A simple peak shifting DSM (demand-side management) strategy for residential water heaters

• A generalized pattern for daily demand of hot water in households was developed based on literature.
• Literature on the cooling behavior of hot water mass in cylindrical hot water tanks was reviewed.
• Exergy destruction during hot water consumption was investigated for different initial uses and standing times.
• A simple cost analysis was carried out to show the economic viability of the proposed DSM (demand-side management) program.
• Timer-setting strategies were discussed based on the experimental observations.

In many developing countries due to lack of infrastructure the utilities experience difficulties in monitoring their customers' demand or time of use of electricity and hence it is very difficult to apply DSM (demand-side management) programs for peak shifting. In several of these countries the residential EWHs (electric water heaters) are usually responsible for the evening peak. The general attitude of people is to turn them on just before they need hot water and statistics have shown that this takes place in the evening hours constituting the evening peak. The present work reviews the experimental findings about the static and dynamic cooling behavior of hot water in storage tanks and discusses the possible timer programs to avoid the peak hours. It is deduced from the experiments that even when the hot water is kept standing in a tank for 12 h after the initial withdrawal of 64.2 L, it would be possible to have warm water at temperatures above 40 °C in the top 15% of the tank to utilize. If the DSM programs are carefully designed it would be possible to set the timers to operate the EWHs for once or twice a day to meet the daily demand of households.