re: dirigible wind turbines SOLAR.KnowledgePublications.com

re: dirigible wind turbines
2 dec 1997
an update on available components: i haven't found a nice slip ring assembly
yet. maybe the large structure should rotate on a horizontal axis, with 2
single-pole slip rings, with a hole in one to admit rainwater for hydrogen
electrolysis. it might be a double tetrahedron, like a double-delta darrieus
turbine turned on its side, or a double 4-sided pyramid, with a bearing or
swivel joint and insulated tether cable at each end, and 2 anchor points on
the ground, say 20' apart. this would make it less likely to fly away.

dave norris at sky signs balloons ltd of valley forge, pa (610) 933-6952
sells advertising balloons made from a 0.0025" polyurethane/vinyl material.
they are said to have a long lifetime. their 13' diameter x 17.5' tall hot-
air-balloon-shaped balloon costs $1,775, with harnesses, fill tube, repair
kit, and so on. it weighs 22 pounds, and can lift 70 pounds when filled with
1265 ft^3 of helium. they don't rent their helium balloons, unlike their
cold-air balloons, since they tend to fly away. they weren't very sure about
the helium leak rate, but it sounds like something between 1% per day and
1% per week. they come in red, yellow, white, blue and orange. sewn-in
stripes raise the price to $2,100.

herbach and rademan at (800) 848-8001 sells 8' helium weather balloons
with 17 pounds of lift for $16.95, in red and white. edmund scientific
at (609) 573-6250 sells 8' weather balloons for $17.95 with 18 pounds of
lift when filled with 268 ft^3 of helium. yesterday, an unladen tethered
8' balloon approached a 30 degree elevation in a 17 mph wind. edmund also
sell a 16' weather balloon for $92.50 which has 140 lb of lift when filled
with 2144 ft^3 of helium. none of these are very durable, but they might
be useful components if the larger structure were covered with typar for
sun and wind protection.

a double tetra structure might look like this, from one bearing end:

            w    <-- wind
              .                  it might contain 6 or 7 
            .   .                8' weather balloons with a
          .   b   .              net lift of 108-126 pounds.
        .           .   w    
      .    b  b   b   .
    w   .       \   .            24v air-303s cost about $500 each,
          .   b   .              weigh 13 pounds each, and make up to
     ~16'   .   .   \            375 watts with a 45" propellor. 
              .       \
                w <-- rotation
                          \      
                            \    tether.

it might rotate at about 6 rpm in a 5 mph wind.

nick