Why a cold snap could spell disaster
In 2012, a spell of super-cold weather hit much of Europe, starting in the east, and gradually moving west, until even the UK saw temperatures down to minus 11°C. If that happened again today, I believe there would be rotational disconnections and blackouts across the UK, and possibly much of Western Europe too.
NESO appear dangerously complacent. At the root of the problem is its approach of using an ‘average cold spell’ to determine the maximum demand on the system, and the so-called ‘derated capacity’ to determine whether the amount of generation capacity available is adequate to meet it.
Our growing demand from heat pumps and EVs means that a very cold spell means a spike in demand beyond that seen in an ‘average’ cold spell.
But the big problem is on the demand side. De-rating of generators tends consider 'average' weather conditions, perhaps with some notion of the likelihood of maintenance outages too. Windfarms will of course be derated to a much lower percentage of capacity than gas-fired power stations, reflecting the fact that the wind might not blow.
However, in a 2012-style cold snap, we would expect to get nothing from our renewables fleet at all – such periods are characterised by still weather and winter gloom. That would mean that the thermal plant (gas and nuclear) would have to take the whole strain of delivering 60 GW or more to the UK, as well as considerable demand for exports across the interconnectors to France. But would there be enough? Put another way, are the derating factors for thermal plant adequate?
Under average conditions, they may be. But under the conditions of extreme cold in 2012, there were, for example, problems with gas supply valves freezing, supply pumps and regulators freezing shut or only partially open, and cooling systems freezing up. This meant many that generators that had declared themselves available, didn’t start. Others started, but because of failures in either gas supply or cooling system, their output didn't climb and they quickly disconnected again entirely. Other plant ran fine for six or eight hours then failed – old plant doesn't like running at maximum stress for hours on end.
Consider what this might mean today. On the first day of the cold snap, we might expect to have:
Wind: 1% of capacity
Thermal: 70% of capacity.
This on its own would be bad enough, but with the interconnectors wanting to export too, it would be a serious problem.
By day 2, the availability of thermal generation would have fallen to 40% or so, as we encountered the problem of aged gas plant refusing to run at maximum output for hours on end. Hard choices would then follow. We would probably cut the interconnectors, and after that we’d also have to decide if we wanted to prioritise supplies of natural to domestic heating or electricity generation.
By day 3, we’d almost certainly have to curtail demand – in other words, to impose rolling blackouts. This might need to take in half the country at a time. And since central heating and heat pumps cannot be used without an electrical supply, it would undoubtedly result in many deaths from cold.
NESO’s current approach is inadequate. They need to urgently switch to proper scenario-based modelling for capacity, reliability and energy duration, as well as considering interdependencies on gas networks and electricity networks across Europe. They also need to look at how extreme weather and geopolitical events might restrict or inflate electricity and gas exports and imports. They are not considering low-probability but high-impact events, and that failure could spell disaster.