Why Fuel Cells?
Like combustion engines, fuel cells operate using fuel from tanks that can be easily refueled. As long as fuel is available, the cell can run continuously. The major advantages that fuel cells hold over internal combustion engines however are the high efficiency of operation and the lack of harmful pollutants. Below is a projection made by Mercedes-Benz on the efficiency of compact cars powered by fuel cells versus other energy sources:
Graph Courtesy of Mercedes-Benz
Fuel cells generate electricity directly from fuel by way of an electrochemical reaction, an efficient process (Chemistry of Fuel Cells). Because fuel cells simply create electricity in this manner, they can be used in myriad different ways (Applications of Fuel Cells). When combustion engines generate power, a large portion of the energy of combustion is lost to waste heat and friction, resulting in their low efficiency. The lack of friction within a fuel cells coupled with the lack of moving parts contribute greatly to the low maintenance needed by fuel cells. Other byproducts of combustion include pollutants such as sulfur dioxide and nitrogen oxides. Fuel cells, again because of their mechanism of operation, produce little or no pollutants depending on the type of fuel cell (Types of Fuel Cells). The U.S. Department of Energy (DOE) is projecting that if 10% of automobiles used in the US were powered by fuel cells, air pollutants currently regulated air pollutants would be cut by one million tons per year and 60 million tons of carbon dioxide would be eliminated from the yearly greenhouse gas production (see Fuel Cells 2000). The DOE has also stated that advanced fuel cells using natural gas could potentially reduce carbon dioxide emissions by 60% compared to a conventional coal plant and by 25% compared to today's natural gas plants. In fact, fuel cells running on hydrogen derived from a renewable source would emit nothing more than gaseous water.
Another benefit of fuel cells that makes it similar to some industrial combustion processes and better than others is the ability to capture excess heat generated and use it in a cogeneration-like manner or for space/water heating. These methods of increasing the overall efficiency of the fuel cell have been shown to push the efficiency to approximately 80% for both the phosphoric acid and molten carbonate fuel cells (see DOE Fossil Energy).