To Store the Wind and Sun, Energy Startups Look to Gravity

In the Alpine town of Arbedo-Castione, Switzerland, an electric-blue, 400-foot-high crane with six heads lifts a block of compacted soil into the air and carefully adds it to the top of a stack.

Later, the crane will reverse that process, generating power as gravity lowers the block back toward the ground.

Energy Vault, the company that built the contraption, believes it could help the renewable-energy industry confront its most intractable problem: storing up energy against the surges and lulls that characterize renewables like wind and solar.