1. 20. http://en.wikipedia.org/wiki/Extremophile.
2. 19. http://en.wikipedia.org/wiki/Electrofuels.
3. 15. http://www.sheetak.com/.
4. 8. http://arpa-e.energy.gov/?q=arpa-e-programs/grids.
5. 6. http://energy.gov/sites/prod/files/SunShot_SEAB_Presentation_1-31-12.pdf.