It’s not the battery as we usually imagine it: it’s gravity. This system uses the force of gravity to store energy and takes a few seconds to release it. According to the developers, their solutions will find wide application in the renewable energy sector.
how does gravity work
The prototype is located in the port area of Leith, Edinburgh, Scotland. The structure has a 15 m high lift shaft, however, there is no lift. Instead, the weight of 50 tonnes of iron has been fixed on steel cables.
A series of electric motors slowly lift the weight to half its height. At this point, the device represents a giant “battery” of potential energy, thanks to gravity. When needed, in fact, the weight is reduced and the motors become generators producing 250 kW of energy.. This energy conversion is completed in 11 seconds.
Such a system mimics a traditional hydroelectric storage and power generation plant. However, the main difference is that a hydroelectric plant requires a specific landscape, a complex authorization system, and a particularly expensive infrastructure. On the other hand, this plant has a particularly simple design and makes it possible to exploit, for example, existing mines.
start up, which currently employs 14 people, plans to build the first industrial scale plant in 2023 with a 1 km drop and metal load that will enable a maximum output of up to 4 MW.
A New Rival for Lithium Batteries
Oliver Schmidt, a clean energy consultant and visiting researcher at Imperial College London, says the system has inherent advantages over lithium batteries. The first, and also the main, is that a lithium battery can charge and discharge a limited number of times due to the loss of capacity. This, he says, usually happens over a few years. The mechanical components that make up a gravity system can easily last for decades without special modifications.
Gravity’s lead engineer Miles Franklin also said that the effect of his system is much less than that of its “chemical” counterpart. The production of iron is much less effective than extracting metals and rare earths for batteries..
Gravity, how much does it cost me?
Oliver Schmidt himself produced a report using Gravitricity’s economic data showing how, including construction, operating costs and maintenance, the system is cheaper than its lithium counterpart.
The cost of gravity for a 25-year project is $171/MWh. According to calculations, in fact, the cost of a similar lithium storage project is $367/MWh.
gravity and hydrogen
Gravitytricity’s future plans include the idea of combining gravity storage systems with pressurized gas storage systems.. The company’s founder, Indeed, Martin Wright says that “the hydrogen economy of the future will need to find cheaper and safer ways to store it when it is needed.” According to Wright, each gravity well would be one large sealed pressure vessel. It will be a safer and cheaper system than existing hydrogen storage systems.
a bit of realism
Gravity isn’t the only solution for storing energy using gravity. In fact, there are many companies that work and research in this area. Gravity Power in California, where thanks to renewable energy, water is pumped under a piston, lifting it. When energy is needed, the piston is allowed to break free under its own weight, turning the water into a hydroelectric generator. New Energy Let’s Go, a German company, uses a similar system. Swiss Energy Vault uses a multi-arm crane with a motor generator to stack a 120-metre-high tower made of hundreds of 35-ton bricks. The height of this tower varies according to the demand for energy.
Gravity-based energy storage technology is still very immature, says Oliver Schmidt. In fact, companies in this sector have made little progress. Energy Vault only raised $110 million in funding in 2019 and only had its first commercial development in 2021.
Small natural gas plants are still the best solution to offset fluctuations in energy demand. If carbon-free energy policies are not encouraged, gravity storage systems will not be economically sustainable. A rather “serious” situation, needless to say.
Graduated in Chemical Engineering. Qualified Engineer since 2018.
First Process Engineer and Consultant on Electric Vehicles and Lithium Batteries, now a PhD student in Industrial Engineering at the University of Salerno.
The author on #EnergyCuE from May 2019.
Passionate about technology, science, Japan, energy and all round sustainability.
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