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LG300N1T-G4 -- T for Transparent?

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  • #31
    Originally posted by jflorey2 View Post
    There's an 80kW array down here that uses bifacial panels. It's a sun deck over white concrete at a restaurant. The transparent backsheet allows a decent amount of light through.

    More and more often down here in San Diego I am seeing freestanding structures (parking lot arrays, carports, sunshades, lampposts) that could benefit from such panels, both from the light they allow through and from the additional power from the reflected light.

    That may be. I see some of the same in 92026. What most folks seem to not understand is that if the front side (top) of a panel or of an array is (hopefully) oriented so as to have the most favorable conditions available for operation, to a 1st approx., logic and common sense might lead one to surmise that a surface oriented in the precisely opposite direction, that is, the back side of a panel or array might just have close to the worst orientation, or at least not very good. But never mind that for now. That's just my dumb country upbringing floating to the surface like the big chunks in a cess pit.

    On the 80 kW sundeck: I'd guess the panels and the array are somewhat horizontal ? Or if tilted, probably something like @ 20 deg. or so ? Without going into particulars about things like diffuse surface reflection and directionality, along with forward vs. backward scattering, view factors, and a bunch of other stuff, I'll take a SWAG that the incident radiation on the underside of those panels if they are, at, say, 20 - 30 ft. off the ground, is probably not much more than 5% or so of the front side irradiance.

    By way of some explanation: A thought experiment: For hours of collection, say between 0900 and 1500 hrs. solar time, a good portion of the ground (the white concrete) surface that the underside of that array will "see" with more than a very small view factor will be the ground under the array, and thus (unfortunately) be shaded - and so not much to reflect there - only diffuse reflected, some of which was itself reflected before it got to the only reflecting surface with a decent view factor. The view factors for the rest of the surroundings - for walls, other nearby surrounding buildings (and probably not as white and therefore not as reflective) etc., will be quite small, the smallness of the view factors mostly due to the high angles of incidence of the other surfaces relative to the undersurface of the array. For the white concrete under the array, if it is shaded by the array, as it must be (for most of the time and mostly during peak sun hours), that means the only solar radiation incident on the concrete under most of the array will be diffuse, with the additional penalty (to reiterate) that most or all such diffuse radiation will be comprised mostly of backscattered diffuse radiation and diffuse radiation incident as a result of already having been reflected from other probably diffuse surfaces, perhaps multiple times, weakening and scattering more with each "re"-reflection.

    Additionally, since it's highly likely that most or all of the small amount of solar radiation reaching the underside of the array will be diffuse, an additional penalty will be in place. Reason: transmittance of diffuse radiation through glazing is less than for beam radiation. This is due to the higher effective (averaged) angles of incidence of the scattered, diffused light, and how, because higher angles of incidence have greater surface reflectance, less radiation is present tor transmittance.The common approximation is to take the reflectance of diffuse radiation as being appox. the same as that of beam radiation at a 60 deg. incidence angle. For most transparent materials used in solar energy applications that translates into an approx. 10% additional penalty in collected energy. That's due to increased reflection of diffurse solar radiation only.

    There is also a small additional penalty to be paid due to increased panel temp. This is small, but ought to be at least considered. Say the backside enhancement does amount to a 5 % increase in incident radiation. Since, at least to a pretty good 1st approx., and from energy (heat) balance considerations, that will increase the cell temperatures by something like ~ 5% over the not bifacial temp. diff between the array and the surroundings. That will mean something like a 1 C. or so increase in panel temp., resulting in another 0.5% or so decrease in energy collected due to temp. induced efficiency decrease. That needs to be taken as a reduction to my (assumed) 5 % enhancement from back face irradiation..

    Now, If the design came in at the same price with or without bifacial panels, and assuming (somewhat generously I'd respectfully submit), O. & M. and other costs are the same, I'd say consider going for the bifacial option for this non residential option. However, given the dearth of knowledge surrounding how to estimate the potential enhancement to incident radiation on the backside of panels from reflection, I'd not go for it if it cost much more than the non bifacial option without some serious work.

    I'd respectfully suggest to those who think large increases in incident radiation, and thus annual output are possible from the use of bifacial panels, to understand the possibilities and constraints that are part of the reality of the situation. Large (say~ > 10 % ) increases in actual yearly output without some compromises in aesthetics or some added costs in ancillary equipment or additional design requirements are probably hard to come by, and rarely cost effective in residential situations.

    Comment


    • #32
      Originally posted by DanKegel View Post

      The pricing I saw from one uk site:

      204 lg300
      221 lg300 black
      228 lg300 bifacial
      245 lg315
      250 lg320

      So, halfway between price for 300 and 320.

      That seems pretty reasonable.
      So the difference is ~US$10, only 3% additional cost? I would have thought much more. With the right application (see my post #30 re West facing tilt mount) possibly achieving just 15% additional output, this is easily justified. Just 3% extra production is break-even.

      Comment


      • #33
        Originally posted by J.P.M. View Post
        A thought experiment: For hours of collection, say between 0900 and 1500 hrs. solar time, a good portion of the ground (the white concrete) surface that the underside of that array will "see" with more than a very small view factor will be the ground under the array, and thus (unfortunately) be shaded...
        Right, self-shading is a problem. Prism and LG both suggest using them on flat white surfaces, in tilt mounts,
        and say that back-side output is roughly proprotional to the height above the surface.

        The City of Santa Monica has relaxed rules for solar panels that don't extend more than five feet over the roof,
        which leaves only half a meter for the gap under the panels... LG says you can expect about a 15% boost in
        that case.

        I don't know yet whether non-penetrating flat roof mounts like PermaCity's can deal with that, I think they are
        engineered with a very low gap, which wouldn't be a good match. Still looking around.

        Comment


        • #34
          If the price isn't far off standard panel, then I guess there's market for it. The way I look at this double side panel if you install them on flat roof with tilt mounts or on the snow to get the money worth.

          The spec on paper definitely look good, but did anyone compare the actual output with regular panel on roof mount? more failure points?

          If they can make the solar panel transparent allow lights to passing through crystal (still remain the efficiency), then I guess you got a GO

          Comment


          • #35
            Originally posted by J.P.M. View Post
            On the 80 kW sundeck: I'd guess the panels and the array are somewhat horizontal ? Or if tilted, probably something like @ 20 deg. or so ? Without going into particulars about things like diffuse surface reflection and directionality, along with forward vs. backward scattering, view factors, and a bunch of other stuff, I'll take a SWAG that the incident radiation on the underside of those panels if they are, at, say, 20 - 30 ft. off the ground, is probably not much more than 5% or so of the front side irradiance.
            Probably correct. I'd guess 5% during most of the day from reflection, and 10% when the sun angle is low and illuminating a larger portion of the deck.
            There is also a small additional penalty to be paid due to increased panel temp. This is small, but ought to be at least considered. Say the backside enhancement does amount to a 5 % increase in incident radiation. Since, at least to a pretty good 1st approx., and from energy (heat) balance considerations, that will increase the cell temperatures by something like ~ 5% over the not bifacial temp. diff between the array and the surroundings. That will mean something like a 1 C. or so increase in panel temp., resulting in another 0.5% or so decrease in energy collected due to temp. induced efficiency decrease. That needs to be taken as a reduction to my (assumed) 5 % enhancement from back face irradiation..
            The additional cooling from being ten feet from the nearest surface (compared to 6-18 inches in a typical roof installation) will far outweigh the additional heat load from the reflection.
            Now, If the design came in at the same price with or without bifacial panels, and assuming (somewhat generously I'd respectfully submit), O. & M. and other costs are the same, I'd say consider going for the bifacial option for this non residential option. However, given the dearth of knowledge surrounding how to estimate the potential enhancement to incident radiation on the backside of panels from reflection, I'd not go for it if it cost much more than the non bifacial option without some serious work.
            Right. These aren't, in general, for standard roof installations; they are for alternative installations that are farther away from the surface they are mounted to. Since they are nearly identical in price to standard panels, the additional functionality doesn't come with much of a penalty.

            Comment


            • #36
              One more vendor with bifacial: http://www.yinglisolar.com/as/produc...ine/panda-210/
              These are glass-glass, frameless. No price in US yet (and yingli has financial problems, I hear, so who knows if they will make it here).


              Comment


              • ncs55
                ncs55 commented
                Editing a comment
                Yingli are crummy modules, that's why they are going belly up. I have replaced too many due to failures already, and there are more failing every day. Just remember 1 thing, In the solar industry, you get what you pay for. You go cheap, your system will fail prematurely in some way. I see it every day right here in So Cal.

            • #37
              Homeowners just looking for panels, please ignore this post.
              Those not interested in bifacial panels, please ignore this post.

              For anyone interested in an update on bifacial panels, see bifipv-workshop.com; they just held their third annual workshop, and all the slides from the talks are online.
              At least one talk emphasized that the intended application is for large arrays or architectural applications which are particularly able to deliver back side illumination.
              One emphasized they have not yet proven their worth in the field beyond a shadow of a doubt (and then presented a way to gather evidence quickly).
              Several discussed progress towards a standard way of measuring bifacial panel output (taking into account things like junction box shading).
              And a couple discussed real-world performance of bifacial arrays.
              Meyer-Burger, a mainstream solar cell production equipment vendors, had two presentations... so it's not just individual solar companies going it alone.
              Interesting reading, if you're watching this not-yet-widespread niche technology.

              Sorry for the pun buried in the middle there

              Comment


              • #38
                Originally posted by DanKegel View Post
                Homeowners just looking for panels, please ignore this post.
                Those not interested in bifacial panels, please ignore this post.

                For anyone interested in an update on bifacial panels, see bifipv-workshop.com; they just held their third annual workshop, and all the slides from the talks are online.
                At least one talk emphasized that the intended application is for large arrays or architectural applications which are particularly able to deliver back side illumination.
                One emphasized they have not yet proven their worth in the field beyond a shadow of a doubt (and then presented a way to gather evidence quickly).
                Several discussed progress towards a standard way of measuring bifacial panel output (taking into account things like junction box shading).
                And a couple discussed real-world performance of bifacial arrays.
                Meyer-Burger, a mainstream solar cell production equipment vendors, had two presentations... so it's not just individual solar companies going it alone.
                Interesting reading, if you're watching this not-yet-widespread niche technology.

                Sorry for the pun buried in the middle there
                Thanks for the update Dan. Let us know if any information you get out of that workshop would help you evaluate your bifacial panel installation.

                Comment


                • #39
                  Originally posted by DanKegel View Post
                  Homeowners just looking for panels, please ignore this post.
                  Those not interested in bifacial panels, please ignore this post.

                  For anyone interested in an update on bifacial panels, see bifipv-workshop.com; they just held their third annual workshop, and all the slides from the talks are online.
                  At least one talk emphasized that the intended application is for large arrays or architectural applications which are particularly able to deliver back side illumination.
                  One emphasized they have not yet proven their worth in the field beyond a shadow of a doubt (and then presented a way to gather evidence quickly).
                  Several discussed progress towards a standard way of measuring bifacial panel output (taking into account things like junction box shading).
                  And a couple discussed real-world performance of bifacial arrays.
                  Meyer-Burger, a mainstream solar cell production equipment vendors, had two presentations... so it's not just individual solar companies going it alone.
                  Interesting reading, if you're watching this not-yet-widespread niche technology.

                  Sorry for the pun buried in the middle there
                  I stopped going to solar energy conferences and workshops when I figured out they were worse than the usual peddler's excrement one finds at industry trade shows in terms of the mostly shameless hype and hawking of wares, and the B.S. that's often presented as results of alleged valid research. Or, some of what amounts to white collar welfare for those hiding out in academia. With the possible exception of the NREL presentation, most of this stuff looks like one or the other of those things, and all of it looks like power point surface scarfing of the issues with little backup for claims made.

                  I'd note too that there still does not seem to be any consistency or focused discussion, much less agreement on something as simple and fundamental as measurement and angular distribution of backside irradiance, or discussion of possible ways and possible agreement on how to standardize on it.

                  Still, and if only to play the devil's advocate to Dan's pie in the sky tendency to shout about what fits his often stated ignorance about things dealing with alternate and renewable energy, ongoing discussion and presentation of what may be the current thinking in any particular application is probably good. Or, at least do little harm, provided it doesn't mislead folks into thinking bifacial PV is mainstream, cost effective and roof -ready for Joe and Jane 6-pack. Or another reason: It may as a way to see which way the possible misinformation may be heading.

                  I'm always interested in information, so, I read Dan's post.

                  Having done so, my B.S. meter tells me to follow the money. I believe Dan's reference doesn't have much that's new. If it has any additional useful purpose, it may be that it seems to agree, in general, with the idea that bifacial panels are mostly useless for most common residential applications - read: Don't pay more without a lot more information that's probably not yet available.

                  Otherwise, and even though I'm interested and FWIW, probably know a lot more than Dan about bifacial panels, as well as where, why and when they may, or may not, hold advantages, Dan's most recent post to this thread, at least IMO, seems more of the same of Dan's usual M.O. of repeating stuff that fits his version of reality but deals in matters, by his own admission, he knows little about.
                  Last edited by J.P.M.; 01-18-2017, 01:13 PM.

                  Comment


                  • #40
                    How does a Transparent panel harvest power ? (hint, if it's transparent, it's not sucking up any light)

                    I give this a FAIL.
                    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                    solar: http://tinyurl.com/LMR-Solar
                    gen: http://tinyurl.com/LMR-Lister

                    Comment


                    • #41
                      Originally posted by SunEagle View Post
                      Thanks for the update Dan. Let us know if any information you get out of that workshop would help you evaluate your bifacial panel installation.
                      Main thing I have to do is free up some time to work on it again; I realized a while ago that trying to shade one side of the panel with black cloth raised the temperature quite a bit, enough that I'm not comfortable trying to compensate for the effect on the output of the unshaded panel. So it's back to the simple idea of spreading out a high-albedo sheet (say, Tyvek) on the roof; I bet that make the results valid without temperature compensation.

                      As for the workshop -- it's just nice to see progress from multiple vendors towards a better quantified product.

                      Mike, the transparent parts don't harvest any power.

                      Comment

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