CURRENT PROJECTS - A parabolic trough solar collector you can build
I am working on a solar heater, a parabolic solar tracking concentrator of my own design. Here is a picture of the prototype.
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. High Definition. You can see the HD button in the lower right after it starts playing and to the right of that, you can display it full screen, if you have enough bandwidth.
Free heat from the sun - Provides about 800 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 for each 8 foot section.
Simple - Flexible plastic mirrors are held in a plywood and
steel frame which pivots around a horizontal collector pipe. The
parabolic shape of the collector focuses the sun's heat onto the
collector heating the filtered water which follows through the
collector. 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
tracks the sun all day.
Efficient - it uses almost no power itself. It does not
"hunt" when cloud cover obscures the sun. Reflectors are balanced
and hang from the collector tubes so require very little force to rotate them.
Safe - Although it concentrates the heat of the sun about 20
times, 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 though!
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 with a simple electronic circuit that you can buy or make for
about US$30.00.
The heat produced can be used for pool or spa heating
or for bio-diesel production.
My fifth prototype is pictured. The final model
will incorporate lessons learned.
Plans will be available
I am currently working on a detailled set of plans which should be available for purchase in the SOON at modest cost, probably in the range of $50. You can let me know you are
interested in being notified that the plans are available by emailing to: Solar Parabola Plans
RIBS
(click on any image to enlarge) - The 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 have used both MDF wood (medium density fiberboard) or marine plywood with good results. 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 with a router and a template to get a good
clean edge. Rough blank
shapes are cut to a traced pencil line with a jig saw and closer with a
band saw and finally routed along a template made from one of the early
ribs.
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 but very strong and light.
The plans will show you in detail how to make high quality ribs and will include a pattern for you to use to make your own template
for marking, bandsawing and routing the ribs.
With the methods described, it will take you about three and a half
total hours to each finished rib primed with two coats of marine epoxy
primer.
Each eight foot section can provide you with
the equivalent heating of about 800 watts. Each eight foot
section will cost you about $150. You build as many as you want to cover
your requirements.
Videos showing each step of the process will be included.
The reflector 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 steel channel cut from furring strip from home center box 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.
