World's first commercial sand battery begins energy storage in Finland

World's first commercial sand battery begins energy storage in Finland
A new type of battery being put to use in Finland is exploring the potential of sand as an energy storage medium
A new type of battery being put to use in Finland is exploring the potential of sand as an energy storage medium
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The world's first commercial sand battery system is now in operation in Western Finland
The world's first commercial sand battery system is now in operation in Western Finland
A compelling set of advantages
A compelling set of advantages

Wind and solar power are intermittent, generating power when it's available rather than when it's needed, so the green energy transition will require huge amounts of energy storage. This could end up taking many forms, from conventional lithium-based "big battery" installations, to flow batteries, silicon phase-change batteries, molten salt batteries, iron-air batteries, gravity batteries, carbon dioxide expansion batteries, and other more unusual ideas like buoyancy batteries.

Each has its own advantages and disadvantages in terms of efficiency, size, location, installation costs, operating costs, input and output power ratings, longevity and how long it can store the energy for. That's good, since different solutions will fill different needs – some backing up the power grid during instantaneous demand spikes, others smoothing out the mismatched daily curves between demand and renewable supply, and others still helping to address seasonal supply drops, like when solar drops off through the winter.

Here's another for the pile, coming out of Finland. Polar Night Energy says it's just opened its first commercial sand battery at the premises of "new energy" company Vatajankoski, a few hours out of Helsinki.

The world's first commercial sand battery system is now in operation in Western Finland
The world's first commercial sand battery system is now in operation in Western Finland

This is a thermal energy storage system, effectively built around a big, insulated steel tank – around 4 metres (13.1 ft) wide and 7 metres (23 ft) high – full of plain old sand. When this sand is heated up, using a simple heat exchanger buried in the middle of it, this device is capable of storing an impressive 8 megawatt-hours of energy, at a nominal power rating of 100 kW, with the sand heated to somewhere around 500-600 degrees Celsius (932-1112 °F).

When it's needed, the energy is extracted again as heat in the same way. Vatajankowski is using this stored heat, in conjunction with excess heat from its own data servers, to feed the local district heating system, which uses piped water to transmit heat around the area. It can then be used to heat buildings, or swimming pools, or in industrial processes, or in any other situation that requires heat.

This helps make it extremely efficient, the company tells Disruptive Investing in a video interview. "It's really easy to convert electricity into heat," says Polar Night CTO Markku Ylönen. "But going back from heat to electricity, that's where you need turbines and more complex things. As long as we're just using the heat as heat, it stays really simple." The company claims an efficiency factor up to 99 percent, a capability to store heat with minimal loss for months on end, and a lifespan in the decades.

A compelling set of advantages
A compelling set of advantages

There's nothing special about the sand – the company says it just needs to be dry and free from combustible debris. Indeed, the company sees it as a super-low or even zero-cost storage medium. The whole thing's so simple and cheap that Polar Night Energy claims the setup costs are less than €10 (US$10.27) per kilowatt-hour, and it runs itself in a fully-automated fashion, using no consumables, at a minimal cost as well.

The company says it'll scale up, too, with installations around 20 gigawatt-hours of energy storage making hundreds of megawatts of nominal power, and the sand heated as far as 1,000 °C (1,832 °F) in certain designs. It's possible to create bulk underground storage facilities out of disused mine shafts, if they're the right shape. There are no high-pressure vessels needed, and the biggest cost involved is often the pipework.

The business name Polar Night is of course a reference to the fact that parts of Northern Finland see no sun at all during the winter, since they're above the latitude (~68 degrees north) where there's no direct sun at all for weeks on end through the depths of winter. This sand battery, says the company, will have its greatest impact during periods like this, when its long-duration storage will keep buildings heated cheaply and cleanly through the freezing Finnish winter.

Indeed, the solid sand storage medium comes into its own here, since the design enables multiple 'zones' of energy storage within the sand. It's possible to build a system designed for longer-term heat storage toward the center of the cylinder of sand, but shorter-term repeated use cycles closer to the top surface or the outside. This would be impossible in a liquid medium like water or molten salt, since the liquids would constantly be mixing and moving.

It's fair to say this system will only find widespread use in areas with district-level heating. But there's a surprising amount of district heating going on. Nearly half of all Scandinavian homes incorporate some form of it, and it can be found in many other areas too, including Northern China and the USA.

As such, Mission Innovation's climate solutions framework has estimated estimated that deploying Polar Night's energy storage system to its full potential could replace enough carbon-burning heat sources to reduce annual greenhouse emissions by somewhere between 57 and 283 megatons of CO2 equivalent per year by 2030. That would be a pretty significant contribution.

Source: Polar Night Energy

Brilliant because simple and inexpensive for the stated purpose
Steve Jones
This is absolutely stunning.
Hopefully this means a load of lithium which can stay in the ground for now, with the potential to be used more effectively in the future, than would be possible with today's technology.
Would be interesting to know the rate that energy can be transferred into/out of the store, the thermal coefficient of sand is really low ( 0.06 W/mK ) so its probably good for long slow energy release ( for local district heating as mentioned in the article ) but less likely to be of use for later converting back to electricity
This could be a DIY installation for domestic water heating/room heating, using spare solar electricity.
99% efficiency??? How is this insulated to hold the heat until needed??? How is it heated to begin with??? Steam??? Or just a lot of hot air from the salesman???
I hope it really is just using regular old sand and not the specific kind we need for making concrete. Last I checked we were running out of that kind of sand.
in northern africa a solar farm could use this battery system to store excess energy. thermocouples have been used for microwave sites for years to power the transmitters and receivers. a bank of them might be used to convert heat to electricity???
Well written, Loz. @SJones, this isn't alternative to batteries, as it is heat storage, not electrical. would be a comparable alternative. It is only about 70% efficient, but allows the energy to be transported. @Oirinth, correct, this is not for electricity generation, just heating. The energy transfer rate is in the article - 100kw for the existing installation, potentially scaled up to 100Mw.
The only downside is the need for a local heating distribution network. That in itself will limit the size of the silo (the size of the community served).
Doesn't it seem that this would be easy enough to scale DOWN so that sandpits could be built beneath new individual homes and any excess solar from the home's rooftop system could used to create a supplemental heat source for winters?
My guess is that the efficiency will be found much wanting, while the costs are extremely underestimated from real-life construction. But cheap and simple can be good partners in energy costs, so GO FOR IT, folks!
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