The author of this website, Dr. Richard LaRosa, experimented with solar energy and taught courses
in solar thermal engineering during his professional career in microwaves and electronics. He
wrote and edited many articles exploring energy conservation and renewable energy. Reporting on
these technologies made him realize that they would always be practiced on too small a scale to
solve the global problems of climate change, sea level rise, and fresh water shortage. A detailed
study of the greenhouse effect was the first step in the evolution of a more global perspective.
The next step was the idea that we might be able to save the polar glaciers by changing the global
distribution of the solar heat stored in the oceans. Experience during the greenhouse effect study
indicated that the radical nature of the idea and the lack of formal education and credentials in
oceanography and climate science would make it difficult to publish in peer-reviewed journals. The
Internet offered an accessible alternative. The website was kept anonymous to encourage examination
of the ideas rather than the bearer of the message. Of course, anyone who emailed the website received
a reply with full personal contact information.
This website has not been changed since it was established late in 2001. Many books and articles have
been studied in the intervening three and a half years. This has resulted in greatly increased
understanding of oceanography. The focus has been on estimating the power that drives the subtropical
ocean gyres, and determining how much power must be removed in order to reduce their heat transport.
There has been some correspondence and publication, most recently at the Energy Ocean 2005 Conference
in Washington, D.C. A later version of that paper follows in this update. Anonymity is no longer appropriate.
Of the many books and other publications that have been helpful, the most important one has been a textbook,
"Ocean Circulation", Second Edition, prepared by an Open University Course Team, published by
Butterworth-Heinemann in 2002. This book seemed to have just the right descriptions and illustrations
to enable the author to tackle the more formal and difficult publications.
The following paper estimates the power driving the North Atlantic Subtropical Gyre and the effect of
turbines and drag devices placed in the Florida Current and the Gulf Stream.
Earth is warming up and glaciers are melting or sliding into the sea. This, plus thermal expansion, causes
the sea level to rise. The trend appears to be accelerating, and there are predictions of great future
troubles. The World's population is concentrated along the coasts and there is no place for them to go
when the coasts are inundated. Economies in the interior regions are already strained and will not welcome
refugees. Flood control devices can only be used in places whose wealth can support their great cost.
The Earth is warming because the incoming short wave solar energy exceeds the outgoing long wave infrared
radiation. The Kyoto Treaty and conservation efforts attempt to reduce the rate at which greenhouse gases
are being added to the atmosphere. Even if these measures are implemented, greenhouse gases will increase
and the radiation imbalance will persist. Water has large thermal storage capacity and it covers the majority
of Earth's surface, so that its temperature increases slowly but steadily. We have no plan in effect to combat
sea level rise.
I believe we can slow down the loss of land-supported ice and snow (floating ice has already raised sea level)
by changing the distribution of heat over the globe. Solar energy is more intense near the Equator. The Florida
Current and Gulf Stream transport warm water from low to high latitudes. Slowing them down should reduce the
rate of this heat transport. Turbines and drag devices distributed along the length of these streams should
be able to accomplish this slowing. This paper estimates that supplying 14.3 Gigawatts (GW) to the North
American electric power grid and dissipating another 14.3 GW in system losses and turbulence caused by mooring
cables might have a useful effect. The 14.3 GW (14,300 Megawatts) supplied to the grid is less than the peak
demand of the combined New York City and vicinity and Long Island areas.
The Figure above is a skeleton view of the North Atlantic Subtropical Gyre. The Caribbean Current on the
left feeds the
Loop Current in the Gulf of Mexico, which passes through the Straits of Florida as the Florida Current. The
volume transport of the Florida Current is about 30 Sv (30 million cubic meters per second) at 27 deg N
latitude, and increases steadily along its length. The transport is between 70 and 100 Sv at Cape Hatteras,
where the current leaves the Blake Plateau and heads out into open ocean. Its name changes to Gulf Stream
around this point.
The Gulf Stream volume transport increases along its path and reaches about 150 Sv at 65 deg W longitude. Around
this point, 30 Sv branches out of the Gyre and goes north as the North Atlantic Current. It feeds the North
Atlantic Drift and the Norwegian Current. These and other currents transport heat to the Arctic. Air passing
over the ocean is warmed, and also transports heat to the Arctic.
The rest of the 150 Sv takes various clockwise paths around the Gyre. The outermost path includes the Portugal
Current, Canary Current, North Equatorial Current, and Antilles Current, eventually feeding back into the Florida
Current. The Azores Current is part of a more interior recirculation path. There are smaller recirculation loops
along the Gulf Stream which have been sketched in different configurations by different authors. In order for
the volume transport to increase along the path, the loops would have to be nested so that they all originated
near the 150 Sv terminus. The longest loops would feed back into the stream just downstream from where the
Antilles Current flows into it. Progressively smaller loops would feed into the stream at points along the
stream, with the smallest loop feeding in closest to the 150 Sv terminus.
The Gulf Stream flow becomes confusing because it meanders and sheds rings on both sides. There is also some
reverse flow, but the stream gains energy along its path. Measurements over cross sections along the path show
that the maximum velocity hardly changes from Miami to Cape Hatteras and remains fairly high further downstream
even though the flow volume increases. It appears that power, as well as water, is flowing into the stream from
the interior of the gyre.
Some wind power comes from the uneven solar heating of the Earth. The warming is greatest near the equator,
where warm air and moisture rises and moves toward the poles. The movement would be parallel to the meridian
lines and the air would fall near the poles and return to the equator if the Earth were not rotating about
its axis. Because of the Earth's rotation
[http://www.oceansonline.com/winds.htm] this pair of giant
circulation cells is broken up into three circulation cells in each hemisphere. The air falls at the poles
and at 30 degrees N and S latitude. It rises at the equator and at 60 degrees N and S latitude.
The circulation cells closest to the equator are named Hadley cells and the air returning at low altitude
toward the equator is turned toward the west to become the Trade Winds. The circulation cells between 30
and 60 degrees N and S latitude are named Ferrel cells and the low altitude air moving toward the poles is
turned toward the east to become the Westerlies. The circulation cells between 60 and 90 degrees N and S
latitude are named the Polar cells. Low altitude air coming from the poles is turned toward the west to
become the Polar Easterlies.
The turning force is called the Coriolis force. When referenced to an xyz coordinate system fixed to the Earth
with the z-axis perpendicular to the Earth surface, there is an accelerating force on a fluid moving parallel
to the xy-plane. The acceleration is directed perpendicular to the velocity direction. In the Northern Hemisphere,
the acceleration is directed to the right of the velocity, so currents are deflected to the right.
The Coriolis force is a real force and it supplies power to the winds and the ocean. It creates fluid rotation
relative to the Earth's surface such that friction between the fluid and the Earth tends to slow down the
Earth's rotation. The Earth is slowing down, and from the rate of slowing, one can calculate that its stored
rotational energy is being removed at the rate of 4350 GW. Tidal friction dissipates about 3000 GW, so there
is 1350 GW going into the atmosphere and non-tidal ocean processes. This is augmented by thermal energy converted
into mechanical by heat engine processes.
The wind exerts a shear stress on the water surface. The component of the stress parallel to the water velocity
times the water velocity times the area of the current gives the wind power into the current. The Ocean Currents
website of the University of Miami's Rosensteil School of Marine and Atmospheric Sciences has data that
suggests reasonable values of velocity and area for each of the component currents of the North Atlantic
Subtropical Gyre. A wind stress of 0.072 N/m2 parallel to each velocity was assumed. The calculated wind
power input (GW) to each component current of the gyre is shown in Table 1.
| Current | Calculated wind power input (GW) |
|---|---|
| Loop Current | 14.4 GW |
| Florida Current | 21.6 |
| Gulf Stream | 33 |
| Antilles Current | 1.4 |
| Azores Current | 15.4 |
| Portugal Current | 3.4 |
| Canary Current | 49.5 |
| N. Equatorial Current | 20 |
| S. Equatorial Current | 30 |
| N. Brazil Current | 71.5 |
| Guiana Current | 20.4 |
| Caribbean Current | 51.7 |
Power is dissipated due to fast water moving alongside of slower water. Velocity contours at various cross
sections show that the velocity decreases almost linearly with distance from the core of maximum velocity
water. Using a few straight-line segments to approximate the velocity vs. depth at stations spaced 5 km apart
across the Florida Current at 27 deg N latitude, the velocity shear power dissipation was calculated to be
5.33 GW per 100 km of stream length. The assumed eddy viscosity was 0.1 m2/s.
Assume that this dissipation value is true for the entire stream, even though the cross section and volume
transport increase in the downstream direction. The stream length is about 2600 km and the dissipation is 139
GW over this length.
The rate of kinetic energy transport through the 27 deg N latitude cross-section plane is 19.5 GW. The rate
of kinetic energy transport through the output cross section must be greater because the cross section area
and volume transport are much greater. A reasonable guess is that it might be 20 GW greater
Table 1 attributes 55 GW of wind power to the Florida Current and the Gulf Stream. The recirculation inflow
must supply the 139 GW dissipation minus the 55 GW wind power plus the 20 GW increase in kinetic energy transport.
This is 104 GW, which is supplied to the Florida Current and Gulf Stream by the Coriolis force acting on the
inflow of the recirculated water. There is much uncertainty in this estimate. If the dissipation per unit
length increases downstream instead of remaining constant, the inflow water might be supplying 150 GW. We
will use 150 GW for succeeding calculations.
The 150 GW power due to recirculation inflow adds to the 318 GW of wind power to give a total power of 468 GW
driving the North Atlantic Subtropical Gyre. Turbines supplying electric power to the grid and system
inefficiencies and mooring cable turbulence dissipation should slow the gyre down and reduce its heat transport.
The heat generated by the dissipation is negligible compared to the thermal energy stored in the ocean current.
Assume that, as the result of our intervention, the velocity everywhere is reduced by the factor (V/Vo). Before
intervention, the wind power into the gyre is Pwo. This power is proportional to the wind shear stress times
the water velocity. Therefore, after intervention, the wind power into the gyre will be Pwo (V/Vo). This
assumes that the wind shear stress is independent of the water velocity.
The power supplied to the gyre by the Coriolis force on the recirculation water is Pco before our intervention.
The acceleration force on the inflow water is proportional to the velocity component normal to the stream flow.
This acceleration force acts in the direction of the mainstream flow. The power supplied to the stream is this
force times the stream velocity, making the Coriolis power proportional to the square of the velocity. Therefore,
after intervention, the power supplied by the recirculation is Pco (V/Vo)2.
The power dissipated along the stream by velocity shear friction is also proportional to the square of the
velocity. Before intervention it is equal to the total power input to the gyre (Pwo + Pco). After intervention
the shear friction power will be (Pwo + Pco)(V/Vo)2.
The intervention consists of supplying electrical power Pe to the shore grid and dissipating Pd in electrical
transmission losses, generator losses, and mooring cable and drag device turbulence. Setting the input power
equal to the velocity shear dissipation plus the electrical power supplied to the grid plus the added dissipation,
we get Eq.1.
Pwo (V/Vo) + Pco (V/Vo)2 = (Pwo + Pco)(V/Vo)2 + (Pe + Pd) Eq.1
The recirculation Coriolis power cancels out of the equation, and we are left with a simple quadratic equation in (V/Vo).
(V/Vo)2 - (V/Vo) + (Pe + Pd)/Pwo = 0 Eq.2
To reduce the velocity by 10%, set (V/Vo) = 0.9 in Eq.2, resulting in (Pe + Pd)/Pwo = 0.09. The wind power input
Pwo was previously estimated to be 318 GW. Therefore (Pe + Pd) = 28.6 GW. If the generation and delivery system
operates at 50% efficiency, we must deliver 14.3 GW to the grid. This is considerably less than the 18 GW peak
power supplied by Consolidated Edison and the Long Island Power Authority to their combined service areas.
The 10% reduction in velocity will result initially in a 10% reduction in heat transport
rate because it will take time for the temperatures of the tropical water source and the high-latitude receiving
reservoir to change. Eventually, the tropical source temperature will increase and the high-latitude reservoir
temperature will decrease because of the decreased heat transport. This will increase the heat transport slightly
but it will take a long time because of the heat storage capacity of the water. The actual rate of increase in
heat transport due to water temperature change would be an appropriate subject for computer modeling.
A computer model study is required to predict the effect of a reduction in heat delivery of the Gulf Stream on the
loss of land-supported ice in the Arctic. Modeling is also required to verify the estimates made in this paper.
The density of water delivered to the Arctic by the North Atlantic Current should increase because an increase in
the tropical source temperature will result in increased evaporation and greater salinity. Also, the water reaching
the Arctic will be cooler and more dense. The thermohaline sinking and resulting circulation should increase.
In this paper, the North Atlantic Subtropical Gyre was assumed to be driven by wind power and Coriolis forces on
the recirculation inflow. No allowance was made for thermohaline drive of the gyre circulation under the assumption
that thermohaline drive was confined to the North Atlantic Current and the currents that it feeds. There is a
contradiction here, because increased thermohaline circulation will require increased Gulf Stream flow. Future
work will be directed at resolving this issue.
The turbines would be held in place by long cables that slant downward to anchors on the ocean bottom. They would
be axial flow types with multi-blade rotors similar to those on most wind farms. The most significant difference
from wind turbines is the fact that deep-sea turbines cannot be mounted on towers. When producing power, the
rotor exerts a torque on the stator of the alternator. The tower would resist this torque in the case of a wind
turbine. A deep-sea turbine would twist the mooring cable so that no power would be produced. To avoid this
embarrassment, most proposed deep-sea units have two side-by-side turbines rotating in opposite directions. This
achieves a gross balance of the torques on the two stators.
Models of these turbines have been tested in sheltered conditions. Survival in the open ocean requires provisions
to rapidly and accurately balance the torques, particularly if one of the turbines in the pair becomes defective
or if its associated power electronics becomes defective. Tested models have used buoyancy tanks or hydrofoil
surfaces to raise them to proper depth. Auxiliary near-vertical cables must be added to insure that the turbines
are always below navigation depth to avoid ship collisions. Submerging them also reduces the severity of storm
disturbances.
Horizontal and vertical tail surfaces are required to keep the turbines pointed upstream. Center of lift or buoyancy
must be above the center of gravity to provide stability against roll. Perhaps fast automatic balance of the
turbine outputs can be included in the roll control design.
The Gulf Stream changes its position. We must solve the problem of how to continually move the turbines so that
they are always in the fast-moving core. Then there is the problem of sharing the sea with its other users, for
example, the fishing industry. We have also the problem of designing, installing, and maintaining a long-distance
deep-sea power transmission system.
There are western boundary currents of subtropical gyres in the North and South Pacific, the North and South
Atlantic, and the Indian Oceans. They all deliver heat from the tropical waters to the higher latitudes. It may
not be economically feasible to deliver electric power to land from most of them. Drag devices can accomplish
the reduction in heat transport rate. The reader is reminded that the heat created by the drag device power
dissipation is negligible compared to the solar heat carried in the large storage capacity of the water.
It may turn out that the Florida Current is the only western boundary current with a stable path that is close
enough to land to be exploited for electrical power delivery to shore. However, a revival of interest in Ocean
Thermal Energy Conversion (OTEC) was evident at the EnergyOcean 2005 conference. Inefficient conversion of small
water temperature differences into mechanical power is a serious limitation in an OTEC plant. Floating plants
could use electric power from turbines in these western boundary currents to run cold water lifting pumps and
vacuum pumps for the production of fresh water by flash evaporation. There might be similar possibilities in
the production of ammonia.
This paper presents a method of changing the global distribution of solar heat so that less heat reaches the
polar regions. This should result in less land-supported ice and snow melting or sliding into the sea. This, in
turn, should slow down the rate of sea level rise.
Significant results of the paper are:
1. Finite power drives the ocean currents that transport heat from the Tropics to higher latitudes in both hemispheres.
2. The ocean currents and the heat transport can be slowed by removing some of this drive power.
3. Quantitative estimates were made for the Florida Current and the Gulf Stream. Supplying 14.3 GW to the shore
grid should result in a 10% slowing of the current.
4. Computer modeling is required to verify these estimates.
5. In addition to supplying electric power to shore, there is the possibility of supplying power to drive pumps
on floating fresh water and ammonia plants.
By presenting this paper, I hope to encourage people with special skills to examine the idea and to determine
whether it is valid.
Implementation of the idea presents a daunting challenge of obtaining financing, securing and maintaining
international and inter-industry cooperation, and solving many scientific and technical problems. But it may
be the only way that we can slow sea level rise.
I thank EnergyOcean 2005 for the opportunity to present an earlier version of this paper.
I have been helped by brief correspondence with Arthur Mariano of the University of Miami, Walter Munk of the
Scripps Institution of Oceanography, and Carl Wunsch of MIT.
Sea Technology helped me by publishing my "Soapbox" article in their November 2004 issue.
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