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<br /> <br />W <br />"-l <br />en <br />~ <br /> <br />exchange desalting process. Conversion to electrical energy would allow <br />membrane processes such as RO (reverse osmoSis) or electrodialysis to be <br />considered for integration with solar ponds. <br /> <br />Current projects planned, which will utilize the power generation tech- <br />nology, include the Dead Sea Project in Israel and the Salton Sea <br />Project (5 MWe scheduled for 1984 and ultimately 500 to 600 MWe). <br />Companies in both the United States and Israel manufacture the organic <br />Rankin power conversion equipment needed for the solar pond powerplant. <br />Low cost and reliable electric power for the baseload and intermediate <br />load applications could be produced from this technology. <br /> <br />A nonconvecting solar pond is a shallow body of saline water, generally <br />between 6.5 and 16 feet deep, that functions similarly to a flat plate <br />solar collector. The pond is constructed in three distinct layers: <br />at the surface, a relatively narrow layer of freshwater or dilute brine <br />in which there are vertical convection currents due to wind and evapora- <br />tion; an intermediate, stable salt concentration gradient increasing <br />with depth to about 20 weight percent; and a bottom concentrated storage <br />layer. The concentration gradient acts as an insulator by inhibiting <br />convective heat losses from the storage zone. With convection sup- <br />pressed, incident solar radiation absorbed throughout the storage layer <br />and pond bottom is trapped enabling storage temperatures to increase. <br />Energy can then be extracted from the pond by recycling the hot storage <br />layer brine through a heat exchanger as depicted in figure 10. Typi- <br />cally, pond storage temperatures range between 160 and 200 'F and pond <br />thermal conversion efficiencies from 15 to 25 percent, <br /> <br />CONOENSER <br /> <br /> <br /> <br />,,' ,"''o) <br /> <br />" <br />", <br />, COLD WATER I':::, <br /> <br />,':j< <br /> <br />"",,:,::::,:::~,:, ,,',',', <br /> <br />GENERATOR <br /> <br />t <br /> <br />\\~ <br />\ \ \' "" <br /> <br />PUMP <br /> <br />:...;.;:::.:.:.:.......'...... <br />E~APORATlON (BOILER) <br /> <br />-'" <br />....,;:.... . .,'.. ;." -' ..~:..,.'.'.' '.'" ....: '0";', : '. '. '". . <br /> <br />" .', <br /> <br />Figure 10. - Solar pond generating concept, <br /> <br />I V - 26 <br />