Work has started at the firm’s specialist factory in the Czech Republic and is expected to complete in December. The custom-built winches and control system will be shipped from Rotterdam to Leith. At the same time the 250kW demonstrator’s lattice tower is being fabricated by Leicester engineering specialists Kelvin Power.

The full 16-metre high rig will then be assembled at a grid-connected site at the port of Leith for testing to begin in spring 2021.

The Scottish energy innovators have recently raised over £1.5 million for their technology development through a crowdfunding campaign and have also received a £640,000 grant from Innovate UK, the UK Government’s innovation agency.

Gravitricity lead engineer Miles Franklin said: “Our demonstrator will use two 25-tonnes weights suspended by steel cables. In one test we’ll drop the weights together to generate full power and verify our speed of response. 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

“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. This two-month test programme will confirm our modelling and give us valuable data for our first full-scale 4MW project which will commence in 2021.

“Huisman are global experts in winches and control systems and it is great to have them as strategic partner for this project and our full-scale system.”

Pepijn Toornstra, Huisman managing director, said: “We are extremely pleased to have received from Gravitricity this project to build a unique energy storage system. It is an excellent addition to our current production portfolio and we hope that it will be a long-term success for both our companies and our contribution to the renewable energy market, the growing importance of which we are convinced.”

Gravitricity’s energy storage system works by raising multiple heavy weights – totalling up to 12,000 tonnes – in a deep shaft and releasing them when energy is required. They plan to roll out their technology in disused mine shafts worldwide.