Gravity never goes away, and that’s a powerful tool in the world of renewable energy, often marred by the ebb and flow of wind, tide, and sunshine. A number of companies have invested considerably in gravity batteries, and boast impressive figures regarding energy efficiency and power storage.

Scottish start-up Gravtricity claims to be able to power 63,000 homes through an hour of operation of its 20MW facility, while GravitySoilBatteries aims to provide up to 30,000kWh of storage at a system efficiency of 85%. It remains to be seen, however, if projects such as these can scale up to be a more integral part of the world’s clean energy mix.

Unlike fossil fuels, solar and wind can’t provide an uninterrupted stream of energy. After all, the sun sets and winds die, but scientists and engineers have developed myriad ways to store that renewable energy for when the grid needs it. One idea is to supplement lithium-ion batteries with iron-air batteries that could charge our homes via rust (yes, rust), or transform existing coal-fired power plants into nuclear ones. But another much talked about technology is what’s known as “gravity batteries,” which use regenerative braking and, well, gravity to send energy to the grid.

The big problem is exactly that — they’re big — making them unfeasible (and unattractive) for certain areas. However, earlier this month, scientists revealed a gravity battery that takes advantage of vestiges of dirty energy’s past by using millions of abandoned mines worldwide to store energy.

The process uses gravitational energy to fill batteries during peak conditions when energy derived from renewable sources is plentiful. Then, if demand for power outstrips that which renewable sources can provide, this stored energy can be released, providing power if, for instance, the sun does not shine, or the wind does not blow.

Gravity batteries could prove integral to the world’s clean energy mix, especially in relation to other forms of renewable power storage. When compared to lithium-ion batteries which currently dominate the stored energy landscape, the environmental footprint of gravity batteries is light, with figures suggesting that the cost per MWh associated with gravity batteries could be half as much as their lithium counterparts, even factoring in maintenance, construction and running costs.

However, continued innovation in the gravity batteries sector means that, for the time being at least, there is optimism regarding the future of the process.

Our work with energy storage

Universal Kraft has been working with compressed air storage solutions for several years, combining renewable energy production, through wind or solar, with an energy storage system of compressed air in the ground or in tanks. Currently, together with partners, we are developing a new technology in which a compressor is used to pump air into the ground or tank for storage, that is then reversed when the energy is needed, into a generator. Discover our projects here.