As the world actively seeks sustainable energy solutions, the importance of energy storage technologies is becoming increasingly evident. Among emerging storage methods, gravity batteries are gaining attention and may play a vital role in the future energy landscape.
How Gravity Batteries Work
The fundamental principle of a gravity battery lies in the conversion between gravitational potential energy and electricity. Simply put, when the power grid has a surplus of electricity, this excess energy is used to lift heavy objects to a higher elevation, storing energy as gravitational potential. When electricity demand increases, the elevated weights are released, converting potential energy into kinetic energy as they fall, which in turn drives a turbine to generate electricity that is fed back into the grid.
A classic example is pumped-storage hydropower systems, which can be considered a broad form of gravity battery. During off-peak hours, water is pumped from a lower reservoir to a higher one, storing energy as gravitational potential. During peak hours, the water is released back down, spinning turbines to generate electricity. This method is widely adopted around the world—approximately 97% of large-scale energy storage capacity today comes from pumped-storage, with a total output capacity of around 180 GW out of the global total of 8.9 TW.
With the advancement of new technology, modern gravity batteries are exploring the use of solid masses instead of water. For instance, excess solar or wind energy can be used to lift heavy concrete blocks or iron pistons. When energy demand peaks, these materials are released in a controlled sequence to produce electricity through their descent.
Types of Gravity Battery Technologies
(1) Building-Integrated Gravity Batteries
Some innovative approaches are focusing on transforming skyscrapers into gravity battery systems. One such concept involves retrofitting elevator systems to lift heavy weights or water tanks to upper floors during off-peak times. During peak electricity hours, these weights descend, converting gravitational potential into electricity via pulleys, actuators, and regenerative braking systems. For example, Skidmore, Owings & Merrill LLP (SOM), the firm behind the Burj Khalifa, is exploring using motors to lift large stone blocks, then harvesting energy from their descent.
(2) Underground Gravity Energy Storage (UGES) in Abandoned Mines
In 2022, scientists from IIASA in Austria proposed the UGES concept. This system uses disused mine shafts where elevators lift sand-filled containers to store energy and release them to generate electricity through regenerative braking. Motors/generators installed on both sides of the shaft handle the conversion. Sand is loaded at the surface, unloaded at the shaft’s bottom, and returned empty. When surplus electricity is available, the sand is transported back up using conveyors and dump trucks. Scientists estimate UGES could provide 7–70 TWh of global storage potential, with countries like China, India, Russia, and the U.S.—all with many abandoned mines—offering great implementation prospects.
(3) Commercial Gravity Battery Projects
Swiss company Energy Vault has made significant progress, integrating the first commercial gravity battery system into China’s grid in 2024. Located in Jiangsu Province, this system has a capacity of 25 MW with an investment of 650 million yuan. The building measures 120m long, 110m wide, and 148m high, containing 12,600 gravity blocks, each weighing 25 tons. The system lifts these blocks during surplus power and lowers them during demand peaks. Each lifting or lowering process takes 4 hours; at 2.5 MW output, this generates 100,000 kWh with a round-trip efficiency of around 85%, higher than the 81.06% average of chemical batteries.
Advantages of Gravity Batteries
(1) Environmentally Friendly and Clean
Gravity batteries involve no combustion or chemical reactions. They emit no greenhouse gases and cause no pollution, making them a fully clean and renewable energy storage option. Compared to fossil fuels, their environmental benefits are significant, supporting global efforts to combat climate change.
(2) Fewer Geographic Limitations
Unlike pumped-storage, which requires specific geographical conditions (like mountains or large reservoirs), gravity batteries are more flexible. Urban high-rise buildings and abandoned mines can serve as infrastructure, allowing broader deployment across varied terrains.
(3) Stable Energy Storage
Unlike chemical batteries, which degrade over time or due to environmental conditions, gravitational energy is inherently stable. Once a weight is lifted, it can reliably store energy until needed, offering consistent and dependable support for the power grid.
(4) Cost Advantage Potential
Repurposing existing infrastructure, such as abandoned mines, can significantly lower construction costs due to pre-existing facilities and grid connections. Moreover, as the technology matures and scales up, per-unit storage costs are expected to decrease, potentially making gravity batteries more cost-competitive than some chemical solutions.
Challenges Facing Gravity Batteries
(1) Retrofit and Maintenance Costs
Transforming existing buildings or mines into gravity batteries requires major investments in system installations and structural assessments. For instance, modifying elevator systems in high-rises entails not only replacing equipment but reinforcing building structures to bear additional weight. Regular maintenance of mechanical systems adds to ongoing costs.
(2) Conversion Efficiency Loss
Though some systems have achieved high energy conversion rates, losses still occur through friction, mechanical resistance, and operational energy use. These reduce overall system efficiency and impact economic feasibility.
(3) Technological Maturity and Market Acceptance
As a nascent technology, gravity batteries face hurdles in terms of system reliability, control precision, and market readiness. Public and industrial acceptance needs time to grow, and widespread commercial adoption will require further education and demonstration.
Future Prospects of Gravity Batteries
Despite challenges, gravity batteries hold strong promise in the evolving energy landscape. As the demand for clean energy rises and energy storage requirements grow, gravity batteries may become a vital solution.
On one hand, with the increasing share of intermittent renewables like wind and solar, gravity batteries offer a way to store excess energy and smooth fluctuations, enhancing grid stability and maximizing renewable utilization.
On the other hand, ongoing innovation will drive performance improvements and cost reductions. In the future, gravity batteries may integrate with other storage technologies, like chemical and hydrogen storage, to form a hybrid ecosystem. With governments around the world intensifying support for sustainable energy development, gravity batteries are likely to gain more momentum and occupy a more prominent place in the global energy mix.
