[Tikib]

Here's something that's always interested me. How big does a renewable plant need to be to be sustainable.

For instance the huge dams in China and South America are probably sustainable because the power from them could be used to make concrete metal etc to repair them.

How big would a csp plant have to be to be sustainable?

[GHung]

Sustainable energy is the sun on your back and the deadfall you find in the forest for your campfire; hopefully enough to get you through the winter. Anything much beyond that gets problematic.

It's human behaviour that isn't sustainable, not our energy sources.

[Hawkcreek]

Interesting question.
A 100 watt solar PV panel would need damn near eternity to produce enough power to mine the ore, smelt the aluminum, mine the sand and other stuff for tempered glass, produce a doped solar cell, assemble the thing, and then pay for the food, housing, and transport for all the people doing this stuff. A one mega-watt assembly? I don't know.
Maybe it isn't sustainable at any size.

[Tikib]

I was thinking more along the lines of a 1 gw solar thermal plant which is eminently achievable

[Newfie]

You got two good answers above.

Would you understand better if they repeated it a billion times?

[Tikib]

Neither has any maths to back it up. In a good location solar has a fairly positive erei.

It's far too late to save the world from fossil fuel depletion but maybe a country or even just a city.

[Newfie]

Well then do the math.

But what price will you ascribe to a bbl of oil when doing the math? You might make it work at $50 or $100/bbl.

But what happens when we do hit the peak hard and oil becomes precious? Then your return on investment goes to hell.

We are building relatively cheap solar because we have relatively cheap oil.

In a sustainable model we use no oil. None. Now how you gonna build that solar?

This is not a new discussion. James Lovelock has returned to favor nukes as the best way to leverage the little fossil energy we have left to assure available energy in the future.

So, not to make the maths too hard, use ..$1,000/bbl and see how it works out.

[Tikib]

Well as I am trying to say if you build the solar ahead of time you can use that solar to build more solar. Aluminium is smelted near hydro plants theirs no law of nature saying it must be done with fossil fuels.

[Tikib]

The human race has never been in a situation where they have a large csp plant and no fossil fuels so again it's not obvious at all if it's possible to use the power from the plant to keep the plant going.

my guess would be that their is a point where you can break even and maintain the plant.

Talking of plants they maintain themselves with no fossil fuel input.

[Newfie]

That's right, over billions of years of evolution nature has perfected the best solar power storage system possible. Trees.

You think you can do better!

Harrumph!

Look, sorry to be such a downer. You are a new guy. Looks around, you will find kindred hopeful spirits. But there are a few hard core realist also.

Not everyone is as grumpy as I. Welcome aboard.

[dashster]

$this->bbcode_second_pass_quote('Tikib', 'H')ere's something that's always interested me. How big does a renewable plant need to be to be sustainable.

For instance the huge dams in China and South America are probably sustainable because the power from them could be used to make concrete metal etc to repair them.

How big would a csp plant have to be to be sustainable?

[Keith_McClary]

$this->bbcode_second_pass_quote('dashster', 'F')rom the standpoint of just producing excess power over it's lifetime that could be used for the energy required in repairs over its lifetime, it would seem that we are now at the cost point where they all do that. If it took more energy to repair them than they could put out then none of them would make any economic sense no matter what the tax subsidy was to build them.

[dashster]

$this->bbcode_second_pass_quote('Keith_McClary', '')$this->bbcode_second_pass_quote('dashster', 'F')rom the standpoint of just producing excess power over it's lifetime that could be used for the energy required in repairs over its lifetime, it would seem that we are now at the cost point where they all do that. If it took more energy to repair them than they could put out then none of them would make any economic sense no matter what the tax subsidy was to build them.

[Tikib]

$this->bbcode_second_pass_quote('Newfie', 'T')hat's right, over billions of years of evolution nature has perfected the best solar power storage system possible. Trees.

You think you can do better!

Harrumph!

Look, sorry to be such a downer. You are a new guy. Looks around, you will find kindred hopeful spirits. But there are a few hard core realist also.

Not everyone is as grumpy as I. Welcome aboard.

[vtsnowedin]

Between the USA and Canada there are 138 MW of installed hydo power capacity.
You can use that to build you windmill and solar panel plants as well as run the mines and aluminum smelters to make you raw materials. After that it is just a matter of EROEI for your production from the factory. As any factory would be expected to produce thousands of units over years of service the imbedded (invested) energy in each panel or windmill from the factory's creation would be quite small per unit. The energy to mine transport and smelt the metals needed would be the tripping point. Therein lies the largest energy component embedded in each panel or wind mill. From what I gather windmills have a EROEI of around 17 and PV solar panels around 2 to 4 depending on where they are deployed So the windmills are probably sustainable if built on good sites and the PV panels even if installed in favorable locations while positive will not return enough energy to be worth the effort as the economy needs a EROEI of 5 or better to function.

[Newfie]

$this->bbcode_second_pass_quote('Tikib', '')$this->bbcode_second_pass_quote('Newfie', 'T')hat's right, over billions of years of evolution nature has perfected the best solar power storage system possible. Trees.

You think you can do better!

Harrumph!

Look, sorry to be such a downer. You are a new guy. Looks around, you will find kindred hopeful spirits. But there are a few hard core realist also.

Not everyone is as grumpy as I. Welcome aboard.

[Newfie]

Also, when oil goes away, or gets dear, plastics go away.

So that new sustainable culture will have to exist without plastics. Including nylon and polyester clothing.

[GHung]

I'm surprized nobody has posted a link to sunweb's article; Can you make a wind turbine without fossil fuels?:

http://peakoil.com/alternative-energy/c ... ssil-fuels

[Tikib]

I feel like I am missing something. I didn't say it
Was easy to build renewables without fossils. But it is doable providing the renewables resource was big enough.

I think your big gripe is the liquid fuels issue and that's a biggy as its very difficult to move stuff without oil. All I can say is sail boats and electric trains. no neither of us them is as good as the fossil alternative but I didn't say they were.