Analysis of photovoltaic total energy systems for single family residential applications

Abstract

The performance and cost-effectiveness of three photovoltaic total energy system concepts designed to meet the thermal and electrical demands of a typical single family house are compared. The three photovoltaic total energy system concepts considered are: (1) All-photovoltaic systems. Passively air-cooled photovoltaic panels provide electricity to meet both electrical and thermal demands. (2) Separate-panel systems. Solar thermal panels provide thermal energy, while passively air-cooled photovoltaic panels serve the purely electric demand. (3) Combined thermal/electric panel systems. Water-cooled photovoltaic panels provide both thermal energy (transported by cooling water) and electrical energy to meet the separate thermal and electrical demands. Additional passively air-cooled photovoltaic panels are added, as required, to meet the electrical demand. The thermal demand is assumed to consist of the energy required for domestic hot water and space heating, while the electrical demand includes the energy required for baseload power (lights, appliances, etc.) plus air conditioning. An analysis procedure has been developed that permits definition of the panel area, electrical and/or thermal storage capacity, and utility backup energy level that, in combination, provide the lowest annual energy cost to the homeowner for each system concept for specified assumptions about costs and system operations. The procedure appears capable of being used to approximately any size system using solar collectors, as well as in any application where the thermal and/or electrical demand is being provided by solar energy, with utility or other conventional backup. This procedure has been used to provide results for homes located in Phoenix, Arizona, and Madison, Wisconsin, and to evaluate the effects of array and backup power costs and the desirability of selling excess electrical energy back to the utility. (WHK)