Types of Renewable Energy
What is renewable energy? The term has two basic components, neither of which necessarily defines itself.
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Everyday living aside, the concept of energy also has a technical side and science commonly represents it abstractly, referring to it as an ability to perform work. From an even more technical scientific starting point, the first law of thermodynamics states, "In all physical and chemical changes, energy is neither created nor destroyed, but may be converted from one form to another." Using science as a starting point, energy can be defined as things around us that change forms in order to perform a task.
Discussions of energy as it relates to renewable energy commonly refer to the types of fuels we use to perform the tasks associated with modern life. Fuels run our transportation system and they produce the electricity for our homes and offices and factories. Overwhelmingly, fossil fuels, coal, oil and natural gas have been the fuels of choice for performing these tasks. Fossil fuels are distinguished from renewables in the sense that they are finite resources, i.e., there's x amount under the earth and once used will run out unless you're willing to wait the millions of years for the fossilization process to create more.
Renewable energy, on the other hand, refers to fuel sources more consistently available than their fossilized counterparts. Sources for this energy commonly fall under five categories:
In theory these sources are infinitely available. As long as the earth continues to revolve around the sun, the sun will continue to produce harvestable energy. Heat from the sun additionally creates atmospheric conditions conducive to wind and water production, although not in even quantities throughout the world or with scientific precision in any one particular location. Finally, the sun produces the light necessary for growing the plants and trees which constitute the biomass category.
Long before the beginning of the industrial revolution, mankind used the natural resources at hand to serve as energy sources for every day tasks. Historical records of watermill and windmill use dates back to ancient China, Greece and Rome. Renaissance thinkers and builders expanded their use, creating machines to grind grain, create cloth and produce metal products. Today's versions of those same machines, while more technologically advanced to meet the energy needs of a larger population, operate on similar principles, harvesting the energy of the world around us.
Cleanliness is perhaps renewable energy's biggest draw. Whereas fossil fuels require a combustion process (the use of an engine or turbine) to convert the energy into a form capable of performing the task at hand, renewable energy sources require none. No combustion means no emissions byproducts that cause the most common types of air pollution today, acid rain, smog and climate change. How much cleaner are renewables? There's probably no single answer, however, consider the following two examples related to solar (photovoltaic systems) and wind energy.
The National Renewable Energy Laboratory reports (report no. FS-520-24596),
"An average U.S. household uses 830 kilowatt-hours of electricity per month. On average, producing 1000 kWh of electricity with solar power reduces emissions by nearly 8 pounds of sulfur dioxide, 5 pounds of nitrogen oxides, and more than 1,400 pounds of carbon dioxide. During its projected 28 years of clean energy production, a rooftop system with 2-year payback and meeting half of a household's electricity use would avoid conventional electrical plant emissions of more than half a ton of sulfur dioxide, one-third a ton of nitrogen oxides, and 100 tons of carbon dioxide."
In the wind power area, the American Wind Energy Association claims,
"A single 660-Kw wind turbine will displace emissions of 1,100 tons of carbon dioxide (the leading greenhouse gas), 6 tons of sulfur dioxide (the leading component of acid rain), and 4 tons of nitrogen oxides (the leading component of smog) every year, based on the U.S. average utility fuel mix. 375 acres (more than half a square mile) of forest would be needed to absorb the same amount of CO2."
© 2001. Patricia A. Michaels