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Posted by Malcolm \"Mal\" Reynolds on February 8, 2009, 9:37 am

I was actually thinking that the array might generate enough "credit" to pay
for my total useage or near enough to make it interesting

Posted by Ron Rosenfeld on February 8, 2009, 12:37 pm
On Sun, 8 Feb 2009 09:37:15 +0000 (UTC), "Malcolm \"Mal\" Reynolds"

In many places, you can also get credit for solar hot water systems.

But first you need to define, much more precisely, exactly what you want to
do with this system.

Generate hot water?  Generate electricity?  Feel good about being green?
Save money?  Increase reliability?  etc.

Then you need to determine how much you want -- kWh?  BTU?  etc.

If you are already grid-connected, you'd need a lot of subsidies, and
fairly expensive electricity, in order to make solar PV cost-effective.
Also, and again this is location dependent, professional installation may
be required (by a licensed installer) in order to qualify for the
subsidies.  You'll certainly need professional help to connect your system
to the grid (e.g. licensed electrician).

Professional installation may also be required to qualify for subsidies on
a solar hot water system.

It is generally true that even if you want to generate both electricity and
hot water from solar, it would still be more efficient to have two separate
systems -- a solar hot water system and a solar PV system, than it would to
use the solar PV system to run an electric heater.

There could be a place where differences in gas prices, electric rates,
subsidies, solar insolation, etc combine to make that not the case.

We live off-grid and don't get any subsidies.  We use wind and solar for
our electricity (with a propane fueled generator backup).  Our
furnace/boiler is also run on propane, and we have a hot water heater that
runs off the furnace.

If I were to generate our hot water by solar, there is no question that it
would be much less expensive to put in a solar hot water system, than it
would be to add enough PV to run an electric hot water heater.

http://www.infinitepower.org/calculators.htm  has some tools to allow you to
evaluate various strategies.

Posted by RED on February 8, 2009, 5:50 pm

That problem has been solved for a long time.  Just put in two ponds, one
low and one high, and use hydropower when draining the high pond into the
low pond.  This is a completely free solution, and will generate plenty of
electricity to run a water heater.

Posted by BobG on February 8, 2009, 7:02 pm
 On Feb 8, 12:50pm, R...@ix.com wrote:

How much is 'plenty' again? Lets say one 'pond' 100m across and 1m
deep.... about 300 m^3, and you have it up on a hill 10m high.
potential energy is mgh=300,000 kg x 9.8 x 10 or about 3 million
joules. If your micro hydro generator gives you 100watts, you have
enough energy for 30000 seconds... 500 min.... 8 hrs. Use it wisely.

Posted by Curly Surmudgeon on February 8, 2009, 7:51 pm
 On Sun, 08 Feb 2009 11:02:51 -0800, BobG wrote:

If that is your limit, a 10 meter rise and only one meter of water, then
true.  Few would consider such an installation but it would work.
Regards, Curly
                               Arrest Bush

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