Problem Statement: Water heating is the second largest source of energy use and greenhouse gas emissions in residential buildings. Heat pump water heaters, integrated with phase-change material based thermal energy storage, provide a great potential to reduce water heater energy use, greenhouse gas emission, and negative impact on the electric grid. However, there is a lack of control technologies to enable grid-interactive control of phase-change material based thermal energy storage to improve heat pump water heaters performance according to time-varying electricity supply conditions, such as electricity price, electricity supply carbon intensity, and demand response signals. Proposed Solution: This proposal will develop an advanced control technology to support integration of heat pump water heaters with phase-change material based thermal energy storage. This advanced control will automatically determine an optimal system operation sequence of charging and discharging thermal energy storage according to time-varying building hot water demand projection, the state of charge of the thermal energy storage and electricity supply conditions. Phase I Project Activities: This project will first develop a system design solution to integrate phasechange material based thermal energy storage with a heat pump water heater for providing hot water in multifamily buildings. The project will build a prototype system according to the design solution. Second, the project will develop a controller, including detailed control algorithms and a method to assess the state of charge of phase-change material based thermal energy storage. Last, the project will perform preliminary laboratory tests of the prototype system and controller to verify their capability of achieving grid-interactive operation. Commercial Applications and Other
Benefits: Both residential and commercial buildings can greatly benefit from the integration of heat pump water heaters with phase-change material based thermal energy storage using a grid-interactive control technology. In addition to supporting domestic hot water services, this integrated solution can also be used in building space heating and cooling applications, which will be explored in the future phases of the project.
