The need for an on demand constant power supply can be difficult to achieve if you want your power to be renewable. Sometimes the wind will blow and the sun will shine too much for your consumption requirements. This doesn't cause a problem since you can simply put the brakes on wind turbines, cover up a solar panel, or you can burn off the excess power. This is a waste. Then, a problem arrises when there isn't enough wind and sun to meet your power needs.

A system to store power when you have too much and then release it when there isn't enough has been on the minds of people for some time. Obvious solution is to just buy lots of very big batteries. But they cost a lot of money, manufacture and disposal has environmental consequences, they require maintenance and have a limited lifespan.

If you were designing a sustainable system with the very least impact on the environment, you would likely consider Geoexchange. In the town of Pornainen, Finnland some very clever people have made the world's largest thermal storage "battery" using sand as their storage substance. It is not a batttery in the chemical to electrical scense that we are familiar with. Rather, it is a very large insulated, underground container of sand, that is heated up with electric heaters. The electricity comes from excess wind turbine power that would otherwise be wasted. This is not a very efficient process, but it does save a large proportion of the energy that would otherwise be wasted.

Unlike potential or chemical energy, thermal energy is difficult to store. It is prone to dissipation.

A sand battery is thermal energy storage, a type of Geoexchange. Similar projects like this include storing heat energy in massive underground water reservoirs. It turns out that sand is also a good material for storing thermal energy.

Then when the wind isn't blowing strongly enough to keep up with electricity demand, instead of turning on fossil fuel heating systems, the heat energy held in the sand can be sourced. Water pipes snaking through the hot sand are piped directly to homes and businesses in the town.

Imagine a sand battery as part of a large hospital heating system in a country with cold winters. Such a system could include solar panels and wind turbines that both collectively add surplus energy to the sand. Then when required, the thermal energy from the sand boosts the water temperature going to the heating boilers. Combining with heat pumps the temperature can be raised further. This would cut fuel bills substantially.

About The Author
Jane Duncan
Chewells Contributor

Jane is passionate about the environment, she is our main contributor for the renewable industry blogs. She... »

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