Comment by DoctorOetker
4 hours ago
I'm dumbfounded, most light incident on a solar panel is not reflected, so logically photons were absorbed, some generated useful electron hole pairs pushing current around the load loop, others recombined and produced heat.
Its an entirely reasonable position in solar panel discussions to say that a 20% solar panel will heat as if 80% of the optical energy incident on the panel was turned into heat. Conservation of energy dictates that the input energy must equal the sum of the output work (useful energy) and output heat.
Not sure what you are driving at here, and just calling a statement ridiculous does not explain your position.
You have not done any real world verification on any of this, you are arguing from a very flawed and overly simplistic lay-persons theoretical model of how solar panels must function in space and then you draw all kinds of conclusions from that model, none of which have been born out by experiment. 25% efficiency for a solar panel means that 25% of the sunlight incident on a panel was turned into electricity. It has nothing to do with how big a fraction is turned into heat, though obviously the more of it is turned into electricity the less there is available to be converted into heat. And it does not account for other parts of the spectrum that are outside of the range that the panel can capture.
That 25% is peak efficiency. It does not take into account:
(1) the temperature of the panel (higher temp->lower efficiency), hence the need for passive cooling of the panels in space due to a lack of working fluid (air).
(2) the angle of the incidence: both angles have to be 'perfect' for that 25% to happen, which in practice puts all kinds of constraints on orientation, especially when coupled with requirements placed on the rest of the satellite.
(3) the effects of aging (which can be considerable, especially in space), for instance, due to solar wind particles, thermal cycling and so on
(4) the effect of defects in the panels causing local failure that can cascade across strings of cells and even strings of panels
(5) the effects of the backing and the glass
(6) in space: the damage over time due to mechanical effects of micro meteorite impact on cells and cover; these can affect the panels both mechanically and electrically
To minimize all of these effects (which affect both operational life span of panels as well as momentary yield) and effectively to pretend they do not exist is proof that you are clueless, and yet you make these (loud) proclamations. Gell-Mann had something to say about this, so now your other contributions suffer from de-rating.
1) yes solar panels should be cooled, but this is feasible with thermal radiation (yes it takes surface area)
2) pointing the panels straight at the sun for a sun-synchronous orbit is not exactly unobtainium technology
3) through 6) agreed, these issues need to be taken into account but I don't see how that meaningfully invalidates my claim that a solar panel operated at 25% efficiency turns ballpark ~75% of incident photons into heat. Thats basic thermodynamics.