Days would be needed to restore electricity supply in Scotland after blackouts, the risk of which are increasing due to the grid’s growing reliance on intermittent renewable generation, according to a new report.

A new paper from the Institute of Engineering and Shipbuilding in Scotland (IESS), entitled Engineering for Energy, says the closure of thermal generating plants has resulted in a “significant loss” of the inertia that is an important feature in guarding against instability in the energy system.

It says that coal and gas-fired power stations are important in restoring electricity supply following system failures, wind generators can only have a very limited role in such situations and nuclear plants cannot be quickly restarted.

It says: “The time to restore supply in Scotland is now estimated in days – several days – rather than in hours. A lengthy delay would have severe negative consequences – the supply of food, water, heat, money, petrol would be compromised; there would be limited communications. The situation would be nightmarish.

“The likelihood of system failure and the time to restore electricity supply is therefore increasing at a time when society and business have become fully dependent on it. The risks will continue to increase unless action is taken to control them.”

The paper calls for the establishment of a National Energy Authority to ensure the provision of fit for purpose energy infrastructure by planning supply capacity and plant mix.

It says the growing prevalence of wind and solar generation means there is an increasing need for such a system approach for energy planning.

Fluctuations in demand for electricity, which can increase by 30GW to 40GW over a three-hour period on winter mornings, means the system must contain flexible and reliable generation that can be called on when needed at the required power levels. The report states that neither wind and solar generation are sufficiently reliable or flexible to play this role.

It says a range of control strategies, including demand management and extra storage as well as additional generation, can be used to maintain the flexibility and reliability of the energy system.

These extra “integration costs” should be taken into account by using the Total System Cost Method (TSC) which takes account of all the costs paid for by customers for generating, transmitting and distributing electricity.

Justin Bowden, GMB National Secretary, said the IESS report underlined the case for continued investment in gas supply.

“This report is the latest document to back up what we’ve been saying for years – Britain needs gas – and both the Scottish and UK governments must heed these expert warnings and place gas at the heart of future energy policy.

“Gas heats 85 per cent of UK homes [21 million] and provides nearly half of our electricity. As we transition to a lower carbon economy, we need to make sure our energy supply is safe, secure and in our own hands and, should the worst happen, gas will be vital to quickly deal with a power outage.”

Claire Mack, chief executive of Scottish Renewables, said: “The average UK fossil fuel power station is more than 30 years old and we must replace these ageing plants with clean, cheap and secure generation if Scotland and the UK are to meet existing carbon targets.

“Renewable energy ticks all those boxes – and it’s popular, with the latest UK government poll showing more than 82 per cent of the UK public back the use of renewable energy to provide our electricity, fuel and heat.

“Renewables now generate enough electricity to meet almost 70 per cent of Scotland’s power demand and National Grid, which is responsible for the security of our energy system, is already planning for more green power generation, saying it is confident ‘we will have the intelligence available in the system to ensure power is consumed when it’s there and not when it’s not there’.

“Investing in renewable generation means stabilising energy costs, banking on technology which is becoming cheaper every day, creating jobs and reducing carbon emissions.

“Failing to do so will expose energy consumers to volatile fossil fuel prices and poorer air quality, as well as the global threat of climate change.”