Sand thermal storage

Sand thermal storage: can this thermal energy storage technology give a new impetus to the development of “green” energy?

In Finland, based on a new technology for storing generated energy, a large “sand accumulator” has been built and put into operation. The high-temperature heat accumulator was built on the territory of the power plant in the city of Kankaanpää. Will the introduction of new energy storage technology, on an industrial scale, give a new impetus to the development of “green” energy?

Adepts of “green” energy consider its main “advantages” to be the renewable sources from which energy is obtained, and the absence of emissions during energy generation. This, of course, is good, but “green” energy has no less significant drawbacks. These are the high cost of generated energy, seasonality plus the unpredictability of generation (which depends on natural, weather conditions, etc.) and the problem of storing excess energy received so that it can be used during periods of production decline.

According to specialists from Polar Night Energy, who have applied a new and cheap technology for accumulating and storing heat (energy) in their “sand battery”, the problem of the high cost of storing excess “green” (solar and wind) energy generated during the “high” season is being solved. Until now, the generated surplus has been “stored” in the form of electricity in batteries. And it is very, very expensive.

The Polar Night Energy sand storage tank is a large steel container (7 meters high) that is filled with 100 tons of ordinary construction sand, which is cheap and can store a lot of heat in a small volume. Excess generated solar and wind energy is used to heat the sand in the container. The sand heats up to 500-600 degrees Celsius (although the heating process is rather slow) and can store the accumulated heat for several months. Thus, surplus energy generated during the sunny or windy season can be “cheaply and efficiently”, with minimal losses, stored in a heat accumulator until the cold season, when the accumulated energy can be used to heat residential buildings.

The hot sand of the heat accumulator heats the air in a special container, which is installed inside the body of the “sand accumulator”. From the tank, hot, sand-heated air is supplied to the heat exchanger, where water is heated (boiled), which, in turn, is supplied to the centralized heat supply network for heating residential buildings. The thermal power of this “sand accumulator” is estimated at 100 kW, and its energy consumption is 8 MWh.

In itself, this technology is not new (in the sense of theory), but the “embodiment” of technology in a really working heat accumulator of this scale is happening for the first time. If the “sand accumulator” proves to be effective in energy saving and the ability to smooth out uneven heat consumption depending on the season, then such an alternative method of heating houses can be applied on a larger scale than now (at present, with the help of a heat accumulator put into operation, it is planned to heat during the winter season, a small village located in the immediate vicinity of the Kankaanpäa power plant). If the capacity of such energy storage facilities is increased to 20 GWh, this will make it possible to centrally heat all residential buildings throughout the city.

Sand thermal storage

It is quite possible that the mass use of such heat accumulators (allowing the conversion of excess “green” electricity into heat and providing storage of this heat), if not a breakthrough in “green” energy, will certainly give a new impetus to its further development. Since the generation of wind turbines and solar panels is extremely unstable and depends on many factors (season, weather conditions, day-night cycle, etc.), there are periods when all the generated electricity goes to the grid for consumers, and there are periods in which generation exceeds consumption. It is during the period of excess generation that heat accumulators should “reserve” excesses (albeit in the form of thermal energy) and store it until it is in demand. And since the “cost of storage” of energy by heat accumulators is incommensurably less compared to the “storage” of excess “green” electricity using batteries (due to the cost of building a heat accumulator and the almost eternal life of its filler), using this technology is very “cheap” and angrily” the issue of accumulation, storage and use at the right time of excess generation in the “green” energy is being solved.