Where is the hydrogen that's going to power the fuel cell going to come from?
As the H in H20, hydrogen is one of Earth's most plentiful elements. So why do fuel cells get their hydrogen from natural gas?
The answer is that to separate hydrogen from water is expensive. The process, known as electrolysis, requires passing an electric current between two metal electrodes bathed in water; hydrogen gas is formed at the negative electrode and oxygen at the positive electrode. The problem is, powering an electrolysis reaction takes a lot of electricity. In fact, with existing equipment, the amount of electricity that could be generated by a fuel cell with hydrogen produced by electrolysis is only about half of the electricity that would be needed to actually split the hydrogen from water. And, of course, the vast amount of electricity to run electrolysis is distributed by utilities generally burning fossil fuels, defeating the goal of clean, economical power that fuel cells are supposed to deliver. "It's very, very expensive to get hydrogen out of water with today's technology," says Robert Kripowicz, acting assistant secretary for fossil energy at the U.S. Department of Energy.
Extracting hydrogen from natural gas, on the other hand, is far less costly and doesn't hog electricity. The most efficient method involves heating the gas with high-temperature steam in the fuel cell's reformer. In the process, hydrogen is separated from carbon molecules.
At least 20 years' worth of natural gas reserves are available now, according to the National Petroleum Council, and new technologies are being developed that will soon let suppliers tap enormous resources too deep to get at today.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.