Electric hot water systems are currently being phased out in countries such as Australia, but in the USA where water heating represents between 13 and 17 percent of residential energy consumption nationwide, approximately 42 percent of all homes in the U.S. still have electric water heating – in excess of 53 million homes.
Usually hot water sourced from renewable energy is associated with solar hot water systems, but a recent study by Rebecca Farrell Troutfetter of Frontier Associates LLC outlines the possibility of off-peak water heating programs to generate demand for renewable energy sources such as wind power.
Home hot water systems are retaining or delivering hot water on a continual basis and most systems are very effective in retaining temperature. Since they can be modified to only heat only during off-peak hours, the systems can be altered so as to utilize renewable energy generated off-peak; reducing peak loads and effectively acting as a renewable energy "battery".
Electric water heaters would need a dedicated device with temperature and voltage control capability connected to an electric company load control switch, utility-controlled to only operate during off-peak hours.
The water heater would need to heat stored water past the conventional set point in colder areas to meet household hot water needs over the entire peak duration when power would be cut to the system. This would present possible scalding dangers, so a thermostatically controlled mixing valve would need to be installed to mix cold water with the stored hot water to conventional temperatures.
An example of where this could work well is in the state of Texas. Texas is a large producer of wind energy, the majority of which is generated off-peak. By shifting electricity loads from on-peak to off-peak, the demand for off-peak generation sources such as wind power increases. Wind generation is lowest during the summer peak months in Texas, indicating that wind energy could have high potential use for year round water heating in the state.
The full study can be viewed here (PDF)
