Designing Scotland’s electricity system so that it can run purely on renewable energy would require tens of billions of pounds worth of investment in battery storage or continued reliance on carbon emitting gas plants, according to modelling carried out by EDF.

Humphrey Cadoux-Hudson, managing director of nuclear development at EDF Energy, outlined the findings at an event on renewable energy organised by the union Prospect last week.

The French-owned utility had examined demand and supply in Scotland for electricity last October when enough power was generated from renewable sources to supply the country’s total power needs. Scotland was selected because of the self contained nature of the electricity grid north of the border.

However the modelling showed that mismatches in supply and demand, resulting from fluctuations in renewable generation, meant that other sources of energy would be required even when it is so abundant.

Cadoux-Hudson said that plugging the gaps when insufficient electricity is being generated by renewables would have required £56 billion worth of battery capacity.

Alternatively, if combined-cycle gas turbine (CCGT) plants were used as back up, the carbon intensity of Scotland’s electricity generation would be around 100g/kWh.

He said: “We are somewhere down the road but have a problem getting down to zero.

“If we are going to fulfil the aim of 100 per cent renewables, to ensure the stability of the grid and deliver electricity when needed, we will need a mix. A baseload of around a third of electricity from nuclear makes the problem of getting to zero carbon much, much easier.”

Tom Burke, chair of environmental consultancy E3G, told the event that achieving 100 per cent renewable electricity is “possible” but the more important question is whether it can be done in a “reliable, deliverable and affordable” way.

And he said the transition to a zero carbon energy system would not happen if the government maintained its “ideological approach” to energy policy which he described as “a lot more successful at deterring investment than complying with the Climate Change Act.”

“There is no prospect that markets can deliver the energy transition in time on their own and we cannot make the transition without the long-term public policy commitments that are alien to this government.”

Burke, who was a special adviser to Michael Heseltine when the latter was environment secretary in the 1990s, said the lack of action on cutting heating emissions is a “real failure of government particularly Treasury.”