Green Energy

Renewable Energy: Wind

There is evidence that wind energy was used to propel boats along the Nile River as early as 5000 B.C. Simple windmills were also used in China to pump water and grind grain. In the United States, millions of windmills were erected to pump water for farms and ranches as the American West was developed during the late 19th century. By 1910, many European countries were using wind turbine generators to produce electricity.

Wind is thermal power that has already been converted to mechanical power.  As the wind turns the blades of the turbine, the rotating motion drives a generator, producing electricity with zero emissions. This is referred to as "wind energy" or "wind power." This power can then be used for specific tasks (such as grinding grain or pumping water) or can be converted to electricity (through a turbine).

Modern wind turbines fall into two basic groups; the horizontal-axis variety, like the traditional farm windmills used for pumping water; and the vertical-axis design, like the eggbeater-style Darrieus model, named after its French inventor. Wind turbines are often grouped together into a single wind power plant, also known as a wind farm, and generate bulk electrical power. Electricity from these turbines is fed into the local utility grid and distributed to customers just as it is with conventional power plants.

All electric-generating wind turbines, no matter what size, are comprised of a few basic components: the rotor (the part that actually rotates in the wind), the electrical generator, a speed control system, and a tower.

Wind turbines are available in a variety of sizes and power ratings. There are machines that have propellers that span more than the length of a football field, stand 20 building stories high, and produces enough electricity to power 1400 homes. A small home-sized wind machine has rotors between 8 and 25 feet in diameter and stands upwards of 30 feet and can supply the power needs of an all-electric home or small business.

Wind turbine power capacity can range from several kilowatts to several megawatts, depending on the turbine design and the length of the blades. Most turbines now produce about 600 kW but more powerful machines are becoming more common as the market expands and technology improves. There are currently several different types of turbines available - with 1, 2, or 3 blades, different blade designs, and varying orientations to the wind.  

The feasibility of wind power for a particular location depends on the amount of wind available at the site. Wind speed is a critical feature of wind resources, because the energy in wind is proportional to the cube of the wind speed. In other words, a stronger wind means a lot more power.

Wind energy has been the fastest growing source of electricity generation in the world in the 1990s at a rate of about 26% per year. It is also the most economically competitive of the renewables. However, the majority of this growth has been in Europe, primarily in Denmark and Germany, where government policies and high conventional energy costs favor the use of wind energy. India has also experienced tremendous growth with the private sector playing a lead role confining the government's role to that of a catalyst providing technical guidance and economic stimuli such as capital subsidies, exemption from certain duties and taxes.

Wind power is also being used extensively in the US, mostly in California. More countries have the potential to develop wind power in a significant way than have access to large domestic hydropower sources or fossil fuel deposits.

The global wind energy industry has grown steadily over the last 10 years and companies are now competing aggressively in energy markets around the world.  The industry continues to expand and develop a full range of highly reliable, efficient wind turbines. These new-generation turbines, when installed, perform at 98 percent reliability in the field, representing remarkable progress since the technology was first introduced as a sustainable energy resource in the early 1980s.

Although wind is an intermittent source of power which poses some concern, unlike hydropower, wind energy tends to be readily available at times of highest electricity demand.

One advantage to wind power technology is that turbines can be used singly or in small groups to provide power locally or can be part of an energy system, either with other renewable energy sources or connected to the grid.

Several factors affect the cost of wind power - for example, the wind speed at a particular site, the reliability and efficiency of the turbines, and the estimated rates of return on investment - but overall, costs are declining. With improved technology and manufacturing procedures, the cost of generating electricity from wind power has dropped to less than 7 cents per kilowatt-hour, compared to 4-6 cents per kilowatt-hour to operate a new coal or natural gas power plant-and prices are expected to drop even further over the next 10 years. 

New, utility-scale, wind projects are being built all around the United States today with energy costs ranging from 3.9 cents per kilowatt-hour (at very windy sites in Texas) to 5 cents or more (in the Pacific Northwest). In the US, wind energy provides more jobs per dollar invested than any other energy technology - more than five times that from coal or nuclear power. Modern wind technology takes advantage of advances in materials, engineering, electronics, and aerodynamics.

Many states in the USA now permit "net metering," in which the utility must buy wind power generated by homeowners at the same retail rate the utility charges. This essentially allows the customer's meter to turn backward while wind energy is supplied to the grid by the customer's turbine.

The amount of emissions avoided from California's wind power plants in 1990 alone was more than 2.5 billion pounds of carbon dioxide, and 15 million pounds of other pollutants. It would take a forest of 90 million to 175 million trees to provide the same air quality.

In spite of the dramatic decrease in costs over the past 10 years, the technology requires a higher initial investment than fossil-fueled generators. Roughly 80% of the cost is the machinery, with the balance being the site preparation and installation. These high initial costs are offset by the minimal operating expenses and zero fuel bill.

Although wind power plants have relatively little impact on the environment compared to other conventional power plants, there is some concern over the noise produced by the rotor blades, aesthetic (visual) impacts, and occasional avian (pertaining to birds) mortality. Most of these problems have been greatly reduced through technological development or by properly siting wind plants, although avian mortality remains an issue to be better understood and resolved.

The major challenge to using wind as a source of power is that it is intermittent and does not always blow when electricity is needed. This challenge is overcome by using batteries. In addition, good wind sites are often located in remote locations far from areas of electric power demand (such as cities). In certain regions, wind resource development may compete with other uses for the land and those alternative uses may be more highly valued than electricity generation. However, wind turbines can be located on land that is also used for grazing or even farming.