Challenge 2 Sandbox is now open! Familiarize yourself with the Problem Formulation (new November 24), Input Files and Formats, Output Files and Format, Rules, Scoring, and the Timeline (summarized below). Only members of Challenge 2 registered Teams may submit. Challenge 1 teams must reregister as Challenge 2 teams.
See References/Time Limits for new information about time limits.
Watch Lane Genatowski, ARPA-E Director, talk about Challenge 2 on YouTube.