Supporters of nuclear power often argue against renewables on the grounds that the sun does not always shine on a solar array and the wind does not always blow to turn the blades of a wind turbine. They contrast nuclear power with wind and solar by saying that nuclear power provides reliable constant base power while the renewables cannot be relied upon.
The truth is a bit more complex than “nuclear is reliable and wind and solar are not reliable.” This is partly based on the fact that large scale batteries, pump energy storage in reservoirs and other ways to regularly supplementing intermittent wind and solar power have been developed. This means that the baseload power provided by nuclear power is no longer so important. In addition, the output of the global fleet of commercial nuclear fission power reactors is falling while the output of wind and solar installations are increasing.
Output from electrical generating systems over a year is measured in terawatt hours (TWh). In 2020, the electricity generated from nuclear power in the U.K. was about fifty terawatt hours which is down eleven percent from nuclear electricity generation in 2019. Part of the reason for this is the need to deal with cracks and rust in aging reactors. The renewable output for electricity generation achieved a record high of one hundred and twenty terawatt hours in 2020.
Nuclear electricity generation was thirteen terawatts less in 2020 when compared to output for 1989 when nuclear provided about twenty percent of the U.K.’s electricity. The amount of wind and solar generation was tiny. Even though the massive Hinkley Point C nuclear power plant is currently being constructed, nuclear power is fading away in the U.K. In order to keep the lights on in the U.K., they are going to have to learn how to carefully manage the power produced by unreliable sun and wind.
While nuclear power is fairly reliable, it is not “on” one hundred percent of the time. For example, a power reactor in the U.S. with an maximum annual capacity of 5,098,320 MWh at full production actually only produced produced 4,697,675 MWh which is eight percent less than full production. Nuclear fission reactors need to be refueled every twelve to eighteen months. This means that they are not generating one hundred percent of the time. In addition, any necessary down time for maintenance and repair of the aging reactors will also take them out of producing electricity for weeks to months. This further reduced annual electricity production. As reactor age, they require more maintenance and repair which means that they are offline even more of time.
While baseload power is important in areas where the demand requires it, it turns out that baseload power is not always needed if the demand drops. Nuclear power reactors are difficult to turn on and off and most do not have the capability of load-following which means that their production of electricity cannot be easily raised or lowered to follow demand. On the other hand, it is easy to load-follow with renewables.
The bottom line is that while massive nuclear power reactors have supplied a lot of power for the U.K. in the past, their utility is falling for future electricity generation. And, for those who suggest that a combination of nuclear and renewables would be desirable, it turns out that if nuclear power is pursued, it can reduce the ability of a nation to also develop a robust renewables program.