Creating new ways to fill tanks

CAMBRIDGE, Massachusetts - The insatiable consumption of fossil fuels and concerns about climate change are driving the quest for alternative fuels, and a better battery could be part of the solution.

Cars must carry their energy and expend energy to carry it, so the less weight per unit of energy, the better.

The United States Department of Energy has a new agency dedicated to the search. The Advanced Research Projects Agency-Energy finances high-risk, high-reward projects and seeks profound results, such as tens of millions of vehicles that would run 480 kilometers a day on electricity from clean sources or on liquid fuels from trees and garbage.