SunPump

1. How much can Panels expand with changes in temperature?

The answer is scientific: 4.72 mm over 2 M at 100 C increase. (2.3 mm Left and Right) = 3/32" L & R at 180 F.

 

Here are the facts. Our Panel is made from AL 1060 with a thermal expansion coefficient of 23.6 µm/m-°C @Temperature 20.0 - 100 °C *
We have measured Temperature differences and can state they stay under 100 C. or 180 F from Sun to R410a.

To explain the micron unit: (µm/m-°C) units is Micron Per Meter Per Celsius Degree. Assuming 100 C temperature difference (180 F)

Here is the math to relate to our 2 Meter long panel. 23.6 microns x 2 M x 100 C

23.6 x 200 = 4,720 microns = 4.72 mm = 0.185 inch (3/16") = 3/32" L & R

2. Will a 3/32" expansion over 3 feet warp a Panel? 

To find out by demonstration, lay a 3 foot wood ruler or metal strip supported only at the ends, clamp blocks to both sides, and bend the middle until it moves between 1/16-1/8 inch on each end as measured by the increase in gap from the clamped block to the butt-end. 

Our answer is yes - mildly. Properly mounted, an expansion that deflects into a mild bulge should also return to form when cool the same as when you stop pushing down on the ruler it returns.

3. Then why has a small percent of installs shown significant warps?

Our hypothesis is when a combination of four conditions converge at the time of install:

1. Installed on a cold/Winter day so Panels were their shortest;
   
2. Installer workmanship is lacking and/or using substandard fasteners;
3. Installed with a mild amount of compression or flex, so the Panels were pushed to fit narrow holes;
   
4. Installed on a metal roof, perhaps an opposing vertical expansion? No warps known on Shingle roofs, or most metal roofs.
   

4. Is a warp a defect?

No. Panels have thermal expansion rates that are natural and to be expected. Our theory is a warp is an install issue that happens only when several factors are combined. A warp is cosmetic only, it is an install issue - not a performance or Warranty issue. (excerpt below)

As some background, the deformation rate of AL 1060 is 25%, which takes over 1000 PSI to burst current Panels, far more than a compressor maximum of ~620 PSI. A burst panel can only result is exceeding the Nitrogen pressure test maximum of 200 PSI by raising/bypassing the 0-2000 PSI pressure regulator. We are testing if it may be possible to distort a panel used incorrectly in a cooling Mode, at maximum high-side pressure while rejecting heat. Do not try Cooling with Panels.  

5. Can anything fix a warp?

Yes some degree of remedy can be done by your installer, at extra cost. Panels bolts can be loosened on a hot summer day, the warp can be pushed back by hand or with a block, and re-tightened in the expanded length. Bolt holes in the Panels can be expanded with a rasp-bit on a drill so round holes become slots to resolve the limitation of compression. Alternatively, a 3/4" x 1/4" x 6" 6" piece of Stainless Steel can be drilled with 3 holes, inserted, and bolted under the Panel 1" lip to brace the shape.

6. Are there any future changes?

Yes, SunPump is always seeking to improve every component. Structurally we plan increasing the metal gauge and doubling the 1-inch lip fold for a 2-ply structure, however this changes flex - it does not change the expansion of AL. Incorporating slotted holes in Panels and L-foot kits in 2017 is expected to avoid install compression. We will not replace panels, but are considering a small upgrade cost exception. (not including removal or reinstall). A Solar PV panel aluminum frame will be used when the PV-Thermal panel is available, at a higher cost for the co-generation panel. ETA is unknown, target is mid-2017 or later. 

*AL 1060 Reference PDF attached below and URL here:  http://www.matweb.com/search/datasheet.aspx?matguid=896dfdfb65834ca8aa8b0fcc6a7efcc4&ckck=1