The blackout experienced by more than a million people across the UK on Friday was notable by the fact that such occurrences are now exceedingly rare. Unlike in the 1970s, blackouts are infrequent and tend to be short-lived incidents. However, they could become more common in future as the country continues its shift to renewable generation.

The National Grid is, like its equivalent in most countries and regions in the world, a “synchronous grid” which means that it must be maintained at a steady frequency to function (50Hz in the UK). This allows multiple generators to be connected to the same network, increasing the security of supply, reducing costs and enabling energy trading.

The tricky part of managing such a network is that the power generation and power consumption across the network must be balanced consistently. If there is excessive generation on the network, then the frequency will rise, while is there is excessive load then the frequency will drop. The grid operator must then take steps (usually automatic in practice) to either reduce or increase the attached power generation. These adjustments can take time, however, and to stabilise the grid frequency in the short-term operators rely on “inertia” – the energy stored in massive spinning turbines of the sort found in large thermal power plants – coal, gas and nuclear.

On Friday, due to the high winds, there was relatively little thermal generation being used; indeed, it was shortly after National Grid had boasted of near-record wind-power generation. The downside of this is that there was little inertia in the system to call upon, which meant the grid was unusually vulnerable to disruption.

In a video posted online, Julian Leslie, the head of national control at the National Grid, explained the cut was caused by “the loss of two generators that connect to the National Grid transmission network in order to export their power. […] And what was happening as the frequency was falling, the system could see this, and unfortunately the way the system protects itself is by losing some demand.”

In other words, the grid will automatically blackout parts of the grid if there is no other way to maintain system frequency. And when two stations tripped (the gas station at Little Barford and the Hornsea offshore wind farm), there was little option but to disconnect some energy consumers, hence the blackout.

The wider point is, however, that through shameful inaction and misguided policy, successive governments have seriously compromised the security of our energy supply. For example, the UK currently has 15 nuclear reactors generating about 21% of its electricity but almost half of this capacity is to be retired by 2025. The failure to support the domestic nuclear industry has resulted in Britain being reliant on other nations to build new stations, provided terms can be agreed. Unfortunately, an inability to agree such contracts has resulted in both Toshiba and Hitachi cancelling projects in the UK, which leaves only the French and Chinese-backed Hinkley Point C in Somerset, and on terms that will force UK consumers to buy some of the most expensive electricity on the planet.

Green policies (such as the carbon tax) have also resulted in the government scheduling the closure of all Britain’s coal-fired power stations by 2025. In the near future, a huge amount of Britain’s existing base-load generation capacity will have disappeared, and there is little sign of any equivalent replacement coming online.

In fairness, it is likely that, as energy storage and “smart grid” technology improves and becomes more widespread, the network will become more resilient. Such major changes as more electric cars being connected to the grid could help, as could the ability to cut off certain connected devices for short periods (e.g. smart freezers). However, in the short-term, the rush by governments to being seen to go green has occurred at the expense of network resilience and security of supply. This means that we should perhaps expect more minor blackouts in the immediate future as we become more reliant on renewable energy sources.

A potentially bigger concern is what could happen in the event of a complete black-out on the National Grid. These (thankfully rare) events are usually the result of cascading failures resulting in a loss of network synchronisation which requires the whole network to be started from scratch. This is usually accomplished by getting thermal stations online, providing power across a small area of the network until it is stable enough to add more generation and more load. Gradually power is restored across the whole network, section by section. The trouble is that wind and other renewable sources are not capable of providing this “black-start” capacity due to their intermittency. Without large thermal stations available, it could take several days (possibly weeks) to fully restore power across the National Grid. This would be a period in which there would be no water, gas or petrol (due to electricity being required to pump them), rapidly diminishing food supplies (due to the inability to distribute food without petrol), no lighting or heating, and no broadcast media or mobile telecommunications to even let people know what was happening. In such circumstances, society could be stretched to breaking point. It may be highly unlikely but such events do happen, and we must be in a position to withstand such failures.

It must be a priority of the new government to deliver an energy strategy based on reality and not wishful thinking about the capacity of renewables to provide all our energy. If the government target to be carbon-neutral by 2050 is to be achieved, a new civil nuclear programme must be started, preferably domestically built, owned and operated. Thankfully, there are signs that the government might be taking steps in this direction by funding a small fleet of Rolls-Royce Small Modular Reactors (SMRs) to be built in the Sheffield city region, Cumbria, Lancashire and Cheshire. While much smaller than current plants (around 300MW compared to 2 x 1,600 MW at Hinckley Point C) they can be built faster, cheaper and with less financial risk.

In the short-term, it will fall to gas generation to fill the gap so we should get fracking urgently to prevent our energy supply being at the mercy of Russia and various Middle East despots (and which, via replacing coal and oil, will also reduce emissions). It is a tragic failure of imagination in Scotland that Aberdeen hasn’t been refocused as a global centre of excellence for fracking to replace the jobs and economic activity lost due to dwindling North Sea oil production.

Above all, the government needs to take responsibility for the security of our energy supplies and stop just hoping that something will turn up.