wicking waterer and heat cable— not possible?

I want to turn the whole of my cold frame into a wicking water, like the ones shown here. http://deepgreenpermaculture.com/diy-instructions/self-watering-tray/ This would be a big advantage, since things dry out fast here in Colorado, and I am very busy. I will be starting hundreds of plants for the Saint Isidore Society farm and for my home garden. The cool weather things will go in an unheated greenhouse.

However, I also need to start lots of tomatoes and peppers. I was planing to heat the frame with a heating cable under sand. Would this make water evaporate so fast as to make this watering system impossible?

Shouldn't. Yes, it can evaporate water but it should stay contained with the frame and rain back down, like a terrarium.