Developing operational strategies for the Fort Benning shallow solar pond domestic water heating system. Performance testing and results.

摘要

Performance tests were conducted on six of the eighty individual solar ponds that comprise the Fort Benning Shallow Solar Pond Domestic Water Heating System. The system was originally designed to operate at a 3-inch pond fill and provide 500,000 gallons of heated water daily to a laundry and barracks buildings. Since construction, hot water needs from the system have decreased approximately 50% and the original operating strategy was no longer thought to be optimum for current conditions. New operating strategies were tested that could potentially improve system performance. Specifically, these involved varying pond fill levels from 2 to 4 inches and exposure periods from 1 to 3 days. Lower pond fills were found to increase final water temperatures for all exposures. At a 1-day exposure, lowering pond fill from 3 to 2 inches increased pond performance (Btu/gal) by 30%. A larger reduction from 4 to 2 inches produced an approximate 62% increase. With hot water demand on the Fort Benning system well below capacity, lowering pond fill is an excellent option for an immediate and significant performance improvement. Although increasing exposure increased final water temperatures in all but one test case, lowering pond fill was more productive. An individual pond operating at a 3-inch fill and a 1-day exposure collects around 488 MBtu annually which is equivalent to around $4500 in avoided fuel costs. With excess capacity, only the water utilized is saving energy. Therefore, the key operating objective for Fort Benning is to add the most energy possible to the water that is used. Pond fills at Fort Benning should be reduced to 2 inches and exposures should remain at 1 day (unless more ponds are activated). This should provide an immediate increase in pond performance of approximately 30%. 5 refs., 27 figs., 4 tabs.