Gravity energy storage elevated to new heights

An innovative new gravity storage system with an “elevator” style building design is a viable solution to global grid-scale energy storage.

Renewables are projected to increase from its current 12% of the global energy supply to 90% in 2050. Yet the widespread use of renewables is challenged by the intermittency of solar wind, we’re not yet at a place where we can store enough energy to avoid these problems.

As renewable energy supply increases around the world, so to is the demfor grid-scale energy storage. It has been projected that the combined global stationary transportation annual energy storage market will increase from today’s baseline of around 600 GWh by a factor of four by 2030 to more than 2,500 GWh.

Today, global energy storage capacity is dominated by gravity-based pumped hydro (90%), followed by lithium, lead zinc batteries (5%), with the remaining capacity alloted to thermal flow batteries, compressed air, flywheels, other gravity-based mechanical systems.

Gravitational potential energy is one of the only viable grid-scale energy storage solutions. Reprinted with permission from Energy Vault

Within the framework of large-scale, grid-level energy storage, gravity-based solutions currently dominate the commercial space. Pumped hydro, for example, is a reliable technology with a rapid response time proven longevity.

It suffers nevertheless from the availability, scalability, cost of suitable mountainous water rich land, low round-trip energy efficiency (70%), carbon-intense construction, the challenge of co-locating solar wind.

Gravity energy storage

I wrote two ASN articles in 2019 about some exciting new developments in storing renewable energy as gravitational potential energy by lifting lowering heavy objects (Gigawatt Electricity Storage Using Water Rocks and Climate Change Will Require Heavy Lifting). At the time, a Swiss private company founded in 2017 that caught my attention was Energy Vault. In a demonstration project built showcased in Switzerland, they showed the first use of cranes to lift lower heavy composite blocks into massive architectures to respectively store release significant amounts of renewable electricity.

Importantly, the composite blocks enable the use of alternative materials to replace environmentally-unfriendly substances like concrete, which accounts for 7-8% of greenhouse gas emissions. In addition, the technology can accommodate the recycling of various pre-existing waste materials, which in return helps large utility industrial companies transform financial environmental liabilities into infrastructure assets to support their transition to a fully circular economic approach.

Grid-scale gravitational renewable energy storage system. Reprinted with permission from Energy Vault

For example, coal bottom ash waste retired wind turbine blades can be re-directed from landfills into the company’s custom-made composite blocks that anchor the gravity-powered systems. By maximizing the use of locally sourced soil, sand, waste materials — including outputs from fossil fuel production — Energy Vault’s supply chain design reduces the impact of greenhouse gases from the transport sector while increasing jobs for local economies.

The result is an end-of-life solution for materials that are difficult to break down can have negative environmental consequences. This beneficial reuse eliminates waste enables the continual use of local resources within the framework of a circular economy.

During lifting, electricity is stored as gravitational potential energy in the blocks, on lowering, the stored potential energy drives a motor generator to regenerate electricity with as little loss as possible to maximize the efficiency of the process.

The technological performance commercial potential of this gravity-based system relative to other new entrants into the energy storage space was not apparent at the time, especially the levelized cost of electricity in $/MWh compared to lithium-ion batteries. Somehow, extremely tall cranes that lift lower massive blocks in huge construction sites did not seem to be a practical global solution to grid-scale renewable energy storage.

Fast forward to today I have changed my mind. As of April 2022, Energy Vault became listed on the New York Stock Exchange, with the breathtaking news of its latest gravitational energy storage system, it is one of the most exciting companies to watch.

In just three years it has established an impressive global reach with its advanced gravity storage system on five continents, with more than US$32B earmarked projects over the next five years.

What has changed to elevate Energy Vault to such great heights?

It’s simple: They have simplified their gravity storage system by integrating the lifting-and-lowering of heavy weights into a familiar “elevator” style building design that is compatible with all international building codes. Plus, they have perfected the manufacturing process of their eco-friendly fully recyclable composite materials.

The Energy Vault system literally can be built anywhere a building can be built. It is scalable on demwith no topological geographical constraints, having flexible modular construction with the capacity to deliver GWs of power over short long enough durations to handle solar wind intermittency shortfalls.

The energy storage system can also withstharsh changeable weather conditions, it is resilient to storage capacity degradation over time, not reliant on carbon intensive mining refining of rare toxic metals, is devoid of chemical fire safety risks.

The round-trip efficiency or the proportion of stored to retrieved electricity is currently 83-85%, rather close to that of comparable power rating lithium-ion batteries, which hold 87-89%. Most importantly, it is purported to offer a lower levelized cost of electricity than any competing technology, particularly 60% of of today’s lithium-ion batteries — by 2025 this is projected to drop to 51%.

I believe this is one of the most promising sustainable solutions to global grid-scale renewable energy storage. It almost certainly will prove to be an indispensable piece of the circular economy puzzle, having a positive ripple effect on creating new clean technology industries jobs, avoiding environmental liability, ameliorating climate change, mitigating global warming.

Now that’s what I call heavy lifting!    

Written by: Geoff Ozin Athan Tountas

Solar Fuels Group,

Feature image: The Energy Vault Resiliency Center (EVRC). Reprinted with permission

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