Build a tracking parabolic trough solar heater


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I have built a parabolic solar tracking concentrator of my own design. These are pictures of the working prototype.

Read about high-temperature test results.

Please read this review

Time-lapse videos of the system in operation at:
youtube.com/user/georgeplhak

Comments from the readers of this project page and the blog:
ffwdm.com/solar/comments.htm

Frequently Asked Questions (FAQ):
ffwdm.com/solar/FAQ.htm

Bill Of Materials is here (original version) and here (gen2 version) (PDF) including part costs. These lists gives the page number in the book where each part is discussed in detail including methods of fabrication, sources of supply and any alternatives that are suggested. You supply the labor or you can have the parts made for you locally.

Parts cost per 8 foot section C$150-200 (Canadian dollars)
Parts cost of the motor drive C$235-250 (only one required)
Parts cost of the solar sensor and housing C$60-70 (one required)

Video below: Tracking the sun over a full day. It was mostly sunny and windy with clouds racing overhead.You can see that the tracker does a good job staying with the sun even when it is obscured (the dark flashes). I believe that the tracking sensor follows the bright edges of the clouds when it can't "see" the sun, so this is why it wanders a bit under these conditions. With a clear sky, it stays firmly locked on the sun. Time lapse, one pic every 60 seconds.

Free heat from the sun - Provides about 1000 watts of heat per section. Build as many sections as you need. Used here in a summer configuration to heat a swimming pool. I'll show how you can build it yourself inexpensively with local building materials and simple hand tools. Costs about $150-200 for each 8 foot section.

Simple - Flexible mirror sheets are held in a wood and metal frame which pivots around a horizontal collector. The parabolic shape of the collector focuses the sun's heat onto the collector heating the water which follows through. The fluid path has no moving parts, only the reflectors move to track the sun.

Smart - The collector starts tracking the sun in the east and automatically follows the sun all day.

Efficient - it uses almost no power itself. It hunts very little when cloud cover obscures the sun. Reflectors are balanced so require very little force to rotate them.

Safe - Although it concentrates the heat of the sun about 18 times, my tests have shown that failures don't lead to meltdowns or blowouts and you can't normally burn yourself on it anywhere. You do want to wear sunglasses when working on it!

Features:

  • Built with common shop tools.
  • Most materials are from local building center.
  • A few specialized parts you make yourself or buy mail order.
  • Controlled by a simple electronic circuit that you can buy or make for about US$35.00.
  • Heat produced can be used for pool or spa heating, bio-diesel production, distillation, water purification.
  • My ongoing work is at my blog.
RIBS - External ribs form the parabolic shape to the reflector sheet. There are seven ribs required for a single eight foot reflector or three ribs for a four foot reflector. I recommend MDO wood (weatherproof sign board) and suggest sources of supply (start with your local signmaking shop). The top inside curve should be accurately made and stable to within a millimeter to get the best results. With a bit of care, they can be machined easily to good tolerance and finish with a router and a template that you make.

CNC You can use a CNC router, laser or water jet to make the ribs and hangers. I give you DWG files with the new gen2 book.

Or make by hand using templates Rough blank shapes are cut with a jig saw to a pencil line traced from a template and then closer still with a band saw. The parts are then routed smooth, accurate and clean using the template made from the pattern that I supply with the plan book.

Vertical drilling is marked and center punched with the template. Horizontal holes are drilled with a hand drill and a simple jig. The big holes are bored on a small drill press. Finally, the ribs are finish sanded and painted twice to seal them for a northern climate for about 5-7 years. They are easily replaced. Very strong and light weight.

The plans show you in detail how to make high quality parts. The plan books include a full size, highly accurate pattern for you to use when making your own templates for marking, bandsawing and routing the ribs.

With the methods described, it will take you about three and a half hours for each finished part with two coats of paint.

click on pictures to enlarge

The reflector (original gen1 pictured) is strong and sturdy but light weight. It simply hangs from the collector pipe and rotates around it when pushed or pulled from below. The reflector sheet is clamped against the ribs and held in place with side channel cut from furring strip from your local home building supply store.
A single steel drive rod pushes or pulls all reflectors into position through linkage arms attached to each reflector. Rotation is -50 to +50 degrees from vertical. Solar tracking module from www.redrok.com mounted in a weatherproof enclosure directs the reflectors at the sun yet uses next to no power when it's cloudy or dark
Small DC gear motor (in the box to the right) powers drive screw linear to angular drive to provide push-pull positioning to the array. Copper collector tubes, covered with black heatshrink to improve absorption are coupled at the ends through cross pipes made from standard plumbing components.

My Books


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