I would like to know the definitions of flexi glass and plexi-glass. I also would like to know if a person can use plexi-glass on a solar panel with the same results that flexi glass would give.

You have to take curves such as these:

The spectral response of the solar cell (depends on material and manufacturer))

For silicon
Spectral Response (http://pvcdrom.pveducation.org/CELLOPER/spectral.htm)

and the transmission spectrum of the material. This will depend a little on thickness.

For plexiglass
Light Transmittance Values for Plexiglass (http://www.rplastics.com/plexiglass-transmittance.html)

The full scale values of 1 and 100% are one in the same. Um and nm can be converted as well.

You then can integrate the area under the curve of the solar cell and call it 100%.

Then you can multiply both curves and integrate under the result and normalize 100% to the value above.

I could not find a transmission cure for flexiglass.

I would like to know the definitions of flexi glass and plexi-glass.

Plexiglass is a brand name. Its chemical name is "polymethyl methacrylate". It's often referred to as extruded acrylic.

I've never heard of Flexiglass or Flexi-glass. I googled the name and it appears to be an plastic used to make car and motorcycle parts (Flexi-Glass (http://www.flexi-glass.com/)). I'm not sure if there's another product that's used on solar panels. Maybe you can educate me.

Acrylics are known to be brittle -- they will break if you hit them with a hammer. However, they are resistant to the effects of UV rays and sunlight. Acrylics won't yellow the way polycarbonates do, for example. They also are resistant to cracking and crazing in sunlight.