically
huge reservoir of hot surface water by itself
can do little for man from an energy point of
view, the combination of a vast heat reservoir
plus a vast cold reservoir only a short distance
away can do much.

Investigations into the technical and
economic feasibility of tapping the energy
potential of oceanic thermal differences are
being supported here at the University of
Massachusetts and at Carnegie Mellon
University by the RANN (Research Applied
to National Needs) Directorate of the
National Science Foundation. The work at
Massachusetts, to date, has been aimed at one
specific application of the process — a system

24

Proposed 400-megawatt ocean thermal differences power plant, shown
here, would operate like a huge refrigerator in reverse. Warm surface
water gives up heat through tubes of evaporators (A) changing
refrigerant working fluid into vapor under pressure. Cold bottom
water is brought up through inlet tube (F) and hinge joint (E) to chill
condenser tubes under turbines located in pressure hulls (B). Low-
pressure region is thus created, toward which vapor can expand,
operating turbines in process. Warmed bottom water is collected in
circulating water overboard trunk (C) and redirected toward bottom.
Access is through towers (D) extending above surface. Plant will have
16 power packages, each yielding 25 megawatts of electricity.
Structure is 675 feet long, 495 feet wide, 390 feet high. Inlet tube
is 1060 feet long; lower end is 66 feet above seabed.

which could deliver large amounts of
electricity or hydrogen fuel by cable and
pipeline to the lower forty-eight states.
Because of this specific approach, first
suggested by the Andersons* in 1964, we
have arrived at some conclusions which reflect
the application as well as the process. We
have concluded that large numbers of thermal
differences power plants could operate in a
rather large area, 15 miles east-to-west by
550 miles south-to-north, along the western
portion of the Gulf Stream. They could
produce electricity or hydrogen gas at a cost
which would permit either product to be
transmitted to almost any point in the United
States and sold at a competitive price.

The Ocean Thermal Differences Power
Plant is conceived here as the inverse of the
mechanical refrigeration plant on a rather
large scale. A closed Rankine cycle using a
refrigerant (propane, ammonia, a Freon®)t
as a working fluid is made to operate across
a temperature difference as small as 17°

* J. H. Anderson and his son, J. H. Anderson, Jr., are
founders of Sea Solar Power, Inc. of York, Pennsylvania.

t ® Freon is the registered trademark of Du Pont.

Celsius, producing useful work at an overall
efficiency on the order of 1.5 percent. The
warm surface water gives up heat through
the walls of the evaporator tubes, changing
the working fluid into a vapor under
pressure. The cold bottom water is brought
up and used to chill the condenser tubes
under the turbine, thus creating a region of
low pressure toward which the vapor can
expand and do useful work in the process.
Power packages comprising evaporator
(boiler), turbine, condenser, pumps, and
piping have been designed. They are to be
sized to match a turbine having a shaft work
capacity of about 37 megawatts. The power
plant itself is a semi-submersible structure
containing multiple units of these
37-megawatt gross power packages. Each
37-megawatt package will yield about
25 megawatt-electrical net power, so that
the power plants are sized as multiples of
25 megawatts of electricity (MWe). Our
first experimental plant will include 16 of
those packages and is thus a 400 MWe power
plant — no small unit by today's standards.
We will place it at "Site One," located 25
kilometers due east of the Collier Building at

25

the University of Miami in about 360 meters
of water. At Site One we have a 17°C
temperature difference for about 30 days of
the year, and a larger difference other times.

Our investigation began with the hope
that the total installed cost per kilowatt (net)
of the plant, including 15 miles of energy
umbilical, would be $400. Our current
calculations, based on 1973 prices, suggest
that S650 per kilowatt may be closer to the
mark for a system improved by installation
of pressure-proof metallic heat exchangers.
One of these power plants, brought on line in
1980 at a cost per kilowatt of less than
$1100, will win the Florida market from any
forseeable nuclear or fossil fuel competitor.
Each $100 in capital cost below $1100 means
another 200 miles of transmission distance
through which this system's product could
win that competition.

Thus, ocean thermal differences plants
installed at $650 per kilowatt off Miami
should be able to win the Chicago market
away from the nuclear by 1980. The liquid
metal fast breeder reactor doesn't have the
slightest chance of competing economically
against this system. No breakthroughs or
new inventions are required here, only the
careful application of straightforward
technology. With the proper national or
private commitment, an operating
demonstration plant could be on site within
six to eight years. The mooring, anchor,
cold-water inlet pipe, and the detailed design
of the evaporators and condensers are the
controlling items, all of which could be
brought along, step by step, in a well-paced
development program lasting six years and
resulting in the operating demonstration
plant.

ARCTIC
OCEAN

ARCTIC OCEAN

\ ANTARCTIC OCEAN

^f:V:-Ky.W-\:yff:W:f.Vf^::-W.y-' '• ' ' SSSSx&SxSS:

26

In the winds over the oceans, and in the
thermal differences which the sun creates,
we have bountiful resources- of pollution-free
energy. It is left for others in this issue to
describe the energy in the tides and in the
currents. These processes are the way of
the future. When combined with other solar
energy processes, they constitute the only
energy regime which can sustain any real
growth without making our globe uninhabitable.
They are the processes toward which the
developing nations, all rich in solar energy,
should be helped to move. And the leader
in that assistance should be the nation
which has the greatest need itself to get on
with solar energy -- the United States.
Instead of a Project Independence based on
pique, sacrifice of our first minimal actions
toward control of pollution, and a false

concept of a viable future energy economy,
we should be embarking on Project Solar
Dependence, a deliberate plan of action that
would place us in harmony with the biosphere,
using nothing other than renewable energy
resources. Intelligent use of the oceans and
their overlying atmosphere will permit us to
get started on the project right now.

William E. Heronemus is Professor of Civil Engineering at
the University of Massachusetts.

WIND DIRECTION

Left: Analysis of ocean windpower potential
made in 19 39 by Sverre Peterssen. Measurements
are based on emplacement of Smith-Putnam
1250-kilowatt machines with propeller axes
150 feet above surface. Numbers are estimates
of probable annual productivity per kilowatt
of installed generator size. Thus, on the 4000
contour, each kilowatt of generator would
yield 4000 kilowatt-hours during the 8700
hours of the year. Farther out to sea, east of
Labrador, the yield would be greater than
5000 kilowatt-hours per year, "a fantastic
yield," says the author.

Right: Floating four-megawatt wind station
made from low cut-in wind generators.

BUOYANCY SPHERE

BALLAST BOX

ANCHOR

27

Hydro

-A- r^ <

To Burn

Howard P Harrenstien

The conveniences of fossil fuels are certainly
well known and, in fact, have long been
taken for granted. As the world finds its
reserves of these fuels being depleted, and as
more intensive efforts are undertaken to
locate additional supplies, many of these
conveniences will be reviewed and
questioned. For example, as supplies
dwindle, increasing pressures for large price
increases will in part erode the economic
advantages which fossil fuels have enjoyed
since their discovery. Years ago, increases in
price and decreases in availability of natural
rubber provided the motivation to invent and
develop the superior synthetic rubber product.
Today these same pressures are causing
scientists and engineers to look for alternative,
and possibly superior, synthetic fuels.

A synthetic fuel needs a primary energy
source for its production. If this source is
petroleum, little is to be gained as far as
petroleum conservation is concerned. If the
primary energy source is something else,
then perhaps a major impact on the world's
petroleum conservation efforts may be
realized: petroleum may be preserved for use
in petrochemicals and other higher-priority
items.

When synthetic fuels are contemplated, we
might just as well look for the most desirable,
since present technology could be aimed in
any one of a number of directions. What is
needed is a fuel which can be easily
manufactured from extensive resources, such

as coal or nuclear materials, or from solar,
oceanic, geothermal, and other renewable
sources of energy; one which can be easily
transported and stored (a liquid or gas
would be satisfactory); and one which would
be clean-burning while yielding a maximum
heat output from a minimum of weight
and/or volume, if, in addition, it were safe
to handle and non-toxic, the fuel would
appear to be ideal.

No such fuel exists, but hydrogen comes
close. It can be bottled, stored, piped,
pumped, burned, exploded, liquified, and
even used to take man to the moon. It is the
cleanest-burning fuel, giving off only water
vapor and heat when burned in oxygen.
When burned in air, it still primarily exhausts
water vapor and heat and , if the fire is hot
enough, small amounts of oxides of nitrogen.

Although free hydrogen is not as
plentiful in the earth's atmosphere as it is in
the universe, there is plenty of it stored in
chemical compound with oxygen in the form
of water, in the earth's oceans, lakes, streams,
and aquifers. In this resource, it is
stoichiometrically balanced with oxygen at a
rate of two atoms of hydrogen for each atom
of oxygen -- the ratio required for the
complete combustion of hydrogen.

Hydrogen can be transported, either by
pipeline or in cryogenic tankers. It can be
safely substituted for petroleum and coal in
almost all existing industrial processes which
require a reducing agent, such as steel

28

manufacturing and other metallurgical
operations. And it can be easily converted to
other fuel forms, such as methanol, ammonia,
and hydrazine.

Internal combustion engines run
efficiently on this fuel, as do gas turbines.
Fuel-cells, which are flameless, produce
electricity from hydrogen at high efficiencies.
Where storage of hydrogen, either
cryogenically or under pressure, is not
convenient, it may be stored as a metal
hydride. This material releases its hydrogen
when heated.

The universality of this lightest of known
elements is intriguing. Two atoms of hydrogen
make a molecule, H2 , which does not vary in
quality with respect to origin or location. By
that I mean that a molecule of hydrogen made
by electrolysis of seawater using electricity
generated by the Florida Current looks just
like a molecule of hydrogen made from coal
gasification in Montana, or a molecule made
from wind generators, through electrolysis,
in Massachusetts. Hydrogen manufactured
by volcanic or solar means in Japan or Hawaii
may be mixed with any of these other
molecules, and the composite will be identical.
Thus the hydrogen economy offers the world
a truly universal fuel system with complete
compatibility of end product, regardless of
the source. This universality would
ultimately offer excellent economics in the
interchangeability and transmissibility
of technology between the industrialized
nations of the world. The cost of initial
conversion is obviously high, but the benefits
are far reaching.

Many of the proposed new sources of
primary energy, such as wind energy, ocean
waves, ocean currents, ocean thermal
differences, solar energy, and geothermal
energy all suffer location disadvantages. They
generally are not present in the right
magnitude at the right place and at the right
time for them to be directly converted to
electricity and placed on line at that point.
Even if they could be so converted, line
losses imposed by transmission distances

would place a heavy tax on efficiency.

Enter hydrogen. Ocean thermal electric
plants, which are located in the tropical seas,
could generate it on location and store it at
hydrostatic pressure on the sea bottom. Ocean
tankers could collect the product at the
proper time and deliver it to the world
marketplace at great efficiencies in energy
conservation. Ocean current generators
could also produce the gas in much the same
way at those locations where the currents are
optimum. The same delivery system could be
employed. Floating stable platforms, using
pho.tovoltaics and electrolysis to convert solar
energy to hydrogen in mid-ocean, could also
be placed "on-line" as far as the hydrogen
system described is concerned. As a matter
of fact, even bottom-of-the-sea geothermal
energy plants could be developed to produce
hydrogen for these purposes.

In sum, the hydrogen economy may hold
the key to the integration of many new
sources of energy into a common,
environmentally acceptable synthetic fuel -
one which will allow us to conserve our
precious fossil fuel reserves and, at the same
time, develop a higher-level technology to
advance the quality of life in this country and
the world.

Howard Harrenstien is Dean of the School of Engineering
and Environmental Design at the University of Miami. He
recently chaired The Hydrogen Economy Miami Energy
(THEME) Conference, sponsored by the National Science
Foundation and the Advanced Research Projects Agency.
Proceedings of the conference are available through the
University of Miami.

29

byELLawton

Tidal energy is abstracted from seawater at
locations where estuaries or embayments and
control structures permit utilization of the
head.* Tidal-power plants operate on the
continuously varying differences in level
between the water in the basin constituted by
the controlled estuary or embayment, on
the landward side, and the water in the sea.
The basin must be filled from the sea or
emptied to the sea as required by the
operating regime of the power plant, so that
production can be matched with the demand
on the power network to which the plant is
connected.

It is technically feasible today to exploit
much of the conservatively estimated 13,000
megawatts of the world's tidal-energy
resources. Tidal energy, converted to electric
energy, is free from any deleterious effect on
the air, water, or land environment. Its
exploitation rests on its economic
competitiveness when all internal and
external costs of competing energy resources
are properly assessed. The uncertain
availabilities and escalating costs of fossil
fuels and, perhaps to a somewhat lesser
extent, of fissionable fuels are inexorably
advancing the time when tidal power will
come into its own.

Records indicate that by the eleventh
century tide mills were in use along the
Atlantic coast of Europe, notably in Great
Britain, France, and Spain. Even as late as
the mid-nineteenth century, tidal energy was
used widely in coastal areas where the tides
attained a sufficient range. Twenty-foot

* Difference in elevation between two points in a body of
seawater or other fluid.

**•

. w

.•:vr • i

World's only large, modern tidal-power development lies ac

waterwheels installed in 1580 under the
arches of London Bridge were providing part
of the city's water supply some two and a
half centuries later. A tidal-power installation
for pumping sewage was still in use in
Hamburg in 1880. Other installations have
been reported throughout this era in Russia,
North America, and Italy. Some of the old
structures were of impressive size. A tide
mill in Rhode Island, built in the eighteenth
century, used 20-ton wheels, 11 feet in
diameter and 26 feet in width.

Early tide mills produced small amounts
of mechanical energy — about 30 to 100

30

mce River estuary in France.

kilowatts -- generally used at the site. This
was enough to satisfy demand before the
advent of the electric motor and long-distance
power transmission. The disappearance of
tidal-power generation towards the end of the
nineteenth century has been attributed to
power economics. However, new concepts
of construction and marked advances in
large, better-adapted generating units have
reawakened interest in the resource as a
possible competitor with other forms of
energy.

Engineers have examined a large number
of locations potentially favorable to tidal-power

Courtesy of the French Embassy

development. These include sites in the
estuaries and embayments of northeastern
North America, the English Channel and
North Sea coasts, the Irish Sea, Barents and
White seas, the Gulf of Alaska, the Okhotsk
Sea, and the coasts of Korea, China, the Gulf
of Bengal, Pakistan, Western Australia, and
Southern Argentina.

The USSR has slowly and methodically
pursued work leading to the ultimate
development of tidal-power generation, the
principal proponent being L. B. Bernshtein.
A small tidal-power plant was recently
placed in service in Kislaya Bay, a deep basin

31

Passamaquoddy tidal-power project has long history. Here,
visitors from Washington look over early designs. (U. S.
Army Corps of Engineers)

with an area of one square kilometer,
connected with the sea by a narrow estuary
about 100 feet in width. The tidal range
is something under 11 feet. Conceived as an
experimental undertaking involving minimal
expenditures, the basic concept entails the
use of prefabricated caissons built under factory
conditions at a suitable location, floated,
towed to the site, and there sunk into
prepared foundations.

In addition, the USSR is reported to be
investigating a first-stage, 4000-megawatt
development in the Mezen sector of the White
Sea, with others to follow. They have in mind
the possible development of a 320,000-
kilowatt tidal-power plant at Lumbovskaya,
where a bay with an area of 70 square
kilometers can be cut off by a relatively
short dam. Other tidal-power schemes, all in
embayments of the White Sea and in
estuaries of rivers flowing into it, would use
flood tides of about 30 feet.

The French boast the world's only large
modern tidal-power development. The facility
lies across the estuary of the Ranee River,
which empties into the Atlantic Ocean
between Saint-Malo and Dinard on the coast
of Brittany. An average tidal range of 27

feet is utilized in 24 units, each rated at
10 megawatts, providing an annual
production of 544 million kilowatt-hours.
Inaugurated late in 1966, this power plant is
notable for its development and use of the
turbine, essentially a horizontal-axis
propeller turbine with variable pitch runner
blades. The turbine is connected to a
generator enclosed in a nacelle or bulb
upstream from the turbine in the passage by
which water is conveyed to the turbine. The
runner is so designed that it can operate as a
turbine with flow from the basin to the sea
or from the sea to the basin, and pump in
either direction as well. It can also serve as
an orifice, passing about 50 percent of its
normal flow.

Electricite de France has also carried out
extensive tidal-power investigations in L'Aber
Vrach on the northwestern coast of Brittany
and in the vicinity of Mont St. Michel near
St. Malo.

In North America, studies of large-scale,
tidal-power developments at various sites
have been made during the last six decades
by both Canadian and American agencies.

0

32

Two only are discussed herein: the Bay of
Fundy and its western arm, Passamaquoddy
Bay. Both boast the exceptionally high tide
ranges and large controllable embayments
basic to economic tidal power. Tides in the
Bay of Fundy are semi-diurnal. The interval
between the transit of the moon and the

TABLE 1

Tidal Ranges at Locations of
Potential Tidal Power Developments

Site

Location

Tidal Range (ft.)
Maximum Minimum

7.1

Mary's Pt. to Grindstone Is.

43.7

19.1

to Cape Maringouin

7.2

Ward Pt. to Joggins Head

44.4

21.6

8.1

Economy Pt. to Cape Tenny

52.9

23.9

occurence of high water is nearly constant:
the tides are extremely regular, there being
two tides of nearly the same magnitude and
pattern each 24 hour, 50 minute lunar day.
Table 1 shows the range of tides encountered
at several sites of interest. The tide is the
so-called anomalistic type, the variation in

range with the distance of the moon from
perigee to apogee being the greatest variation.
The spring tides each month vary by a
relatively small amount.

Reference has been made to the controlled
estuary or embayment. Its importance lies in
the phenomenon of tidal amplification, which
under certain circumstances can materially
modify the tidal range available at a given
location and hence the head utilizable for
power generation. The principal lunar,
semi-diurnal, tide -producing component in
the Bay of Fundy has a wavelength of about
745 miles.* The quarter-wavelength, then,
is approximately 186 miles. Taking the mouth
of the Bay of Fundy as a line running from
Yarmouth, Nova Scotia, to Jonesport, Maine,
the length of the bay is 159 miles to Cape
Maringouin at the head of Chignecto Bay and
178 miles to a line from Economy Point to
Cape Tenny. These lengths are sufficiently
close to the quarter-wavelength to provide a

* Mean depth of the bay is 240 feet.

Model of Passamaquoddy Tidal Power Project. (U. S. Army
Corps of Engineers)

--.

. P,OWER STATION N0.1

'

-^-^

T-J&5*

SWITCHYARD

POWER STATION NO. 2

V

N

33

Map shows three sites (7.1, 7.2, and 8.1) in Bay ofFundy selected for intensive study by
Canadian experts.

partial explanation for the extremely high
tides at the heads of the two arms of the bay.
The vertical and lateral convergence of the
bay from its mouth to its heads also plays
an important role.

The International Passamaquoddy
Engineering Board, in its report of October,
1959, recommended for specific design and
costing a tidal-power project using
Passamaquoddy Bay as the high pool, with
Cobscook Bay in Maine and Friar Roads in
New Brunswick as the low pool (see map).
The power plant, located at Carryingplace
Cove, would have thirty 320-inch propeller-
type, vertical axis turbines driving 10-
megawatt, 13.8-kilovolt, 60-hertz
generators at 40 rpm, operating under an
average head of 11 feet. Connection with a
hydroelectric plant was studied, as was a
pumped-storage operation on a river
emptying into Passamaquoddy. Though the

investigation showed that the dependable
capacity of the combination would amount
to 323 megawatts and net annual generation
to 1759 million kilowatt-hours, the scheme -
and later variants - were found to be
uneconomic.

In August, 1966, the governments of
Canada, New Brunswick, and Nova Scotia
set up the Atlantic Tidal Power Programming
Board and the Atlantic Tidal Power
Engineering and Management Committee,
for which latter the author was the Study
Director. Between November, 1966, and
March, 1970, twenty-three sites — all in
the Bay of Fundy — were looked over in a
preliminary manner, and, after two series of
evaluations, three were examined in detail
(see map). Investigations covered all relevant
aspects of tides, geology, ecology, foundation
conditions, ice formation, construction,
generating equipment, transmission,

34

production, and costs of tidal-power and
alternative systems. A computer was used
to help assess the significance of the
implantation of tidal-power plants on the
tidal regime of the Bay of Fundy.

Several practical power schemes received
consideration during this study. These were
selected from a range of proposals, many
extremely complex and correspondingly
costly. The intricacy often sprang from efforts
to correct the basic weakness of tidal power:
a. variable production not necessarily in phase
with human needs. Selected for special study
were:

The single-effect, single-basin scheme. The
Dldest form of power generation, it was the
basis of many tidal mills operating in Western
Europe during the tenth and eleventh
:enturies. The basin is filled on the flood
:ide, and the sluice gates are closed at the
high point of the cycle. Generation begins
thereafter, the unit turbine operating on the
difference in level of the water in the basin
ind that in the sea. In principle, operation
in reverse is feasible, but production will be
somewhat less. The single-effect, single-basin
scheme can produce variable "slugs" of
energy but no sustained power.

The double-effect, single-basin scheme.
Exemplified by the Ranee development, it
utilizes civil works similar to those of the
dngle-effect, single -basin concept, since it
nvolves a single basin with double-effect
generation and pumping plus use of the
generating units as orifices to supplement
iluiceway capacity. Power is generated during
Doth filling and emptying phases. Starting
.vith the point in the operating cycle of the
dngle-effect, single-basin concept where the
turbines are under the minimum head at
which generation is feasible, the runner blades
ire feathered and the turbines function as
Drifices which, with or without the sluices,
smpty the basin to a level equal to that of the
sea. After closure of the sluices and orifices,
and after a suitable waiting period, during
which the sea level rises above basin level, the
generating units begin generation with flow

from the sea to the basin. At the end of the
generating phase the basin is filled, and
subsequent operation with flow to the sea is
similar to that in the single-effect, single-
basin concept. The double-effect, single-
basin concept is capable of producing
dependable power at any desired time during
the solar day. This is achieved at the expense
of energy production, which is less than that
of the single-effect, single-basin scheme.

The linked-basin concept. Suggested for
Passamaquoddy, it entails the use of two more
or less contiguous basins of suitable proportions.
Such conditions exist at the mouths of
Shepody Bay and Cumberland Basin. One
basin can be operated as a high pool and the
other as the low. The linked-basin concept was
developed in response to the need for

The high and low of it at a Fundy dock. (U. S. Army Corps
of Engineers)

35

continuously available power. It requires less
sophisticated generating units than some other
schemes and may be economically attractive
in the relatively few cases where two estuaries
or embayments are physically close and
suitable for development.

The paired-basin scheme. Consisting of
two single-effect, single-basin schemes inter-
connected electrically, this arrangement affords
somewhat more flexibility in operation to meet
market demands. In certain cases where there
is a difference in tidal phase, it may produce
greater benefits than do other approaches.

Pumped storage was also considered as a
supplementary power source for the Bay of
Fundy sites. Although it requires additional
capital investment, its ability to store low-value
off-peak energy for subsequent use as high-
quality, peak energy of maximum value makes
it attractive. A hydraulic, pumped-storage
facility provides flexibility in assigning energy
to best advantage in meeting load
requirements. The capacity and method of
operation selected for the pumped-storage
plant is determined by a number of factors,
such as the volume of the storage reservoir,
the characteristics of the output required by
the system, and the installed capacity of the
tidal-power plant.

The pumped-storage element at the three
Bay of Fundy sites was predicated on both
lower and upper basins using natural
topographical features which could be
enhanced by damming low sectors of the
flow line, with either fresh or sea water
serving as the working fluid. Where rock
types and quality are suitable and a natural
upper basin does not exist, the sea can
substitute for the upper basin and underground
chambers (or, in some cases, worked-out mines
near the coast) for the lower basin.

Another means of upgrading the
production of a single-effect, single -basin
tidal-power plant (the type recommended for
the Bay of Fundy sites) is the substitution of
air compressors for the electric generators.
The air is stored in underground caverns and
released at peak periods of demand to drive

TABLE 2

Cost of Energy At-Site from Single-Effect
Single-Basin Schemes*

Item

Cost of energy at-site mills 7.5

(kilowatt-hour)

Site 7.1 Site 7.2 Site 8.1
8.7 5.6

No firm capacity is produced.

TABLE 3

Cost of Dependable Peak and Energy At-Site from
Double-Effect Single-Basin Schemes

Site 7.1 Site 7.2 Site 8.1
32.65 40.29 25.20

Item

Dependable peak* at site
($/kilowatt)

Energy credit

(mills/kilowatt-hour)

2.31

2.31

2.31

* Available 95% of time (total hour basis), 2 hours/day,
60 days/year.

gas turbine units feeding the power network.

Based on 1968 costs and seven percent
money, costs of energy produced at our three
sites from single -effect, single-basin schemes
are indicated by Table 2, while Table 3 gives
the costs of dependable peak and energy
from double-effect single-basin schemes at
the same three sites. These and other 1968
costs are currently under review by the
sponsors of the Bay of Fundy tidal-power
studies.

The optimized developments were
determined, on the assumption that all of the
output from any of the schemes could be
marketed. The unit costs of power and
energy were based on the total output,
determined from power production studies.
The unit costs of energy were computed
by deducting from the annual costs a credit
of S9.50 per kilowatt of dependable capacity.
The at-site unit costs of dependable capacity
for each of the schemes were computed by
assuming an energy value of 2.31 mills per
kilowatt-hour. The value was derived from
a weighted averaging of displacement energy
values in the regional power system and in

36

;he contiguous northeastern United States
narket, with due allowance for monetary
exchange rates and the proportions of
displacement energy which might be sold in
;he Maritimes and in the United States.

It has been conservatively estimated that
he amount of tidal energy dissipated in the
.hallow seas, embayments and estuaries of
he world is approximately 3 x 106 megawatts.
Phe average potential power for the most
nteresting tidal-power projects in North and
South America, Europe, and Asia has been
:stimated at 63,775 megawatts, of which
ibout 13,000 megawatts might be abstracted.
7ederal Power Commission and Electrical
Vorld data place the total USA electric
?ower industry capability at the end of last
fear at 438,492 megawatts, and hydroelectric
:apability, including pumped-storage, at
)1,280 megawatts. The maximum probable
vorld tidal-power capability would be,
•espectively, about 3.0 percent and 21.2
)ercent of these amounts. Thus tidal energy
:an be important, locally, if it cahnot be a
najor contribution to national energy

•esources.

A good deal remains to be done before
nan can deal effectively with tidal power.
The basic theory necessary for its
development has been well established,
•iowever, substantial exploitation will require
Drior determination of the project's effect
Dn the tidal regime of the waterway involved.
Dther necessary oceanographic work involves
study of the tidal currents throughout the
Abater column and the nature and movement
:>f deposited and waterborne sediments.
'Civil engineering features, relatively well
idvanced at this time, thanks to the
experience with the Ranee Development,
the Dutch Delta Plan, and the Bay of Fundy
studies, will benefit immensely from the
North Sea oil and natural gas exploration and
production.) The design, efficiency, and cost
of generating equipment can also be improved,
although much progress has been achieved
with the bulb and straight-flow turbines.
Considerable research on the pneumatic form

of storage may well return appreciable
economic benefits, as will work on the merits
and demerits of a hydrogen-electricity energy
source.

Our modern civilization is based on energy
and, to a greater extent each year, on electric
powei. It is all too often forgotten that most
sources of energy and electric power rely on
fossil fuels (coal, oil, and natural gas) and on
uranium -- that is, on fuels which are depleted
with use. When we consume them, we are
dipping into our savings account provided by
a beneficent Creator to serve the world for as
long as it may exist. Evidence of approaching
exhaustion of these depletable fuels is
accumulating. Costs are increasing.
Fortunately, there are a few sources of energy
which are essentially income-type fuels -
interest, as it were, on our inheritance. Of
these sources — water power, geothermal
power, ocean thermal power, solar power,
and wind power -- the tides are among the
most accessible to the hand of man, with
generation accurately predictable for
decades.

THIRD QUARTER-

PHASES OF THE MOON

1
Midnight

TIDAL CYCLE

U. S. Army Corps of Engineers

F. L. Lawton is a Canadian engineer who has specialized in
applications of tidal power. For further reading in this
field: Lawton, F. L., "Tidal Power in the-Bay of Fundy,"
Tidal Power, ed. by T. J. Gray and O. K. Gashus, Plenum,
New York, 1972; Lawton, F. L., "Economics of Tidal
Power," Tidal Power, ed. by T. J. Gray and O. K. Gashus,
Plenum, New York, 1972; Vantroys, L., "Interferences
with Tidal Regimes Caused by the Operation of a Tidal
Power Plant," Les Usines Matemotrices Francaises, 1967.

37

Current from the Current

Harris B.Stewart, Jr.

Over the years, many persons, noticing the
swift movement of the Florida Current
portion of the Gulf Stream system off
southeast Florida, have speculated on its
potential as a source of useable energy.
As long as there seemed to be adequate
reserves of fossil fuels to supply our landside
power plants, there was little reason to move
beyond speculation. Then came the
1970's -- the environmental movement, the
fuel crisis — and the idea of a fuel-free and
non-polluting energy source suddenly seemed
more attractive.

In 1973, William von Arx of the Woods
Hole Oceanographic Institution and two
researchers — Dr. John Apel and the author -
from the National Oceanic and Atmospheric
Administration's (NOAA) Atlantic
Oceanographic and Meteorological
Laboratories in Miami began to examine the
Florida Current as a potential source of
additional power for rapidly growing south
Florida. They were fortunate in that Walter
Duing of the University of Miami's Rosen tiel
School of Marine and Atmospheric Science
had just completed analyzing the largest series
of data ever obtained from the Florida Current
off Miami. For the first time, there was solid
information on the temporal and spatial
variations of the Florida Current. Using
Duing's data, von Arx and his colleagues
calculated that if they could trap as little as
4 percent of the flow, they could extract
somewhere between 1000 and 2000
megawatts. Since this was roughly comparable
to the power generated by the local nuclear
power plant, the idea seemed worth pursuing.

The three wrote up the idea and submitted
it to the spring 1973 meeting of the
American Geophysical Union. Although the
paper came in too late to make the abstracts
volume, the newspapers picked up the
concept calling it "underwater windmills,"
and the Miami labs of NOAA were inundated
with requests for more data.

Unfortunately, the two of us in Miami
were primarily oceanographers and incapable
of evaluating the engineering and economic
feasibility of capturing energy from the
Florida Current. But we knew the sort of
people we would need to do the evaluation
that was required: ocean engineers, heavy
marine equipment specialists, turbine design
engineers, corrosion and fouling experts,
energy economists, an oceanographer or two,
and several others to round out the team.

Somehow word of our plans got into the
press, and John D. Mac Arthur of Chicago and
Lake Park, Florida, read about it. The concept
of a fuel-free and non-polluting source of
energy was attractive to him, and he came
down to Miami to talk with us. In this way the
idea of the MacArthur Workshop was born.

Workshop participants met for three days
at the end of February, 1974. Walter Duing
brought his basic data on the Florida Current,
Toby Muir from the Florida Power and Light
Company had the data on the long-term
requirements for south Florida, and William
Shoupp and Edward Somers brought their
combined knowledge of turbine engineering
from Westinghouse. Dugan Johnson came
from Allis Chalmers; Perry Pepper, a propeller
specialist, from Edo Corporation; Herman

38

0 Km

60

780-

84CM

Hean-flow conditions in the Florida Straits off Miami,
iveraged over one diurnal tidal cycle. NWF profile
ndicates northward currents during June 14-15, 1971.
iWF profile indicates southward-flowing water (shaded)
in June 17-18. Values on the isolines are in centimeters
jer second. (W. Duing, RSMAS, University of Miami)

Sheets from the Department of Ocean
Engineering at the University of Rhode Island;
Robert Wiegel from the Department of Civil
Engineering, University of California,
Berkeley; William Heronemus from the School
:>f Engineering, University of Massachusetts;
md Wilbur Kirk from the Francis L. LaQue
Corrosion Lab of International Nickel. Others
from government, industry, and the private

780

840

sector completed the group.

The workshop concluded that there is a
large resource available in the kinetic energy
in the Florida Current portion of the Gulf
Stream, roughly equivalent to that produced
by twenty-five 1000-megawatt power plants.
Some 2000 megawatts of power could be
extracted by practical systems from that
stretch of the current running conveniently
close to the east coast of southern Florida.
There might be reluctance to commit
research and development efforts to a process
yielding such modest results. However,
findings arising from these efforts would be
directly applicable to other processes of

39

energy extraction, such as ocean temperature
gradient and oceanic wind systems.

It was therefore proposed that a phased
study and development program be initiated,
aimed at demonstrating commercial feasibility
of extracting kinetic energy from the Florida
Current. The first phase, a 12-month
undertaking by a 15-man team, would
investigate the feasibility of proceeding with
experimentation and model studies leading
to a proof-of-concept demonstration facility.
Areas of concentration would include:

1. The oceanography and meteorology
of the target area, with emphasis on
quantification of the kinetic energy resource
and analysis of the local and global impact of
its extraction.

2. Determination of proper mooring
methods, including long-life hardware
components and methods of implanting and
servicing.

3. Estimation of loadings from wind
waves and hurricanes and the development of
devices to offset these stresses.

4. Analyses of at least five types of
momentum exchange devices, from the
standpoint of both economic and technical
feasibility.

One device discussed by the workshop was
the open propeller, the original "underwater

windmill." Engineering considerations dictate
that its blades would have to be about 100
meters in length, a drawback given the
velocity gradients found in the current (one
blade tip might be in a slow-moving layer,
another in a fast-moving one). The Kaplan
turbine, a ducted device, would encounter
similar problems. The Savonius rotor, a small
version of which is used on current meters,
was brought up for discussion. So, too, was
the Voith Schneider-type propeller. Basically
a number of vertically arranged blades
attached to a large horizontal disc, the
turbine has a larger inlet area and a larger
mass flow, and therefore develops more
horsepower than comparable devices of
different design. Its shaft speed would be
about two rpm in the Florida Current.

The fifth device examined was the Water
Low Velocity Energy Converter (WLVEC),
developed by Iowa inventor G.E. Steelman.
The converter is operated by parachutes
attached to a continuous belt, which they
pull along as they move with the current.
The chutes collapse as they complete the
circuit, opening again for the next trip. The
concept is both simple in design and
considerably cheaper than the other devices
discussed.

Examined also were a number of
different concepts for collecting or

WLVEC

Overhead view

Anchor

Ship

Working line

Pulley

Resting line

G. E. Steelman

40

extracting the energy at the site and delivering
it to the market in a desirable form and at an
attractive price. Electricity or gaseous
hydrogen fuel delivery systems should be
looked into. At a minimum, alternating or
direct current via cable, or compressed air via
hose and pipeline, should be examined as
energy umbilicals. Decisions should also be
made whether or not to design storage sub-
systems adequate to buffer against diurnal
and seasonal variations. Such installations
might lead to a system capable of delivering
peaking power, whose value is much greater
than that of base load electricity.

Workshop participants recommend further
that if the results of Phase I indicate the
project should be carried forward, consideration
should then be given to moving into an
engineering design and experimentation
program. The goal here should be at least
one total system design from which the
working drawings for a proof-of-concept
power plant could proceed. The Phase II
effort would include laboratory experiments,
construction and testing in the ocean of scale-
model subsystems, and preparation for zero
order specifications and cost estimates. The
Phase II effort should probably be concentrated
under one program manager and should have
a strong industrial flavor.

The results of the second phase should

CURRENT FLOW

Getting nowhere fast. Ship is anchored in the Florida
Current. (W. Duing, RSMAS, University of Miami)

allow a sound decision to be made by potential
sponsors on the actual construction and
operation of a proof-of-concept plant, a
prototype probably of 5- to 20-megawatt
capacity. Such a plant would require two
years to complete. The project probably
should include participation by the utility,
public or private, that will sell the delivered
product.

Preliminary cost estimates developed
during the workshop indicate that plant
construction costs and retail energy prices for
a system utilizing the kinetic energy of the
flowing Florida Current would, in all probability,
be competitive with those projected for other
energy sources in the 1980 era. In short,
useful energy can be extracted from the
flowing Florida Current, if the studies, design,
and construction proposed by the MacArthur
Workshop are each carried out successfully
in sequence, the system can effectively
supplement other sources to help meet the
demand in those areas where relatively fast
currents are found close to shore.

Harris B. Stewart, Jr., is Director of the Atlantic
Oceanographic and Meteorological Laboratories, the
National Oceanic and Atmospheric Administration.
Requests for the Proceedings of the MacArthur
Workshop should be directed to his office,
15 Rickenbacker Causeway, Virginia Key, Miami,
Florida 331 49.

41

Sea

Structure

Stephen C. Dexter

The ocean is an aggressive environment in which
most of the ordinary metals and alloys used in the
construction industry deteriorate rapidly. Materials
selection for both large marine structures and
marine instrumentation systems is a difficult
problem. No longer can we afford to overwhelm
corrosion problems by overgenerous design and
large factors of safety. We must look increasingly
toward efficient engineering design to make
offshore and submerged marine structures
economical.

Selection of materials offering the best
combination of strength, corrosion resistance, and
cost should be undertaken as part of the design
phase of a structure. From an engineering viewpoint,
the most attractive materials often are those with
a high strength-to-weight ratio such as the high-
strength steels, titanium alloys, and aluminum alloys.
Table 1 compares some important properties and
costs of these and other classes of metallic materials.
There are specific problems associated with using
each of them in marine applications. The high-
strength steels corrode uniformly at a rate of three
to fifteen thousandths of an inch per year
(3-15 MPY). Moreover, if their yield strength is
above about 180,000 pounds per square inch (psi),
they are subject to stress corrosion cracking
(SCC) — a particularly damaging form of stress-aided
corrosion resulting in the propagation of sharp
cracks through the structure. They must therefore
be protected from the marine environment if they
are to be used successfully.

The medium- and high-strength aluminum alloys
are competitive with steel on a strength-to-weight
ratio basis. However, their low modulus of elasticity
(a measure of elastic stiffness) means that they are

too flexible for many large structures. In their
highest strength condition, they are subject to SCC,
as are the high-strength steels. Unlike the steels, they
are vulnerable to pitting, crevice corrosion, and
intergranular corrosion — all extremely localized
forms of attack leading to perforation of the metal
or loss of strength. They too must be kept from
direct contact with the environment and thus are
rarely found as structural members of large
underwater marine installations subjected to tensile
stresses. They are used frequently and successfully
for topside structural applications to minimize
total weight and for small instrument pressure
casings, which, when deployed, will be under
hydrostatic compression, sufficient to eliminate the
possibility of cracking.

Titanium and titanium alloys are used
increasingly in condenser tubing and other items
needed by the marine industry. They possess
relative immunity to all forms of seawater attack
at ambient temperatures (except for SCC in the very
highest strength condition) an elastic modulus
higher than that of the aluminum alloys, and in the
heat-treatable varieties, very high strength-to-weight
ratios. They are thus attractive for small, fully
submersed structures in instances where either the
desired lifetime is long (10 to 20 years or more)
and the cost of maintaining a steel structure is
prohibitive, or where corrosion of other materials
would cause personnel hazards (as it would in the.
case of submersibles and habitats). Their high cost
and difficulty of fabrication often make them
unsuitable for use in large structures.

Fortunately, uniform attack, pitting, and
sometimes crevice corrosion and SCC can be avoided
by applying cathodic protection in conjunction with

42

Scanning electron micrograph of a corrosion pit in
aluminum-magnesium-silicon alloy, widely used in marine
science applications. Specimen was submerged in seawater
for a week. Diameter of central pit is approximately
one-thousandth of an inch. Note extensive branching,
which amplifies damage.

43

TABLE 1

Class of Material

Modulus of Elasticity
(lb/in2 x 106)

Yield Strength*
(lb/in2 x 10 3)

Strength-to-Weight Ratiot
/yield strength \

Base Costtt

($/lb)

\density in seawater f

High-strength titanium alloys

16.5

120-155

1260

5-10

High-strength steels

29

110 -340

1200

High-strength aluminum alloys

10.4

15 -78

1200

.50 -.60

Age-hardening stainless steels

28.5

110 -185

762

1.25 -2.00

Unalloyed titanium

15

25 - 85

675

4-6

Nickel-based superalloys

29 -30

50 - 175

675

3-12

Medium-strength steels

30

60 -140

567

Plain carbon and low-alloy steels

30

40 - 80

325

-.10

Cupro-nickel alloys

18 -22

16 -80

275

1.00 - 1.50

300 series stainless steels

28

35 -45

175

.50 - 1.25

* Numbers indicate the maximum range attainable for this class of materials.
t Figures are based on the highest yield strength of the range shown,
ft Costs, quoted for large quantities, were in effect in June 1972.

coatings systems. Cathodic protection, using either an
auxiliary power supply or sacrificial anodes, is the
process by which one reverses the polarity of the
naturally flowing electrochemical corrosion
(electrolysis) current, thereby preventing corrosion
of the structure.

Adequate protection of a given structure is not
always possible. For instance, cathodic protection
cannot be used to prevent ultra-high-strength steels
from cracking, because the hydrogen that this
process generates at the steel surface is itself
damaging to the structure. The aircraft industry
successfully uses metallic coatings to keep moisture
away from high-strength steel components, but in
seawater these coatings would have to be maintained
in near-perfect condition. The practical impossibility
of doing this virtually eliminates the ultra-high-
strength steels from consideration for large structures
that are partially or wholly immersed in seawater.
The medium-strength, low-alloy and plain carbon
steels, which are generally not subject to SCC in
seawater, have less stringent protection requirements.
Even so, the yearly cost of controlling uniform
corrosion by maintaining coatings and cathodic
protection systems cannot be overlooked.

A great number of exotic materials having
increased resistance to corrosion are available, but
most of them are unsuitable for building large
structures. The common stainless steels with more
than 12 percent chromium do not rust uniformly in
seawater, as does plain carbon steel. However, they
undergo severe pitting and crevice corrosion
(localized rates of attack as high as 5 inches per year

with rapid perforation of the metal have been
reported). If welded improperly, these materials
may also be damaged in the heat-affected zone of
the weldment by a form of intergranular corrosion
sometimes known as weld decay. These problems
plus higher cost (see Table) generally limit the use
of the standard stainless steels to topside hardware
or, in fully submersed applications, to easily
replaceable parts and short exposure (roughly six
months or less), or to instances where cathodic
protection can be applied.

The nickel-based "super alloys" are finding an
ever increasing market for critical applications where
very low corrosion rates are desired. The nickel-
chromium-high molybdenum alloys are particularly
resistant to all types of attack in seawater (except
for intergranular attack in the heat-affected zone of
weldments) over periods exceeding 25 years, even at
elevated temperatures. However, their low strength-
to-weight ratios and high cost limit their use to
critical applications where no corrosion can be
tolerated.

All of these materials, from plain carbon steel
to titanium alloys, have a common problem when
used in warm coastal waters — biofouling. The
attachment of marine fouling organisms can have
various effects. If not controlled, it can add
substantially to the weight of floating or semi-
submersible structures, necessitating more costly
and less efficient construction. On the other hand,
marine fouling can slightly reduce the corrosion
rate of plain carbon steel by creating a barrier
between the seawater and the structure. Avoiding

44

biofouling requires the added expense of applying
and maintaining a toxic coatings system. The
only metallic alloys available that possess a natural
toxicity to marine fouling organisms are the high-
copper alloys and especially the series of
cupronickel alloys with more than 70 percent copper.
These alloys corrode uniformly at rates of 0.8 to
1.5 MPY, continually releasing toxic Cu ions into
the water surrounding the structure. They are
initially more expensive than carbon steel, but if
the above rate of corrosion can be tolerated, they
are maintenance- free (i.e., no coatings system or
cathodic protection is needed) over the entire
design lifetime. The 90-10 cupronickel alloy has
recently been used successfully for the hull of a
90-foot shrimp boat.

Our dependence on toxic materials for fouling
control may decrease in the future, however, if the
interdisciplinary research efforts now under way
are successful. Investigators at several laboratories,
including the Woods Hole Oceanographic Institution,
are trying to understand why the surface energy of
structural materials (analogous to the surface tension
of a liquid) changes when they are exposed to
seawater, and why these changes sometimes reduce

the tendency of marine microorganisms to attach
to the surfaces. As we begin to understand these
processes, we may be able to use them to control
at least some types of marine fouling by purposely
altering the surface energy of a structure rather
than by using toxic agents.

The problem of choosing the best material from
which to build marine structures, then, is one of
evaluating a series of trade-offs. In each case it must
be decided which is more important: initially high
materials cost or subsequent high maintenance costs.
In general, as one opts for materials with increased
corrosion resistance, one finds higher cost, lower
strength-to-weight ratio, decreased ease of
fabrication, and decreased availability. For these
reasons, the medium strength, low alloy, and plain
carbon steels are usually chosen for large marine
structures. The maintenance requirements of such
structures under the difficult conditions imposed by
the marine environment will add to the cost of
harnessing the reservoirs of energy stored in and
under the world's oceans.

Stephen C. Dexter is an Assistant Scientist in the
Institution's Department of Ocean Engineering.

Jan Hahn

45

Nuclear Powe

Stations

Michael W. Golay

The concept of floating nuclear power
stations in the ocean has been receiving
enewed attention of late. A commercial
/endor has come on the scene offering to
Dirild and site barge-mounted, pressurized
Abater reactor (PWR) power stations in the
>ea. What for more than a decade had been
i speculative design concept has suddenly
oeen transformed into a possibly imminent
bnvironmental, social, legal, and economic
•eality -- complete with promise and
problems.

There are several strong advantages to
)ffshore-sited power station concepts, not
ill of which are embodied in any single
lesign. Among them:

Proximity to load centers. About half of
he United States electrical demand load is
located within 300 miles of the shorelines of
I he two oceans and the Gulf of Mexico,
loughly 42 percent of the national total is
:oncentrated along the Atlantic and Gulf
;oasts, an important point given the fact that
he continental shelves off these coasts
ypically extend for tens of miles out to sea.
)n the West Coast, the ocean depth increases
apidly with offshore distance, and very few
lesirable power station sites exist.

Automatic exclusion zone. Because the
pace between a station and the shoreline is
isually lightly populated, a large exclusion
rea is automatically incorporated into any
>ffshore siting scheme. The distance between
land-based station and its site boundary is
ypically a few hundred yards, while the
eparation distance for an offshore station is
m the order of three miles. This tends to
educe the potential hazard to the public
rom high-level, airborne, radioactive releases
n the unlikely event of a disastrous accident
nvolving loss of reactor coolant.

Reduced environmental impacts. The
>rincipal environmental impacts of electric
>ower production related to a specific power
tation are those of waste heat emissions,
outine radioactive releases, nuclear fuel

"rojan nuclear power plant in Washington. Sites on land are
ncreasingly hard to come by. (EPA-Documerica, Gene Daniels)

transportation, power transmission, and
scenic disruption. The capacity of ocean
areas to assimilate heat and wastes near the
station is typically greater than that of inland
water bodies. In most cases, it will greatly
reduce the hazards to the local aquatic
ecosystem arising from power station operation.

- Any offshore power station probably
would use a once-through cooling system in
which water would be drawn from the ocean,
pumped through the condenser, and returned
to the ocean. Environmental protection
groups have proposed that cooling towers be
used instead. However, the towers cost about
$20 million more per 1000 megawatts of
electricity (MWe) than once-through cooling
and require an installation covering more than
ten acres. They are not apt to be used unless
a far more compelling case can be made that
serious environmental damage is likely to
result from use of once-through cooling. The
system, of course, cannot be used
indiscriminately: the station must not be sited
near important spawning or feeding areas;
water intake and hot-water discharge structures
must be designed to avoid fish entrainment
and minimize local temperature changes.

- Waterborne radioactive releases from
modern nuclear power stations are negligible
when compared to other sources of radiation
exposure (e.g., natural background, medical
radiation procedures, airline flights, color
TV's, microwave ovens, etc.). Human
exposure to these releases would be further
reduced by the assimilative capacity of the
ocean.

- An exceptional advantage to offshore
siting involves human protection from routine
airborne radioactive releases. The ocean
exclusion zone will provide an extra
unpopulated expanse over which dispersion
of the radioactive plume can occur.

- Fuel transportation would occur via
barge rather than truck or rail car, and
offshore siting offers little advantage or
disadvantage in this area.

- Aesthetic problems involving land-based
power stations usually arise from objections

47

to the appearance of the station structures,
and to the scenic disruption associated with
the required transmission lines. In the case
of offshore siting, the transmission lines to
shore would be laid out of sight on the ocean
floor and the proximity of such stations to
load centers offers the promise that fewer
and shorter overland transmission lines would
be required than with land-based power
generation. A recent study indicates that to
a viewer on the beach the apparent size of its
2300 MWe complex cited three miles
offshore would be similar to that of a large
passenger liner.

Abundance of offshore sites. Many
potential offshore power station sites are
available, while equivalent land-based sites
are becoming scarce — so scarce that it is
common practice today in the major load-
center areas to cluster several generating units

Offshore nuclear power systems must be designed to avoid
destruction of marine life. (EPA-Documerica, James H.
Pickerell)

on a single site. Clusters can be found at the
Millstone Site of Northeast Utilities on Long
Island Sound, the Indian Point Site on
Consolidated Edison on the Hudson River,
and the Dresden Site of Commonwealth
Edison in Central Illinois.

Assembly line production. Nuclear power
is the least expensive means of electrical energy
generation in practically every part of the
country today. In spite of this, only about
60 percent of all orders placed for new
generating capacity are for nuclear power
stations. The major impediments are the high
capital costs of a nuclear power station
(currently about $400-$700/kWe) and the
scheduling uncertainty associated with
obtaining an operating license from the U.S.
Atomic Energy Commission. The interest
charges for completed 1000 MWe station are
approximately $100,000 per day. Thus, the
costs of licensing delays at the end of
construction can be significant; it is fear of
such costs which has been a primary
motivation for early accommodation between
utilities and environmental protection
intervenor groups.

An advantage of many offshore siting
concepts is that some long-term reductions
in capital costs and in licensing delays may
be possible due to the assembly-line
fabrication of such plants. The associated
standardization of designs and mechanization
of many construction steps offer the
expectation of increased construction speed
and of a more rapid licensing review of the
standardized portions of the plant. The net
result would be less expensive power stations
and — depending upon the attitudes of the
various state utility commissions -- lower
electric bills to consumers.

Seismic protection. One of the important
sets of hazards which must be anticipated in
the design of a land-based station is that of
earthquake-initiated accidents, the most
severe of which would be a loss-of-cooling
accident. Floating stations are effectively
insulated from most earthquake hazards and
are thus free from the costs and design

48

;onstraints associated with seismic accident
?rotection systems.

A variety of offshore power station
:oncepts have been proposed, some without
Breakwaters — structures designed to
provide protection from waves, wind, and
;ollisions with seagoing vessels. It seems
ikely that any station susceptible to such
lazards would be required to have a
protecting breakwater in order to obtain
)ublic acceptance and the approval of the
Carious state and federal regulatory agencies
:oncerned.

The only type of offshore power plant
:urrently for sale is the floating, barge -
nounted station offered by Offshore
}ower Systems, a company combining the
eactor technology of Westinghouse Electric
oorp. and the shipbuilding ability of
"enneco, Inc. (via the Newport News
Jhipbuilding Dry Dock Co.). The firm is
offering to build standardized 1150-MWe
mits in a new shipyard to be constructed
tear Jacksonville, Florida. The units
vould be towed to the power station
ite, at which a protective breakwater would
^ave been prepared. The barge would be
loated into place and anchored. Single-site
omplexes are envisioned, enclosing one
ir — more commonly -- two barges within a
ingle breakwater. Once the barges are in
lace, the breakwater construction would be
ompleted (see Figure 1); small canals would
I '6 left open on the sides to accommodate the
low of material, personnel, and tides.
Yansmission connections would then be made,
uclear fuel loaded, start-up tests performed,
nd full-power operation initiated.

Each barge displaces 155,000 tons and
.raws 31 feet. It is 209 feet high, 400 feet
Dng, and 37 8 feet wide; it contains all of the
sual components of a land-based power
tation, including a containment building and
he standard safety systems. Estimated cost
f the barge unit alone is approximately
350 million.

A minimum depth of 45 feet is required
n the 90-acre lagoon within the breakwater

in order to assure adequate draft over the
life of the barge, and a maximum site depth
of 71 feet is imposed by increasing breakwater
costs. The breakwater would be constructed
of a core of concrete caissons, and covered
with momentum-absorbing "dolos," which
come in a variety of sizes. The structure is
designed to withstand collisions with the
largest ocean vessels. It is high enough to
deflect the largest wave expected at the site
within a 100-year interval.

As of this writing, Offshore Power Systems
has sales commitments of varying degrees of
finality for eight stations. The barge
construction yard is expected to cost about
$210 million, and the company has stated
that firm orders for six to eight units are
required to justify the initial investment.
Thus, it would appear that the threshold sales
commitment will be obtained soon.

There are, of course, other ways of
locating a nuclear power plant offshore. One
is to place the plant on a large, permanent
artificial island. In its simplest form the
island would be constructed in a landfill
operation. Another related design calls for
concrete piles, driven to bedrock and
surmounted by a reinforced concrete
platform. Yet another would have the power
station built on the ocean floor inside a
concrete and rubble cofferdam, which would
hold back the ocean and serve as a collision
shield and breakwater. Because of the high
cost of the dam or island, these proposals
would be most attractive in shallow waters.
In each case the power station would be
virtually identical to that built on land. The
final "island" concept is a variation on the
Offshore Power Systems theme in which the
barge -mounted station would be floated into
place within a breakwater and sunk -- but not
submerged — in shallow water. An advantage
of all of these approaches is that the station
is not vulnerable to sinking or flooding due
to a hull rupture. Also, in the very unlikely
event of a core melt-down, there would be
no direct path for fission products contained
in the core to enter the ocean. Obviously,

49

mi

FIGURE 1. Aerial view of a typical 2300-MWe Offshore Power Systems generating station, consisting of two barge-mounted
generating units floating in a 90-acre lagoon. Note breakwater design with curved section facing seaward. (Westinghouse-Tenneco)

in most of the "island" concepts, the
offshore siting advantages of assembly-line
fabrication, and seismic protection would be
lost.

Stations could also be built in the form
of a submersible designed to rest on the ocean
floor at least 200 feet below the surface -
safe from storms and surface traffic. The
hazards here would be those of collisions
with submarines and failure of the vessel wall.
The most suitable area for this concept is
on the U.S. West Coast, where deep-water
sites near shore are common. A unique
attraction of the concept is the added
safeguard provided by hydrostatic pressure
acting against the submersible's hull: under
these conditions, internal pressures generated

by an accident would have to be exceptionally
high to overload the containment. In addition
the cost of a breakwater could be avoided.

There are several legal, financial, and safety
concerns which could hinder or prohibit the
advent of offshore power station siting. They
are being faced for the first time in the
licensing process involving Atlantic
Generating Stations I and II -- the Offshore
Power Systems units being purchased by
the Public Service Electric and Gas Co. in
New Jersey. The stations could easily be sited
further than three miles offshore. However,
in order to simplify the legal questions which
must be treated, it was decided to place them
within U.S. territorial waters. Even so, there
are a number of rather novel legal problems

50

^^^HJ^d

•

vhich must be resolved. Some of the
Dotentially interested agencies are the U.S.
3oast Guard, Atomic Energy Commission,
Environmental Protection Agency, Federal
-'ower Commission, and several offices of the
State of New Jersey. Precedents will be set
n this case regarding jurisdictions of the
:oncerned agencies, legal definitions (e.g., is
:he station a ship or a barge?), environmental
Drotection criteria, and safety regulations -
imong other matters. The details of these
decisions will be important in determining
che attractiveness of offshore siting to
investors, and its acceptability to the public.
They will also determine the degree to which
anticipated cost savings from speedy
licensing and shipyard fabrication will be

realized. Estimated costs for the first-
generation Offshore Power Systems stations
are somewhat above those of comparable
land-based units, and with so many substantial
matters yet to be settled, optimistic financial
forecasts must be treated skeptically.

As for reactor safety, the primary concern
involving the floating design has to do with
propagation of fission products in the ocean
if loss of coolant were to result in a core
melt-down. Should the very improbable
happen, the molten mass of reactor material
could conceivably -- but not certainly -- melt
through the bottom of the barge and come
into contact with the ocean water. The
Offshore Power Systems design does not
incorporate a "core-catcher" (a system
capable of containing and cooling the mass of
molten reactor material in a subcritical
configuration) below the reactor to deal with
such an eventuality. A number of
"core-catcher" designs have been proposed,
but none has been tested fully — since this
would require a core melt-down. (Here as
elsewhere in reactor safety technology, the
cost and hazard of the tests required to settle
the question finally are prohibitively great.)
The choices remain: whether to invest
available resources in a very reliable emergency
core cooling system, which will aim to insure
that a "core-catcher" is not needed; or
whether to proceed with a "core-catcher" as
a backup system, even though its adequacy
and necessity may be incompletely
demonstrated.

Independent studies indicate that the
likelihood of a catastrophic accident following
a massive failure of an emergency core cooling
system is very low, less than one in one
million per reactor year. This would tend to
favor the argument against the need for the
"core-catcher." This point of view is
buttressed by society's tolerance of many
activities where the probability of disaster,
though low, could be minimized even further.
Commercial aircraft fly without parachutes
for their passengers, let alone adequate

51

emergency exits or fire-resistant clothing for
use in crash-landings. Towns and villages
are sited directly below high dams. High-rise
buildings are constructed without exterior
fire escapes or sprinkler systems.

An important item in this debate is the
estimation of what will happen should fission
products be released at sea. As in a loss-of-
coolant accident on land, the greatest
immediate hazard to humans stems from the
passage of the radioactive plume of steam
and fission products. The ocean exclusion
zone around the offshore plant would provide
an extra degree of safety through additional
plume dispersion prior to human exposure, as
would the "scrubbing" and condensation of
volatile fission products as they bubbled
upward through the water. However, this
last would create a new hazard — the

introduction of solid and liquid fission
products into the seawater, and into marine
food chains. The magnitude of this hazard
has not yet been completely analyzed, though
it would appear initially to be much smaller
than those imposed by passage of the
radioactive plume.

Michael W. Golay is an Assistant Professor in the
Department of Nuclear Engineering at the Massachusetts
Institute of Technology. He has research interest in the
environmental and safety problems of electric power
production, and for the last two years has held the
A. D. Little Professorship in Environmental Sciences and
Engineering. For further reading in this field:
"Considerations Affecting Steam Power Plant Site
Selection," Report to the President, Office of Science
and Technology, U. S. Government Printing Office, 1968;
Ducsik, Dennis W., ed., Power Pollution and Public Policy,
M.I.T. Press, Cambridge, 1970; "Floating Nuclear Power
Plants for Offshore Siting," Westinghouse Engineering,
Westinghouse Electric, 1972.

IS

Environmental instrument tower installed near site proposed
for nuclear plant by Public Service Electric and Gas Co. of
New Jersey. Tower measures wind, currents, tides, and waves
as part of data acquisition program required by licensing
process. (EG&G)

52

MBL WHOI LIBRARY

hlH IfllA (3

Alvin maneuvers into position to be hoisted aboard Knorr. Carrying
Alvin and towing Lulu (the submersible' s tender), Knorr left Woods Hole
early in June bound for the Azores. There Alvin transferred to Lulu
and, after a short passage to the dive site, joined two French submarines
in exploring the rift valley of the Mid-Atlantic Ridge. (Frank Medeiros)

•'X-

. •flt'.

Published by the

Woods Hole Oceanographic Institution

Woods Hole, Massachusetts

CHARLES F. ADAMS
Chairman, Board of Trustees

PAULM. FYE
President and Director

Associates of the

Woods Hole Oceanographic Institution
HOMER H. EWING, Honorary Chairman
TOWNSEND HORNOR, President
JOSEPH V. McKEE, JR., Vice President
L. HOYT WATSON, Executive Secretary

Library of Congress Catalogue Card No.

59-34518

EDITOR: William H. MacLeish

ASSISTANT: Christina Robinson

PUBLISHING

CONSULTANT: Geno Ballotti