Re: [Vo]:Fresnel focused solar
The higher the concentration, the more accuracy required in the sun tracker. An eqitorial mount, where the rotation axis is parallel to the earth's axis at the installation location, is a good start. However, as the seasons progress, the sun's elevatiion changes, so the tracker must operated in three axes. If you want to place the array on an arbitraily placed roof, it gets more complicated. All can be solved and cheap computers can do the job, but it does get complicated and is a non-neglible cost to the approach. Mike Carrell
Re: [Vo]:Fresnel focused solar
Howdy Mike, This firm, Solargenix was owned by Duke Energy and now owned by a Spanish consortium. They are marketing their electric power producing system across the world and putting some very interesting contracts together. One of their secrets is keeping the cost of operations low.. that means labor and unattended stations. The Spanish have a goal to search out stable and long term revenue streams ( Ma Bell at it's finest) Another example is the Spanish entree into toll roads. Cintra of Spain has made inroads both in Canada and the USA. Masters at both politics and money management, these Spanish consortiums are on the move. The world is awash in money searching for investments. GE was a world leader in these type financial strategies.. what happened to GE?? This generation of GE leadership was taken over. The scary part is that an entire financial seesaw can now tilt in a very short period of time whereas it took the barons of Wall Street more than a 100 years to position the USA to lead the world of capital... Yet, suddenly, In two presidential terms of office by Clinton and Bush.. Poof! Leads me to think that LENR is a victim of indifference greater than ignorance and opposition combined. Richard http://www.eere.energy.gov/news/news_detail.cfm/news_id=9723 http://www.renewableenergyworld.com/rea/news/story?id=44696 Mike Carroll wrote, The higher the concentration, the more accuracy required in the sun tracker. An eqitorial mount, where the rotation axis is parallel to the earth's axis at the installation location, is a good start. However, as the seasons progress, the sun's elevatiion changes, so the tracker must operated in three axes. If you want to place the array on an arbitraily placed roof, it gets more complicated. All can be solved and cheap computers can do the job, but it does get complicated and is a non-neglible cost to the approach.
[Vo]:Question regarding basic solid mechanics and one directional applied stress
Hi If I put a wheight on a vertical cylinder it will be shortened and its radius will be somewhat increased. I wonder if the radial increase is considered a negative stress in radial direction? Is the stress tensor something like this? -a 0 0 T= 0 0 0 0 0 b Where a and b are positive values and the coordinates are cylindrical *ρ*, * φ*, *z* (ISO 31-11). David -- David Jonsson Sweden phone callto:+46703000370
Re: [Vo]:Question regarding basic solid mechanics and one directional applied stress
Howdy David, A brain teaser question. The answer is yes if you accept that expansion and contraction actually occurs depending on the materials of the cylinder. Mention of the cylinder being solid presents another teaser. Certain solids react to being stressed. Predictive science of materials is become the cutting edge technology whereas in the past we used empirical tests alone. LIke non-invasive quality control tests, predictive science is what the Russians face in discovering what is happening with their Soyuv space capsule re-entry problems. You may be working on that task so I wish you well. You may set up a testing method of proving that the stress caculated is indeed negative by building a sorta makeshift air comparison picnometer of a version used for density measurement of dry drilling mud. Fun stuff. Richard - Original Message - From: David Jonsson To: vortex-l@eskimo.com Sent: Sunday, May 04, 2008 3:36 PM Subject: [Vo]:Question regarding basic solid mechanics and one directional applied stress Hi If I put a wheight on a vertical cylinder it will be shortened and its radius will be somewhat increased. I wonder if the radial increase is considered a negative stress in radial direction? Is the stress tensor something like this? -a 0 0 T= 0 0 0 0 0 b Where a and b are positive values and the coordinates are cylindrical ρ, φ, z (ISO 31-11). David -- David Jonsson Sweden phone callto:+46703000370 -- No virus found in this incoming message. Checked by AVG. Version: 7.5.524 / Virus Database: 269.23.8/1413 - Release Date: 5/3/2008 11:22 AM
Re: [Vo]:Stationary Fresnel Array (Hybrid)
Stephen A. Lawrence wrote: Jones Beene wrote: It is perhaps possible to provide a *stationary* Fresnel array which has virtual tracking. Imagine a fixed, stationary array of Fresnel lens and underlying photocells, somewhat as in this image: http://www.sinosolargroup.com/en/images/toushe33.JPG ... and, with such a panel sited on a south-facing roof, exactly the same way as a normal fixed solar-panel would be sited - except that this one is requiring 500 time less area of actual photocells than the normal array. This site lists the advantage of 500:1 concentration: http://www.emcore.com/solar_photovoltaics/terrestrial_concentrator_photovoltaic_arrays Needless to say, since Nanosolar gives only perhaps a 5-to-1 cost advantage with their printed cell, and it is a far less-efficient cell, the comparative advantages of any kind of concentrator array, in cost, would be *huge* - except- for the one issue. That issue being the need, added complexity and aesthetics (for home use) which 2-axis tracking demands. Here is how to overcome most of that added (tracking cost) and other issues, while still keep the solar array fixed and stationary. It is not a unique idea, as it has been suggested for other uses, but it may be unique when it is combined with a Fresnel concentrator, especially the kind of Fresnel which itself is already combined with an angled cone secondary. These are called self-focusing but that is a misnomer. They are also called non-imaging http://en.wikipedia.org/wiki/Non-imaging_optics I'm not sure about this article. Among other things it says: Imaging optics can concentrate sunlight to, at most, the same flux found at the surface of the sun. This is false as written; a lens of f/0.5 produces an image of the sun with flux equal to the flux at the surface of the sun, and a larger lens -- or shorter focal length -- produces a flux /larger/ than that at the surface of the sun. There's something related and true which they may be trying to say, but the statement on the page, as written, is not correct. This leads me to wonder how firmly grounded the rest of that particular article is. Want to produce a spot that's brighter than the surface of the sun? No prob; you can get the materials from Edmund's catalog. Maybe you can't build a classical glass lens with f/0.5 but there's no prob making a Fresnel lens to do the job. If you can find a big Fresnel lens of f/0.5 you're all set. (It's possible the refractive indices of available plastics don't allow such short f/number lenses; I haven't tried to work out the geometry of the lens surface which would be required.) If you can't, you can make one; take three or four ordinary 12 square solar furnace-style Fresnel lenses (available from Edmund's, or at least they used to be) outside on a sunny day, stack them up in a sandwich (which cuts the focal length by a factor equal to the number of lenses in the sandwich), focus the sun, and voila, you've blown a hole in the concrete sidewalk. (Or at any rate you can blow a small chip out of it; I've done it, using a single 12 square lens, never mind the stack.) But don't look at the spot unless you're equipped with something appropriate, like welder's glasses; it is very bright indeed. As I recall the basic solar furnace Edmund lens was not much over f/1 to start with, so four of the them stacked should be neatly under f/0.5. To find the focal length of a stack of lenses, express their focal lengths in diopters and just add them up. A 1 foot diameter circular lens with 18 focal length is an F/2 lens. Er, rather, it's an 1/1.5 lens. 18 = 0.46 meters = 2.2 diopters. Four of them, stacked, have a focal length of about 8.7 diopters, or 0.11 meters, or 4.5 inches. For a 12 diameter lens, that's f/0.38, and it should do the job. A page I happen to have on image brightness: http://physicsinsights.org/simple_camera_brightness_1.html And here's a not-quite-airtight proof that you can't build a telescope which will make things look brighter when you look through it (sorry, you can never see things with your eyes the way they look in the Hubble photos, even if they let you go up on the shuttle and look in the eyepiece [if it had an eyepiece :-) ] ) : http://physicsinsights.org/simple_optics_brightness_1.html This type of optics has some added loss, but it seems to provide a great deal more latitude than a normal Fresnel. It will self-focus (in the patent claims at least) within plus or minus 30 degrees of direct focus (or better). With an initial south facing placement, the use of non-imaging optics will allow you to dispense with one axis of tracking, just as with the parabolic trough; but still requires the one axis for early morning and late evening. OK - the further enhancement is to implement this type of limited self-focusing along with a mirrored-slat louver array, which lays above the Fresnel array. The mirrored slats are long, thin
Re: [Vo]:Re: Fresnel focused solar
Michel wrote: Sounds impressive! So what material are you using in your roll process? Do you have a web site showing these things? The substrate I normally use is polyethylene pterphthalate (PET) film, generally from 12 microns to 125 microns in thickness, depending on the application. The fresnel structure itself is formed in a proprietary thermoset layer which imparts a moisture and short-wave UV barrier, greatly extending the outdoor survivablilty of the PET film. I had originally intended that these lens arrays be held in place by their own great tensile strength, but as a practical matter, lamination to glass is preferred, with the glass side toward the sun and the elements. The glass and the window film type adhesive give the film unmatched thermal stability and 20-year outdoor life. My company website is so far out of date that I'm embarrassed to look at it myself. There is little information about the fresnel lenses. But if you must look at it: www.spectratek.net Until I begin to make something materially useful with my processes, I am mildly distressed whenever I see the name of Augustin-Jean Fresnel up there on the Eiffel Tower along with all those other great French scientists. Not only did he invent the fresnel lens, but worked out all the theory of near-field diffraction on which holography is based. I often wonder what he would think. M. Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ
Re: [Vo]:Stationary Fresnel Array (Hybrid)
Howdy Jones, I was surprised that no one picked up on my comment regarding sealed beam headlamps. The technology, the manufacturing process and the materials are available except for the element for use as a solar collector. Richard
