Wind turbines trace their existence back to wind powered grinding mills which were built by the Persians around 200 BC to grind grains. Windmills were later used to operate pumps both to drain land of excess water and to irrigate land. The first windmill for electricity production was built in Cleveland, Ohio by Charles F. Brush in 1888. Since then, windmills of this type have been used to generate electricity for many farms and remote communities around the world. Today larger versions called wind turbines are being constructed to generate electricity on an industrial scale.
Wind turbines convert the mechanical energy of the wind into electrical energy in much the same way as most electrical generating stations by spinning or turning an electrical generator to generate electricity. Because wind is a free energy source, there are no fuel costs when generating electricity, and wind turbines produce no greenhouse gases. Germany is the world leader, having an electrical generating capacity of a little over 21,000 megawatts (MW). Presently, Canada has the capacity to generate slightly more than 3,000 MW of its electricity using wind power. However, 3,000 MW provides barely 1% of all the electricity generated in Canada.
Because the electrical output of most wind turbines is rather small, usually less than 1 MW, several wind turbines are often arranged in groups called wind farms. Wind farms need to be placed where the average wind speed is at least 10 kilometres per hour and may be placed on land, onshore or offshore. Wind turbines also need to be properly spaced to ensure that turbulence from one turbine doesn’t interfere with air flow to another. Many of the wind farms constructed in Europe have been offshore.
Like all technologies wind turbines do have challenges. The wind does not always blow or remain constant, so the electrical output of wind turbines can be variable and sometimes must be offset by other energy sources such as those generated by hydroelectric dams, fossil fuels or nuclear power. In the past, maintenance has been an issue because the stresses and vibrations caused by the wind can cause wear on turbine parts, which then must be replaced. If the wind farm is located in a remote area such as off-shore, repairs can be difficult to perform.
Perhaps the biggest challenge faced by wind turbine technology is efficiency. On average, wind turbines are about 20% to 25% efficient and have an electrical output of less than 6 MW, therefore large-scale wind farms require large areas of land. The Pickering Nuclear Power Generating Station operates at about 90% efficiency and has an electrical output of 4,124 MW. To generate the same amount of electricity based on 20% to 25% efficiency rate, more than 2,000 wind turbines covering a large area of land would be required. People in some communities in North America have halted the development of wind farms for aesthetic reasons, meaning they objected to how the wind farm intruded on the natural surroundings by creating a visually artificial landscape.
Wind technology is still in its early stages of development and despite the challenges, wind turbines produce electricity without producing the greenhouse gases that contribute to global warming. Many electric utilities across Canada will continue to construct wind farms and develop wind turbine technology as part of Canada’s overall energy mix.
Canadian Energy Research Institute, World Energy: The Past and Possible Futures, 2008, p. 81. www.cna.ca/english/pdf/Studies/CERI/CNA_CERI07_EN.pdf
Ontario Power Authority – www.powerauthority.on.ca
The Pickering wind turbine shown here produces enough power for 330 homes a year.
HOW IT WORKS
(Case Study Ontario)
Wind turbines that generate electricity operate in much the same way as a hydroelectric generating station. Instead of falling water, wind turbines use the kinetic energy of blowing air to spin the blades of the turbine which are connected to a generator.
Wind power currently provides about 1% of Ontario’s electricity but it is the fastest growing energy source in the world and will be playing an increasing role in supplying our electricity.
The amount of electricity a wind turbine can produce depends on the strength and consistency of the wind at any given time. Generally, the wind needs to be blowing at 10 km/hr for a wind turbine to effectively convert kinetic energy into electricity.
Most types of power plants can run 24 hours a day; however, wind turbines can only generate electricity when the wind is blowing. Because of this, wind turbines cannot be relied on to help meet peak electricity demand.
In Ontario, the wind blows fast enough to generate electricity an average of 20% of the time.
The graph below shows how power output from a 3 MW wind turbine varies depending on wind speed.
GENERIC MEGAWATT TURBINE
Ontario Power Generation www.opg.com/education/program.asp