Mounting solar thermal panels on the roof in high wind environment

[ChuckD]

Hi all,
First post here. Thanks to all who provide and support this forum, lots of great information.

We're installing a solar thermal system on our roof to supplement a new geothermal system, and to provide DHW. We're committed to an installer, who we like, who at first was going to install some Schuco panels flat. I've talked him out of this and we're going to install them on ezFlatroof racks, also from Schuco. So here's some vitals:

We're at about 43 degrees N lat.
The roof is sloped directly south and has a 4.5/12 pitch (roughly 20 degrees).
The lowest solar max. altitude occurs around December 21 and is roughly 23 degrees.

So my reasoning for not flat mounting them is that at the time of year when I need them the most, the best sun angle on them would be roughly 45 degrees, which means roughly half the available energy would be harvested. This seems elemental to me but I'll take a sanity check on that theory. There's no dispute involved, and he's very willing to mount them on the racks for an acceptably small extra charge.

The issue though is that we're pretty exposed at 1000' elevation and in a fairly high wind area, high enough that I can seriously consider a wind turbine at some point. But the other side of that is we get gusts on occasion that really rattle our 2x6 walled house. My installer is aware of this too and it was one of his reasons cited for flat mounting.

So, I don't think we're the first to have this scenario, and I was hoping someone out there might offer some practical advise for how these should be mounted. My first thought is there should be some kind of fairing involved to divert the wind. It's pretty predictable from the WNW, but we do occasionally get it from other angles. I'm also thinking the racks should get extra lags, but what good would that be if the panels are in the next field over?

Also, if anyone can shed some more light on this presentation I'd like to hear it:

"Analysis of Wind Forces on Roof-Top Solar Panel"

http://adsabs.harvard.edu/abs/2011APS..MARV31015P

This would've been interesting to hear, especially as they apparently allude to solutions at the end:

'The present study concluded to reduce the strong wind uplift by designing a guide plate or a deflector before the panel. '
Details please!

Thanks for reading

Chuck

[Mike90250]

I'd be inclined to accept the reduced output/harvest, for a secure mounting. Didn't read the article yet.

Do you have snow to deal with in your area ? I'm thinking of what would block /trap snow too.

[s.xavier]

Chuck the first thing you really have to do is access what you want your home to look like. Tackling wind with solar is not impossible but you really need to consider how you want your home to look at the end of the day. Talk to your significant other about it as well.

What is awesome about solar panels and flat installation is the sleek look it provides. You can have a very sophisticated and sleek system under windy conditions but understand that it will add to the final budget. My two cents:

1) talk to significant other what is acceptable
2) understand your budget

If you have flexibility at that point, feel free to shout what the installer recommends.

[ChuckD]

We're partners on this project and she's on board with this. This is not a man-toy for me to fiddle with on the weekends. We want function over style. Not that we don't care how it looks but we're not doing this for looks. FWIW, this roof is on the rear of the house and we're several hundred feet off the road.

And I disagree that the 'first thing I need to do is access (sic) what I want my home to look like'. The first thing I want to do is assess how to get the most heat energy from the sun and into my home. Then I need to determine how to do this without it looking like some kind of monstrocity and blowing the budget. Having studied architecture for several years, I'm pretty sensitive to how it'll look. But I very much disagree that should be priority number one.

And I can't accept only 1/2 of the system's capabilities because we can't come up with a creative way to deal with the wind. We're in Upstate NY. Heat from the sun is already pretty skimpy. Do I have to compromise my system even more? Snow is also a concern, even moreso if the panels lay at the roof's 20 degree slope and allow the snow to collect on them. I can't see myself climbing up there after every snowfall to clear them off. I can see myself implementing some solution to avoid build-up in the first place.

I'm just putting this out there to hear if anyone else has dealt with this. Thanks.

[Mike90250]

I'll direct you to the Solar Shed:

http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/solarshed.htm

The article there may help spark some ideas.

I'm thinking an outbuilding, with the roof properly oriented, to mount the panels to.

[ChuckD]

Now that's a blast from the past. I'd bookmarked this site back around when he made his previous entry in 2009 when I was first kicking this thing around in my head. Thanks for the reminder! Lots of good stuff there.

I don't see building an outbuilding for this happening right now though, that would blow the budget, and we are aesthetically sensitive enough that even my awsome carpentry skills would probably not pass the test.

Thanks again.

I'll direct you to the Solar Shed:

http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/solarshed.htm

The article there may help spark some ideas.

I'm thinking an outbuilding, with the roof properly oriented, to mount the panels to.

[s.xavier]

how you prioritize it is strictly up to you, just my two cents. I'm not saying you but a lot of people fail to assess the look, it is just a friendly reminder.

It is good (and makes sense) that you're utilizing your carpentry skills and architecture talents so the project shouldn't be a problem. can you shoot over a picture so all of us can dabble on design elements?

[ChuckD]

Sorry for the strident tone, but i hate to hear tales of woe of lackluster performance when the first concern was 'how it looks'.

Anyhow, I'll take up your offer and post a pic this weekend. Mmeantime, be advised my "awesome carpentry skillls" was intended with full tongue-in-cheek. ; )

how you prioritize it is strictly up to you, just my two cents. I'm not saying you but a lot of people fail to assess the look, it is just a friendly reminder.

It is good (and makes sense) that you're utilizing your carpentry skills and architecture talents so the project shouldn't be a problem. can you shoot over a picture so all of us can dabble on design elements?

[Naptown]

Two words
Structural Engineer
I would not do this without someone certifying the construction will withstand the implied loads.

[Sunking]

certifying the construction

Certify Smertify, we don't need no stinking certification. That's for Gringo sissies.

[Naptown]

Certify Smertify, we don't need no stinking certification. That's for Gringo sissies.

You lookin t get banned for touting unsafe practices? :>)

[ChuckD]

Well, as it happens, the installer's wife is one, so hopefully we're covered there.

One thing I'd like to be able to do is orient these in "landscape" configuration, as opposed to "portrait" (I think I've seen those terms used that way). Is this an option with the Schucos? At least it would lower the profile and we've got plenty of unshaded roof area for it.

[Naptown]

There are Schuco models that mount either vertically or horizontially depending on the model you would want an H model.

[s.xavier]

people just need to be smart about what it is they are doing to their home... but then again you should also consider your neighbors and such.. Safety, safety, safety and a lot of common sense

[mtmtntop]

i live about 9 miles from the continental divide at about 3900 feet. we can get strong chinook winds, and have had them since i have put up a 75 tube array. my array stands at 65 degrees, my latitude is 46 N. My array does not have a back to it, ie there is nothing behind the array like a reflector, etc. It sits east west, for a southern exposure. My friend built me a really nice rack that replaces the usual legs that come with the arrays. The array angle is adjustable, with square stock steel tubing sliding into each other for the legs. However, as far as anchoring to the roof, here is what i did. FIrst, I built this room from the ground up and had my trusses designed for 50 lbs/sq ft. Then , the rack was built with 2" steel strap iron running the length of the array basically at the "top" and "bottom" as they touch the roof. After drilling pilot holes, I installed1/2" lag bolts every foot either into the rafter itself, or in between , into a 2x4 that straddled 2 rafters in the attic. I installed these with an electric impact gun (think car repair) and it was a breeze. I know these have withstood 60 mph gusts and although you can hear the wind howling through the tubes, it has never moved, even standing up at 65 degrees. Just some food for thought