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Re: Sunlight

On Thu, 22 Oct 1998 12:56:18 -0700 Dave Gomberg wrote:

>At the risk of going high tech on you Ken, look into a heliostat.  It is
>basically a mirror on a 1 rpd (revolution per day) motor.  Since it follow
>the sun across the sky, and since it reflects the sun in a line due south
>and parallel to the ground, the beam is always in the same place.  Now you
>can move it where you want with more fixed mirrors.  You can get very high
>quality mirrors in K-mart or wherever.   They are made from PPG float
>and my last one cost $1 for 1x4'.  By investing $50 in a motor and drive
>and $50 in a mount and $50 in mirrors you would have something better that
>any commercial device and at a lower cost (and simpler).

I think your suggestion is very appropriate for a room with a north facing
roof.  The heliostat could direct the light toward the south and into a
facing skylight with appropriate reflectors.  It might be possible to locate
heliostat at ground level in an inconspicuous place.  There is a company in
Albuquerque called Zome Works which produces a passive heliostat.  The sun
heats two chambers containing a refrigerant which are located on either side
of the pivot point.  Heating the refrigerant moves it from one side to the
other.  The unit balances when it is aligned with the sun. These units are
designed to track the sun for use with solar panels.

Another option is to make a static heliostat.  Basically this is an array of
mirrors with individual mirrors aligned with the sun at different positions
in the
sky.  The mirrors focus the sun at one location.  From there, the light can
redirected as desired.

I think it is likely that all this solar technology might not be required at
all.  It
seems that the greatest resistance to using sunlight has to do with
instability in the tank due to excess light.  I don't see any reason why
this can not be
controlled or as Jeff Dietsch said, throttled.  It would be a simple mater
to control venetian blinds with a stepper motor and a simple controller
which takes light measurements.  For the non do-it-yourself, there are
commercially available products for use with conventional skylights that do
exactly this.

Lets imagine for a minute that we used one of the light gathering techniques
from above.  Assume we have enough excess light on most days that we would
have to reduce it to meet our needs.  Now we could experiment with
simulating seasonal changes which may bring us a step closer to nature.
This of course, is not the only motivation for doing this; I believe the
term cost savings could be significant.

I think this concept could serve a lot of hobbyists, low-tech and hi-tech
alike.  I would like to work with some of you on developing this concept.

Any takers?

I want to clarify, that any ideas or methods we come up with are in the
public domain.  There is already enough overpriced gadgets in the aquarium
hobby, lighting systems included!

Ken Potter

kpotter at flash_net

Albuquerque, NM