How incredibly simple technology can accelerate the transition to net zero emissions.

To balance out the intermittent power supply from wind and solar, we need to construct large energy storage facilities. Surprisingly, the best solution might be inexpensive, simple ideas such as heating bricks and raising weights.

Located 450 kilometers north of Helsinki, Finland, is a decommissioned mine. Despite its remote location, it is being closely monitored because it seems poised to revolutionize our energy systems – but not for the reasons you might expect.

The Pyhäsalmi mine used to produce wealth from zinc and copper, but it is now poised to harness the power of gravity. As the deepest metal ore mine in Europe, it is an ideal location for what is known as a gravity vault. The UK-based company Gravitricity plans to lower a heavy weight down a mine shaft and connect the mechanism to a generator. It will store power as potential energy by pulling up the weight and generate it again by letting it fall.

If that sounds surprisingly simple, that is exactly the point. Governments are grappling with the massive challenge of the intermittency of renewable power: how to keep the lights on when the wind doesn't blow and the sun doesn't shine. So far, they have largely focused on expensive technologies like hydrogen, nuclear power, and lithium-ion batteries. But what if we could solve the intermittency problem – and also reduce costs and emissions – with far more basic methods?

The gravity vault could be just the beginning. Other companies are developing energy storage methods involving such low-tech components as salt, sand, water, and heated bricks. These seemingly...