One Machine for Heating, Cooling, and Domestic Hot Water: Multi-Function Heat Pumps to Enable Zero Net Energy Homes

摘要

The evolution of heat-pump technology promises a revolution for residential energy efficiency. While traditional residential mechanical design uses multiple systems and fuels to provide thermal services, the emerging generation of heat-pump technologies can provide heating, cooling and domestic hot water with a single appliance. These heat pumps operate over a wider temperature range than their predecessors, offer substantial efficiency improvements, and introduce opportunities for waste heat recovery. The domestic hot water heating market is beginning to experience this change as air-source heat-pump water heaters deliver obvious energy savings over electric-resistance water heaters; and (arguably) also beat condensing gasfired systems in terms of source energy consumption and greenhouse gas emissions. However, we anticipate that the current introduction of stand-alone heat-pump water heaters is only the first step in a transition toward multi-function heat-pumps that can replace conventional airconditioners, furnaces, and hot water heaters. The study presented draws from multi-season field measurements of operation and performance for several multi-function heat-pumps. The research assesses the overall efficiency of these systems, and compares the advantages and disadvantages of alternative designs. Our research provides monitored examples of air-source heat pumps, geothermal heat pumps, water-to-water systems, and desuperheaters. We also describe the design of the multi-function heat pump at the core of a zero-net-energy demonstration home designed to generate enough electricity to also power the annual drive cycle of an all-electric sedan. The heat-pump in this home is designed to cover all heating, cooling and domestic hot water needs with no backup.