OK, I am about to sound like a broken record. But, is it not time that people writing or campaigning about energy learned that the capacity of a power plant is not the same thing as the production of a power plant?
It’s rather simple really. Power plants have a rated capacity. It’s measured in megawatts or gigawatts and it tells you the plant’s maximum output. In the case of a wind farm this is the output when it is really windy. But on average it is not really windy, and often it isn’t windy at all. So, what happens? Well, instead of the plant producing, say, 1 GW all the time, it will produce something like 0.25 or 0.3 or 0.35 GW. It depends on how windy it is on average.
In the case of China, 1 GW will average 0.23 GW. That is, the average capacity factor is around 23%. However, nuclear power plants are much higher. In the US the average is around 90%, the more or less run full tilt all the time.
Yet, this basic knowledge seems to have not filtered down to enough people.
Take the completely garbled Quartz story Greenpeace tweeted. Here is the headline:
China’s wind farms can now produce more energy than all of America’s nuclear plants
OK. Now, let’s look at some basic facts. In 2013, America’s nuclear power plants produced 830 TWh of electricity. China’s wind farms produced around 130 TWh. Yes, this went up a bit in 2014. But, clearly China’s wind farms still produce much less energy than America’s nuclear power plants.
So, where does the headline come from? Well, as always the headline writer mixes up capacity and production. The author of the piece doesn’t, but still hands the reader a ball of confusion.
The confusion begins here:
But amid all the hype over nuclear power, China has been expanding its wind power capacity at an even faster clip. Last year, China’s wind farms reached a capacity of 115,000 megawatts, compared with just 20,000 megawatts from its nuclear sector. (To be sure, capacity is different than the actual amount of energy created.)
Yes, “To be sure, capacity is different than the actual amount of energy created”. An important caveat, and one that the author completely ignores throughout the rest of the article. And it starts in the next sentence:
Working at full pace, China’s wind farms could now produce more energy than all of the nuclear power plants in the US.
You can see why the sub-editor made the mistake when writing the headline.
Then we get this:
Beijing says it plans to increase China’s wind power capacity to 200,000 megawatts by 2020, but its own figures see nuclear rising to just 58,000 megawatts in the same time frame.
200 GW of wind, 58 GW of nuclear. Ah, clearly wind is far outpacing nuclear. But, what about that “to be sure caveat”?
This is not a difficult calculation to do. China’s wind farms have average capacity factors of 23%. Its nuclear power plants average around 85%. So, the average output is then remarkably easy to calculate.
For wind, it will be 200 * 0.23 = 46 GW.
For nuclear, it will be 58 * 0.85 = 49.3 GW.
So, instead of wind power racing ahead of nuclear by 2020, nuclear is marginally in front.
As you can see, none of this is particularly difficult to understand. So, why are we continually treated to news stories by journalists who don’t understand it?