The Oil Drum | Concentrating Solar Power

184 comments on Concentrating Solar Power

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PrisonerX on May 30, 2007 - 8:47pm

I visited a web site of a guy from Africa that is using Mylar and satellite dishes to make these things on a personal level.

Drill a hole in the back of the sat dish big enough for a tube

Attach the mylar across the sat dish so that it is sealed.

Put tube in the hole.

Use a pump to siphon the air out of the dish.

This draws the air out and pulls the mylar in toward the back creating a parabola.

Have something in front where you wish to aim for the focal point.

Once you have the distance down turn off pump and seal the tube.

Then never ever walk in front or let anyone else.

The guy claimed he could put a beam thru metal in no time.

I've been keeping my eye out for used dishes since then on the curbs.

even small ones like sat tv should work.

He claims you make a box and get the same effect, seems like the dish shape would work better, don't know.

Weather is the problem for the mylar. thin mylar by the roll is not very expensive.

Quid Clarius Astris
Ubi Bene ibi patria

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Mike C on May 31, 2007 - 12:07am

Googling "solar ovens" or "solar cookers" brings up loads of pages, many of which describe taking discarded satellite dishes and replacing the surface with reflective aluminum.

But here's my favorite design, because
a) you don't need to find a cast-off dish;
b) you could make it as large/powerful as you want; and
c) selecting the size of the individual mirrors you use lets you get whatever size focus you want to end up with

http://amasci.com/amateur/mirror.html

"The result was approximately 1000 watts of solar influx concentrated on an area the size of a silver dollar. Wood ignited with an audible "pop" the instant it entered the focal point. Toast burns instantly. Aluminum melts after 15 seconds. Half inch copper tubing deforms under it's own weight after 20 seconds. Steel glows red in about the same time."

Besides cooking, one of these could be very useful for
- heating a pressure cooker/canner for preserving produce (which you'd be doing during the summer, when there's plenty of sun)
- boiling 5 gallons of wort for making beer
- a smaller version could be used for heating an IcyBall: http://en.wikipedia.org/wiki/Icyball
http://www.ggw.org/~cac/IcyBall/crosley_icyball.html (see especially the home-made one at the bottom of the page)

I especially like the pressure-canning idea. Once you got this thing set up & working, you'd be able to preserve what you get out of your garden year after year, with no electricity or fossil-fuel input whatsoever...

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ericy on May 31, 2007 - 9:46am

I was wondering whether CSP could be used to make concrete. Part of the process involves mixing up some common chemicals, and heating to about 1400C in a kiln:

http://en.wikipedia.org/wiki/Portland_cement

Typical design for a kiln given here:

http://en.wikipedia.org/wiki/Cement_kiln

So the question I have is whether it is possible to design a kiln that could directly use CSP instead of oil/natural gas.

It might or might not be possible to use the CSP directly - depends on whether you can design the kiln to get the material heated properly. It might be easier to replace the flame in an existing kiln with a hydrogen flame, but this would be clearly less efficient.

There are other industrial processes which require heat in one form or another that currently use gas or oil, and my guess is that people ought to be thinking of ways to use the light of the sun directly to provide this heat.

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half full on May 31, 2007 - 11:17am

I've given this some thought myself, and concluded that it is possible to make C3S clinker, but not by the same route used in conventional kilns. Remember that 75% of PC kiln feed is limestone, and the limestone produces CO2 as it is calcined, so that about 80% of the CO2 produced in cement-making comes from the limestone, not the fuel. (and cement accounts for 5-7% of man-made CO2 globally!)

An alternative process uses molten calcium chloride, and has been around for decades.
CaCl2.H2O -> CaO + 2HCl
3CaO + SiO2 -> Ca3SiO5 (at about 700C)

Hydrated calcium chloride melts at about 180C, so the whole process can take place in liquid phase, with the silica in slurry form.

If there is an ocean or brine reservoir nearby, the CaCl2 can be made from limestone and MgCl2 brine by exchange
CaCO3 + MgCl2 -> MgCO3 + CaCl2

You also need a market for the hydrochloric acid.

The challenge here is firstly materials, because molten chlorides + HCl at high temp are extremely corrosive (remember there is water present). The whole reactor loop, and especially the solar absorber will have to be ceramic (carbides?) and able to withstand day/night thermal cycling. If you can figure this out you will be a hero.

Second challenge is business. The cement companies are global semi-monopolies with billions invested in conventional kilns, and won't change until they absolutely have to. They will buy carbon credits for decades first.

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ericy on May 31, 2007 - 12:41pm

Hadn't considered this 2nd process. On the one hand it sounds easier, on the other there would be a hell of a lot of HCl that needs to be put to good use. Reminds me of the glycerine problem with biodiesel...

The global companies will just end up chasing fossil fuels all over the world. As time goes on that will get harder, or the plants may need to relocate (esp if they are using natural gas).

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Rib on June 1, 2007 - 7:27am

Rib
I think we will have to just make less Cement.Timber houses Etc.
See company below has promise of solving issue of what to do with waste glycerol from bio fuel
VIRENT ENERGT
Cellulose /Sugar conversion to Hydrogen /Methane/MethanolCan also use waste Glycerol from Biodiesel manufacture as fuel
http://www.virent.com/
http://www.ecw.org/biomass2power/index.html

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GerryWolff on May 31, 2007 - 12:56pm

There are some thoughts along these lines at http://www.trec-uk.org.uk/csp_sections/csp_synthesis.htm .

In principle, it should be possible to use CSP for a variety of energy-hungry industrial processes.

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184 comments on Concentrating Solar Power

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