Scientists are working on space-based solar panels | Hacker News Reader

Scientists are working on space-based solar panels

businessinsider.com

6 pointsogezi11 comments

You can see why Elon Musk thinks the economics of space based solar is untenable. I think his argument is sound. http://www.youtube.com/watch?v=gVgM2BlMczY

tl;dw: I recall he mentions the losses due to multiple format conversions (light:electricity, electricity:laser, laser:electricity). But these losses get smaller as technology improves. And the 24X7 advantages pretty much make up for that. Ground-based solar has the disadvantage of 'night'.

Further, ground-based stations require land, damage ecosystems, are eroded by weather, are vulnerable to politics. Stations near cities (where the energy is needed) have political hurdles (eminent domain, right of way).

Orbital solar has its own problems. But it can be expanded at will, with no political problems.

Even assuming that you can get the conversion loss low enough that you're coming out ahead due to not having night or clouds, you're still only marginally producing more power. The cost is you have to launch all of that equipment into orbit. That doesn't even begin to justify marginal improvements. The whole thing is wildly optimistic and not grounded at all in economic realities. It would take space elevator type costs of space launch to even consider this. And if you have that, then you have cables to the ground and you can stop worrying about conversion.

That's a leap. Its 10X better solar flux out there in vacuum than on the ground. Gonna take a lot of losses to cancel that.

And its not a matter of total cost - its payback period. It keeps transmitting for decades after being built. We plant forests, reclaim ocean, terrace mountains - with an outlook of 20 to 100 years, and call it good business. Why not orbital solar?

I would say it's you who is making a leap here. http://physics.ucsd.edu/do-the-math/2012/03/space-based-sola...

Guy starts out with fakery to make ground-based work better. Transmitting thousands of miles on land is far worse proposition than he makes out - cable losses are great. Can't use anything as efficient as a laser, because air and dirt.

So this is basically how satellites already work, except the energy would be sent back to Earth through microwaves. What would be the room taken on Earth?

It says in the article: Rectenna arrays up to six miles in diameter.

Interestingly, the article also suggests that this could be useful for remote applications that would have difficulty getting supplied with diesel or other fuels:

    "An advantage for the military, as well as civilians, 
     would be that they could build receivers at remote 
     operating bases and locations where it is 
     logistically difficult and incredible costly to 
     deliver diesel fuel."

I find it hard to see how setting up a 6 mile diameter rectenna array is any easier than setting up a diesel supply route except in the most specific circumstances (e.g. mountain-bound plateau inaccessible by road intended for long-term station that can be supplied initially by a long chain of helicopters providing the array components).

Half of the trillion(s) spent in the Mideast wars, was spent on hauling diesel fuel. For air-conditioning tents. And it is never finished - have to keep hauling forever. For any protracted conflict, you only have to build an array once.

However a true disadvantage to arrays would be, a geostationary energy farm would transmit optimally to land directly under it - the air is thinnest. Steering the laser to remote places would lose efficiency as it traversed oblique slices of atmosphere at odd angles.

Likely you'd need relay sats to beam the energy as microwave then down to the best groundstation location. This isn't an optimal solution I think since it would require sats that could change their orbit to link up (even if you had them setup their initial orbits as a grid it still would require adjustments).

Maybe a ring of relay sats around the planet? With relatively infrequent changes in energy switching (as ground stations are built) a static setup could be formed. Then just modulate the beams (day/night demand flux).

For the original plan, there's no actual requirement to steer the beam. A station isn't so large that one city couldn't consume the whole capacity. So still a reason to build the thing.

Reply on news.ycombinator.com