A report by independent analysts at Imperial College London predicts that gravity-fed energy storage systems from Gravitricity may offer a better long-term cost of energy storage than batteries or other alternatives – particularly in grid balancing and rapid frequency response services.

Gravitricity uses a massive weight suspended in mine shafts to capture power and then release it in seconds.

In February Gravitricity received a £650,000 grant from Innovate UK, the UK Government’s innovation agency, to build their prototype.

Since then the Edinburgh start-up has signed a R&D agreement with Dutch lifting multi-national Huisman to develop a 250 kW concept demonstrator and test it in the Netherlands and Scotland early next year.

The report suggests that Gravitricity technology will be particularly well suited to provide grid balancing and rapid frequency response services to grid operators – where the requirement for multiple short cycles and high power availability play to Gravitricity’s strengths.

The detailed study factors in all relevant cost and performance factors including capex, operating costs, discount rate, depth of discharge and degradation over a 25-year lifespan to arrive at an annualised power Levelised Cost of Energy Storage (LCOS), quoted in US$/kWyear.

In a frequency response scenario – requiring 700 cycles per year and a duration of 15 minutes at a power output of 4MW – Gravitricity has a predicted LCOS of US$141/kW year, outperforming all alternatives.

Key findings:

  • Low specific power cost and high cyclability represent the key advantage of Gravitricity
  • Ideally suited to frequency response market and any application with multiple daily cycles
  • The higher initial opex is offset by very long lifespan (up to 50 years), high power availability, 100% depth of discharge and 0% degradation

“This independent report clearly shows that Gravitricity can be a very strong competitor in the frequency response market, where its low specific power cost and high cyclability sets it apart from other technologies,” states Gravitricity MD, Charlie Blair.

“Lithium batteries are just beginning to be a major provider of frequency response services around the world and we expect early Gravitricity projects to take an increasing proportion of this market.

“The report also validates our belief that in the medium term, energy storage projects will need to stack multiple revenues to be cost effective. Mechanical systems such as ours are very good at this, as we can cycle several times per day with no degradation.”

The report was authored by Oliver Schmidt, a specialist in predicting battery storage cost reductions.

He has published recently in Nature Energy and is currently on secondment to the International Energy Agency in Paris.