CH-12-C006 -- Residential Ground Source Heat Pumps with Integrated Domestic Hot Water Generation: Performance Results from Long-Term Monitoring PDF

Ground source heat pumps show great promise as a means to substantially reduce house energy consumption. Through the use of the soil between 6and 600 feet below the surface of the earth as the thermal energy source or sink, it is possible to obtain design coefficients of performance for heatingand cooling in the range of 4 to 6. Furthermore, generation of domestic hot water is a substantial source of energy consumption in a house. Asenergy for space heating and cooling decreases, reducing energy for hot water generation becomes the next target. The use of a desuperheater forgenerating domestic hot water is a potential strategy to reduce this energy consumption by using the heat pump from the space conditioning system tocreate hot water instead of electric resistance or fossil fuel. However, before widespread implementation can be recommended, it is necessary tounderstand the magnitude of the impact of the elements that affect the thermal energy output of the desuperheater, such as heat pump runtime. Twounoccupied houses in Pine Mountain, Georgia, were instrumented to document the installed operational space conditioning and water heatingefficiency of their ground source heat pump systems. The monitoring period began in January 2010 and continued through April 2011. Duringthis period, interior thermostat setpoints have been maintained at constant values for heating and cooling, and scheduled hot water consumptionoccurred according to the occupancy profile schedule used in the U.S. Department of Energy's Building America Program. This paper will discussthe instrumentation methods and field operation characteristics of the two ground source heat pumps, including a comparison to the manufacturers'listed values of the coefficient of performance calculated from field measured data for the two ground source heat pumps. The measured efficiency ofthe desuperheater assisted domestic water heating system will be compared to other market available domestic hot water systems.