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Bando:
I'm not sure I'd hang my hat on being able to see the effect of rain on production. 1 - assuming 01/29 and 02/01 are identically clear , the arrays will see more sun because of the changing solar geometry I just mentioned. 2 - every degree of temp. diff. will change the arrays' output probably by something like .3 to .5% per degree F. Around here 01/29 ave. temp. was 64 F. Tomorrow's predicted high is 59. We're close geographically. I'd expect similar but not identical conditions.That ambient, BTW, is only part of what determines panel temp. The wind has a lot to do with it as well. 1 and 2 will likely give uncertainty of maybe 2-4 %, maybe more, maybe a lot more, probably on the plus side. If the rain washes off the dirt and that results in a further increase, how will you separate that increase from the effects mentioned ? I'd suggest you have too many unmeasured variables with too much inherent uncertainty of the same approximate magnitude as what you are trying to measure. I think it's a lot of fun, but I'd not assign a lot of confidence to it. I cleaned my array on the 14th and with a lot of data from the 3th and 14th still got little better than what I'd describe in the end as an educated dart throw. See prior post w/results in this thread.
FWIWComment
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yes I won't know for sure however if it's sig higher than 53 I will suspect the rain had something to do with it. That's assuming tomorrow is as sunny as it was on Wednesday . I don't recall the exact temp on Wednesday (2 days ago) however I know I've been sending my boys to preschool in long sleeves all week so it wasn't warm.
I don't know how dirty your panels get but mine were really filthy prior to last night.Comment
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The high here tomorrow says 63 btwComment
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before and after pic for comparison
before = 1/25/14, so you need to add another 5 days of dust accumulation to that
after = 1/31/14, rainfall the night of 1/30
dusty3.jpgrain2.jpgComment
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Panel cleaning
Yea you guys have it tough. A week ago my array made 89 KWH, but today
with ANOTHER snow storm going on, I'll be lucky to do 20. Bruce RoeComment
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here are some results. a few observations/notes to preface:
- January 29 was a sunnier day than February 1. big, billowy, passing clouds on Feb 1 entered my area and shielded the full sun from the arrays from about 11:30-1:00. (i know this because we were outside with the kids)
- January 29 production was the highest we have recorded to date, at 53.2. the bell curve on the production is pretty much ideal/perfect, showing the hour by hour output climb and descent
- first rain in many many weeks (nearly 2 months) arrived on night of January 30, early morning of January 31. i previously hosed off the larger array on January 11.
- max instant output on February 1 was in the low 9's for quite a while on February 1 during full sun. i have not seen anything past 8.4 in a very long time
January 29 production.jpgFebruary 1 production.jpg
it's difficult to account for the loss of production from 11:30-1:00 on February 1, so if you just go the super conservative route and enter the January 29 data for Hour 11 and Hour 12 on February 1, you get the following chart:
Hourly.jpg
as you can see the hour by hour increases over the 72-hour period are not trivial, IMHO. and again, that's taking the conservative route for Hours 11 and 12, which probably would have been at least 5% higher than what I have in the yellow cells, based on the other hours production during the day. the end result would have been 56.5 kwh, which is over 6% increased output over that 72 hour period. maybe you want to remove some % for the fact that days are getting longer, however it wouldn't be that much.
in any case, i think the cleaning by the rain had a significant impact on my particular panels covered in dirt and dust. results will obviously vary for other people depending on where you live and how dirty your panels get. but i think this establishes a pretty good baseline for my situation -- that dirt/dust accumulation over a prolonged period can amount to at least 5% loss, and i would argue again that when i have some window cleaners actually clean and squeegee them, the total loss could amount to even more. it also matches the results from a few weeks ago when i started this thread - hosing off only the larger array achieved about 4.2% increase in output over a 24 hour period.
anyway, it was an experiment and learning experience for us going forward as new solar energy producers. hopefully drought-like conditions do not persist in So Cal, however i think it's safe to say that during the summer, a few hosing offs and maybe an annual window cleaning will be in order ...Comment
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Those are pretty much in line with my January experiments of about a 6% increase after cleaning. January turned out to be a very good month output-wise (significantly higher than January 2013). Alas, some of that must be due to the absence of precipitation (therefore less clouds) which is atypical for Phoenix in January. At least our drought conditions are not yet as extreme as California's.Comment
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Jan into Feb
The shortest day, about all I could get was 70 KWH. 29 Jan managed to make power for
10 full hours, 89 KWH. Snow storm 1 Feb stopped by 11 am, cleaned off the snow. Still
pretty overcast, but managed 23 KWH. 2 Feb few clouds, 80 KWH. Today 3 Feb
even less clouds, 92 KWH. Bruce RoeComment
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Bando:
I appreciate your work and encourage you to continue. But, I am of the opinion that what you have done here, while interesting, does not warrant the confidence in the conclusions you seem to have reached. They are most certainly valid opinions, and worthy of respect, but any validity or confirmation of your conclusions will, IMO, need to come from other sources. I'm not saying my data was, or is any better, but it's probably not less accurate. My data doesn't lead me to believe much more than a 1-2 % improvement in performance from vigorous soap/H2o/cloth cleaning, much less rain by itself. For the 01/29 to 02/04 dates you describe, for beginners, the solar irradiance for the days you mentioned, (01/29-02/01/2014), the daily totals were similar, probably within about 1% or so, but the character of the irradiance throughout the day was quite different. 01/29 had high cirrus most of the day that reduced irradiance from clear sky values something like 5-10% more of less consistently throughout the day. the sky was sort of grayish blue. The 2d was pt. cloudy in the morning and part of the early afternoon. The rest of the 2d was clear with blue sky. The result was about 10%below clear sky values. The big difference was in the temp. I'm aware our locations are about 20 miles apart and I believe I understand, perhaps better than most how much local conditions can vary over short distances. However, I have a hard time, knowing what I know about local conditions and topography that there is much of a temp. diff. in our locations for the same time periods. On the 29th my temp. between the hrs. of 8 A.M. and 4 P.M. averaged 76 deg. F. on 02/01 it averaged 54.9 deg. F. for the same time period. That temp. difference alone will amount to something like, VERY roughly 3 to 5% increase in output on 02/01 from 01/29, even without the likely additional panel temp diff. brought on by the generally windier conditions. I'd respectfully suggest the temp. and wind profiles alone for those days likely changed output enough to lose any ability to measure any effect on panel cleanliness due to any rain in the "noise" of the effects of the other data such as difference in irradiance, and especially temp. difference during daylight hours. What I did recently as reported here may have been an attempt at some accuracy, by attempting to account for the major variables as measured in a systematic way, using equipment that while not primary standards, are traceable to a primary standard and within 6 months of most recent calibration and probably good to a few % +/-. I think I got pretty good data, and it was still a dart throw. BTW: The theoretical increase in horizontal clear sky irradiance from 01/29 to 02/01 is something like 2.7% - ~~4,190 W/day*m^2 to 4,307 W/day*m^. I measured 3,934 and 3 894 same units respectively for the 2 days. Thus, 02/01 was a bit less sunny making the situation for accounting for cleaning effects murkier still. Bottom line, I believe the variables are varying more than it's possible to measure the cleaning is/is not working, but keep up the good work.Comment
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On azcleansolar.com, which is a solar cleaning website, one of their testimonials reported 8.4% increase in daily output and 7.5% increase in peak output. The owner posted to show a before/after picture with dirt buildup due to a bad dust storm.
Thought I'd just pass along the info here. You can take it for what it's worth, because I'm not associated with this data point in anyway except I came across it. They actually have an ad banner on this forum and that's how I found their website.
But this company uses the pure water cleaning approach using the water fed pole like I mentioned before.
It's also interesting to see on their home page, the pics of the city water hose test before and after. They could have deliberately done a lousy job on the water hose test, I don't know. I find it a little hard to believe that the water hose test would leave the panels looking that bad from afar. It should look clean, too, except that if the city water is hard, it may dry to show mineral spots on the surface.Comment
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JPM - while i appreciate your insight and relative expertise on solar matters on this forum, i do think it's important to point out that you don't seem to care or think it's relevant "how dirty are your panels".
my so-called "confidence" in cleaning results apply to me and me only. i'm not telling everyone to go out there and get a hose or pole and clean their panels every day. this whole thread started because my panels looked filthy, and i mean eye-sore dirty. like if you hadn't washed your street-parked car in 2 months dirty.
so i went out and tried to know FOR MY OWN SAKE what kind of impact cleaning would have, if any.
i understand you are claiming the difference is negligible based on your own experimenting and data collection, however i really don't understand how YOU can be so confident that i am "wrong" without knowing how dirty the panels are compared to yours! you talk alot about geography, topography, wind, sun, irradiance, temps, etc, but you haven't mentioned anything dirt-related. unless you can measure "particles per square inch" of dirt, i don't know how you can be so confident that your results are more applicable in my situation. there is new home construction every direction around me within a mile. new roads too. my initial thought is that this perhaps has contributed to how dusty they get. surely the amount of dirt is a contributing factor, isn't it?
on a side note, you seem to want to poo-poo on almost anything i post, which is fine. whatever makes you feel better. i'm a moderator on a lexus forum and have dealt with and seen my fair share of all types of members, good and bad. but what i don't understand is what is the point? ...
if i want to take 15 minutes out of my day during a drought to hose off panels and "waste" some water because (1) they will look cleaner and (2) my belief is that i'll produce up to 5% more - SO WHAT if i only get 1 or 2%, or even 0.01%. if anything, cleaning them won't HURT, will it?
if another member here wants to potentially oversize his/her system for perceived future increased use from EV and/or living more generously and not sweating it out in their home during the summer to save energy, what's wrong with that? does it matter if your ROI is 23% when it *could have been* 24%? does it matter if your payback period is 5 years and 4 months when it *could have been* 5 years and 1 month?
here's another example - if i want to drive my hybrid like a grandma because i believe i'll get 41mpg instead of 40, but i have no way of knowing if i am getting 41 because i used less A/C or there were more favorable stop-go traffic situations than usual, so what? i can't control or measure those instances, just like i can't control the sun and wind. but it won't HURT, so who cares if i only get an actual 40.01 mpg based on my driving style, if you could actually measure that to be the case? (and p.s., no i don't drive like that)
like i've said before, results can AND do vary, as with almost all situations in life. i'm not a rocket scientist and i'm not trying to win an award on solar cleaning. i'm presenting some data that i thought some here might find informative or interesting. if you find that cleaning your panels results in no real gain, hey great - that's more free time and less work - i'm happy for you. but i don't agree that, just by virtue of the proximity of our zip codes, you have invalidated my "'results" without also measuring how much dirt has accumulated.Comment
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