Maybe 'evaporated' was not the best word to use. I am talking about the water that collects on the back of the panel and drips off. Perhaps an air-conditioner or water heater drip pan would work well for collecting the water. Most of them have a drain on them that can be attached to with standard plumbing fittings.

Also any reflective surface would work and you would not necessarily have to use mirrors. That is definitely a valid concern about fire but I think that it can be done safely. There are a lot of images of various reflective surfaces/material that people use to reflect more sunlight onto solar panels. Perhaps a simple online image search will show you some examples.

Distilled water would probably work best but I think as long as you do not have a lot of iron, calcium, sulfur or minerals in the water it would work fine.