thin film performance

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mahendra
mahendra Solar Expert Posts: 181 ✭✭✭
in General Solar Power Topics #1
hi i would like a honest answer based on experienced rather than something out of a book or manual.
Disregarding the price or space requirements how do thin film solar panels perform in hot/high temperatures and low light conditions(and assuming i am using a mppt charge controller that is capable of tracking thin film power curves)?thanks .
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  • H2SO4_guy
    H2SO4_guy Solar Expert Posts: 213 ✭✭✭
    #2
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    Re: thin film performance

    I have 4 Uni-Solar 64 watt panels with frames and 4 of the 136 watt flexible panels. The rigid frame versions produce more energy, but the claim of wattage is optimistic at best. These are all setup to run around 80 volts or so voc. I use them to final charge batteries when you don't need large strings of high wattage. As the batteries get full the amperage demand goes down and that is where these really come in handy. I can switch them to a variety of charge controllers by just flipping a few switches. That way my larger strings of panels (840 watts each) are busy doing other important work like running the AC!!! Or stereo. I might be off grid, but I sure do like some luxuries.

    If you have shading issues, then thin film may work just a bit better, but if much of a panel gets shaded the amperage goes down so far that while you may have good voltage, you're not making much power, and that to me is the bottom line. They also don't last nearly as long as mono or poly versions. Grade B panels can be had for such a great deal it makes a convincing case for purchasing them. My last 7k of panels arrived to KC including freight and paying the dock folks for less than 70 cents per watt.

    Good luck and let us know how it goes.
    12K asst panels charging through Midnite Classic 150's, powering Exeltechs and Outback VFX-3648 inverter at 12 and 48 volts.  2080 AH @ 48 VDC of Panasonic Stationary batteries (2 strings of 1040 AH each) purchased for slightly over scrap, installed August 2013.  Outback PSX-240X for 220 volt duties.  No genny usage since 2014. 
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #3
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    Re: thin film performance

    One of the questions to ask--Are you interested in Spec'ed performance vs actual performance--Or do you have a limited amount of area to install solar panels?

    The big issue is usually a limited amount of square feet (or meters) to install the solar panel. So, a 500 Watt Mono-Crystalline panel will output 250 Watts on a (light) overcast days and a 250 Watt thin film panel will output 150 watts (instead of 125 watts) on the same day (just making up numbers here--The thin film are supposed to work better with diffuse/off angle illumination--I think).

    Because Crystalline panels generally are more efficient per square at gathering energy, they will still produce more power per square in reduced light (even if they are a little bit less efficient).

    Many thin film panels are somewhat flexible (crystalline are usually behind a sheet of glass), so can be a bit more tolerant to damage (rocks). However, I am not convinced that well built flexible panels will last longer than 2-10 years vs >20 years for well built glass panels (and I have had 3.5 kWH of "well built" crystalline panels under glass fail in ~6 years--So things do go wrong).

    And thin film panels usually need to be hermetically sealed against moisture and oxygen or they will fail quickly. Crystalline panels also do not like water or oxygen--But are much less likely to fail if small amounts of oxygen get past a seal.

    These are my questions/understanding... There are so many variations on thin film materials and panel design/construction/manufacturing--It is difficult to generalize without being contradicted when discussion specific panels/mfg.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    #4
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    Re: thin film performance

    BB is spot on.

    My thin-film panels (PowerFilm) do GREAT in 105F temps, no major efficiency losses at least as measured against 70F with a clamp-meter and ocv's are right up there. Shadowing is good - shade half the panel, and I get half the output. Put a leaf on my monocrystalline, and the whole panel is effectively gone.

    Long term shading - according to the "books", even though thin-film can stand this kind of reverse-bias shading temporarily, long-term it is best to avoid it. My use is only temporary, so I can't say either way - my thin films only go camping, but are chosen specifically to take some shading and still provide some useful output. All it would take is a small leaf to fall on my monocrystalline, and the charging hours are wasted.

    My PowerFilm's do provide more power under diffuse lighting than a monocrystalline as well - BUT is it significant enough to get excited about - no. Perhaps if the only thing I was doing was at the very end of a low-current absorb cycle, possibly. I think of it as an added bonus, but is never figured into my solar-insolation power-budget calculations. Then again, I'm only using pwm, so maybe someone else can comment on mppt thin-film tracking, which does make sense to try and get the most out of.

    Again the emphasis here is not to *purposely* plan on shading - even if they can take it temporarily. Decade-long projections on lifetime are kind of hard though so that's why everyone says go with monocrystalline with a guaranteed lifespan.
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  • Tecnodave
    Tecnodave Registered Users Posts: 437 ✭✭✭✭
    #5
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    Re: thin film performance

    I have 10 First Solar FS-275 (75 watts each) Cadmium Telluride Thin Film Panels, 24 Siemens MJ55 (55 watts each) monocrystalline panels, and 2 Suntech Wuxi Poly-crystalline (280 watts each) so I have just a bit of direct comparison experience. The monocrystalline panels do outperform the other types but the Cadmium Telluride Thin Films far out preform the others in diffuse light conditions. I have locally dense fog here at my location in the summer and that is the reason for my interest in them. The First Solar Thin Film panels are not flexible like most thin films, they are two sheets of 3.2 mm glass bonded together with the silicon vapor deposited on them. They are most commonly used in multi-gigawatt power plants and are not at all common in household use. I use the monocrystalline panels and the Cadmium Telluride panels connected to the same controller banks. The mono's are connected 4 in series for 69.6 volts at MPP and the CdTe panels are all in parallel at 69.8 volts at MPP for a close match at MPP. They are connected to Tracer (Beijing EP Solar Technology) 3215RN MPPT controllers rated at 400 watts /12 volts specifically designed for thin film panels operating at 68 volts. In bright sun I am using only the mono's 2 banks of 4 each (440 watts total) ,in foggy conditions the CdTe Panels are connected in parallel with the with the mono's on each controller. In heavy fog the 5 CdTe panels (375 watts) produce approx. 60% and the 8 mono's (440 watts ) produce approx. 40% of the total power produced from each of the shared controllers.
    Other panels are connect to Tracer 4210RN controllers 3 banks of 3 Siemens panels and 1 bank of two series connected Suntech Wuxi panels.
    CdTe panels are difficult to use, setup and information is difficult to find on them. Most large scale power plants are using them as they have a much better thermal coefficient of performance (they do not derate nearly as much as mono panels) and they are much cheaper to produce as there are fewer manufacturing steps. The melted silicon Is sprayed or vapor deposited on the glass. There is no growing of crystals , slicing wafers etc. they are currently being produced by General Electric, Siemens, Bosch, and Westinghouse as well as First Solar. None of these companies are selling them for residential use. Mine were scrounged from a forklift dropped pallet of panels at a major >50,000 panel installation in the San Francisco Bay Area. As they are all glass with no frames they are fragile.

    I would recommend these panels only for experimenters.

    The Tracer MPPT charge controllers that I am using are the only Chinese charge controllers that are worth looking at (in my opinion).
    At approx. $250.00 they are not cheap and are not junk. Their higher end line the eTracer ($400-600) is so close in design to the Morningstar MPPT line that it might be a clone of the Morningstar but at that price the Morningstar is a much better deal.

    Tecnodave
    2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #6
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    Re: thin film performance

    I have Sharp NAF "micro-morph" panels, they're dual junction a-SI with micro-crystaline. And another set of Yingli poli panels on the same roof. During cloudy weather, I hardly see any difference between the two: http://forum.solar-electric.com/showthread.php?20351-Thin-film-expansion/page2

    This just illustrates that it's dangerous to generalise about "thin film" panels, when there are so many differences between the technologies. CIS, CIGS and CdTe (like technodave's FirstSolar panels mentioned above) seem to do much better than aSi-uSi and plain aSi in low light. Single junction aSi seems to be quite bad in low light, with also the lowest efficiency - but some dual junction aSi-aSi panels on the other hand seem to do quite well in low light.
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