Dynamic positioning of sea thermal power plants by jet propulsion

A sea thermal power plant is provided with pumps of the propeller type for bringing up cold water and forcing it through suitable condensers or heat exchangers and for drawing a continuous flow of warm water from a surface layer of the sea and forcing it down through suitable heat exchangers or boilers of the plant. The water so drawn from the sea flows through the heat exchangers and is subsequently discharged therefrom, which action creates thrust thereby producing forces to move the plant over the water surface. The heat exchangers are provided with deflectors which control the direction of discharge to produce a reaction force in any desired direction to drive the power plant. The pumps have associated therewith pipes which have located therein, downstream of the pumps, bypass louvres or vanes which can be opened to discharge water directly into the sea to produce a higher thrust for moving or positioning the power plant.

BACKGROUND OF THE INVENTION 
In a sea thermal power plant, it is important to be able to move the plant 
at a slow rate of speed over the surface of the water while producing 
power, or alternatively to be able to maintain the plant in a fixed 
position despite the drag forces created by winds and currents. The warm 
water from the surface layer of the sea is drawn into the plant by 
suitable pumps and directed through heat exchangers or evaporators and 
after giving up some heat, to boil a power producing fluid, it is rejected 
from the plant. Since warm water has been removed from the surface of the 
sea, it must be replaced by water from underneath the surface and the 
surface water is then slightly cooler than before. Thus, in order to have 
available a continuous supply of warm water, that can be drawn into the 
plant, it is necessary that the plant be moved about the surface of the 
sea. 
In order to effectively move the power plant, it has been proposed to 
employ adjustable deflectors which would permit directing the thrust of 
the water rejected from the heat exchangers so as to produce thrust in any 
desired direction, thereby producing forces to move the plant or to 
position the plant with respect to the currents of the sea. While a system 
of this type permits thrust to be produced and directed in such a way as 
to position a plant, it is questionable whether enough thrust can be 
produced to overcome the drag forces produced by wind and currents under 
high storm conditions. Therefore, it becomes important to have a thrust 
means available, which can produce higher thrust during times when storms 
may occur. 
SUMMARY OF THE INVENTION 
The present invention is directed to the pumps of a sea thermal power plant 
and the equipment associated therewith for producing higher thrusts under 
abnormal conditions. The power plant is provided with pumps that draw the 
warmer surface water therethrough and direct same through evaporators or 
heat exchangers from whence it flows through suitable deflectors or guide 
means back into the sea. In addition, the power plant is provided with a 
pump that draws cooler water from the lower depths of the sea and delivers 
same to a heat exchanger or condenser from where it is directed by 
suitable deflectors or guide means back into the sea. Under normal 
conditions the water directed back into the sea from the pumps provides 
sufficient thrust to move the power plant over the surface of the sea. 
In order to produce higher thrust forces, so as to overcome the drag forces 
produced by wind and currents under high storm conditions, it is necessary 
to provide additional thrust openings in the portion of the pipes 
downstream from the various pumps. This is accomplished by utilizing vanes 
or louvres which, while normally maintained in a closed position, are 
capable of being opened for discharging the greater portion of the water 
from the pipes directly into the sea with the remaining portion of the 
water flowing through the heat exchangers and then into the sea. The 
pivotally mounted vanes or bypass thrust openings can be installed below 
the pumps on the pipes delivering the warm water from the surface of the 
sea and on the pipe above the pump bringing cold water up from deep in the 
sea. Thus, all of the pumps can contribute in producing higher thrust when 
it is required.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
There is shown in FIG. 1 a segment of sea thermal power plant embodying an 
equipment deck 10 having associated therewith inlet screens 12 which 
permit the warm surface water of the sea to flow into the inlet pipes 14. 
The pipes are provided with axial flow propeller pumps 16, shown in dotted 
outline in FIG. 1, with said pipes terminating in evaporators or heat 
exchangers 18. The warm surface water discharged from the pipes 14 flows 
through or between the tubes or plates of the heat exchanger 18 giving up 
heat to the fluid in said tubes or plates after which the water is 
rejected from the evaporator or heat exchanger. The heat exchanger 18 is 
provided with adjustable louvres or deflectors 20 which can be arranged to 
direct the rejected water from the heat exchanger so as to produce a 
thrust. The thrust so derived can be directed by the deflectors in any 
desired direction. Thus, by directing the flow of water as it discharges 
from the evaporator or heat exchanger in a direction backward or rearward 
to the path of movement of the power plant a reaction force is produced so 
as to drive the power plant forward through the water. It should be borne 
in mind that the water entering the pipes 14 from the surface of the sea 
is drawn in under the action of the pumps 16 and is forced through the 
heat exchangers or evaporators by said pumps so that the water moves out 
of the evaporators or heat exchangers at some velocity due to the pump 
action. Since there is a large quantity of water flowing through the heat 
exchangers 18 under the action of the pumps 16, the water rejected from 
the heat exchangers will be flowing at considerable velocity. Thus, the 
velocity of the water leaving the heat exchangers may be higher than the 
desired velocity of the moving power plant and if this is the situation, 
then the louvres or deflectors 20 can be adjusted to control the direction 
in which the rejected water is being directed. In this manner, the angular 
relation or positioning of the louvres or deflectors 20 will tend to 
control, to a degree, the forward velocity of the power plant through the 
sea water. 
The power plant is provided with a depending cold water pipe 22 which has 
positioned therein an axial flow propeller pump 24 of the same general 
type as the pumps 16 in the pipes 14. The cold water pipe 22 terminates in 
a condenser or heat exchanger 26. The condenser or heat exchanger 26 
utilizes the cooler water from the cold water pump 24 to liquify a 
vaporized working fluid and like the heat exchangers 18 is provided with 
louvres or deflectors 28, FIG. 3, for directing the water discharged or 
rejected from the heat exchanger so as to produce a reaction force in the 
same manner and for the same purpose as the water discharged from the 
evaporators 18. Thus, the adjustable louvres 20 and 28 carried by the heat 
exchangers 18 and 26 permit directing the thrust from the heat exchangers 
in such a way as to produce thrust in any desired direction thereby 
producing forces to move the power plant or to position said plant with 
respect to ocean currents as so desired. 
The pumps 24 and 16 are utilized respectively, to bring up cold water and 
force it through the condenser or heat exchanger and to pump warm water 
from the surface inlet down through the boilers or heat exchangers of the 
power plant. In order to provide for a greater thrust from the power plant 
so as to overcome the drag forces produced by wind and currents under high 
storm conditions, the pipes 22 and 14, downstream from the pumps 24 and 
16, are formed with louvres or bypass thrust openings. In this manner, 
when high thrust is desired for the power plant, the louvres or vanes or 
thrust openings in the pipes 22 and 14 are opened so that water can be 
discharged directly from the pipes into the sea at the same time that some 
of the water continues to flow through the heat exchangers and into the 
sea. The pipes 14 and 22 are each provided with segments or sections 30, 
FIG. 4, that have louvres or bypass thrust openings in the form of 
pivotally mounted vanes 32 which can be opened to the full line position 
of FIG. 4 for discharging the greater portion of the water flowing through 
the pipe directly from the pipe into the sea, while the remaining portion 
of the water continues to flow through the respective heat exchangers 18 
and 26. As a result of the foregoing arrangement, all of the pumps 16 and 
24 can assist in producing higher thrust when it becomes necessary during 
such times when storms may occur. The vanes 32 may be actuated by any 
suitable means, not shown, for moving from the full line open position to 
the dotted line closed position or any intermediate position. During 
normal operation of the sea thermal power plant, the vanes 32 are moved to 
the dotted lined closed position of FIG. 4 so that all of the water 
flowing through the pipes 14 and 22 will be discharged into the sea 
through the respective heat exchangers 18 and 26. 
In order to produce the higher thrust, a considerably higher flow through 
the pumps would be required than would be the case at normal operating 
conditions. Referring to FIG. 6, the head versus capacity and efficiency 
versus capacity are plotted for a typical propeller pump at 270 RPM. The 
peak efficiency curve occurs at 180,000 GPM where the pump operates at 87 
percent efficiency; the head produced at this flow is 17 ft. In a 
propeller pump, the head produced is directly proportional to the square 
of the speed and the flow is directly proportional to the speed. 
Therefore, operating curves can be shown in FIG. 7 derived from the curves 
of FIG. 6 with the operating curves of FIG. 7 showing the head versus 
capacity and horse power required versus capacity at the varying speeds 
from 200 to 400 RPM. The operating point at peak efficiency is shown in 
FIG. 7, where, for example, at 200 RPM the pump would deliver 295 cu. 
ft./sec. at a head of 9.3 ft. and would require 380 hp. If the pump were 
to be operated at 400 RPM, it would deliver at the same peak efficiency 
condition 593 cu. ft./sec. at a head of 37.3 ft. and would require 2900 
hp. The peak efficiency line can normally also represent the 
characteristic curve of frictional resistance to pump the water through 
the pipes 14 and 22 and the heat exchangers 18 and 26. Thus, if normal 
operation occurs at 200 RPM and the normal flow against the resistance of 
friction in the heat exchangers and pipes is such that the pump would 
deliver 295 cu. ft./sec., as shown at this peak efficiency point, then, if 
the pumps speed were increased to 400 RPM, it would then deliver 595 cu. 
ft./sec. at a resistance head of 37.3 ft. and would require 2900 HP. Thus, 
if one wanted to double the flow through the heat exchangers, thereby 
producing more thrust, it would require 2900 hp. as compared to only 380 
hp. at normal operating conditions. It, therefore, becomes rather 
difficult and undesirable to try to speed up the pumps with operating 
flows going through the heat exchangers to develop high thrusts during 
storm conditions. 
Instead of trying to speed up the pump and use excessive power to obtain 
more flow through the heat exchangers, the bypass louvres or vanes 32 are 
opened, by any suitable means, to the full line position of FIG. 4 so that 
the resistance to flow is reduced and it is possible to pass considerably 
more flow through the system at a much lower head. For example, if one 
wanted to maintain the same essential pressure drop across the heat 
exchangers or the same total head as the system was operating on normally, 
then one could make the bypass area, as defined by the louvres 32, large 
enough so that the combined resistance curve of the bypass and the heat 
exchangers would be as shown in dotted lines in FIG. 7 and marked "bypass 
open". This resistance line intersects the 400 RPM head line at 9.5 ft. 
head and under these conditions, the flow would then be 725 cu. ft./sec. 
or 2.46 times as much as the flow under normal operating conditions. At 
the 400 RPM and the head of 9.5 ft., the pump would require 1300 hp. This 
means that a much higher flow would be generated per unit of horse power 
at the conditions with the bypass louvres 32 open so that more thrust 
could be generated and thus be available for emergency conditions such as 
when storms may occur. 
There is shown in FIG. 5 a sectional view through a propeller pump 16 or 24 
which might be used in the pipes 14 and 22. The axial pump 16 or 24 is 
provided with a suitable casing or housing 34 that is formed with an inlet 
36 which is provided with vanes 38 which can adjustably direct the flow of 
water into the propeller blade 40. The pump is normally required to rotate 
at a very low speed while the desirable speeds for the turbines are much 
higher. Thus, the pump 16 or 24 is shown with a two-stage step-down gear 
arrangement permitting the turbines to run at a much higher rotating speed 
than the pump propeller. In this connection, a propeller shaft 42 is 
supported in suitable bearings and carries a gear 44 that meshes with a 
pinion gear carried by a shaft 48 that is supported in suitable bearings. 
The shaft 48 also has mounted thereon a gear 50 that meets with a gear 52 
carried by a shaft 54. 
In order to provide for the excessive power that is required when storm 
conditions occur and high thrust is required, the shaft 54 has mounted 
thereon a main turbine 56 and an auxiliary turbine 58 which are arranged 
in vertical spaced relation to one another. The main turbine 56 would 
drive the pump propeller 40 under normal operating conditions while the 
auxiliary turbine 58 would be placed into service to increase the power 
during the time when high thrust is required. In this connection, the 
auxiliary turbine 58 is considerably smaller in diameter at the turbine 
wheel 60 than is the turbine wheel 62 for the main turbine 56. This 
permits the velocity of the turbine wheel 60 at a higher RPM to operate 
more efficiently so that the turbine 58 can operate at a good efficiency 
when the speed is in excess of the normal speed of the turbine 56. It is 
to be noted, however, that the main turbine 56 is larger in diameter so 
that its tip is in the range of high efficiency during the slower speed 
for normal operation. Furthermore, the turbine 58 is disclosed as having a 
wider wheel 60 and, therefore, larger flow capacity in order to supply the 
large increase in horse power required for operating at the high speed 
when high thrust is required. 
Thus, the sea thermal power plant is capable of producing thrust by 
controlling the direction of the water rejected from the heat exchangers 
as a result of the use of the louvres or deflectors 20 and 28 in 
conjunction with the heat exchangers 18 and 26. Under normal conditions 
the louvres or deflectors 20 and 28 would enable the power plant to move 
through the surface of the water under the force derived from the water 
being ejected from the heat exchangers through the louvres or deflectors. 
The thrust so produced would permit the power plant to be moved or 
positioned with respect to ocean currents as desired. In situations 
wherein it would be desirable to produce higher thrust, such as times 
during storms or the like, the vanes or bypass louvres 32 in the pipes 14 
and 22 would be opened so that the greater portion of the water flowing 
through the pipes 14 and 26 would be discharged directly into the sea 
thereby providing greater thrust while at the same time a portion of the 
water flowing through the pipes 14 and 22 would continue to flow through 
the heat exchangers and against and through the louvres or deflectors 20 
and 28. In addition, during the periods when higher thrust is required, 
the pumps would be driven by both the main and auxiliary turbines to 
increase the power of said pumps when storm conditions occur and high 
thrust is required. 
Although the foregoing description is necessarily of a detailed character, 
in order that the invention may be completely set forth, it is to be 
understood that the specific terminology is not intended to be restrictive 
or confining, and that various rearrangements or parts and modifications 
of detail may be resorted to without departing from the scope or spirit of 
the invention as herein claimed.