Finnish engineers have developed a sand “battery” capable of storing renewable energy produced over several months in the form of heat for individual, collective or industrial purposes.

In its final Energy Futures 2050 report, published last February, RTE, for the electricity transmission grid, recalled that the “variability of production (renewable energies, ed) must be compensated for with flexibility “, understand solutions to store the energy produced so that it can be used when the grid needs it. A need that is not necessarily concomitant with production. The wind blows when it wants and the sun doesn’t always show up when you want it.

The uncertainty of renewables

To illustrate this variability, just look at other data provided by RTE last February. Thus, in 2021, renewable energies weighed less than the previous year, despite an increase in solar parks, in particular. Blame it on unfavorable weather conditions for both hydroelectricity and wind power.

Whether it is gigantic water tanks, which serve to produce electricity when the grid is required and whose water is then brought to the top using the electricity produced when the need is less or conventional batteries, the challenge is to find a way to use renewable energy optimally and store it with the least possible loss.

Find a low-tech but inexpensive battery

The problem with storage is that it is often necessary to use “conventional” batteries, which contain lithium, which limits a fairly high cost, especially since these battery packs take up a lot of space.

However, young Finnish engineers may have found an original, ecological and effective solution. Their company Polar night energy has developed sand “batteries”.

In fact, in terms of the battery, it is a silo, which looks like a grain silo, into which building sand is poured, which is more normal. This sand will then be heated and kept at a temperature between 300 and 500 ° C thanks to a weak electric current, produced from renewable sources. Because sand accumulates and retains heat very well, these hot sand “containers” can keep their contents warm for several months.

When electricity production becomes more expensive due to winter demand, for example, the air heated by the sand “battery” is in turn used to heat the water in the thermal systems of surrounding homes, offices and swimming pools. Electricity is not strictly stored, so the energy produced and transformed is.

One more step, a new solution

The next two stages in the development of this technology low-tech it will be fundamental. The first is whether these sand heat exchangers can be adapted for wider uses and adopted by larger communities. The second is whether the two engineers can find a solution to improve the return of energy in the form of electricity. So far, the performance is pretty low.

However, heat is a form of energy that can have real uses in many industrial contexts, whether for food preparation, pharmaceutical production or even for textile production.

These batteries are obviously not a revolution, alone they will not solve the question of the storage of renewable energies, but they bring their stone into the building, their little grain of… sand.



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