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Comment by yetihehe | Hacker News Reader

Does anyone has an idea of what would be the effect of a large solar farm that converts 95% of light into usable energy? It would mean that this light doesn't fall on ground and doesn't heat surrounding air, so net cooling in one place and exporting that heat into the rest of earth (where it is used and expelled as heat)?

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As I understand it, solar panels have a maximum theoretical efficiency that's much lower than that. 33% for a conventional design with others apparently going a bit higher, but I don't think you can ever get anywhere close to 95%. There's also the question of transporting the electricity efficiently.

Still an interesting hypothetical question though. Maybe you could achieve the same effect more easily with mirrors.

95% conversion into electricity (or steam if you prefer) by a solar plant wouldn't have a cooling effect at all. It's just high grade energy that eventually becomes low grade energy (thermal energy) heating the atmosphere of the earth.

if you actually want to prevent light from becoming thermal energy on earth it'd be far easier to build a dyson swarm to obstruct the sun.

Not necessarily if you get rid of the energy in another way, right? You could perform hydrolysis to turn water into hydrogen + oxygen, and if you release hydrogen into the atmosphere it will just escape our atmosphere into space.

Theoretically, but most hydrogen generated would be burnt to generate back heat. Doesn't make much sense to use hydrolysis to capture Oxygen.

The only practical way to do such a thing would be with a giant mirror. There is no reason why earth cannot radiate energy back into space. A mirror is a good way to do that for the optical wavelengths. Most of the energy received by earth each day is in the optical spectrum and secondarily from the gravitational interaction of the earth-moon system. The moon we can't really do much about. But sunlight absolutely can be reflected.

A mirror would also be much more effective if part of some ring like structure orbiting the earth, as most of the energy would never enter encounter earth's atmosphere in the first place.

You just need an umbrella at the Lagrange point.

Maybe there already is, but it’s just not observable…

Isn't that what your parent comment said?

> exporting that heat into the rest of earth (where it is used and expelled as heat)

If you covered the Earth in solar panels and used it solely to charge a battery, the Earth wouldn’t freeze. Energy is not the same as useful energy.

Not even at 95% efficiency? I think it was a hypothetical, not a current consideration.

But it would tho? Imagine if your battery was the earth's core. So basically you're pumping majority of the incoming energy inside the earth. Less heat is reflected to to warm the athmosphere, hence a cooling effect.

Once you release the stored energy it's a different story.

On net I don’t think it makes a difference. When the energy is spent as electricity it basically releases heat in some form or other eventually

However you might be able to kick the can down the road for another century or even millennium if you release the heat deep inside the earth.

You could even achieve a similar effect with today's tech by running solar-powered heat pumps that pump the heat into deep bore holes or old oil wells.

But that air conditioning the desert is a particularly great idea, but compared to better ideas like putting translucent reflective foil into orbit it had the charm that it has local effects you can achieve without international cooperation or incident

Radiation to space would be another possibility. But reflective paint would seem easier than a scheme to power arrays of space facing lasers using ultra high efficiency solar panels.

Thinking of becoming a kardashev 1 civilisation, are we?

Theoretically yeah. The question is how efficient they are at doing this.

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