Heating Thermal Energy Storage

If you are using electric resistance, natural gas, propane or fuel oils to produce space heating, you may be spending too much for thermal energy. Heating thermal energy storage uses electric resistance, the most efficient heat conversion process available, at night when electricity rates are low to produce heating energy for use during the day. Electric resistance efficiencies combined with lower off-peak electric rates can produce heating at a fraction of the cost of conventional systems.

How Does it Work?

Heating thermal energy storage cuts space heating costs by utilizing the 100% conversion efficiency of electric resistance strip heaters. This means that you can use each unit of energy that you purchase, unlike energy sources that must be burned to release their heating energy. Heat is produced by the strip heaters at night and the heat is stored in some type of storage medium, usually earth materials or ceramic bricks. The storage of heat at night means that you can take advantage of electric off-peak rates which are generally 33% to 75% less expensive than on-peak electric rates. The heat that is stored at night is contained in insulated containers until a standard room thermostat calls for space heating. At this time, the heat necessary to satisfy the room thermostat is removed from the storage unit and transferred into the room.

The use of earth as a heat storage medium is usually restricted to new construction since the application requires that electric resistance grids be placed 1 to 2 feet in the ground below the structure flow. The requirement that the grids be placed under the building makes this an impossible retrofit for any facility without a basement or crawlspace. For new construction applications, approximately 5 feet of earth directly below the structure is used for storage of heat produced by the grid. A rigid-waterproof insulating material is placed vertically around the perimeter of the building and extends approximately four feet below the earth grade line. The insulation insures that heat stored in the ground is forced to be radiated into the structure and not into the surrounding earth. The electric resistance grid is placed 1 to 2 feet below the earth's surface and covered with about two inches of sand and earth materials.

Ceramic bricks provide an excellent heat storage medium for retrofit as well as new construction applications due to their module sizes, ease of installation and their high heat retention abilities. These units are normally manufactured in various sizes and shipped to the building site. Their construction normally consists of an insulated box about the size of a conventional radiant hot water or steam heating unit. The module contains many ceramic bricks depending on the heat storage requirement and a small fractional horsepower circulating fan. The ceramic bricks contain electric resistance strip heaters in their holes. At night, during low cost off-peak periods, the strip heating units produce heat which is absorbed by the ceramic bricks. The insulation surrounding the bricks restricts heat losses from the bricks until it is required by the space to be heated. During the day, a conventional thermostat is used to control the fractional horsepower fan which circulates air from the room across the ceramic bricks to pickup heat and blows the air into the room. Once the thermostat has been satisfied, it shuts off the circulating fan and no more heat transfer takes place until the thermostat requires it again.

Is a Heating Thermal Storage System for You?

Heating thermal storage systems can be cost justified for almost any facility which requires large amounts of heat for space heating and is billed under electric rate schedules that have large differentials between on- and off-peak electric consumption. These types of rates are referred to as time-of-use rate schedules.