Solar panels are, usually, made out of gallium arsenide. This compound presents itself in the form of large cristalized formation that reflect light in defferent ways, depending on the angle of incidence of light itself. To create such an effect in Cinema4D we have to create a compound shader too. We must combine several discreet ways to react to light coming from different angles into one single material. The new Layer shader is a natural for what we need. Unfortunately it only exists in release 8.3.

Inside the Color channel create a new Layer shader. Inside it place a Colorizer shader (14) and choose the shades of blue that you want for the solar panel.

Inside the Colorizer place a Noise shader and choose a noise type of Voronoi with the following parameters:

It is very important that the Space is set to UV(2D) to allow us to easily scale the material once it is applied to an object.

I placed a HSL shader (13) on top of the Colorizer so that I could easily control the color in a more general way but this is not required.

Create a new Folder (9) and inside it place a Noise shader with the following parameters:

On top of it place a Transform (12)shader so that we can control the angle of the streaks. I set it to 20 but any other angle will be fine.
On top of the Transform shader create a Colorizer shader (11) and place inside it a copy of the first Noise shader you created (lets call it, from now on, the Voronoi Noise). The Colorize shader should have this parameters:

The Colorizer should be set to Multiply. This way it will produce a black image with only a few cells filled with the streaks created by the Noise shader inside the folder. Now set the folder tranfer mode to Screen. This will combine it with the color defined bellow.

You now need to recreate the folder you just created, two more times (1 and 5).

The Noise shader that creates the streaks can have its parameters slightly changed.
The Colorizer that affects the Voronoi Noise must be set to different values in order to change different voronoi polygons to black and white. I set the Colorizers (2 and 6) to these values:

 

Also change the Transform (3 and 7) angle value to different values to vary the direction of the streaks.

Now, to create changes on the specular highlight according to the angle of light, lets create a Layer shader in the Specular Color channel.

Set Colorizers 3, 6, 9 and 12 to the following parameters:

Colorizer (3)	Colorizer (6)
Colorizer (9)	Colorizer (12)

Inside each Colorizer place a copy of the Voronoi Noise.
On top of each Colorizer place a Fresnel shader and set their parameters to the following values:

Fresnel (2)	Fresnel (5)
Fresnel (8)	Fresnel (11)

Set the transfer mode of each Fresnel to Multiply. Set the transfer mode of each folder to Add. The Fresnel masks will create a different Voronoi Noise for different angles of incidence.

Set the Specular Color channel to the following:

This way the result of the combined Layer shaders can be easily tinted.

Finaly, set the Specular channel to something like this:

It just needs to be wide enough to spread the effect and be high enough to be visible.
I also added an image to the Environment channel but that is optional, of course.

Have fun playing with variations of this setup :-)