Ask a Solar Expert: How does weather affect solar?

Ask a Solar Expert: Weather from Bella Energy on Vimeo.

So first of all, when it comes to weather, when we give you an estimate on annual production, it is taking into account average historical weather patterns over the last 15 years. We use the National Renewable Laboratory’s database on PV production for specific areas of the county, specifically Boulder. So when they say a 1 kW system facing South at 40 degrees pitch with produce 1459 kWh in a year, that is taking into account that there is of course multiple days with clouds, there are days when there is pollen on the panels, there are days when there is snow on the panels. So essentially, yes, PV is affected by weather, specifically clouds. But is managed in our estimates. Essentially, we manage that expectation in the estimate we provide to the customer.

More specifically, on a cloudy day, the voltage of the panels stays at what is supposed to be. So for example, you might have a Sharp 175 panel that’s running at, and I’m just throwing this out there, at 28 volts or something like that, and let’s say 8 amps. On a cloudy day the panel is still going to run at 28 volts. What is going to drop is the amperage. So if you had, 4PM, in other words twilight sun, and completely overcast the voltage on those panels is going to be fine. The amperage is going to be an eighth or a tenth of what it could be optimally. Which translates to that your panels will be operating at about an eighth to a tenth of what they would be optimally.

With regards to hail, all panels that we install are UL Listed and UL Tested. As part of the UL test, there is a test against hail. That said, the glazing or the glass on top of the panel can crack and still pass the test. The test is looking to ensure that the glazing or glass doesn’t explode out of the frame and potentially hurt somebody, i.e. flying glass. They use a 1 inch steel ball and drop it at terminal velocity to strike the panel at a 90 degree hit. Not all panels glazing breaks, but on average the panel’s glazing cannot explode out of the frame.

Now if we had a hail storm and your glazing or glass or coating broke you would need to get that replaced and it would not be covered by warrantee. However, homeowner’s insurance policies will cover that, and the same with lightning. That being said you do need to check with your homeowner’s insurance company to make sure that you new solar electric or PV system is going to be covered. But in the majority of cases, it is considered what is termed in the insurance industry a permanent fixture on the home and it will be covered, without a rider in most cases.

Then with regards to lightning, and protecting the system from lightning. NEC, which is the National Electric Code, does require that we put into place grounding systems. These grounding systems are essentially equipment grounds, grounding electro-conductors and grounding rods. All of these things help protect the overall system in the case of a lightning strike, but in all likelihood it is not going to completely protect it. The consensus in the industry among experts is that lightning does what it wants, goes where it wants to go and there is certainly the possibility that your system could be damaged by lightning. Again should be covered by insurance, but a worthy question to ask of your insurance agent.

Tags: solar expert, weather