Gravitricity has celebrated a new milestone, as the 15-metre high lattice tower for its storage demonstrator project is installed ahead of testing beginning next month.
The Leith based energy storage start-up is building a £1 million 250kW demonstration project at Forth Port’s Prince Albert Dock, Edinburgh, Scotland, made up of the tower, two 25-tonnes weights suspended by steel cables, plus two fully grid-connected generator units.
Now the tower, which has been fabricated by ESL engineers in Hull, has been installed along with the top frame, and work has begun on installing the electrical connection to the winch container, which is expected to be fully commissioned by April.
This will allow Gravitricity to move on to the test phase, where the company will begin by lowering weight to generate full power, allowing it to verify the speed of response possible.
"We calculate we can go from zero to full power in less than a second – which can be extremely valuable in the frequency response and back-up power markets,” explained Frances Tierney, engineering project manager.
"We’ll then run tests with the two single weights, dropping one after the other to verify smooth energy output over a longer period, alongside a programme of other tests to demonstrate and refine the full capabilities of the system.”
Gravitricity is expecting the time to drop – thus the time to full power, 250kW for the demonstrator – will be 14 seconds, with the weights travelling 0.6 m/s (1.3 mph). While the time to half power (125kW) is expected to be 28 seconds.
The demonstrator was announced in May 2020, after the company was awarded a £640,000 grant from Innovate UK. Gravitricity is working with AJS Fabrication in Fife on the base frame and weight baskets, Glasgow based Industrial Systems and Control on controls and simulations, and its long-term partner Huisman on the system’s custom-built winches and control modules.
The upcoming two month test programme " will confirm our modelling and give us valuable data for our first full-scale 4-8 MW project which will commence later this year,” added Tierney.
Gravitricity’s technology works by raising weights totalling up to 12,000 tonnes in a deep shaft when there is excess renewable energy on the grid, and then releasing them when energy is required. In particular, the company is targeting decommissioned mine shafts as sites for development.
The company said analysts have calculated that the system can store energy at half the lifetime cost of lithium-ion batteries.