* Make solar energy economical

* Provide energy from fusion

* Develop carbon sequestration methods

* Manage the nitrogen cycle

* Provide access to clean water

* Restore and improve urban infrastructure

* Advance health informatics

* Engineer better medicines

* Reverse-engineer the brain

* Prevent nuclear terror

* Secure cyberspace

* Enhance virtual reality

* Advance personalized learning

* Engineer the tools of scientific discovery

http://spectrum.ieee.org/tech-talk/at-work/innovation/041610-how-to-solve-the-worlds-greatest-technology-problems
http://www.engineeringchallenges.org/