Sand batteries are a significant advancement in clean energy technology.

This month, Finland launched the world's largest sand battery, enabling residents to remove oil from their district heating network and reduce emissions by nearly 70 percent, as reported by Euro News. If it continues to operate as efficiently and affordably as expected, sand batteries could become common worldwide.

Developed by Finnish company Polar Night Energy, this battery uses excess clean electricity to heat sand to high temperatures, storing thermal energy that can later be released to heat homes and power local industries. This is not Finland's first sand battery, but it is significantly larger. The facility in Pornainen is an insulated silo that stands 13 meters tall and 15 meters wide, containing 2,000 tonnes of crushed soapstone. The sand retains heat remarkably well, losing only 10 to 15 percent during storage and recovery, according to The Cool Down.

The system can hold up to 100 MWh of energy for weeks, sufficient to heat the town center even in winter, according to a World Economic Forum report. When the battery releases heat, it can reach temperatures of 400º Celsius (752º Fahrenheit).

Long-term energy storage is becoming increasingly important as energy grids rely more on variable sources like wind and solar. It allows for capturing excess energy during peak generation and redistributing it when demand exceeds supply, making thermal energy storage a practical solution.

Despite being recently activated, Finland's latest sand battery is already attracting attention for its cost-effectiveness and efficiency. The Cool Down notes that it's difficult to find a cheaper energy storage system. The soapstone used in Pornainen's battery was leftover material from a fireplace manufacturer.

TechCrunch estimates the Finnish battery's costs are under $25 per kilowatt-hour, compared to around $115 for leading lithium-ion batteries, which only store energy for short periods. Additionally, since the sand battery uses recycled materials, it avoids the supply chain issues faced by lithium-ion technology, which can also be environmentally damaging due to lithium extraction. This makes sand-based storage a more sustainable and accessible option.

Sand batteries offer multiple advantages: they have high specific heat, low thermal conductivity, and pose no fire risk, leading to increased interest in grid-scale and industrial applications, as noted by Interesting Engineering.

While Finland is at the forefront, other countries are also exploring sand battery technology. In April, the U.S. Department of Energy announced a $4 million pilot project for a sand battery near Boulder, Colorado. The NREL team estimated that their system could retain over 95 percent of heat for at least five days and achieve a targeted storage cost of 5¢ per kWh under various scenarios, though the project's future remains uncertain with the new administration.