Alternative Energy Basics

A recent presentation covered the fundamentals of alternative energy sources, including wind, solar, and biofuel

5 November 2010

With alternative energy—particularly wind, solar, and biofuel—so much in the news lately, a little tutorial might be useful. Harvey N. Weintrob presented just that during the IEEE International Telecommunications Energy Conference in June, in Orlando, Fla. The conference was sponsored by the IEEE Power Electronics Society. Weintrob is an instructor at Dan McMenamin and Associates, a consulting and training services company in West Deptford, N.J., that specializes in telecommunications and power equipment design, including alternative energy systems.

A wind turbine converts the wind’s kinetic energy into electricity, with the turbine’s blades spinning on a shaft that connects to a generator. The most common type of turbine has a horizontal axis, and blades that resemble airplane propellers.

Wind turbines are often grouped together at a power plant, or wind farm, or a green-oriented citizen might install a wind turbine at home. Electricity from the turbines is fed to the grid.

Wind farms are popping up around the world, with Denmark leading the way. About 20 percent of the country’s energy is now produced that way. Wind power generates 11 percent of Portugal’s electricity, about 7 percent of Germany’s, and roughly 5 percent of India’s.

The windiest U.S. locations are found in California, Colorado, Idaho, Kansas, Maine, Montana, and New York.

Whether a wind turbine at your home or business is a sound energy choice depends on the statement often made about real estate: “It’s all about location, location, location,” Weintrob says. Areas with an average annual wind speed of at least 20 kilometers per hour are considered good for turbines.

Although the turbines have relatively little impact on the environment compared with fossil fuels, drawbacks include noise from the blades, complaints of unsightliness, and concern over birds and bats killed by flying into them.

Solar systems rely on cells that convert light into electricity. The photovoltaic cells are made of semiconductor materials—often some variety of silicon—that absorb sunlight and produce an electric current.

A typical photovoltaic system is composed of solar panels made of rows of individual cells, a battery to store the energy, and a charge controller that monitors the battery and ensures it isn’t overcharged. Most solar-energy systems, which generate direct current, also require a DC to AC inverter to switch from the battery-stored DC to standard AC power.

How much electricity the cells generate depends on how much of the sun’s energy reaches the cells. Typically, solar panels are mounted on a roof and oriented to face south to get the most rays. But they can face up to 45 degrees east or west without significantly decreasing output.

Germany, Japan, Spain, and the United States are top producers of solar energy, according to the Renewables Global Status Report for 2009.

The disadvantages of photovoltaic systems are their high purchase price and installation cost, and they generate peak electricity only during sunny days. The cost of installation varies depending on the size of the system, ranging from about US $16 000 for a modest home to $100 000 for a large one.

More information on solar energy systems is available at the National Renewable Energy Laboratory’s PVWatts Web page, which includes links to calculators to help you determine the cost savings of using solar cells instead of electricity from the grid.

Biofuel is derived from biomass, which is organic material from such things as plants and manure. Ethanol made, for example, from sugar cane in Brazil or corn in the United States, is the most common biofuel. It is produced by fermenting sugars derived from the sugar cane or corn, as well as from wheat or molasses. Ethanol derived from the process is used as a somewhat lower-powered replacement for gasoline.

Biodiesel, another type of biofuel, typically is made from soybean oil. Biodiesel in its pure form can be used as a fuel for vehicles, but it is usually mixed in as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons emitted by diesel-powered vehicles.

Although biofuels—as other alternative energy sources—are not carbon-neutral, because energy is required to grow crops and convert them into fuel, there are advantages. Bioenergy can be produced using organic waste that might otherwise be discarded, thus reducing the environmental and economic cost of disposing of them.

Countries where bio-energy systems have been expanding include Germany, Italy, and the United Kingdom.

When you’re deciding on an alternative energy system for your use, make sure to look into state and federal tax incentives. Many governments offer credits or rebates for installing alternative systems.

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