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re: building solar collector
2 jun 2001
szymczyk wrote:
>i'm interesting for instruction building solar colector 5 kw.
vous parlez francais, peut-etre?
a 5 kw heat collector requires 5/0.8 = 6.25 m^2 or 67 ft^2 of solar
aperture with 1 kw/m^2 of peak sun and an 80% collection efficiency.
how about a 2'x8' (2 foot by 8 foot) solar trough under an 8'x8'x8'
tall linear parabolic reflector with 64 ft^2 of aperture?
to make the reflector, saw a 1.5"x3/4"x12' (1.5 inch by 0.75 inch by
12 foot) strip off one side of each of 3 wood 12' 2x4s, (12'x1.5"x3.5"
boards) and saw 2 1.5"x3/4"x8' strips off 2 8' 2x4s. make about 10
partial cuts with a saw across the short faces of the 12' 2x4s to
approximate the parabola y^2=16x from x = 0 to 12', leaving 3/4" of
wood uncut. bend the 12' 2x4s to shape with a cable and pulley until the
saw cuts close (use a temporary extension arm at x = 0), and screw a
thin strip of steel to the cut sides to hold them in shape. bend the
strip 90 degrees around the wood and screw it to the end at x = 0.
"glue" 96 ft^2 of 0.001" thick reflective mylar (polyester) film to
an 8'x12' piece of 0.006" thick uv-stabilized greenhouse polyethylene
film with a thin layer of grease and a paint roller. staple one 8' edge
of the films to the 1.5" side of an 8' 2x4. screw on an 8'x3/4" strip
to hold the film in place. do the same with the other 8' edge.
stretch the films over the 12' 2x4 bows on 4' centers, with the mylar
on the inside. screw the 2 8' 2x4s flat and perpendicular to the 1.5"
uncut sides of the 12' 2x4s near x = 0 and 12, with the films between
the 8' and 12' 2x4s, and screw the 12'x3/4" strips back on the 12' 2x4s
to hold the 12' edges of the films in place.
how's that so far?
nick
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