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

摘要

Ground source heat pumps show great promise as a means to substantially reduce house energy consumption. Through the use of the soil between 6 and 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 heating and cooling in the range of 4 to 6. Furthermore, generation of domestic hot water is a substantial source of energy consumption in a house. As energy for space heating and cooling decreases, reducing energy for hot water generation becomes the next target. The use of a desuperheater for generating domestic hot water is a potential strategy to reduce this energy consumption by using the heat pump from the space conditioning system to create hot water instead of electric resistance or fossil fuel. However, before widespread implementation can be recommended, it is necessary to understand the magnitude of the impact of the elements that affect the thermal energy output of the desuperheater, such as heat pump runtime. Two unoccupied houses in Pine Mountain, Georgia, were instrumented to document the installed operational space conditioning and water heating efficiency of their ground source heat pump systems. The monitoring period began in January 2010 and continued through April 2011. During this period, interior thermostat setpoints have been maintained at constant values for heating and cooling, and scheduled hot water consumption occurred according to the occupancy profile schedule used in the U.S. Department of Energy's Building America Program. This paper will discuss the 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 of the desuperheater assisted domestic water heating system will be compared to other market available domestic hot water systems.