Solar Path Question

Thanks for the illustration. The links made for hours of interesting
reading, too.

There was a reference in one of the links to solar chemistry.
They're writing about reducing CaCO2 to CaO + CO. Using the CaO for
cement. That'll be useful to me in my studies in a week or so, when
I start looking at building materials.

So, back to the solar question. Is there any geometry for the
heliostats that can make use of ALL of the mirrors during the lunar
day? How would a field be laid out so that the mirrors between the
tower and the sun can be used?

Am I correct in understanding that heliostat fields that completely
encircle the tower can make use of all of their mirrors when the sun
is 45 degrees or greater above the horizon?

Nobody seems to be addressing my queston of solar path at the lunar
equator. Does that create any unique problems? I'm feeling that I'm
conceptualizing something incorrectly here, namely that a sufficient
angle can be created between the heliostat mirrors and the tower.
Does the equator create any problems in creating the necessary
angles?

> Greetings,
>
> I just posted a gif file
with a
> 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