How to harvest solar power? Beam it down from space!

[Chipstone306]

http://www.cnn.com/2008/TECH/science/05/30/space.solar/index.html

 

[Enjo]

Great news, thanks

"Skyrocketing oil prices, a heightened awareness of climate change and worries about natural resource depletion have recently prompted a renewed interest in beaming extraterrestrial energy back to Earth, Miller explained."

and this is a conclusion that I've been waiting for, for a long time.

 

[Belisarius]

Isn't it really dangerous to have TeraWatts of microwave radiation being beamed down from orbit? What happens if the beam goes off-target? What happens if an aircraft strays into the beam? Do we really want to fry flocks of migrating birds?

 

[thomasantony]

Isn't it really dangerous to have TeraWatts of microwave radiation being beamed down from orbit? What happens if the beam goes off-target? What happens if an aircraft strays into the beam? Do we really want to fry flocks of migrating birds?

That is not that much of a concern.
Copying from the almighty wiki here:
http://en.wikipedia.org/wiki/Solar_power_satellite#Safety


At the earth's surface, a suggested microwave beam would have a maximum intensity, at its center, of 23 mW/cm2 (less than 1/4 the solar irradiation constant), and an intensity of less than 1 mW/cm2 outside of the rectenna fenceline.

Now .. like any other problem, we only need some good investors .. Man, if I had that kind of billions lying around, the world would already have had a launch loop and an SPS system :dry: .. Oh well .. I guess one can dream .

~
Thomas

 

[Scrooge McDuck]

Right, this idea is about 40 years old, and studies have proven that it's not economically affordable, way too expensive. I also wonder about the efficiency of the beam, how many energy will be left at a receiving station, after the transmission?

Also,

A single kilometer-wide band of geosynchronous Earth orbit experiences enough solar flux in one year to nearly equal the amount of energy contained within all known recoverable conventional oil reserves on Earth today

It seems the article mixes up some things here, the amount the 1 km wide band receives, and the amount of energy that can be extracted from it, with current technology. I think that is a lot less.
Also, they say 'known' oil reserves, probably lot's and lot's of oil is yet to be found in future.


On another note, I always have a rather bad feeling when people talk about developing nations and this so called 'clean' energy. Why them? Even we, modern countries, don't use (currently) way too expensive solar panels for our main source of electricity supply, so why do people 'force', of all countries, developing nations do so, sigh... With a fraction of the money we could probably build them some decent power plants instead. Anyhow, this is a bit off topic in this subject, as this application is not neccecarily intended for developing nations.

regards,
mcduck

 

[eveningsky339]

It's definitely worth a try. Anything that could help reduce the world's reliance on fossil fuels sounds like a good idea to me.

I always carry an extra billion or so in my pocket for an occasion such as this.

 

[JEL]

Maybe this article is more interesting when talking about realistic (ie using current technology) solar-power harnessing:

http://www.geotimes.org/apr08/article.html?id=feature_solar.html

It is from april 2008, so quite fresh

It's not space-related though, so maybe not quite as relevant for this forum, but I believe its still on-topic in this thread on solar-power.

It talks about various ways of converting solar-energy into heat, and then utilizing that for further energy-conversion (into electrical in particular)

Problems mentioned:
-Storing the harvested energy during periods of no usable sunlight.
-Getting as much usable sunlight as possible into the energy-process.
-Whether larger power-plants or smaller per-house solutions are the most viable.

 

[rage]

other option drop a big !@# power cable down from orbit hmm is that possible damn the voltage drop on it would be huge

 

[thomasantony]

other option drop a big !@# power cable down from orbit hmm is that possible damn the voltage drop on it would be huge

Or maybe they can use some superconducting cables made from traditional or the high Tc ceramic type. Would require a lot of tubing for the liquid N2 .

~
Thomas

 

[rage]

superconductor is a good option but you would need as much n2 as you would think cos it is cold up there only when you start getting down low like under 10000 ft

 

[thomasantony]

superconductor is a good option but you would need as much n2 as you would think cos it is cold up there only when you start getting down low like under 10000 ft

Well you will have to cover it with gold foil and fill it with N2 as a contingency . But then there is still the problem that affects space elevators, collisions with sats.

~
Thomas

 

[n0mad23]

Scrooge is correct, this is a recycled old idea. Back in the 1970's, microwaving electricity back to Earth was the basis and justification of the book, High Frontiers. Honestly, the book seems a bit silly in 2008.

I've wondered since just how feasible this really is. I know it's pretty unpopular currently to see a connection between the demise of the bee and cell phones, but it does raise questions about the unpredicted effects of the technology. Certainly studies behind this technology are very different depending on if they were authored in Europe or in the US. I smell venal sensibilities here.

It also seems a bit silly to think that orbital technology's going to save the day when we haven't figured out a way to use sustainable energy here on terra firma. The choices for orbital electricity still are limited to solar panel technology, and to solar furnace generators. Solar panels just haven't got good enough yet to be worthwhile, and the alternative requires a lot of mass - just how much does it cost to put a kilo into orbit today?

Still, it's good to see that the ideas are still being discussed.

 

[Scrooge McDuck]

just how much does it cost to put a kilo into orbit today?

Well according to the Wiki link Thomas provided, the total cost of one orbital solar power station be $320 billion (I think it's fair to take worst case + some extra billions that I don't even mention), including all the required heavy lift launch vehicles.
The article also says that over it's whole lifetime, it will generate $154 billion by selling the energy, so you would still lose $166 billion at least...


To quote an interesting part of the article:

Without doubt, the most obvious problem for the SPS concept is the current cost of space launches. Current rates on the Space Shuttle run between $3,000 and $5,000 per pound ($6,600/kg and $11,000/kg) to low Earth orbit, depending on whose numbers are used. Calculations show that launch costs of less than about $180-225 per pound ($400-500/kg) to LEO (Low Earth orbit) seem to be necessary.

 

[n0mad23]

Well then, it's certainly making Tblaxland's and my project look more and more attractive.

I'd really like to see more exploration (even in terms of thought experiments) of some other ways of making off-world ventures more cost effective. I really think that the Moon's availability of He3 is what the goal should be in terms of alternative energy solutions. At least if we're looking for the solutions coming from other than local renewable resources.

 

[thomasantony]

Well then, it's certainly making Tblaxland's and my project look more and more attractive.

I'd really like to see more exploration (even in terms of thought experiments) of some other ways of making off-world ventures more cost effective. I really think that the Moon's availability of He3 is what the goal should be in terms of alternative energy solutions. At least if we're looking for the solutions coming from other than local renewable resources.

Well, an He-3 based energy source if even more remote in feasibility as of now than SPS. :thumbsdown: Why? Well for one, even though He-3 can be said to be "abundant", its concentration is only around 0.01 parts-per-milion. You get 10 grams of He-3 from processing 1 million kg of moon regolith, that too .. assuming 100% efficiency. :facts: And we have not yet made a net-power producing fusion reactor , so much for a production level He-3 reactor using tonnes of He-3 per year.

I think SPS is very feasible, provided we have some cheap launch system, like an Orbital launch loop.

~
Thomas