Generally, when one pictures a battery, one imagines the lithium-ion battery in various high-tech forms.

Yet in 2022, Polar Night Energy launched the world's first commercial sand battery, capable of storing 500-600ºC in heat energy for months. Compare this to a standard lithium battery that can only hold energy for a few hours!  

Now, Polar Night Energy, in collaboration with the heating company Lovisan Lämpö, will launch a sand battery 10 times the size and capable of storing up to 100 megawatts hour of heat.

This battery will eliminate the need for oil-based energy for the entire town of Pornainen, Finland, and keep 160 tonnes of carbon dioxide out of the atmosphere annually. 

What is a Sand Battery?

The idea for a sand battery is simple: storing large amounts of heat in a certain material for later use.

This technique dates back centuries. Ancient Egyptian homes were made of sand mixed with silt and straw that would capture the heat of the hot desert sun -- and then release it slowly during the cool nights.

Many Native Americans used Adobe in construction for the same reason. They would also store heat from campfires in rocks wrapped in leather skin and use these rocks for heating their beds at night. This ancient wisdom can now be applied to modern sustainable solutions through sand batteries.   

Commercial sand batteries are simply large insulated steel silos filled with sand and pipes for transferring heat, along with fans and steam generators on the outside. The advantage of sand is its ability to store large amounts of heat in a small volume, its abundance, and its low cost. Other sand-like materials can also be used.  

How Do They Function?

Sand batteries are charged using electricity generated from renewable sources like wind and solar.

• The electricity powers a heater that heats the air in the battery.
• A fan circulates the hot air through a closed-loop air-pipe system, heating the sand up to a maximum of 600ºC.
• To recover the stored heat, cool air is pumped in, and in a reverse heat exchange, the air gets heated and is piped to homes and businesses. 

The main purpose of sand batteries is to serve as reservoirs for excess wind and solar power and to conserve surplus energy when demand is low. They can provide heated water as well as heated air to homes and industries that would otherwise use fossil fuels. The heat can also be converted back to electricity using a steam turbine. 

Looking To The Future

With the environmental and ethical cons of mining for lithium batteries, investors and companies are looking for alternatives, and sand batteries are one of them.

According to the Washington Post, more than $900 million has been invested in clean storage technologies in the past three years, a number that is expected to reach $3 trillion by 2040. This money is being directed towards various small companies that are investigating natural batteries, from rock-based systems in Sardinia to massive bricks in Sweden, to molten salt in Denmark.

There are obstacles to overcome before this technology can be adopted widely. It remains to be seen whether natural batteries can be a steady source of energy. Furthermore, because it’s an emerging industry, natural battery projects will need to be constructed from scratch, meaning only developed countries can afford to implement them.

Despite this, sand and other natural battery solutions are an exciting step forward towards a green future. 

Sources: Washington Post, BBC, ABC, polarnightenergy.fi, Popular Mechanics