For most of the past decade, small but influential groups of energy experts have been arguing that the time has come to abandon the whole fossil fuel experiment in favor of something better: hydrogen. The most abundant substance in the universe, it contains more energy per unit of weight than any other fuel. And it's clean: A hydrogen-powered fuel cell emits literally no harmful pollutants, just a dribble of pure water. A hydrogen-based economy, therefore, would be both clean and secure-and quiet, since fuel cell-powered vehicles are virtually silent. It's an attractive prospect.

Hydrogen ICE and Fuel Cells

The shortest path to hydrogen is also the most familiar. With a few upgrades, including a better-insulated fuel tank, specialized cooling equipment, fuel injectors, and valves, today's vehicles could be converted to burn hydrogen. Because hydrogen has a very wide combustion range, engines burning it can run smoothly in "lean" mode, producing easier starts and higher fuel economy. And because it burns cleanly, hydrogen internal combustion engines (ICE) meet the world's most stringent emissions standards. The BMW Hydrogen 7 concept car, for instance, goes 133 miles per hour, can travel 125 miles on a tank of hydrogen, and has a separate tank for gasoline if hydrogen isn't available. Most reviewers say it drives like its gas-burning counterpart-which is to say really well.

The downside of hydrogen ICE is efficiency. Because hydrogen requires energy to produce and store, it's less efficient from "well to tank" than gasoline. Internal combustion engines, meanwhile, are a relatively inefficient way to convert a fuel to power. Combine the two, and you get results that, while possibly acceptable in the near term, aren't a long-range solution. So think of hydrogen ICE as a transitional technology to drive the build-out of a hydrogen-based infrastructure.

Which brings us to the fuel cell-the real engine, so to speak, of the hydrogen economy. In much the same way that a battery brings different substances together to produce reactions that, in turn, produce electricity, a typical fuel cell exposes hydrogen to a catalyst (usually platinum) that splits the hydrogen into protons and electrons. A membrane allows the protons to pass unimpeded to combine with oxygen to form water. Electrons, however, can't cross this membrane and are forced to take a longer route through wiring outside the cell, producing electricity that powers an electric motor. The water vapor and waste heat are released through the exhaust. No greenhouse gases, no acid rain, no money flowing to nuclear-armed psychopaths. And because fuel cells operate like batteries, they can participate in vehicle-to-grid power systems, feeding power to the grid while their owners are at work. It's easy to see why so many people love this technology.

The other reason fuel cells are so interesting is that they're two to three times more efficient than internal combustion. This more than offsets the lower well-to-tank efficiency of hydrogen, producing a highly efficient vehicle that can cover twice the distance of a conventional car on the same amount of energy. In 2008, fuel cell concept cars were operating at efficiencies comparable to hybrids, with most industry observers predicting continued dramatic gains. Based on the progress of the recent past, this seems like a safe bet: In 1994, when Canadian fuel cell maker Ballard Power partnered with German automaker Daimler on a prototype fuel cell vehicle, the fuel cell took up the entire back of a van. A decade later, fuel cells were small enough to fit into a compact car without sacrificing passenger space, at a fraction of the 1994 cost. The U.  ....read more