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[GavJ]

This is my primary concern. Not cities in general mind, but Manhattan in particular: We've so thoroughly canibalized every livable inch in a quest for space, we went and built on the sky; and if you look to nearby areas, the problem only gets worse with the massive urban sprawl.

1) There's enough natural sunlight falling on manhattan to feed half a million people, 1/3 its population. Immediately surrounding boroughs go up to higher ratios until not too far away you could start getting surpluses. They all have roofs
2) More importantly, hydroponics. http://en.wikipedia.org/wiki/Hydroponics

[10ebbor10]

if the image in the opening post is right, any country that isn't absolutely packed with people isn't going to have significant trouble finding enough land to supply their need with solar power.
Transportation, storing, price might be problems, but raw quantity of land shouldn't be.

It probably isn't. The trick is to use potential, ie, eliminate any grid inefficiencies, assume 100% efficient pannels, and all that.

Even then, space should not be a problem

[Urist Mc Dwarf]

Also, people waste sooooo much electricity, food, etc. that it's riduclous. If people weren't so wasteful, I bet we might not even need this discussion.

However, on a renewable power note, some time ago, Popular Science had an article about noise from electricity.

[GavJ]

Also, people waste sooooo much electricity, food, etc. that it's riduclous. If people weren't so wasteful, I bet we might not even need this discussion.

Reduce, re-use, recycle   is intended to be done in that order.

[mainiac]

I think that if people didn't flip out whenever nuclear anything is mentioned, the world would be a lot better off.
Really, fission would be fandabi-fucking-dozi, but everyone just remembers disasters and, "but muh radiation!!!" rather than the vast majority of nuclear power plants that are entirely uneventful.

I think we'd be better off if nuclear advocates realized that it's cost, not safety that keeps nuclear from getting built.  Nuclear is more expensive then solar and solar's price is rapidly declining.  Nuclear hasn't been built in a while because it hasn't made sense in a while.  It's stayed around as a meme for thirty years because it lets someone claim to be non-ideological in the middle.

Personally I wanna see there:
http://www.extremetech.com/extreme/181389-japans-25-year-plan-to-put-a-gigawatt-solar-power-farm-in-space

Make 3000 stations like these and you've solved all the earths electricity needs with plenty of room to spare.  Plus you've jump started human space colonization efforts.

[GavJ]

Nuclear is more expensive then solar and solar's price is rapidly declining.

No, solar is twice or more as expensive as advanced nuclear (modern, breeders and such)
http://en.wikipedia.org/wiki/Cost_of_electricity_by_source

Also cheaper than clean coal.

More expensive (barely) than wind or hydro or geothermal, but far more flexible in location. If you live in Oregon, great, put in some hydro. But nuclear should be the basic fallback in any location where one of those three isn't immediately obvious as being especially well-suited, if you want efficiency. It also takes up way less space than any of those, except potentially geothermal (a very conditional energy source, but awesome)



Edit: I don't think that chart covers energy storage costs. If I'm correct in that, then go ahead and mark up the solar numbers to be about double again what they are listed as. Similarly for wind and hydro, needing to either have batteries or be built well beyond normal capacity.

[10ebbor10]

Besides, very significant cost reductions can be achieved if you can mass produce nuclear. Also, near zero grid cost.

On a side note, Space based solar is just a fantasy until we can get launch costs as low as $100–$200 per kilogram to LEO. For comparison, SpaceX's is aiming for 1100$/kg, with reusable tech perhaps 500.

[mainiac]

Nuclear is more expensive then solar and solar's price is rapidly declining.

No, solar is twice or more as expensive as advanced nuclear (modern, breeders and such)
http://en.wikipedia.org/wiki/Cost_of_electricity_by_source

I suppose it's just a coincidence then nuclear power is always 5 years in the future.

There is a host of problems with the metrics in the study you are referencing.  Nuclear generation is over a 30 year lifespan. 15 years from now nuclear which has improved very little will be competing with solar that has gotten a lot cheaper.  Nuclear generation is assumed to always be at 90% of capacity.  That's baseload power, the stuff we have in excess.  Yes in some markets that would offset some natural gas generation but it's just not as valuable.  Solar power is much more tilted towards peak generation.

And of course there is the problem that nuclear plants talk big talk but get cancelled and delayed and run into overruns.  Even assuming that these overruns all just vanish in the future you are still looking at a more expensive way to displace generation on the existing power grid.  If you realize that these estimates are probably about half what the final price tag will be after annualizing costs, it's a horrible, horrible idea.

[10ebbor10]

I thought the idea was to reduce emissions and pollution by displacing fossil generation.

And for that, Nuclear is excellent as it's both cheap (on a 60 year basis) , and can replace the most polluting source of all, coal.

[GavJ]

Same page has estimates for grid costs, placing solar at approx. 15-20x higher than nuclear.  Although they mention that chart as being more controversial, I don't think controversy explains away a 20-fold difference.

Yes in some markets that would offset some natural gas generation but it's just not as valuable.

Gas is cheaper and compact, yes, but the thread is "alternative energy sources" and we are discussing mostly long term options.
There's billions of years of wind and rain and sun, and probably billions of years of uranium.  Versus what, 100 or something of natural gas?
It's certainly a valid consideration sometimes, but not really what we are talking about here.

Also, personally, I'm much more concerned about greenhouse gases as an unknown externality that might cost way more than any of these estimates predict, potentially, than anything else. Natural gas is still a hydrocarbon and still spews forth CO2.

And of course there is the problem that nuclear plants talk big talk but get cancelled and delayed and run into overruns.

Political cancellation is not an actual argument against a power source 
And annual costs/maintenance are ALREADY taken into account in the previous link I provided.

[mainiac]

Same page has estimates for grid costs, placing solar at approx. 15-20x higher than nuclear.

I did not see that.  How on earth would you get those figures?

Gas is cheaper and compact, yes, but the thread is "alternative energy sources" and we are discussing mostly long term options.

The short term is the route to the long term.  The US isn't going to be all nuclear like France in 10 or 20 years.  Even in the most optimistic situations for the next 10-15 years we are talking about either replacing gas or coal plants.

If we are talking about 20 or 30 years in the future then keep in mind that solar is going to be a lot cheaper at that point: http://en.wikipedia.org/wiki/File:Price_history_of_silicon_PV_cells_since_1977.svg

If we hypothesize solar costs of under a dollar a kilowat of generation then far and away the best solution is just make a huge excess of solar electricity and then have the grid sort out the difficulties.  Even if we lost 75% of it in transmission, that's still cheap, abundant electricity.  And probably there will be efforts to shift energy intensive processes to times and locations where these is excess power.

[10ebbor10]

Under a dollar a kilowatt is a serious cost decrease though, I don't think we'll see those decreases going further.

[GavJ]

Sure, except building the batteries, or building the power lines capable of carrying 4x our electrical needs across the world (such that you can lose 75% of it), or whatever crazy scheme could ITSELF cost more than an entire nuclear power grid + plants, potentially.

That's why looking at PV cells alone is fairly useless. They could be FREE and you might still have a more expensive system, potentially.

And adding in those numbers is beyond anybody here. I provided current numbers. For future estimates, you need to find a professional, well regarded source that accounts for grid costs and service replacement time and energy storage and blah blah. We can't just guess from our armchairs in any meaningful way.

[mainiac]

Sure, except building the batteries, or building the power lines capable of carrying 4x our electrical needs across the world (such that you can lose 75% of it), or whatever crazy scheme could ITSELF cost more than an entire nuclear power grid + plants, potentially.

The cost of a "smart grid" would be around 400 billion.  Not nothing but keep in mind that existing electricity costs are nearly that much for a year.  If you can make energy cheaper then paying to ship it around makes sense.

[GavJ]

1) What does that even mean? A grid costs initial and ongoing annual costs. One number doesn't make sense. Over how long is that, what area (U.S. only?), what features (needs to include storage and transit of energy to non sunny places)?
2) Citation?