Graduate Student Research Assistants Peter Johnstone and Andrea Allen test module performance at the Schatz Solar Hydrogen Project.
Renewable energy is energy that comes from sources that are naturally replenished.
Ultimately, all renewable energy used on earth is solar energy. Solar thermal energy and photovoltaic devices make direct use of solar radiation, but wind, hydroelectric, and biomass energy are also driven indirectly by the sun. Geothermal energy is technically nonrenewable, as it is driven by limited steam reservoirs in the ground, but it is usually classified as renewable due to its wide perception as a clean way to generate electricity.
Petroleum and natural gas are expected to become scarce in the coming decades. Coal and uranium offer longer-term energy supply, but they too will eventually run out. In addition, all of these fuels produce environmental impacts that threaten our health and quality of life. Renewable energy sources are clean and will not run out in the foreseeable future. Because of their consistent long-term availability, renewable energy resources are also inherently more stable in price than fossil fuels. Many renewable energy technologies are modular and portable, making them practical anywhere from a city center to a remote mountaintop. And renewable energy is naturally decentralized, offering us a safer and more robust alternative to today's giant-scale power plants and their vulnerability to fuel price swings, natural disasters, and terrorism.
At SERC, we specialize in developing systems that integrate renewable energy with hydrogen and fuel cells. Renewable energy is naturally intermittent. Hydrogen provides a means to store renewable energy for times when the sun doesn't shine or the wind doesn't blow. When these resources are available, they can be used to generate electric power for immediate use, with surplus energy being converted to hydrogen using an electrolyzer. The hydrogen is stored until renewable energy is unavailable, at night or on cloudy or windless days. A fuel cell then converts the stored hydrogen to electric energy. Hydrogen thus offers a solution to renewable energy's key deficiency, i.e. that it's not always available when we need it.
On a dollars-per-kilowatt-hour basis, renewable energy is still generally more expensive than fossil fuels, although its cost is decreasing all the time. In some energy markets, new wind turbines are already less expensive than new conventional power plants. As fossil fuels become scarcer in the future, renewable energy will be more economically attractive. While recent growth in the renewable energy industry is in part due to government and utility incentives, it must be noted that conventional fuels also benefit from direct and indirect subsidies, including externalization of the social costs created by polluting power plants.
It is feasible for most homes to generate all or most of their energy on-site using photovoltaics and other technologies. However, bear in mind that a dollar spent on making your home more energy efficient will generally return much more in long-term energy cost reduction than the same dollar spent putting solar modules on your roof. If you are considering installing renewable energy equipment, work first to make your home as energy efficient as possible. Renewable-powered transportation is another matter. In wealthy countries, where nearly every household owns at least one car, it is probably not realistic to anticipate that renewable energy will enable us to continue with business as usual. A more modest and efficient transportation system might be sustainably run on renewable energy.
The same point holds true on a global scale -- the more energy-efficient we make our society, the more feasible it will be to convert to an all-renewables economy. "Sustainable" as renewable energy may be, it cannot indefinitely support unsustainable growth in global energy consumption. Wealthy countries have the most room for improvement: per capita energy consumption in the U.S. is six times that of the rest of the world, and over ten times greater than in developing countries. Some good news: the surface of the Earth receives ten thousand times as much solar energy each year as is consumed by all human activity.
