Starting from a blank slate: roof access?

System · May 2009

We're building a new house, with a great southern exposure for about 800 sf of roof in the main roof, and another 200 sf of shed roof on the south side of the house. So, solar, here we come, I'm thinking-- grid-tied PV on the main roof, some solar thermal on the lower roofs ...

But, as we get into it, pragmatic things, such as designing in roof access for cleaning, rise up as issues. This is a 3 story house, with the 3rd story as a "half-story under the eaves of the A-frame construction.

OK-- skylight near the peak and centrally located. Arrange the panels around that hatch within reach of window cleaning tools. Maybe two skylights if we get ambitious about the array. Fair enough.

But then a source of water for the hose would be nice, in a location that wouldn't drip all over the interior. Hmmmm ...

I'm looking for ideas from either experience or imagination.

We are dedicating a decent portion of the under-eaves space for mechanical systems, but had favored putting that on the north side, where all the bathrooms line up in a stack.

I've gone so far as to wonder whether my wife could spray water up on the roof from the ground, while I wield the mop from a skylight. Can a pressure washer shoot water up 2-3 stories? Or maybe I can lean out of the bathroom window on the north face of the roof and shoot the water back over the peak. See where I'm going with this? I doubt it can get much wackier, so please brainstorm away.

lorelec · May 2009

Re: Starting from a blank slate: roof access?

Unless you never get any rain (or you live somewhere with a lot of air pollution), I wouldn't think PV cleaning would take up much of your time. Mine are pole-mounted on the ground, mostly for ease of snow removal in the winter. But I've never had to hose them down, even in the summer when we go for months with very little rain.

If you're able (and heights and/or roof pitch don't deter you), climbing up there via ladder with a hose a couple times a year would probably be all you'd need. Pressure washers can shoot a distance, but careless use with one could also damage your PVs.

Marc

niel · May 2009

Re: Starting from a blank slate: roof access?

the angle that allows snow to run off will aid in getting rid of any soot too when it rains. i would imagine that your arrangement will have a fixed angle being it's so difficult to access and that will be based from your latitude. boston is about 42 degrees and many add another 15 degrees for 2 reasons. 1> the winter harvest of power is more difficult than the summer. 2> the sun is at lower angles to the horizon before and after solar noon. the total angle will be 57 degrees, with 90 degrees being vertical and 0 degrees being flat for reference.

mike95490 · May 2009

Re: Starting from a blank slate: roof access?

I'd tried using a mini-firehose nozzle (a "sweeper", just a simple taper for a small, high power stream) and discovered the flow breaks up at the 1st floor level. I could only get mist up to the 2nd floor where my panels were. A pressure washer has high pressure right at the orifice, but if you get 5 feet away, you have nothing. The blast won't even make it to the 1st floor. You are stuck going up with a garden hose, and a spot free car rinse (DI filter cartridge).

n3qik · May 2009

Re: Starting from a blank slate: roof access?

I noticed very little gain when I washed the panels. I biggest gain was when it snowed, then I would clean them, but summer, let mother nature do her thing.

BB. · May 2009

Re: Starting from a blank slate: roof access?

I could not tell the difference after I washed my panels either... Which was surprising as we have skylights right next to the panels and they are quite spotted and streaked with dirt after a long time without washing.

-Bill

dwh · May 2009

Re: Starting from a blank slate: roof access?

http://www.aclindustries.com/construction/cage-ladders/roof-access-ladder.html

http://www.goodyearep.com/productsdetail.aspx?id=14478

http://www.properautocare.com/bodebrkit.html

http://www.discountsafetygear.com/fallprotection.html

http://www.heinekeninternational.com/homepage.aspx

icarus · May 2009

Re: Starting from a blank slate: roof access?

I wouldn't worry a bit about washing the panels. I would on the other hand consider ALL aspects of the house design to maximize efficiency throughout, for PV solar, passive and active space and water heat, minimize heat loss in winter, heat gain in summer etc.

Too many people realize too late,,,,"Oh, I could of had a V-8!

Tony

System2 · May 2009

Re: Starting from a blank slate: roof access?

Thanks all for insights and safety equipment suggestions. We are really concentrating on the efficiency of the structure, so much so that the solar aspects really are an afterthought.

Another post somewhere else commented that cleaning panels is lot like window washing--so hire a window washing outfit. They've got the right tools and are used to working on ladders, etc.

Perhaps having the panels and windows all cleaned professionally a once or twice a year would suffice.

niel · May 2009

Re: Starting from a blank slate: roof access?

you could try that and see if any improvement is actually had when it's done. let us know the outcome and try this after about a year after the install.

BB. · May 2009

Re: Starting from a blank slate: roof access?

To be honest--you will probably pay more for the window washing service than you will ever recoup by washing.

The only time I wash is because we have leaves that sometimes form a dark "dried tea" that looks like "burned" panels... I wash with soap and water and the dark edges go away.

-Bill

Starting from a blank slate: roof access?

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