I have an ideal south facing roof for mounting panels, have been dragging my feet on the purchase on panels was close a few times recently one package system looked promising but it lacked the MPPT charge controller so I passed. Also have been linked to the Alibaba site watching the 2 volt batteries, but just can't get a good feeling about that type of purchase . Figure a pivot pole mount is the ideal way to install vs the roof, way easier to remove snow, maintenance etc...
Agreed. Though more "visually unattractive", having them on a tracking pole has it's advantages. Increased power collection is one, but so is avoiding snow piling up when "parked" when not sunny. (also protects against hail damage too)
Sent from my Samsung Galaxy using TapaTalk 2
Hmmmm. You're a real smart guy, Rod -- and I'm sure you've thought this out fairly well -- But I wonder if you're not throwing the baby out with the bath water(?). Or maybe I'm missing a piece of your set-up.....Originally Posted by rreidnauer
Heck! Usually one makes an effort to NOT have snow sliding off, (i.e.-snow birds/fence/guards) but I see your point. Hmmmm! You just gave me an idea. I was starting to temporarily setup some of my big panels today, (need more power with these continuous dreary days) and thinking about having to clear snow from them just about every other day lately. Think I will give them the RainX treatment. That'll make life a whole easier!
This is one example of the nice things about MPPT. I'm series wiring the panels to produce 72 volts. That allows me to send the power further (from where more sunlight is available) with smaller wire size and lower line losses, and still be able to charge the RV's 12v batteries. My big problem right now is deciding where to mount the dang controller. Not a lot of wall space in an RV, ya know?
Sent from my Samsung Galaxy using TapaTalk 2
True, the higher voltage (and lower current), will result in lower IxR voltage drop across a long, small dia cable run. But if you're series-ing 7 panels, you're limiting your total available current to about what ONE panel is capable of (say..... 5Amps, for reference / example). Or, whatever the Max realistic current is, for 1 panel. If all 7 panels were paralelled, you'd produce 5amps x 7 panels = 35 Amps (at 12+VDC.....at the panel-end of the cable run). If you had an 8th panel, you could make "the best of both worlds", by series/paralelling your panels in a configuration of 4 banks in parallel of 2-serially wired panels, to produce 24VDC at 20amps (or a 48vdc system at 10amps). At the end of the day, it's the current that provides charge to the battery bank, of anything at/over ~12.8vdc (for lead-acid).
That's MY thinking, anyway. Or maybe there's something I'm missing? THAT's entirely possible too
Believe I'd be placing MPPT as close as feasible, to the battery bank. And hopefully they are somewhere with plenty of ventilation!
Black panel frames do help a little bit in keeping light snow away from the perimeter of the panels (once the sun hits them), which then has a better chance of sluffing off or being blown off. This is something I'd done at a remote (mountain-top / helicopter-access only), comm's site. But we still ended up having to clear the panels manually, on most visits. To suppliment low sunlight in Alaskan winters, I had rigged a 10kw generator (to run a battery charger), so I could engage the glow plug, start, and later stop the generator, via two-way radio link. THAT was before smart-phones (or even cell systems), were invented. Today -- I'd consider a grid of heating elements on the back of the panels, that could be switched on as-needed (run off of commercial or gen power), similar to how we currently "de-ice" satellite antennas in winter.
Share your thoughts on the 72VDC config, vs 24 or 48vdc config Rod. But don't embarrass me too much, if I missed something completely obvious
Cheers!
Ak, I think rod was saying that line resistive losses are solely a fnc of current. That's why utilities step down amps prior to long distance transmission. (you can't use a transformer on dc). An mmpt controller can take in say 72 volt @ 5 amps, and output 12 volt @ 35 amp, with very little loss.
Peter, working the dream
www.youtube.com/stressman79
photobucket/site address: http://s319.photobucket.com/albums/mm471/stressman79/
Peter has it exactly right. And ironically, even the amperage examples turn out to be exactly what I am working with! (I am putting up two 175 watt, 24 volt panels, which produce maximum power at 36V @ 5A)
MPPT controllers are basically a computer with different charging algorithms, manage different voltage combinations, and excel at being able to "throttle" the current to maintain specific panel voltage which extracts the maximum wattage possible. Additionally, it doesn't just target one single voltage, rather it test sweeps to determine which is the best throttle setting. This is what really sets these controllers a part from the rest, because it makes the most of what is left in waning light, such as in the evening, early morning, or hazy/partly cloudy conditions. (or in the case of original question, panels not receiving sunlight directly head-on)
They are the only controllers capable of extracting the full rated wattage of the panel. Makes me wonder why anyone would use anything else. (of course, I'm guilty of currently using a simple switching controller, and only getting about 75% of the wattage from the panel because of it) I guess others exist for small system use, and are a good, low-cost option for simple maintanance charging, but for off-grid life, and the demand for power that comes with it, I can't imagine not wanting to harvest every watt feasible.
Sent from my Samsung Galaxy using TapaTalk 2
Following the argument for MPPT controllers, I have a real world example of their capabilities. Since last posting, I upgraded my operating solar system to two 175w rated panels and a MPPT controller. The other day, I had a brief period of absolute sapphire skies and a blazing sun, so I decided to run a high load test and see what the controller could really pull out of the panels. Turning on every load I could (which isn't all that much) to prevent the battery from reaching a full state during the charging test, I managed to hit 404 charging watts! That's 15.5% over rated output!
I don't know if cheaper thin-film panels would respond the same, but I was surprised to see such a large (or any) overage on these old monocrystaline panels. Needless to say, I'm quite pleased with the results. Now I wonder if I'll be able to get 15.5% extra out of the full array (2100 rated watts) once it's up. (a potential extra 325 watts for free!)
Sent from my Samsung Galaxy using TapaTalk 2
Last edited by rreidnauer; 03-28-2013 at 06:14 AM.
Excellent info! I appreciate it!
Marv
"Where there's a will, there's a way"
I predict if and when the new Hyperloop is designed and implemented (as a prototype) by Elon Musk, solar panels will drastically fall in price. The whole concept runs off of solar power, and the amount of solar panels it takes to drive this new transportation would be quite a bit. More solar panels bought = price dips. Then again, some people have said prices have dropped 20 percent every year - http://monetaryrealism.com/solar-is-...nge-our-world/
Couple more years and solar panels would probably be economical for just about anyone it seems.
Along those lines, I thought this article was very interesting. Talks about the big power companies and how private solar is set to change the way they do business.
http://www.businessweek.com/articles...ies-irrelevant
Interesting article. Worth the read.
edkemper
Class: Valentine's Day weekend 2009
Feel the Bern!
Posting Permissions
Reply With Quote
Bookmarks