Imagine a gigantic brick, packed full of highly compressed dirt. As big as a pickup truck but — at 24 tons — about five times heavier. An elevator powered by solar panels or wind turbines hoists it over 300 feet up the side of a huge building. A trolley stows it inside, but it’s not alone. An automated system lifts and stores hundreds more bricks, like giant Pez candies, as the sun shines and the wind blows.
Now imagine the building’s control system lowering those hundreds of bricks one by one, spinning electrical power generators in the process. They drop down every evening just as demand for power peaks but solar panel output fades away.
In effect, the brick-filled building is a giant battery that stores energy with gravity instead of chemistry.
Gravity batteries are a potentially important solution to a critical problem with the green energy revolution: making sure electricity is available when we need it, not just during the times when sun and wind supply it.
And it isn’t just an idea. With two sites under construction — one in Rudong, China, just north of Shanghai, and the other in Snyder, Texas, about 250 miles west of Dallas — startup Energy Vault will begin seriously testing the viability of the gravity storage technology. An earlier pilot generated 5 megawatts of power, but these two facilities and expected successors will show whether gravity storage is economical and efficient enough to work at large scale.
Power when the sun goes down
You may think putting solar panels on your roof will help fight climate change, but without some form of energy storage in your home or on the grid, you’ll likely rely on carbon dioxide-spewing gas and coal power plants to run your home’s lights, TV and dishwasher as the sun sets.
Energy Vault tested its technology at a smaller scale in Switzerland, where the 170-person company is headquartered. Its two EVx systems under construction are much bigger. The Chinese system, built for waste management and recycling company China Tianying, is in a 400-foot-tall building and will have an energy storage capacity of 100 megawatt-hours. That’s enough to power 3,400 homes for an entire day, and the system should be complete by June. The Texas system, in a 460-foot-tall (but narrower) building, will provide power company Enel with 36MWh of capacity.
Solar panels and wind turbines now generate power more cheaply than coal and natural gas plants, making them a clear choice in the push to replace fossil fuels. Solar power costs dropped 83% from 2009 to 2023 and wind costs dropped 63% over the same period, according to tracking from investment advisory and asset management firm Lazard. But in many parts of the country, new solar panels often just supply a glut of power during the middle of the day without helping in the evenings.
The mismatch between power production and power usage is responsible for the infamous “duck curve
,” a graph with a birdlike shape showing the disparity increasing with each pass
