This texture is FREE for personal and commercial use!
It can be downloaded at
https://www.texturecan.com/details/208/
They are the most common solar panels which are blue and highly reflective. As solar panels must be installed outdoors, dirt are inevitable.
There is also a more specific solar panel which is Tesla solar rooftop that can be downloaded at
https://www.texturecan.com/details/207/
This is a seamless and tileable PBR CG texture for 3D artists.
Each package usually includes a Base Color Map / Diffuse Map, Normal Map, Roughness Map, Displacement Map, Metallic Map (Metals Only) and Ambient Occlusion Map.
The texture maps are applicable to Blender, ZBrush, Sketchup, Maya, 3D Max, Cinema 4D, Unity, Unreal etc.