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  • khanh dam
    replied
    awesome glad to see someone who actually cooled thier panels with rain water here on this group

    Leave a comment:


  • khanh dam
    replied
    lol yes i agree UV damages panels.
    It's rhetorical

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  • SunEagle
    replied
    Originally posted by khanh dam View Post

    wrong. i have pointed to real life ambient RAINWATER system and a discussion of the good and bad of the system.

    you have consistently argued about using COLD water systems, and act like that is what I said, obviously wrong. anyone can read the discussion and see that.

    solar panels are made to be used outside and in the rain. what's next you are going to warn them that UV light can degrade them? sky is not falling, so no need to warn about it.
    But the sky could be falling if someone that did not follow the rain barrel water instructions perfectly and ended up greatly degrading their panels and investment.

    I don't understand why you like to argue with me when I am just trying to point out it is better to be very cautious when it comes to maintaining a solar pv system which most people do not understand and can hurt their financial investment.

    And by the way UV light and heat does degrade a solar cell. The amount depends on the type & quality of the cell and the amount of sunlight that hits it. And that info can be found in any research document that studies pv cells. I know because I worked in a research center at the U of D when we were experimenting with Cadmium Sulfide solar cells. First these thin film cells did not produce a high efficiency output or lasted long under high heat so they were abandoned as a solar pv cell go to.

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  • khanh dam
    replied
    Originally posted by SunEagle View Post

    And you are asking people to believe what you tell them.
    wrong. i have pointed to real life ambient RAINWATER system and a discussion of the good and bad of the system.

    you have consistently argued about using COLD water systems, and act like that is what I said, obviously wrong. anyone can read the discussion and see that.

    solar panels are made to be used outside and in the rain. what's next you are going to warn them that UV light can degrade them? sky is not falling, so no need to warn about it.

    Leave a comment:


  • SunEagle
    replied
    Originally posted by khanh dam View Post

    have you taken a swim in a 55gallon barrel of rain water that is sitting outside (at ambient temps) ready to be pumped onto solar panels to cool them?
    cause that is the ambient water source that normal people would use

    maybe you are thinking of doing a rain dance to cool the panels? if that is the case your comments are correct.

    Actual 15 year old working prototype trumps any theoretical discussion or fears of rainwater damaging the panels. Internet is full of folks who type about what they think. Very few people actual put their ideas into practice. Even fewer look at a 15 year old working system and claim it doesn't work. IT seems as if some are saying: Don't believe what your eyes see. Believe what I tell you.

    anyways I'm done talking about this. it was only brought up as a possible research topic that would be better than cleaning, but like many things on this forum, it turns into an argument topic.
    And you are asking people to believe what you tell them. Which can lead to someone without true understanding to hurt their system.

    I am just trying to warn people that putting water (of any temperature) onto hot panels may cause stresses that can degrade the panel. If they are going to wash the panels then try to not do it when they are very hot.

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  • khanh dam
    replied
    Originally posted by SunEagle View Post
    Well I have been out in a rain storm and the drops were not warm or ambient temperature.
    have you taken a swim in a 55gallon barrel of rain water that is sitting outside (at ambient temps) ready to be pumped onto solar panels to cool them?
    cause that is the ambient water source that normal people would use

    maybe you are thinking of doing a rain dance to cool the panels? if that is the case your comments are correct. LOL. it's a joke dont' take it personally.

    Actual 15 year old working prototype trumps any theoretical discussion or fears of rainwater damaging the panels. Internet is full of folks who type about what they think. Very few people actual put their ideas into practice. Even fewer look at a 15 year old working system and claim it doesn't work. IT seems as if some are saying: Don't believe what your eyes see. Believe what I tell you.

    anyways I'm done talking about this. it was only brought up as a possible research topic that would be better than cleaning,

    no one said to use "COLD" water, rain water was the term used and obviously that is stored in a bucket and close to ambient temperature.
    Last edited by khanh dam; 02-25-2021, 09:47 AM.

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  • J.P.M.
    replied
    Originally posted by khanh dam View Post
    rain water is ambeint temperature, it doesnt' come from a cold house from a ground well located near a glacier.
    never in the history of solar chat forums has any one claimed cold rain destroyed their solar panels. with our without clouds.
    Can you explain the logic or scientific basis of why you think rainwater is at the ambient air temp ?

    Looks to me like you're again out of your knowledge base. You statement makes me think you're ignorant of what influences the temp. of precipitation.

    The temp. of rainwater (or ice or snow for that matter, but probably not applicable to this discussion) may be higher or lower than the local ground level ambient air temp. and will be more dependent on the environmental conditions present when and where the water vapor begins to condense to liquid, and also dependent on the environmental conditions the liquid passes through on the way to the ground.

    Also, while I've not yet performed an exhaustive search through the history of solar chat forums as you seem to imply you've done, I can't verify or refute your claim that it's not been reported that cold rain destroyed a solar panel, but I'm pretty sure whether or not cold rainwater were to, as you write, destroy a panel, that if such a calamity did occur, clouds were present somewhere in the vicinity of the damage, making me curious about the sense of your "with our (sic) without clouds" statement. Reason for my curiosity: Last I checked and the way I learned it, it takes clouds (water vapor) for precipitation to form. But I'd probably agree that rain water doesn't come from houses, cold or not, and that rainwater doesn't originate in wells.

    IMO only, this forum would be better off if you checked the accuracy of what you write before you mouthed off with respect to stuff about which you're ignorant.

    BTW, and meant as constructive criticism, your poor grammar, spelling, punctuation and sentence construction as you continue to exhibit here doesn't help you to be taken seriously. If someone - you, me, anyone - can't take the time, make the effort and have enough self respect to check their work, how can they expect readers to think they know enough, for example, about the physics and Thermodynamics of the earth's atmosphere to discuss precipitation temperatures and to be taken seriously rather than some semi-literate blowhard ?

    If you think I'm simply being argumentative, stay within your knowledge base and know your limitations, and watch the crap storms die away. Do that and your statements will precipitate a lot less of what you call argument, your stuff will need a lot less correction, and this forum will be better for having more accurate, or maybe better said (written) less inaccurate content.

    Leave a comment:


  • SunEagle
    replied
    Originally posted by khanh dam View Post
    rain water is ambeint temperature, it doesnt' come from a cold house from a ground well located near a glacier.
    never in the history of solar chat forums has any one claimed cold rain destroyed their solar panels. with our without clouds.
    Well I have been out in a rain storm and the drops were not warm or ambient temperature. For that matter they seem pretty cold to me. Remember that some storms produce hail which is ice and not warm.

    I mentioned the clouds because once they block the sun the panel temperatures come down from what they were before it rained.

    The overall issue is not how to clean the panels but can cold water damage them due to a larger temperature change. Maybe they won't crack right away but will they degrade over time? Most panels are on a roof and out of site for close inspection. How would someone know the panels are slowly degrading unless they can see damage. Or in most cases on this forum when panels start to fail or not produce they look at the equipment or wiring first. Maybe they need to look at the panels and see if there is moisture inside the glass.

    I agree that panels need to be cleaned but some type of caution should be taken when putting a cold solution on them when they are hot.

    Leave a comment:


  • khanh dam
    replied
    rain water is ambeint temperature, it doesnt' come from a cold house from a ground well located near a glacier.
    never in the history of solar chat forums has any one claimed cold rain destroyed their solar panels. with our without clouds.

    Leave a comment:


  • J.P.M.
    replied
    Originally posted by khanh dam View Post
    cooling panels in hot weather produces better results. guy on youtube used rain water and had impressive results.
    Typical simple minded you tube crap.

    Too many variables and too too little consideration/control of temps.

    A few random issues the video brings up in my mind that might need addressing:

    Rain water flows off a hot roof, the roof heats the runoff and the runoff takes a lot of the crap on the roof with it. Some of that will wind up on the panels when the runoff is pumped back to the roof. In the meantime, while all this is going on, the rain that hit the panels the same time it hit the roof at a temp. probably about midway between the dry bulb and wet bulb air temps or less has cooled the glazing on the panels, sending the glazing temp. in the direction of the dew point temp. So, the pumped hot water may well have the opposite of the desired effect of heating the panels. That may be less onerous and tolerable than dumping (hot ?) water on the (now cooler) panels and damaging the glazing or putting the panel seals under repeated FAST thermal dimensional and flexure strains not to mention glazing cracking from thermal shock of the pumped water because the RATE of the (rain) induced heat transfer is probably less than that of the pumped (and likely warmer) water as well as as the advantage the more evenly distributed rain will have to lessen the differential thermally induced strain on any single lite which is usually a less severe thermal shock than pumped coverage over a differential area. Then, when the rain stops, and depending on when the pump stops, it may well leave some of the stream bed load of crap from the roof carried by the pumped water to the panels which will tend to make the panels dirtier and mud up when everything dries up and thus lose performance.

    And, bottom line cost analysis, the possible (if any) performance gained by lower panel temps. - with no way of knowing because there appears to have been no0 attempt to measure it - will probably be a lot smaller than the time and toil invested in this modification.

    15 years of something that may not have failed yet is not a good definition of successful design as much as it's good luck. Good luck is not good design and says nothing about what most knowledgeable folks call fit for purpose engineering.

    I'm pretty sure a more thorough analysis than the cursory review given above would probably raise other concerns that would be a part of a serious more design effort than that video shows.

    You seem to imply or confuse discussion and exchange of ideas with argumentation. IMO only, one reason you may think that is because you are out of your league with respect to design of mechanical, thermal and electrical systems, and don't know misleading, and possibly dangerous junk and ideas like this when you see them.

    One big problem with you tube crap in particular and the net in general: No/inadequate vetting and so too much crap gets posted, seen and taken as gospel by people who will swallow anything.
    Last edited by J.P.M.; 02-23-2021, 04:49 PM.

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  • azdave
    replied
    Cold rain falling evenly across a large hot glass surface is not nearly as stressful as cold water being spray on the same hot glass but in a concentrated area like when using a garden hose.

    Leave a comment:


  • SunEagle
    replied
    Originally posted by khanh dam View Post
    I advocate just adding more panels to get more power, but if you want to do a research paper cooling might be better is all I am saying

    If your guy's theory was correct, solar panels in florida which get rained on almost every summer afternoon after being baked up to 110-130F and then cooled with say 90 F rain water would only last a few months correct?

    but they last just as long as anything else. you guys like to argue, but lets see you explain away a system that has been working for 15 years? video below:

    Well most storms here in Florida are proceeded by clouds so I believe the panel temperatures drop before it rains.

    But I agree that cold rain may drop the panel temperature a lot more then it should. It all comes down to what the manufacturer states is acceptable for a temperature range and speed their panel can be subjected to before it is stressed with possible cracking.

    I also don't always believe what I see on Youtube to be truthful but take what you want with that.
    Last edited by SunEagle; 02-23-2021, 12:33 PM.

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  • J.P.M.
    replied
    ARSAC:

    1.) Meant as constructive criticism, I'd get rid of that 30% improvement comment. First off, it's misleading in anything other than a desert climate, and not very likely even then. One example: The folks at the Furnace Creek Resort in Death Valley clean their 1.2 MW array every other year and figure about a 10 % performance penalty from panel fouling due to all sources, mostly dust, but also guano from flocks dessert starlings that inhabit the resort. Secondly, your looking for opinions, not giving them. You're biasing any data your survey returns. If your institution has a math dept. or an Mgmt. program, ask a math instructor or a marketing instructor in those dept's. about bias in a survey.

    2.) Are your group's design efforts primarily aimed at addressing the solar flat plate fouling problem, or creating a cleaning system for marketing purposes ? I'd choose one.

    3.) If this effort is for marketing purposes, what market(s) are you aiming at, commercial/large users, residential, or some other market ?

    4.) What research has your group done with respect to the causes and types of panel fouling as f(weather, array orientations, site location, local conditions, nature of the fouling, other) that would have an impact on design goals for a cleaning system ?

    5.) What research has your group done with respect to other types of systems that already exist that address the possible need for panel cleaning systems ?



    FWIW, in my opinion, with respect to flat plate solar panels that use glass as the glazing material, most residential PV applications don't need more than maybe a 1X/month or so hosing with tap water (in the A.M. before the sun has been up more than an hour or so) at a rate of ~ 3 l/panel with no wiping/squeegeing and followed by a simple air dry. Hard water spots on the array may impair performance some, but the data I have from various cleaning methods has shown that soaping and rinsing followed by more rinsing with distilled water followed by /squeegeing/wiping to remove hard water spots has no measurable improvement in cleanliness over simply soaping and rinsing with tap water and leaving the spots - and I note- the 3 l/ panel simple rinsing as described above seems to remove about 3/4 -90 % as much of the fouling as a thorough cleaning.

    I live in what can be described as a semi arid climate (zip 92026). If it doesn't rain, and it commonly doesn't rain much around here from ~ April to Nov., my array fouls at a rate such that performance rolls off off about 0.75 %/week +/- a bit with a lot of the fouling that does show up due to morning dew that cakes up the prior day's dust and adds to the fouling load. A decent rain (maybe > 0.75 cm or more) will probably restore maybe 2/3 to 3/4 of the array performance lost due to accumulated fouling.

    One other think I've noticed about my array's fouling rate: It seems to exhibit some asymptotic behavior. The first maybe 4-6 weeks the rate of fouling seems to be linear at that 0.75%/week as noted above. After that, the rate of fouling seems to decrease and sort of stop increasing so that after maybe 8 - 10 weeks the fouling may level off at maybe 10-12 % or so and not get any worse. That most likely may be a local phenomenon or the end rate may well be and IMO, probably is quite site dependent, but I'd note that skylites don't become opaque from dirt so I'd guess that, averaged over some time period, the rate of dirt deposition on and removal from non vertical surfaces exposed to the environment become equal at some point, and I'd also postulate that the rate does so in an asymptotic fashion.

    What all the above mental spoor comes down to is that if your group's efforts are aimed at a learning experience in a marketing exercise, it needs more focus. If the goal is to design what could be described as a "clean in place" system, and the market is residential, I don't think there's a market for it for several reasons, the biggest one being it isn't needed. The second biggest is it's impractical as well as maintenance prone and located in a place where people won't go. Third, people wo buy PV overwhelmingly have two goals for getting residential PV: a lower electric bill for the lowest upfront cost as possible. A costly system add-on that probably will need maintenance (which it will most likely not get BTW) as well as looking unusual if not downright unsightly may have a steep climb to marketability. All of those comments apply in spades for any snow removal equipment.

    Best of luck in your educational efforts and perhaps your future engineering careers. It can be one of the best times of your lives.

    Stay curious always, learn the see the world through an engineer's eyes and make the world a better place through your efforts. Keep your instructors on their toes by asking tough and focused questions formulated through critical thinking. Believe it or not, they'll appreciate it.

    Leave a comment:


  • khanh dam
    replied
    I advocate just adding more panels to get more power, but if you want to do a research paper cooling might be better is all I am saying

    If your guy's theory was correct, solar panels in florida which get rained on almost every summer afternoon after being baked up to 110-130F and then cooled with say 90 F rain water would only last a few months correct?

    but they last just as long as anything else. you guys like to argue, but lets see you explain away a system that has been working for 15 years? video below:

    Solar powered solar panel cooler system - YouTube

    youtube comments from creator below:
    This system is in Melbourne, Australia. This cooling method cannot damage the panels because it is just a spray of rainwater and the panels are obviously designed to be rained on. Also, the cooling limits how hot the panels can get so that could possibly extend their life. The cooling system has been running around 15 years now and just last week the panel temperature sensor (or sensor wiring) appears to have failed, which is the first controller issue it has had. I haven't had a chance to work out what is wrong yet, but the temperature sensor is just a cheap thermister so it should only cost a few dollars to fix.

    further on here are devil's advocates against system:

    The Dummy Spit1 year ago
    You have a small system, 2-3 Kw at best. You would be far better off getting some used panels and adding a second string on the same inverter. Yes, You can over clock the inverter and NO it won't hurt it. It will give you more power earlier and later in the day and when it's a cloudy day as well. Alternatively if you are a worry wart and have to do everything by the book the corrupt power co's set down, Just get an up to date 5 or 6.6 Kw system. It will be paid back in 3 years and you'll be making loads more power and saving a lot more money thereafter than mucking round with this. Improving output 20% on such a small system that you have modified and spent money on 3 or 4 times now is kidding oneself to think you are in any way ahead. The system is old and outdated for a start and trying to improve it is an exercise in Futility.


    Michael Porter1 year ago
    It is a small system but I can't upgrade it without losing my over 70 cents/kwhr feed-in tarrif. The upgrades have easily paid for themselves even though it is small and I enjoy the process.REPLY

    The Dummy Spit1 year ago (edited)
    @Michael Porter So how much extra has the cooling given you per year in KW or FIT? What is the actual size of the system?REPLY

    Michael Porter1 year ago
    @The Dummy Spit It's only a 1kW system. It is hard to estimate, but I'd say it might give me an extra 150kWh per year at $0.72 feed-in tariff is an extra $110 per year. It's been running for at least 10 years with virtually no running costs. It's not much, but it's not nothing.REPLY

    The Dummy Spit1 year ago
    @Michael Porter The chances of you getting 150KW a year extra with a 1KW system in Melbourne with cooling panels are virtually non existent. In summer the pump would have to be running so much it would eat up any power savings easily not to mention what the controller draws over a day. Might be small but there's not a lot to to play with here at the start. You would be far better off to upgrade the system and forget about the .70C Fit. There are deals where you can get .50 C now on systems under 10 KW so you are really making a false economy both ways. Clearly you are not going to listen to anyone but others would want to think twice about this because it's a waste of time and effort for no worthwhile reward. I have done the tests and measured all the factors accurately and it's much better to just add another panel or 2 to the system and be done with it.
    Show lessREPLY

    Michael Porter1 year ago
    @The Dummy Spit This video is just a record of what I've done- I'm not selling anything or recommending others do this. For the record, the pump and all electronics are completely powered by a separate small solar panel so there is no electrical cost of providing this cooling. Most of the equipment required were items I already had or were very cheap because otherwise the payback period would easily blow out. I agree extra panels are the best way to increase output - and that's why tracking systems for example are very hard to justify.1REPLY

    BoomBrush10 months ago
    in australia, at least in the state i live in (QLD) you aren't allowed to change the size of the inverter if you wish to retain the government feed in tariff. adding more panels may be possible but only if the capacity of the panels remains under the inverter's nominal operating level. so sadly this isnt an option for some REPLY

    The Dummy Spit9 months ago
    @BoomBrush It's an option if you don't let corrupt and greedy power companies take advantage of you. I sure as hell don't!!
    Last edited by khanh dam; 02-23-2021, 10:12 AM.

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  • SunEagle
    replied
    Originally posted by khanh dam View Post
    cooling panels in hot weather produces better results. guy on youtube used rain water and had impressive results.
    I would be careful when I use water to cool the panels. If they are very hot during the daytime the glass may not like the sudden drop in temperature and end up cracking or being stressed beyond their design.

    If the water temperature was just a few degrees lower then the panel it may work but if we are talking about cold or even cool water on a very hot panel, I would say don't try it.

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