Affordable Near- and Medium-Term Solutions for Integration of Low GWP Heat Pumps in Residential Buildings
Develop and Demonstrate next generation heat pumps utilizing low global warming potential refrigerant, achieve high efficiency, and achieve cost savings.
The Regents of the University of California, on behalf of the Davis Campus
Recipient
Davis, CA
Recipient Location
3rd
Senate District
4th
Assembly District
$1,290,091
Amount Spent
Active
Project Status
Project Update
The project completed retrofitting ten demonstration sites with the near-term heat pump solution which uses a lower-cost compressor drive coupled with the low-GWP refrigerant, R-454B. The existing systems were monitored for one year to establish the baseline energy usage for each home followed by a year of post retrofit monitoring. The medium-term solution was focused on improving the performance of air-to-water heat pumps with the potential of safely incorporating ultra-low GWP, natural refrigerants. This project developed advanced microchannel polymer heat exchanger designs to improve heat exchanger performance relative to typical fin-tube type heat exchangers used in hydronic systems. The project team evaluated different manufacturing methods for developing the polymer heat exchanger such as injection molding and 3D printing. A commercial-scale 1.5 Ton heat exchanger was tested in the laboratory and used to validate heat exchanger models for further improving the design. The optimized design showed a 15-20% improvement in heat transfer effectiveness compared to the standard fin-tube design.
The Final Report for this project is now posted, and a follow-on project funded by the CEC EPIC program is planned to further develop the medium-term solution. Future work will continue to explore injection molding manufacturing solutions for the microchannel polymer heat exchanger and develop PCM-based thermal storage for load shifting. The near-term product was ultimately not pursued commercially due to changes in testing requirements for variable-speed heat pumps that penalized the approach used by the novel compressor drive.
The Issue
Next generation heat pump technologies have the potential to significantly reduce greenhouse gas emissions from buildings in California but have had some challenges penetrating the California marketplace, largely due to high initial costs. In order to meet California's aggressive energy and carbon goals it will be necessary to find low-cost solutions for switching the primary fuel for heating buildings from natural gas to electricity while also improving the heating and cooling efficiency of heat pumps.
Project Innovation
This project developed and demonstrated next-generation heat pump technology that achieves high-efficiency heating and cooling, significantly reducing greenhouse gas emissions from buildings, at a lower cost relative to similar performing equipment. The team pursued two pathways, advancing both near- and medium-term solutions. Development of the near-term solution was completed by Rheem Manufacturing Company, and performance verification was conducted by University of California Davis. For the medium-term solution, advancements in heat exchanger design were conducted through modeling and small-scale testing before testing a full-scale heat exchanger coupled to an air-to-water heat pump in the laboratory.
Project Goals
Project Benefits
This project developed and demonstrated next-generation heat pump technology that achieves high-efficiency heating and cooling, significantly reducing greenhouse gas emissions from buildings, at a lower cost relative to similar performing equipment. The team pursued two pathways, advancing both near- and medium-term solutions. Development of the near-term solution was completed by Rheem Manufacturing Company, and performance verification was conducted by University of California Davis. For the medium-term solution, advancements in heat exchanger design were conducted through modeling and small-scale testing before testing a full-scale heat exchanger coupled to an air-to-water heat pump in the laboratory.
Consumer Appeal
Reducing the cost of heat pumps will make them more attractive to customers who have so far largely ignored them due to high upfront costs relative to alternatives.
Affordability
The proposed research will lead to lower costs for heat pumps in the near- and medium-term. This is necessary for greater market uptake.
Environmental Sustainability
A total of 9.2 million therms of natural gas could be offset through increased use of electric heat pumps, and while this would increase the electric demand statewide by 63.7 GWh, the greenhouse gas emissions in California would decrease due to the fuel switching.
Key Project Members
Vinod Narayanan
Curtis Harrington
Felix Villanueva
Subrecipients
TRC Engineers, Inc.
Rheem
Merced County Community Action Agency
Match Partners
Southern California Edison
Regents of the University of California, Davis
