Fuel cells directly convert the chemical energy in hydrogen to electricity and some heat. Inside a fuel cell, hydrogen electrochemically combines with oxygen (from the air) to create electricity, with pure water and potentially useful heat as the only by-products.
Hydrogen-powered fuel cells are not only pollution free, but also can be more than two times more efficient than internal combustion technologies. A conventional combustion-based power plant typically generates electricity at efficiencies of 33 to 35 percent, while fuel cell systems can generate electricity at efficiencies of up to 60 percent (and even higher with cogeneration). The gasoline engine in a conventional car is less than 20% efficient in converting the chemical energy in gasoline into power that moves the vehicle in normal driving conditions. Hydrogen fuel cell vehicles, which use electric motors, are much more energy efficient and use 40-60 percent of the fuel’s energy – corresponding to more than a 50% reduction in fuel consumption, compared to a conventional vehicle with a gasoline internal combustion engine. In addition, fuel cells operate quietly, have fewer moving parts, and are well suited to a variety of applications.
Fuel Cell Basics
A single fuel cell consists of an electrolyte sandwiched between two electrodes, an anode and a cathode.
The power produced by a fuel cell depends on several factors, including the fuel cell type, size, temperature at which it operates, and pressure at which gases are supplied to the cell. A single fuel cell produces approximately 1 volt or less – barely enough electricity for even the smallest applications. To increase the amount of electricity generated, individual fuel cells are combined in series to form a stack. (The term “fuel cell” is often used to refer to the entire stack, as well as to the individual cell.) Depending on the application, a fuel cell stack may contain hundreds of individual cells layered together. This “scalability” of fuel cells makes them ideal for a wide variety of applications, from laptop computers (50-100 Watts) to homes (1-5kW), vehicles (50-125 kW), and central power generation (1-200 MW or more).