Found where the number came from! Survey: Creating Tomorrow's Designer
Specifically:
The 20 concepts are all complete. They sometimes do just change one component or the way the components fit together, but often the change of one component had a ripple through effect where everything else had to be adjusted appropriately.
Unfortunately, ME’s in general don’t like concepts and I had to fight to be able to do them. I was originally asked for one functional concept and six refinement concepts outlining how everything will fit together. I’ll see if I can start up a project topic on the board, just have to clear it with the school first.
How do you guys know when you’ve exhausted your resources and reached the right solution?
The basic function of the device is fairly simple. My concepts (so far) cover things like self cleaning, environmental considerations, different power sources, etc. All sketches at the moment.