The whiter the image, the hotter the area.
Recently I found myself on the roof of a shed I hadn’t worked on in at least a dozen years. The sun wasn’t gone yet, but damn, it needed cleaning.
These days I have a thermal imaging camera to play with and have a passing interest in how real solar systems cope with age. I’m happy to report that this unit worked well, but the owner complained about rising electric bills. Due to an annual rainfall of 800 mm and an almost invisible installation, other things grew on the site unnoticed.
It’s been quite a journey
I reminisced in more ways than one. This was a roof that I had fallen through while helping to put up the building. How? I concentrated my weight on stepping on a sheet of roofing that had no screws in it. In response, I stood upright and was able to easily pass through the frame.
“Remember that!?” my old buddy giggled… Well; I’ll never forget landing on a screwdriver. It hurt, but I particularly remember laughing and worrying about denting the roof sheet metal. It was hilarious.
Maintenance time
This time I was tricked into helping replace some cracked plastic skylight panels, but we managed the job without any safety issues.
While I was there, I took a quick look at the 3.33 kW system. Originally consisting of 10 Sungrid branded panels, it was quickly expanded to include 8 genuine Australian units from Silex.
Australia has been a world leader in solar
BP Solar previously operated a complete solar module manufacturing facility in Sydney, unlike Tindo Solar’s current solar module factory in Adelaide, this was a complete end-to-end ingot, wafer and module operation.
BP Solar Australia. We didn’t just give up car manufacturing. This specimen is kept in a museum in Port Augusta SA
Those were the glory days when the new Olympic Village in Sydney featured Australian-made panels on the roof and our esteemed leaders spent ten times more research and development dollars on “clean coal”1 than on renewable energy.
While BP previously supplied panels for the legendary Telecom Outback phone boxes, China had decided that they should own the world’s renewable energy industry. Our little plant soon grew into a tiny, unrivaled size. After BP sold out, Silex took over for a while, but unfortunately it didn’t last long.
Telecommunications telephone boxes at Innaminka. Photo credit to Solar Depot for sending me there to see them
At least today we have above-average success in installing solar systems on roofs.
White = hot: Viewed from above or below, the panel in our cover photo has a hot cell because lichens are growing over it
Damn, there is a real need for cleaning
As the cover image shows, a seemingly harmless little green spot actually affects the operating temperature of a solar cell.
By blocking the light on that one cell, all the others in that row must force their electrons through an unproductive wafer.
In this example, a third of the panel is affected, and the diodes in the junction box where the three cell strings are connected will also work to allow the rest of the panel to work around the problem.
This excess heat is obviously wasted energy, but it also shortens the life of the cell and affects overall performance in the long term.
Fortunately, in this case, it didn’t take long for the cell to cool down after the offending growth was removed.
All it took was scraping off most of the lichen with my pocket knife to make the difference.
Take a different perspective
Although these images were taken with just a simple $600 phone attachment2, the motivating effect they have on customers and installers is priceless.
The lichens on this row look fairly harmless to the naked eye
Thermal imaging cameras continually optimize themselves to display contrast. In any given setting, there can be a difference in surface temperature of 10 degrees or 100 degrees.
The colors shown do not represent a specific number, but rather the coldest surface is shown as a dark spot while the warmest is white and hot, so to speak.
Better cameras provide numbers on a scale to show actual temperature, but the latest software update seems to have removed this setting from my device.
Here we see the same arrangement with a few dog balls on display; from hundreds of cells; They really shine here.
There are literally no limits for the best results. Commercial operators spend $15,000 or more on a high-resolution camera and drone package.
Still, the costs are easy to justify when there are thousands upon thousands of panels to inspect in a solar farm. And of course, drones are very convenient for a home system in a difficult two-story house.
Beware of solar panel cleaner claims
If the dirt is so thick that you can’t see the cells, cleaning is essential. However, some solar panel cleaners tend to exaggerate how much yield you can restore to a system by simply removing a transparent layer of dirt.
If they have a photo of an inverter display that shows 30% more power, it’s probably just because they cooled the panels with water.
Provided the array has a tilt of 10 degrees or more, it will probably clean itself in the rain.
Under no circumstances should you walk over the glass or use a high-pressure cleaning machine when cleaning.
It is interesting to see how low coverage causes a cell to heat up
5 years is fine
My general advice is to hire a qualified solar company to clean and inspect your solar system as often as you like.
However, remember that as a small embedded generator, you are required to have the system inspected to ensure safety. The agreement you have with the Poles and Lines Authority normally calls for 5 year intervals, but I have never heard of audits being carried out.
Harsh shade should be avoided
While it may not seem significant, the key message here is simply that shade is not good for solar cells. Whether it’s bird droppings, leaves and lichen or, even worse, smelly pipes, antennas or other obstructions, the best performance and longest life comes from eliminating stubborn shade.
Footnotes
- How good is clean coal? Reminds me of a famous passage by Donald Horne that no one ever quotes in full. Australia is a lucky country, ruled mostly by second-rate people who share its good fortune. It thrives on other people’s ideas, and although its common people are adaptable, most of its leaders (in all fields) so lack curiosity about the events that surround them that they are often caught off guard. ↩
- I’m sure there are now imitation thermal imaging cameras for half the price ↩
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