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Well here it is. Proof that shades affect my production after 5PM.
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San Jose is near the western edge of the Pacific Time Zone, and with Daylight Savings Time in effect, the amount of insolation left at 5pm is a little bit more than you might otherwise expect. There are several hours of the early evening left before the sun gets really low in the sky.
Still, nowhere near the effect as the same sort of shade at noon.SunnyBoy 3000 US, 18 BP Solar 175B panels.Comment
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Update on this. Today was a cloudy day. The microinverter system gave me 29 kwhr and 5 miles away, the Aurora (I thought it was SMA but it's actually Aurora) inverter was only able to achieve 23.6 kwhr. This system has no shades and routinely hit 30-32 kwhr on a clear day. I think for days like these the microinverters are far more efficient.Comment
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Wow! Thanks for the info! I guess the bigger question is: If you assume that this is 'average' for your two systems, how long will it take to recover your additional cost of installing microinverters instead of regular inverters? Anything AFTER recoup of initial cost differential is the 'gravy'.
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I have a tall palm tree on the east side and a small palm tree on the west side. My panels are on the west side and it gets hit with shades early morning between 10-12. It gets also get shades after 5PM. My satellite dish on my chimney (had I known I would install solar there, I would've asked them to move the dish). For 30 minutes, one panel is shaded. With a central inverter, the production for my entire array would collapse with one panel shaded.Wow! Thanks for the info! I guess the bigger question is: If you assume that this is 'average' for your two systems, how long will it take to recover your additional cost of installing microinverters instead of regular inverters? Anything AFTER recoup of initial cost differential is the 'gravy'.
Today is another cloudy day and I will report the production tonight. It could be that yesterday was an anomaly as losing 30% on cloudy days whereas the micro lost perhaps 5% seems odd. As for micro, the quote I received for the install of my system was lower than the other quotes for string inverters so there is no cost differential. All the benefits are gravy. I was able to track production on a per panel basis which allowed me to trim some tree branches that increased an additional .5-1 kwhr after 5PM. I am in the process of calling DirecTV to move that dish to another location. The difference is probably neglible with the micros, but I'm in the new shiny thing phase where I am trying to get the optimum production possible even with the early morning and late afternoon shade issues.
On a normal clear day, the string inverter system (with no shades) produces 30-33 kwhr whereas the micro produces 29-31 kwhr even with the early and late afternoon shades. Microinverters get a thumbs up from me.Comment
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The lower cost was between different installers rather than quotes from the same installer. You could find an installer that prefer micro as they are easier to install. They may knock off part of the install cost to cover the added cost of the micros. In California where Enphase dominates, some installers may be getting incentives to push Enphase.Comment
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Yesterday was an all around ugly day with no sun. String inverter system got 11.28 kwh and the micro got 10.6 kwh. This seems to confirm they share the same weather system. Without any sun whatsoever, I'm not surprised the string got better results as it normally does. Today will be another cloudy day but hopefully not as bad as yesterday. I'd like to see how they do with some sun among the clouds.Comment
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Today was a sunny but overcast day. The string inverter system which normally exceeds the micro system by 2 kwhr on a clear sunny day produced 26.94 kwhr. The micro system produced 28.4 kwhr. That is about 3.5 kwh reversal. It's not as extreme as two days ago. This may be more inline with the norm for cloudy days. I believe there are benefits to micros for days with shades. It's impossible to quantify based on the extremely limited sample size. I will revisit this after three months to see how the systems compare.Comment
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Science takes time and more samples. Keep recording.
One thing you don't list here is:
- which PowerOne Aurora model is it?
- how were your modules wired up? All to one MPPT or to both evenly?
- how do you have the Aurora inverter mounted - outside near the modules or inside with a long DC wire running to it?
This thread compares two similarly sized systems of about 5KW which use different modules and different inverters wired differently. It's not really a comparison of apples and apples but quite different environments, as russ says. If the modules on the Aurora are in both MPPT controllers - are the Voltage and Amps of each side showing the same power production? If not, you may have one module acting up in one of the strings.
The only way to truly measure production is a production meter near where the power is used. Using the Envoy software to measure output is going to show power at the microinverter and not at the point of usage (derated down-wire power versus point of production).
Let us know how you are capturing the production in kWh. Clouds are not all the same and production output varies widely based on height and density of clouds and if they are intermittent (lots of cloud-edge effect) or steady. String inverters also seem to work best during the height of power production (PowerOne produces an efficiency graph which helps to see that).
One thing Enphase does is provides their power output at point of production which makes them look better than string inverter production monitoring which may occur down the wire at a utility-grade production meter.PowerOne 3.6 x 2, 32 SolarWorld 255W monoComment
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This reminds me of a couple of years back on another forum when some clown was insisting his system was always right on with PV Watts predictions. As PV Watts is based on 20 year averages, for the most part, it is unlikely it will ever be "right on".[SIGPIC][/SIGPIC]Comment
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This was never meant to be a science experiment. I have no political point to score. I have access to two systems in the area in the same area, with the same KW system with different inverters and I like to share some observations. One system has shade the other doesn't. The one without shades consistently outproduce the one with shades on sunny days. On overcast days, the reverse is true. The information are all AC watts from SolarCity's "envoy" like device and Enphase envoy so they should be the same. If weather patterns are truly random, then statistically, it should even out over time rather than favor one system over the other (which over three months should prove). There is no way to explain swings of 3 - 8 kwhr on shaded days otherwise. No different panel maker at the same KW size could have wild swings like that. I thought this information could be useful for Solar users out there.
Instead of taking it for what it is, MY observations, I feel like this information is not wanted. Inferring that I'm a "clown" by a moderator tells me that I'm overstayed my welcome. It's never good to be called a clown by the site moderator.Comment
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