Experimental evaluation of a series solar assisted heat pump system

A series solar assisted heat pump space heating system has been installed in UTK Solar House I on the campus of The University of Tennessee, Knoxville. It is desired to (1) determine the overall thermal performance of such space heating systems and (2) identify solar space heating systems that will interface favorably with electric utilities when the back-up energy source is electricity. The solar system consists of a 675 ft/sup 2/ site built water cooled array, an insulated 1100 gallon thermal storage tank buried just below the ground surface in the crawl space of the house, and heat exchange to the space via forced air distribution system. Heat is supplied to the conditioned space through either the direct solar mode or the use of a field modified air-to-air heat pump in which the heat pump draws heat from the solar system when auxiliary heat is required. The heat pump modification consists of addition of a third (water-to-refrigerant) heat exchanger and control changes. Electric resistance heat is available when the storage tank is below the minimum usable temperature. The system as described operated during the 1979 to 1980 heating season. The overall system performance factor for this period was calculated tomore » be 2.14. The system's maximum peak electric demand was 11.20 kW. During the 1980 to 1981 heating season, the thermal storage system consisted of a 2000 gallon uninsulated steel tank buried seven feet deep in the ground. The overall system performance factor for this period was measured to be 2.81. The system's maximum peak electric demand was only 4.33 kW.« less