An innovative thermal energy storage system has redefined the way a small Finnish town heats its residential and commercial buildings, with an enormous silo of 2,000 tons of crushed stone capable of storing renewable energy heat in the form of heat stored for weeks upon weeks, a breakthrough in thermal heating technology that could revolutionize the way society globally considers a solution to carbon-neutral heating.
The largest sand battery in the world drives the heating of the district
Finnish small town is testing an alternative form of infrastructure: the largest sand battery in the world, as Fast Company states. The battery is a 42-foot-tall and almost 50-foot-wide silo holding 2,000 tons of crushed stone, which is located on the corner of a parking lot. When renewable electricity is available in abundance on the grid and power is cheap, electricity is then used to warm the crushed stone.
Such heat is stored in a battery until it is required by nearby buildings. The basic approach is simple. It only heats air and sends it through sand, says Liisa Naskali, COO of Polar Night Energy, the Finnish company that invented the technology. Sand or other material crushed to sand-size particles can store heat over the course of weeks.
Fossil fuel systems are substituted with carbon-neutral heating
The town, named Pornainen, is heated using a district heating system to warm a collection of buildings, including city offices and the local school, and some businesses and complexes of apartments. Until recently, the network either burned oil or used wood chips to burn. However, the municipality is looking to be carbon neutral, and it decided that it was time to change.
Now, when a person in an apartment beside them switches on the hot water shower, the heat is sourced by the sand battery. The heat produced by the battery, as with any other district heating system, is distributed by way of pipes filled with hot water to all other buildings; each building has its own equipment to distribute the heat to radiators and floor heaters, or other HVAC systems.
New technology can ensure that there is no oil dependency
This summer, the battery was started, and this week it was actually inaugurated, which is to say that the district heating system now consumes not a drop of oil. During the summer, it was wholly dependent on the sand battery. When the weather becomes colder, the battery will be used together with wood chips, but the consumption of wood chips will decrease by approximately 60 percent.
Although the startup refers to the technology as a sand battery, other materials can be used. In the new installation in Pornainen, the firm resorted to soapstone scraps used in making a fireplace in the neighbourhood. That also minimised waste and prevented the environmental issues associated with obtaining sand, which is usually dug out of rivers or lakes or along the coast.
Economical operation by use of intelligent electricity timing
The company has a heat exchanger and a closed-loop system in the silo to circulate heat. The heaters are operated by the software when the electricity prices are low. During the summer, Naskali reports that the utility charged only at optimal times and paid approximately 10 percent of the average price of electricity. That makes the technology competitive in costs, she says, but the upfront cost of its installation is expensive.
This new sand battery idea is a major breakthrough in the storage of renewable energy, and it shows that communities can be carbon-neutral and still have a reliable heating system. The Pornainen success would encourage such projects across the globe, a solution that scales up to sustainable district heating and minimizes carbon emissions as well as energy expenses.