Aggregated Generic Load Curve for Residential Electric Water Heaters

Advanced control techniques may be used to regulate the operation of residential appliances to establish a virtual power plant. The electric water heater may be regarded as a 'uni-directional battery' and a major component of a hybrid residential energy storage system. One of the main constraints of implementing demand response with EWH relates to the unpredictable customer behavior, which influences the domestic water tank temperature as well as the EWH operation cycle. This study analyzes the operation of multiple water heaters and develops an aggregated generic water heater load curve for the average residential customer based on experimental data retrieved from the A.O. Smith Corporation. An equivalent thermal model capable of capturing the typical customer behavior and estimating the per unit hot water usage was developed. The proposed aggregated generic EWH load curve was validated through an example demand response program, in which the morning peak demand is shed in order to store the surplus PV power at midday in the EWH. Based on the representative hot water draw profile and the electric power profile, the change in average tank temperature was estimated and maintained within the customer acceptable range.