Or a bicycle.
Multiuse components reduce weight and expense... unless they add volume and/or complexity. Adding another layer to a display makes the display more complex to produce and possibly thicker/more fragile, as well. Adding a layer to a window reduces transparency of the window, I'm sure. But all of this could be negated by the idea of shortening the distance between power and use, I agree.
Ethanol will only be a viable fuel option in my mind when it is produced from something that requires no petroleum-based fertilizers and minimal power to harvest and process.