Assessment of Demand Response Potential of Heat Pump Water Heaters
This project is a controlled field study and lab test that assessed the demand response (DR) potential of split system and unitary heat pump water heaters (HPWHs) that use carbon dioxide (CO2) refrigerant. The researchers included Washington State University (WSU), Pacific Northwest National Laboratory (PNNL), Efficiency Solutions, and Ecotope working with Cascade Engineering Services.
The controlled field test took place at PNNL’s Lab Homes Test Center in Richland, Washington. The configuration of the Lab Homes allowed simultaneous testing of the water heaters under the same weather, interior temperature, and loads. The tests conducted were: baseline measurement; balancing INC, which tests the response of hourly or sub-hourly changes in demand and the available dispatchable power/energy shift associated with it; and oversupply mitigation, which identifies the total dispatchable power, and resulting energy shift, that a noncritical load like water heating can provide during a 3- to 12-hour window. The Lab Homes tests reveal that both the unitary system and the split system HPWHs could provide water at the required temperature at an aggressive 130 GPD draw, and could perform balancing INC consisting of three 1-hour periods without a loss of delivery performance.
With the PNNL Lab Homes program exploring the extreme ends of the draw spectrum, the draw pattern selected for the lab tests was based on the regional average hot water use of approximately 15 gallons per person per day and with an average home occupancy of three. The goal of the lab tests was to identify the impact of DR on hot water delivery, HPWH performance, the dynamic energy storage potential, and controls needed for optimum DR implementation. The DR benefits revealed by these tests indicate that this is a highly efficient technology that can provide high-capacity storage for oversupply mitigation and can facilitate load balancing – in the same 24 hour period if necessary. This operation increases rather than decreases long-term efficiency.
BPA: Janice Peterson
Washington State University
Pacific Northwest National Laboratory
2013 – 2015