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Finland’s “Sand Battery” Could Solve Solar Intermittency

Much like cell phone and internet companies, energy providers are in a relatively unique position regarding reliability. If a local McDonald’s were to shut down for renovations, potential customers might see it as a momentary inconvenience and go elsewhere for that day’s lunch. 

With energy companies, customers pay a monthly fee and may interpret any service interruption as violating their agreement. No matter how temporary it is, there will always be a few dozen angry consumers demanding answers for lack of lighting, an inability to cook food, or a shutting down of their air conditioning units. It’s not too difficult to grab a chicken wrap instead of a cheeseburger and fries; however, it is a far greater challenge to spend the night without power.

Reliability reality is one of the biggest obstacles to the world getting fully on board with renewable energy. Many have pointed to the lack of a dependable alternative to coal and oil energy to support the world’s immediate needs. If we want to convert to solar and wind, we need to accept inconveniences like scheduled blackouts or work toward technological breakthroughs that can change the intermittency equation. Thankfully, startups like Polar Night Energy are developing game-changing batteries using sand to solve the dilemma. 

Photo Courtesy Polar Night Energy

The Finnish startup has recently installed its first commercial sand-based battery system at the Vatajankoski power plant in Kankaanpää. A tourist or passerby probably wouldn’t know what to make of what is just a simple, nondescript silo filled with roughly 100 tons of sand, but its creators would call it the key to the energy lull problem. “Whenever there’s like this high surge of available green electricity, we want to be able to get it into the storage really quickly,” says Markku Ylönen, Polar Night co-founder.

The secret is in the temperature.

The mass of sand is heated to around 500 degrees Celsius using a small amount of low-cost electricity via resistive heating. The superheated air is then stored within the sand and, if untouched, can stay that way for months.

So during sunnier times, when solar heat energy is in excess, that surplus is transferred into the battery, which can then be released as required when limited power is available elsewhere. The stored energy can be used in homes, office buildings, and community swimming pools as any other heat energy source. 

Photo Courtesy Polar Night Energy

Local officials expect the impact to be more pronounced in the coming months when colder temperatures creep in, bringing heightened heating demands along with them. “If we have some power stations that are just working for a few hours in the wintertime when it’s the coldest, it’s going to be extremely expensive,” says  Elina Seppänen, city energy and climate specialist. “But if we have this sort of solution that provides flexibility for the use and storage of heat, that would help a lot in terms of expense, I think.”

Polar Night’s creation is expected to be the first of many, as industries like fashion, food and drink manufacturing, and pharmaceuticals all use processed heat that is currently sourced by burning fossil fuels. It has even picked up in the U.S., where the National Renewable Energy Laboratory (NREL) has begun looking into the heat-storing properties in builder’s sand. 

There is no animosity over this in Finland, where experts like Vatajankoski’s Pekka Pasi are happy to be energy trailblazers for the rest of the world. “It’s really simple, but we liked the idea of trying something new, to be the first in the world to do something like this,” said Pasi, the managing director of the Vatajankoski power plant.


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