Reflective Material

Greenpower
http://greenpowerscience.com/SHOPREFLECTIVEBUY.html

Reflectec

 * http://alanod-solar.com/opencms/opencms/Reflexion/index.html
 * http://www.reflectechsolar.com/pricing.html from http://openfarmtech.org/index.php/Rick_Thomas_on_solar.
 * Mylar (brand name)

Reflectech produces a reflective material very close to the efficiency of mirror, that is covered over any object to form a reflective surfaces such as a parabolic dish. Thus we can use scrap material, compressed wood, crushed glass to form parabolic troughs etc and then cove it with this reflective material. Without reflectech a DIY approach to energy production won't be feasible. Cover a diy SolarLinks#Solar_ring with Reflectech at around $22 per square meter.

http://www.altenergymag.com/news_detail.php?pr_id=12617

ReflecTech® Mirror Film is the key design-driving innovation in the award-winning SkyTrough® parabolic trough solar concentrator. Both ReflecTech® Mirror Film and SkyTrough™ were developed through cooperative research with the U.S. National Renewable Energy Laboratory.

Reflectech produces a reflective material very close to the efficiency of mirror, that is covered over any object to form a reflective surfaces such as a parabolic dish. Thus we can use scrap material, compressed wood, crushed glass to form parabolic troughs etc and then cove it with this reflective material. Without reflectech a DIY approach to energy production won't be feasible. Cover a diy SolarLinks with Reflectech at around $22 per square meter.
 * http://www.reflectechsolar.com/pricing.html from http://openfarmtech.org/index.php/Rick_Thomas_on_solar.

http://www.altenergymag.com/news_detail.php?pr_id=12617

ReflecTech® Mirror Film is the key design-driving innovation in the award-winning SkyTrough® parabolic trough solar concentrator. Both ReflecTech® Mirror Film and SkyTrough™ were developed through cooperative research with the U.S. National Renewable Energy Laboratory. SkyTrakker™ provides the local electronics that control and direct a trough’s movement by determining the optimal position for the collector based on calculating the sun’s position. The SkyTrakker™ represents a step-change in features, reliability and life-cycle costs of control units for parabolic trough power plants.
 * http://www.skyfuel.com/#/OUR%20PRODUCTS/

SkyTrakker™ is a critical component of SkyFuel’s product design and it is also available to the Concentrated Solar Power (CSP) industry for use in parabolic trough projects.

SkyFuel, in partnership with the Helac Corporation, have combined the SkyTrakker™ with a customized L30 helical, hydraulic rotary actuator to make the OnSun™ tracking, control and drive system.

Innovative SkyTrakker™ system features include:

• Advanced Health Monitoring – Capability to monitor and diagnose the solar collector performance and drive system operation

• Green Power Consumption – Reduced parasitic losses; half the power usage of prior generation control systems

• Variable Frequency Drive Motor – Controls the startup of the hydraulic pump motor, limits inrush current, allows for the most precise sun tracking and reduces electricity consumption.

• Flexible Communications – Network wired (RS-485) and/or wireless (2.4GHz RF) and Local PC control (USB).

• Flexible Electrical Power Inputs - Accepts from 110VAC to 220VAC single or three-phase.

• Easy Installation – The entire system is comprised of only two major elements for quick mounting and connection.

The combination of these features provide a trouble-free parabolic trough sun tracking system resulting in reduced operating costs and greater power production.

Styrofoam
(http://cr4.globalspec.com/thread/35459/Best-Reflective-Material-for-Solar-Trough ref for styrofoam, polish aluminium, )  Try aluminized Mylar. It is extremely thin ,.00025" and inexpensive. If you've ever seen the space blanket, that is aluminized Mylar. I have seen it used in a parabolic reflector by creating a slight vacuum behind it. The material is cheap $ 70/# ( 9000 sq.yd/#) enough to throw away when it gets dirty

Here in Germany we have an aluminium foil, glued to a Styrofoam backing, about 4mm thick. Its for preventing heat from radiators being absorbed into the wall where the rad is mounted. Very,very effective.........and really cheap. Its really easily glued with a glue for Styrofoam (most normal glues melt it!) onto any flat or curved surface, even complex curves can be covered with a few judicial cuts......very flexible..... Any heat absorbed by the aluminium cannot get into the backing (well most anyway!) and eventually gets radiated back. I feel strongly, if available in your country, that this is exactly what you are looking for.... Main reasons for recommending this foil backed styrofoam is Foil alone could do it, but is tricky to handle and glue, this stuff I am recommending is easy to handle and glue and makes a more profession looking job in the end...

Polished Aluminium
I have no experience building solar troughs "yet", but aluminum sheeting can be easily polished to a brilliant mirror finish using a simple cotton polishing wheel attached to a power drill. Use the wheel with aluminum specific cutting polish. If exposed to the elements, you'll need to repolish frequently, hence the aluminium must be glazed with glass. I polished a Triumph twin using this method and it's blinding to look at in sunlight. Any coated aluminum will work well. Uncoated aluminum will oxidize turning white over time. Stay away from back surface mirrors they absorb a lot of heat.

A formed glass mirror is best. The next is chromed steel. Aluminium is good but requires maintenance. The cheapest and shortest lived but also effective is alum-mylar film. All of these if your goal is a point of focus. I built a solar oven that used 10 1ft square mirrors to heat the black copper plate transfer behind a glass and insulating air. I put the mirrors on camera tripods and adusted then with help of others every .5 hr. A pain but effect enough to get temps of 350deg F for enought time to cook (warm up) a smoked ham.

Depends on your definition of "best". The performance/cost ratio is pretty high for aluminum spray paint applied to a smooth surface. The aluminum foil approach sounds pretty good for the money also.

Making mirrors
http://www.mirrorsheeting.com/ In order to make a mirror, it is critical that the mirror sheeting be as flat as possible. People have had varying success with different strategies of doing this, a few of which we have described below. Feel free to give these ideas a try, or try your own.

If you decide to make a mirror, the first step I suggest is ordering samples. You need to be able to make the mirror flat, so choose a type of sheeting that you think you can accomplish this with or you will get distortion in the reflected image. The mirror sheeting does scratch easily, so you need to clean it with a polishing cloth and lemon pledge, or you can cover it with the extra clear film.

Some people use thin material and stretch it on a frame, the end result of which is similar to "mylar mirrors" on frames that usually sell for about $600.00 on the web. Others use the thicker film and tensioners (can be ordered below) to mount it. Some use double back mounting tape, some wooden dowels or boards on the top and bottom. Some recommendations regarding this procedure can be found at the link here: Instructions for a portable mirror on a frame. See  Mirror making

Solution
Glue Mylar film over a surface and then cover with thin sheet of polycarbonate to prevent oxidation of the aluminum surface. Try and make a vacuum between polyc. sheet and mylar or any other polished aluminum sheet. http://www.fsec.ucf.edu/en/research/solarthermal/solar_cooker/documents/reflectivematerialsreport.pdf, ceramic coating over polished aluminum to prevent oxidation.

Clear acrylic coating over polished aluminum sheet to prevent oxidation. http://www.instructables.com/id/how-to-make-your-own-blank-clear-acrylic-paint-med/?ALLSTEPS

http://www.fsec.ucf.edu/en/research/solarthermal/solar_cooker/documents/reflectivematerialsreport.pdf ".. 2.5 mil polyester film with a specular metallized layer on front surface treated with an acrylic coating to suitable for protecting metallized layer from oxidation/corrosion and polyester film from ultra violet....."

Polish aluminum sheet and then cover with polycarbonate. Print sheet of polycarbonate with 3d printers. Fit sheet over aluminum sheet in presence of nitrogen http://www.airproducts.com/e-newsletters/gas-metalinteractions/winter2006/EffectsofNitrogenonAluminumExtrusion.pdf. Fill chamber with nitrogen gas.

Links
http://solarcooking.wikia.com/wiki/Reflective_material Looking for inexpensive, recycled reflective material for solar cookers? Here’s a tip from the SunStove Organization of South Africa: "Lithograph printing plates are available in every country at the government printing office, the local printer or the local newspaper. Used printing plates are sold as scrap." This scrap may be sold for the equivalent of US $1.25 per kilogram. Before using the plates in solar cookers, clean with paint thinner and water.

https://en.wikipedia.org/wiki/Heliostat Links to reflective material.

https://www.youtube.com/watch?v=wiHs_3DFfEs Mylar reflective for solar ovens.

http://www.fsec.ucf.edu/en/research/solarthermal/solar_cooker/documents/reflectivematerialsreport.pdf FSEC Comments:  Pure (99%+) aluminum develops a protective coating of aluminum oxide immediately on exposure to air (oxygen). This actually protects the aluminum from further oxidation by oxygen in the air (unlike iron which will continue to oxidize until there is nothing left but iron oxide – rust.) However, pure aluminum has poor structural properties. Therefore, aluminum that is used for anything structural is actually an alloy of aluminum. These alloys can be “polished” however, without some kind of protection (anodized or coated), they are subject to fairly rapid atmospheric corrosion. One will often see white chalky pitting on unprotected structural aluminum products. Pure aluminum is also subject to severe corrosion from strong acids and bases like cement “lime” products will destroy it in very short order. Thus aluminum products that are expected to last for extended periods of time must be coated with a protective coating.

http://solarenergyengineering.asmedigitalcollection.asme.org/article.aspx?articleid=1457288

http://cleardomesolar.com/solareflexpanels.html Manufacturer states that in comparison heat tests, their reflective material continuously beat any other material such as aluminum foil, glass mirrors, Mylar, etc. by 18-20% in heat generation. This is stated as being due to the excellent IR reflection properties that the other surfaces do not seem to reflect as well. The manufacturer also states that since their material reflects most of the IR, and because it has a metallic surface and not a plastic surface, there is little or no effect from IR exposure

http://www.mirrorsheeting.com/, http://nielsen-enterprises.myshopify.com/pages/directions-to-make-a-mirror Sells Mylar sheeting 30x1m $54 = $1.8/sqrmetr