Abstract:
A solar cell floats over a body of saline water. A submerged fresh water collection system underlies the cell. A partial vacuum is created in the solar cell for drawing water vapor from the cell to the collection system. Water vapor is condensed in a condenser disposed between the cell and the collection system. Heat generated by the condensation of water vapor is utilized to heat the salt water, which rises upwardly to replace the salt water vaporized in the cell. The fresh water from the fresh water collection system is routed under the cell such that it becomes thermally enriched. The thermally enriched fresh water is provided to a power generator to improve efficiency.

Description:
TECHNICAL FIELD 
   The present invention relates generally to a solar energy conversion system and more particularly to a solar thermal energy conversion system for power generation. 
   BACKGROUND OF THE INVENTION 
   Solar distillation systems are known that utilize solar energy stored in sea water to assist in the production of fresh water. These systems, however, are generally directed solely at the evaporation of sea water and the subsequent condensation of fresh water. Existing systems, although fulfilling their primary design purpose, often fail to fully utilize the thermal energy trapped within their confines. In many systems, this is a reflection on the inefficiency of design for solar distillation. In other systems, however, this inefficient approach represents a failure of designers to recognize the potential of the stored energy to improve the efficiency of energy generating systems. 
   The concept of utilizing the thermal properties of sea water in an effort to generate energy is not novel in and of itself. Ocean Thermal Energy Conversion (OTEC) systems have been designed to take advantage of the temperature differences between the warmer ocean surface and the colder ocean depths. Existing systems, however, carry with them several disadvantages. In order for significant temperature differences to be utilized, existing systems must often be located (or have access to) offshore and are therefore exposed to the ravages of nature. This contributes significant costs and inefficiencies to these systems and often requires their location at a position distant from the potential users of the generated energy. In addition, the temperature differences typically utilized by such systems are in the magnitude of 35–36 degrees Fahrenheit. This is usually representative of a temperate surface of 77–78 degrees and a chilled depth of 42 degrees. Although considerable effort has been expelled to extract as much energy as possible from this temperature range, the potential is limited. 
   In addition to the thermal inefficiencies, existing OTEC systems often suffer from other disadvantages such as biofouling. Biofouling and scaling often develop when ocean water filled with biomatter is raised to temperatures between 60 degrees and 100 degrees Fahrenheit. This contributes both expense and additional inefficiencies to existing systems. Processes such as reverse osmosis can minimize the effects of biofouling, but contribute their own complexities to the systems. The problem of biofouling can exist for a wide variety of energy generating systems that attempt to utilize sea water as an active ingredient. Thus an approach to energy generation that reduced the impact of biofouling on an energy generation system utilizing sea water would be highly desirable. 
   Accordingly, there is a need for a cost effective energy efficient solar energy generation system that utilizes the potential for solar energy storage in sea water without the representative disadvantages associated with existing systems. In addition, there is a need for a solar energy generation system that utilizes the excess solar energy often ignored by solar distillation advances. 
   SUMMARY OF THE INVENTION 
   The solar thermal energy conversion system of the present invention stores solar energy in water in the form of heat. The system utilizes the accumulated solar generated heat as well as the heat of condensation to increase the temperature of water internally of perimeter insulation surrounding a plurality of integrated solar cells. 
   More specifically, the solar thermal energy conversion system of the present invention comprises multiple solar cells, the number of which is dictated by the required output of the system. The solar cells are designed so that the upper extremities thereof float above the water level. The entire system is insulated from the adjoining body of water and is designed to move up or down with the tide. System position is maintained against change in the direction of water currents and/or wind by mooring cables. 
   The solar energy conversion system of the present invention is different than known systems in many important respects, namely; (a) the system works day and night, during cloudy days and during the cold winter season due to the fact that heat is stored in the system. Temperatures approaching 100° C. are reached in the tipper layers under the cells after four months of operation; (b) the system can work in combination with solar distillation to produce fresh water for use in power generation and/or fresh water supplies; and, (c) the system is designed to produce huge quantities of thermally enriched water for use by power generators. 
   The aforesaid advantages are achieved by: 
   (1) Continuously heating the water to temperatures approaching the boiling point; 
   (2) Condensing water vapor in a collection system deep under the solar cells, for example, 40 feet; 
   (3) Storing heat in massive quantities at temperatures ranging from sea temperature to the boiling point of saline water; 
   (4) Eliminating the requirement for a heating element or condenser coil; 
   (5) Utilizing the heat of solar radiation plus heat of vaporization; and 
   (6) Utilizing humid air above the installation which is drawl into the system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an elevation of the solar thermal energy conversion system of the present invention in its operating environment. 
       FIG. 2  is a view taken within the circle “ 2 ” of  FIG. 1 . 
       FIG. 3  is a cross-sectional view taken within the circle  3  of  FIG. 2 . 
       FIG. 4  is a cross-sectional view taken within the circle  4  of  FIG. 2 . 
       FIG. 5  is a graph showing heat gain in sea water in the disclosed system over time. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   As seen in  FIG. 1 , a solar energy conversion system  8  is provided that utilizes a plurality of interconnected solar cells  10  adapted to float over a body of water  12 . The body of water  12  may represent salt water or fresh water. Additionally, although the body of water  12  is contemplated to encompass any water mass either natural or man-made, the body of water  12  is preferably one located in a position between ±37 latitudes wherein the energy storage potential of the solar energy conversion system  8  can be fully utilized. When the solar thermal energy conversion system  8  is deployed over a body of water  12  that is subject to wave action, a wave breaker  24  may be employed to protect the solar cells  10  from the waves. Suitable cables  26  and anchors  28  position the system  8  relative to the sea bed  30 . 
   As seen in  FIGS. 2 and 4 , each solar cell  10  is made of insulating material, for example, polyurethane foam encapsulated by PVC or the like to preclude attack by salt water. Each cell  10  comprises a pair of cool water return pipes  48  extending downwardly relative to a central pedestal  50 . A pair of side pedestals  52  and  54  are disposed on opposite sides of the central pedestal  50 . The central pedestal  50 , side pedestals  52  and  54 , and base portions  62 ,  64  support a pair of solar energy transparent upper panels  56  and  58  to form an enclosure  59 . The cool water return pipes  48  are connected to the base portions  62  and  64  of a pair of truncated conical funnel like water chambers  70  and  72  on opposite sides of the pedestal  50  which aid in the circulation of water from each cell  10  downwardly through the pipes  48  into the body of water underlying the cell  10 . The base portions  62 ,  64  form a lower panel  65  positioned below the water surface  60 . The solar energy transparent upper panels  56  and  58  and the lower panel  65  are positioned to define an airspace  67  and a cavity  69 . The cavity  69  is filled with a portion of the body of salt water  12 . The airspace  67  and cavity  69  define an inner cell heating zone  71  within the enclosure  59 . This inner cell heating zone  71  serves to capture solar energy and store it within the solar energy conversion system  8 . 
   In operation, when sunlight impinges on the cell  10 , solar energy passes through the glass panels  56  and  58  so as to heat and evaporate the water inside the solar cell  10 . The water vapor is then drawn through passages  80  and  82  in the pedestal  50 , through the water vapor extraction pipes  40  to the condensers  42  due to the reduced pressure therein created by the vacuum pump or source  16 . A pressure differential is maintained between ambient pressure externally of the cells  10  and water vapor pressure internally of the cells  10 . This is accomplished by connecting a vacuum line  14  to each solar cell  10  and to the low pressure side of a vacuum pump or source  16 . In addition, water vapor is drawn through passages  84  and  86  in each of the pedestals  52  and  54  through the water vapor extraction pipes  41  to the condensers  42  along with water that condenses on the lower face of the glass panels  56  and  58 . 
   Each of the solar cells  10  is provided with downwardly extending water vapor extraction pipes  40  and  41  for the conduction of water vapor to a like plurality of condensers  42 . As seen in  FIG. 3 , the condensate output side of each condenser  42  is connected to the vacuum line  14  by conduits  44 . Condensate pipes  46  are also connected to the output side of each condenser  42  and extend downwardly from the vacuum line  14  for connection to the horizontally orientated fresh water extraction conduit  18 . As water vapor moves down the vapor extraction pipes  40  and  41  under the influence of the vacuum pump or source  16 , water continuously condenses in the pipes  40  and  41  as well as in condensers  42 . Fresh or distilled water flows downwardly from the condenser  42  through a water/vapor separator  43  (see  FIG. 3 ), thence through the fresh water conduits  46  and  18  to fresh water storage tanks  20 . A service platform  22  can be orientated over the tanks  20  for the housing of the vacuum pump  16 , fresh water pumps, valves, etc. 
   Heat generated by such condensation warms the water externally of the pipes  40  and  41  and condensers  42  creating an under cell heating zone  73  positioned below the enclosure  59 . The under cell heating zone  73  is generated by transferring the solar energy stored in the inner cell heating zone  71  to a column of sea water  75  positioned below the enclosure  59 . Although this transference has been described by way of condensation, it should be understood that the transference may be accomplished in a variety of fashions. The warmed sea water rises and finds its way through passages  90 ,  92 ,  94  and  96  (vertical salt water replenishment conduits) in the cell  10  thereafter rising to the water surface  60  where it is subjected to solar energy. When surface water in the cells  10  evaporates, the underlying water cools, causing it to sink through the pipes  48 . This relatively cooler water (and saltier in the case of sea water) is replaced by warmer water from under the cell  10  which rises through passages  90 – 96 . Water lost due to evaporation is replaced by the incoming relatively warm water through the passages  90 – 96 . 
   It is to be noted that hot, moist ambient air can be drawn into the cell  10  through passages  100 ,  102 ,  104 ,  106 ,  108  and  110  so as to greatly increase efficiency of the solar cell  10 . As the water vapor is drawn down the vapor extraction pipes  40  and  41  under the influence of the vacuum pump or source  16 , a partial vacuum is created in the enclosure  59  that actively draws the ambient air into the cell  10  through passages  100 ,  102 ,  104 ,  106 ,  108  and  110 . This in effect captures water vapor from surrounding body of water to further improve the efficiency of the present invention. The ambient moist air can retrieve rising heated water losses escaping from under the perimeter heat insulation barrier  120  as well as the vapor from naturally heated surrounding waters. Although the passages  100 ,  102 ,  104 ,  106 ,  108  and  110  may be formed in a variety of configurations, one embodiment contemplates directing the passages  100 ,  102 ,  104 ,  106 ,  108  and  110  at the surface of the portion of the body of water captured in the enclosure  59 . This further helps draw the water vapor off the heated water  12  within the cavity  69  and improves the efficiency of the present invention. 
   As operation continues, heat will build up under the cell  10 , bringing the upper film of water within the system  8  to an elevated temperature that facilitates evaporation of the sea water. Accordingly, it is essential to efficient operation of the system  8 , that heat be retained within the system  8  by a perimeter heat insulator barrier  120  that extends downwardly to a level slightly above the condenser whereby relatively cool sea water surrounds the condensers  42 . In this fashion, the perimeter heat insulation barrier  120  defines the under cell heating zone  73  below the enclosures. The under cell heating zone  73  having only a bottom face  77  open to the body of sea water  12 . The under cell heating zone  73  is comprised of a column of sea water  75  positioned below the enclosure  59 . The insulation barrier  120  surrounds only the sides of the column of sea water  75  while the bottom face  77  is open. The under cell heating zone  73  can store a mass of heated sea water  75 . In the preferred embodiment, the barrier  120  is made of polyurethane or similar material covered with protective material such as PVC Savings. 
   The under cell heating zone  73  can continuously increase in temperature when the solar energy conversion system  8  is utilized in warmer climates. In fact, it is contemplated that the present invention can be employed such that the entire column of sea water  75  positioned under the enclosure  59  can reach the boiling point of water (or salt water as the case may be). In approximately 9 months after the start of operation the column of water  75  can reach this condition.  FIG. 5  illustrates the temperature of the column of water  75  over a period of nine months. Without use, the thermally charged water within the solar cell  10  would begin to spill out under the perimeter heat insulation barrier  120  and dissipated into the surrounding waters. The advantage of this system  8  is that this large quantity of highly solar charged water is directed towards a power generator  200  to generate electricity. It should be recognized that the solar energy stored in the column of water  75  need not represent the sole source of energy for feeding the power generator  200  but may simply be utilizing to impact the efficiency of the power generator  200 . 
   Power generators  200  are known to come in a wide variety of forms and configurations. It is known, however, that whether such generators comprise steam turbines or ocean thermal energy conversion generators, many of these designs rely on heated water as a source of power to generate electricity. The present system creates significant inroads to such power generating systems by harnessing and trapping solar energy for use in these systems. Often power generators  200  may be sensitive to the content of water used to generate electricity. Biofouling or contamination may result in damage to the power generator  200  or a loss of efficiency. An embodiment of the present invention addresses this by including a fresh water heat exchanger  210  in communication with the fresh water conduit  18 . Although the fresh water heat exchanger  210  may be placed in communication with the fresh water conduit  18  in a variety of fashions, one embodiment contemplates the communication taking place via the at least one fresh water storage tank  20  as illustrated in  FIG. 1 . In this fashion the fresh water heat exchanger  210  can draw a continuous flow from the stored fresh water. 
   The fresh water heat exchanger  210  is positioned within the solar cell  10  such that fresh water passing through the fresh water heat exchanger  210  is thermally enriched as it passes through the fresh water heat exchanger  210 . The fresh water heat exchanger  210  preferably passes through the column of water  75  that has become superheated due to solar energy. A variety of heat exchangers may be utilized to facilitate the transference of the solar energy stored in the column of water  75  into the fresh water. Although the fresh water heat exchanger  210  is illustrated positioned within the column of water  75 , ill other embodiments it is contemplated that it may be positioned in other locations within the solar cell  10 . The fresh water heat exchanger  210  is contemplated to be in communication with the power generator  200  such that a supply of thermally enriched distilled water can be supplied to the power generator  200 . This can be utilized to significantly improve the efficiency of the power generator  200 . 
   It is recognized that not all power generators  200  or bodies of water  12  need or benefit from the use of a fresh water heat exchanger  210 . In such circumstances, the present invention contemplates the use of a heated water supply conduit  220  in communication with the under cell heating zone  73 . In one embodiment, the heated water supply conduit  220  may simply conduct the thermally enriched water  270  from the fresh water heat exchanger  210  to the power generator  200 . In an embodiment wherein such fresh water usage is not beneficial, however, the heated water supply conduit  220  may conduct the thermally enriched water  270  directly from portions of the heated column of water  75 . In such cases where the heated water supply conduit  220  directly transfers salt water, the power generator  200  output may additionally include distilled water  230  which further improves the benefits of the present system and a water discharge  235 . In either case, the heated water supply conduit  220  is preferably insulated in areas outside of the under cell heating zone  73  to protect the integrity of the thermally enriched water  270 . 
   In a unique embodiment of the present invention illustrated in  FIG. 1 , it is contemplated that the power generator  200  comprises an ocean thermal energy conversion generator  240 . The OTEC generator  240  further includes a cold water conduit  250  in communication with the power generator. The cold water conduit  250  communicates chilled sea water  260  to the OTEC generator  240 . The OTEC generator  240  in turn utilizes the chilled sea water  260  in combination with the thermally enriched water  270  provided by the heated water supply conduit  220  to generate electricity. 
   Commonly OTEC generators  240  require pipes from significant ocean depths to deliver chilled sea water  260 . Even when these mechanical difficulties are hurdled, the temperature differential between the hot and cold waters in existing OTEC assemblies limits their potential. The present invention directly removes these limitations. The thermally enriched water  270  from the present invention is contemplated to approach 100 degrees Celsius (212 Fahrenheit). With this level of temperature on the hot side, the chilled sea water  260  need only be drawn from any reasonable depth (such as 60 feet deep) wherein the temperature is slightly chilled (15 degrees C. 59 degrees Fahrenheit). These temperature differences, therefore, of the present invention (upwards of 85 degrees C., 153 degrees Fahrenheit) will provide a differential vapor pressure significantly more that of present OTEC systems and a differential vapor weight well in excess of existing designs. This dramatically improves the efficiency of the OTEC generator  240  while simultaneously reducing the mechanical constraints of existing systems wherein the plant must be positioned significantly offshore. The energy utilized to generate a vacuum in an OTEC system can be significantly reduced simultaneously with the increase in power generation resultant from vapor pressure differences. Additionally, the extreme temperatures of the thermally enriched water  270  are known to reduce biofouling which is most prevalent between temperatures of 15 and 35 degrees Celsius. Thus fewer deposits are present in the presented energy conversion system  8  as compared to prior systems. This eliminates the need for filtering systems such as reverse osmosis filters that add cost to existing energy conversion systems. 
   While particular embodiments of the invention have been shown and described, numerous variations and alternative embodiments will occur to those skilled in the arm. Accordingly, it is intended that the invention be limited only in terms of the appended claims.