Debbie's got some good ideas there. Our hydronic
heating system has copper tubing and even that slitted
black foam insulation material you push on to keep
the heat in. We've also done her papier-mache
balloon trick to make concave spherical surfaces
and it works pretty well. Note that a spherical
surface very closely approximates a parabola for
small off-axis angles, particularly if the focus
is large piece of copper.
I believe a parabolic surface can actually be formed
by starting with a crude near-parabolic bowl, filling
it part way with a hardening polymer, then spinning
it 'till it dries. Then you have to mirror-coat it.
But it's probably something more easily purchased from
a stock house like Edmund Scientific, which is now:
http://www.edsci.com
They also sell fresnel lenses in various sizes, which
also concentrate solar energy quite well and are
damned more fun to play with, like at Cassini parties,
where you can watch small children sear the flesh of
their siblings. JT might use them for lighting cigars,
probably even by moonlight. :)
The more efficient large solar concentrator arrays are
actually rows of parabolic troughs, with motorized sun
tracking elevation control and blackened pipes running
along the focus line. JT might use these for lighting
a bunch of cigars at once for *his* next party..
Then there's always google.
dc
Georgie Hinklemyer wrote:
> P.S. Keep the copper tubing short, to minimize heat loss.
>
> --- In OliveStarlightOrchestra_at_yahoogroups.com, "Georgie Hinklemyer"
> <samoolives_at_y...> wrote:
>
>>Mylar works great as a surface coating. Or any other silvered
>>sheeting. Tinfoil is lots cheaper and easier, but collects wrinkles
>>like you wouldn't believe.
>>Really small egg shape: use a plastic lady's "L'Eggs" Egg. They
>
> make
>
>>nice parabolic surfaces.
>>Medium-sized egg shape: try blowing up a balloon, tape the knot down
>>VERY flat, and papier-mache it. Use the knot end as the bottom of
>
> the
>
>>mirror. Punching-bag balloons get to be about 2 feet across, if
>>you're lucky.
>>Smaller egg shape, already mirrored: a mylar balloon. Papier-mache
>
> it
>
>>and the inside's already silvered. Might not be a steep enough
>>parabola, though.
>>Do you know how to calculate the focus of a parabola?
>>--Debbie
>>
>--- In OliveStarlightOrchestra_at_yahoogroups.com, "Richard Conner"
>> <rkc_at_p...> wrote:
>
>>> > I'm looking into experimenting creating a sort of
>>> > hemispherical solar
>>> > concentrator. Perhaps some of you out there may have some
>>> words of
>>> > wisdom or ideas for me...
>>> >
>>> > Looking something like:
>>> >
>>> > | o |
>>> > \ |=/=== b
>>> > -|-
>>> > |
>>> > a
>>> > 1. Lightweight plastic(?) hemisphere - possibly some sort
>>> > of sphere
>>> > that might be cut in half.
>>> > 2. Some form of reflective coating?
>>> > 3. Small copper ball (o) attached to copper tube/wire (o-a)
>>> > dropping thru hemisphere.
>>> > 4. Clear plastic(?) tubing(?) (a-o-b)
>>> >
>>> > Experiment is to heat water in tube (o-a) to cause thermosyphoning
>>> > from cooler water below (a) to be heated and flow out thru (b).
>>> >
>>> > Any suggestions for parts/information/etc much appreciated.
>>> >
>>> > -Richard
Received on 2004-06-11 10:58:09