[Greenbuilding] is it ever sensible to use PV to heat water?

Reuben Deumling 9watts at gmail.com
Tue Mar 20 18:54:04 CDT 2012


On Tue, Mar 20, 2012 at 4:42 PM, <larencorie at axilar.net> wrote:

>
>
> > From: "Reuben Deumling" <9watts at gmail.com>
>
> > Neither solar PV or solar thermal contribute much
> > of anything in the winter here (cloudy PNW)
>
> Hi Reuben;
>
>  Though the bigger issue (than overcast) is your
> relatively short heating season, you can still get
> good payback from site built wall mounted Solar air
> heaters, which could deliver about 100,000BTU/sqft
> per heating season.  At around $3/sqft material
> costs, the payback would be fast.
>

Laren,
do you know why your computer always delivers a high ratio of carriage
returns to words typed? Very hard to read, at least on my computer.

I had to chuckle when you said 'relatively short heating season.' Even with
pretty careful insulation and a reduction in firewood demand to 1.5 cords,
I still heat from Oct. 15 to May 15: seven months. I'd expect San Diego to
have a relatively short heating season, but am not sure I'd agree with our
~4500 HDD/yr as short.

Solar air heater sounds good, but perhaps you didn't know that Portland get
just about the least solar insolation in December and January of anywhere
in the US (except the Olympic Peninsula and parts of Northern Minnesota). I
got these figures from NREL's website. That is why solar thermal systems
here don't do squat in the middle of our winter. Most folks of course have
fossil fuel backup systems for the solar DHW and so aren't aware of the
shortcomings of this setup.

Or maybe you could say a few more words about this fast payback solar air
heater?

Reuben
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