zlacker

>>g-mork+(OP)
> it is possible to put 500 to 1000 TW/year of AI satellites into deep space, meaningfully ascend the Kardashev scale and harness a non-trivial percentage of the Sun’s power

We currently make around 1 TW of photovoltaic cells per year, globally. The proposal here is to launch that much to space every 9 hours, complete with attached computers, continuously, from the moon.

edit: Also, this would capture a very trivial percentage of the Sun's power. A few trillionths per year.

>>gok+h4
We also shouldn't overlook the fact that the proposal entirely glosses over the implication of the alternative benefits we might realize if humanity achieved the incredible engineering and technical capacity necessary to make this version of space AI happen.

Think about it. Elon conjures up a vision of the future where we've managed to increase our solar cell manufacturing capacity by two whole orders of magnitude and have the space launch capability for all of it along with tons and tons of other stuff and the best he comes up with is...GPUs in orbit?

This is essentially the superhero gadget technology problem, where comic books and movies gloss over the the civilization changing implications of some technology the hero invents to punch bad guys harder. Don't get me wrong, the idea of orbiting data centers is kind of cool if we can pull it off. But being able to pull if off implies an ability to do a lot more interesting things. The problem is that this is both wildly overambitious and somehow incredibly myopic at the same time.

>>rainsf+RA
So what are the other things? You said he glossed over them and didn't mention a single one.

>>byeart+1G
If we (as in "civilization") were able to produce that many solar panels, we should cover all the deserts with them. It will also shift the local climate balance towards a more habitable ecosystem, enabling first vegetation and then slowly growing the rest of the food chain.

>>SergeA+Xi1
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+QC1
That is not what 25% efficiency means for solar panels.

>>jacque+RD1
care to expand on your comment? or are is this just remarking that some light was reflected?

>>Doctor+9N1
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+GO1
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+uP1
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+XT1
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.