Fires, why they happen.
First, let me say this....
Solar panel fires are EXTREMELY RARE.!
You have a better chance of being hit by lightning than having a solar panel fire.
A solar panel is made mostly of glass and aluminum, with some special plastic sheeting to seal it. Being dark colored they do get warm in the sunlight. More importantly, in the sun, they make electricity. And just like your home appliances, they have wire that plugs into the system. If this wire becomes shorted, it can lead to a fire just like your house appliances can. The wiring on a solar panel is very thick, and resistant to the outdoor environment. Installations all over the world run every single day without a problem. So when you see a array of panels on fire, its because of a poor installation, or more likely, sabotage. Lightning is also a rare possibility. Solar systems and the panels are extremely safe, and it's not easy to set a panel on fire. In fact, most solar panel fires are not caused by the panel failing, but the circuit breaker/fuse located on or near them failing due to exposure.
If you have a large panel, and something shorts it out, even then they don't catch fire for awhile. Getting the materials in a solar panel to burn takes a lot of heat. So what I'm saying is, solar panels are no more dangerous than your toaster. Do a search for "odds of having a solar panel fire" and you will see they are not prone to catching fire.