Quote:
Originally Posted by jyl
What is a realistic lifetime for a residential PV grid-tie system (w/o batteries)? 20 years? 30? What wears out?
Is there any maintenance required, or is cost literally zero after year 1? I would think you want to hose off dust and leaves now and again? My roof is three stories up and I'm not sure how I'd do that - have images of having to build a hatch in the center of the roof and plumb water to a rooftop hosebib - sounds weird.
Is is correct that, w/ current module design, a shadow on one part of the module (say, a leaf), reduces the output from the whole module?
How can one estimate how much sun a given location gets per year? I assume latitude, climate, panel direction/angle all factor into it. Assume no shadows from trees/other buildings. Is there a online calculator where I can plug in a location and get a reasonably decent estimate?
It looks like James, your scenario equates to 6 hours/day of full sun - but that's got to be specific to TX and similar South/SouthWest locations?
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Solar output depends on where you are and your clearness ratio. In Houston, we can expect 5 times the nameplate rating in watt-hours, averaged over the year. In So Cal, the number is closer to 7. You only get "full power" when the panel is exactly lined up with the sun. But the sun shines for an average of 12 hours a day.
If you put the panels on a tracking system, you can increase the watt-hour ratio by quite a bit, but that is usually offset by the cost of the tracker. They look cool, though!
Maintenance: Yeap, you need to clean the panels periodically for maximum output.
Life: 30+ years. Most of the panels will degrade over time and they are generally guarenteed to produce 80% of the nameplate after 30 years.
Failed panel: It depends on how the system is wired. If the panels are in parallel, then you only lose the power from that panel. For larger arrays, the panels are in "Strings". The entire string is affected by a bad panel. The design of the system depends on the characteristics of the inverter.
The SMA Sunnyboy is designed to work best with your peak voltage from the panels at 480 volts. If the panels nominal best output is 30 volts, then strings would be best to be 16 panel units. The voltage range of the Sunnyboy is 250 to 480 volts. It will adjust the operating voltage on the panels until it gets the most power. With lower light levels, this is important. It is called MPPT (Maximum Power Point Tracking). If you use 10 panels, then the inverter will only work when the combined panel votlage is above 250, but they max out at 300!
Again, I might choose either a different inverter or play with which panels we pick.
If you go with microinverters, each panel has its own inverter and MMPT system. A dead panel only removes that panel. The panels are tied together on the A/C side instead fo the D/C side. And the better microinverters have IP over AC and will connect to a monitoring unit and you can see the power producition and the condition of each panel.