Lead Performer: Electric Power Research Institute Inc. – Palo Alto, CA
June 20, 2023
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Lead Performer: Electric Power Research Institute Inc. – Palo Alto, CA
Partner: Oak Ridge National Laboratory
DOE Total Funding: $1,800,000
Cost Share: $450,000
Project Term: October 1, 2021– September 30, 2024
Funding Type: Funding Opportunity
Project Objective
In an effort to greatly reduce energy consumption and greenhouse gas emissions from space conditioning equipment, the proposed project aims to integrate a thermoelectric (TE) heat pump with a conventional residential air-to-air heat pump, produce working prototypes that meet target performance, and plan a path for scaling and commercialization of the technology. Two kinds of prototypes will be designed, first through computer simulations, and then developed and tested in the laboratory and the field:
- A refrigerant-to-refrigerant TE heat pump coupled with a conventional space conditioning heat pump to function as a subcooler and recover heat for space heating.
- A water-to-water TE heat pump that operates the same as 1), but using water as the heat transfer medium, with the additional feature of building dehumidifier operation in the cooling season to deliver separate sensible and latent cooling.
Both TE heat pumps will use microchannel heat exchangers on the cold and hot sides to transfer heat. In addition, the TE subcooler will reduce the quality of the refrigerant entering the evaporator, thus achieving a similar effect as a vapor injected compressor to enhance the heating efficiency and capacity at a fraction of the first cost. The first type of prototype will be field-tested in cold as well as moderately cold climates, while the second prototype will be field-tested in a humid climate. The combination of the TE heat pump and a VCS heat pump will deliver superior efficiency, i.e., the overall SEER > 18 and HSPF > 12. It will result in > 10% energy savings in heating mode, with much lower cost than the similar technology of vapor-injection compressor. The cold climate heat pump will work down to -25°C (-13°F) with an integral COP > 2.3. In the case of using the water-to-water TE heat pump as a building dehumidifier in the cooling mode as well as the subcooler in heating mode, it will achieve greater energy savings in both heating and cooling operations. The multifunctional unit will target an annual space conditioning energy reduction of 10%.
Project Impact
The research project described herein aims to develop, demonstrate, measure and verify significant energy savings (>10%) in a heat pump for residences and small commercial buildings by cascading a TE heat pump with a conventional direct expansion air-to-air heat pump, to achieve the benefits of high heating capacity and efficiency at cold outdoor temperatures with lower cost and system simplicity compared to technologies currently being used. The low cost, small footprint system will deliver enhanced heating performance that matches or exceeds a premium vapor-injection compressor. The project will also evaluate the use of the TE heat pump as an add-on device to any residential heat pump (single-speed or modulated capacity) in moderate winter conditions, e.g. 4°C (40°F) to achieve additional energy efficiency and reduce utility peak demand. The installation will be flexible, having minimal first cost increment. The project also aims to demonstrate the applicability of another TE heat pump innovation that will work as a dedicated building dehumidifier in cooling mode, in parallel to a central residential type air conditioner, to facilitate separate sensible and latent load control, and provide better comfort with reduced cyclic ON/OFF efficiency loss. When coupled with a hydronic system, i.e., using water to transport the heating/cooling capacity, it will allow short-term energy storage for peak electric load shifting. These goals will be achieved through computer simulations, full-scale laboratory tests and field verifications.
Contacts
DOE Technology Manager: Payam Delgoshaei
Lead Performer: Sreenidhi Krishnamoorthy