zlacker

for solar panels that are say 25% efficient, that means 75% of optical energy is turned into heat, whereas the sand had a relatively high albedo, its going to significantly heat up the local environment!

>>Doctor+(OP)
That is not what 25% efficiency means for solar panels.

>>jacque+11
care to expand on your comment? or are is this just remarking that some light was reflected?

>>Doctor+ja
No. It is enough for me to see such a single ridiculous statement of such magnitude to discount the rest of your voluminous contributions to this thread.

>>jacque+Qb
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.

>>Doctor+(OP)
http://english.scio.gov.cn/m/chinavoices/2025-10/23/content_...

In your opinion, how credible is this story?

>>Doctor+Ec
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.

>>jacque+7h
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.

>>SergeA+4d
I am unable to access this site, if you could mirror the page I will take a look.

EDIT: found it on the Internet Archive:

https://web.archive.org/web/20251208110913/http://english.sc...

I will come back and give you my opinions.

>>SergeA+4d
OK I read the story (it was shorten than expected).

So simplistically put there are 3 periods:

1) the grassy period before overgrazing, lot of wind

2) the overgrazed period, loss of moisture retained by plants and loss of root systems, lot of wind results in soil run-away erosion without sufficient root systems

3) the solar PV period: at higher heights still lots of wind, but the installation of the panels unexpectedly allowed the grass to regrow, because wind erosion is halted.

The PV panels actually increase the local heating, but that doesn't need to directly equate to temperature: the wind just carried away the heat so it's someone else's problem :). Also the return of soil moisture thanks to the plants means a return of a sensible heat buffer, so the high temperature in the overgrazed period before solar panel introduction may not actually be an average temperature increase, but an increase in peak temperature during the summer. Imagine problematic summer temperatures, everybody would be talking about the increased temperature, when they are really just experiencing the loss of a heat buffer.

At least thats my impression from the story.