Renewable energy: How incredibly simple tech can supercharge the race to net zero

Some 450 kilometres north of Helsinki, Finland, lies a decommissioned mine. Despite its remote location, it is being keenly watched because it looks set to play a role in revolutionising our energy systems – though not for the reasons you might suspect.

The Pyhäsalmi mine used to yield wealth from zinc and copper, but it is about to monetise the power of gravity. As the deepest metal ore mine in Europe, it is an ideal spot for what’s known as a gravity vault. UK-based company Gravitricity plans to dangle 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, then generate it again by letting it plummet.

If that sounds surprisingly simple, that is exactly the point. Governments are wrestling with the epic 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 problem of intermittency – and cut bills and emissions too – with far more rudimentary methods?

The gravity vault could be just the start. Other companies are developing energy storage methods that involve such technological marvels as salt, sand, water and hot bricks. These disarmingly…