Question s regarding mounting panels on a curved roof?

[Ampster]

Yea probably, but then there are considerations of the effects on array operating temps. that would have. Not a deal killer, just another design consideration.

At 60 MPH I am not sure it would make them much hotter because you could design the foil to allow some air but deflect the uplift forces. The biggest heat issue will be when you are stationary. If you park in the shade that wont be much of an issue.

[PNW_Steve]

Thanks for all of the replies!

I am quite confident of the all steel structure that I am attaching to.

My biggest concern is making sure that the panels are adequately supported.

The method shown in the picture looks slick and economical on materials but I lack confidence that it is adequate for the 300 watt panels.

Thanks

[J.P.M.]

The first thing I'd consider would be adding a foil at the leading edge to deflect all wind over the panels

Yea probably, but then there are considerations of the effects on array operating temps. that would have. Not a deal killer, just another design consideration.

[littleharbor]

The first thing I'd consider would be adding a foil at the leading edge to deflect all wind over the panels

[J.P.M.]

I think you could do a similar rails-down-the-length with unistrut or a more traditional solar-rail.

But I don't know how you'd calculate that the rails are fastened sufficiently.
Nor how to check that the fastening of the modules to the rails is going to hold up at highway speeds (with a headwind, and when going under overpasses.)
Possibly you could design it with IronRidge or something and use a windspeed well over 65mph.

I don't know if the DMV or state requirements would be considerations but my first observation/opinion is that the roof attachment will be the most problematic to design. Attaching panels to the usual building roof racking is probably an OK (but still checked) attachment, but I'd think a vehicle roof that's gage thickness sheet metal might be a challenge to make work.

I'd agree on your wind speed considerations and add that the NHSB has some information. I'm not now or ever was qualified for such vehicle wind design, but I'd probably consider several scenarios/conditions:1.) Some high ground wind speed, consider it a headwind, add the most likely max. vehicle speed to that wind speed for one condition. 2.)That condition however, because it may present a lower array area profile to the wind, might not be the most severe case. I'd might also consider (for example) the wind condition of max. vehicle speed and max wind velocity with the wind coming from a direction that is normal to the diagonal of the array, and then take the vector sum of those two resultant forces. There may be and probably are other conditions that might be considered depending on the judgement and experience of the designer and, of course, any jurisdictional requirements. But, I'd consider some ground speed and not simply vehicle induced wind forces.

[foo1bar]

Here we go...

I think you could do a similar rails-down-the-length with unistrut or a more traditional solar-rail.

But I don't know how you'd calculate that the rails are fastened sufficiently.
Nor how to check that the fastening of the modules to the rails is going to hold up at highway speeds (with a headwind, and when going under overpasses.)
Possibly you could design it with IronRidge or something and use a windspeed well over 65mph.

[J.P.M.]

If I had the engineering skills I probably would not need to ask the question.....,.

So, lacking necessary knowledge, I sought assistance from the smartest group of people that I could find.

Personal tip: NEVER drive behind a car with a mattress on the roof.

True story: I was driving on an expressway in Buffalo in the early '80's on the way to work. I was maybe 6 - 8 or so car lengths behind a full size dump truck carrying a load of dirt/etc. when the box on the truck suddenly started to rise. We were traveling at speed and things were pretty crowded on the road. My lucky day as I was about 5 car lengths from an exit so I scooted off and only had a few dirt/stone chips. I was driving my winter car at the time so a few more scratches/dents didn't matter. Most of the load was dirt but some small stones/pea size gravel etc. got spewed on the road before the driver realized WTF was happening. Fortunately there were no overpasses coming up. The TV news said driver unfamiliarity with the truck operation was the cause. Expessway was closed for several hours while probably 15 -20 yards of dirt etc. were removed over maybe 1/4 mile of roadway.

[PNW_Steve]

I can't tell from the picture with enough detail. Presumably you are going to be driving that bus down the Interstate highway so they will be subject to wind loads and vibration. Do you have rudimentary engineering skills to logically account for wind uplift loads? The classic example of what not to do is the guy with a mattress tied to the roof of his car with a piece of string.

If I had the engineering skills I probably would not need to ask the question.....,.

So, lacking necessary knowledge, I sought assistance from the smartest group of people that I could find.

Personal tip: NEVER drive behind a car with a mattress on the roof.

[PNW_Steve]

Painting probably won't mitigate galvanic corrosion. Isolating dissimilar metals is what prevents that kind of corrosion. Not a big issue especially if you are not near moist or salt air. Is the bus body steel or aluminum?

I am not understanding?

AL on a steel roof would certainly be more problematic than galvanized steel. I am not too concerned about the weight of the steel Unistrut. It may be a pain to handle but I only have to do it once.

[J.P.M.]

And you will have less of an issue with galvanic corrosion if you use aluminum.

The way I learned it, one way of several to reduce/eliminate(?) galvanic corrosion where 2 metallic surfaces are joined is to use similar (or identical) metals. If the roof is steel, that would indicate using steel supports. If the roof is steel, using aluminum for support material without taking measures to reduce the galvanic potential between the two metals will have the potential to cause more problems than steel on steel.

[littleharbor]

I like the guy who drove past us at 80+ mph. with a new fridge in the bed of his truck. 1/2 mile ahead everybody starts slamming on the brakes. New fridge basically exploded all over the freeway. I'm sure that went over well with the little woman.

[Ampster]

Any thoughts on the mounting method shown in the picture?

I can't tell from the picture with enough detail. Presumably you are going to be driving that bus down the Interstate highway so they will be subject to wind loads and vibration. Do you have rudimentary engineering skills to logically account for wind uplift loads? The classic example of what not to do is the guy with a mattress tied to the roof of his car with a piece of string.

[Ampster]

It will be painted. I would think that a quality paint job would protect it adequately.

What do you think?

Painting probably won't mitigate galvanic corrosion. Isolating dissimilar metals is what prevents that kind of corrosion. Not a big issue especially if you are not near moist or salt air. Is the bus body steel or aluminum?

[littleharbor]

Not terriby concerned about the weight. I have an 8000 pound "weight budget" for the conversion.

When you pick up a full length of the rectangular steel stuff you'll understand what I mean. It is so heavy you may find even handling and mounting it difficult. plus the corrosion factor.

[PNW_Steve]

Any thoughts on the mounting method shown in the picture?