Solar panel efficiency August 28, 2020, 01:14:42 pm Yesterday afternoon, I noticed that my 5 panels were only pumping out about 7 amps, and my battery bank, normally at 100% by 5 PM, was only at 94%. A friend asked when I had last cleaned my panels. "Years," I replied. "I let the rain take care of it." Well, with all the smoky haze we have gotten the last few days, and with a light shower one night, I decided to go up and at least take a look this morning.Instead of being blue and black, my panels were somewhere between tan and brown. After a bit of washing, I climbed down and checked the output. At 9:15 they were cranking out 11 amps, and by 10:05, they were up to 17 amps.It is hard to imagine that the particles causing all that haze did so much to block the panels, but a week ago, the panels would routinely crank out over 20 amps midday. Live and learn...Ken F in WY 1 Likes
Re: Solar panel efficiency Reply #1 – August 28, 2020, 01:22:13 pm "...imagine that the particles causing all that haze..."Also imagine what 4" of snow will do, clean panels or not? How do I know? 2 Likes
Re: Solar panel efficiency Reply #2 – August 28, 2020, 02:26:21 pm Unrelated to panel cleanliness, but solar panels do degrade over time at a rate of about 1% per year.
Re: Solar panel efficiency Reply #3 – August 28, 2020, 03:56:09 pm I've done a few experiments over the years, comparing solar panel output before and after cleaning really dirty panels. To my surprise, it didn't seem to make a lot of difference. However, I have a hunch that when the sun is low in the sky, dirt on panels would have a much greater effect than at noon. So it's still a good idea to keep 'em clean.But as for smoke haze, that's a different story. I've found that it seriously affects solar output--much more than one might think just from looking at the sky.
Re: Solar panel efficiency Reply #4 – August 28, 2020, 11:18:06 pm Solar panel cleaning is big business. Some companies claim a 35% increase in efficiency. Personally, I’m topside on the LD every week or so to clean the array on our LD. A soft microfiber towel and a quart of water is all it takes. Of course that ladder can be a bit intimidating. 🙀Bright and shinny saves the sun. 🌞Kent
Re: Solar panel efficiency Reply #5 – August 29, 2020, 09:12:45 am without going to deep into the weeds .... Depending on the solar panel manufacturer different panels respond to different parts of the 'light' spectrum. I.E. the spectrum of light is the issue (I'm going to leave out the temperature issue but its an important part also). Clouds generally don't reduce the output as they don't block infrared and ultraviolet but smoke haze can. Smoke haze is a particulate. So is dust. It's very difficult to compare solar panel outputs between folk. Even when we are right next to each other. No two rig setups are identical is all parts.Bottom line you get what you get when ya get it.glen 1 Likes
Re: Solar panel efficiency Reply #6 – August 29, 2020, 10:42:39 am Glen, it is interesting that you say that clouds don't reduce output. On an overcast day, my output is dramatically less than when I have clear sky overhead. After 12 years of fulltiming, relying on my panels for more than half the year, this is not a guess. With full sun, I will get up to about 28 amps coming into the battery bank. On a cloudy day, I would expect less than half of that.Ken F in WY
Re: Solar panel efficiency Reply #7 – August 29, 2020, 11:56:19 am It's difficult to compare clouds and smoke haze, since both are difficult to quantify. It's true that clouds can pass a fair amount of ultraviolet light--I don't know about infrared--which is why it's possible to get a sunburn on an overcast day, although of course it takes longer than on a clear day. But clouds definitely do reduce solar panel output. I've been using them for fourteen years in all kinds of weather, and there's no doubt about that.
Re: Solar panel efficiency Reply #8 – August 29, 2020, 12:21:06 pm Quote from: Kenneth Fears - August 29, 2020, 10:42:39 amGlen, it is interesting that you say that clouds don't reduce output. On an overcast day, my output is dramatically less than when I have clear sky overhead. After 12 years of fulltiming, relying on my panels for more than half the year, this is not a guess. With full sun, I will get up to about 28 amps coming into the battery bank. On a cloudy day, I would expect less than half of that.We have been in the Eastern Sierras for the past 15 days and have had all sorts of weather, including a lot of clouds. During several days in Mammoth, we received minimal solar, due to the clouds from the tropical disturbance that caused the thunderstorms that ignited hundreds of fires.During this time, we received less than half our normal solar charging and ended up using more battery power that what was gained during the day. The heat and humidity required running the two roof fans 24/7.It’s times like this that I’m happy to have a propane powered refrigerator and not a 12-volt compressor refrigerator. It would have required a generator run each day to provide the needed power.When cleaning the solar panels, rarely has more than an extra amp or two been observed, they need to be extremely dirty to make a significant difference.Larry
Re: Solar panel efficiency Reply #9 – August 29, 2020, 12:22:08 pm I have found that current technology solar panels respond far better than older ones to shading of various types. This is comparing panels installed in the early '90's to those installed in 2012. However, confusion may come when comparing performance recharging heavily depleted batteries to those that are less than 30% discharged. Batteries which are NOT heavily discharged will only accept a certain rate of recharge, regardless of the solar charge capacity. Thus, someone who tends to be power conservative - like us - notices little difference in the charge rates on clear days vs. those with some overcast or cloudiness. Others may notice a large difference if they draw the batteries much further down overnight.Steve
Re: Solar panel efficiency Reply #10 – August 29, 2020, 12:55:02 pm Steve, you make an important point. I've been fooled more than once by checking solar panel performance when batteries were only slightly discharged. With LiFePO4 batteries you can get away with this, since they accept juice at their maximum rate right up until they're fully charged. But with the far more common lead-acid batteries, unless they're pretty far down and the charger is in bulk mode, you don't get a true idea of what the panels can produce. This is easy to overlook. ;-)
Re: Solar panel efficiency Reply #11 – August 29, 2020, 01:08:32 pm "It's times like this that I'm happy to have a propane powered refrigerator and not a 12-volt compressor refrigerator. It would have required a generator run each day to provide the needed power."Good point, Larry. As with most things, there are tradeoffs with each type of fridge.
Re: Solar panel efficiency Reply #12 – August 30, 2020, 05:45:14 pm <smile> like I said there are just two many variables to make a solid statement. Old vs new - thick vs thin clouds - type of batteries - state of charge - type of pollution - time of year vs time of day etc etc etc. Bottom line small changes can make a large different on the end result. I don't disagree with any persons observations. glen 1 Likes
Re: Solar panel efficiency Reply #13 – August 30, 2020, 05:59:28 pm Quote from: colddog - August 30, 2020, 05:45:14 pm<smile> like I said there are just two many variables to make a solid statement. Old vs new - thick vs thin clouds - type of batteries - state of charge - type of pollution - time of year vs time of day etc etc etc. Bottom line small changes can make a large different on the end result. I don't disagree with any persons observations. glenAs you say, Glen, "It's all good....."Chris 1 Likes
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