HuffPost Innovators Series: The Automotive X PRIZE Finalists (PHOTOS)

09/13/2010 01:21 pm ET | Updated May 25, 2011

In the latest edition of the HuffPost Innovators series (check out previous editions here, here and here), we've compiled some of the most promising eco-friendly cars in the world. And, yes, they are fast. Very fast.

The seven vehicles below are all finalists in the $10 million Progressive Automotive Insurance X PRIZE. The X PRIZE Foundation is a Playa Vista, Calif.-based non-profit that organizes prizes and competitions to drive "radical breakthroughs" in technology and innovation. (The foundation recently challenged innovators to help solve the Gulf oil spill.)

The requirements? Each car must exceed a 100 mile-per-gallon fuel efficiency standard and can be fueled by any energy type, including gasoline, hydrogen or grid electricity The competition was held in several stages, including a lab-based series of tests and on-track stage. Judges evaluated each car on aspects like cost, fuel efficiency and design.

After eliminating all but seven of the 111 entrants, on September 16 in Washington, D.C. the X PRIZE Foundation will anoint one winner in the "mainstream class," which will receive $5 million, and the remaining funds will be split between the two winners of the alternative class of vehicles.

Which car is the most innovative? Check them out and vote for your favorite below.

(We are still looking for submissions to HuffPost's Innovators Series! To submit an innovative entrepreneur, startup or established company, click "ADD A SLIDE" below and upload a short description and picture of the founder or business leader you'd like to nominate. Note: Please skip the marketing jargon and keep your descriptions short. If your story is compelling, a HuffPost staffer will contact you to learn more about your story.)

HuffPost Innovators Series: The Best Of The Automotive X Prize