Energy Innovation: Could Sand Power the Next Battery?
The world is in the midst of a renewable energy transition being propelled forward at a breakneck speed by the rising costs of oil and gas, climate change impacts and the increased availability of alternative technologies. One of the most significant challenges to the widespread adoption of renewable energy is providing a steady supply of energy.
Solar and wind energy are intermittent sources and work well as part of an all-inclusive renewable energy portfolio. However, energy storage solutions are needed to bridge the gap when solar power isn’t available or wind turbines stop producing.
One innovative solution has recently emerged: using sand as a battery to store excess energy produced by solar panels and wind turbines. A low-cost battery that doesn’t rely on mining precious metals could help the world overcome some challenges of transitioning to a green energy economy.
What Is a Sand Battery and How Does It Work?
A sand battery stores excess energy as heat using sand or sand-like materials. The heated sand can be stored for several months and later used to heat homes directly or power electricity-generating turbines. The cooled sand can be returned to storage, where it repeats the process again and again.
Polar Night Energy, a Finland-based company and leader in sand battery technology, uses electricity generated from solar and wind power to heat sand to 600 to 1,000 degrees Celsius (1,120 to 1,832 degrees Fahrenheit). The heated sand is then stored in an insulated silo until needed.
The first commercial sand battery developed by Polar Night Energy went online in 2022 and is connected to a heating network to heat the homes and swimming pools in a small town in western Finland. This project provides 100 MW of electricity and has a storage capacity of 20 GWh.
Most homes in Finland are warmed via district heating systems that historically relied heavily on coal and natural gas. And although their reliance is decreasing, in 2019, just under 50 percent of district heat was still produced using fossil fuels. Using sand heated with renewable energy to heat homes combined with improved home energy efficiency could further reduce Finland’s reliance on fossil fuels.
Another pilot project developed by the U.S. Department of Energy’s National Renewable Energy Laboratory heats sand particles to 1,200 degrees Celsius (2,192 degrees Fahrenheit) by feeding them through an array of electric resistive heating elements. Unlike the Finnish project, the heat stored in the sand is not used to heat homes directly. Instead, the heated sand is fed through a heat exchanger and used to heat a gas to drive a turbine and generate electricity for the grid. This project can store 26 GWh of thermal energy.
The Benefits of Using Sand as a Battery
The benefits of using sand as a battery are numerous. Lithium-ion batteries are currently the most commonly used technology for energy storage. These batteries rely on finite resources, such as lithium and cobalt, which must be mined from the earth. Lithium-ion batteries are also highly flammable if damaged or recharged improperly.
Sand batteries, on the other hand, eliminate the need to mine these critical minerals. Sand is abundant, inexpensive and resistant to fire and explosion, making it a much cheaper and safer alternative to other battery materials.
Also, unlike lithium, sand does not break down over time. It can also be heated and cooled repeatedly. Should the sand eventually need to be replaced, used sand can be safely recycled for other uses.
In addition to the materials used, sand batteries have several other advantages. First, they can be easily scaled up or down in size as needed, making them ideal for small-scale commercial projects and distributed energy applications like residential solar installations.
Second, because of their flexibility, energy storage systems using heated sand can be sited nearly anywhere, including below ground. As countries transition to renewable energy, retired coal- and gas-fired power plants with existing connections to the electrical grid could easily be converted into large-scale sand battery facilities.
Finally, sand batteries are highly efficient. Heat stored in the sand battery can be used directly or converted into electricity with up to 95 percent efficiency.
The Challenges of Transitioning to a Sand Battery Economy
The sand battery is a promising technology, but specific issues must be addressed before it becomes viable for mass energy storage.
Sand is the most mined element in the world. It accounts for 85 percent of all mineral extraction and often comes at a steep environmental cost. Sand is used to produce concrete and hydraulic fracturing to extract natural gas and crude oil from rock formations. It is also used as a base for asphalt roads, for land reclamation and for glass manufacturing. Sand mining is the least regulated mining operation.
Should the world look to sand batteries to meet its decarbonization goals, sand could become even more valuable and over-extraction could become an issue. Countries must implement regulations to ensure sand is mined responsibly. Rivers and coastal ecosystems need to be protected and small islands, already at risk of coastal flooding as sea levels rise, need to be protected from being eliminated.
The Future of Sand Battery Technology
In addition to providing electricity to the grid and heating buildings, sand batteries can provide a heat source for industrial and chemical processes. These processes cannot rely on intermittent renewable energy sources, so adding sand batteries would significantly reduce the carbon footprint of these processes.
Sand batteries are an exciting and innovative technology that holds promise for the green energy transition. Although there are still challenges to overcome before sand batteries become a widespread energy storage solution, they offer a promising and inexpensive alternative to current battery materials. With sand’s abundance, low-cost and fire-resistant properties, it may soon be powering homes and businesses worldwide.