Storing Electricity as Heat | Green Energy News

May 11, 2008 – Vol.13 No.8

STORING ELECTRICITY AS HEAT.

Otter Tail Power has a suggestion to cut energy costs in homes and other buildings. As part of the construction of a new building, remodeling or a building addition, include a thermal mass that’s heated internally with electric cables buried within; build a floor slab that’s like an electric blanket made of concrete, sand and insulation. Then use only low-cost, off-peak power to electrify this radiant heating system. With this basic technology, electricity is effectively stored as heat for 8 -14 hours. Call the whole thing an off-peak electric thermal storage (ETS) system, or a very low tech heat storing battery if you will .

Generally speaking thin-walled, stick-built homes in the US are not up to the task of coping with high energy costs or reducing their carbon footprint. Newer homes are better than old but most homes are about as sophisticated energy-consumption-wise as a 1960’s Detroit-built car.

Fortunately, unlike developing technologies to build hyper-energy-efficient cars, the technologies to build hyper-energy-efficient homes and other buildings are already available in the market place. The cables used to heat a thermal mass with electricity in a building are the same as those used to melt snow off driveways. (Some homes actually have this energy-wasting feature.) Electric load regulating technology is also available to tap off-peak power for this and other uses. Building an off-peak electric thermal storage system is just a matter of doing it, not like with cars waiting for the technology to be commercialized.

Of course, the thermal mass doesn’t necessarily need the electric cables. It can also be heated passively by the sun.

In its most basic form a thermal mass is a big thick chunk of concrete, adobe, compacted earth, brick, sand, stone or some other heavy dense material. It can be used without the help of human generated energy to heat as well as cool a building. The thermal mass can be the slab foundation of a building as well as some interior walls. The mass is also heavily insulated to keep it from contact with the outside world.

This passive solar thermal mass is heated by direct sunlight and light that bounces around the inside of the house. Warm air from indirect solar heating from the house can also be circulated over or through the mass to warm it. The bigger and denser the mass is the more heat it will absorb and store.

The passive solar thermal mass works tirelessly without assistance. In the winter the mass absorbs the heat of sunlight to release it at night. In summer, with as much direct sunlight kept out of the building as possible, the mass absorbs any stray heat keeping the house cool. Good ventilation exhausts any additional hot air.

For those who aren’t building new or heavily remodeling, there’s an additional option for off-peak electric thermal storage. At least one company, Steffes Corporation of Dickinson, North Dakota, makes heating equipment that stores heat with specialized bricks. The equipment can be timed to switch on and generate heat at off-peak hours. Later heat is released as needed in peak periods. The company makes central thermal storage forced-air furnaces, hydronic furnaces, room units and load management controls for tapping off-peak electricity.

Studies have already shown that there’s plenty of off-peak, unsold power on the US grid to charge the batteries of millions of plug-in hybrid electric vehicles. That same power could instead be used in homes for electric thermal storage (ETS). Unsold, off-peak power from the grid has been described as one of our nation’s greatest resources. Putting it to work reduces greenhouse gases because it eliminates the need to build new power plants, and perhaps could actually close some.

Our houses leave a larger carbon footprint than our cars, and home energy costs are skyrocketing too. The technology is available to make homes dramatically more efficient. Perhaps while hyper-energy-efficient cars are still to be developed we should concentrate on the home front.

Otter Tail Power is an electricity provider for residential, commercial, and industrial customers in Minnesota, North and South Dakota.

Links:

Otter Tail Power
http://www.otpco.com

Otter Tail Power, Thermal Storage Underfloor Heat
http://www.otpco.com/ProductsServices/ThermalStorageUnderfloorHeat.asp

Steffes Corporation
http://www.steffes.com

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