Check out these links for project ideas

Collier's Cranes at the MIT Stata Center
http://cranes.mit.edu/about

Info on wind powered scooters
https://en.wikipedia.org/wiki/Wind-powered_vehicle

Theo Jansen's Strandbeests
https://www.youtube.com/watch?v=PuxtdylbwVs

How to make toy helicopters
https://www.youtube.com/watch?v=VzudVzZE7LE

How to build a hydroponics system-Ezra
https://www.epicgardening.com/hydroponic-systems/