Feasibility of Grid Flexibility Provision Using Heat Pump Water Heaters Under Midnight Power Services: A Case of South Korea

Sector coupling (SC) has recently emerged as a solution to alleviate the curtailment caused by surplus power from variable renewable energy sources. Power-to-heat (P2H) is considered an economically viable SC approach that utilizes commercially available technologies. Previous studies demonstrated that electric water heaters and heat-pump water heaters (HPWH) effectively manage the demand and enhance flexibility. However, the practical implementation of P2H has been limited owing to policy limitations. This study proposed a P2H implementation model for South Korea that utilizes existing HPWHs deployed under the midnight power service, with a focus on flexibility provision through a reverse demand response (DR) program. The flexibility provision effect, energy efficiency, and economic impact were analyzed to evaluate the feasibility of the model. The case study results indicated that flexibility provision up to 100% of the device capacity was achievable, participation in the reverse DR program reduced power consumption by 4.4%, and operation costs decreased by 6–17% based on the DR scenarios.