Applications of Commercial Heat Pump Water Heaters in Hot, Humid Climates

Abstract

Heat pump water heaters can provide high-efficiency water heating and supplemental space cooling and dehumidification in commercial buildings throughout the United States. They are particularly attractive in hot, humid areas where cooling loads are high and the cooling season is long. Because commercial kitchens and laundry facilities have simultaneous water heating and cooling needs, they are excellent applications for heat pump water heaters. Typical heat pump water heaters (HPWHs) operate at an annual coefficient of performance (COP) of approximately 3.0 for water heating alone. Space conditioning benefits of about 0.67 Btu are delivered at no additional cost for each Btu of water heating output. In situations in which this cooling output is valued, the dual thermal outputs for heating and cooling make heat pump water heaters particularly attractive. The comfort value of added cooling in overheated facilities and the resulting increase in employee and customer satisfaction are frequently cited as additional benefits. This paper describes currently available heat pump water heating equipment and offers guidelines for successful applications in commercial facilities. The results of field test programs involving more than 100 units in Alabama, Georgia, Mississippi, Tennessee, South Carolina, and other areas are incorporated. Initial conclusions are drawn from a reliability database, and interviews with utility applications specialists and manufacturers are discussed. Design tools are reviewed, including a new comprehensive computer simulation model. Emphasis is placed on identifying sound candidates for installations and on application and design considerations. A brief survey is provided of environmental implications of heat pump water heaters and new developments in heat pump water heater equipment.