Lab and field demonstration of a multifunction AWHP with thermal energy storage.
Status: Current
Funding Sources: California Energy Commission In-kind Support by Harvest Thermal and Midea
Project Objective
The primary goal of this work is to develop a new product: an ultra-low global warming potential air-to-water heat pump (AWHP) integrated with thermal energy storage (TES) to provide domestic hot water (DHW) and space heating and cooling while efficiently enabling demand flexibility in residential buildings at lower cost than leading alternatives.
Significance to Industry
The increasing share of intermittent renewable energy sources on the grid is driving a need for efficient, grid-interactive buildings and appliances. There is a need for residential utility customers to participate in demand-side management strategies to mitigate critical grid conditions, reduce electricity and grid system costs, and decrease both direct and indirect greenhouse gas (GHG) emissions. A key challenge lies in creating scalable solutions that are cost-effective, energy-efficient, reliable, and safe for residential buildings.
This work proposes to develop a multifunction air-to-water heat pump (AWHP) integrated with low-cost sensible thermal energy storage (TES). This solution promises to be more energy-efficient and cost-effective than both typical and leading solutions to provide domestic hot water (DHW) and space conditioning in residential buildings. The integrated system can enable electricity rate payers to automatically shift equipment operation to periods with lower electricity prices and carbon emissions. Furthermore, the multifunction AHWP can also avoid costs for electrical panel upgrades often associated with electrification projects.
Research Approach
Harvest Thermal, a project team member, has an existing TES platform that currently uses a single-pass CO2 (R-744) refrigerant AWHP for both space heating and DHW, but that does not provide cooling. These heat pumps are relatively expensive due to very high-pressure requirements for CO2 as a refrigerant. This platform will be reconfigured to use a lower first-cost, multi-pass R-290 refrigerant AWHP that will also provide space cooling. The team will work with Midea, a manufacturer and CBE industry partner, to modify their monobloc Thermal Arctic HT series AWHP, newly available on the international market, to be deployable in the USA and complete the integration with Harvest.
The study AWHP will utilize R-290 (propane) a natural refrigerant with an ultra-low global warming potential that has an A3 (highly flammable) classification but that is now widely used in Europe and Asia. The team will measure performance in full-scale laboratory testing in PG&E’s newly A3-compliant test facility over a range of representative design and typical climate and grid conditions in California. To prepare for the demonstration, the team will also deploy the system in a building at UC Berkeley’s Richmond Field Station, which allows for controllable loading while being representative of typical residential settings. Finally, the team will demonstrate the final prototype system in a Berkeley home to demonstrate safety, performance, low initial costs, and demand flexibility capabilities in a real residential setting. We will also measure the energy, emissions, and cost improvements compared to the existing gas-fired appliances.
In conjunction with these activities, the team will conduct interviews and prepare technical and/or policy briefs to facilitate permitting of systems using an A3 refrigerant. Last, we will use building energy simulation (EnergyPlus) to extend evaluation of the system over the full range of design, climate and grid conditions spanned by the California residential building stock. Through these combined activities, we will compare the proposed system to common systems in existing homes (tank or tankless gas-fired DHW with independent gas furnace), a common electrification pathway for existing homes and all-electric new construction (heat pump water heater and independent air-to-air heat pump), and current market leading technologies (combined space heating and DHW system, e.g., Harvest Thermal’s current design).