BPA is looking at innovative heat pump system designs for water heating in commercial buildings. Air‐to‐water heat pumps can produce domestic hot water at nearly three times the efficiency than electric resistance systems. They also have a side benefit of cooling and as a result the best applications are in facilities that need both domestic hot water and space cooling. Water-to-water heat pumps can produce domestic hot water with even higher efficiencies (COPs of 5 or 6) than air-to-water heat pumps but they don’t have the added value of space cooling, so care should be taken when planning for best system. In addition, employing a CO2-refrigerant system promises to increase performance over a wide range of temperatures, compared to heat pumps using a standard refrigerant. Unlike residential or small commercial heat pump water heaters (HPWH) don’t have an integrated storage tank and large scale HPWHs are offered only by a few manufacturers, including Colmac and Nyle. Suitable applications include facilities (ie. restaurants, hospitals, dorms, multifamily, etc.) that have total daily domestic hot water consumption of 500 gallons per day or more.
BPA has funded or is currently funding field tests of central heat pumps in buildings where heat from underground garage exhaust systems, refrigeration condensers, mechanical rooms and waste water is used to heat domestic water. We are funding additional research on methods to reduce those distribution system losses.