Imagine a perfect summer weekend day: a cloudless blue sky with a gentle breeze. Solar panels are at full capacity, wind turbines are turning offshore – and many people are out and about, in gardens or parks. Electricity supply is high, but demand is low.

Electricity systems must balance supply and demand in real time. In the above scenario, when renewables are producing lots of electricity but there isn’t much demand, energy companies may need to curtail output – disconnecting their turbines or panels from the grid, and essentially wasting clean energy that could have been generated. Hours later, when demand rises, that energy is no longer available.

In the UK, wind farms are already being paid to switch off on days when supply outstrips demand. Similar curtailment of renewable generation already happens regularly in places with lots of solar power such as California, Spain or Australia. As renewable energy........

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