Does heat help or hinder solar panels?


Posted

March 02, 2019 10:27:08

The future of solar energy in Australia has never looked brighter.

Key points:

  • Demand for electricity is expected to increase in parts of Australia this weekend
  • Experts say solar panels become less efficient in extreme heat
  • The perfect temperature for a solar panel is about 25C

Solar firms and farms are springing up across the country, and more than 20 per cent of the nation’s homes have solar installations.

There is also largescale investment by state governments in home battery schemes which capture energy generated by rooftop panels, with the aim of driving down household power bills.

But despite their growing popularity, there are still some lingering misconceptions about how solar cells work, especially in very hot weather.

“A solar panel is a bit like the silicon chip inside your computer, if it gets too hot it doesn’t work quite so well,” University of WA resources scientist Ray Wills said.

Parts of southern Australia, including Adelaide, are currently enduring an unusually hot start to autumn.

Temperatures rising above 40 degrees Celsius are expected across South Australia today, with temperatures in the high 30s forecast in parts of Victoria.

Will the heat help or hinder solar panels?

In sweltering conditions, many will switch on their air conditioners, driving up demand for electricity.

While it is easy to assume that blazing sunshine would boost the performance of solar panels, generating more power, that is not necessarily the case.

“A really hot day, you’ll actually produce less power because the solar panel gets so hot,” engineer and solar analyst Finn Peacock said.

“The heat from the sun actually degrades the efficiency of the panel.

“So the perfect conditions for solar are strong sun but cold, which is pretty unusual unless you’re in the Arctic.”

What works best?

In order to work at maximum efficiency, the perfect temperature for a solar panel is about 25C.

But that refers to the temperature of the panel itself, not the atmospheric temperature.

“On a 45C day, I would expect the panel to be at least 75C, so the panel is 50C hotter than the optimum,” Mr Peacock said.

For every degree above that optimum, power output will decline by about half a per cent.

“If it’s 10C higher than normal, it’s underperforming by 5 per cent which is not a lot,” University of NSW solar researcher Renate Egan said.

It’s all about light, not heat

There are different types of solar energy production: solar photovoltaic (PV) and solar thermal.

As its name suggests, solar thermal harnesses the heat of the sun and operates in a similar way to a coal-fired power station — it boils water and generates steam.

But most rooftop solar panels and solar farm projects in Australia are photovoltaic — they convert light into electricity.

“The way solar PV works is that you have this material, typically silicon, and there’s a certain kind of magic that goes on in silicon,” Associate Professor Egan said.

“It’s known as a semi-conductor, which means it conducts electricity some of the time.

“When you shine a light on [it], it generates free electrons and those electrons can then travel, so it becomes a conductor when it’s exposed to light. That’s how a solar panel works.”

The reason extreme heat hinders that process is because of the basic physical properties of the semi-conductor.

Is this bad for power bills?

Not necessarily.

While electricity output from household solar panels will likely drop today, that doesn’t mean homes will stop producing their own power, or even be producing less power than they need.

“It’s not a show stopper. It’s still very useful to have solar during a heatwave. If you’ve got a good system, it should power your house through,” Mr Peacock said.

“You may produce 30 kilowatt hours in the day instead of 40 kilowatt hours in the day, but if you’ve got a reasonably efficient home that would be way more than enough to power your home through the heatwave.”

Topics:

weather,

solar-energy,

alternative-energy,

environment,

sa,

adelaide-5000



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