Re: PV Panel War: Sanyo v. Hengji. The ultimate side-by-side long-term, real-world t
I find this whole thing very interesting, my wife who has a degree in Physics and a PhD in electrical engineering, specialising in semiconductors explained it to me, how the MPPT could never achieve as much as treating each panel at an individual level, basically the sum of the parts will always be greater than the sum of the total because each panel is optimised or the whole system is optimised, but whether this was significant or not, who knows, what is very significant is the Physics involved in the conversion of photons to electrical energy, and this is where clouds can have a big impact as the shadow moves across the panels, but again, it's not measurable in any meaningful way.
Personally detesting the look in my opinion is only excusing a lack of willingness to consider the options, in my case, 9 panels are hidden from the front, and 8 of these sit on top of flat roofs that don't have any aesthetics to lose
. But if aesthetics are important, surely the only option is solar tiles, which incidentally I did get a quote for, but it put the install, off the scale, for price.
I'd love to give meaningful figures but I've yet to find a way to record the Enecsys figures beyond the totals they show, for day, week, month etc. and this is looking at the data with sufficient detail. I have collected the odd snapshot throughout a single day to see what happens, but you'd really need to capture every reading for every panel throughout the day, to analyse it in any meaningful way. If a shadow from a cloud moves across the panel at the same speed, the effect on a micro-inverter system is for both panels to record the same total, if using a string, the effect is to lower the overall output for the duration of the shadow on either panel. But if you looked at the instantaneous readings, you'd see one panel was generating maybe 10 or 15W less for the duration of the cloud.
My best figures I can come up with, for 2 of the pairs that are in consistent conditions, and they're flawed for the reasons above:
Pair 1: Today: Same reading Week: Same reading Month: 18.37 vs 18.45 Year: 64.84 vs 65.17
Pair 2: Today: Same reading Week: 2.49 vs 2.48 Month: 19.14 vs 19.07 Year: 67.92 vs 69.88
Pair 2 is interesting as the panel that's achieving the most has swapped over.
Another interesting factor is temperature, and I suspect worrying about clouds and positioning is probably largely irrelevant compared to temperature, we know how much heat can affect the generation efficiency, so the middle panels in any array, could potentially be under-performing the outside panels due to heat build up. Now we're in the summer I'm seeing my flat roof mounted panels exceed the generation of the roof mounted panels by a much larger margin than any of the efficiency differences, which is probably mostly to do with heat. My roof mounted panels were always the best during the winter by 10-15% and this situation has reversed by roughly the same amount.
There are so many factors that could affect solar generation, I found it quite dismaying that micro-inverters were rejected out of hand by so many installers. I think the reality is as you say, the cost is more significant than any benefits, unless the system cannot function without.
I suspect my install is one of the most esoteric out there (and my reasons for maximising generation at whatever cost), and it would not be possible to design out any of the shading issues, simply because orientation of panels is largely fixed due to various factors. I would have loved a 3D model, but given the cost is nearly half that of fitting an extra panel, you'd wonder whether the suck it an see approach is just as valid as sitting there and trying to do the maths.
mike
