But this system, while serviceable for decades, has inherent problems that must be addressed in the coming century, experts say. Within 50 years, or perhaps sooner, experts say, the world's supply of fossil fuels will begin an inexorable decline. Among other things, this will likely trigger a rise in oil prices. Moreover, power plants that burn oil and coal, and to a lesser extent natural gas, are significant producers of greenhouse gases that contribute to global warming. Fossil fuel-burning power plants are also among the chief producers of pollutants that mix with sunlight to form smog, the most widespread air quality problem worldwide.
Sulfur dioxide is also the major component of acid rain.
Energy experts say these problems could help spur the drive to generate cleaner and potentially cheaper energy. They are particularly enthusiastic about three methods of electrical generation that have been familiar for decades, but have yet to see widespread use in the United States. Fuel cells, which were used in the Apollo space capsules, are garnering new attention from the private and public sectors, in part because they're also seen as potential replacements for combustion engines in cars and trucks. Now, for the first time, companies are designing and testing models that can be used in homes. The fuel cells feature high-tech processors that take hydrogen out of fuels such as natural gas and propane.