Lithium-free and low-cost: How sand could be the future of energy storage?

New Delhi: On the surface, it looks like an ordinary industrial silo in a quiet Finnish town. But step closer, and you realise this unassuming grey tower in Pornainen holds a world-first innovation. Inside are 2,000 tonnes of crushed soapstone — a type of sand — that have been turned into the world’s largest “sand battery”, capable of storing enough heat to keep an entire town warm for weeks.

In an era where countries are chasing net-zero targets and wrestling with the problem of storing renewable energy, Finland’s sand battery has captured global attention. And for India, which is balancing its clean energy ambitions with rising power demand, it could be more than just an interesting experiment. It could be a blueprint for the future.

The timing problem that plagues renewablesWhether you are in Helsinki or Hyderabad, the challenge is the same: renewable power doesn’t always show up when you need it. Solar plants hum with energy in the day but fade at night. Wind turbines spin wildly in stormy weather but can go still for days.Traditional lithium-ion batteries can store electricity, but they are expensive, dependent on minerals like lithium and cobalt — which India imports — and they degrade over time. For a country with vast industrial needs and sharp seasonal swings in energy demand, the search for a low-cost, scalable, and durable alternative is urgent.Finland’s simple yet radical answerInstead of storing electricity, Finland’s engineers decided to store heat — one of the most direct forms of energy we use daily. The sand battery works by using surplus renewable electricity to heat air, which is then pumped into the insulated silo full of sand. This sand reaches temperatures of several hundred degrees Celsius and can trap that heat for months without major losses.When needed, the heat is released into Pornainen’s district heating network, replacing oil and slashing the use of wood chips. The result? A nearly 70% drop in heating emissions — a game-changer for a country where winters routinely dip below minus 20°C.How it could work in IndiaIf India adopted this technology, it wouldn’t be just for heating. Our needs are different. Stored thermal energy could power textile mills in Surat, run chemical plants in Gujarat, keep food processing units in Punjab operating year-round, or even support desalination in coastal cities.It could also feed district cooling systems in cities like Mumbai, Delhi, and Ahmedabad, where extreme summer heat pushes electricity grids to breaking point. The beauty is that sand is abundant, non-toxic, and cheap. Unlike lithium-ion storage, it doesn’t require rare minerals or complex recycling systems.India’s circular economy vision could get a boost too. Waste from stone-cutting units, mining operations, or construction sites could be repurposed as the storage medium — exactly as Finland did by using soapstone by-products from a fireplace manufacturer.

Smart energy, smart economics

Finland’s system doesn’t just sit there storing heat blindly. It’s optimised by AI software from Finnish telecom company Elisa, which decides when to store heat (when renewable power is cheap and plentiful) and when to release it (when demand peaks).For India, similar AI integration could help balance grids with high shares of solar and wind, while reducing dependence on coal during demand surges. The economics are promising too: sand batteries are cheaper to build and maintain than chemical batteries and have a lifespan of decades. That means lower costs for industries and fewer supply chain headaches.

Why India should pay attention now

India has pledged to install 500 GW of non-fossil fuel capacity by 2030. But that goal depends on one thing — reliable, affordable energy storage. Battery Energy Storage Systems (BESS) will play a key role, but they can’t cover every use case.

Sand batteries offer a complementary pathway that’s local, low-maintenance, and flexible. They could be deployed in industrial clusters, urban energy networks, or even as part of hybrid renewable projects that combine solar, wind, and heat storage.

A quiet revolution in the making

What makes the Finnish experiment so inspiring is its simplicity. There’s nothing futuristic-looking about the Pornainen silo. No shiny panels, no whirring turbines — just a silent, insulated cylinder holding heat in grains of sand. Yet, it solves one of the toughest problems in the renewable transition.

For India, where resourcefulness often drives innovation, this is a reminder that the future of clean energy doesn’t always come in sleek, high-tech packages. Sometimes, it’s hiding in the dust beneath our feet — waiting to be shaped into a solution that could keep our lights on, our factories running, and our cities cool.