Ocean thermal energy conversion hydro well apparatus

An apparatus is disclosed to generate electricity using ocean thermal and salinity gradients. An elongated chamber extends vertically downward from the surface of the ocean. Warm, high-salinity water from the ocean surface flowing by gravity down the apparatus is used to drive a turbine and electrical generator. Air bubbles are introduced into the flow at the upper opening of the apparatus. This air is subject to hydraulic compression as the water falls. The flow of sea water and air passes through a cooling tube near the bottom of the apparatus where it is cooled to the temperature of ambient sea water at that depth. The flow then enters a chamber where the air and water are allowed to separate. Because of its greater density than the ambient sea water at that depth, the water in the chamber tends to flow out exhaust ports located at the bottom of the chamber. Excess air pressure held in the chamber can either be used to operate a booster pump to increase the flow through the turbine, or to assist in exhausting water from the separation chamber.

FIELD OF THE INVENTION 
The present invention relates generally to the use of ocean salinity and 
thermal gradients to generate electricity. In particular, the present 
invention uses these gradients to induce a flow of sea water and entrained 
air through a vertical chamber to power an electrical generator. 
BACKGROUND OF THE INVENTION 
In most oceanic locations around the world the water at depths greater than 
130 meters is relatively fresh, dark, and cold in comparison with the 
surface water, which is warmer and has a greater salinity. Various ocean 
thermal energy conversion (OTEC) inventions have been devised in the past 
to exploit these temperature and salinity gradients between the surface 
and deep ocean to produce power, or to create an upwelling of 
nutrient-rich deep water to the ocean surface for mariculture. For 
example, one simple method involves placement of a long vertical cold 
water pipe into the ocean in such a manner that the bottom of the pipe is 
exposed to cold, relatively fresh water, while the top of the pipe is in 
warm, saline water. A continuous flow of water up the pipe results after 
the fountain is primed, due to an exchange of heat, but not salinity, with 
the ambient ocean. H. Stommel, A. B. Arons, and D. Blanchard, "An 
Oceanographical Curiosity; the Perpetual Salt Fountain," Deep Sea 
Research, Vol. 3 (1955), pp. 152-155. A similar system for surface 
water-deep water counterflow is disclosed by Johnson, "Salinity-Driven 
Oceanographic Upwelling," U.S. Pat. No. 4,597,360, issued July 1, 1986. 
A basic OTEC system for generation of power is disclosed by Claude, et al, 
"Method and Apparatus for Obtaining Power from Sea Water," U.S. Pat. No. 
2,006,985, issued July 2, 1935. OTEC systems of this type have 
considerable appeal in that approximately sixty percent of the world's 
largest cities and two-thirds of the world's population live within 80 
kilometers of the sea. However, existing OTEC systems have either been 
inefficient or not cost-effective due to a number of problems, such as the 
length of the large cold water pipe required; the size of heat exchangers, 
turbines, and evaporators; biofouling, corrosion, and creation of salt 
water gases; and the difficulty of transmitting electricity under water. 
In contrast, in the present invention, hydraulic compression of the 
entrained air is used to assist in exhausting water at the bottom of the 
apparatus, thus increasing the flow through the generator. The present 
apparatus does not require extreme temperature differences, and thus can 
be located close to shorelines near most major cities. This serves to 
minimize the length of electrical transmission lines. The present 
invention does not involve cold water pipes, evaporators, condensers, or 
steam turbines. The heat exchanger is an inexpensive cooling tube which 
serves to limit biofouling and corrosion. 
SUMMARY OF THE INVENTION 
The present invention uses ocean salinity and thermal gradients to induce a 
flow of sea water and entrained air through a vertical chamber to power an 
electrical generator. Sea water flows into an intake manifold located at 
the upper end of the vertical chamber. Air is added to the saline water at 
the intake manifold in the form of small bubbles by an air induction 
vortex. The air is trapped in the falling water and compressed as it is 
pulled downward by gravity through a penstock. The flow of water and 
entrained air is used to drive a turbine and electrical generator to 
create electricity. The water and air are then cooled as they flow through 
a cooling tube which spirals down and around the outside of the vertical 
chamber. The flow then passes over a separating cone in a chamber located 
at the bottom of the apparatus. The trapped compressed air separates and 
rises into the upper portion of this chamber. The cooled, high-salinity 
water tends to flow out a number of exhaust ports at the bottom of this 
chamber because it is denser than the surrounding sea water. The pressure 
of the compressed air in the chamber can be regulated to maintain a stable 
level of water in the chamber. In addition, the compressed air in the 
chamber can be used to drive a booster pump to increase the flow of water 
through the turbine, or to create a stream of air bubbles to increase the 
flow of water out of the chamber through an upwelling tube, if necessary.

DETAILED DESCRIPTION OF THE INVENTION 
A generally cylindrical casing 6 housing the apparatus extends vertically 
from the surface down into the ocean. A depth of 400 feet may be used as 
an average length for the apparatus based on other hydroelectric plants. 
The apparatus may be held in place by moorings attached to the ocean 
bottom. Past research suggests that concrete or polyvinyl chloride may be 
the most cost-effective materials for the apparatus. A cone-shaped top 
extends from the upper end of the cylindrical casing, above the high tide 
and wave limits, to afford easy access to the equipment located inside the 
casing for servicing. Open-grate platforms located inside the casing add 
strength and support equipment where needed. The optimal diameter of the 
cylindrical casing and the water intakes 2 are determined by tide, 
current, and wave conditions. In particular, the screened water intakes 2 
must not remove warm surface water faster than it is available. One 
alternative would be to construct a series of smaller apparatuses grouped 
around a central platform where one crane could service the entire group. 
Prior to commencing operation of the apparatus, the separation chamber 15 
must be pressurized with air before water is allowed to enter the water 
intakes 2. In addition, the upwelling tube 14 must be primed to create an 
upward flow of water. Operation of the apparatus is commenced by allowing 
water to enter the water intake 2. The water is then drawn by gravity 
through the penstock 5 to drive the turbine 9 and electrical generator 8. 
Air flows through the air intakes 1, and is added to the flow of surface 
water in the form of small bubbles by the Venturi effect at the air 
induction vortex 3. The amount of air entering the vortex is regulated to 
equal the amount of air being exhausted from the apparatus. Only as much 
air is entrained as necessary to stabilize the water level in the 
separation chamber 15. When the booster pump 10 is running, the air 
induction vortex allows the maximum amount of air to be entrained. The air 
trapped in the falling water is compressed as it is pulled downward by 
gravity through the penstock. The penstock below the turbine has an 
increased diameter to avoid back pressure in the turbine. The flow of 
water and air then enters the cooling tube 11 which spirals down and 
around the outside of the separation chamber 15. Heat flows from the 
warmer water and air in the cooling tube to the ambient ocean water, and 
to the water flowing upward through the upwelling tube 14 located between 
the cooling tube and the outside surface of the separation chamber 15. The 
flow of water and air then enters the separation chamber 15 over a 
separating cone 16. The compressed air in this flow then separates, rises, 
and pressurizes the separation chamber 15. This air has been compressed to 
the same pressure as the ocean depth pressure opposite the separating cone 
16. The water in the separation chamber is essentially at the same 
temperature as the ocean at that depth, only denser because of its higher 
salt content. This water flows out of the lower exhaust manifold 17 
because it is denser than the ambient sea water at that depth. 
The upwelling tube 14 is also used to remove water from the separation 
chamber. When the salinity and temperature gradients are sufficiently 
large, most of the water in the separation chamber will flow out the lower 
exhaust ports 17, with only a minimal flow through the upwelling tube. Due 
to heat exchange between the cooling tube 11 and the upwelling tube 14, 
the flow of water upward through the upwelling tube is gradually warmed, 
resulting in a thermosiphoning effect. The flow through the upwelling tube 
can be accelerated by releasing a jet of air bubbles through orifices 13 
in the upwelling tube, using a portion of the compressed air held in the 
separation chamber. Varying the rate of flow in the upwelling tube 
provides another means of controlling the air pressure and water level in 
the separation chamber. This exhaust system would not be used during 
normal operating conditions. However, should the flow through the lower 
exhaust ports 17 or the upwelling tube 14 slow, pressure would build 
within the separating chamber 15, triggering activation of the valves 
controlling the jet of air bubbles in the upwelling tube. 
Excess compressed air held in the separation chamber can also be used to 
drive a booster pump 10 to increase the flow of sea water and air down the 
penstock 5 and through the turbine 9. Air exhausted by the booster pump, 
as well as any excess compressed air vented from the separation chamber 
are released to the atmosphere through the air exhaust tube 4. 
It will be apparent to those skilled in the art that many variations and 
modifications of the present invention may be made without departing from 
the spirit and scope of the invention.