A new word in energy: Finland is building a “sand battery” to heat an entire city
The Finnish company Polar Night Energy has announced the creation of an industrial-scale “sand battery” that can be included in a district heating system. The developers said that the battery capacity should be enough to heat an entire city during cold polar winters.
Green energy, which includes, for example, solar, wind, tidal, and geothermal, is good because it uses renewable resources to generate energy. But one of its most significant disadvantages is that energy is produced only when it can be, not when it is needed. That is why the energy transition to renewable energy sources requires the development of not only production methods but also storage methods.
The form of storage of generated energy can be very different: from conventional lithium batteries to hydroelectric power plants, salt melt batteries, carbon dioxide batteries and other exotic ideas. However, lithium batteries are too expensive to compensate for months-long failures of solar generation in winter (or weeks for wind power). PSPPs are practically unacceptable to Western countries for ideological reasons, and other methods are usually even more expensive than lithium solutions. Therefore, the search for new ways to store energy continues to be a critical issue.
The idea of a “sand battery” developed and patented by Polar Night Energy is quite simple. Essentially, it is a large steel hopper with hot sand (or similar solid material) that is heated up to 1000 degrees Celsius through a heat exchanger located in the center of the tank. Excess electricity from the grid, generated, for example, by wind turbines or solar panels, is used to heat the coolant.
According to the developers, their high-temperature storage is so well insulated that it can store the accumulated energy for several months with minimal losses (no more than five percent). If necessary, energy can be extracted in the form of heat or electricity, although the former is preferable due to lower energy losses. At the same time, the specialists obtain sand for their plant from environmentally friendly sources. It consists of purified and dried crushed soapstone, a by-product of local industry.
Such a storage facility is planned to be used in Finland, connecting it to the local district heating system of the municipality of Pornainen with a population of just over five thousand people. Polar Night Energy has previously developed and built a prototype sand thermal energy storage system for a local energy company.
The prototype is capable of storing approximately eight megawatt-hours of primary energy with a rated power of 100 kilowatts. The new “sand battery” measuring 13 by 15 meters should be an order of magnitude more energy-intensive (up to 100 megawatt-hours of primary energy).
