Re: Hemispherical Solar Concentrator?

From: Richard Conner <rkc_at_pacbell.net_at_hypermail.org>
Date: Sat, 12 Jun 2004 05:06:16 -0000

--- 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?

Hmm... interesting ideas... how about a little more details -
I was thinking I'd use a half an actual sphere so that focus should be
at a constant point within the device without needing to adjust for
sun tracking as well as being tolerant of constant minor movement of
the hemisphere. What I am actually interested in investigating is
feasability of an *extremely* cheap solar pool heater. Hemispherical
concentrator heating copper element transferring the heat into the
water within the tube causing thermosyphoning to draw water up from a
few feet down, and spilling over sides of hemisphere. If they could
be made to work, and were cheap enough, it might be possible to drop
several in a pool -- or I could just be smoking crack. :-)
Received on 2004-06-11 22:06:25