Swimming Pools as Heat Sinks for Air Conditioners

Using swimming pools as heat sinks for air conditioner waste heat has been estimated to reduce air conditioner energy use in California by 25-30% (Harrington and Modera, 2012). There are two primary advantages of rejecting waste heat to an air conditioner instead of ambient air: 1) swimming pool temperatures are colder than ambient air during peak cooling periods, and 2) water is a superior heat transfer medium than air resulting in better heat exchange performance. These both result in lowering compressor head pressures and associated energy use. This process also has the added benefit of providing “free” pool heating which would increase the benefits to consumers and spur market adoption. A retrofit technology has been identified for adapting an existing air conditioner to allow heat rejection to a swimming pool, but no independent evaluation of the technology exists. The technology allows a maximum pool temperature to be set by the user, and will switch between the existing air-source condenser and the water-source condenser depending on the heating needs of the pool. The higher the pool setpoint temperature the more heat that is rejected to the pool versus ambient air and the higher the energy saving potential. This project would perform 2-3 retrofit installations of this technology to evaluate the impact on air conditioner energy use, and develop recommendations for control setpoints that lead to higher energy savings results. The results will be combined with an existing pool thermal model to develop a tool for evaluating potential savings using inputs such as: pool volume, average depth, shading, air conditioner capacity and efficiency, climate zone, and pool temperature setpoint.