SOLAR panels are “highly ineffective” in the UK climate and although solar power produced more energy than coal between April and September, a free market think-tank claims we should not expect that to last.

In a paper published today called Solar Power in Britain, the Adam Smith Institute and the Scientific Alliance use 10 years’ worth of weather data to analyse the technology’s capabilities – and find it wanting.

It says solar panels are highly ineffective in UK climates and generate less than a tenth of their possible output annually – producing nothing for more than 30 weeks of the year, and only managing 50 per cent of their generation capability for eight days.

On claims that a combination of wind and solar power could smooth out this seasonal intermittency, the report says that even combined they would only exceed 60 per cent of their capability for a day-and-a-half each year, and would be below 20 per cent for more than half of the year – meaning they would have to be supplemented by more reliable sources.

The solar fleet produces less than 2.5 per cent of UK electricity generation says the report, the problem being that there is insufficient storage for energy generated in the summer to provide in winter. It adds the lifetime output of a 5MW solar park could be matched in 36 hours by a nuclear power plant taking up 50 times less ground space.

Two effective storage options that could make solar power feasible are addressed – pumped storage and battery storage, but it says these “highly expensive and environmentally damaging solutions are unworkable”. Instead, solar energy should focus on providing for local customers’ domestic water and heating until a more realistic storage system can be manufactured.

Ben Southwood, head of research at the Adam Smith Institute, said: “We know that UK solar panels only generate electricity at nine per cent of capacity, but our paper shows that even this average level is a mirage. Power comes in stops and spurts and not when we want it.

“If we had ways to store large amounts of energy cheaply then it wouldn’t matter when the sun shines, we could just save up what we’ve generated in batteries.

“In the future, cheaper and more efficient generation and storage will solve the problem, but for now there is no way of squaring the circle. Relying on solar and wind will force us to back up the supply with dirty fossil fuels, or the lights will go out.”

However, WWF Scotland director Lang Banks said: “Unlike coal, solar power absolutely has a role to play in the fight to address climate change in the UK and end our addiction with polluting fossil fuels.

“While wind and hydro power will continue to dominate our renewable power output, solar will continue to be rolled out as a result of its relatively low installation cost and its suitability to be used on the roofs of homes and other buildings. If you look at solar maps, Scotland receives about 80 per cent of the solar energy of Germany, the current world leader.

“The Scottish Government’s forthcoming energy strategy provides the perfect opportunity to set out a bold vision of becoming the EU’s first fully renewable electricity nation by 2030. Greater use of solar power should certainly be part of that vision.”