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CO2 Heat Pump Water Heater

CO2 Heat Pump Water Heater Prototype<br />
Credit: Oak Ridge National Lab

CO2 Heat Pump Water Heater Prototype
Credit: Oak Ridge National Lab

Lead Performer: Oak Ridge National Laboratory - Oak Ridge, TN
Partner: General Electric Appliances - Louisville, KY
DOE Funding: $2,147,000
Cost Share: Provided by CRADA partner
Project Term: October 1, 2009 - September 30, 2015

Project Objective

This project is developing a carbon dioxide (CO2) heat pump water heater (HPWH) that meets ENERGY STAR® standards for HPWHs at an installed cost that will enable widespread acceptance in the U.S. residential market. CO2 has low global warming potential when compared to other refrigerants, has zero ozone depletion potential, is very inexpensive, and is not flammable. The project team will demonstrate the performance and energy savings of field ready CO2 HPWH prototypes in ORNL research houses and perform Gate 6 evaluation (passage from engineering development to product demonstration). The project team will then proceed with establishing the performance and cost milestones for commercialization and sales. ORNL, along with the CRADA partner, will design the required field testing protocol including customer feedback and initiate field-testing. Finally, the project team will perform a design optimization of wrap-around gas cooler design to improve system reliability and reduce cost.

Project Impact

With full deployment, ORNL estimates that cost-effective CO2 HPWHs could reduce energy use by 0.8 quads a year; currently, electric water heaters use 1.38 quads annually. Unlike currently available electric heat pump water heaters, a CO2-based system would have minimal GWP. Besides being a very inexpensive fluid, CO2 also has zero ODP and no flammability. Due to the higher temperatures in the transcritical CO2 cycle (compared to subcritical cycles of other refrigerants), CO2 also has greater potential for use in residential/commercial demand response units, as well as for high-temperature commercial water heating applications.


DOE Technology Manager: Tony Bouza
Performer: Kyle Gluesenkamp, Oak Ridge National Laboratory

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