Demand flexibility characterisation of heat pump water heater system

The demand flexibility of a residential heat pump water heater system was experimentally characterised. The heat pump water heater system was installed and instrumented with power, temperature and flow sensors. Two scenarios were considered: baseline or normal operation and load decrease (load shifting) which tested the heat pump’s ability to reduce power demand in response to a request for demand flexibility. Demand flexibility is quantified in terms of the following parameters: capacity, electrical energy storage, round trip efficiency, heat storage, activation time delay, response duration, minimum time between events, and cycle duration. In the load decrease scenario, the demand flexibility capacity was found to be 0.27 to 0.32 kW over a response duration of 47-51 mins. The average electrical energy storage, round trip efficiency and heat storage were $0.25 \mathrm{kWh}, 91 \%$ and 11.1 kWh respectively. The average activation time delay, cycle duration, and minimum time between events were 258, 317, and 269 minutes respectively. These results may be useful for evaluating demand flexibility potential from heat pump water heater systems.