A wind turbine is a device that converts the kinetic energy of wind into electrical energy. Hundreds of thousands of large turbines, in installations known as wind farms. which is now generate over 650 gigawatts of power, with 60 GW added each year. They are an increasingly important source of intermittent renewable energy, and are used in many countries to lower energy costs and reduce reliance on fossil fuels.
In this blog, Pritish Kumar, discusses the Wind Turbine, its types, and its associated pros and cons.
Smaller wind turbines are used for applications such as battery charging for auxiliary power for boats or caravans, and to power traffic warning signs. Larger turbines can contribute to a domestic power supply while selling unused power back to the utility supplier via the electrical grid.
Wind turbines can rotate about either a horizontal or a vertical axis, the former being both older and more common. They can also include blades or be bladeless. Vertical designs produce less power and are less common.
Large three-bladed horizontal-axis wind turbines (HAWT) with the blades upwind of the tower produce the overwhelming majority of wind power in the world today. These turbines have the main rotor shaft and electrical generator at the top of a tower, and must be pointed into the wind. Small turbines are pointed by a simple wind vane, while large turbines generally use a wind sensor coupled with a yaw system. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator.
Some turbines use a different type of generator suited to slower rotational speed input. These don’t need a gearbox and are called direct-drive, meaning they couple the rotor directly to the generator with no gearbox in between. While permanent magnet direct-drive generators can be more costly due to the rare earth materials required, these gearless turbines are sometimes preferred over gearbox generators because they “eliminate the gear-speed increaser, which is susceptible to significant accumulated fatigue torque loading, related reliability issues, and maintenance costs. There is also the pseudo direct drive mechanism, which has some advantages over the permanent magnet direct drive m Vertical axis.
A vertical axis
Vertical-axis wind turbines (or VAWTs) have the main rotor shaft arranged vertically. One advantage of this arrangement is that the turbine does not need to be pointed into the wind to be effective, which is an advantage on a site where the wind direction is highly variable. It is also an advantage when the turbine is integrated into a building because it is inherently less steerable. Also, the generator and gearbox can be placed near the ground, using a direct drive from the rotor assembly to the ground-based gearbox, improving accessibility for maintenance. However, these designs produce much less energy averaged over time, which is a major drawback.
Vertical turbine designs have much lower efficiency than standard horizontal designs. The key disadvantages include the relatively low rotational speed with the consequential higher torque and hence higher cost of the drive train, the inherently lower power coefficient, the 360-degree rotation of the aero foil within the wind flow during each cycle and hence the highly dynamic loading on the blade, mechanism.
Wind turbines convert wind energy to electrical energy for distribution. Conventional horizontal axis turbines can be divided into three components:
1)The rotor, which is approximately 20% of the wind turbine cost, includes the blades for converting wind energy to low-speed rotational energy.
2)The generator, which is approximately 34% of the wind turbine cost, includes the electrical generator, the control electronics, and most likely a gearbox ,adjustable-speed drive, or continuously variable transmission component for converting the low-speed incoming rotation to high-speed rotation suitable for generating electricity.
3)The surrounding structure, which is approximately 15% of the wind turbine cost, includes the tower and rotor yaw mechanism.
A 1.5 (MW) wind turbine of a type frequently seen in the United States has a tower 80 meters (260 ft) high. The rotor assembly (blades and hub) weighs 22,000 kilograms (48,000 lb). The nacelle, which contains the generator, weighs 52,000 kilograms (115,000 lb). The concrete base for the tower is constructed using 26,000 kilograms (58,000 lb) reinforcing steel and contains 190 cubic meters (250 cu yd) of concrete. The base is 15 meters (50 ft) in diameter and 2.4 meters (8 ft) thick near the center.
Comparison with fossil-fuel turbines
Wind turbines produce electricity at between two and six cents per kilowatt hour, which is one of the lowest-priced renewable energy sources. As technology needed for wind turbines continued to improve, the prices decreased as well. In addition, there is currently no competitive market for wind energy, because wind is a freely available natural resource, most of which is untapped. The main cost of small wind turbines is the purchase and installation process, which averages between $48,000 and $65,000 per installation. The energy harvested from the turbine will offset the installation cost, as well as provide virtually free energy for years.
Wind turbines provide a clean energy source, use little water, emitting no greenhouse gases and no waste products during operation. Over 1,400 tonnes (1,500 short tons) of carbon dioxide per year can be eliminated by using a one-megawatt turbine instead of one megawatt of energy from a fossil fuel.
Wind turbines can be very large, reaching over 140 m (460 ft) tall and with blades 55 m (180 ft) long, and people have often complained about their visual impact.
Environmental impact of wind power includes effect on wildlife, but can be mitigated if proper monitoring and mitigation strategies are implemented. Thousands of birds, including rare species, have been killed by the blades of wind turbines, though wind turbines contribute relatively insignificantly to anthropogenic avian mortality. Wind farms and nuclear power plants are responsible for between 0.3 and 0.4 bird deaths per gigawatt-hour (GWh) of electricity while fossil fueled power stations are responsible for about 5.2 fatalities per GWh. In 2009, for every bird killed by a wind turbine in the US, nearly 500,000 were killed by cats and another 500,000 by buildings.