Electric Thermal Storage Heating (ETS)
Electric Thermal Storage (ETS) is a heat storage technology that can reduce home heating costs where time-of-use (TOU) or low, off-peak rates are offered. Where such rates are available, electricity is most expensive during the day-time hours when the demand for power is the highest. ETS shifts the home’s heating load from the higher-cost, on-peak hours to the less-expensive, off-peak hours thereby reducing electricity costs.
In the most common ETS systems, heat produced with electricity during off-peak times is stored in dense ceramic bricks. When heat is needed, a blower moves the heat from the bricks to the living space. In addition to individual room heating units, other ETS products available today include heat pump boosters, hydronic heating systems and forced air furnaces.
In recent years, as the installation of heat pumps in colder climates has grown, ETS is finding a place helping them attain the optimal economical operation. Heat pumps provide extremely high energy efficiencies, but as outdoor temperatures fall, so does their efficiency. At some point the heat pump can no longer keep the home at a comfortable temperature on its own and a
supplemental or back-up heat source is needed.
When the back-up is provided by resistance electric heat, the resistance heat uses the standard electric rate, which is generally two times higher than the off-peak rate. Using ETS, which has stored less-expensive heat produced off-peak, as a heat pump booster replaces the need for direct resistance heat at times when prices are higher. The heat pump booster can also deliver a higher level of constant comfort in the home by continually monitoring duct temperatures and injecting as much heat as necessary to keep the home comfortable.
ETS can make electric heating cost-competitive with fossil fuels. Where affordable, off-peak electric rates are offered, customers may be able to save significant money by converting to ETS heating in lieu of their propane heaters, natural gas heaters, wood stoves or fire places. The savings using the ETS system are largely influenced by three factors :-
1. The differential between the utility’s on-peak and off-peak rates, 2. The length of time each day that is off-peak, and 3. The annual amount of home heating needed.
ETS Description
The ETS unit can be designed as the main forced-air or hydronic heating system for homes or small commercial buildings. It can also be installed as a supplement to another heating system.
As a supplement, ETS can increase the overall efficiency of a heat pump system, provide assistance to an electric furnace during on-peak times, replace a duct heater, or supplement a fossil fuel system. ETS systems work by converting electricity at the utility’s off-peak times (usually at night) into heat and storing that heat in specially designed, high density, ceramic bricks. Because ETS systems use off-peak electricity, to be maximally economical, their operation is limited to off-peak operation. That means the system must be carefully sized to assure it can hold enough heat to maintain comfort at the coldest temperatures that would occur in the year.
ETS units have control systems that automatically regulate how much heat is stored in the brick core in relation to outdoor temperature and the heating requirements of the user. When the room thermostat calls for heat, heat is extracted from the unit’s storage core and is distributed into the home until the call for heat has been satisfied. ETS systems can be integrated with all the common peripherals like an air conditioner, electronic air cleaner, central humidifier, and programmable thermostats.
Source:Home Energy Library