Solar panels on flat roof

[Nickmpower]

I have some solar panels I am looking to mount. I was planning on building a rack, but after looking at some calculators it might not be worth my time. I will only loose 12 percent efficiency in march and September laying them completely flat on the roof.

The main thing I am concerned about is the draining. Will I have to manually pump the water out before every winter? Will water boiling off in the plastic panels damage them?

 

[JasonLion]

As long as the panels are well supported, placing them on a flat roof is acceptable. However, the panels will need to be removed to drain them properly for the winter. There is no way to fully drain them in place when they are lying flat.

 

[mas985]

The main thing I am concerned about is the draining. Will I have to manually pump the water out before every winter? Will water boiling off in the plastic panels damage them?

With a proper design, it might possible to get the panels to mostly drain with just gravity and the siphon effect. Any remaining water should not be an issue in our area. I know that my panels do not completely drain and it hasn't been a problem for me in the 9+ years I have owned the pool. You just want enough air in the panels and pipes (>10%) to prevent freeze damage.

 

[Nickmpower]

So there isnt really a good spot for them unfortunately, but now the spot I'm looking at is slightly sloped. The only problem is that ideally, for aesthetic reasons the pipe would have to run back up the slope, then go back down to ground level near the fence in the back. Will Using a vacuum breaker allow the siphon effect to drain the panels?

 

[mas985]

If you can run the pipe along the fascia board on the side of the roof it may be possible to slightly tilt the pipe downwards (opposite the roof tilt) so it drains toward the fence. If that works, then it should be no problem and you won't get much water trapped in the pipes or panels. If you paint the pipe the same color as the side of the roof, I don't think it would be that noticeable.

 

[Nickmpower]

Yeah that also crossed my mind, was hoping to conceal it more. I am putting a nice white gutter on the front of the overhang, and also repainting everything etc. In its current state the pipe on the side would fit right in but once it is looking nicer it will stick out a little, might have to do it anyways.