Goldilocks Power: Why Solar Output Plummets During Heatwaves
Goldilocks was evidently the brains behind the ‘engineering’ of wind and solar power, which only operate when conditions are “just right”.
When the weather turns nasty, giant industrial wind turbines simply turn off. When there’s no wind, they produce nothing; when winds hit gale force, they produce nothing.
Solar panels aren’t any more resilient.
A few fluffy clouds give them grief.
Hailstones make short work of them; a blanket of snow and ice cuts their production to nothing, even when the sun is shining.
A hurricane or tornado soon tears them to worthless shreds.
But, counterintuitively, it’s when solar energy is at its zenith that the output they occasionally produce starts to drop off, very dramatically.
In Australia, summertime temperatures are routinely 35° C and above with heatwaves of 40° C and above, that can last for a week at a stretch. In those conditions, as their owners will sheepishly admit, their output drops off, well below their rated capacity.
In Britain such conditions are rare, so this is probably the first time the owners of solar panels have worked out just how fickle they can be.
Helen Cahill has the story.
Weather ‘too hot’ for solar panels
19 July 2022
The weather was too hot for solar panels on Tuesday as soaring temperatures reduced their efficiency.
As the heatwave pushed the mercury above 40C for the first time ever in Britain, solar output remained well below the levels usually reached at peak times in spring.
Modelling data from the University of Sheffield suggests that solar energy provided an average 2.8 gigawatts of power on Tuesday.
Meanwhile in spring, when the weather is cooler and generation peaks, it typically accounts for 3.3 gigawatts, according to Josh Jackman, researcher at The Eco Experts.
Solar panels become less efficient when temperatures rise above 25C, meaning energy generation drops off, with efficiency decreasing by around 0.35 percentage points for every degree above this level.
Professor Alastair Buckley, of the University of Sheffield, said: “We never see peak output in mid summer.
“The temperature of the actual solar cell depends on a combination of the ambient temperature and the radiative heating from the sun and also cooling from wind. We saw cell temperatures of 70 degrees yesterday on our test system. Normally it would be between 40 degrees and 50 degrees.”
Tim Dixon, analyst at Cornwall Insight, said: “The efficiency of solar panels is impacted by temperature, with high temperatures above 25 degrees negatively impacting on performance. It is likely that the extreme temperatures have impacted total output levels.”
Chris Hewett, chief executive of industry group Solar Energy UK, said the current weather was “good for solar energy generation” but that the heat “brings down the efficiency of the panels slightly”.
Mr Jackman said that solar panels would be performing better in a heatwave than during a spell of cloudy weather despite their limitations at higher temperatures, and that the technology would normally achieve an average efficiency of around 85pc in a year.
“If it was a cloudy day, they would also be suffering. Losing 5pc of efficiency sounds bad but on a cloudy day you can lose anywhere from 25pc to 66pc depending on how cloudy it is.
“So actually it’s better for it to be too hot than for it to be cloudy.
“They are only at maximum efficiency quite rarely. But who among us is ever at maximum efficiency?”