Installing PV on Steel Shop Building Roof?

VicVic Solar Expert Posts: 3,152 ✭✭✭✭
Am starting planning on a new project. This will be new construction -- Off-Grid steel shop building with great solar exposure.

Assume that this building will be typical of steel shop type construction. Also assume that none of the steel roof is designed for point loads. Believe that the main supports for the roof system run from the lower eaves to the ridge. Normally for stick-built construction, one would usually run PV mounting rails across the roof, side-to-side in order to connect to the rafters. Customarily, the connections to the rafters would be a post that spaces these horizontal rails off the roof for thermal and water/debris clearing (ala UniRac and others).

Have any members here, designed and installed an approach for modern steel shop-type buildings (for a modest sized shop about 3000 sq ft)? How did you do this? Can spec 4:12 pitch, which is better for solar than the more standard 1:12. Might still need a bit of additional tilt on the racks.

Have been having a conversation with the company that will erect the building. This person had concerns about water leaks, and proposed Standing-Seam roof and S-5 clips. Would love to avoid both of these, due to expense and am not thrilled at relying totally on a pinch clip holding everything to the roof -- planning on 100 MPH winds. I have concerns about leaks, as well as loads that the PV will place on the roof, and perhaps debris and water clearing the roof, without human intervention and so on. Have not been a fan of ballasted racks either (am I being too picky ?).

This cannot be that unique. Off grid, or GT, seems that this must have been addressed many times on many different types of steel building construction. Yes, I DO need to find out much more about the exact construction of the candidate building. Am working on that.
Thanks for any guidance. Vic
Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.

Comments

  • solarixsolarix Solar Expert Posts: 713 ✭✭
    Re: Installing PV on Steel Shop Building Roof?

    Been there, done that. My 1200sqft steel shop is oriented N-S so used tilt racks running across the purlins going E-W. The solar mounts are TEK screwed to the purlins which are spaced every 5ft. The main trouble I had was getting the permit approved. The building manufacturer wasn't real helpful and had to get a local engr to approve the additional loading. Most of these steel building are very optimized for the design snow load and are not intended for much in addition. If you have corrugated roofing and need to run the rails across the bumps, look into what is called a saddle block mounting spacer.
  • VicVic Solar Expert Posts: 3,152 ✭✭✭✭
    Re: Installing PV on Steel Shop Building Roof?

    solarix,

    Thanks for the reply, and tips.

    OK, you used some sort of rack rails running E/W, attached every 5 feet to purlins. Were these rails mounted flat on the roof, or did they stand up? What brand and model racking did you use?

    The steel roof material for this building will not be the traditional sine-wave profile corrogated steel, but some form of flats, ribs, etc. There are many profiles, and do not know the exact one.

    Regarding the design loading of the roof, yea, it is designed for perfectly distributed snow, wind and other loads. But know that one can step up to thicker guage material, and more stout primary/secondary structures (perhaps by specing greater wind or snow loads ... I dunno. Perhaps some additional structural members under the rack attachemnts ????

    Thanks again, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • rollandelliottrollandelliott Solar Expert Posts: 834 ✭✭
    Re: Installing PV on Steel Shop Building Roof?

    http://www.schletter.us/commercial-fixz-7.html

    seems like a good product for metal roofs.
  • VicVic Solar Expert Posts: 3,152 ✭✭✭✭
    Re: Installing PV on Steel Shop Building Roof?

    Hi Roland,

    Thanks a lot for the link. Have just started looking at their hardware. If their systems are affordable, it should work! Also notice that say they have mounts for "frameless PV modules". FWIW.

    Thanks again, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • VicVic Solar Expert Posts: 3,152 ✭✭✭✭
    Re: Installing PV on Steel Shop Building Roof?

    Hi Roland,

    Had a meet with the erector of the candidate building, had sent him the link that you provided. He thought the Schletter mounting products would be fine for the style of roof that the building will be using. So, if these items are cost effective, we will be good. Thank you again for the link.

    And solarix thank you, too for your experiences with PV on shop roofs ... any additional info on exactly what racking/rails you used would help me and, quite possibly others.

    Thanks all, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • solarixsolarix Solar Expert Posts: 713 ✭✭
    Re: Installing PV on Steel Shop Building Roof?

    I fabricate my own racking system out of Alum Angle. Works great but is not UL listed of course. Which means I have to get my friend's PE stamp on the plans in order to pass permitting. Have to do that anyway most of the time because of building considerations such as the steel building like here. The manufactured racking systems such as Schletter are designed for ease of assembly - meaning no power tools (drills) on the roof. They use custom (expensive) slotted extrusions for mounting rails as a result in order to provide dimensional flexibility when assembling. It all gets a little too expensive to my mind especially when you figure in all the special little parts and pieces you have to buy from the manufacturer in order to build your system. One of the things the solar industry is going to have to do to get the costs down to be viable without tax credits etc, is standardize on a simple, cost effective mounting system. My aluminum supplier delivers for free, is way less expensive than these custom shapes, and we stock a whole bunch of standard stuff and easily cut and drill to put together a system. Cheaper, better, faster.
  • VicVic Solar Expert Posts: 3,152 ✭✭✭✭
    Re: Installing PV on Steel Shop Building Roof?

    OK, solarix, Thanks for the added detail.

    Well, the system just prior to this one, speced UniRac, primarily due to engineering considerations. It IS very, very expensive. It went together easily, for a very windy ridge. This system was overbuilt in every regard.

    Completly agree with you regarding the need to get installation costs down. Am not sure that NEC is helping much there either.

    I've beneifted personally for the Tax Credits, and they have helped the industry get rolling (IMHO).

    Thanks again for the information, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • rollandelliottrollandelliott Solar Expert Posts: 834 ✭✭
    Re: Installing PV on Steel Shop Building Roof?

    Solarix is Absolutely right about racking systems being very expensive. If you know of a Professional Engineer that can economically stamp your home made aluminum structures that is the way to go.
    You can get sample drawings from many different racking companies and pretty much tell from the drawings how they are constructed. And companies that wholesale aluminum like easternmetal.com have standard extrusions that just require a bit of machining to yield something that can be used to make a racking system easily. Aluminum cuts just like wood with an aluminum blade chop saw, taps easily, etc. There are other aluminum extrusions suppliers, just google them for your local area. The problem is getting local AHJ to approve your racking system.
  • VicVic Solar Expert Posts: 3,152 ✭✭✭✭
    Re: Installing PV on Steel Shop Building Roof?

    Hi roland/solarix,

    YES, I, too, am in total agreement with you both. AND that was part of why I asked the question.

    The site for this new project is technically a ridge, and it does get windy, so just need a conservative design. I have used one PE/Structural Engineer in the past, but he has become more successful, so has less time for the vanilla designs.

    I should find some PE starting out, but with a year or two experience.

    Have used AL extusions in the past, and am familiar with how to deal with it.

    Have also used 'Strut material for temporary racking as well, altho, the readily available 'Strut is all galv steel, and not exactly suitable AL PV frames. Have used SS fasteners and SS washers to try to isolate the AL from the steel, and for several year exposure, this works well enough.

    Thanks again, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
Sign In or Register to comment.