# Solar System Basics

Posted by Saki on November 8, 2009, 8:18 am

Is 0.03 gpm per square foot a good number to shoot for on a MTD
collector?
Is 2-3 gallons of storage per square foot a good number to shoot for
on a MTD
collector?

Any suggestions on a source of large sheets of mylar?

Posted by Morris Dovey on November 8, 2009, 10:35 am

Saki wrote:

I have no experience with these things, but you can read about one MTD
system at

http://www.builditsolar.com/Experimental/MTD/MTD.htm

How well any of this is likely to work for you will depend on your
location and typical winter weather patterns.

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

Posted by daestrom on November 10, 2009, 1:35 am
Saki wrote:

Well, let's do some math.  If insolation is 1000 W/m^2 in full sun,
that's about 93 W/ft^2 and that in turn is about 5.28 BTU/min/ft^2.

Since a gallon of water is about 8.3 lbm and that means it takes about
8.3 BTU to raise water one degF, a flow of 0.03 gpm per square foot with
5.28 BTU/min/ft^2 would mean...

deltaT = (5.28 BTU/min/ft^2) / (8.33 lbm/gal * 0.03 gal/min-ft^2 * 1
BTU/lbm-degF)
deltaT = 21 degF

That doesn't seem too bad.  Of course this assumes no losses to
evaporation or other ambient losses, so I expect you'll really get half
that or less.

If you get 5 hours of full sun (300 minutes), at 50% collection that
would be about 793 BTU.  That would raise 3 gallons of water (25 lbm)
about 31 degrees F in one day (assuming no standby losses).

daestrom