A startup from Finland called Polar Night Energy has developed an energy storage system based on sand. The idea is to store excess energy generated from clean electricity sources such as Wind, Solar, etc., to be reused days or even months later.

If it works, it will help solve the primary pain point of intermittent clean energy sources by making their final energy output more predictable and, therefore, more reliable.

But how does it work, and why sand? Polar Night Energy’s solution is straightforward and elegant. They use clean electricity to heat a large mass of sand well insulated from the outside. It could be in a silo or even buried underground.

Such a mass heated to 500C (930F) would store that energy for months. In theory, it could store summer months’ energy to be used in the autumn and winter. The primary challenge is to monitor and control heat release, and that task would be computerized.

The first commercial application of this technology was made with a Finish utility company called Vatajankoski, and the stored energy will partially power the utility’s heating system.

If this design holds to its promises, it would be an exquisite and cost-efficient way of storing clean energy. The sand doesn’t even need to be expensive like construction sand, and no harmful chemical is required to build the storage system

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