MemberOctober 8, 2021 at 8:05 am
(side note/question – I used to be able to edit a comment but the editing function doesn’t seem to exist anymore. Any ideas? In the comment I made October 7, 9:00 PM (just above), I meant to say “…there’s NO such thing as a “granular”, compound curve cell….” and would like to correct it.)
With respect to peak cell temperatures, I’ve looked through the data I collected during the last 2 events held at “Circuit of the Americas” in Austin, Texas and found a series of current vs voltage (a.k.a. IV) curves taken between 2:17 PM and 2:34 PM local time on July 7, 2017 for a solar car team’s array. Peak temperatures of the array were between 68 and 76 C. Nominal co-planer insolation was between 990 and 1006 W/m^2 at the time. I don’t know with 100% certainty but I suspect the testing was done with the car in the “cold pit” (between garages and “hot pit”) of the track. I wish I had wind data too but, alas, I don’t. I suspect, however, it was quite still in the area because of the garages to the rear of us and the track grand stands to the front.
If interested, the team’s array was composed of full size SunPower cells encapsulated such that the finished “laminates” had an “areal weight” of about 800 grams/m^2 (it’s my “Legacy” encapsulation scheme). These laminates were bonded to the team’s upper shell. The upper shell, as I recall, was a fiber reinforced resin skinned honeycomb core sandwich structure w/o foam filler.
With respect to why the cells are the right choice, it boils down to, essentially 3 characteristics. First, raw efficiency. SunPower/Maxeon still have the best efficiencies. Second, of all the conventional single junction Silicon cells, they have one of the lowest (if not the lowest) peak power temperature coefficient. Third, at least in the more recent generations, they have a lower “breakdown” voltage. Having a lower breakdown voltage helps mitigate mis-match losses. Mis-match is all but guaranteed on curved arrays.