Battery that could revolutionise renewables on trial in Scotland

Source:, By Mure Dickie, 13 September 2016

Windturbines on the Isle of Gigha, Argyll

The Dancing Ladies of Gigha — a set of community-owned wind turbines — are about to be joined in their Scottish island idyll by a less dynamic but potentially more important electrical innovation: a battery.

But not just any old battery. The shipping container-sized object to be installed on Gigha is a “vanadium redox flow battery”, a new class of device that supporters say could revolutionise the global renewables sector.

Growing reliance on renewable but intermittent sources of power such as solar and wind have created a huge need to smooth out peaks and troughs in supply and so keep the lights on at night or on calm days.

Energy can already be stored using technologies ranging from pumped hydro schemes to large-scale lithium-ion batteries. But the UK government-funded trial on Gigha, site of Scotland’s first community-owned grid-connected wind farm, will demonstrate that vanadium redox flow is now commercially viable, says Scott McGregor, chief executive of the device’s developer, redT.

“The technology has moved faster than anyone has expected and what you see today is a system that is a commodity product,” Mr McGregor says. “This is ready to scale.”

It is not just redT that believes the time has come for vanadium flow batteries. Late last year, Japan’s Sumitomo Electric Industries started operation of a 60MWh battery system the size of a large building on the northern island of Hokkaido. Sumitomo plans to release shipping container-sized flow batteries soon. German manufacturer Gildemeister already sells them as part of its Cellcube energy storage system.

Redox flow devices — which Mr McGregor prefers to call “machines” rather than “batteries” — are based on vanadium’s ability to hold different levels of electrical charge. Pumps and membranes are used to separate or bring together differently charged vanadium solutions, charging or discharging electricity.

The redT energy storage machine on Gigha

Although technically challenging and relatively bulky, the approach promises some big advantages. Unlike lithium-ion batteries, redox flow devices are not flammable and do not gradually lose their capacity, which should mean long working lives and therefore much lower costs.

Mr McGregor says parts of redT’s devices may need replacing after 12 years or so but “the rest of it will just keep on going” for at least two decades.

RedT, which is listed on the London Stock Exchange’s Aim, claims it can sell its devices at half the price or less of its redox flow rivals. That should enhance the technology’s appeal for “grid constrained” generators that currently struggle to sell their electricity at times of peak production but cannot afford other forms of storage.

On Gigha (pronounced “gee-ah” with a hard “g”), the wind farm has had to limit output because of a shortage of grid capacity and has had no way of storing the excess until now. Installing the planned seven redT units, each with capacity of 240 kWh, will allow the community to store electricity for sale when the grid can accept it and also potentially stabilise supply to the island itself.

The trial is drawing close attention from policymakers and renewables developers. Paul Wheelhouse, the Scottish government’s energy minister, visited the town of Cumbernauld near Glasgow this month to inspect a Gigha-bound redT device as it was put through its paces at Scotland’s Power Networks Demonstration Centre.

Mr Wheelhouse said he was impressed by the technology hidden inside the unprepossessing grey container at the centre — adding that Scotland had scores of islands that might benefit from it. “Clearly, we will learn a lot from what happens in Gigha,” the minister said. “It is exciting to see it deployed in a real-life situation.”

Timothy Cornelius, chief of tidal power developer Atlantis Resources, says the Gigha trial is “of extreme interest”. Atlantis is building one of the world’s largest tidal power arrays in Scotland’s Pentland Firth and expects energy storage to play a big role in future projects, particularly when they involve islands with limited grid connections.

“We fully subscribe to the idea that storage is the revolution,” Mr Cornelius says. “If they can prove [vanadium redox flow works as billed] then Scott McGregor will be one of the first people I call.”

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