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97 comments on A gesture is sometimes important...

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Stuart Staniford on November 22, 2005 - 4:29am Permalink | Subthread | Parent | Comments top
Can you give a source for the claim about concentrator photovoltaics with a payback of months.
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wkwillis on November 22, 2005 - 5:55am Permalink | Subthread | Parent | Comments top
That's an energy payback of months, not an economic payback.
Concentrator photovoltaic uses fabricated modules to concentrate up to, well, 40,000 times sunlight is theoretically possible, but practical is more like 1,000 because of cooling and thermal shock problems.
These modules are expensive because of the labor cost of fabrication and assembly. They are steel and plastic and glass and aluminum and much less energy expensive per pound than crystal silicon. Crystal silicon requires that you not only reduce silica to silicon, but that you hold it in a molten state for days while the cooled seed crystalizes the silicon. I worked in a wafer fab and you should have seen the busbars for the power supply.
So the cost of concentrator photovoltaic electricity depends on the cost of labor instead of the cost of silicon. Despite the fact that silicon wafer prices have been going down since the seventies (till recently) the concentrator economics haven't improved because construction labor costs are only down 20% since the seventies.
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Leanan on November 22, 2005 - 12:09pm Permalink | Subthread | Parent | Comments top
They are steel and plastic and glass and aluminum and much less energy expensive per pound than crystal silicon.

Maybe so, but still not cheap, and they will be more expensive still in an energy-poor world.  

As always, the problem lies in the the scaling-up.

As my sister put it, we are like fish trying to imagine the desert.  Energy has been so cheap and abundant for us, for so long, we have a hard time imagining what it was like when the energy cost of steel and glass was so high that they were reserved for the wealthy only.  

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GeoPoet on November 22, 2005 - 12:46pm Permalink | Subthread | Parent | Comments top
As you may recall, there was a copper age, a bronze age, and an iron age. Any of these people could have constructed a solar collector, although without silvered mirrors, its efficiency may have been low. The dish frame can be reinforced wood - the slop allowable in the focusing of these collectors is fairly large - or it could be simple fiberglass mat construction, like a hot tub or a surfboard. If weight was not an issue, one could even use clay and actually make a giant bowl!

This is not high tech - this is low tech. It is easy - the Egyptians used solar reflectors to illuminate inside their temples and pyramids, concentrating more of them when more light was needed. When were silvered mirrors invented? All of these items are hundreds of years old.

The only new parts of the concentrator system are the heliostat and generator parts. If this were to be done in the 1600's or 1700's, then a clockwork heliostat could even have been employed. Generators are simply not high tech either - some magnets and copper wire wound round. Remember that Ben Franklin dabbled in electricity, long before the oil age.

I am currently building one of these things in my free time - pleae don't make it seem like some kind of high tech solution. It simply isn't.

But it does work. How well I should be able to tell you by summer....

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step back on November 22, 2005 - 1:13pm Permalink | Subthread | Parent | Comments top
Will your solar concentrater cook a turkey?

Have a happy ....

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GeoPoet on November 23, 2005 - 9:23am Permalink | Subthread | Parent | Comments top
stepback -

Yes, although it would crisp it pretty quickly. I don't have all the mirrors set yet (about 70%), and it is quite dangerous at the focal point. At high noon, it's hitting the central focal point with 150 .025 spots at between 350 and 500 degrees...

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Leanan on November 22, 2005 - 1:56pm Permalink | Subthread | Parent | Comments top
It is easy - the Egyptians used solar reflectors to illuminate inside their temples and pyramids, concentrating more of them when more light was needed.

Temples and pyramids.  Not Joe Sixpack's living room.  That's my point.  "Simple" technology may have been known, but it was too expensive for ordinary folk.  Mirrors were luxury items until relatively recently.    

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Stoneleigh on November 22, 2005 - 5:47pm Permalink | Subthread | Parent | Comments top
It wasn't so long ago that a small amount of window glass would have been a luxury, let alone mirrors. In Shakespeare's time, ordinary folk lucky enough to have had a house at all would have had windows made of boiled horn. They let in a little light and kept out the worst of the drafts, but that was all. You couldn't see through them.

It's only in very recent times that a substantial middle class has gained access to relative luxuries and peak oil is likely to reverse that trend sharply.

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GeoPoet on November 23, 2005 - 9:29am Permalink | Subthread | Parent | Comments top
stoneleigh -

The clock isn't turning back but going forward. Glass is no longer something enigmatic and valuable, but something ubiquitous and even a significant part of our waste stream. I know you have seen the house built of coke bottles on TV probably. Point being, glass is no longer what it was - now it is everywhere. Unless it is total collapse, glassmaking will continue to go on at a relatively cheap price, because all it requires is heat from ANY source...

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Leanan on November 23, 2005 - 10:37am Permalink | Subthread | Parent | Comments top
It's the heat that's the problem, not the "mystery."

People have been making glass for 5,000 years.  The problem is the heat it takes to work it.  The ingredients are relatively cheap, it's working it that is expensive.  

Getting enough fuel (firewood, dung, etc.) to cook and heat with was a neverending struggle before we discovered fossil fuels.  It still is, for much of the undeveloped world.  The fuel cost required to heat glass to 2000 degrees is what made it expensive, not the "mystery."

This is what I mean when I say we're like fish trying to imagine the desert.  We assume that ancient peoples didn't do what we do because they didn't know how to do it.  The idea that they knew how to do it but it was too energy-intensive is hard for us to understand.

Of course we have lots of scrap now.  Plastic, aluminum, steel, glass.  However, it will take a lot of energy - heat - to work into new uses.  This might be a good temporary solution.  If we do it with the knowledge that we are just cushioning the drop and it is not sustainable, I'd be all for it.  But it's not a long-term solution.  

IOW...yes, glassmaking will most certainly go on.  But not at a "cheap" price.  

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copperweaver on November 23, 2005 - 11:44am Permalink | Subthread | Parent | Comments top
I don't see materials goods being much of an issue in a post peek world.  Photovoltaic panels and other solid state devices will not be easy and probably imposable to manufacture, but we defiantly have tons of material goods to scavenge.  Food and medicine will be the scarce commodities.  There are lots of wonderful medicinal plants, but you have to know where to find them and how to use them.  I often wonder how humans will adapt to all of the toxins that are currently in our bodies and the environment.  I think we already see many of the effects of these toxins via cancer, infertility, and other diseases.  Health care will be a huge issue in a post peek world....
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GeoPoet on November 23, 2005 - 9:25am Permalink | Subthread | Parent | Comments top
Well, it's not mysterious any longer, and you can find mirrors everywhere, even in junkpiles. Think of how many will get chunked out in New Orleans alone. Just by picking through scrap one could build this type of setup.

We aren't in that time period any longer - the argument isn't valid with all the cheap crap we have cluttering up our world these days.

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Atticman on November 22, 2005 - 9:16pm Permalink | Subthread | Parent | Comments top
how about the tired Coyote in a chicken house analogy?The chicken are healthy and run around,the coyote is hungry but tired.

The U.S. is obviously the coyote in this histogram and energy solutions are abundantly running around untouched by us loathesome Yankees

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