Saur Energy Explains: Grains to Grid – Power of Sand Batteries

Energy storage technologies are evolving at a fast pace in order to keep up with the new-age energy storage demand. New innovations in battery technologies have enhanced energy density, life, and cost components of the novel batteries, making them more favorable than ever before. Thermal storage based Sand batteries are one such ESS technology that has been making headlines recently.

Although Li-ion batteries lead the energy storage space as of now, innovative battery technologies like solid state battery, thermal batteries, sodium-ion battery, flow battery, lead-acid battery, and many more, are now entering the commercial energy storage space and are here to stay.

This explainer will cover how sand batteries work, how they compare to other energy storage technologies, their market outlook and key projects, and any other relevant data surrounding this innovative technology.

Introducing Sand Batteries

Sand batteries are large-scale, high-temperature thermal energy storage systems that promise affordable, long-duration energy storage using sand –  one of Earth’s most abundant materials – or similar materials to store energy as heat.

In a sand battery system, electricity from sources like solar or wind is converted to heat which is stored in an insulated sand silo and later released for useful energy – mainly heat, or even electricity if needed. These sand silos often store at hundreds of degrees Celsius.

How Do Sand Batteries Work?

The simple mechanism is that sand batteries store energy as heat during times of surplus and discharge heat when there’s demand. Sand can be heated to well above 500°C, allowing more energy to be stored per unit of material.

According to the Finnish startup, Polar Night Energy, which has commissioned the world’s largest sand battery in Finland, their Sand Battery storage unit is  typically 10 to 15 meters tall. Depending on capacity, the diameter ranges from 4 to 30 meters.

Energy Storage

At its core, a sand battery is a large insulated container filled with sand, or similar material like crushed rock. Excess renewable electricity, like solar power on a sunny day or wind turbines on a windy night, is used to heat air via resistive heating elements. This hot air is blown through the sand to raise its temperature.

The sand can be heated to around 500°C (or even higher in some designs) and will retain that heat for days or months due to insulation.

Energy Deployment

When energy is needed – say on a cold winter night – the hot air is drawn off from the sand through a heat exchanger to heat water for a district heating network, warming homes and buildings.

For the Polar Night Energy battery, the output is hot water, steam, or air, with temperatures up to 400°C, suitable for 36 percent of industrial process heat needs.

Advantages of Sand Batteries

Sand batteries belong to the category of long-duration energy storage, aiming to store large amounts of energy at low cost. They have some clear advantages compared to conventional batteries as well as other storage tech.

Cost-effective

Being one of the cheapest battery technologies is probably the USP of a sand battery. Sand  – silica sand or similar – is extremely cheap and widely available – on the order of ~USD 30 per ton in the US market, and is considerably cheaper than this in Asian countries like India.

Further, the cost of installation of insulated silos with heating elements is also less. As per a BBC report from a few years back, a sand battery is eight to 10 times cheaper than a lithium battery which stores the same amount of energy. Furthermore, scaling up a sand battery means just adding more sand (bigger silo) which is relatively cheap compared to stacking up more lithium batteries.

Storage Duration

Another advantage is that the sand batteries are ideal for long duration storage (10+ hours up to several weeks) at large scale, unlike lithium-ion batteries which would be needed in massive volumes which is prohibitively expensive and they self-discharge over time. For instance, Finland’s new sand battery can store 100 MWh of heat – enough to supply a small town’s heating needs for a week in winter.

Efficiency

If the goal is to provide heat, say for space heating, industrial processes, etc, sand batteries are very efficient. Most of their input energy can be recovered as heat – typically ~85–90 percent or more. This makes them excellent for decarbonizing heating needs, which are a large part of energy consumption in cold climates and industries.

Energy Density & Space

It is indeed true that sand has a lower energy density than battery chemicals – storing 100 MWh in sand requires a fairly large silo, in Finland’s case, ~13 meters tall and 15 meters wide holding 2,000 tons of sand/stone. A lithium battery farm of the same 100 MWh might fit in a big warehouse. However, they can be built vertical and don’t necessarily need much land area, reducing space required.

Moreover, unlike pumped hydro which needs specific geography (hills, large water reservoirs), sand silos can be built anywhere – even in flat or arid regions. And compared to huge thermal storage tanks of water, sand can store heat at much higher temperatures, taht is 500+°C of sand against water’s ~100°C limit. This meaning more energy stored per unit mass.

Lifespan and Sustainability

Sand batteries contain no toxic or rare components – mostly just sand/stone and steel – and face no cycle degradation issues. A sand or rock can be heated and cooled thousands of times without performance loss, whereas lithium-ion batteries begin to degrade after a few thousand charge cycles. This means a sand battery installation could last for decades with minimal replacement and negligible maintenance. Mining concerns linked to battery metals are also alleviated.

Moreover, sand batteries don’t necessarily need high-grade river sand – any sand-like or crushed rock material that meets density and heat specs can be used, even industrial residues. In Finland, for example, the latest project used crushed soapstone waste from a local fireplace company as the storage medium.

The Pornainen sand battery now provides the majority of a town’s heating demand and helped cut local heating emissions ~70 percent by replacing oil-burning boilers. It also reduced biomass fuel use (wood chips) by 60 percent.

Market Analysis

Sand batteries are very new having  just now entered commercial use. The world’s first commercial sand battery was installed in 2022 in Kankaanpää, Finland (8 MWh thermal storage) as a pilot, followed by a much larger unit in 2025 in Pornainen, Finland (100 MWh) which is currently the world’s largest.

Numerous companies and research groups are now jumping into the sand (and rock) storage arena. As per a recent report by Precedence Research, global sand battery market size is predicted to increase from USD 1.38 billion in 2025 to approximately USD 4.86 billion by 2034, expanding at a CAGR of over 15 percent from 2025 to 2034.

Key drivers for this growth would be the push for grid integration of variable RE power, reliable clean heating requirements in buildings and industry, and the advantages of sand batteries in terms of sustainability and cost.

Regional Insights

Geographically, North America and Europe currently lead in sand battery development, North America being the largest regional market in 2024, and Europe home to notable early projects. However, Asia-Pacific is expected to be the fastest-growing market for sand batteries going forward.

Key Players and Projects Worldwide

Several firms have endorsed the sand batteries, or any similar thermal batteries using the same mechanism. Polar Night Energy – a Finnish startup – is the name most associated with sand batteries today, as mentioned earlier.

The success in Pornainen has drawn global attention, prompting Polar Night to engage with local and international partners for wider deployment. The company is also working on converting stored heat back into electricity — a key challenge that limits round-trip efficiency to around 50 percent in current sand battery designs.

Notably, the US-based Antora Energy uses graphite blocks to store energy as ultra-high temperature heat of about ~2400°C, and convert it back to electricity efficiently.

Other innovators are using different materials. For instance, Scotland’s Sunamp uses special salts for heat storage in homes, Israel’s Brenmiller Energy uses crushed rocks in its bGen units for industrial heat storage. The US startups like Rondo Energy use stacks of refractory bricks heated by renewables to deliver high-temperature heat for factories.

Although in a different technology category, an Indian startup, Baud Resources, is developing a system that lifts and dumps sand to store energy as gravitational potential, like pumped hydro but substituting water. They are constructing a 100 MWh pilot and estimate an extremely low storage cost around INR 2.5 per kWh (~$0.03/kWh).