Gravitricity, a Scottish start-up is planning a project for the storage of surplus power from solar and wind energy at the Port of Leith. The 250 kW, grid-connected prototype facility will be able to stabilize the network tested. A 16m-high rig uses the clean power to raise a mass in a 150-1500m shaft and will discharge the power thus ‘stored’ by releasing the mass to rotate an electric generator.
Gravitricity mentioned that the mass used can range from 500 to 5,000 tons and the electricity discharged could have the power to provide electricity to 30,000 nearby homes for two hours. Gravitricity stated that sophisticated winches and a control system can lower the mass very quickly, making it flexible enough to stabilize electricity networks at 50Hz and ensuring the set-up can respond to full power demand in under one second. The company based in Edinburgh said the system offers 25-year service without loss of performance or cyclical degradation and can be sited anywhere, including in city centres. The developer pointed to disused mine shafts as ideal locations.
Gravitricity will begin construction of a US$1.2 million pilot project in October on an industrial site at Port of Leith, Scotland’s largest enclosed deep-water port. With completion scheduled for December of 2020, the 250 kW prototype will be connected to Port of Leith’s power network and have its speed of response for grid stabilization assessed. “The demonstrator at the Port of Leith will allow the technology to under go trials on a much smaller scale, utilizing an above-ground structure,” the company said.
The pilot system will use two 25-tonne weights suspended by steel cables. “This two-month test program will confirm our modelling and give us valuable data for our first full-scale, 4 MW project, which will commence in 2021,” said Gravitricity lead engineer Miles Franklin. The project is being backed by government agency Innovate UK with a US$780,000 grant.
Energy Vault, a company based in the US unveiled gravity-based storage technology relying on a crane and 35-ton concrete blocks a year ago. That system was said to take account of volatility in energy supply and demand, weather conditions and inertia, according to the developers and was backed by a US$110 million investment from Japanese lender SoftBank in August. “Energy Vault will be demonstrating the first 35 MWh storage tower, in the north of Italy in 2019,” the Japanese conglomerate announced at the time.