As the effects of global climate change are accelerating, the need to convert away from the fuels that scientists have identified as the cause of these changes becomes ever more essential. The conversion of energy production from hydrocarbon-based fuels to more sustainable sources like solar and wind production has faced one major hurdle: how to store energy from times it is produced to times when it is needed. Now, across the world, novel approaches to this challenge are being invented.
Thermal Innovation: Sand and Salt
Polar Night Energy Sand Battery, Pornainen
In Finland, the “sand battery” has moved from an experimental concept to a grid-scale reality. Developed by Polar Night Energy, the world’s largest operational sand battery in Pornainen uses 2,000 tons of crushed soapstone, which is a byproduct of local industry, to store renewable electricity as heat. By blowing air through pipes into a massive highly insulated silo, the sand is heated to over 500°C. This thermal energy can be stored for months, providing a low-cost seasonal buffer for district heating during the harsh Nordic winter.
Varanto Thermal Energy Storage Facility System
Similarly, Finland is breaking ground on the Varanto project in Vantaa, which will become the world’s largest cavern thermal energy storage facility. By storing water at high pressure and temperatures up to 140°C in giant underground caverns, the system will hold 90 GWh of energy—enough to heat a medium-sized city for an entire year.
Principle of Molten Salt System
In Germany, the focus has shifted toward molten salt storage. At the German Aerospace Center in Jülich, researchers are utilizing liquid salts that can reach 565°C. Unlike traditional batteries that store electricity chemically, these systems store it as heat and use a steam turbine to convert it back into electricity on demand. This approach is particularly effective for decarbonizing heavy industries that require high-grade heat for manufacturing.
New Horizons: Iron-Air and Gravity
Principle of Iron-Air Battery
Beyond thermal storage, 2026 has seen the commercial debut of Iron-Air batteries. Unlike lithium-ion batteries that rely on rare and expensive minerals, these batteries use iron, which is one of the most abundant materials on Earth. By utilizing a process of “reversible rusting”—where iron consumes oxygen to discharge energy and uses electricity to convert rust back into unoxidized metal—these batteries can provide up to 100 hours of storage. This makes them ideal for “multi-day” backups when the wind might not blow for a week.
Other innovators are looking to the sky—and the earth—with gravity-based storage. These systems use surplus solar or wind power to lift heavy blocks or pump water uphill. When energy is needed, the weights are lowered, or the water is released, spinning turbines to generate power.
Principle of Gravity-Based Storage
These and other, diverse technologies prove that the “storage problem” isn’t a single puzzle with just one solution. Instead, the future of sustainable energy generation will likely be a mosaic of sand, salt, iron, and gravity, each filling a specific niche in our transition away from hydrocarbons.
If you would like your New England project designed with the maximum sustainability and awareness of new technologies in mind, please reach out to the award-winning architects at A4 Architecture and we will be pleased to discuss your building plans with you.
Ross Cann, RA, AIA, LEED AP, is an author, historian, and practicing architect living and working in Newport, RI. He holds degrees with honor in Architecture from Yale, Cambridge, and Columbia Universities and studied Molecular Biophysics & Biochemistry while in college.
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