Electricity has increased in importance in recent years and is probably the most vital manmade commodity. To support our way of life and critical services, a constant base supply is required, twenty four hours per day, 365 days per year with demand fluctuating through the day and year.
In addition to the steady load, there is a surge every working day, usually in the range 10000 – 15000 MW, from 530 am to 830 am, but up to 20000 MW in very cold weather. This is supplied by generators that can respond quickly to ensure that system frequency does not fall below statutory limits or cause load shedding.
As part of their strategy to reach zero carbon by 2050, the government, on the advice of the CCC, proposes that heating and transport will progressively convert to electricity from carbon based fuels. This policy could see the morning increase in demand double or treble in a few years time. Generating systems that have high availability and reliability will become more essential. The principal source of this electricity, according to the Net Zero Department will be renewables. As they are driven by natural forces, they do not have the capacity to increase output at will and blackouts are a real possibility, based on recent generation data.
Over the last 25 years, multiple schemes have been introduced to encourage and subsidise the switch to renewables and their long-term performance is a matter of record and does not instil confidence. There are now almost ten thousand wind turbines with an installed capacity of 30000 MW and similar solar capacity.
One does not have to be a meteorologist to recognise that wind speeds vary in an erratic fashion and that there are long periods in the winter when the sun provides negligible light. A cursory glance over the last few months in the data on websites such as Gridwatch, Mygrid, or Iamkate will reveal the times when renewables have been totally inadequate at times of high demand. At times of high demand, wind power sometimes suffered a dramatic collapse.
The evidence is clear from the winter period - November to March. On 22nd January 2025, wind machine output was in decline through the early hours and dropped to only 130 MW at 7 am. It was providing only 0.4% of UK electricity whilst the CCGT contribution was increased to 70%. On Monday 10th March, wind output was 13000 MW, but by Thursday 13th it was down to 1900 MW, forcing gas to increase to 23000 MW and imports from France reached 4000 MW. Generation security has been achieved by our gas-fired plants, with output peaking at 25000 MW. The security margin is small, with maximum installed capacity only a little greater at 28000 MW. Aggregated data confirms the situation.
Electricity generation over the 28 days to 18th March 2025 was:-
| Source | percent |
|---|---|
| Natural gas | 32% |
| nuclear | 13% |
| Offshore wind | 12.6% |
| Onshore wind | 12.6% |
| Imports | 14.4% |
A few old reactors and imports via cables under the North Sea supplied more electricity than all the 10000 wind machines. Such poor performance should be publicised, but it is never reported by the BBC. They reveal their partiality by reporting only days when renewables work well.
Solar power can be considered as making zero contribution to base-load, since during the winter months it provides no power for 16 hours per day. Its output is greatest when demand is very low in mid-summer. Renewables output is so variable that reliable backup must be on hand at all times to maintain supplies. Costs are increased substantially because duplicate equipment has to be available, maintained and staffed.
The government objective to reduce CO2 emissions has to recognise that only nuclear and hydro power can provide the combination of reliable output, security and negligible emissions.
Neither wind nor solar power can supply power continuously nor respond to the surges in demand that occur every working day and must be met quickly to stabilise system frequency. As long as we have secure back up from CCGTs, nuclear plants and imports, the illusion can be sustained that the renewables transition will be successful. However, the margin is being reduced as the oldest gas and nuclear plants approach retirement. The construction of new nuclear plants to replace those that are retiring must take precedence over the installation of renewable plants that have low load factors.
Paul Spare24 March 2024