Wind Turbines-2

Where Do Winds Come From?
The sun has a lot to do with creating winds. Winds above continents and oceans occur because of temperature differences around the world. Some places, especially those near the Equator, receive far more direct sunlight than those closer to the Earth's north and south poles. As a result, the air over these areas warms up and then rises. Cooler air from the surrounding area rushes in to fill the space left by the rising air, creating a surface wind.

Capturing Wind Energy
Air is constantly on the move. In some places, especially along coastlines and in mountains, it provides a highly reliable source of mechanical energy. Humans have invented an amazing array of devices that can harness the energy of the wind and put it to practical use.

Sails
One of the oldest uses of wind energy is transportation. The first primitive sails were probably made from woven mats held aloft by wooden poles or human hands. Modern sailboats have very efficient sails and masts constructed from strong, lightweight materials such as Kevlar (the material used in bulletproof vests) and titanium. They work like aircraft wings to generate forces that pull the boat in the desired direction.

Pumping and Grinding
Long before the invention of electricity, early wind turbines did very useful work. Windmills were used in many places in Europe over the last several centuries to turn heavy granite disks called millstones. The millstones were used to crush dry grains such as wheat, barley, and corn to make flour or meal.

The Netherlands is famous for its windmills. In truth, most of these structures are not mills at all, but water pumps.

The Dutch created new farmland along the coast by building dikes around low-lying estuaries and mudflats and pumping out all the seawater. The "windmills" provided a steady supply of mechanical energy to lift seawater into the canals, allowing the new farmland to dry out.

In the past, windmills were common on farmsteads across Canada. They were often used to pump water from wells to watering troughs for cattle and to generate electricity at the farmhouse. When rural areas finally received electricity, many of these windmills fell into disuse and disrepair. Recently however, small windmills are becoming popular once again for bringing water to livestock.

Generating Electricity
One of the most popular uses of wind turbines is to generate electricity. To make electricity, the shaft of the turbine must be connected to an electrical generator. Through gearboxes, the generator converts the mechanical energy of the spinning turbine shaft into electricity.

The wind farm at Castle River, Alberta, generates enough electricity to meet the needs of several thousand Canadian homes. Photo courtesy of Vision Quest Windelectric Inc.

Generators are small and light enough that they can be housed under an aerodynamically designed cover at the top of the pole or tower. Wires running down the tower carry electricity to the grid, batteries or other appliances, where it is stored, and/or used.

Electricity is now being generated on a commercial scale at large installations called "wind farms" in several places around the world. Wind farms consist of rows of towers, sometimes 90 metres high, equipped with giant wind turbines for producing electricity.

In Canada, the first commercial wind farm was built in southern Alberta near the town of Cowley, in a region famous for its strong, steady winds. Commercial wind farms have also been established in Germany, Denmark, the United States, Spain and India. Denmark and Germany have pioneered the development of commercial wind power, one of their fastest-growing industries.

Some companies are now installing wind farms in shallow waters near coastlines in small countries with little available land area. These "offshore wind farms" are a promising new source of electricity. Toronto Hydro is installing such a turbine offshore on Lake Ontario.

Commercial wind energy is one of the most economical sources of new electricity available today. Wind turbines can be set up quickly and cheaply compared with building new coal-fired generating stations or hydroelectric facilities. Modern wind generating equipment is efficient, highly reliable, and becoming cheaper to purchase. The environmental impact of large wind turbines is negligible compared with an open pit coal mine or a reservoir, and during their operation produce no air pollution. Because of these factors, wind energy is recognized as the world's fastest-growing new energy source.

Small, highly efficient wind turbines are becoming popular as a source of electricity for rural homes. The cost of installing one comes close to that of putting up poles, overhead power lines and other equipment necessary to connect to the electrical grid. The advantage is that the homeowner owns the generating equipment and is freed from paying monthly electrical bills!

Fuel Cells

Fuel cells and their ability to cleanly produce electricity from hydrogen and oxygen are what make hydrogen attractive as a "fuel" for transportation use particularly, but also as a general energy carrier for homes and other uses, and for storing and transporting otherwise intermittent renewable energy. Fuel cells function somewhat like a battery—with external fuel being supplied rather than stored electricity—to generate power by chemical reaction rather than combustion. They typically consist of numerous small cells in layers though, rather than a single large one. There are several different types of fuel cells using different catalysts (chemicals, in this case probably metals, that trigger a chemical reaction without themselves being used up by it) and electrolytes (non-metallic conductors of electrical ions, classically in a solution, but for fuel cells more likely in a solid membrane). In one type, for example, however, hydrogen fed to one catalyst-containing electrode splits to a positively charge hydrogen ion (proton) and a negatively charged electron. The positive ions travel through the electrolyte to the other catalyst electrode where they combine with oxygen fed to that electrode—and electrons—to produce water and heat. The necessary electrons are drawn through an electric circuit external to the cell, creating the electrical generation.

NREL's current fuel cell work is primarily on developing durable, less-expensive materials for fuel-cell components. Platinum and other current electrode catalysts are costly (particularly for low-operating-temperature fuel cells) and conditions can be highly corrosive (particularly for high-operating-temperature fuel cells) both for electrodes and membranes. Fuel cell design options and their relation to other vehicle operating systems are quite complex. NREL is also applying its analytical capabilities fuel-cell system analysis to help DOE and industry partners identify critical areas for improvement and the most effective operating parameters for whole vehicle systems.

Wind Turbines

We have been harnessing the wind's energy for hundreds of years. From old Holland to farms in the United States, windmills have been used for pumping water or grinding grain. Today, the windmill's modern equivalent—a wind turbine—can use the wind's energy to generate electricity.

Wind turbines, like windmills, are mounted on a tower to capture the most energy. At 100 feet (30 meters) or more aboveground, they can take advantage of the faster and less turbulent wind. Turbines catch the wind's energy with their propeller-like blades. Usually, two or three blades are mounted on a shaft to form a rotor.

A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity.

Wind turbines can be used as stand-alone applications, or they can be connected to a utility power grid or even combined with a photovoltaic (solar cell) system. For utility-scale sources of wind energy, a large number of wind turbines are usually built close together to form a wind plant. Several electricity providers today use wind plants to supply power to their customers.

Stand-alone wind turbines are typically used for water pumping or communications. However, homeowners, farmers, and ranchers in windy areas can also use wind turbines as a way to cut their electric bills.

Small wind systems also have potential as distributed energy resources. Distributed energy resources refer to a variety of small, modular power-generating technologies that can be combined to improve the operation of the electricity delivery system.