Solar Turbine Implementation - Revision history

Jeb: /* Smari */ fixed wiki formatting on this letter by removing the leading spaces.

2009-08-25T19:27:41Z

Smari: fixed wiki formatting on this letter by removing the leading spaces.

← Older revision		Revision as of 19:27, 25 August 2009
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	===Smari===		===Smari===

	Sorry to hear about the problems with reflective surfaces. We've been		Sorry to hear about the problems with reflective surfaces. We've been
	getting lots of questions at the Fab Lab about laser etching glass and		getting lots of questions at the Fab Lab about laser etching glass and
	mirrors recently, and while glass is no problem mirrors can't be done as		mirrors recently, and while glass is no problem mirrors can't be done as
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	it's currently done..		it's currently done..

	What I think you might want to do is build your own parabolic glass		What I think you might want to do is build your own parabolic glass
	sheets to specification. You could do this by, for example, milling out		sheets to specification. You could do this by, for example, milling out
	a wooden block in negative, casting silicon over that making a positive		a wooden block in negative, casting silicon over that making a positive
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	of moderate quality.		of moderate quality.

	When this is done, rough application of a molten tin-silver mixture to		When this is done, rough application of a molten tin-silver mixture to
	the back surface should both remove any roughness in the glass at that		the back surface should both remove any roughness in the glass at that
	side and provide a reflective coating.		side and provide a reflective coating.

	... but that said, making mirrors is unfortunately a bit complicated		... but that said, making mirrors is unfortunately a bit complicated
	and delicate. How can it be made simpler?		and delicate. How can it be made simpler?

	Looking forward to the next episode!		Looking forward to the next episode!

	- Smári - spm2@hi.is		- Smári - spm2@hi.is

	[[Category:Solar Turbine]]		[[Category:Solar Turbine]]

WikiSysop: /* Smari */

2009-01-12T03:44:27Z

Smari

← Older revision		Revision as of 03:44, 12 January 2009
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	- Smári - spm2@hi.is		- Smári - spm2@hi.is

			[[Category:Solar Turbine]]

Marcin: /* The Next Reflector */

2008-08-30T14:57:09Z

The Next Reflector

← Older revision		Revision as of 14:57, 30 August 2008
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	The local hardware store has 1/8" glass mirrors for $1.50 a square foot, which will easily curve under tension to our desired shape, probably won't require plywood backing and which should long outlast mylar.		The local hardware store has 1/8" glass mirrors for $1.50 a square foot, which will easily curve under tension to our desired shape, probably won't require plywood backing and which should long outlast mylar.

			==Back to the Drawing Board==

			Here is the design with the sandwich of curved surfaces:

			[[Image:reflectorsandwich.jpg]]

	==Reviews==		==Reviews==

Marcin: /* The Next Reflector */

2008-08-30T02:03:51Z

The Next Reflector

← Older revision		Revision as of 02:03, 30 August 2008
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	The local hardware store has 1/8" glass mirrors for $1.50 a square foot, which will easily curve under tension to our desired shape, probably won't require plywood backing and which should long outlast mylar.		The local hardware store has 1/8" glass mirrors for $1.50 a square foot, which will easily curve under tension to our desired shape, probably won't require plywood backing and which should long outlast mylar.


			==Reviews==
			===Peter Clark===
			Peter Clark <2PeterClark@gmail.com>

			Marcin:

			I enjoy your reporting. Thanks.

			The group that I was working with in the 1970's found two ways to create good reflector surfaces using aluminized mylar:

			1. Pull a vacuum behind film that is mounted in a circular frame.
			2. Use a formed shape to push the mylar, and then rigidify it. We used a searchlight mirror as a mold for a fiberglass "parabolic mound", stretched the mylar over a ring, and pushed the ring down around the mound, the coated it in fiberglass (ugh).

			Glass mirrors in a Fresnel arrangement is another option.

			These things are shown in the book that I wrote at the time- the Natural Energy Workbook Vol. II. It has been out-of-print for 20 years, but is available used on Amazon.

			Keep up the good work!

			Peter

			===Smari===

			Sorry to hear about the problems with reflective surfaces. We've been
			getting lots of questions at the Fab Lab about laser etching glass and
			mirrors recently, and while glass is no problem mirrors can't be done as
			they'll scatter the beam and fudge up the laser. So I checked out how
			it's currently done..

			What I think you might want to do is build your own parabolic glass
			sheets to specification. You could do this by, for example, milling out
			a wooden block in negative, casting silicon over that making a positive
			mold, then stone casting over that (ceramic mold). It's a three step
			process but it'll give you lots of leeway for accuracy, specially as the
			silicon will maintain details very well. Given the stone mold, pad it
			with green sand (mix of silica, water, and some other stuff) and put
			pure silica (SiO2) mixed with sodium carbonate (Na2CO3) into the mold
			and bake at 1500°C. Supposedly this should give you a translucent sheet
			of moderate quality.

			When this is done, rough application of a molten tin-silver mixture to
			the back surface should both remove any roughness in the glass at that
			side and provide a reflective coating.

			... but that said, making mirrors is unfortunately a bit complicated
			and delicate. How can it be made simpler?

			Looking forward to the next episode!

			- Smári - spm2@hi.is

WikiSysop: /* Second Reflector */

2008-08-18T02:34:14Z

Second Reflector

← Older revision		Revision as of 02:34, 18 August 2008
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	[[Image:reflector2.jpg]]		[[Image:reflector2.jpg]]
	[[Image:target.jpg]]		[[Image:target.jpg]]
			[[Image:elliot.jpg]]
			[[Image:structure.jpg]]

	==The Next Reflector==		==The Next Reflector==

WikiSysop: /* Second Reflector */

2008-08-18T02:29:22Z

Second Reflector

← Older revision		Revision as of 02:29, 18 August 2008
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	[[Image:testing.jpg]]		[[Image:testing.jpg]]
			[[Image:reflector2.jpg]]
			[[Image:target.jpg]]

	==The Next Reflector==		==The Next Reflector==

WikiSysop: /* The First Reflector */

2008-08-18T02:27:19Z

The First Reflector

← Older revision		Revision as of 02:27, 18 August 2008
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	Under greater intensity light however, the flaws of the design became apparent as a foot wide strip was clearly illuminated. The imprecise optics may be due to the diffuse reflectance of the aluminum foil. Experiments with mylar when it arrives will be telling.		Under greater intensity light however, the flaws of the design became apparent as a foot wide strip was clearly illuminated. The imprecise optics may be due to the diffuse reflectance of the aluminum foil. Experiments with mylar when it arrives will be telling.

			==Second Reflector==

			Getting ready for testing the second collector:

			[[Image:testing.jpg]]

	==The Next Reflector==		==The Next Reflector==

Offonoffoffonoff: New page: This is a log of the implementation process, dead ends and all. ==The First Reflector== The first idea to be implemented was a 4'x 8' tensioned plywood panel covered in aluminum foil (la...

2008-08-17T19:01:01Z

New page: This is a log of the implementation process, dead ends and all. ==The First Reflector== The first idea to be implemented was a 4'x 8' tensioned plywood panel covered in aluminum foil (la...

New page

This is a log of the implementation process, dead ends and all.

==The First Reflector==

The first idea to be implemented was a 4'x 8' tensioned plywood panel covered in aluminum foil (later to be mylar). The tension applied by two rows of bolts with wingnuts holds the plywood in a parabolic shape.

[[Image:First_panel.jpg]]

[[Image:First_panel2.jpg]]

At sundown, this panel appeared to give a tight focus (as Ben learned first hand).

[[Image:First_panel_andben.jpg]]

Under greater intensity light however, the flaws of the design became apparent as a foot wide strip was clearly illuminated. The imprecise optics may be due to the diffuse reflectance of the aluminum foil. Experiments with mylar when it arrives will be telling.

==The Next Reflector==

Due to the changing focal length of the system as the suns angle parallel to the trough axis changes, the concentrating ability of a single parabolic reflector is limited to about 2 in an east-west axis system. Therefore, the next panel implementation will be only one foot wide as opposed to four feet. Experiments with mylar stuck to a curved plywood or oriented strand board backing will be preformed. Strectched mylar seems unlikely due to the high cost of thick (5 mil) mylar.

The local hardware store has 1/8" glass mirrors for $1.50 a square foot, which will easily curve under tension to our desired shape, probably won't require plywood backing and which should long outlast mylar.