shop-talk supported in part by Fat Chance Garage
http://fatchancegarage.com
On Fri, Nov 04, 2005 at 07:03:22PM -0700, Rich Gallagher wrote:
> My research indicates that a solar air space heater may result in heating cost
> savings. I could install it on the south wall (unobstructed to the sun). We
> get a lot of sun during the winter. I'[m looking at a Cansolar SA240 Solar
> Max unit. (http://shop.altenergystore.com/itemdesc.asp?ic=CANSOLARMAX240)
>
Hi. I'll preface this with an admission that I have no experience with
this company or this solar heater.
That said here are a couple observations:
They claim they tested in October and obtained a peak output of 2.6KW to 2.8KW
but they did not say where this test was performed. It would have been more
useful if they would have also provided a total output figure in KWhr (that is,
something like this: "We ran a test from sun-up to sun-down on Oct 21, 2001 in
Someplace, USA and obtained an estimated total output of 12.3KWh").
Here is a map of the available solar energy in October assuming a south-facing
flat plate collector tilted at an angle equal to the latitude:
http://www.nrel.gov/gis/images/US_pv_october_may2004.jpg
As you can see, a solar collector will perform quite well in the southwest
but not so well in other locations and downright poorly in still other areas.
You can find the NREL's (National Renewable Energy Labratory) other solar maps
here: http://www.nrel.gov/gis/solar_maps.html
In Oct in Montana, it looks like you'll have somewhere between 4KWh - 5.5KWh
available energy per day per square meter of collector area. Looks like this
drops to between 2.5KWh - 3.5KWh per day from Nov through Jan. Keep in mind
that the SA240 appears to be mounted vertically instead of at an angle so the
available energy will be somewhat less.
So, is it worth it? Dunno.
Let's assume you'll use this heater from October through March and over that
time
you're able to average 9-10KWh output per day (the collector is about 2.6 square
meters). 180 days at 9.5KWh/day = 1710 KWh/year or 5.84 million BTU/year
(58.4 therms/year).
If electricity costs $0.10/KWh it would save around $171/year compared to a
electric heater. The solar heater would pay for itself after around 10 years.
For gas, let's assume natural gas goes up to $1.40/therm (100k BTU) and stays
there. Then you're looking at saving around $82/year. The solar heater would
pay for itself after around 20 years.
Jimmie
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