From Sand to Stability: Powering the Shift to Renewables

The world's largest sand battery is now in operation in Pornainen, Finland. Developed by Polar Night Energy, the battery has a storage capacity of 100 MWh and delivers 1MW of thermal power. With the launch, oil will be phased out of Pornainen’s heating network. The battery charges with grid electricity when the electricity price is low. With Finland’s energy mix, which contains 43% of renewables and 26% of nuclear energy, the sand battery is expected to reduce the annual CO2 equivalent emissions from local heating by nearly 70%. The sand battery also presents a cheaper alternative to lithium-ion batteries, which cost approximately $115 per kilowatt-hour. In comparison, a smaller sand battery prototype has been estimated to cost around $25 per kilowatt-hour. 

Thermal batteries store energy in the form of heat that was originally electricity, then dispatch it as heat or convert it back to electricity when needed. Some companies developing such systems include Rondo Energy, which heats stacks of bricks with a resistance heater; Electrified Thermal Solutions, which runs electrical current through thermally conductive bricks to generate then store the heat; and Antora Energy, which uses carbon-based blocks to generate and store heat, while also aiming to use thermophotovoltaic technology to transfer the heat back into electricity. 

With the integration of renewable energy, storage systems have become essential- first, to store excess generation for later use, and second, to stabilize grid frequency. These challenges were less prominent with fossil fuels, which can provide dispatchable electricity throughout the day and have physical inertia that supports grid stability. In addition to thermal batteries, pumped hydro systems pump water from lower reservoirs to higher ones during periods of high renewable production, then release it during times of high demand. Long-duration pumped hydro energy storage accounts for about 95% of global electricity storage. Lithium-ion batteries are also used for grid frequency balancing due to their millisecond-level response times. As the world shifts toward clean energy, storage systems will be key to building a stable and resilient grid.