Large Solar Panels

Salvo,

figure 2.5 is for a tilted panel. Flat to the roof is a bit of a different animal and laminar flow is an issue.

Any aerodynamics folks out there to chip in?

Take a look at 2.5. There's lots of lift.

http://www.kstr.lth.se/fileadmin/kstr/pdf_files/Exjobb/TVBK-5000_pdf/TVBK-5195JWweb.pdf

A flat board, panel, what not traveling straight forward will not create lift. It requires a air foil that will increase the wind speed over the top of the wing via up slope affect and then a decline in the foil to create low pressure. Tilting the wing will increase the lif but too much tilt and you lose the affect nd stall.

Now if you were nose high with the panel it would produce some lift but the main force would be from below at that time, kind of like flying a kite.

One thing I have noticed over the years is the older panels have a heavier duty frame on them than the newer panels, even those from the good ol USA. Obviously not all of the cost savings have come from just the Chinese dumping on the market.

Mike.

I'll be looking for help with installation here soon. I want to do it to my level of quality but it's not been a good winter physically for me so I'll look for installers. On the other hand we may be able to help each other out if you think you are up to it. I have all of the tools, saws, cutters, crimpers, drills and ladders needed for install and few neighbors that may even help with the heavier lifting. I plan on bribing them handsomely when it comes time to move the 8-D's.

So if you are interested, let me know. I'll need to pick up the mounting hardware just to get the panels up, after that I can wire at my own pace. That way we could get your wires ran and crimped too.

You will.

Back 10 years ago, when panels were much smaller Kyrocera already stated the panels were not guaranteed for rv use. I added extra Al angle to stiffen the frame.

I also wonder about the dynamics of air flow over panels. Do they act like a wing, giving them lift? I bet there's a lot more air flow over the top of the panel than the bottom. What's the implications of this pressure differential?

smkettner wrote:
NEVER read a post with panel damage from vibrations of the RV.
Large or small these panels are very tough. No worries.

NEVER read a post with panel damage from vibrations of the RV.
Large or small these panels are very tough. No worries.

scrubjaysnest wrote:
The first place to start is an energy audit, that will determine battery bank size from which you determine solar wattage needed.

He's been there already. As I recall, the conclusion in that other thread - by people here - was 400 AH battery bank and around 500W solar.

Yes, there is a notable flex in big panels. I don't drive much, and don't drive fast with trailer. Didn't have any problems at 50-55 mph, with one panel sitting on 3 legs only :) - needed to get to the camp while the mounting wasn't finished yet.

My 250W are sitting on 4 legs each. 2 more, on the long sides, can easily be added but I don't find it necessary yet. Alternatively, the frame can be stiffened by adding aluminum angle across the panel underneath (or again onto the long sides).

Hi,

The non MPPT Tristar controllers are fully featured and include the items you list. I am not sure, but I think they may also do diversion loads which would be a boon for a larger system.

If you are truly power hunger then a good case can be made for switching to a 24 volt bank. That brings the wattage limit up to 1600 for a single PWM controller.

brulaz wrote:
At the time, available mppt controllers seemed to be more sophisticated battery chargers, with available temperature compensation, and adjustable voltage set points and timers, in addition to the mppt function, so the extra cost was worth it to me.

I have 2 250 watt panels. I'm not sure they are poly or Mono but I think they are mono as there is an M in the model #. I could care less as the price was right. I had to run them in parallel due to the voltage limitation on my charge controller that I already had from a previous install. So far I have been happy with them. Even my smaller Kyocera 140 watt panels required two people to get on the roof so size wasn't an issue there. Two panels, 500 watts, done vs 3 panels 405 watts on my first install.

Smaller is better.

I chose to use angle aluminum on the long sides of my panels (which happen to have no glass) to help stiffen them. The panels are about 50" x 32". I put them in the "wind shadow" of other items on the roof and they hug the roof.

NinerBikes wrote:

Salvo wrote:
My biggest concern for larger panels is the vibrations a RV has. The panels may be seeing 2 g-force of vibrations. These panels are designed for roof or ground installations. The panels will see a lot of flexing.

Does this favor 100W panels or 250+watt panels?

Salvo wrote:
My biggest concern for larger panels is the vibrations a RV has. The panels may be seeing 2 g-force of vibrations. These panels are designed for roof or ground installations. The panels will see a lot of flexing.

Does this favor 100W panels or 250+watt panels?