This Sand Battery Is An Audacious Attempt To Store Green Power

Engineers in Finland may have discovered a cheap and effective way to get the most out of their country's wind and solar power systems. Polar Night Energy claims to have constructed "the first commercial sand-based energy storage" in the world, and their facility is currently operational.

Renewable energy projects are becoming more and more popular for several reasons. Many scientists and political figures see renewable power from sources like solar and wind as a vital tool in the fight against climate change. Several countries have pledged to drastically cut emissions, while others are aiming to become entirely carbon neutral in the coming decades. Another factor is related to the current geopolitical situation. Several European countries, including Finland, rely on Russian oil and gas exports to meet their energy needs. Following Russia's invasion of Ukraine in February 2022, several European nations are looking for ways to cut back on their need for Russian fossil fuels. This isn't a one-way thing, Russia has also used its oil and gas reserves as a way to pile political pressure on several countries. Finland, which built the sand-based thermal storage battery, has seen its supply cut off after joining NATO (via NPR).

The trouble with renewable energy sources

While renewable energy comes with clear benefits, there are also some pretty major downsides. You can burn gas, coal, or harness the power of the atom 24 hours a day, seven days a week, 365 days a year. This means the energy generated from these sources is both constant and reliable. On the other hand, the wind doesn't always blow, and the sun doesn't always shine. So if you want constant power from these sources alone, you need to find a way to store the energy you harvest when the conditions are ideal.

Again, this may be a larger problem in places like Finland. On the equator, days are of a fairly equal length all year round. The further north or south you get, the more things change with the season. Some parts of Finland will get constant sunlight for several months during the summer — in fact, Visit Finland claims that when you're in the Arctic Circle, the sun won't set at all between May and August. While that doesn't mean you get 24 hours of peak solar generating conditions, you will be able to generate some power constantly during those months. To balance this out, there are a few months of total darkness in winter where the sun won't rise at all. Wind-based power systems are even less predictable, you get windy periods and you'll get times where there's barely a breeze.

So what you need is a way to store that energy. Most batteries use lithium, which is expensive and quite limited in what it can store. This means a cheap, easy, way of storing excess renewable energy is a game-changer when it comes to the practicality of climate-friendly power.

How the sand battery works

The idea behind the sand battery is quite simple. Use a large silo of cheap, low-grade sand to store thermal energy created from renewable sources. This thermal energy can be made when there is an excess of one type of power — like solar in the middle of summer. That thermal energy can then be released as needed and used to heat water which is then used to heat homes and public buildings.

The sand is heated to 500 degrees Celsius, or 932 degrees Fahrenheit, by a process known as resistive heating. It's the same way an electric stove or fire works, the current is put through a resistive piece of material, and heat energy is given off. Hot air is then generated in the big sand pit and moved around in the sand by a heat exchanger. The battery's designers claim that the sand can hold on to the heat for "several months," which makes it an ideal medium for a thermal battery (via BBC). The Finns aren't the only ones who have spotted the potential of sand-based batteries, the US National Renewable Energy Laboratory is working on one too.

Cost-effectiveness is also central to the battery's design. The low-grade builder's sand used is ideal for this purpose and incredibly cheap when compared to metals like lithium. Heating homes with an array of solar batteries is also more cost-effective than running a power station through the winter. There is a downside, if you want to pull the energy you've stored in a sand-based thermal battery back out as electricity instead of just heat, the battery's efficiency drops drastically. However, although it isn't perfect, the sand-based thermal battery is a big step forward, and energy storage solutions like this could be the key to a carbon-neutral future.