# Solar in rainy Washington



## Pink_Carnation (Apr 21, 2006)

I was wondering if anyone has done much with solar in Western Washington and how well does it work with all the rain we get in the winter.


Pink


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## Jim-mi (May 15, 2002)

Thats a good question for someone at the Home Power crew.
A couple of them are in that area.
[email protected]

........www.homepower.com


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## mightybooboo (Feb 10, 2004)

Ive read articles of successful solar power in the NorthEAST,FWIW.Unsure of the Pacific NorthWEST.
Read of using solar evacuated tube hot water systems in rainy,overcast climates that was surprisingly successful.

Solar Gary may have some thoughts on this,check his site?

http://www.builditsolar.com

BooBoo


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## SolarGary (Sep 8, 2005)

mightybooboo said:


> Ive read articles of successful solar power in the NorthEAST,FWIW.Unsure of the Pacific NorthWEST.
> Read of using solar evacuated tube hot water systems in rainy,overcast climates that was surprisingly successful.
> 
> Solar Gary may have some thoughts on this,check his site?
> ...


Hi,

You might take a look at the NREL RedBook site:
http://rredc.nrel.gov/solar/pubs/redbook/

They give fairly detailed tables for solar radiation on a collector for many cities. You can download the one for Washington (which has Seattle), and for some other areas to get a comparison. For example Denver is an excellent solar location, and Great Falls, MT (near me) is a kind of middle of the road solar location.
Just a quick visual inspection says that Seattle in mid-winter is not so good. But, it looks like the heating season extends roughly from Oct to April, and the sun gets better in the spring and fall. It looks fine in the summer. 
So, solar hot water would be good, and you could get some benefit from a solar space heting system with most of the benefit in fall and spring. Having lived in Seattle for 30 years, I should have a better feel for this 

--

I've heard the same thing about evac tube collectors doing well in cloudy weather, but have not seen much to back this assertion up -- I'm a bit skeptical, especially given the high price of evac tubes. The SRCC ratings site actually has ratings for full sun, part sun, and cloudy for both conventional and evac tubes -- you could compare them. 
http://www.solar-rating.org/RATINGS/RATINGS.HTM

Gary
www.BuildItSolar.com


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## SolarGary (Sep 8, 2005)

SolarGary said:


> Hi,
> ...
> I've heard the same thing about evac tube collectors doing well in cloudy weather, but have not seen much to back this assertion up -- I'm a bit skeptical, especially given the high price of evac tubes. The SRCC ratings site actually has ratings for full sun, part sun, and cloudy for both conventional and evac tubes -- you could compare them.
> http://www.solar-rating.org/RATINGS/RATINGS.HTM
> ...




Hi again,

Just taking a look at the SRCC site, and comparing a Heliodyne Gobi 408 flat plate collector to an Apricus evac tube collector you get:

These are output in BTU per hr- sqft

Flat Plate: Full sun 713, Part Cldy 403, Cloudy 120 BTU/hr-sqft
EvacTube: Full Sun 686, Part Cldy 480, Cloudy 274


So, the Evac tube does does better in cloudy, while the flat plate does better in sunny. You would have to look at the prices to see if the evac tube actually produces enough extra output to justify the extra bucks. The Apricus was the best of the evac tubes I could find at a quick look -- the Thermomax evac tubes actually did worse than the Heliodyne flat plate at all sun levels -- ouch!

-----

I'm getting back to working on my Solar Shed project, and while I was thinking about ordering premade absorber plates, and building in the rest of the collector as part of the shed wall, I'm now wondering about a scheme where water is trickled down between two sheets of EPDM rubber sheeting with a layer of shade cloth between the two sheets to make for uniform water flow.
The glazing would be twin-wall polycarbnate (which I have already purchased). The back support for the collector would be the shed 2X6 studs (spaced at 4 ft) with a sheet of 2 inch polyiso insulation between each set of studs.

I think the EPDM collector would only end up running about a net $2.70 per sqft (this is taking credit for not having to use siding under the collector). This compares to $5 to $8 just for the absorber plate for the other solution, or $25 and up per sqft for commercial collectors -- even more for evac tubes.
This might pay off well even in Seattle 

I don't see why the EPDM with the twinwall polycarbonate would not perform in the same general area as a commercial flat plate collector?
EPDM has a long life and can take exposure to temps up to 180F -- I think I can work out a scheme to keep temps lower than this (which is helped by the steep angle I have them mounted at).

The Solar Shed: http://www.builditsolar.com/Experimental/InWorkshop/SolarShed/solarshed.htm

Gary




Gary


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## Jim-mi (May 15, 2002)

Gary I gotta add a thought about collectors for folks to consider.
I am in a *snow belt* area, and I am very lerry to use evac tube collectors here. After one of our heavy snow falls I can just imagine trying to clean the snow off the evac tubes.......no thanks.
I have a soft bristle brush on a 8' handle for cleaning snow off my PV racks.....and that would be just fine for a flat plate collector..

bottom line; Folks think about how much snow you get before deciding evac or flat plate.


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## mightybooboo (Feb 10, 2004)

Excellent link Gary,thank you!

BooBoo


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