Solar Path Question

Greetings,

I just posted a gif file
little diagram about using a mirror to focus sunlight onto a tower.

Basically it just says you point the mirror in the direction halfway
between the Sun and the tower focus. A field of mirrors on the Moon would
need to rotate (on an axis parallel to the lunar axis) at 1/2 the lunar
rotation rate. Pretty slow - only 90 degrees in two weeks. If the focus
appeared as one degree across (from the mirror), it would take about 4
hours before this flat mirror would be mis-aligned. All sorts of design
options seem possible. Maybe a robot that takes care of all motions of
mirrors on simple (dumb) joints or stands. All terrestrial designs can
apply to the Moon, except the motions are 14 times slower. Also, the
seasonal north-south motion of the Sun would be smaller, only a few degrees
instead of the 46 degrees on Earth.

I took a look around the web for info on heliostats and solar towers.
Interesting stuff out there.. thanks for reminding us to think about solar
power on the Moon, and lunar rotation geometry.

- Eric Dahlstrom

Here are a few sites I stumbled across.

RED ROCK ENERGY Solar Power Heliostat Arrays.
http://www.redrok.com/main.htm
*Lots* of links. Examples, designs, etc.

Sun Day Symposium "From Basic Research to Industry" May 1996, Israel
http://magnet.consortia.org.il/ConSolar/stepp.html
Professional conference in Israel, with a number of papers demonstrating
operating systems, economics, etc. One page from one of the papers is given
below.

High-Concentration Solar Energy Optics (A. Kribus), page 4
http://magnet.consortia.org.il/ConSolar/SunDaySymp/KRIBUS/HiConcSol4.html
There is a good figure here that shows the practical limits for solar
concentration on terrestrial systems. Why 10,000x systems are available,
but not 40,000x. Anyone care to think about what would be easier (or
harder) on the Moon?

Here is a photo of a mirror array focused on a terrestrial tower.
http://hep.uchicago.edu/~stacee/nsttf-e.gif
(Now picture the massive tower replaced with a lightweight frame sized for
0.17 g)

Pictures of the new hexagonal design for mini-heliostat arrays
http://www.multimania.com/rossen/solar/hexdesign.html
Computer models of mirrors focused on a tower - a nice set of 3 graphics
that show the geometry. (Erik Rossen, 2000, Switzerland)

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