Tower of power

03 Jan 2021

Engineering capacity news posted by Andy Sandford

Fabrication is nearing completion and assembly underway on a £1 million 250kW gravity-based energy storage demonstrator at the port of Leith.

Fife fabricator AJS Production was contracted to deliver the base frame and the weight baskets for the innovative Gravitricity prototype. The system’s lattice tower has been fabricated by ESL engineers in Hull, while custom-built winches and control modules have been made by international winch specialists Huisman at its factory in the Czech Republic and are currently being shipped to Leith.

The full 15-metre high rig will now be assembled at the grid-connected site for testing to begin in February 2021.

Commenting on the project, Steven Kirk, Senior Mechanical Engineer said: “AJS is fabricating two vital components for our demonstrator – the grillage (or base frame) will sit on the concrete plinth and will support the lattice tower, and the two weight baskets will be filled on site with high density aggregate, to create two 25-tonne weights.

“These weights will be suspended by steel cables within the tower, and 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.

“Our two-month test programme will begin in February and will confirm our modelling – and give us valuable data for our first full-scale 4MW project which will commence later in 2021,” Kirk concludes.

Photo: Senior Mechanical Engineer Steven Kirk and Mechanical Engineer Julie Le Négaret on-site at AJS Production.


Rig height – 15 metres

Weights – 2 x 25 tonnes

Weigh composition – steel vessels filled with high density aggregate

Cables – steel

Stroke – 7 metres

Time to drop (full power – 250kW) – 14 seconds - 0.6 m/s (1.3 mph)

Half power (125kW) – 28 seconds

See a short (30 second) explainer animation here.

See a longer (4 minute) explainer animation here.