In a remarkable feat of innovation, a team of Finnish engineers has cracked one of the clean energy sector's most persistent problems: how to store renewable power for a rainy day—or more accurately, for a long, sunless winter.
Their solution is as elegantly simple as it is bizarre. They have built the world's first fully functional 'sand battery', a giant steel silo filled with ordinary builder's sand that stores energy as heat.
How Does a Sand Battery Work?
The process begins with cheap electricity generated from wind or solar sources. This power is used to heat air inside the battery, which is then circulated through the sand via a heat exchanger.
The sand, a highly effective medium for retaining thermal energy, can be heated to a scorching 500°C (932°F) and hold onto that heat for months on end. When energy is needed, the battery releases the hot air to warm water, which is then pumped into the local district heating network to heat homes, offices, and even the local swimming pool.
Tackling the Intermittency Crisis
This technology is a potential game-changer. The greatest challenge for renewables like wind and solar is their intermittency; the sun doesn't always shine, and the wind doesn't always blow. Large-scale, cost-effective storage has been the holy grail, and lithium-ion batteries are often too expensive and resource-intensive for grid-level use.
The sand battery offers a cheap, low-impact, and highly efficient alternative for storing excess energy generated during sunny or windy spells, making green power a reliable year-round option.
A Proven Concept in Kankaanpää
The first commercial-scale model is already operational in the town of Kankaanpää, in western Finland. Developed by the startup Polar Night Energy, the battery has been integrated into the town's energy infrastructure.
As Finland faces soaring energy prices exacerbated by the war in Ukraine, this local, sustainable source of heat provides not only environmental benefits but also crucial energy security and price stability for the community.
While currently used for heating, the engineers at Polar Night Energy are already working on the next step: scaling the technology to also generate electricity. This would involve using the stored heat to power a steam turbine, a development that could truly revolutionise how we power our world with clean energy.
