Energy system flexibility through scheduling hot water heaters – valley filling versus reducing peak power demand

Electric water heaters represent an existing, but often overlooked, opportunity for providing flexibility in power systems through intelligent load shifting. This study investigates the load shifting potential and economic benefits of implementing control strategies for the electric water heater systems at Oslo Airport Gardermoen. Two control algorithms were developed and simulated: (1) Maximum Load Shifting, which aims to concentrate the water heater consumption during off-peak hours, and (2) Peak Avoidance, which focuses on reducing consumption during periods of high electricity demand. The simulations were based on electricity consumption data and a minimum of hot water is always ensured. The results demonstrate that the Maximum Load Shifting algorithm could shift 61.2% of the water heater consumption to off-peak hours, resulting in a total energy shift of 182.3 MWh over a 12-month period. The Peak Avoidance algorithm reduced the monthly peak demand attributable to the water heaters by an average of 87.92 kW. These load shifts led to a total annual cost savings of € 5700 and € 3650 for the two strategies, respectively. The findings highlight the potential of water heaters as a cost-effective and readily available flexibility resource in large commercial buildings.