Study of modeling & analysis of wind turbine

Study of Modeling & Analysis of Wind Turbine

1. Introduction:

1.1 General: Bangladesh is a least developed country. The area of this country is 1,47,570 square kilometer and population is 1.44 million. Bangladesh is mainly an agrarian country. The industrialization process of this country is increasing rapidly in present. There is no alternative of industrialization for the economic development of Bangladesh. Modernization of agricultural sector is necessary for obtaining the food security as such. And for these types of activities continuous supply of good quality electricity is very essential. But the lack of electricity in Bangladesh has come to an alarming state. The expected development in Bangladesh is hampering due to a huge gap between production capacities in response to demand. Bangladesh must have to solve her electricity problem to become a technologically advanced and food secured economically solvent developed country. As a result, besides meeting increasing electricity demand, new employment will be created; unemployment problem will be solved and will turn into an agriculturally self dependent and industrially developed country. By this means economic freedom of our country will be achieved.

The ice in the arctic regions is melting because of temperature rise which is caused by emission of green house gases. As a result, the sea level is also rising and the coastal low

lying countries will probably disappear in the sea in future. Besides this due to this climate change the frequency of natural calamities has also increased. The human being has also come under considerable threat of extinction. For the sake of sustainable economic development of agricultural, industrial and other sectors in this aspect, all the activities must be environmental friendly. So, to produce electricity environmental consequences of it must be considered. The power plant of Bangladesh is currently using fossil fuel for generating electricity. Bangladesh is not rich in mineral resources. Although coal and gas mine has been discovered here but these are not plenty. Most of the power plant of Bangladesh use gas. The coal driven power plant is also found in Bangladesh. The petroleum reserve has not been discovered so far in Bangladesh. So, to operate power plant depended on petroleum huge foreign currency is expensed to import those petroleum from abroad. So, the production cost of electricity has increased substantially. The impact of this is felt in our socio-economic life.

Bangladesh has one water driven power plant. This power plant has developed by building a dam in Kaptai Lake. A vast land area has become submerged and biodiversity lost after construction of this plant due to the rise of water level in the lake. Moreover, the power plant is old enough to produce expected amount of electricity. Some of its units have collapsed.

Some of it has completely lost its productivity. So, this power plant is not able to produce expected amount of electricity.

It is now essential to establish new power plants to meet the increasing demands. Although, the establishment of contemporary power plant require less time and money, to keep it running and considering the fuel cost high the long term cost for electricity production remain high. The fuel used in this purpose is harmful to environment. So, technologically advanced countries of the world are giving importance to establish wind turbine power plant as an alternative means for producing electricity in an average scale. The advantage of this is to produce average amount of electricity in a average scale.

Although primary establishment cost of this type of power plant is huge but to produce electricity in the long run power production cost is comparatively lower. Environmental pollution is also becomes less. The longevity of this power plant is more than other types of power plants and fuel cost gets zero. The production capacity is average. To take all the things into consideration, the necessity to establish a wind turbine power plant in Bangladesh is very much. This type of power plant can be able to meet the demand for electricity for long time. The safe usage of wind turbine power can play an important role in the socio-economic development of Bangladesh.

1.1 Objectives: Knowledge about the problem and prospect of the power sector of Bangladesh can be gained through this thesis. * To get concept on conventional power plants. * To become aware about the problem of generating power through these conventional power plants. * To get knowledge of the advantages and disadvantages of conventional power plants. *To get knowledge on wind turbine power plant. * To get knowledge of the advantages and disadvantage of wind turbine power plant.

* To get knowledge on the prospect of wind turbine power plant in the context of Bangladesh.

The proposals for solving the power problem in the context of Bangladesh for sustainable environmental friendly development.

2. Power generation: Electricity generation is the process of generating electric energy from other forms of energy.

The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday. His basic method is still used today: electricity is generated by the movement of a loop of wire, or disc of copper between the poles of a magnet.

For electric utilities, it is the first process in the delivery of electricity to consumers. The other processes, electricity transmission, distribution, and electrical power storage and recovery using pumped storage methods are normally carried out by the electric power industry.

Electricity is most often generated at a power station by electromechanical generators, primarily driven by heat engines fueled by chemical combustion or nuclear fission but also by other means such as the kinetic energy of flowing water and wind. There are many other technologies that can be and are used to generate electricity such as solar photovoltaic’s and geothermal power.

2.1 Methods of generating electricity: There are seven fundamental methods of directly transforming other forms of energy into electrical energy: * Static electricity, from the physical separation and transport of charge (examples: turboelectric effect and lightning) * Electromagnetic induction, where an electrical generator, dynamo or alternator transforms kinetic energy (energy of motion) into electricity, this is most used form for generating electricity, it is based on Faraday's law, can be experimented by simply rotating a magnet within closed loop of a conducting material (e.g. Copper wire) * Electrochemistry, the direct transformation of chemical energy into electricity, as in a battery, fuel cell or nerve impulse * Photoelectric effect, the transformation of light into electrical energy, as in solar cells * Thermoelectric effect, direct conversion of temperature differences to electricity, as in thermocouples, thermopiles, and Thermionic converters. * Piezoelectric effect, from the mechanical strain of electrically anisotropic molecules or crystals

* Nuclear transformation, the creation and acceleration of charged particles (examples: beta voltaic or alpha particle emission) Static electricity was the first form discovered and investigated, and the electrostatic generator is still used even in modern devices such as the Van de Graff generator and MHD generators. Charge carriers are separated and physically transported to a position of increased electric potential.

Almost all commercial electrical generation is done using electromagnetic induction, in which mechanical energy forces an electrical generator to rotate. There are many different methods of developing the mechanical energy, including heat engines, hydro, wind and tidal power.

The direct conversion of nuclear potential energy to electricity by beta decay is used only on a small scale. In a full-size nuclear power plant, the heat of a nuclear reaction is used to run a heat engine. This drives a generator, which converts mechanical energy into electricity by magnetic induction.

Most electric generation is driven by heat engines. The combustion of fossil fuels supplies most of the heat to these engines, with a significant fraction from nuclear fission and some from renewable sources. The modern steam turbine (invented by Sir Charles Parsons in 1884) currently generates about 80 percent of the electric power in the world using a variety of heat sources.

3. Source of energy: 3.1 Renewable energy: Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable (naturally replenished). About 16% of global final energy consumption comes from renewable, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from hydroelectricity. New renewable (small hydro, modern biomass, wind, solar, geothermal, and bio fuels) accounted for another 3% and are growing very rapidly. The share of renewable in electricity generation is around 19%, with 16% of global electricity coming from hydroelectricity and 3% from new renewable.

Wind power is growing at over 20% annually, with a worldwide installed capacity of 238,000megawatts (MW) at the end of 2011, and is widely used in Europe, Asia, and the United.[5] Since 2004, photovoltaic’s passed wind as the fastest growing energy source and since 2007 has more than doubled every two years. At the end of 2011 the photovoltaic (PV) capacity worldwide was 67,000 MW, and PV power stations are popular in Germany and Italy. Solar thermal power stations operate in the USA and Spain, and the largest of these is the 354 MW SEGS power plant in the Mojave Desert. The world's largest geothermal power installation is the Geysers in California, with a rated capacity of 750 MW. Brazil has one of the largest renewable energy programs in the world, involving production of ethanol fuel from sugarcane, and ethanol now provides 18% of the country's automotive fuel. Ethanol fuel is also widely available in the USA.While many renewable energy projects are large-scale, renewable technologies are also suited to rural and remote areas, where energy is often crucial in human development. As of 2011, small solar PV

systems provide electricity to a few million households, and micro-hydro configured into mini-grids serves many more. Over 44 million households use biogas ade in household-scale digesters for lighting and/or cooking, and more than 166 million households rely on a new generation of more-efficient biomass cook stoves. United' Secretary-General Ban Kimoon has said that renewable energy has the ability to lift the poorest nations to new levels of prosperity.

Climate change concerns, coupled with high oil prices, peak oil, and increasing government support, are driving increasing renewable energy legislation, incentives and commercialization. New government spending, regulation and policies helped the industry weather the global financial crisis better than many other sectors. According to a 2011 projection by the International Energy Agency, solar power generators may produce most of the world’s electricity within 50 years, dramatically reducing the emissions of greenhouse gases that harm the environment.

3.2 Main stream from of renewable energy: 3.2.1 Wind power: Airflows can be used to run wind turbines. Modern wind turbines range from around 600 kW to 5 MW of rated power, although turbines with rated output of 1.5–3 MW have become the most common for commercial use; the power output of a turbine is a function of the cube of the wind speed, so as wind speed increases, power output increases dramatically. [20] Areas where winds are stronger and more constant, such as offshore and high altitude sites are preferred locations for wind farms. Typical capacity factors are 20-40%, with values at the upper end of the range in particularly favorable sites.

Globally, the long-term technical potential of wind energy is believed to be five times total current global energy production, or 40 times current electricity demand. This could require wind turbines to be installed over large areas, particularly in areas of higher wind resources.

Offshore resources experience average wind speeds of ~90% greater than that of land, so offshore resources could contribute substantially more energy.

Fig: 1.1 Wind Turbine Power Plant 3.2.2 Hydropower: Energy in water can be harnessed and used. Since water is about 800 times denser than air, even a slow flowing stream of water, or moderate sea swell, can yield considerable amounts of energy. There are many forms of water energy: * Hydroelectric energy is a term usually reserved for large-scale hydroelectric dams.

Examples are the Grand Coulee Dam in Washington State and the Akosombo Dam in Ghana. * Micro hydro systems are hydroelectric power installations that typically produce up to 100 kW of power. They are often used in water rich areas as a remote-area power supply (RAPS). * Run-of-the-river hydroelectricity systems derive kinetic energy from rivers and oceans without using a dam.

Fig: 1.2 Hydro Electric Power Plants 3.2.3 Solar energy: Solar energy is the energy derived from the sun through the form of solar radiation. Solar powered electrical generation relies on photovoltaic’s and heat engines. A partial list of other solar applications includes space heating and cooling through solar architecture, delighting, solar hot water, solar cooking, and high temperature process heat for industrial purposes.

Fig: 1.3 Solar Power Plants Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air.

3.2.4 Biomass: Biomass (plant material) is a renewable energy source because the energy it contains comes from the sun. Through the process of photosynthesis, plants capture the sun's energy. When the plants are burnt, they release the sun's energy they contain. In this way, biomass functions as a sort of natural battery for storing solar energy. As long as biomass is produced sustainably, with only as much used as is grown, the battery will last indefinitely.

In general there are two main approaches to using plants for energy production: growing plants specifically for energy use (known as first and third-generation biomass), and using the residues (known as second-generation biomass) from plants that are used for other things.

See biobased economy. The best approaches vary from region to region according to climate, soils and geography.

3.2.5 Biofuel: Biofuels include a wide range of fuels which are derived from biomass. The term covers solid biomass, liquid fuels and various biogases. liquid biofuels include bioalcohols, such as bioethanol, and oils, such as biodiesel. Gaseous biofuels include biogas, landfill gas andsynthetic gas.

Bioethanol is an alcohol made by fermenting the sugar components of plant materials and it is made mostly from sugar and starch crops. With advanced technology being developed, cellulosic biomass, such as trees and grasses, are also used as feedstock’s for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form, but it is usually used as a gasoline additive to increase octane and improve vehicle emissions. Bioethanol is widely used in the USA and in Brazil.

Biodiesel is made from vegetable oils, animal fats or recycled greases. Biodiesel can be used as a fuel for vehicles in its pure form, but it is usually used as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from diesel-powered vehicles.

Biodiesel is produced from oils or fats using transesterification and is the most common biofuel in Europe. Biofuels provided 2.7% of the world's transport fuel in 2010.

3.3 Non-renewable energy: A non-renewable resource is a natural resource which cannot be reproduced, grown, generated, or used on a scale which can sustain its consumption rate, once depleted there is no more available for future needs. Also considered non-renewable are resources that are consumed much faster than nature can create them. Fossil fuels (such as coal, petroleum, and natural gas), nuclear power(uranium) and certain aquifers are examples. Metals are prime examples of non-renewable resources. In contrast, resources such as timber (when harvested sustainably) are considered renewable resources.

3.4 Main stream from of non-renewable energy: 3.4.1 Fossil fuel: Natural resources such as coal, petroleum (crude oil) and natural gas take thousands of years to form naturally and cannot be replaced as fast as they are being consumed. Eventually natural resources will become too costly to harvest and humanity will need to find other sources of energy.

At present, the main energy source used by humans are non-renewable fossil fuels, as a result of continual use since the first internal combustion engine in the 17th century, the fuel is still in high demand with conventional infrastructure and transport which are fitted with the combustion engine. The continual use of fossil fuels at the current rate will increase global warming and cause more severe climate change.

Fig: 1.4 Coal Mine 3.4.2 Radioactive fuel: The use of nuclear technology requires a radioactive fuel. Uranium ore is present in the ground at relatively low concentrations and mined in 19 countries. The uranium resource is used to create plutonium,uranium-238 is fissionable and is transmuted into fissileplutonium-

239 in a reactor. Nuclear fuel is used for the production of nuclear weapons and in nuclear power stations to create electricity.

Nuclear power provides about 6% of the world's energy and 13–14% of the world's electricity. The expense of the nuclear industry remains predominantly reliant on subsidies and indirect insurance subsidies to continue. Nuclear technology is a volatile and contaminating source of fuel production, with elements that are unstable and each decays radioactively into other elements. Nuclear power facilities produce about 200,000 metric tons of low and intermediate level waste (LILW) and 10,000 metric tons of high level waste (HLW) (including spent fuel designated as waste) each year worldwide.

The use of nuclear fuel and the radioactive waste the nuclear industry collects is highly hazardous to people and wildlife. Radio contaminants in the environment become bio accumulative by entering the chain, internal or external exposure causesmutagenic DNA breakage, producing teratogenic generational birth defects, cancers and other damages. The United Nations (UNSCEAR) estimated in 2008 that average annual human radiation exposure includes 0.01 mSv (milli-Sievert) from the legacy of past atmospheric nuclear testing plus the Chernobyl disaster and the nuclear fuel cycle, along with 2.0 mSv from natural radioisotopes and 0.4 mSv from cosmic rays; all exposures vary by location. Some radioisotopes in nuclear waste emit harmful radiation for the prolonged period of 4.5 billion years or more, and storage has risks of containment. The storage of waste, health implications and dangers of radioactive fuel continue to be a topic of debate, resulting in a controversial and unresolved industry.

The nuclear fuel cycle, unlike burning fossil fuels, produces carbon dioxide emissions from production, construction and transport, between being mined, milled, enriched, formed into fuel rods, used in the power station, then stored or reprocessed, including nuclear decommissioning and management of nuclear waste, all these actions produce carbon emissions contributing significantly to global warming.

3.4.3 Reciprocating engines: Small electricity generators are often powered by reciprocating engines burning diesel, biogas or natural gas. Diesel engines are often used for back up generation, usually at low voltages.

However most large power grids also use diesel generators, originally provided as emergency back up for a specific facility such as a hospital, to feed power into the grid during certain circumstances. Biogas is often combusted where it is produced, such as a landfill or wastewater treatment plant, with a reciprocating engine or a micro turbine, which is a small gas turbine.

A coal-fired power plant in Laughlin, Nevada U.S.A. Owners of this plant ceased operations after declining to invest in pollution control equipment to comply with pollution regulations.

3.4.4 Photovoltaic panels: Unlike the solar heat concentrators mentioned above, photovoltaic panels convert sunlight directly to electricity. Although sunlight is free and abundant, solar electricity is still usually more expensive to produce than large-scale mechanically generated power due to the cost of the panels. Low-efficiency silicon solar cells have been decreasing in cost and multifunction

cells with close to 30% conversion efficiency are now commercially available. Over 40% efficiency has been demonstrated in experimental systems. [7] Until recently, photovoltaics were most commonly used in remote sites where there is no access to a commercial power grid, or as a supplemental electricity source for individual homes and businesses. Recent advances in manufacturing efficiency and photovoltaic technology, combined with subsidies driven by environmental concerns, have dramatically accelerated the deployment of solar panels. Installed capacity is growing by 40% per year led by increases in Germany, Japan, California and New Jersey.

Fig: 1.5 Solar or Photovoltaic Power Plants 3.5 Other generation methods: Wind-powered turbines usually provide electrical generation in conjunction with other methods of producing power.

Various other technologies have been studied and developed for power generation. Solidstate generation (without moving parts) is of particular interest in portable applications. This area is largely dominated by thermoelectric (TE) devices, though thermionic (TI) and thermo photovoltaic (TPV) systems have been developed as well. Typically, TE devices are used at lower temperatures than TI and TPV systems. Piezoelectric devices are used for power generation from mechanical strain, particularly in power harvesting. Beta voltaic are another type of solid-state power generator which produces electricity from radioactive decay. Fluidbased magneto hydrodynamic (MHD) power generation has been studied as a method for extracting electrical power from nuclear reactors and also from more conventional fuel combustion systems. Osmotic power finally is another possibility at places where salt and sweet water merges (e.g. deltas ...). Modern innovation now allows kinetic energy to be generated by simply walking on floor tiles that have energy harvesting sensors embedded within them, thus producing renewable electricity.

Electrochemical electricity generation is also important in portable and mobile applications.

Currently, most electrochemical power comes from closed electrochemical cells ("batteries"), which are arguably utilized more as storage systems than generation systems, but open electrochemical systems, known as fuel cells, have been undergoing a great deal of research and development in the last few years. Fuel cells can be used to extract power either from natural fuels or from synthesized fuels (mainly electrolytic hydrogen) and so can be viewed as either generation systems or storage systems depending on their use.

3.6 Other sources of energy: Other power stations use the energy from wave or tidal motion, wind, sunlight or the energy of falling water, hydroelectricity. These types of energy sources are called renewable energy.

Fig: 1.6 A hydroelectric dam A hydroelectric dam and plant on the Muskegon river in Michigan, United States.

3.6.1 Hydroelectricity: Dams built to produce hydroelectricity impound a reservoir of water and release it through one or more water turbines, connected to generators, and generate electricity, from the energy provided by difference in water level upstream and downstream.

3.6.2 Pumped storage: A pumped-storage hydroelectric power plant is a net consumer of energy but can be used to smooth peaks and troughs in overall electricity demand. Pumped storage plants typically use "spare" electricity during off peak periods to pump water from a lower reservoir or dam to an upper reservoir. Because the electricity is consumed "off peak" it is typically cheaper than power at peak times. This is because the "base load" power stations, which are typically coal fired, cannot be switched on and off quickly so remain in service even when demand is low.

During hours of peak demand, when the electricity price is high, the water pumped to the high reservoir is allowed to flow back to the lower reservoir through a water turbine connected to an electricity generator. Unlike coal power stations, which can take more than 12 hours to start up from cold, the hydroelectric plant can be brought into service in a few minutes, ideal to meet a peak load demand. Two substantial pumped storage schemes are in South Africa, one to the East of Cape Town (Pelmet) and one in the Frankenberg, Natal.

3.6.3 Wind: Wind turbines can be used to generate electricity in areas with strong, steady winds, sometimes offshore. Many different designs have been used in the past, but almost all modern turbines being produced today use a three-bladed, upwind design. Grid-connected wind turbines now being built are much larger than the units installed during the 1970s, and so produce power more cheaply and reliably than earlier models. With larger turbines (on the

order of one megawatt), the blades move more slowly than older, smaller, units, which makes them less visually distracting and safer for airborne animals.

Fig: 1.7 Wind turbines in front of a thermal power station in Amsterdam, the Netherlands.

4. Power station: A power station (also referred to as a generating station, power plant, or powerhouse) is an industrial facility for the generation of electric power. At the center of nearly all power stations is a generator, a rotating machine that converts mechanical power into electrical power by creating relative motion between a magnetic field and a conductor. The energy source harnessed to turn the generator varies widely. It depends chiefly on which fuels are easily available, cheap enough and on the types of technology that the power company has access to.

Central power stations produce AC power, after a brief Battle of Currents in the 19th century demonstrated the advantages of AC distribution.

4.1 History: The world's first power station was built by Sigmund Schuckert in the Bavarian town of Etta and went into operation in 1878[4]. The station consisted of 24 dynamo electric generators which were driven by a steam engine. It was used to illuminate a grotto in the gardens of Linder of Palace.

The first public power station was the Edison Electric Light Station, built in London at 57, Holborn Viaduct, which started operation in January 1882. This was an initiative of Thomas Edison that was organized and managed by his partner, Edward Johnson. A Babcock and

Wilcox boiler powered a 125 horsepower steam engine that drove a 27 ton generator called Jumbo, after the celebrated elephant. This supplied electricity to premises in the area that could be reached through the culverts of the viaduct without digging up the road, which was the monopoly of the gas companies. The customers included the City Temple and the Old Bailey.

Another important customer was the Telegraph Office of the General Post Office but this could not be reached though the culverts. Johnson arranged for the supply cable to be run overhead, via Holborn Tavern and New gate. In September 1882 in New York, the Pearl Street Station was established by Edison to provide electric lighting in the lower Manhattan Island area; the station ran until destroyed by fire in 1890. The station used reciprocating steam engines to turn direct-current generators. Because of the DC distribution, the service area was small, limited by voltage drop in the feeders. The War of Currents eventually resolved in favor of AC distribution and utilization, although some DC systems persisted to the end of the 20th century. DC systems with a service radius of a mile (kilometer) or so were necessarily smaller, less efficient of fuel consumption, and more labor intensive to operate than much larger central AC generating stations.

AC systems used a wide range of frequencies depending on the type of load; lighting load using higher frequencies, and traction systems and heavy motor load systems preferring lower frequencies. The economics of central station generation improved greatly when unified light and power systems, operating at a common frequency, were developed. The same generating plant that fed large industrial loads during the day, could feed commuter railway systems during rush hour and then serve lighting load in the evening, thus improving the system load factor and reducing the cost of electrical energy overall. Many exceptions existed, generating stations were dedicated to power or light by the choice of frequency, and rotating frequency changers and rotating converters were particularly common to feed electric railway systems from the general lighting and power network.

Throughout the first few decades of the 20th century central stations became larger, using higher steam pressures to provide greater efficiency, and relying on interconnections of multiple generating stations to improve reliability and cost. High-voltage AC transmission allowed hydroelectric power to be conveniently moved from distant waterfalls to city markets. The advent of the steam turbine in central station service, around 1906, allowed great expansion of generating capacity. Generators were no longer limited by the power transmission of belts or the relatively slow speed of reciprocating engines, and could grow to enormous sizes.

For example, Sebastian Ziani de Ferranti planned what would have been the largest reciprocating steam engine ever built for a proposed new central station, but scrapped the plans when turbines became available in the necessary size. Building power systems out of central stations required combinations of engineering skill and financial acumen in equal measure. Pioneers of central station generation include George Westinghouse and Samuel Insull in the United States, Ferranti and Charles Hester man Merz in UK, and many others.

4.2 Thermal power stations: In thermal power stations, mechanical power is produced by a heat engine that transforms thermal energy, often from combustion of a fuel, into rotational energy. Most thermal power

stations produce steam, and these are sometimes called steam power stations. Not all thermal energy can be transformed into mechanical power, according to the second law of thermodynamics. Therefore, there is always heat lost to the environment. If this loss is employed as useful heat, for industrial processes or district heating, the power plant is referred to as a cogeneration power plant or CHP (combined heat-and-power) plant. In countries where district heating is common, there are dedicated heat plants called heat-only boiler stations. An important class of power stations in the Middle East uses by-product heat for the desalination of water.

Fig: 1.8 Rotor of a modern steam turbine The efficiency of a steam turbine is limited by the maximum temperature of the steam produced and is not directly a function of the fuel used. For the same steam conditions, coal, nuclear and gas power plants all have the same theoretical efficiency. Overall, if a system is on constantly (base load) it will be more efficient than one that is used intermittently (peak load).

Besides use of reject heat for process or district heating, one way to improve overall efficiency of a power plant is to combine two different thermodynamic cycles. Most commonly, exhaust gases from a gas turbine are used to generate steam for a boiler and steam turbine. The combination of a "top" cycle and a "bottom" cycle produces higher overall efficiency than either cycle can attain alone.

Fig: 1.9 CHP plant in Warsaw, Poland

Fig: 2.1 geothermal power stations in Iceland.

Fig: 2.2 Coal Power Stations in Tampa Coal Power Station in Tampa, States. Thermal power plants are classified by the type of fuel and the type of prime mover installed.

4.2.1 By fuel: * Fossil fuelled power plants may also use a steam turbine generator or in the case of natural gas-fired plants may use a combustion turbine. A coal-fired power station produces electricity by burning coal to generate steam, and has the side-effect of producing large amounts of sulfur dioxide which pollutes air and water and carbon dioxide, which contributes to global warming. About 50% of electric generation in the USA is produced by coal-fired power plants * Nuclear power plants use a nuclear reactor's heat to operate a steam turbine generator.

About 20% of electric generation in the USA is produced by nuclear power plants.

* Geothermal power plants use steam extracted from hot underground rocks. * Biomass-fuelled power plants may be fuelled by waste from sugar cane, municipal solid waste, landfill methane, or other forms of biomass. * In integrated steel mills, blast furnace exhaust gas is a low-cost, although low-energydensity, fuel. * Waste heat from industrial processes is occasionally concentrated enough to use for power generation, usually in a steam boiler and turbine. * Solar thermal electric plants use sunlight to boil water and produce steam which turns the generator.

4.2.2 Prime Mover: A machine that transforms energy from thermal, electrical or pressure form to mechanical form, typically an engine or turbine 4.2.3 By prime mover: * Steam turbine plants use the dynamic pressure generated by expanding steam to turn the blades of a turbine. Almost all large non-hydro plants use this system. About 90% of all electric power produced in the world is by use of steam turbines. * Gas turbine plants use the dynamic pressure from flowing gases (air and combustion products) to directly operate the turbine. Natural-gas fuelled (and oil fueled) combustion turbine plants can start rapidly and so are used to supply "peak" energy during periods of high demand, though at higher cost than base-loaded plants. These may be comparatively small units, and sometimes completely unmanned, being remotely operated. This type was pioneered by the UK, Prince town being the world's first, commissioned in 1959. * Combined cycle plants have both a gas turbine fired by natural gas, and a steam boiler and steam turbine which use the hot exhaust gas from the gas turbine to produce electricity. This greatly increases the overall efficiency of the plant, and many new base load power plants are combined cycle plants fired by natural gas. * Internal combustion reciprocating engines are used to provide power for isolated communities and are frequently used for small cogeneration plants. Hospitals, office buildings, industrial plants, and other critical facilities also use them to provide backup power in case of a power outage. These are usually fuelled by diesel oil, heavy oil, natural gas, and landfill gas. * Micro turbines, Sterling engine and internal combustion reciprocating engines are low-cost solutions for using opportunity fuels, such as landfill gas, digester gas from water treatment plants and waste gas from oil production.

4.2.4 Cooling towers:

Fig: 2.3 Cooling towers (Cooling towers evaporating water at Radcliffe-on-Soar Power Station, United Kingdom.)

All thermal power plants produce waste heat energy as a byproduct of the useful electrical energy produced. The amount of waste heat energy equals or exceeds the amount of electrical energy produced. Gas-fired power plants can achieve 50% conversion efficiency while coal and oil plants achieve around 30–49%. The waste heat produces a temperature rise in the atmosphere which is small compared to that of greenhouse-gas emissions from the same power plant. Natural draft wet cooling towers at many nuclear power plants and large fossil fuel-fired power plants use large hyperbolic chimney-like structures (as seen in the image at the left) that release the waste heat to the ambient atmosphere by the evaporation of water.

However, the mechanical induced-draft or forced-draft wet cooling towers in many large thermal power plants, nuclear power plants, fossil-fired power plants, petroleum refineries, petrochemical plants, geothermal, biomass and waste to energy plants use fans to provide air movement upward through down coming water and are not hyperbolic chimney-like structures. The induced or forced-draft cooling towers are typically rectangular, box-like structures filled with a material that enhances the contacting of the up flowing air and the down flowing water.

In areas with restricted water use a dry cooling tower or radiators, directly air cooled, may be necessary, since the cost or environmental consequences of obtaining make-up water for evaporative cooling would be prohibitive. These have lower efficiency and higher energy consumption in fans than a wet, evaporative cooling tower.

Where economically and environmentally possible, electric companies prefer to use cooling water from the ocean, or a lake or river, or a cooling pond, instead of a cooling tower. This type of cooling can save the cost of a cooling tower and may have lower energy costs for pumping cooling water through the plant's heat exchangers. However, the waste heat can cause the temperature of the water to rise detectably. Power plants using natural bodies of water for cooling must be designed to prevent intake of organisms into the cooling cycle. A further environmental impact would be organisms that adapt to the warmer plant water and may be injured if the plant shuts down in cold weather.

Water consumption by power stations is a developing issue.

In recent years, recycled wastewater, or grey water, has been used in cooling towers. The Calpine Riverside and the Calpine Fox power stations in Wisconsin as well as the Calpine Mankato power station in Minnesota are among these facilities.

4.3 Generator: In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge (usually carried by electrons) to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow (but does not create water). The source of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air or any other source of mechanical energy.

The reverse conversion of electrical energy into mechanical energy is done by an electric motor, and motors and generators have many similarities. Many motors can be mechanically driven to generate electricity, and frequently make acceptable generators.

4.3.1 Types of generator: Their are numerous types of generators but we'll focus on the most common fuel types: • •

Gas Generators LPG Generators

•

Diesel Generators

•

Natural Gas Generators

We'll also focus on the most common uses for generators: • Home Standby Generators • Portable Generators •

Commercial Generators

5. Turbine: 5.1.1 Wind Turbines: Wind turbines, like aircraft propeller blades, turn in the moving air and power an electric generator that supplies an electric current. Simply stated, a wind turbine is the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity.

5.1.2 Wind turbine types: • Three types based on the generating system And the way in which the aerodynamic Efficiency of the rotor is limited during high

Wind speeds • Generating systems types: 1. Squirrel cage induction generator 2. Doubly fed (wound rotor) induction Generator.

3. Direct drive synchronous generator.

5.2 Wind turbine design: Wind turbine design is the process of defining the form and specifications of a wind turbine to extract energy from the wind. A wind turbine installation consists of the necessary systems needed to capture the wind's energy, point the turbine into the wind, convert mechanical rotation into electrical power, and other systems to start, stop, and control the turbine.

This article covers the design of horizontal axis wind turbines (HAWT) since the majority of commercial turbines use this design. Contrary to popular belief, considerable attention should be given to the structural and foundation design of HAWTs. This is mainly due to the disproportionate amount that is spent on the foundations as a percentage of the total project cost.

Fig: 2.4 Turbine components 5.2.1 Turbine Components: Horizontal turbine components include: • •

blade or rotor, which converts the energy in the wind to rotational shaft energy; a drive train, usually including a gearbox and a generator;

•

a tower that supports the rotor and drive train; and

•

Other equipment, including controls, electrical cables, ground support equipment, and interconnection equipment.

5.2.2 Wind Turbine Size and Power Ratings: Wind turbines are available in a variety of sizes, and therefore power ratings. The largest machine has blades that span more than the length of a football field, stands 20 building stories high, and produces enough electricity to power 1,400 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. Utility-scale turbines range in size from 50 to 750 kilowatts. Single small turbines, below 50 kilowatts, are used for homes, telecommunications dishes, or water pumping.

5.3 Design specification: The design specification for a wind-turbine will contain a power curve and guaranteed availability. With the data from the wind resource assessment it is possible to calculate commercial viability.[1] The typical operating temperature range is -20 to 40 °C (-4 to 104 °F).

In areas with extreme climate (like Inner Mongolia or Rajasthan) specific cold and hot weather versions are required.

Wind turbines can be designed and validated according to IEC 61400 standards.

5.3.1 Low temperature: Utility-scale wind turbine generators have minimum temperature operating limits which apply in areas that experience temperatures below –20 °C. Wind turbines must be protected from ice accumulation. It can make anemometer readings inaccurate and which can cause high structure loads and damage. Some turbine manufacturers offer low-temperature packages at a few percent extra costs, which include internal heaters, different lubricants, and different alloys for structural elements. If the low-temperature interval is combined with a low-wind condition, the wind turbine will require an external supply of power, equivalent to a few percent of its rated power, for internal heating. For example, the St. Leon, Manitoba project has a total rating of 99 MW and is estimated to need up to 3 MW (around 3% of capacity) of station service power a few days a year for temperatures down to –30 °C. This factor affects the economics of wind turbine operation in cold climates.

5.3.2 Aerodynamics: The aerodynamics of a horizontal-axis wind turbine are not straightforward. The air flow at the blades is not the same as the airflow far away from the turbine. The very nature of the way in which energy is extracted from the air also causes air to be deflected by the turbine. In addition the aerodynamics of a wind turbine at the rotor surface exhibit phenomena that are rarely seen in other aerodynamic fields.

In 1919 the physicist Albert Betz showed that for a hypothetical ideal wind-energy extraction machine, the fundamental laws of conservation of mass and energy allowed no more than

16/27 (59.3%) of the kinetic energy of the wind to be captured. This Betz' law limit can be approached by modern turbine designs which may reach 70 to 80% of this theoretical limit.

5.3.3 Power control: A wind turbine is designed to produce a maximum of power at wide spectrum of wind speeds. All wind turbines are designed for a maximum wind speed, called the survival speed, above which they do not survive. The survival speed of commercial wind turbines is in the range of 40 m/s (144 km/h, 89 MPH) to 72 m/s (259 km/h, 161 MPH). The most common survival speed is 60 m/s (216 km/h, 134 MPH). The wind turbines have three modes of operation: Plastic vortex generator stripes used to control stall characteristics of the blade - in this example protecting the blade from rapid fluctuations in wind speed.

• •

Below rated wind speed operation Around rated wind speed operation (usually at nameplate capacity)

•

Above rated wind speed operation

If the rated wind speed is exceeded the power has to be limited. There are various ways to achieve this.

A control system involves three basic elements: sensors to measure process variables, actuators to manipulate energy capture and component loading, and control algorithms to coordinate the actuators based on information gathered by the sensors.

5.3.4 Pitch control: Furling works by decreasing the angle of attack, which reduces the induced drag from the lift of the rotor, as well as the cross-section. One major problem in designing wind turbines is getting the blades to stall or furl quickly enough should a gust of wind cause sudden acceleration. A fully furled turbine blade, when stopped, has the edge of the blade facing into the wind.

Loads can be reduced by making a structural system softer or more flexible. This could be accomplished with downwind rotors or with curved blades that twist naturally to reduce angle of attack at higher wind speeds. These systems will be nonlinear and will couple the structure to the flow field - thus, design tools must evolve to model these nonlinearities.

Standard modern turbines all pitch the blades in high winds. Since pitching requires acting against the torque on the blade, it requires some form of pitch angle control, which is achieved with a slewing drive. This drive precisely angles the blade while withstanding high torque loads. In addition, many turbines use hydraulic systems. These systems are usually spring-loaded, so that if hydraulic power fails, the blades automatically furl. Other turbines use an electric servomotor for every rotor blade. They have a small battery-reserve in case of an electric-grid breakdown. Small wind turbines (under 50 kW) with variable-pitching generally use systems operated by centrifugal force, either by flyweights or geometric design, and employ no electric or hydraulic controls.

Fundamental gaps exist in pitch control, limiting the reduction of energy costs, according to a report from a coalition of researchers from universities, industry, and government, supported by the Atkinson Center for a Sustainable Future. Load reduction is currently focused on fullspan blade pitch control, since individual pitch motors are the actuators currently available on commercial turbines. Significant load mitigation has been demonstrated in simulations for blades, tower, and drive train. However, there is still research needed, the methods for realization of full-span blade pitch control need to be developed in order to increase energy capture and mitigate fatigue loads.

5.3.5 Other controls: 5.3.6 Yawing: Modern large wind turbines are typically actively controlled to face the wind direction measured by a wind vane situated on the back of the nacelle. By minimizing the yaw angle (the misalignment between wind and turbine pointing direction), the power output is maximized and non-symmetrical loads minimized. However, since the wind direction varies quickly the turbine will not strictly follow the direction and will have a small yaw angle on average. The power output losses can simply be approximated to fall with cos3(yaw angle).

5.3.7 Electrical braking: Braking of a small wind turbine can also be done by dumping energy from the generator into a resistor bank, converting the kinetic energy of the turbine rotation into heat. This method is useful if the kinetic load on the generator is suddenly reduced or is too small to keep the turbine speed within its allowed limit.

Cyclically braking causes the blades to slow down, which increases the stalling effect, reducing the efficiency of the blades. This way, the turbine's rotation can be kept at a safe speed in faster winds while maintaining (nominal) power output. This method is usually not applied on large grid-connected wind turbines.

5.3.8 Mechanical braking: A mechanical drum brake or disk brake is used to hold the turbine at rest for maintenance.

Such brakes are usually applied only after blade furling and electromagnetic braking have reduced the turbine speed, as the mechanical brakes would wear quickly if used to stop the turbine from full speed. There can also be a stick brake.

5.4 Turbine size:

Fig: 2.5 a person standing beside medium size modern turbine blades.

For a given survivable wind speed, the mass of a turbine is approximately proportional to the cube of its blade-length. Wind power intercepted by the turbine is proportional to the square of its blade-length. The maximum blade-length of a turbine is limited by both the strength and stiffness of its material.

Labor and maintenance costs increase only gradually with increasing turbine size, so to minimize costs, wind farm turbines are basically limited by the strength of materials, and sitting requirements.

Typical modern wind turbines have diameters of 40 to 90 meters (130 to 300 ft) and are rated between 500 kW and 2 MW. As of 2011 the most powerful turbine Enercon_E-126 is rated at 7.5 MW. 5.4.1 Gearbox, rotor shaft and brake assembly: For large, commercial size horizontal-axis wind turbines, the generator is mounted in a nacelle at the top of a tower, behind the hub of the turbine rotor. Typically wind turbines generate electricity through asynchronous machines that are directly connected with the electricity grid. Usually the rotational speed of the wind turbine is slower than the equivalent rotation speed of the electrical network - typical rotation speeds for a wind generators are 520 rpm while a directly connected machine will have an electrical speed between 750-3600 rpm. Therefore, a gearbox is inserted between the rotor hub and the generator. This also reduces the generator cost and weight.

Older style wind generators rotate at a constant speed, to match power line frequency, which allowed the use of less costly induction generators. Newer wind turbines often turn at whatever speed generates electricity most efficiently. This can be solved using multiple technologies such as doubly fed induction generators or full-effect converters where the variable frequency current produced is converted to DC and then back to AC, matching the line frequency and voltage. Although such alternatives require costly equipment and cause power loss, the turbine can capture a significantly larger fraction of the wind energy. In some cases, especially when turbines are sited offshore, the DC energy will be transmitted from the turbine to a central (onshore) inverter for connection to the grid.

5.5 Gearless wind turbine: Commercial size generators have a rotor carrying a field winding so that a rotating magnetic field is produced inside a set of windings called the stator. While the rotating field winding consumes a fraction of a percent of the generator output, adjustment of the field current allows good control over the generator output voltage. Enercon has produced gearless wind turbines with separately excited generators for many years, and Siemens produces a gearless "inverted generator" 3MW model while developing a 6MW model.

In conventional wind turbines, the blades spin a shaft that is connected through a gearbox to the generator. The gearbox converts the turning speed of the blades 15 to 20 rotations per

minute for a large, one-megawatt turbine into the faster 1,800 rotations per minute that the generator needs to generate electricity.

Gearless wind turbines (often also called direct drive) get rid of the gearbox completely.

Instead, the rotor shaft is attached directly to the generator, which spins at the same speed as the blades.

In a turbine generator, magnets spin around a coil to produce current the faster the magnets spin, the more current is induced in the coil. To make up for a direct drive generator's slower spinning rate, the diameter of the generator's rotor is increased hence containing more magnets which lets it create a lot of power when turning slowly. To reduce the generator weight some constructors use permanent magnets (PM) in the generators' rotor, while conventional turbine generators use electromagnets copper coils fed with electricity from the generator itself. Building smaller generators with important torque is still an active research area to enhance their competitiveness.

Gearless wind turbines are often heavier than gear based wind turbines. A study by the EU called Reliawind www.reliawind.eu based on the largest sample size of turbines, has shown that the reliability of gearboxes is not the main problem in a wind turbine. Reliability of direct drive turbines offshore is still not known, since the sample size is so small.

Experts from Technical University of Denmark estimate that a geared generator with permanent magnets may use 25 kg/MW of the rare earth element Neodymium, while a gearless may use 250 kg/MW. In December 2011, the US Department of Energy published a report stating critical shortage of rare earth elements such as Neodymium used in large quantities for permanent magnets in gearless wind turbines. China produces more than 95% of rare earth elements, while Hitachi holds more than 600 patents covering Neodymium magnets. Direct-drive turbines require 600 kg of PM material per megawatt, which translates to several hundred kilograms of rare earth content per megawatt, as Neodymium content is estimated to be 31% of magnet weight.

Hybrid drive trains (intermediate between direct drive and traditional geared) use significantly less rare earth materials. While PM wind turbines only account for about 5% of the market outside of China, their market share inside of China is estimated at 25% or higher.

Demand for neodymium in wind turbines is estimated to be 1/5 of that in electric vehicles.

5.6 Blades: 5.6.1 Blade design: The ratio between the speed of the blade tips and the speed of the wind is called tip speed ratio. High efficiency 3-blade-turbines have tip speed/wind speed ratios of 6 to 7. Modern wind turbines are designed to spin at varying speeds (a consequence of their generator design, see above). Use of aluminum and composite materials in their blades has contributed to low rotational inertia, which means that newer wind turbines can accelerate quickly if the winds pick up, keeping the tip speed ratio more nearly constant. Operating closer to their optimal tip speed ratio during energetic gusts of wind allows wind turbines to improve energy capture from sudden gusts that are typical in urban settings.

In contrast, older style wind turbines were designed with heavier steel blades, which have higher inertia, and rotated at speeds governed by the AC frequency of the power lines. The high inertia buffered the changes in rotation speed and thus made power output more stable.

The speed and torque at which a wind turbine rotates must be controlled for several reasons: * To optimize the aerodynamic efficiency of the rotor in light winds. * To keep the generator within its speed and torque limits. * To keep the rotor and hub within their centrifugal force limits. The centrifugal force from the spinning rotors increases as the square of the rotation speed, which makes this structure sensitive to over speed. * To keep the rotor and tower within their strength limits. Because the power of the wind increases as the cube of the wind speed, turbines have to be built to survive much higher wind loads (such as gusts of wind) than those from which they can practically generate power. Since the blades generate more tensional and vertical forces (putting far greater stress on the tower and nacelle due to the tendency of the rotor to process and mutate when they are producing torque, most wind turbines have ways of reducing torque in high winds.

To enable maintenance. Since it is dangerous to have people working on a wind turbine while it is active, it is sometimes necessary to bring a turbine to a full stop.

To reduce noise. As a rule of thumb, the noise from a wind turbine increases with the fifth power of the relative wind speed (as seen from the moving tip of the blades). In noisesensitive environments, the tip speed can be limited to approximately 60 m/s (200 ft/s).

It is generally understood that noise increases with higher blade tip speeds. To increase tip speed without increasing noise would allow reduction the torque into the gearbox and generator and reduce overall structural loads, thereby reducing cost.[3] The reduction of noise is linked to the detailed aerodynamics of the blades, especially factors that reduce abrupt stalling. The inability to predict stall restricts the development of aggressive aerodynamic concepts.

5.7 The hub: In simple designs, the blades are directly bolted to the hub and hence are stalled. In other more sophisticated designs, they are bolted to the pitch mechanism, which adjusts their angle of attack according to the wind speed to control their rotational speed. The pitch mechanism is itself bolted to the hub. The hub is fixed to the rotor shaft which drives the generator through a gearbox. Direct drive wind turbines (also called gearless) are constructed without a gearbox. Instead, the rotor shaft is attached directly to the generator, which spins at the same speed as the blades.

5.7.1 Blade count: The NASA Mod-0 research wind turbine at Glenn Research Center's Plum Brook station in Ohio tested a one-bladed rotor configuration

The determination of the number of blades involves design considerations of aerodynamic efficiency, component costs, system reliability, and aesthetics. Noise emissions are affected by the location of the blades upwind or downwind of the tower and the speed of the rotor.

Given that the noise emissions from the blades' trailing edges and tips vary by the 5th power of blade speed, a small increase in tip speed can make a large difference.

Fig: 2.6 One-Bladed Rotors Wind turbines developed over the last 50 years have almost universally used either two or three blades. Aerodynamic efficiency increases with number of blades but with diminishing return. Increasing the number of blades from one to two yields a six percent increase in aerodynamic efficiency, whereas increasing the blade count from two to three yields only an additional three percent in efficiency. Further increasing the blade count yields minimal improvements in aerodynamic efficiency and sacrifices too much in blade stiffness as the blades become thinner.

Component costs that are affected by blade count are primarily for materials and manufacturing of the turbine rotor and drive train. Generally, the fewer the number of blades, the lower the material and manufacturing costs will be. In addition, the fewer the number of blades, the higher the rotational speed can be. This is because blade stiffness requirements to avoid interference with the tower limit how thin the blades can be manufactured, but only for upwind machines; deflection of blades in a downwind machine results in increased tower clearance. Fewer blades with higher rotational speeds reduce peak torques in the drive train, resulting in lower gearbox and generator costs.

Fig: 2.7 Two-bladed NASA/DOE Mod-5B wind turbines The 98 meter diameter, two-bladed NASA/DOE Mod-5B wind turbine was the largest operating wind turbine in the world in the early 1990s System reliability is affected by blade count primarily through the dynamic loading of the rotor into the drive train and tower systems. While aligning the wind turbine to changes in wind direction (yawing), each blade experiences a cyclic load at its root end depending on blade position. This is true of one, two, three blades or more. However, these cyclic loads when combined together at the drive train shaft are symmetrically balanced for three blades, yielding smoother operation during turbine yaw. Turbines with one or two blades can use a pivoting teetered hub to also nearly eliminate the cyclic loads into the drive shaft and system during yawing.

Finally, aesthetics can be considered a factor in that some people find that the three-bladed rotor is more pleasing to look at than a one- or two-bladed rotor.

5.8 Blade materials: Wood and canvas sails were used on early windmills due to their low price, availability, and ease of manufacture. Smaller blades can be made from light metals such as aluminum. These materials, however, require frequent maintenance. Wood and canvas construction limits the airfoil shape to a flat plate, which has a relatively high ratio of drag to force captured (low aerodynamic efficiency) compared to solid airfoils. Construction of solid airfoil designs requires inflexible materials such as metals or composites. Some blades also have incorporated lightning conductors.

New wind turbine designs push power generation from the single megawatt range to upwards of 10 megawatts using larger and larger blades. A larger area effectively increases the tipspeed ratio of a turbine at a given wind speed, thus increasing its energy extraction.

Computer-aided engineering software such as HyperSizer (originally developed for spacecraft design) can be used to improve blade design.

Current production wind turbine blades are as large as 100 meters in diameter with prototypes in the range of 110 to 120 meters. In 2001, an estimated 50 million kilograms of fiberglass laminate were used in wind turbine blades.

An important goal of larger blade systems is to control blade weight. Since blade mass scales as the cube of the turbine radius, loading due to gravity constrains systems with larger blades.

[18]

Manufacturing blades in the 40 to 50 meter range involves proven fiberglass composite fabrication techniques. Manufactures such as Nordex and GE Wind use an infusion process.

Other manufacturers use variations on this technique, some including carbon and wood with fiberglass in an epoxy matrix. Options also include prepare fiberglass and vacuum-assisted resin transfer molding. Each of these options use a glass-fiber reinforced polymer composite constructed with differing complexity. Perhaps the largest issue with more simplistic, openmold, wet systems are the emissions associated with the volatile organics released.

Preimpregnated materials and resin infusion techniques avoid the release of volatiles by containing all reaction gases. However, these contained processes have their own challenges, namely the production of thick laminates necessary for structural components becomes more difficult. As the perform resin permeability dictates the maximum laminate thickness, bleeding is required to eliminate voids and insure proper resin distribution. [17] One solution to resin distribution a partially preimpregnated fiberglass. During evacuation, the dry fabric provides a path for airflow and, once heat and pressure are applied, resin may flow into the dry region resulting in a thoroughly impregnated laminate structure.

Epoxy-based composites have environmental, production, and cost advantages over other resin systems. Epoxies also allow shorter cure cycles, increased durability, and improved surface finish. Prepare operations further reduce processing time over wet lay-up systems. As turbine blades pass 60 meters, infusion techniques become more prevalent; the traditional resin transfer molding injection time is too long as compared to the resin set-up time, limiting laminate thickness. Injection forces resin through a thicker ply stack, thus depositing the resin where in the laminate structure before gelatin occurs. Specialized epoxy resins have been developed to customize lifetimes and viscosity.

Carbon fiber-reinforced load-bearing spars can reduce weight and increase stiffness. Using carbon fibers in 60 meter turbine blades is estimated to reduce total blade mass by 38% and decrease cost by 14% compared to 100% fiberglass. Carbon fibers have the added benefit of reducing the thickness of fiberglass laminate sections, further addressing the problems associated with resin wetting of thick lay-up sections. Wind turbines may also benefit from the general trend of increasing use and decreasing cost of carbon fiber materials.

5.9 Tower:

Typically, 2 types of towers exist: floating towers and land-based towers.

5.9.1 Tower height: Wind velocities increase at higher altitudes due to surface aerodynamic drag (by land or water surfaces) and the viscosity of the air. The variation in velocity with altitude, called wind shear, is most dramatic near the surface.

Wind turbines generating electricity at the San Gorgonio Pass Wind Farm.

Typically, in daytime the variation follows the wind profile power law, which predicts that wind speed rises proportionally to the seventh root of altitude. Doubling the altitude of a turbine, then, increases the expected wind speeds by 10% and the expected power by 34%.

To avoid buckling, doubling the tower height generally requires doubling the diameter of the tower as well, increasing the amount of material by a factor of at least four.

At night time, or when the atmosphere becomes stable, wind speed close to the ground usually subsides whereas at turbine hub altitude it does not decrease that much or may even increase. As a result the wind speed is higher and a turbine will produce more power than expected from the 1/7 power law: doubling the altitude may increase wind speed by 20% to 60%. A stable atmosphere is caused by radiative cooling of the surface and is common in a temperate climate: it usually occurs when there is a (partly) clear sky at night. When the (high altitude) wind is strong (a 10-meter (33 ft) wind speed higher than approximately 6 to 7 m/s (20–23 ft/s)) the stable atmosphere is disrupted because of friction turbulence and the atmosphere will turn neutral. A daytime atmosphere is either neutral (no net radiation; usually with strong winds and/or heavy clouding) or unstable (rising air because of ground heating— by the sun). Here again the 1/7 power law applies or is at least a good approximation of the wind profile. Indiana had been rated as having a wind capacity of 30,000 MW, but by raising the expected turbine height from 50 m to 70 m, the wind capacity estimate was raised to 40,000 MW, and could be double that at 100 m.

For HAWTs, tower heights approximately two to three times the blade length have been found to balance material costs of the tower against better utilization of the more expensive active components.

In Europe, road restrictions make transportation of towers with a diameter of more than 4.3 m difficult. Swedish analyses show that it is important to have the bottom wing tip at least 30 m above the tree tops, but a taller tower requires a larger tower diameter. A tower profile made of connected shells rather than cylinders can have a larger diameter and still be transportable.

A 100 m prototype tower with TC bolted 18mm 'plank' shells has been erected at the wind turbine test center Høvsøre in Denmark and certified by Det Norske VERITAS, with a Siemens nacelle. Shell elements can be shipped in standard 40 foot containers.

5.10 Blade construction: 5.10.1 Steps in the wind rotor construction procedure:

1. Choose a design for the blades, and make templates from paper or thin aluminum sheet.

Copy the drawings in Appendix II for the templates. The templates will fit the outside of the blades Exactly.

2. Use these templates to make a three dimensional pattern in the shape of the actual Blade. One can carve a pattern from wood. Or metal sheet or foam could be used Instead.

3. Around the pattern, cast fiberglass moulds. We might make enough moulds for a Full set of blades for one rotor (three moulds for a three bladed rotor).

4. Use the moulds to make the blades.

5. Make a hub for the blades and assemble the rotor.

If the production teams have no experience with fiberglass resin, they may need to ask an expert for help.

We will need to test the strength of the blades, and balance them, so they will be safe and run smoothly.

5.10.2 The two rotor designs: Here are the main features of the two rotor designs described in this Booklet: - SECTION the ‘blade section’ is the shape of the blade in cross-section (cut at 90 degrees). The NACA4412 section is made from two skins With space between. The K2 section can be solid fiberglass resin.

5.10.3 Diameter: The larger, 2.0 meter diameter rotor will sweep across more wind, and therefore it Can produce more power, in a given wind speed.

TIP SPEED RATIO The ‘tip-speed-ratio’ is the speed at which the blade tip should run compared to the Wind speed. The shaft speed in revolutions per minute (rpm) depends on the tip speed And the diameter.

Rpm = wind speed x tip-speed-ratio x 60 / (diameter x ) The main reason why the two blade rotor can work at higher tip-speed-ratio is that it Only have two blades. The smaller, three bladed rotors will have a slower tip-speed, but will run more smoothly because it has three blades.

5.11 Site selection: Selecting a wind farm site is complex, time consuming, and involves multiple disciplines working on parallel paths. Financing, government permits, meteorological studies, land use restrictions, and design has to be completed or well along before a site is approved and before construction can begin. However, it is imperative in all of the above-referenced steps that construction expertise be involved and consulted to achieve maximum use of the approved site. There are three principle sources of construction expertise generally participating in

wind farm projects. They are the design team responsible for conceptual and eventual site design, the developer or construction manager of the project, and the wind turbine generator contractor.

Wind farm developers should include on their initial concept and development team people with expertise in site design and wind farm construction, regardless of whether those people ultimately end up working on the wind farm construction. After conceptual approval and financing, expertise should be added to the team regarding the selection and operation of wind turbine generators. This expertise will allow the non-construction professionals on the project team to understand the limitations of various wind turbine designs, the site specific issues that may affect the layout and operation of the wind farm, and the scheduling, civil engineering, and electrical issues that will affect actual wind farm construction. Wind is big and wind is heavy. These two factors introduce unique considerations to the construction of a wind farm that differ from the construction of other power generation facilities. Big and heavy will contribute to the determination of an appropriate site, will determine the schedule for constructing the wind farm, and will contribute additional costs to transportation, site preparation, construction, and commissioning.

When selecting the appropriate site for construction a wind farm, scheduling consideration should be given to accessing the site and to constructing the site. Integral to both of these site selection concerns is the preoperational project schedule. Development of a wind farm generally takes from 2 to 5 years with construction taking more or less than a year depending upon decisions made in the development phase. One of the key decisions that can affect the construction schedule would be the lead time in ordering the wind turbine generators selected for the project. To the layperson, all wind turbines may look the same, but that is not reflective of reality. Turbine design, turbine dimensions, turbine weights, and turbine manufacturing locations all affect the construction of a wind farm.

Another unique factor affecting project schedule and costs is the transportation and road system that exists between the wind turbine generator manufacturing point and the wind farm site. The excessive weight of a wind turbine nacelle and the excessive lengths of the wind turbine blades and tower segments require special attention to transporting the wind turbine generator to the wind farm site. Special vehicles are required to transport wind turbine components. Roads have to be selected that can adequately bear the load of wind turbine parts. The transportation route has to be selected with adequate turning radii to accommodate the wind generated power to the substation. Also, cables to monitor individual tower performance and any other tower control cables should be trenched where possible between each tower and the wind farm operational control building. Site configuration will determine where to place the operational control building, but it is normally placed near the main entrance to the wind farm.

It is important at this point to distinguish in the construction process between the wind turbine generator and the civil and electrical works. In the construction process, the supplier of the wind turbine generator is responsible for providing the tower, the blades, the hub, the nose cone, and the power unit. The supplier of the wind turbine generator is also usually responsible for the Supervisory Control and Data Acquisition (SCADA) system and can also be responsible for the provision of an initial spare part inventory and the possible design of any desired maintenance facilities.

The wind turbine supplier is also usually responsible to commission the operation of the wind turbines to demonstrate achievement of the stated performance criteria. It is important to point out that there is no standard definition of commissioning except for what is provided by contract or by technical data sheet provided by the wind turbine supplier. However, the electrical infrastructure can be tested by reliance on standard electrical tests recognized in the industry or required by applicable codes. Commissioning is necessary to commence the wind turbine warranty. Warranties generally run from two to five years and cover lost revenue, downtime to correct faults, and an evaluation of the power curve. A wind turbine power curve is a graph indicating the individual turbine’s electrical power output for operation at different wind speeds. The power curve is generally determined by local wind field measurements. Failure to achieve power curve standards is often addressed in a contract by the imposition of liquidated damages. The wind farm civil works and electrical works are usually referred to as the Balance of Plant (BOP) and are provided by a contractor different from the wind turbine supplier. BOP civil engineering scopes of work include roads and drainage, crane pads, turbine foundation, meteorological mast foundations, and buildings for electrical switch gear, SCADA equipment, and a maintenance/spare part facility. BOP electrical work scopes include point of connection equipment to feed the wind farm’s power generation into the electrical grid, underground cable networks and overhead transmission lines, electrical switch gear to protect and/or disconnect turbines or other equipment from the system, transformers and switches for individual turbines unless located within the turbine and provided by the turbine supplier, and grounding and connections for control rooms, maintenance facilities, and any other buildings onsite.

This difference in responsibility between the wind turbine supplier and the BOP contractor is the topic of some debate regarding selection of the proper project delivery system for a wind farm. Project developers generally use EPC contractors as the entity to design a wind farm project and manage construction through the commissioning phase. The EPC contractor would be responsible for contracting with the wind turbine supplier and with any BOP contractors. However, this arrangement exposes the EPC contractor to damages should the wind turbine fail from a performance or delivery perspective. Additionally, the wind turbine generator represents a high percentage of project costs without provision of an appropriate markup available to the EPC contractor. That is because the wind turbine is commonly shipped, erected, and commissioned by the wind turbine supplier and not by EPC contractor personnel. Thus, EPC contractors have begun to perceive a disproportionate risk/reward ratio in contracting with the turbine supplier, encouraging some movement to a project delivery system where the developer contracts with the wind turbine supplier directly, instead of through the EPC contractor.

Construction issues related to wind farm site selection are also affected by other issues unique to the selected parcel. Construction may be affected by land use restrictions or zoning issues, such as hunting rights, grazing rights, and cultural issues. Additionally, wildlife issues may restrict construction due to bird or bat migration, wildlife migration, spawning issues, wetlands and surface water issues. Last, noise or visual obstruction restrictions may affect placement of turbines or hours of construction operation.

Construction of wind turbine farms is greatly affected by site selection. Though these issues are relatively new in the United States, there are well developed practices within the wind turbine and wind farm industries developed in other countries and adopted within the United States to address constructability concerns. So, despite all of the publicity related to wind farm site selection regarding zoning, permitting, environmental concerns, and community

reaction, the construction industry is capable of constructing a wind farm in the face of multiple site specific issues.

6. How to increase the capacity: 'Smart Turbine Blades' To Improve Wind Power:

Fig: 2.8 Smart Turbine Blades The research by engineers at Purdue University and Sandia National Laboratories is part of an effort to develop a smarter wind turbine structure.

"The ultimate goal is to feed information from sensors into an active control system that precisely adjusts components to optimize efficiency," said Purdue doctoral student Jonathan White, who is leading the research with Douglas Adams, a professor of mechanical engineering and director of Purdue's Center for Systems Integrity.

The system also could help improve wind turbine reliability by providing critical real-time information to the control system to prevent catastrophic wind turbine damage from high winds.

"Wind energy is playing an increasing role in providing electrical power," Adams said. "The United States is now the largest harvester of wind energy in the world. The question is, what can be done to wind turbines to make them more efficient, more cost effective and more reliable?"

The engineers embedded sensors called uniaxial and triaxial accelerometers inside a wind turbine blade as the blade was being built. The blade is now being tested on a research wind turbine at the U.S. Department of Agriculture's Agriculture Research Service laboratory in Bush land, Texas. Personnel from Sandia and the USDA operate the research wind turbines at the Texas site.

Such sensors could be instrumental in future turbine blades that have "control surfaces" and simple flaps like those on an airplane's wings to change the aerodynamic characteristics of the blades for better control. Because these flaps would be changed in real time to respond to changing winds, constant sensor data would be critical.

"This is a perfect example of a partnership between a national lab and an academic institution to develop innovations by leveraging the expertise of both," said Jose R. Zayas, manager of Sandia's Wind Energy Technology Department.

Research findings show that using a trio of sensors and "estimator model" software developed by White accurately reveals how much force is being exerted on the blades.

Purdue and Sandia have applied for a provisional patent on the technique.

Findings are detailed in a paper being presented May 4 during the Wind power 2009 Conference & Exhibition in Chicago. The paper was written by White, Adams and Sandia engineer Mark A. Rumsey and Zayas. The four-day conference, organized by the American Wind Energy Association, attracts thousands of attendees and is geared toward industry.

"Industry is most interested in identifying loads, or forces, exerted on turbine blades and predicting fatigue, and this work is a step toward accomplishing that," White said.

A wind turbine's major components include rotor blades, a gearbox and generator. The wind turbine blades are made primarily of fiberglass and balsa wood and occasionally are strengthened with carbon fiber.

"The aim is to operate the generator and the turbine in the most efficient way, but this is difficult because wind speeds fluctuate," Adams said. "You want to be able to control the generator or the pitch of the blades to optimize energy capture by reducing forces on the components in the wind turbine during excessively high winds and increase the loads during low winds. In addition to improving efficiency, this should help improve reliability. The wind turbine towers can be 200 feet tall or more, so it is very expensive to service and repair damaged components."

Sensor data in a smart system might be used to better control the turbine speed by automatically adjusting the blade pitch while also commanding the generator to take corrective steps.

"We envision smart systems being a potentially huge step forward for turbines," said Sandia's Rumsey. "There is still a lot of work to be done, but we believe the payoff will be great. Our goal is to provide the electric utility industry with a reliable and efficient product. We are laying the groundwork for the wind turbine of the future."

Sensor data also will be used to design more resilient blades.

The sensors are capable of measuring acceleration occurring in various directions, which is necessary to accurately characterize the blade's bending and twisting and small vibrations near the tip that eventually cause fatigue and possible failure.

The sensors also measure two types of acceleration. One type, the dynamic acceleration, results from gusting winds, while the other, called static acceleration, results from gravity and the steady background winds. It is essential to accurately measure both forms of acceleration to estimate forces exerted on the blades. The sensor data reveal precisely how much a blade bends and twists from winds.

The research is ongoing, and the engineers are now pursuing the application of their system to advanced, next-generation turbine blades that are more curved than conventional blades.

This more complex shape makes it more challenging to apply the technique.

In 2008 the United States added 8,358 megawatts of new wind-power capacity, which equates to thousands of new turbines since the average wind turbine generates 1.5 megawatts.

The new capacity increased the total U.S. installed wind power to 25,170 megawatts, surpassing Germany's capacity as the world's largest harvester of wind power.

"Our aim is to do two things - improve reliability and prevent failure - and the most direct way to enable those two capabilities is by monitoring forces exerted on the blades by winds," Adams said.

6.1 10 MW wind turbine data: Type: wt10000dd Grid frequency: 50 Hz / 60 Hz Tilt angle rotor axis: 5째 Hub height: 125 m Hub type / material: cast iron Mainframe type: cast iron Type of tower construction: conical tubular steel tower Rotor diameter: 190 m Lightning conductor: integrated OPERATING DATA Cut-in wind speed: 4 m/s Rated wind speed: 11.5 m/s Cut-out wind speed: 30 m/s GENERATOR AND POWER ELECTRONICS: Generator type: HTS synchronous Rated driving power: 12,000 kVA Rated generator speed: 10 rpm Number of poles: multi-pole Cooling: cryogenic and water cooling Converter type: IGBT, 4-quadrant Generator rated power 0.95 inductive to 0.95 capacitive at 690V ph-ph DRIVETRAIN SPECIFICATION:

Type of gearing: direct drive Gear lubrication: Connection gear / generator: BRAKING SYSTEM: Operational brake: individual blade pitching Type of construction: gear/servomotor Mechanical brake: disc brake YAW SYSTEM: Type of yaw bearing: ball bearing Drive unit: gear motor Number of drive units: tbd Brake: active brake plus motor brake AMBIENT TEMPERATURE RANGE: Normal: During operation: -10°C to 40°C Survival range: -20°C to 5 6.2 Wind power market: Wind power is growing at over 20% annually, with a worldwide installed capacity of 238,000 MW at the end of 2011,and is widely used in Europe, Asia, and the United States Several countries have achieved relatively high levels of wind power penetration, such as 21% of stationary electricity production in Denmark,18% in Portugal, 16% in Spain,[14% in Ireland and 9% in Germany in 2010.As of 2011, 83 countries around the world are using wind power on a commercial basis.

As of 2011, the Roscoe Wind Farm (781 MW) is the world's largest wind farm. As of February 2012, the Walney Wind Farm in United is the largest offshore wind farm in the world at 367 MW, followed by Thanet Offshore Wind Project (300 MW), also in the UK. The London Array (630 MW) is the largest project under construction. The United Kingdom is the world's leading generator of offshore wind power, followed by Denmark.

There are many large wind farms under construction and these include Anholt Offshore Wind Farm (400 MW), BARD Offshore 1 (400 MW), Clyde Wind Farm (548 MW), FântâneleCogealac Wind Farm (600 MW), Greater Gabbard wind farm (500 MW), Lincs Wind Farm(270 MW), London Array (1000 MW), Lower Snake River Wind Project (343 MW), Macarthur Wind Farm (420 MW), Shepherds Flat Wind Farm (845 MW), and the Sheringham Shoal (317 MW) Chart 1

Top 10 wind power countries Country

Total capacity end 2009 (MW)

Total capacity June 2010 (MW)

Total capacity end 2010 (MW)

Total capacity June 2011 (MW)

United States

35,159

36,300

40,180

42,432

United Kingdom 4,092

4,600

5,204

5,707

Spain

19,149

19,500

20,676

21,150

Portugal

3,357

3,465

3,734

3,960

Italy

4,850

5,300

5,797

6,200

India

10,925

12,100

13,066

14,550

Germany

25,777

26,400

27,215

27,981

France

4,521

5,000

5,660

6,060

China

26,010

33,800

44,733

52,800

Canada

2,550

3,319

4,008

4,611

Rest of world

21,698

24,500

26,154

29,500

Total

159,213

175,000

196,630

215,000

6.3 Wind turbine limitation: 6.3.1 No electricity when there is any wind: The limitation of wind power is that no electricity is produced when the wind is not blowing.

Thus, it cannot be used as a dependable source of base load power. Utilities and merchant generators will not invest huge sums of money into a technology that does not work when the wind is not blowing. Americans want the lights on when they flip the switch, no questions asked. Wind power will probably increase its market share when we develop a 'smart grid' that can handle multiple distributed generation input sources of electrical power.

6.3.2 Wind turbines killing migrating birds: It has been estimated that about 45,000 birds (golden eagles, kestrels and red-tailed hawks) have been killed over the past twenty years by the whirling blades of wind turbines. The rows of spinning blades at Altamont Pass, east of San Francisco, turn wind into electricity, but they are killing many predatory birds whose annual migration route includes the pass. Past attempts to reduce bird kills have included painting the tips of turbine blades to try to make them more visible to birds and installing screens around generators. These measures have failed to substantially lower the number of bird deaths Bat kills are the latest big problem for wind farmers. Researcher's estimate that 1,500 to 4,000 bats were killed at the Mountaineer Wind Energy Center in Western Maryland in 2004.

This is raising concerns about an expansion of wind turbine use at Backbone Mountain in Maryland, where Clipper Wind power, Inc. Of California is planning to build a project 20 miles away from the mountaineer site.

6.3.3 Solutions of limitations: We should build wind turbines where there is too much of wind like near sea so there will be 24 hours electricity and the problem of electricity will be solved and there are less birds near sea so the problem of killing birds will also be solved.

7. Conclusion & overview: 7.1. Overview Country Overview Area

:

147,570 sq. km.

Population

:

about 144 million (2008)

Per Capita GDP

:

554 US$ (at current price)

Real GDP Growth: Electricity

6.21%

(2007- 08)

:

Per Capita Generation (2006- 07) :

168.08 kWh

Per Capita Consumption (2006-07): 149.97 kWh Energy Availability

:

230 kg OE (per capita) Share of commercial energy is About 50%

Available Energy Resources Gas Total recoverable reserve in 22 gas fields is 15.51 TCF. Total amount of gas consumed till 2006 is ~ 5.6 TCF. For a growth rate of 7%, the above gas reserve will be exhausted within the Year 2015.

Coal Total coal reserve is ~ 2000 million tons out of which about 500 million tons is potential reserve. The potential reserve can meet a fractional future energy demand of the country.

Hydro Presently harnessing 230 MW from the Kaptai Dam. Potential sites are Matamuhuri (300 MW) and Sangu (200 MW) and a few mini-hydro sites of potential 10 MW.

Present Electricity Sector (Dec.08) Installed Capacity

:

BPDB 3812 MW (59 Units) IPP 1330 MW (39 Units) SIPP & Rental 311 MW (7 Units) Total 5453 MW (105 Units)

Generation Capacity by Fuel Type Max. Demand Served

: 4146 MW (Apr. 2009)

Net Energy Generation :

23,267 GWh

Key Energy Issues (according to Draft NEP 2008) More stress on hydrocarbon exploration Minimizing over-reliance on Natural Gas Improving Gas and Electricity consumption practices through efficient management Massive investment requirements to meet forecast growth in energy demand Introduction of Nuclear Energy within the shortest possible time

Govt. Vision for Power Sector

7.2. Comparison of the Various Power Plants The comparison of steam power plant, hydro-electric plant, diesel power plant and wind turbine power plant is given below in the tabular form Sl. Item No.

Steam Power Station Hydro-electric power Plant

Diesel power Plant

Wind turbine Power Plant

1

Site

Such plants are located at a place where ample supply of water and coal is available, transportation facilities are adequate Initial cost is lower than those of hydroelectric and nuclear power plants.

Such plants are located where large reservoirs can be obtained by constructing a dam e.g. in hilly areas.

2

Initial cost

3

Running cost

Higher than hydroelectric and nuclear power plants.

Practically nil because no fuel is required.

4

Limit of source of power

Coal is the source of power which has limited reserves all over the world.

5

Cost of fuel transportati on

6

Cleanliness and simplicity

Maximum because huge amount of coal is transported to the plant site.

Least clean as atmosphere is polluted due to smoke.

Water is the source of power which is not dependable because of wide-Variations in the rainfall every year.

Practically nil.

7

Overall efficiency

Least efficient.

Overall efficiency is about 25%

Most efficient.

Overall efficiency is about 85%

8

Starting

Requires a lot of time for starting

Can be started instantly.

Highest among all plants because of high price of diesel.

Diesel is the source of power which is not available in huge quantities Due to limited reserves.

Higher than hydro and nuclear power plants.

More clean than steam power and nuclear power plant.

More efficient than steam power station.

Efficiency is about 35%.

Can be started quickly.

9

Space required

These plants need sufficient space

Require very large area

Require less space.

Initial cost is very high because of dam construction and excavation work.

Most simple and clean.

Such plants can be located at any place because they require less space and small quantity of water.

Initial cost is less as compared to other plants.

These plants are located at corner of see.

Initial cost is highest because of huge investment on building a Wind turbine. it has the minimum running cost.

The source of power is the wind which is available in Earth.

Minimum because its free.

Its fully cleane.

Average efficient than others.

Can be started easily.

These require average space

because of boilers and other auxiliaries.

because of the reservoir

10

Maintenanc e cost

Quite high as skilled operating staff is required.

Quite low.

Less

11

Transmissio n and distribution cost

Quite low as these are generally located near the load centers.

Quite high as these are located quite away from the load centers.

12

Standby Losses

Maximum as the boiler remains in operation even when the turbine is not working.

No standby losses .

Least as they are generally located at the center of gravity of the load.

Less standby losses

as compared to any other plant of equivalent capacity.

Average cost.

Quite high as these are located far form load centers.

Less

7.3 Conclusion: In order to research and gain knowledge about wind turbine behaviour during grid faults or Abnormal operations new wind turbine models have to be developed. Approximated Behaviours are not sufficient for today’s tasks and therefore detailed multifunctional Models have to be developed.

7.4 Future work: The research captured in this work represents the state of the art of today, though it is only a step in the effort to clarify the influences of faults in wind turbines and their impact on the Grid. The following are opportunities for future work: · An important part the wind turbine model yet to be implemented, is the total Protection system of the turbine. A model encompassing this would to enable Further fault studies. · Extending the model with recently developed control strategies for fault ride through Capability. · Further validation of the transformer and the complete turbine models with Measurements should be performed. · Implementation of other machine phenomena such as slots effects, skin effects and The implementation of a realistic converter model (switching model) to capture Harmonic contributions to the turbine (flicker) and investigate overload conditions of The converter. · Expanding the study in order to clarify the influence of several different generators Types and finding a rule for the machine phenomena. · Measurement of an asymmetrical fault to further validate the machine and wind Turbine model.

7.5 Summery of the work: Wind turbines have potential benefit in that they have power density that matches coal, at least according to one measure. Set against this the uncontrollable nature of their output.

Locking ahead to when fossil fuels become scare involves consideration of the low power densities that are likely to be associated with liquid energy sources. At present, it is hard to say whether building wind farms and running a grid will be possible without fossil fuels, especially because no viable renewable fuel in liquid form is evident. Concerning introducing wind turbines in order to reduce the present use of fossil fuel, while it is probable that wind turbine do save some fossil fuels.

Wind power is not an all0encompassing solution, able to replace all other forms of electricity generation. However, it will play a significant role in nation’s policy toward helping divert the worst effects of anthropogenic climate change and to ensuring energy security in future decades.

Chapter 8 8. References: [1] V.K. Mehta & Rohit Mehta, “Principles of Power System” 2009, S.CHAND and Company.

[2] G.R. Nagpal, “Power Plant Engineering” 2nd Edition.

[3] V.Akhmatov, H. Knudsen, A.H. Nielsen, Advanced simulation of windmills in the Electric power supply, International Journal of Electrical Power and Energy Systems, 22 (6) , p. 421-434, Elsevier 2000 [4] Vladislav Akhmatov, Analysis of Dynamic Behavior of Electric Power Systems with Large Amount of Wind Power, PhD Thesis April 2003, Ørsted DTU, Denmark [5] Sigrid M. Bolik, Jens Birk, Björn Andresen, John G. Nielsen, Vestas Handles Grid Requirements: Advanced Control Strategy for Wind Turbines, EWEC’03, Juni 2003, Madrid, Spain [6] Wolsink, M. 2007. Wind power implementation: The nature of public attitudes – Equity and fairness instead of ʻbackyard motives. Renewable Sustainable Energy Rev; 11: 1188– 1207.

[7] Langdon Crane, Magneto hydrodynamic (MHD) Power Generator: More Energy from Less Fuel, Issue Brief Number IB74057, Library of Congress Congressional Research Service, 1981, retrieved from [8] AAAS Annual Meeting 17 - 21 Feb 2011, Washington DC. Sustainable or Not? Impacts and Uncertainties of Low-Carbon Energy Technologies on Water.Evangelos Tzimas, European Commission, JRC Institute for Energy, Patten, Netherlands [9] International Energy Agency, "2008 Energy Balance for World", 2011.

[10] Layton, Edwin T. "From Rule of Thumb to Scientific Engineering: James B. Francis and the Invention of the Francis Turbine," NLA Monograph Series. Stony Brook, NY: Research Foundation of the State University of New York, 1992.

[11] GWEC, Global Wind Report Annual Market http://www.gwec.net/index.php?id=180.Retrieved 14 May 2011.

Update".

Gwec.net.

[12] Hannele Holttinen, et al. (September 2006). "Design and Operation of Power Systems with Large Amounts of Wind Power", IEA Wind Summary Paper" Global Wind Power Conference 18–21 September 2006 [13] Johnson, Scott J.; van Dam, C.P. and Berg, Dale E. (2008). "Active Load Control Techniques for Wind Turbines".

Sandia National Laboratory. http://www.sandia.gov/wind/other/084809.pdf. Retrieved 13 September 2009.

[14] Griffin, Dayton A.; Ashwill, Thomas D. (2003). "Alternative Composite Materials for Megawatt-Scale Wind Turbine Blades: Design Considerations and Recommended Testing".

Journal of Solar Energy Engineering.

[15] Thomas C. Elliott, Kao Chen, Robert Swanekamp (coauthors) (1997). Standard Handbook of Powerplant Engineering (2nd edition ed.). McGraw-Hill Professional.

[16] British Electricity International (1991). Modern Power Station Practice: incorporating modern power system practice (3rd Edition (12 volume set) ed.). Pergamon.