The photo is sourced from polarnightenergy.fi
The storage is a steel silo with a capacity of 100 tons, which is seven metres tall and four metres wide. The reservoir filled with dry and clean sand contains heat transfer pipes whose structure resembles an uncompressed spring. The energy accumulation and usage chain consists of several stages. First, excess electricity produced by solar and wind generators during hours of low demand is fed to a resistance heater, which heats the air to 500–600 degrees Celsius. The air is then sent via pipes to the silo where sand is heated to the same temperature. In order to extract energy, the pipes inside the silo need to be blown with cold air, as a result of which the exhaust pipe starts to transfer heat, which can be used to heat up water tanks for central heating.
The project’s chief advantage is its safety. Sand can be stored at temperatures up to 1,700 degrees Celsius, which is why the sand battery, unlike lithium-ion ones, does not require a special cooling system. Another advantage is the possibility of storing energy for several months. It must be said, however, that Polar Night Energy estimates that the optimal cycle for charging and discharging the battery should not exceed two weeks. Finally, another strength of the project is that it can be easily scaled up: according to Polar Night Energy, the most popular of these batteries will have a heat power of 10 megawatts and an energy capacity of 1,000 megawatt-hours, which is 100 times more than the pilot version built in the process of creating a full-scale commercial prototype.
Polar Night Energy’s project has contributed to an investment boom in the sphere of energy storage. According to the International Energy Agency (IEA), 2022 saw investments in the construction of energy storage systems grow from $2 bln to $3 bln in Europe and from $7 bln to $12 bln in the developed countries at large.
