by Dan Auld, Friend of Katerva
Google is just about the smartest place on earth. So in 2008, many were surprised that Google was surprised with its discovery that it did not really know that much about its 1.65 megawatt solar array.
They knew it was dirty. And when they cleaned it, energy production doubled. And they knew all kinds of other things could prevent their array from operating at Google-like efficiency: dirt from neighboring fields, baseballs, birds, squirrels, wiring, leaves, and hundreds of other bugaboos.
But that was the extent of their knowledge. They did not know which panels were good or bad; which needed replacing or just washing. And they definitely did not know when these maintenance measures should be performed.
And the company admitted as much in its study on getting more energy from their panels:
It would be difficult to detect manufacturer defects or accidental damage by data analysis alone, unless the damage impacts (greater than about) 20% of the solar panels in that building. Example: There have been few occasions when some of the solar panels … were damaged by delivery trucks accidentally hitting the support beams that hold up the solar panels. Since these accidents did not damage a sizable portion of the solar panels, the damage went undetected for a while.
Translation: if you want to know the best time to clean your system or replace your panels, do what Google suggests — guess.
There is a better way, however.
First, let’s do a little Engineering for Dummies:
Google’s solar system covered about two football fields with somewhere between 5,000 and 10,000 panels, all wired together.
“But that creates an illusion there is just one system, when each panel is really its own little power plant,” said Ray Burgess, CEO of Solar Power Technologies. “And like the old Christmas tree lights, if one panel goes down, that hurts surrounding panels. Which we would never know without proper monitors.”
A piece of shadow, for example, not only hurts the array beneath the shade, but an area 36 times larger,says government energy laboratories.
“So all these things happen, and you don’t really know why because instead of keeping track of each of the 10,000 mini-power plants, you are only tracking their total production, when you need to be using monitors to track individual panels,” Burgess said.
Government energy agencies say solar panels go bad at the rate of .5% to 4.5% a year. For someone with 10,000 panes, that’s 50 to 450 panels going bad a year. Every year. That does not count the raccoons and baseballs and birds.
But without panel monitoring, there is no one way of knowing which are bad — unless you tested every one every year, which would probably cost hundreds of times more than the panels are worth. You don’t pay $1 million to test a $10,000 car.
Do some rough math: The United Nations says over the last two years, the world has spent $142 billion on solar power facilities.“And 20, 30, 40 percent of that is just wasting away because we don’t use the right kind of monitors?,” said Burgess. “Seriously?”