In some areas, it’s now cheaper to build a new wind or solar farm than to run an old coal plant. But when the sun isn’t shining and the wind isn’t blowing, storing that power is still relatively expensive—and solutions like batteries and dams create their own environmental challenges. Lugano, Switzerland–based Energy Vault uses gravity to solve the problem through a new system that raises and lowers massive low-cost bricks, relying on basic principles of energy conversion to store and release energy along the way. “Now you can couple [solar power] and low-cost wind with our storage and for the first time replace fossil fuels with renewables 24 hours a day,” says cofounder and CEO Robert Piconi. Indian utility Tata Power, Energy Vault’s first announced customer, will be installing one of the towers later this year.
1. Lifting Bricks
When a solar farm produces extra energy during the day, the Energy Vault system uses that power to run motors that lift the huge bricks and stack them on top of a tower, storing energy through the elevation gain. The design is modular, but a typical tower is roughly the height of a 30-story building.
2. Energy Release
When the grid needs power—say, in the evening—software directs arms on the crane to lower the bricks, spinning generators to create electricity. The energy then flows into the grid. An average-size system can serve around 3,400 homes each day. When demand is low, the software automatically adjusts to discharge less energy.
3. Recycled Parts
Each 35-metric-ton brick can be made from concrete debris that would normally end up in a landfill. At a coal plant shifting to renewable power, the bricks could be made from coal ash. Energy Vault can also use a new process to make bricks from dirt on-site.
4. Quick Setup
Unlike a battery factory, which can cost more than $1 billion and take years to build, each tower can be constructed quickly. Standard cranes arrive from manufacturers within a few months and require only two or three weeks to set up. The bricks can also be produced quickly. “A big benefit of our solution is the scalability,” Piconi says. In the first few months after the company launched, in November 2018, it was in talks with prospective customers about 1,200 potential towers.