FEATURE | RENEWABLE ENERGY
LIFT WEIGHT, SAVE ENERGY
Gravity batteries are a technology that may ride to the rescue of intermittent renewable sources. Hoists are central to the system. One of the major bottlenecks in the transition to sustainable energy
of course produces only during the daytime; the second is strongly dependent on the weather. Storing energy in conventional chemical batteries is problematic. Lithium-ion technology is at present the most widely used for large-scale storage (as well as for cell-phones and the like); but it is expensive, and mining lithium and rare earths used in other types of battery can be environmentally destructive. Stored hydrogen is an alternative that is being considered: peak-generated electricity is passed through water to split it into hydrogen and oxygen; the hydrogen is compressed and stored under 200 atmospheres pressure, in lined underground rock shafts, to be used as emissions- free fuel when needed. Several companies are working on the technology. Gravity storage is another developing technology. It is in principle
very simple: electricity at a time of surplus is used to lift a heavy weight; at time of peak demand the weight is allowed to fall slowly, generating electricity as it does so. Such systems using pumped water as the weight are well-established. Dinorwig, in North Wales, began operating in 1984. Its six turbines
give an installed capacity of 1800 MW, capable of very rapid response and drawn on at times of peak demand. Pumped hydro currently makes up more than 94% of world power storage. It is generally limited to areas that have high mountains and plentiful water. Recent interest has focused on using not water but solid weights as the storage element; they are raised and lowered either inside specially- constructed buildings, or up and down repurposed mineshafts. and hence greater energy storage. Exhausted deep mineshafts are present in many locations, often close to large centres of population. The technology obviously depends on the hoists that are used to raise and lower the weights. Here hoist technology can prove itself central to the transition to sustainable energy. The same hoist that uses electricity to raise the weight simply operates in reverse to generate electricity when turned by the weight of the load, and that unlike with conventional chemical batteries, there is no gradual leakage of stored energy over time, and gravity batteries can operate for decades without any loss of performance. A leading company in developing gravity storage is UK- based Gravitricity. During 2021 they successfully constructed, suspended by steel cables from a standard hoist by Huisman. Since then they have progressed further. In December 2023,
Gravitricity signed an agreement with Swiss mining technology company ABB to accelerate the development of the system towards commercial adoption in former mines. Called GraviStore, the aim is characteristics of lithium-ion batteries and pumped hydro storage. ABB is a market leader for mine hoists, with an installed base of
more than 1,000 hoist solutions worldwide. ABB will collaborate by providing research and development, product development
and engineering teams specializing in the design, engineering and operations of mine hoists for gravity batteries and mechanical, electrical and control technologies for hoisting. The aim of commercialising the technology is bearing fruit. In
February this year Gravitricity inked a deal to install its gravity energy storage system in a 1,444-metre deep mine near the Finnish deep auxiliary shaft is to be transformed into a 2MW capacity use of the system in Europe. “As the world generates more electricity from intermittent
renewable energy sources, there is a growing need for technologies which can capture and store energy during periods of low demand and release it rapidly when required,” said Martin Wright, Gravitricity’s co-founder and executive chairman. “Our GraviStore underground the best characteristics of lithium-ion batteries and pumped hydro storage – at low cost, and without the need for any rare earth metals.” By repurposing disused mine shafts for energy storage, mine original lifetime, and can mitigate decommissioning costs, while simultaneously creating new job opportunities and contributing to the green energy transition.
in Europe, India and Australia and this partnership with ABB – with us accelerate our ambitious commercialization plans. I am delighted we are working in tandem.” The teams will work together on feasibility studies to understand the application of existing hoisting technology in gravity energy identify suitable sites and shafts for the deployment of GraviStore.
30 | October 2024 |
www.hoistmagazine.com
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