The Secret to Renewable Energy Storage: Would You Believe Chairlifts?


Storage of renewable energy is the cutting edge of the transition to renewables themselves. While wind and solar technologies have advanced to become competitive with fossil fuels, the possibilities for energy storage lag behind.

In fossil fuel power stations and hydro power plants, the sources of energy are stored beforehand. A pile of coal sits outside the power station ready to be burned as needed. Or a reservoir of water awaits nearby to tumble through the plant’s turbines to generate electricity.

With wind and solar, the fuel can’t be stored because the sun and wind appear intermittently. So to make sure the power generated from these sources can be delivered to the grid in a predictable way at the right time, the energy must be stored somewhere after production.

A pair of solutions

There are a couple of grid-scale ways to do this: pumped storage and batteries.

Pumped storage uses hydro power plants. With a top lake and a bottom lake and a hydro power plant in the middle, the system can be reversed. Rather than water flowing down the mountain to power the generators, it can be pumped up the mountain to store energy so it then can flow back down through the turbines to generate electricity.

That’s about 80% efficient and a good solution. But a hydro power plant costs millions of dollars to build, and can’t be built just anywhere. Then there are lithium-ion batteries – the new golden bullet. They’re flexible and efficient but they come with supply-chain issues.

The world cannot keep extracting precious materials out of the earth to manufacture the batteries ad infinitum.

Gravity energy storage

This week, GristOpens a new window , a digital outlet focused on the environment, reported on a cool idea called “gravity energy storage” to use a kind of chairlift to move sand up a mountain.

Similar to pumped storage, it calls on renewable energy to transport sand to the top of a mountain and then uses the weight of the sand and the force of gravity to turn turbines and generate energy on the way back down. Simple, relatively cheap and feasible. All it needs is an abundant material such as sand to haul up a mountainside and a pulley system that causes the rotation necessary to generate electricity.

A recent report in Toolbox techOpens a new window detailed another, similar idea to use old mine-shafts as renewable storage, hoisting weights up a mine-shaft with renewable energy and then generating electricity by dropping them back down again.

Closed-loop ideas

The beauty of these kinds of solutions is both their simplicity and closed-loop nature. Once built, they can with minimal maintenance keep on going. They won’t degrade like a battery.

There are also rail shuttles that use the same principle with heavy rail cars ascending a hill and generating electricity on the way back down. Another idea, Energy Vault, uses cranes and pulleys to construct and deconstruct a tower made from concrete blocks.

In fact, the chairlift idea isn’t new. In fact, a prototype was built by Energy Cache in 2012. At the time, the investment to continue just wasn’t there. But the market has changed. Now that utilities are serious about renewables, the impetus for kick-starting these technologies exists.

It seems there’s no shortage of ideas and as the demand for energy storage rises, the humble chairlift is set to take its place in the pantheon of renewable energy storage solutions we’ll need to reshape our electricity landscape.