Wind turbine renewable energy project by

Wind Turbine Renewable Energy Project By: Anas Qaddoura Abdelrahman Alqatawneh Hashem Abdullah Mustafa Almomani Mustafa Al-Arini Yazan Abdullah Energy Conversion Course Project Presented to Dr.Issa Etier Department of Electrical Engineering Hashemite University Zarq-Jordan Hashemite University December 2013 Dedication To our parents, our families, and all our friends To each one who support us To all our fellows in the Electrical Engineering Department To all our fellows in the Faculty of Engineering ACKNOWLEDGMENT We can not find the words to describe the dept we owe to our project advisor: Dr.Issa Etier for his kindness, guidance, support, encouragement, and sharing us his knowledge and experience to complete this work Table of Contents Dedecation…………………………………… …….……………………………………………………………………………………………… Acknowledgment…… …………………….….………………………………………………………………………………………………… Table of Content……………………………… ……………………………………………………………………………………………………4 Chapter One: Introduction 1.1 What Cause Wind Chapter Two: Types of Wind Turbines, economical and environmental effects 2.1 Types of Wind Turbines 2.1.1 Horizontal Axis Wind Turbine 2.1.2 Vertical Axis Wind Turbine 10 2.2 The Structure of a Modern Wind Turbine 12 2.3 Environmental Effects 13 2.4 Economic Effects 14 Chapter Three: Wind Energy Potential 15 3.1 Wind Energy Potential 16 3.1.1 World 16 3.1.2 China 17 3.1.3 India 17 3.1.4 United States 18 3.1.5 Europe 19 3.1 Wind Energy in Jordan 19 3.2.1 Introduction 19 3.2.2 Outlook 20 3.2.3 Key Driver 21 3.2.4 Major Projects 22 Chapter four: Connecting the System 23 4.1 How to Choose off Grid or on Grid System 23 4.1.1 on Grid Applications 23 4.1.2 off Grid Applications 24 4.2 Comparison 24 4.2.1 Typical Configuration 24 4.3 Advantages and Disadvantages 25 4.3.1 on Grid System 25 4.2.1 off Grid System 26 Chapter Five: Wind Turbine improvement 27 5.1 Project 29 5.1.1 Introduction ………29 5.1.2 Theory 29 5.1.3 Objective 30 5.2 Secondary Advantages of Ducts 31 5.2.1 Ducts in General 31 5.2.2 Ducts Improvement 32 Chapter Six: Conclusion and Recommendation 33 References 34 Chapter One Introduction Modern Wind Energy and its Origins The re-emergence of the wind as significant source of the world’s energy must rank as one the significant development of the late 20th century The advent of the steam engine followed by the appearance of other technologies for converting fossil fuels to useful energy would seem to have forever relegated to insignificance the role of the wind energy generation In fact by the mid-1950s that appeared to be what had already happened By the late 1960s, however, the first signs reversal could be discerned, and by the early 1990s it was becoming that a fundamental reversal was underway That decade saw a strong resurgence in the worldwide wind energy industry, with installed capacity increasing over five-fold The 1990s were also mark by a shift to large, megawatt-sized wind turbines, a reduction and consolidation in wind turbine manufacture, and the actual development of offshore wind power During the start if 21th century this trend has continued, with European countries (and manufactures) leading the increase via government policies focused on developing domestic sustainable energy supplies and reducing pollutant emissions To understand what was happening, it is necessary to consider five main factors First of all there was a need An emerging awareness of the finiteness of the earth’s fossil fuel reserves as well as of the adverse of effects of burning those fuels for energy had caused many people to look for alternative Second, there was a potential Wind exists everywhere on the earth, and in some places with considerable energy density Wind had been widely used in the past, for mechanical power as well as transportation Certainly, it was conceivable to use it again Third, there was the technological capacity In particular, there had been developments in other fields, which, applied to wind turbines, could revolutionize the way they could be used These first three factors were necessary to foster the re-emergence of wind energy, but not sufficient There need to be more two factors, first of all a vision of a new way to use the wind, and second the political will to make it happen The vision began well before 1960s with such individuals It was continued by others, but soon spread to others too numerous to mention At the beginning of wind’s re-emergence, the cost of energy from wind turbines was far higher than the from fossil fuels Government support was required to carry out research, development, and testing; to provide regulatory reform to allow wind turbines to interconnect to the electrical networks; and to offer incentives to help hasten the deployment of the new technology The necessary political will for this support appeared at different times and to varying degrees, in a number of countries: first in the United States, Denmark and Germany, and now in much of the rest of the world 1.1 What Cause Wind As long as there is sunlight, there will be wind The wind is a by-product of solar energy Approximately 2% of the sun’s energy reaching the earth is converted into wind energy The surface of the earth heats and cools unevenly, creating atmospheric pressure zones that make air flow from high- to low-pressure areas Trade winds on a tropical island are fairly dependable, providing a nearly constant wind flow throughout the day and night Unfortunately, we have no trade winds in our part of the world, and weather systems move through every few days With alternating stormy and fair weather, wind speeds can range from gale force to total calm within a 24-hour period An Iowa wind turbine owner must cope with these large variations Daily and seasonal changes are important considerations for applications where electricity use is time-dependent Seasonal winds in Iowa are strongest in winter and early spring and weakest in summer Daily winds generally are strongest during the afternoon and lightest during the early morning To make the most efficient use of the energy supplied by the wind turbine (assuming little is to be fed into the utility grid), users should adjust their energy consumption to match the availability of the wind Weather forecasts are valuable in planning for high and low wind periods Wind direction is also variable, although the strongest winds generally prevail out of the southwest to northwest Knowledge of the prevailing wind direction is important for siting the wind turbine in the least obstructed setting possible Chapter Two Overview Types of Wind turbine, economical and environmental effects Many people believe that the Windmill and Wind Turbine are the same thing However, they are actually very unique and deferent in many ways The windmill was made to help pump water and grind grain very similar to the water wheel In contrast to the wind turbine which was made to produce energy for a clean and safe environment Both the windmill and the wind turbine have their own features, which can help uncover their distinctions The windmill is a much shorter machine then that of a Wind Turbine The Wind Mill uses more blades to catch more wind power thus causing more physical work to produce The blades are generally connected to an axle and then lead to the gears of a pump or that of a grinding wheel to help generate irrigation for crop production Although, the Wind Turbine and the Wind Mill may be similar they have their differences when considering certain factors And in general, if the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill And if the mechanical energy is then converted to electricity, the machine is called a wind generator 2.1 Types of Wind Turbines There are four main types of wind turbines depending on many factors such as fellow Horizontal Axis Wind Turbine (HAWT) – Upwind Some wind turbines are designed to operate in an upwind mode (with the blades upwind of the tower) Large wind turbines use a motor-driven mechanism that turns the machine in response to a wind direction Smaller wind turbines use a tail vane to keep the blades facing into the wind Horizontal Axis Wind Turbine (HAWT) – Downwind Other wind turbines operate in a downwind mode so that the wind passes the tower before striking the blades Without a tail vane, the machine rotor naturally tracks the wind in a downwind mode Additionally, in high winds the blades can be allowed to bend which reduces their swept area and thus their wind resistance Since turbulence leads to fatigue failures, and reliability is so important, most HAWTs are upwind machines So up-wind is the most common Vertical Axis Wind Turbine (VAWT) - Drag based The generator shaft is positioned vertically with the blades pointing up The turbines are usually mounted on the ground or a short tower This type is also called the Savonius turbine, after it’s inventor, S I Savonius It was invented in the 1920’s It uses drag, like a cup anemometer, to produce torque Vertical Axis Wind Turbine (VAWT) - Lift based The generator shaft is positioned vertically with the blades pointing up The blades use the lift design This type is called Darrius or “egg beater” The previous for types come from two main types of wind turbines depending on the Axis of the wind turbine either it is vertical or horizontal 2.1.1 Horizontal Axis Wind Turbine The horizontal axis wind turbines a "yaw" mechanism to turn the turbine against the wind direction in order to harvest the wind energy They are usually installed high up above ground level on a tower in order to harvest the ample wind energy up in the sky They are types of blades that are used these turbines They are Drag type and Lifting type The Drag type blades are typically what you see on an old Dutch wind mill The blades are generally flat which are hit by the wind to cause the rotation This type of design is great for operation at very low wind speed and can develop a lot of torque to perform operation However, they cannot operate at medium to high wind speed The Lift type blades are used in most modern wind turbines and on airplanes The design uses the aerodynamic properties of the blade profile to provide lift force to turn the blades such that the wind turbines can harvest the wind energy at high wind speed With this design, the rich energy in high wind speed area can then be harvested efficiently 2.1.2 Vertical Axis Wind Turbine The Vertical Axis Wind Turbines not require a “yaw” mechanism to harvest the wind energy Since the blades rotate 360 degree on the vertical shaft of the wind turbines, wind of any direction can turn the turbine The turbines are usually installed on or close to the ground level However, the wind speed is always lower than that in the upper sky There are also types of blades that are used on these turbines They are the Drag type and Lift type The Drag type blades are used on the Savonius wind turbine The blades are generally of flat type with large area They are hit by the wind to cause the rotation This type of design is good for operation at low to medium wind speed to generate electricity However, the capacity of this type of wind turbines is limited to small scale because it is difficult to make the large area of blades required The Lift type of blades is used on the Darrius or “egg beater” wind turbine The design uses the aerodynamic properties of the blade profile to provide lift force to turn the blades such that the wind turbines can harvest the wind energy at high wind speed The blade shapes are different than the lift type used on the Horizontal Axis Wind Turbines In general, each type has certain advantages and disadvantages However, compared with the horizontal axis type very few vertical axis machines are available commercially 10 satisfied by imports Jordan’s native energy resources are its modest gas reserves, oil shale deposits and tar sands It also has a small hydropower and biogas potential The Jordanian Government launched a gradual removal of subsidies for gasoline, diesel, fuel oil and kerosene in 2005 This was driven in part by a strategy to liberalize Jordan’s energy markets as well the need to alleviate the financial burden to its economy caused by rising oil prices In 2010 the Jordanian Minister of Energy and Mineral Resources Khalid Tuqan stated that the cost of Jordan’s imports of energy in that year was estimated at US$3.6 billion or 13.5 per cent of GDP In that same year figures released by the Ministry showed that imports accounted for 96 per cent of all energy used in Jordan 3.2.2 Outlook I Ma , Jo da ’s Mi ist of E e g a d Mi e al Resou es (the Ministry of Energy) called for investors to submit expressions of interest (EOIs) for installing 1,800 MWs of renewable energy plants Interested parties had until June 30 2011 to deliver proposals for renewable energy projects In the Master Strategy of the Energy Sector in Jordan for the period (2007-2020) (the Energy Strategy), the Jordanian government set a target to obtain 1,800 MWs, or 10 pe e t of the ou t ’s e e g suppl , f o e e a le sou es Of this, about 1,200 MWs will come from wind energy, 600 megawatts from solar power, and between 30 and 50 MWs from waste-to-energy facilities, according to the Energy Strategy In the request for EOIs, the Jordanian government sets out general guidelines or instructions to investors.1 The go e e t’s ke fo us is to de elop a i itial -100 MW concentrating solar power plant that uses existing concessional funding and such additional concessional funding as can be secured by the relevant project developer The approved project will be developed through a competitive tender, and depending on the availability of further concessional funding, the government may tender additional projects Further matters to note include the following:  20 Priority will be given to photovoltaic projects from to 10 MWs and solar thermal projects from 25 to 50 MWs i o de to eet the i te est of a la ge u e of investors and to comply with the commercial applications of such projects and the si ila e pe ie e e ui ed the La   La ge p oje ts ill e o side ed ut the ill eed to de o st ate thei lear supe io it i te s of te h i al a d fi a ial aspe ts i o de to e a epted i addition to compliance with the Law.2 Projects which generate energy for domestic consumption will be awarded priority over export projects Projects based on exports will be considered on a case-by-case basis and priority would be given to export projects based on regional / international initiatives Project developers that are successful in passing the EOI stage will receive a Memorandum of Understanding (MOU) from the government This will enable the project developer to proceed with measurement campaigns, feasibility studies and other preparatory and due diligence work such as negotiating access to land and financing for the proposed project Upon completion of the MOU process, the applicant will be required to submit a full and committed direct proposal to the Ministry of Energy The selection of projects will be based on evaluation criteria to be developed by a committee established by the Ministry of Energy In assessing a project, regard will be had to its financial and technical affordability as well as the need to obtain the best possible price, as required by Jordanian law The MOU will guarantee that a power purchase agreement is entered into upon the submission of a successful proposal and the completion of the renewable power project within a pre-specified timeline 3.2.3 Key Driver The E e g “t ateg s to edu e Jo da ’s depe de e o i po ted p odu ts f o pe cent (in 2010) with renewables meeting 10 per cent of energy demand by 2020 and nuclear energy meeting 60 per cent of energy needs by 2035 Since the Iraq invasion of 2003, Jo da ’s sou e of i po ted oil has ee “audi A a ia, follo ed Ku ait a d the United Arab Emirates By seeking to increase the share of renewable energy projects contributing to primary e e g suppl i Jo da , the go e e t hopes to de ease the Ki gdo ’s depe di g o international fuel prices, to enhance security of supply and to shift patterns of energy supply and de a d i to a o e sustai a le di e tio Annual electricity demand growth for the period of 2008 to 2020 is projected to be reach 5.5 per cent Experts have warned that the Kingdom faces severe water shortages in the coming years Desalination projects i te ded to eet Jo da ’s ate suppl eeds ill i ease e e g demand The Jordanian government has signed contracts with a number of companies to undertake feasibility studies to produce oil from oil shale deposits Projections indicate that oil shale 21 a o t i ute pe e t of Jo da ’s e e g produce crude oil e ui e e ts a d also e used to Jordan has potential to utilize biogas from solid waste A successful pilot biogas plant has ee uilt at the ou t ’s la gest la dfill lo ated i Russaifah The original project rated capacity as MW Due to the successful operation this was expanded to 3.5 MWs Jordan benefits from rich wind energy resources Studies show that there is a potential for several hundreds of megawatts of wind power installations around the Kingdom Jordan lies in the earth-sun belt area and has vast solar energy potential At present, solar energy is used primarily for domestic solar water heating “tudies Jo da ’s Natu al Resou es Autho it e fou d ediu a d low geothermal waters along the Dead Sea rift valley Small geothermal resources are also utilised in aquaculture 3.2.4 Major Projects 30-40 MWs Al- Kamshah wind project / Jarash- in March 2009 the Jordanian government selected a team comprising the Greek firms Terna Energy and Vector Aeolian Parks and the local firm Enara Energy Investments as the preferred bidder to build a wind farm at Al-Kamshah in Jordan The wind farm will be constructed on a build own and operate basis, under a twenty year concession, with debt finance to be provided by the International Finance Corporation Fuijeij wind project / Ma’an - the contract for the 90 MW project was due to be awarded earlier this year To date there are 16 pre-qualified applicants for this project The Jordanian government have intimated that after the initial 90MW phase is built, the project is likely to be expanded to 250MW Wadi Araba wind project - development and operation of a wind farm of 25 to 30 megawatts The Jordanian authorities have stated that the project: “would readily fit into the existing electricity supply chain as an Independent Power Producer or Public Private Partnership.” The Jordanian government has plans for three wind turbines to be stationed at AlHarir, Wadi Araa and Ma’an, which will have a combined generating capacity of 400 MW 22 Chapter Four Connecting the System Stand Alone Power System Off-grid power systems supply electricity to properties that are not connected to the public electricity network These systems are often referred to as "stand-alone power systems" (SAPS), or "remote area power systems" (RAPS) These systems are independent power stations capable of powering a wide range of applications with dependable and reliable electricity that is no different to that supplied by the national electricity grid Whether it be for a small or large new or existing home, a station, business or an entire community that depends on large diesel generators, offgrid stand-alone power systems are commonly the reliable, clean, hassle free, cost competitive answer 4.1 How to Choose off Grid or On Grid System If your facility happens to be on or near an existing electricity grid, you will have to decide whether or not you want your small wind turbine to be connected to the grid Below is a comparison of on-and off-grid applications - this will give you an idea of the typical applications for each system After this, you can look at the practicality of option, as well as the pros and cons 4.1.1 On-Grid Applications The wind turbine and the load it serves (e.g a house) are connected to a large, external electricity distribution or transmission grid This can be a national grid or one that supplies an isolated community, mining complex, or other large load, and the house or other load typically receives its electricity from the wind turbine when wind is available and from the grid when supplemental/backup power is needed Small wind turbines above 30 kW commonly use induction generators that produce gridcompatible AC electricity and can be connected to the grid directly, without inverters (although other power conditioning equipment such as step-up transformers may be required) Such turbines usually need to be connected to the grid in order to operate, since the generator relies on the grid for field excitation and frequency synchronization, though, to connect a renewable energy system to the grid, you must adhere to interconnection guidelines and a net metering agreement 23 4.1.2 Off-Grid Applications The wind turbine and the load it serves (e.g a house) are not connected to a larger electrical network, and Since wind is usually an intermittent energy resource, off-grid systems are typically installed with some form of energy storage device (usually a bank of lead-acid batteries) that stores excess wind-generated electricity and supplies it to the load (e.g house) when there is insufficient wind Battery systems can supply reserve power when energy demand exceeds that delivered by the wind turbine, such as during calm spells DC electricity from turbines can be used directly for battery charging but is not suitable for loads that require alternating current (AC), such as common household appliances In these cases, an inverter is required to convert the DC power to AC Inverters are becoming more common in off-grid power installations and can provide AC electricity of the same quality as grid power 4.2 Comparison Below a comparison between on and off-grid small wind systems configurations and applications so you can determine which more suitable for the certain needs: 4.2.1 Typical Configuration Typical on-grid small wind turbine configuration with permanent magnet alternatorand synchronous inverter: Figure 4.1 Typical On-Grid system wind turbine 24 Typical off-grid small wind turbine configuration with battery storage but without supplemental or backup energy systems: Figure 4.2 Typical off-grid small wind turbine 4.3 Advantages and Disadvantages 4.3.1 On Grid System 4.3.1.1 Advantages Allows renewable energy generators to use the "grid as storage" for excess generation, thereby reducing the need for expensive battery storage systems and improving the payback period for the investment Eliminates the need for an expensive second meter, thereby reducing the installation costs Reduce or eliminate environmental impact from the disposal of lead-acid batteries, the burning of fossil fuels for backup generators and potential spills of generator fuel 4.3.1.2 Disadvantages Grid connection is not permitted everywhere in your country Process to obtain approval for interconnection from the utility company can be lengthy and complicated, and requires careful planning For DC output turbines, connection to the grid requires an inverter capable of producing “grid-ready” AC electricity While such inverters are commonly available for photovoltaic systems, most of these models can only be used with wind turbines if they are tied to a 25 battery bank that acts as an energy buffer A number of leading manufacturers of small wind turbines are in the process of developing ‘battery-less inverters’ that avoid the extra cost of battery banks Note, for battery-less inverters, the requirement by many utilities for inverter compliance with the UL 1741 standard (in USA for example) limits the amount of time some small wind systems can spend storing energy in the grid Be informed of recent inverter developments (consult an expert, if necessary) before deciding to go with a battery-less inverter for on-grid application 4.3.2 off-Grid System 4.3.2.1 Advantages Systems are easy to set up and No access to the utility grid Off-grid systems can be cheaper than extending power lines in certain remote areas Consider off-gird if you’re more than 100 yards from the grid The costs of overhead transmission lines range from $174,000 per mile (for rural construction) to $11,000,000 per mile (for urban construction) Become energy self-sufficient, Living off the grid and being self-sufficient feels good For some people, this feeling is worth more than saving money Energy self-sufficiency is also a form of security Power failures on the utility grid not affect off-grid systems 4.3.2.2 Disadvantages High Cost of batteries Maintenance of batteries Back-up system costs Higher level of skill, knowledge, and discipline required for managing electrical load according to what your generation system(s) can provide 26 Chapter Five Wind Turbines improvement Wind Turbines Classification Turbines are often mounted on a tower to raise them above any nearby obstacles One rule of thumb is that turbines should be at least 30 ft (9.1 m) higher than anything within 500 ft (150 m) Small Scale Wind Turbines The generators for small wind turbines usually are three-phase alternating current generators, even though, Some models utilize single-phase generators The trend is to use the induction type They are options for direct current output for battery charging and power inverters to convert the power back to AC but at constant frequency for grid connectivity In real life, efficiency of this type ranges from 10-30% Wind Power Production Limitations Braking of the wind from its upstream speed to its downstream speed, while allowing continuation of flow regime When the rotor rotates too slowly, it allows too much wind to pass undistributed, so power is lost The turbulence in the air stream caused by blades rotation Viscous and pressure drag on the rotor blades, The swirl imparted to the air flow by rotor, blade tip vortices 27 Power losses in transmission and electrical system How to Improve Efficiency? In general, there are two methods to increase the efficiency of wind turbines: Reducing electrical/mechanical losses: this could be done by increasing the efficiency of the inner components of the turbine, such as the generator, the gear box, etc… Increasing the captured power by the turbine The Captured Power By Wind Turbines Mechanical power : Cp: power coefficient : Air density A: Turbine Swept area V: wind speed This equation states the power available in wind Since the relationship is cubic, The power extracted from the wind greatly depends on the wind velocity In this project, our main concern will be increasing wind velocity rather than the other limitations Acceleration of Airflow Velocity According to Bernoullis’s principle of compressible gases: By placing the wind turbine inside a convergent duct, the cross sectional area of the wind flow will decrease which leads to an increase in wind speed Figure 5.1 : acceleration of airflow velocity 28 Effects of Boosting the Wind Velocity Boosting the wind velocity that passes through the turbine will greatly increase the generated power In Jordan, Cut-Out limits are rarely reached by wind Figure 5.2 Effect of boosting the wind velocity 5.1 Project: 5.1.1 Introduction: Conventional wind turbines were not very efficient, expensive, and have a limited fatigue life This project investigates ducted turbines for the use of wind power generation The aim of this project is to increase the efficiency of the wind turbine with a new duct design 5.1.2 Theory The ducted turbine has the ability to accelerate the airflow through a converging intake thereby increasing the power extracted from airflow 29 This is supposed to reduce the blade tip vortices as well, which all can increase the efficiency so the output power 5.1.3 Objective In our project we are looking for designing a new duct with improved properties These properties include:     Higher efficiency Lower price Reduced complexity More feasible Developing of a new duct design that meets these properties in a decent way 5.1.4 Power Extracted by an Ideal Wind Turbine Without a duct: Let: r = 1.5 m v = m/s At sea level: P= - Then: P = 541.1 watt With a duct: Outer Radius = 2m V2= 8.888 m/s - Then: P = 3039 watt That’s about times greater than the inducted turbine 30 5.2 Secondary Advantages of Ducts Ducted turbine offers a solution for some of wind power generation limitations: Adjusting the angle of attack, this results in more efficient generation Reduction of span-wise flow area At low wind speeds there will be no more losses caused by lowered rotating speeds 5.2.1 Ducts in General The ducted turbine is an environment friendly, safe alternative method of power production from renewable sources The ducted turbine reduces: The blade flash Kills the noise made by the turbine Landscape pollution (better look) Which overcomes some of the biggest problems facing the wind energy industry Notes on Ducts The micro and small wind turbines are more efficient systems for a ducted wind turbines Considering the feasibility and reliability of installing them Designing of a new duct with improved properties is possible Ducts Efficiency The dimensions of the duct (such as the duct surface area and the depth of the duct) are important for the optimization of the efficiency stats The shape of the duct is very important to control the velocity and pressure too, that will optimize the efficiency 31 5.2.2 Duct Improvement 5.2.3.1 Dimensions The following relation describes the air velocity before and after going through the duct: It’s clear that v2 is directly proportional to A1, A2, V1 but A2 and V1 cannot be modified (Independent from the duct) We can modify A1 by: Depth of the duct The angle that the duct makes with the horizontal at the intersection with blades point 5.2.3.2 Shape The shape of the duct matters, the less resistant to air flow the better This will reduce the mechanical stress on the duct holdings The aerodynamics of the duct depends completely on the shape of it 5.2.3.3 Material The material of the duct is important; it must be as smooth as possible Duct installation To install the duct, a suitable structure is needed to hold it A lot of mechanical stress is applied to the duct by air, also its weight plays a rule The duct holders must be strong enough to attain such forces 32 Chapter Six Conclusion and Recommendation Wind energy technology will supplement other technologies for producing energy but cannot by itself produce enough energy output to replace conventional coal, wood and nuclear power stations For Jordan, having limited fossil fuel resources and exposed to the vagaries of the price of imported fuel, the need for energy from renewable sources is critical Jordan, unlike some of its oil rich MENA neighbors, has taken clear steps towards encouraging the development of renewables by commencing the implementation of a regime devoted to the regulation of the renewables sector However, more work needs to be done, not least by providing more clarity on the tariffs for electricity produced from renewable sources, i.e by allowing for the payment of a green tariff to producers of renewable energy 33 References http://www.backwoodshome.com/articles2/yago140.html Wind Power https://en.wikipedia.org/wiki/Wind_power Wind Power Potential http://www.nrel.gov/docs/fy12osti/51946.pdf Windmill and wind turbine http://www.polarisamerica.com/wind-basics/windmill-vs-windturbine/ Wind Power http://environment.nationalgeographic.com/environment/global-warming/windpower-profile/ Stand Alone Power System http://goo.gl/XnhCdu History (Wind Energy Explained ) Book 34 ... response to a wind direction Smaller wind turbines use a tail vane to keep the blades facing into the wind Horizontal Axis Wind Turbine (HAWT) – Downwind Other wind turbines operate in a downwind mode... as fellow Horizontal Axis Wind Turbine (HAWT) – Upwind Some wind turbines are designed to operate in an upwind mode (with the blades upwind of the tower) Large wind turbines use a motor-driven... that the wind turbines can harvest the wind energy at high wind speed With this design, the rich energy in high wind speed area can then be harvested efficiently 2.1.2 Vertical Axis Wind Turbine