U.S. Department of Energy - Energy Efficiency and Renewable Energy
Building Technologies Office
Carbon Dioxide-Based Heat Pump Water Heater Research Project
The U.S. Department of Energy is currently conducting research into carbon dioxide (CO2) heat pump water heaters. This project will employ innovative techniques to adapt water heating technology to meet U.S. market requirements, including specifications, cost, and performance targets.
Carbon dioxide is a refrigerant with a global warming potential (GWP) of 1. The CO2 heat pump water heater research seeks to develop an improved life cycle climate performance compared to conventional refrigerants. For example, R134a, another type of refrigerant, has a GWP of 1,300.
This project seeks to develop a CO2-based heat pump water heater (HPWH) designed for the U.S. market that will save at least as much energy as conventional HPWHs while using an environmentally benign refrigerant.
Research is being undertaken through a cooperative research and development agreement (CRADA) between the Department of Energy, Oak Ridge National Laboratory, and a CRADA partner.
The goal of this project is to develop an ENERGY STAR®-qualified CO2 HPWH with low direct global warming potential, and zero ozone depletion potential (ODP).
Benefits and Impacts
Successful development of a CO2 HPWH can improve the market share of HPWH technology. This improvement will be driven by higher efficiencies, the HPWH's ability to operate at lower ambient conditions, and its ability to sustain efficiency and capacity at higher temperature set points compared to other HPWH technologies that use high GWP refrigerants.