Gravity batteries: could lifting weights power the grid?

Renewable energy is booming, but intermittency remains a core challenge. Storing excess energy to cover demand when the sun is not shining can now happen in many ways; one you probably haven’t heard of is harnessing gravity.  

In fact, pumped hydro storage has exploited this principle for many decades, pumping water uphill when electricity is cheap and letting it flow back downhill through a turbine when needed. However, a mountain, a reservoir, and a lot of water aren’t available everywhere. 

Yet gravity is ubiquitous, and there are various ways to exploit it to store excess electricity, including cranes, rail cars, and decommissioned mine shafts. Can gravity batteries be a credible option in the energy storage puzzle? Let’s dig into it in this new episode of Green Tech Decoded. 

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How do gravity batteries work? 

The working principle is simple and similar to what was explained for pumped hydro storage. When renewable power is abundant, surplus electricity powers motors to lift heavy weights – such as concrete blocks – to a higher elevation. 

This way, electrical energy is converted into gravitational potential energy. In other words, that energy doesn’t vanish, but can turn into electricity again when the mass descends in a controlled way, so that its motion drives a generator. And mechanical energy becomes electricity again. This can be done with tall towers in which weights move up and down. 

As physics laws prescribe, the amount of energy that can be stored is equal to: mass x gravity x height. The heavier the weight and the taller the lift, the more energy can be banked.  

Who are the main developers of gravity batteries? 

Two companies are worth highlighting: the Chinese Energy Vault and the Scottish Gravitricity. 

Energy Vault takes the idea of pumped hydro and replaces it with concrete blocks, moving them on a tall crane structure. The company's blocks aren't just poured concrete — some are made with waste materials like coal ash, so the system can also use industrial byproducts that would otherwise go to landfill. Its first commercial-scale plant, at Rudong in China, proved the concept works at grid scale.

Gravitricity entered liquidation last year, with less than £8,000 in assets. However, its concept is still worth highlighting. Their GraviStore system suspends a massive weight — up to 12,000 tonnes in its largest configuration — on steel cables inside a vertical mine shaft, using winches similar to those already used to move equipment and workers in and out of mines. This means no new infrastructure is needed, but what’s already there can be repurposed.

What are the pros of gravity batteries? 

This concept has some appealing advantages. 

• No critical minerals. Unlike lithium-ion batteries, gravity batteries don’t depend on critical minerals such as lithium, cobalt, and nickel, or on any other material whose supply chains are concentrated in a handful of countries. Blocks can be made not only from concrete, but from waste materials and even composites mixed with ash. In other words, there are many ways to create weights. 
• Minimal degradation. A steel or concrete block doesn’t lose capacity the way a regular battery cell does after thousands of cycles. Energy Vault claims a 35-year lifespan for its concept. 
• A second life for decommissioned infrastructure. This is probably the most intriguing argument in favor of gravity batteries, especially for mine shaft systems. Decommissioning a mine shaft means filling it, sealing it, and restoring the site. For operators, turning a soon-to-be-decommissioned mine shaft into a gravity battery means turning a liability into an asset and preserving jobs in mining communities. Mine operators across Europe are considering the idea. 

What are the cons of gravity batteries? 

As with any other developing technology, there are some caveats, too. 

• Low energy density. This is one of the main downsides, as the mass required to store large amounts of energy is immense. Take a 100 MWh system — roughly enough to power around 10,000 average Dutch homes for a full day. Using a tower height of about 120 meters (within the range of Energy Vault's real towers) and accounting for round-trip losses, storing that much energy as lifted mass requires about 380,000 tonnes of material — the equivalent of about 38 Eiffel Towers. The same amount of energy could be stored in 20 Tesla Megapacks – nearly 500 times less mass for the same capacity. Gravity batteries are built for the grid and sited not in urban areas, yet the problem remains. 
• Site constraints. Space and permitting procedures for these tall structures aren’t straightforward. Placing these systems requires considerable space, and ensuring compliance with safety and zoning regulations can be lengthy. In the mine shaft use case, careful consideration is required for each site, as factors such as depth, structural condition, and proximity to the grid are key. 
• Still a financial rounding error. The market is still small. Industry research firms' 2026 estimates range from around $160 million to over $750 million, with one outlier report putting current value closer to $1.6 billion. The market is too thin and unpredictable at the moment. Gravitricity's voluntary winding up is an example of how immature the market is. 
• Energy Vault’s pivot. The company that built the first commercial gravity tower has increasingly shifted its own business toward conventional lithium battery storage (BESS) projects in the US and Australia. Its gravity-block technology now mostly moves forward through licensing partners in China rather than Energy Vault building towers itself — a signal that even gravity storage's own pioneer sees lithium as the safer bet for most markets, at least for now.

Where does the technology stand now? 

China is ahead. Beyond the Rudong project, a second Energy Vault site in Zhangye, Gansu — 17 MW / 68 MWh, paired with wind generation — is operational, and China's National Energy Administration has designated several of these projects as official pilot demonstration sites.

Gravitricity was testing its mining variant in Europe, particularly at the Pyhäsalmi project in Finland. Notably, in 2021, it pivoted to include hydrogen and heat storage technologies in its energy storage systems to store gas as well. Its assets and patents went on sale through financial services firm Hilco. The website reads that the package has been sold, yet the buyer’s name hasn’t been disclosed. 

What to expect from gravity batteries? 

Gravity storage won’t replace lithium-ion; rather, it aims to fit into the long-duration, grid-scale storage segment, stashing excess power for hours. It can be a promising alternative in areas where supply chain disruptions, degradation, or fire hazards make conventional batteries risky. Even more so in former mining sites, to give new life to existing infrastructure. 

Physics works — gravity will still be there for the time being — economics have to follow, and possibly open up opportunities for niche segments. At this time, gravity storage is not really attractive, but it could still play a role in the future.