The advantage of lithium-ion batteries is that they can be...

The advantage of lithium-ion batteries is that they can be placed anywhere and can provide power to the grid very quickly, as they do in electric cars. They can respond in milliseconds and generally provide up to four hours of storage, helping grids deal with sudden outages in electricity generation, but are less cost effective in the longer term. In the UK, the majority of large-scale lithium-ion batteries provide energy for 30-90 minutes.

And local residents such as King worry about their safety, after a spate of battery fires over the past few years. There were 33 fires at installations in South Korea between 2017 and 2018 alone, and there have been more recent incidents in the UK and US.

In January, the California Energy Commission, the US state’s primary energy policy and planning agency, issued a call for long-duration energy storage – defined as providing energy for over 10 hours – enough to store a day’s worth of solar energy for overnight use.

Matt Harper, the company’s chief commercial officer, says vanadium batteries can store eight to 10 hours of renewable energy during the day and deploy it during peak demand, or overnight, helping to put a floor under power prices. They are also “more likely to put out a fire than start one,” he says, because they use a water-based electrolyte. They also last longer than lithium-ion cells – and can go for 30 years.

In the centre of Dalian, north-east China, Rongke Power is building the world’s biggest vanadium battery. At 800 megawatt-hours, it would be more than three times the size of the world’s largest lithium-ion battery installation in California. It would help Liaoning province’s electricity grid better integrate wind power.

“We would not be allowed to install a large-scale lithium-ion battery in the city centre, [due to safety concerns],” says Li Bin, Rongke’s marketing director. “The safety issues in lithium-ion batteries have not been solved.”

Yet vanadium prices are highly volatile and surged to $US127 per kilogram in November 2018 before falling to $US25 per kg today, which could have an impact on the cost of production.