The power of the wind has been utilized for at least 3000 years. It is known that the Persians used vertical axis wind turbines during 700BC . The earliest windmills had vertical axis. The first details about horizontal axis windmills are found in historical documents from Persia, Tibet and China from about 1000 AD. In Europe, windmill performance is continuously improved between the 12th and 19th centuries.
Wind energy is one of the most important and reliable energy sources among the renewable energy sources. Wind power generation has known a remarkably rapid growth in the past 20 years, and now it is a mature, reliable and efficient technology for electricity production.With increasing significance of environmental problems, clean energy generation becomes essential in every aspect of energy consumption. With government policies and incentives throughout the world supporting the rapid construction of renewable generation facilities, the renewable share of world generation increases from 18% in 2007 to 23% in 2035
it generates electricity, but does not release any harmful pollutants or gases as by products.Wind energy does not involve the use of any fossil fuels or non-renewable sources of energy .Wind is a never-ending resourceWind energy is also one of the cheapest forms of energy available today .Each MW of wind power development provides 3 jobs years of employment. Wind also benefits the economy by reducing "hidden costs" resulting from air pollution and health care.
The number of installed wind power plants is increasing every year and many nations have made plans to make large investments wind power in the near future . Over the last decade, interest in wind power has increased dramatically in many countriessuch as Denmark, Spain, Germany, United States, and India
by the end of 2010, 2,946 MW of offshore wind capacity in 45 wind farms spread across nine countries were feeding an estimated 10.6 TWh of electricity into the European grid. Since the beginning of the decade, new offshore wind capacity has been going online every year. In 2001 the 50.5 MW of installed offshore capacity represented 1% of total new European annual wind capacity, the 883 MW installed in 2010 represented 9.5% of the annual European wind energy market
In the day, the air over land heats quicker than the air over water. The warm air over the land expands and rises, and the cooler air, which is heavier, takes its place, creating wind. In the night, the wind’s direction is reversed because the air cools quicker over land than over water.This is called the daily wind cycle.
Created by differences in air pressures.Flows from areas of high pressure to areas of low pressure.Near equator and pole surfaces winds are weak. Near surface winds occur by pressure gradients and these gradients cause to temperature gradients, which lead to strong winds
Anemometer: Measures the wind speed Blades: Most turbines have either two or three blades. Brake: can be to stop the rotor in emergencies. Controller: The controller starts up the machine at wind speeds of about 8 to 16 miles per hour (mph) and shuts off the machine at about 55 mphGear box: Gears connect the low-speed shaft to the high-speed shaft and increase the rotational speeds from about 30 rpm to 1800 rpm.Generator: Usually an off-the-shelf induction generator that produces 60-cycle AC electricity.High-speed shaft: Drives the generator.Nacelle: The nacelle sits a top the tower and contains the gear box, low- and high-speed shafts, generator, controller, and brake.Pitch: keep the rotor from turning in winds.Rotor: The blades and the hub together are called the rotor.Tower: Because wind speed increases with height, taller towers enable turbines to capture more energy and generate more electricity. Yaw drive: The yaw drive is used to keep the rotor facing into the wind as the wind direction changes.
Throughout the past 20 years, average wind turbine ratings have grown almost linearly.with each new generation of wind turbines ,the size has grown along the linear curve and has achieved reductions in life-cycle cost of energyFigure shows aVestas V-80 2.0-MW windturbine superimposed on aBoeing 747 JUMBO JET
A major difference between onshore and offshore wind farms is the relative complexity and cost of civil works, especially the substructures required for offshore turbines.The size and water-depth constraints of manufacturing, transporting and installing wind turbines are vital factors in determining the current techno-economic limitations of offshore wind farms.
Monopiles Substructure design : A monopile foundation consists of a single steel pile which is embedded into the sea bed.Typically, the turbine tower is mounted onto the foundation via a transition piece which itself is fixed on to the pile using a specialized grouted joint. A disadvantage of the monopile is that is becomes less stable in deeper waters, and is best suited to water depths of up to 25 meters. Gravity-based structures : They are designed to avoid tensile or uplift forces between the bottom of the support structure and the seabed. Gravity structures are usually competitive when the environmental loads are relatively modest. This type of structure is currently suited for sites in water depths up to 30 meters.their weight is increased by filling the structure with pumped-in sand,concrete, rock or iron ore as required
Tripods: The tripod is a standard three-legged structure made of cylindrical steel tubes. This type of structure is well suited for sites ranging in water depth from 20 to 50 m.Tri-piles: Tri-piles consist of three foundation piles connected via a transition piece to the turbine tower with the transition piece located above the water level. Jackets:they consist of a larger plan area through the majority of the structure,positioning the steel further from the center of the axis, which results in significant material savings.
The planetary boundary layer (PBL), is the lowest part of the atmosphere and its behavior is directly influenced by its contact with a planetary surface. Above the PBL is the "free atmosphere" where the wind is approximately geostrophic (parallel to the isobars) while within the PBL the wind is affected by surface drag and turns across the isobars.The PBL is covered by a layer of warmer air, creating what is known as a temperature inversion . The boundary between the cooler PBL below and the warmer layer above can be visually marked by the base of the clouds in the area.
Above the PBL, the wind speed is much more uniform and stronger due to a marked decrease in friction Above the PBL the wind is approximately geostrophic (parallel to the isobars)During the day, the air within the PBL is thoroughly mixed by convection induced by the heating of Earth’s surface, and the very top of the PBL is an entrainment zone characterized by sporadic and weakening turbulence.PGF points at a right angle to the local isobar or height contour line. It also points from high pressure to low pressure (or high heights to low heights).The closer the isobars or height contours, the greater the PGF magnitude.
An 'ideal' location for a wind turbine would have a near constant flow of non-turbulent wind throughout the year and would not suffer too many sudden powerful bursts of wind. An important turbine siting factor is access to local demand or transmission capacity. The wind blows faster at higher altitudes because of the reduced influence of drag of the surface (sea or land) and the reduced viscosity of the air.Wind farms or wind parks often have many turbines installed. Since each turbine extracts some of the energy of the wind, it is important to provide adequate spacing between turbines to avoid excess energy loss.
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Advanced and Alternative Energy Systems LVA302.064 Wind Energy Saeid Samiei Yeganeh 1029575 Student of Vienna University of Technology Study of literature for the Department of Mechanical Engineering,Institute for Energy Systems and Thermodynamics
Content :*The wind energy utilization in the world.*The development of offshore wind power.*Mechanism of wind creation*Influence of planetary boundary layer.*Overview about global wind energy markets*The various turbines technology*Substructures for offshore wind frams
Historical backgroundThe power of the wind has beenutilized for at least 3000 years.Sails were used to drive a mill stoneFor the grinding of grain.It is known that the Persians usedvertical axis wind turbines during700BC.The earliest windmills had verticalaxis.In Europe, windmill performance iscontinuously improved between the12th and 19th centuries.
Why wind Energy ?With increasing significance of environmentalproblems, clean energy generation becomes essentialin every aspect of energy consumption.It is well known that wind energy is one of the cleanestand most environmentally friendly energy sources, andunlike fossil fuels, the wind will never be depleted.All forms of energy production have an environmentalimpact, but the impacts of wind energy are low, local,and manageable.
Pros of Wind Energy It is clean source of energy it is an efficient renewable energy Wind is a never-ending resource cheapest forms of energy Economic Benefits
Cons of Wind Energy turbines can get damaged it does not eliminate electricity problems completely Noise the production of electricity depending upon the speed of the wind Bird and Mortality Location
Global wind energy production capacityThe number of installed wind power plants is increasingevery year and many nations have made plans to makelarge investments wind power in the near future . Overthe last decade, interest in wind power has increaseddramatically in many countries such asDenmark, Spain, Germany, United States, and India
Development of offshore wind power in Europeby the end of 2010, 2,946 MW of offshorewind capacity in 45 wind farms spreadacross nine countries were feeding an estimated10.6 TWh of electricity into the European grid.In 2001 the 50.5 MW of installed offshorecapacity represented 1% of total new European annual wind capacity, the 883 MW installedin 2010 represented 9.5% of the annual Europeanwind energy market
How Wind is Created ?In the day, the air over land heats quickerthan the air over water. The warm air overthe land expands and rises, and the coolerair, which is heavier, takes its place, creatingwind. In the night, the wind’s direction isreversed because the air cools quicker overland than over water.
WindCreated by differencesin air pressures.Flows from areas ofhigh pressure to areasof low pressure.Near equator and pole surfaces winds are weak.Near surface winds occur by pressure gradientsand these gradients cause to temperaturegradients, which lead to strong winds
Parts of a wind turbine Anemometer Blades Brake Controller Gear box Generator Shaft Nacelle Pitch Rotor Tower Yaw drive
How Big is a 2.0 MW Wind Turbine?Throughout the past 20 years, average windturbine ratings have grown almost linearly.with each new generation of wind turbines,the size has grown along the linear curveand has achieved reductions in life-cyclecost of energy
Different Substructures for offshore wind farmsA major difference betweenonshore and offshore wind farmsis the relative complexity and costof civil works, especially thesubstructures required foroffshore turbines.The size and water-depthconstraints ofmanufacturing, transporting andinstalling wind turbines are vitalfactors in determining the currenttechno-economic limitations ofoffshore wind farms.
Monopiles Substructure designA monopile foundation consists of asingle steel pile which is embedded intothe sea bed.Typically, the turbine tower is mountedonto the foundation via a transitionpiece which itself is fixed on to the pileusing a specialized grouted joint. Gravity-based structuresThey are designed to avoid tensile oruplift forces between the bottom of thesupport structure and the seabed.Gravity structures are usuallycompetitive when the environmentalloads are relatively modest.
Space frame structuresFor deeper locations, space framestructures are likely to be considered Tripods: The tripod is a standard three-legged structure made of cylindrical steel tubes. Tri-piles: Tri-piles consist of three foundation piles connected via a transition piece to the turbine tower with the transition piece located above the water level. Jackets: they consist of a larger plan area through the majority of the structure
planetary boundary layer (PBL)It is the lowest part of the atmosphere and itsbehavior is directly influenced by its contact with aplanetary surface. In this layer physical quantities isstrong.The PBL is covered by a layer of warmer air, creatingwhat is known as a temperature inversion .
Abovethe PBL, the wind speed is much more uniform and stronger due to a marked decrease in friction Abovethe PBL the wind is approximately geostrophic (parallel to the isobars)
An ideal location for a wind turbine wouldhave a near constant flow of non-turbulentwind throughout the year and would notsuffer too many sudden powerful bursts ofwind. An important turbine siting factor isaccess to local demand or transmissioncapacity.