Development of fuelless powerplants?

The conspicuous lack of autonomous orbital bombardment systems primed to fire at anything producing electricity might also be a contributing factor to why Earth hasn't put any serious investment in this sort of thing.

Just saying.

cralkhi wrote:Yeah, but land area is not really important -- sunny desert land is cheap and common. What you need are not really efficient photovoltaics, but really cheap even if inefficient photovoltaics.

Solar constant is 1353 W/m^2. Cut half of that for nighttime, half for atmosphere/clouds, 10% efficiency... that's 33.8 W/m^2. So... 1000 square kilometers is 33.8 gigawatts (Hoover Dam is about 2 GW)... and that's a speck in the US Southwest.

Use 10% of Nevada alone, and that's about 1 Terawatt. If you could transfer the energy without losses, you could power the entire Earth from the unpopulated parts of the US Southwest (though if you paved THAT much with solar panels you would start to have ecological problems.)

I don't think land is the issue.

At assuming an average weight of solar panels being roughly 18kg/m^2, and 1,000,000 m^2 per km^2, and 1000 km^2 squared of area your array of solar panels is going to require 18*10^9 kg (18 billion) of material, or roughly two Invictus SD(P)s and change. That is only for the panels themselves, any mounting hardware* and electrical fittings are going to be extra**

*Some assembly required
**Batteries not Included

ksandgren wrote:One environmental problem generally ignored in the rush to alternative energy sources is that it is an environmental near disaster to produce those photovoltaics. Most of the original processes require, and contaminate with, some very dangerous chemicals to produce the photovoltaics in the first place. For all the semiconductor manufacturing done in silicon valley, the cost is a lot of contaminants burried like some of the WWII era dumps that are now super fund clean up sites. This is the left coast, and we have a lot of environmental concerns, but our need for energy results in a LOT of pollutants being produced for clean energy and materials. Solar photovoltaics may be relatively clean in operation, but they have been anything but to produce. I don't doubt that today's processes are much cleaner than the ones I grew up with, but it is hard to safely dispose of things like arsene gas.

This is the reason while, although I'm rather on the green side, I despise photovoltaic as a clean solution in all but very specific situations. But what we have been discussing for 4 pages is thermal solar and do not involve photovoltaic panels but simple mirrors and steam.
That is very clean technology.

Total eco-bilan of photovoltaics panels is usually negative value, especially the newer ones made in china which are cheaper but last a lot less longer.

1) Best efficiency achieved so far by a multijunction solar cell is 44,5%. That is quite a bit higher than the 15% of commercially available cells.

2) The efficiency of multijunction cells increases with the concentration of sunlight. The price of mirrors is much lower than that of multijunction cells. Ergo, have a small area of multijunction cells fed concentrated sunlight by a much larger area of mirrors.



That said, I'm still in favor of other renewable sources of energy such as solar thermal and geothermal, at least until photovoltaic cells are developed for a few decades more.

Or until we get reliable, positive-efficiency fusion power. There are some experiments towards that.

Belial666 wrote:(SNIP)

That said, I'm still in favor of other renewable sources of energy such as solar thermal and geothermal, at least until photovoltaic cells are developed for a few decades more.

Or until we get reliable, positive-efficiency fusion power. There are some experiments towards that.

Not to rain on anyones parade - but this topic is very impractical. (No offense!)

While the technologies mentioned are practical, they are not ready now.

I mean, why would anyone spend the years necessary to develop the technology (i.e. vacuum technology for the dewars, ceramic technology for the insulators, material technology for the development of the salts, etc), when steam energy is already developed, and is currently being rolled out?


As a possible source for 20+ years time - sure! But for the here and now, IMHO, steam is the way to go.....

Aegis99 wrote:At assuming an average weight of solar panels being roughly 18kg/m^2

That sounds rather high. That would be something like... assuming a density of 2000 kg/m^3 which is about right for silicon ... almost 1 cm thick, which seems excessive given that thin films exist -- newer, yes, but I think they'd turn out much cheaper (for that very reason -- materials) if you were really trying to cover a large area.

ksandgren wrote:
One environmental problem generally ignored in the rush to alternative energy sources is that it is an environmental near disaster to produce those photovoltaics. Most of the original processes require, and contaminate with, some very dangerous chemicals to produce the photovoltaics in the first place. For all the semiconductor manufacturing done in silicon valley, the cost is a lot of contaminants burried like some of the WWII era dumps that are now super fund clean up sites.

Yeah, I'm aware of that, but I don't think it really rises to the level of the sheer environmental disaster fossil fuels are. Those problems are pretty localized, while fossil fuels have the localized problems too (mountaintop removal for coal, various oil projects in formerly pretty pristine regions of Canada/Alaska etc. etc.), plus the atmospheric effects of fossil fuels which get everywhere and change a whole lot of things in often subtle ways (air pollution in cities with all its very nasty health effects -- which are I think underestimated by the general public since it more raises rates of people dying of respiratory issues, without a clear disaster to point at like Fukushima or Chernobyl, though coal etc. are actually much more dangerous overall; acid deposition; CO2 increase with all its climate effects, plus ocean acidification...)


But I think we've gotten well off Safehold at this point...

cralkhi wrote:

Aegis99 wrote:At assuming an average weight of solar panels being roughly 18kg/m^2

That sounds rather high. That would be something like... assuming a density of 2000 kg/m^3 which is about right for silicon ... almost 1 cm thick, which seems excessive given that thin films exist -- newer, yes, but I think they'd turn out much cheaper (for that very reason -- materials) if you were really trying to cover a large area.

Sure, but consider that a desert is also a very inhospitable environment with high winds, and by definition a high amount of heat. Those fancy thin film panels fail under those conditions. I think a 1cm thick panel is very reasonable for structural reasons and for durability. Which if you're covering an entire desert in something durability is going to be a prime design consideration.

That doesn't even consider replacement issues. Current technology panels lose about 1/3 of their electrical generating potential in 5-10 years, with complete impotency after 20 years. That means your desert of panels is going to have to be continuously replaced every twenty years.

As you pointed out though, this is not something safehold can/would use at this stage.

Aegis99 wrote:(SNIP)

Sure, but consider that a desert is also a very inhospitable environment with high winds, and by definition a high amount of heat. Those fancy thin film panels fail under those conditions. I think a 1cm thick panel is very reasonable for structural reasons and for durability. Which if you're covering an entire desert in something durability is going to be a prime design consideration.

That doesn't even consider replacement issues. Current technology panels lose about 1/3 of their electrical generating potential in 5-10 years, with complete impotency after 20 years. That means your desert of panels is going to have to be continuously replaced every twenty years.

As you pointed out though, this is not something safehold can/would use at this stage.

Just to raise a stupid question, but how is this energy used?

I mean, is there going to be a industrial settlement co-located with the solar power generator? If not, how is the energy to be transfered to the nearest settlement?

Aegis99 wrote:
Sure, but consider that a desert is also a very inhospitable environment with high winds, and by definition a high amount of heat. Those fancy thin film panels fail under those conditions. I think a 1cm thick panel is very reasonable for structural reasons and for durability. Which if you're covering an entire desert in something durability is going to be a prime design consideration.

That doesn't even consider replacement issues. Current technology panels lose about 1/3 of their electrical generating potential in 5-10 years, with complete impotency after 20 years. That means your desert of panels is going to have to be continuously replaced every twenty years.

As you pointed out though, this is not something safehold can/would use at this stage.

Not actually correct. Solar panel outputs in modern panels drop about 1% per year from the previous years output - so you should get about a half centuries service before you see a noticeable drop. (Washing the panels helps too, Mars is a little harder.)
http://www.nrel.gov/docs/fy12osti/51664.pdf