BASIC KNOWLEDGE - WIND ENERGY What is wind energy? Definition, types and more
Wind provides us with a powerful, clean, and sustainable alternative energy source. In this article, we will take an in-depth look at wind energy, how it is generated, and what the future may hold for wind power.
As industries and governments across the world move away from their reliance on fossil fuels, alternative energy sources are set to become integral to the global power supply. Wind energy has the potential to transform electricity production and play a major role in the decarbonization of the energy industry.
Wind energy is the second largest source of global renewable energy production, surpassed only by hydroelectric power. Wind power is now the leading source of renewable electricity in the United States. 2021 was a record year for new wind installations in Europe with more wind farms designated for construction during 2022. Approximately 13 % of China’s electricity is now generated by wind farms. Wind power is also on the rise throughout countries such as Brazil, India, Indonesia, Japan, South Korea, Russia, the UK, and Australia.
To discover just why the world is now looking to the wind as a way to produce clean, cheap electricity, it is helpful to have a clear definition and description of wind power and how it works. In this article, we will take an in-depth look at what wind power is, how it is generated, the pros and cons of wind energy, and discuss the future of the wind energy industry.
What is wind energy?
Wind energy, or wind power, refers to the process of using the movement of air to convert it into mechanical power or electricity. Wind energy is categorized as a form of solar power because it is generated as a result of the passage of air relative to the surface of the Earth.
How does a wind turbine work?
While they are constructed using highly advanced technology and engineering techniques, the method that wind turbines use to generate electricity is quite simple. Whether we are talking about small-scale micro-turbines used to provide power for residential houses, or the gigantic structures that populate the world’s largest wind farms, all wind turbines use the same mechanical principle to produce electricity.
There are two types of wind turbines: horizontal-axis wind turbines (HAWT) and vertical-axis turbines.
The most commonplace commercial utility-scale wind turbines are horizontal-axis wind turbines. These turbines are similar to windmills and feature three blades attached to a tower. When most people think of wind energy, they picture horizontal-axis wind turbines.
There are also vertical-axis turbines that have blades attached to the top and bottom of a vertical rotor. The most typical vertical wind turbine is the Darrieus wind turbine, named for the French engineer Darrieus who invented the design in 1931. However, today these turbines are very seldom used since they do not perform as efficiently as horizontal-axis wind turbines. For that reason, we will be concentrating on the design and function of horizontal-axis wind turbines.
The blades of horizontal-axis wind turbines act much like the wings of an airplane. Wind creates lift that causes the blades to rotate. The rotation of the blades powers a drive shaft at the top of the turbine. The kinetic energy produced by the turning shaft generates DC electricity which is converted into AC electricity via a transformer and then fed into the grid from the turbine itself.
This video shows in detail how wind turbines work:
Although it depends on the manufacturer and the type of turbine, wind turbine towers are normally made from steel, which accounts for up to 79 % of the overall mass. The blades of wind turbines can be constructed from a combination of glass fiber, reinforced polyester, resin, and plastic. The main structure of a wind turbine may also contain small amounts of iron or cast iron, aluminum, and copper.
Wind turbines are usually situated in clusters across a designated area, which is then referred to as a wind farm. Wind farms can be located onshore (on land) or offshore (at sea).
Wind turbines have five major components:
The foundation: For onshore turbines, the foundation is typically a concrete block, often hidden underneath the ground. Offshore turbines located far out to sea are connected to floating foundations or foundations secured to the seabed. The foundation of the turbine must be sufficiently heavy to support the weight of the turbine itself and the force of the wind.
The tower: Towers are made of tubular steel to reduce drag and can be anywhere from 3 meters to over 110 meters tall. Towers must be at least as tall as the diameter of the spinning turbine blades and are usually two to three times the diameter of the blades. Wind speeds can increase dramatically at heights, so taller towers are subjected to stronger winds and therefore generate more electricity.
The rotor: Wind turbine blades have an aerodynamic airfoil design. Usually, although not always, a wind turbine rotor will have three blades attached to a central hub. Blades are not solid but hollow and are most commonly constructed from composite materials for maximum lightness and strength.
The movement of the rotor blades is known as blade pitch. Horizontal-axis wind turbines are fitted with hydraulic or electrical control systems that continuously adjust blade pitch to prevent the rotor speed from exceeding maximum capacity in strong winds. To prevent damage, the majority of modern wind turbines will stop rotating if the wind speed goes beyond 88.5 kilometers per hour.
The nacelle: Situated at the top of the tower, the nacelle houses the wind turbine’s electromechanical system, including the gearbox, the generator, inverters, hydraulics, bearings, and the drive train. A nacelle is fixed to a yaw bearing that allows it to revolve with the rotor to match the direction of the wind. Nacelles used on utility-scale wind turbines can contain over 1,500 separate components, be over 15 meters in length, and weigh more than 300 tons.
The generator: Wind turbine generators are situated inside the nacelle and convert the kinetic energy produced by the spinning rotor blades into electrical energy. Wind turbine generators differ from other generators as they have to cope with a source of torque that is constantly fluctuating. Because of the amount of power they produce, utility-scale wind turbine generators require cooling systems to keep them from overheating. Most often the generator is situated near a duct that uses a fan to provide cooling, but some generators are fitted with water cooling systems.
How much energy does a wind turbine produce?
Wind turbines start to produce energy once the wind speed reaches between 9.66 and 14.48 kilometers per hour. Because the wind is intermittent and wind speed does not accurately correlate to the amount of energy produced, it can be difficult to measure the output of wind turbines.
To overcome this issue, wind turbines are rated by their overall energy generating capacity. This figure is reached by dividing a turbine’s average power output by its maximum power capability. The amount of energy a wind turbine can produce is usually accepted to be anywhere between 15 to 50 % of its rated capacity. For example, a 1 MW rated wind turbine may produce 15 kW or 50 kW of electricity.
In general, a standard commercial onshore wind turbine rated between 2.5 to 3 MW can produce up to 6000 MWh per year. An offshore wind turbine of the same rating may produce double that amount.
As companies strive to build more efficient and bigger wind turbines, maximum capacity limits have greatly increased. Launched in Rotterdam, Netherlands in October 2021, General Electric’s Haliade-X was the first 14 MW turbine to begin operations. This massive turbine has a capacity factor of between 60 to 64 % of maximum output and can produce 74 GWh of electricity per year.
A range of factors come into play that can impact the rate of wind energy produced by a wind farm. Most obviously there is the fact that the wind may not always be blowing hard enough for the turbine to produce electricity. Conversely, if the wind is too fast then the turbine will shut down to avoid damage.
The location of the turbine is also a factor. Turbines placed at higher altitudes or turbines located offshore can produce significantly more power than their onshore counterparts. Lastly, the size of the tower and the rotor blades will affect how much electricity the turbine can produce.
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The different wind energy types explained
When discussing wind energy, there are two major designations:
Onshore wind energy: This describes the collections of wind turbines (wind farms) that we see placed in farmland, coastal areas near the ocean’s edge, or at high altitudes. The term onshore wind energy can also be used to describe residential wind turbines that are not connected to the main power grid.
Offshore wind energy: This designates wind turbines that are situated out to sea or in large bodies of water. Offshore wind farms are usually located in reasonably shallow water that is up to 60 meters in depth. They must be placed away from coastlines, shipping or marine traffic routes, areas that are of ecological importance, or naval installations. Offshore wind turbines can produce more electricity than onshore wind turbines because of their size and the lack of impediments to wind speed.
What are the advantages of wind power?
The expansion of the wind energy industry across the globe is due to the many advantages it has as an alternative energy source. There are considerable economic and environmental benefits to be gained from wind energy.
Since it generates electricity with no pollution, wind energy is an incredibly clean form of energy. The CO2 emissions caused by manufacturing and installing a wind turbine can be offset within the first year of operation.
Like solar power, wind energy is a completely sustainable method of producing electricity. Because wind is a non-depletable, free resource, the electricity produced by wind turbines is cheap when compared to other sources. Once installed, wind turbines have low operating costs and require minimal maintenance over their lifetime.
There are also many macro-economic benefits of wind energy. By installing wind farms, countries can lower their energy costs and become self-reliant. The wind energy industry is responsible for the creation of millions of jobs worldwide, especially in developing countries. As investment in wind farms increases, the amount of people employed by the wind industry is set to rise.
In summary, these are the main advantages of wind energy:
- Very clean form of energy
- Sustainable method of power generation
- No complex maintenance necessary
- Wind as a free resource
- Reduced energy costs for whole countries
- Wind power makes self-sufficiency possible
- Creation of numerous jobs
What are the disadvantages of wind power?
Critics point out that despite the many advantages, there are several drawbacks associated with wind energy.
One of the most commonly heard criticisms of wind farms is that they are visually unappealing and emit high levels of noise.
While the aesthetic appeal of wind farms is debatable, accusations of noise pollution aired by people who live near wind farms are being taken seriously. In March 2022, a court case in Australia ordered a wind farm to cease night-time operations due to high levels of noise emitted by wind turbines.
Wind power must still be competitive with traditional power sources in terms of cost and efficiency. Critics point out that there are many hidden costs to wind energy. Because it is difficult to estimate the output of a wind farm, and because many communities may object to a wind farm being installed, operators can find it difficult to obtain investment for projects and get local government approval for wind farm sites. Wind farms are often located in remote areas, so electricity transmission costs can be high.
The intermittent nature of wind and the availability of suitable areas for wind farms are also significant disadvantages. Wind power production in Europe was lower than expected by 15 % in 2021 due to an extreme weather event that reduced the amount of wind across the continent.
Although seen as an environmentally friendly source of energy, wind farms can have a negative impact on wildlife. There are few in-depth studies on the subject, but it has been estimated that wind farms kill as many as 100,000 birds each year in the UK and up to 328,000 in the US. The impact on other airborne species, such as bats, is unknown as is the impact that wind turbines have on local habitats for non-airborne forms of wildlife.
However, a Norwegian study found that bird deaths caused by wind turbines were reduced by 70 % simply by painting one rotor blade black. Scientists are also studying the use of ultrasonic acoustic devices to keep bats and birds away from wind farms. Research is still ongoing regarding the true environmental cost of wind farms.
In summary, these are the main disadvantages of wind energy:
- Visual landscape impairment
- Negative impact on wildlife
- High noise level
- Hidden costs
- Unsteady wind
- Difficulty in finding suitable areas
Applications of wind energy
People have been harnessing the energy of wind for centuries. In the 1st century AD, the ancient Greeks developed a windwheel to power a machine. Windmills were used extensively during the 7th to 9th century in Iran and were employed throughout Europe in the 11th century to grind grain and pump water.
The first use of wind to produce electricity was in 1887 with the creation of a wind turbine by Professor James Blyth of Glasgow. This was followed by the first US wind turbine built by Charles Brush of Ohio, and the inventions of Danish scientist Poul la Cour, who converted a windmill into a prototype power plant that provided lighting for a local village. La Cour was instrumental in rolling out over 2,500 windmills to generate electricity across Denmark and founded the Society of Wind Electricians in 1903. La Cour was also responsible for the discovery that wind turbines with fewer blades are more efficient at producing electricity.
It could be said that two events marked the beginning of the modern wind power industry. During the mid-1970s to the early 1980s, the United States government worked on producing commercial utility-scale NASA wind turbines that could provide power on an industrial basis. The other major milestone in the development of wind power was the construction of the first multi-megawatt wind turbine in 1978 by the Tvind school in Denmark.
These developments led to the world’s first modern onshore wind farm being built in Crotched Mountain in southern New Hampshire by US Windpower in 1980. The first offshore wind farm was erected in 1991 off the coast of Vindeby in Denmark by Ørsted.
10 wind energy facts at a glance
- 1. There are more than 340,000 wind farms across the globe
- 2. The cost of wind power is now 90 % lower than it was in the 1980s
- 3. The lifespan of a modern wind turbine is approximately 20 years
- 4. The wind industry employs over 1.2 million people across the world
- 5. The value of the global wind industry was estimated to be worth USD62.1 billion in 2019
- 6. China produces the most wind energy with an annual output of over 236,000 MW
- 7. China also has the world's largest wind farm - the Gansu Wind Farm
- 8. The biggest manufacturer of wind turbines is the Danish company Vestas Wind Systems A/S
- 9. The world’s largest wind turbine is the Siemens Gamesa’s SG 14-222 DD in Østerild, Denmark
- 10. It has been estimated that it would take 3.9 million turbines to provide enough power for the entire globe
Eco-energy without limits?
What does the future of wind power look like?
The ongoing development of wind turbine technology coupled with enhanced power capacity and the demand for alternative energy sources ensures that wind power will remain at the forefront of the global energy industry.
The wind energy industry is now expanding at an incredible rate and is projected to create over 3 million jobs worldwide within the next five years. The overall value of the global wind industry is expected to reach USD127.2 billion by 2027.
As the world strives to attain zero net emissions by 2050, countries are investing huge sums into new wind farms and are continuously developing wind energy technologies. Modern wind farms are becoming increasingly larger, more efficient, and capable of producing more energy than ever before.
The Siemens Gamesa’s SG 14-222 DD in Østerild, Denmark has a rotor diameter of 222 meters with 108-meter-long blades and can produce enough electricity to power 18,000 households for a year. China’s Gansu Wind Farm, also called the Jiuquan Wind Power Base, is the biggest onshore wind farm on the planet. When fully completed, the Gansu Wind Farm is expected to have 7,000 wind turbines with a planned capacity of 20 GW.
While offshore wind farms currently only supply a fraction of worldwide wind energy, their potential is vast. Offshore wind capacity factors are expected to grow exponentially with the development of floating foundation technologies. It has been reported that new technologies could see offshore wind farms adding more than 420 000 TWh per year to the global electricity supply.
To limit the impact of global warming, 180 GW of new wind energy is required worldwide each year. From 2030 onwards, it is estimated that 280 GW of new wind energy will be needed in order to meet net zero emission goals by 2050.
Can wind power provide humanity with the solution to the climate change crisis? Or are we simply tilting at windmills? With continued investment, research and development, and government support, there is a strong possibility that wind energy may become the world’s most important future energy source.