Huisman have begun fabrication of a £1m energy storage demonstrator which is set for trials in Edinburgh next year.
The contract is being fulfilled for Gravitricity, developers of an energy storage system that works by raising multiple heavy weights – totalling up to 12,000 tonnes – in a deep shaft and releasing them when energy is required.
Gravitricity set to launch stored energy demonstrator
Work on the custom-built winches and control system has started at a Huisman factory in the Czech Republic and is expected to complete in December. The lattice tower for Gravitricity’s 250kW demonstrator is being fabricated by Kelvin Power in Leicester.
The full 16m high rig will then be assembled at a grid-connected site at the port of Leith for testing to begin in spring 2021.
Gravitricity have recently raised over £1.5m for their technology development through a crowdfunding campaign and have also received a £640,000 grant from Innovate UK.
In a statement, 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.”
Gravitricity plan to roll out their technology in disused mine shafts worldwide. Read more about this in the September 2020 edition of The Engineer.
KEY FACTS
- Rig height – 16 metres
- Weights – 2 x 25 tonnes
- Weigh composition – steel vessels filled with iron ore
- 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
Source: Gravitricity
Good news, as these developments are much needed for both storage and grid frequency control.
Given that this is storing about 1 kWh, its main contribution is likely to be frequency control, in competition with batteries.
It strikes me that this could be incorporated into an aero-generator as a windpower balance, lifting the weight when excess power is available, using it when the wind drops
The idea of converting deep coal mining shafts into renewable energy batteries has an appealing elegance.
The energy storage capacity is very low a 1.8 m diameter 10 m long cylinder with 80 m stroke stores 157 MJ or about 44 kWh. That is about 40 seconds worth of the output of a 3.6 MW turbine
What on the face of it seems a bit heath-robinson has some potential. It would be interesting to see what energy was needed during its ‘recovery’ or reset phase. Though many mine shafts have now been filled in or flooded. Which is another issue, how much energy to keep them water free? Maintenance of shafts is obviously needed, how do they intend to keep it safe while people are below working? And of course braking at the end of the drop? 25 or 50 tons on freefall has interesting repurcussions.
“And of course braking at the end of the drop? 25 or 50 tons on freefall has interesting repurcussions.”
Well (see what I did there), you could always use the the power from one falling weight to lift up the other !!
I am pleased to see that this article gives some numbers to the performance of the technology.
Obviously the slowing down of the fall of the weights allows a soft landing and control of the electricity generation.
I would suspect that its low energy storage would suffice for embedding in wind-turbines (in support columns?) to allow for smoother power output – and more graceful power down and help stop the sort of failure that precipitated the power cut of August 2019. This could be part of a proactive move to support consumers that National Grid/OFGEN should have mandated; perhaps they will?
I must admit I am unclear on, and find it difficult to discover, the power consumption required by wind-turbines (for starting, de-icing and just plain keep moving , lest shafts bow etc – especially the larger ones…) — so there may be other applications suited for this technology in wind-turbines.
Otherwise I see it as, possibly, being cheaper than batteries and as fast – for peak loping and emergency frequency control. But it would be good to see the proponents talking more about application – rather than a hand waving about energy storage..