Notes Topic 11 - 1 INTRODUCTION 2 WIND RESOURCES 3 WIND...

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Unformatted text preview: 1 INTRODUCTION 2 WIND RESOURCES 3 WIND TURBINE COMPONENTS AND CONCEPTS 4 WIND TURBINE AERODYNAMICS 5 WIND TURBINE BLADE DESIGN AND BLADE MANUFACTURE 6 WIND TURBINE MECHANICAL DESIGN 7 GENERATORS 8 GRID CONNECTION AND POWER CONDITIONING 9 OPERATION CONTROL OF WIND TURBINES 10 CONTROL FOR SAFETY 1 Introduction.................................................................................................................................................. 1 2 Wind Resources ........................................................................................................................................... 1 3 Wind Turbine Components and Concepts ................................................................................................... 1 4 Wind Turbine Aerodynamics....................................................................................................................... 1 5 Wind Turbine Blade Design and Blade Manufacture .................................................................................. 1 6 Wind Turbine Mechanical Design ............................................................................................................... 1 7 Generators .................................................................................................................................................... 1 8 Grid Connection and Power Conditioning................................................................................................... 1 9 Operation Control of Wind Turbines ........................................................................................................... 1 10 Control for Safety......................................................................................................................................... 1 11 SITING, PLANNING APPROVAL AND INSTALLATION OF SMALL TURBINES ........................... 2 11.1 Siting ..................................................................................................................................................... 2 11.1.1 Local topography / wind obstructions ............................................................................................ 2 11.1.2 Distance to occupied buildings....................................................................................................... 3 11.1.3 Distance to grid or battery room..................................................................................................... 3 11.2 Planning Approval – Hamilton Hill Case Study ................................................................................... 4 11.2.1 Background..................................................................................................................................... 4 11.2.2 Obtaining planning approval to install the 20kW turbine .............................................................. 5 11.3 Installation – Exmouth Case Study ....................................................................................................... 6 11.3.1 Typical tower designs and foundation layout................................................................................. 6 11.3.2 Foundations and anchors ................................................................................................................ 7 11.3.3 Civil works for electrical cable..................................................................................................... 10 11.3.4 Tower & Gin-pole assembly......................................................................................................... 11 11.3.5 Guy wires...................................................................................................................................... 13 11.3.6 Connecting the Turbine to the Tower ........................................................................................... 14 11.3.7 Tower Erecting ............................................................................................................................. 16 11.4 Final Adjustments and Commissioning .............................................................................................. 17 Figure 11-1 The effect of obstructions on turbulence ........................................................................................ 3 Figure 11-2 Erecting method of a guyed tower with a gin pole and tow up vehicle.......................................... 6 Figure 11-3 A typical foundation plan for a wind turbine................................................................................. 7 Figure 11-4 Two foundations that have been shuttered (note the string line that is used for ensuring the foundations are in line) ................................................................................................................................ 8 Figure 11-5 Pouring of concrete foundations into a shuttered hole.................................................................... 9 Figure 11-6 Guy wire anchors cast into the concrete block ............................................................................... 9 Figure 11-7 Trenching for the underground cable............................................................................................ 10 11-1 Figure 11-8 (left) Lowering an inverter onto the pad (note the conduits protruding the pad) and (right) Electrical equipment after installation (dump load in the foreground, three inverters and green metering box) ............................................................................................................................................................ 11 Figure 11-9 Bolting the tower sections together............................................................................................... 11 Figure 11-10 (top) The tower and gin pole fully assembled and attached to the hinge assembly, and (bottom) close up of the hinge assembly before standing the gin pole..................................................................... 12 Figure 11-11 Lifting the gin pole to the vertical position................................................................................. 13 Figure 11-12 Trial raise of the tower to check guy lengths.............................................................................. 14 Figure 11-13 Installing the nacelle onto the top tower flange .......................................................................... 15 Figure 11-14 Fastening the blades onto the hub............................................................................................... 15 Figure 11-15 Attaching the tail boom............................................................................................................... 16 Figure 11-16 Attaching the gin pole tie bar between the gin pole and the foundation block (note the sheave system) ....................................................................................................................................................... 17 Figure 11-17 The Exmouth Mini wind farm after commissioning (3 x 20kW Westwind turbines). ............... 18 11 INSTALLING SMALL WIND TURBINES 11.1 Siting Deciding on the actual position to install a small turbine is based on a series of compromises between factors such as those outlined below. Generally the influence of these factors is learned by experience, although general rules-of-thumb may be used to identify an optimal location. A poorly sited turbine may be fated to have significantly increased installation costs, increased maintenance and or mediocre power production. Therefore extra care and time spent in the planning stage could pay significant rewards to the long-term success of the project. 11.1.1 Local topography and wind obstructions This is possibly the most important factor to consider when micro-siting a small wind turbine. The obvious factors to consider are the effect of obstructions (hills, valleys, buildings, trees etc) on the prevailing wind. Not only may these obstacles reduce wind strengths but also the resulting increase in turbulence may be devastating to the reliable operation of the turbine. If possible it best to select a location that has minimal disturbances to the wind particularly in the prevailing wind direction. The zone of turbulence caused by the disturbed wind flowing over an obstruction up to twenty times the height of the obstruction downwind and, interestingly, may extend about two times the height upwind. The disturbed airflow may also be experienced up to twice the obstructions height downwind. See Figure 11-1. If it becomes impractical to install the turbine abiding these rules of thumb then a taller tower may solve some of these concerns. Installing a turbine near a ridge or steep slope should be avoided at all costs because of the severe level of turbulence that almost certainly will occur. The effect of turbulence may significantly reduce the lifetime of a turbine as well as reduce the potential energy capture. Gradual, smooth, slopes may accelerate the wind, particularly if siting the turbine on a gentle rise, which may pay dividends as increased energy capture. The design of tower may also dictate what sort of terrain is preferred. Generally, it is easier to install all types of guyed towers on level ground; more is presented on this later in the topic. Depending on the capacity of the turbine and the style of tower, vehicular access may be required, especially by heavy trucks or cranes. In these circumstances it may be preferred to locate the turbine near existing tracks to reduce costs and to 11-2 minimise environmental damage by vehicles travelling over un-spoilt ground. Tilt type tower designs often require a path for the tow-up vehicle to travel as the tower is being raised which must also be taken into account. Figure 11-1 The effect of obstructions on turbulence resistance per unit length and also the cost of the cable therefore minimising cable length will not only reduce the cost of the cable but also the cost of civil works. The conductor size of the transmission cable can be sized based on voltage drop over the length of the cable. 5% is generally considered the maximum limit for cable losses. It should be noted however that, since these losses are proportional to the current squared, at normal generated levels (about 20% rated power) the transmission losses are significantly lower. 11.2 Planning Approval Hamilton Hill Case Study 11.2.1 Background Since 1998 Westwind turbines have been involved in a project with the Australian CRC for Renewable Energy (ACRE) aimed at improving the performance of small wind turbines. Much of the research of the project has focused on the development of a prototype 20kW machine. One 20kW wind turbine prototype was installed at the Murdoch University Energy Research Institute (MUERI) in 1999 for the purposes of design testing. Three more 20kW prototypes were installed at Western Power’s Advanced Mini Wind Farm in Exmouth in June 2002 as part of a demonstration of the technology (see above). To date, the focus in designing the turbines has been on reliability in remote areas. (Source: Gipe, P. Wind Energy Basics p72) 11.1.2 Distance to occupied buildings All turbines produce noise, particularly aerodynamic noise from the rotor in high winds. If this is likely to be a source of censure it is advisable to install the turbine well away from any occupied buildings or areas where people may frequent. A general rule of thumb is100m metres away from a dwelling and (if possible) locate the turbine downwind of the predominant wind direction. Certain designs of turbines are noisier than others, but generally the lower the tip speed ratio the lower the noise generated. The wind turbine manufacturer should be able to supply noise data for the turbine, which can be used to predict the level of noise at a certain distance from the tower. It is not advisable to install a turbine, of any size, on the roof of an occupied building for a number of reasons. Since a wind turbine is a rotating machine, some sort of vibration will be transmitted through the tower at all operating speeds. This may lead to frustrating humming noises caused by the vibrations reaching natural frequencies of certain parts of the buildings structure. As previously mentioned wind flowing over any obstacle has the potential to create turbulence, and this is definitely true for air flow over buildings due to the may sharp angles that the wind may encounter. Further research is required to develop a design that maintains reliability while optimising the energy production of the 20kW prototype. The path to optimal design requires a wind turbine test site with a good wind resource that is accessible in order to implement changes and monitor performance. For economic feasibility, most wind turbine sites have a mean hub-height wind speed of at least 6.5m/s. The MUERI test site is easily accessible but has a mean wind speed of 3.3m/s, which limits the conclusions of the study in terms of the performance of the machine. The Exmouth site has a good wind resource but is not frequently accessible due to its remote location. Thus a search for a new wind site was undertaken which would have a mean hub-height wind speed of at least 6.5 m/s and would be located in the Perth Metropolitan Area, so as to be easily accessible. A number of potential sites were considered and the most promising was the old Western Power (formerly SECWA) wind turbine test site, the other side of Cockburn Rd. from the old Fremantle Power Station. In the early-1980’s, the site contained three grid-connected wind turbines of various sizes – 20kW, 30kW and 60kW. During 1989-1990 Murdoch University undertook a wind assessment survey of the site using wind sensors on a 50m mast. The results of the survey were published in the West Australian Wind Atlas [1] and extrapolation of the data using WasP (Wind Atlas Analysis and Application Program) predicted that the annual mean speed of the site at 30 m height was 6.9m/s. Lastly, it is not advisable to locate the turbine near areas frequented by people for safety reasons. Even though turbines may be guaranteed for a number of years and have a predicted lifetime of up to thirty years, failures due occur. Even a small component being shed from a rotating turbine has the potential to inflict serious injury, albeit the probability is very low. Today, the site is part of a strip of undulating coastal limestone dunes in the Beeliar National Park in the suburb of Hamilton Hill. The turbines have now been removed (the 20kW M.A.N. machine can now been seen at Western Power’s World of Energy museum in Fremantle) but the concrete foundations, cabling conduits and pole transformer (for grid connection) can still be seen at various places around the site. The 50m mast is now being used as a radio mast and the site now boasts a Telstra mobile phone tower. 11.1.3 Distance to grid or battery room Ideally the wind turbine should be located as close as possible to the battery room or to a power line, if it is grid connected, to minimise cabling costs. Underground cables are most commonly used with small turbines rather that overhead wires, which are generally more expensive over the relatively short lengths, required. The cabling costs include the cost of the cable, trenching costs (including digging, clean fill beneath and above cable, safety labelling and backfilling). The size of the conductors within the cable determines the The location, good wind resource and presence of existing wind turbine infrastructure (foundations and cabling) helped to sway the decision towards the Hamilton Hill site as a new test site. 11-3 11-4 11.2.2 Obtaining planning approval to install the 20kW turbine This case study shows that the process of obtaining planning permission for installation of even a small stand-alone wind turbine can be lengthy and involved. The first stage of obtaining planning approval was to ascertain the owner of the land. Since the site was located within the boundaries of the Beeliar National Park, the Regional Parks Department of CALM (Conservation and Land Management) was contacted. CALM provided a topographical map of the region that showed that area containing the site was owned by the Western Australian Planning Commission (WAPC) but leased by the City of Cockburn. The next step was to approach the Development Branch of the Cockburn City Council to enquire whether the Council would accept a sub-lease of the land. The response from the Council appeared favourable and the Council provided Town Planning Schemes in order to pinpoint the exact location of the site in terms of Lot Number, Location Numbers, Plan/Diagram Numbers and Volume/Folio Numbers. A visit to the Central Map Agency of the Department of Land Administration (DOLA) was undertaken to obtain a Locality Map of the region with detailed contour information. The Locality Maps use Australian Map Grid References and are composed of digitally captured data from ground surveys and aerial photography. An Application to Commence Development was then sent to the Cockburn City Council. The Development Application consisted of the following: • • • • A completed Application Form 1 to be signed by the owner of the land (in this case the Secretary of the WAPC) A report containing details of the proposed development with diagrams of tower and foundation measurements and tow-up lengths The DOLA Locality Map showing the location of the proposed turbine in relation to it’s surroundings and location of nearby installations (in this case the radio mast and the mobile phone tower) The appropriate Planning Service Fee (in this case 0.23% of the estimated cost of development). 11.3 Installation Exmouth Case Study This section outlines the practicalities of installing a stand-alone wind turbine in a remote location. The photographic examples given within this section are of the installation of a 20kW Westwind turbine in Exmouth, Western Australia. 11.3.1 Typical tower designs and foundation layout Most small-scale turbines are erected on relatively slender, tubular or lattice masts that are supported in the vertical position by guy wires. This style of structure yields a more optimal design in terms of minimising tower and foundation material; hence lower comparative cost than with the cantilever design preferred by utility scale turbines. Cantilevered designs require a crane for erecting the tower that may present a significant cost penalty in remote locations due to the cost of mobilising the crane to and from the site. So called ‘tilt’towers’ are often preferred by many manufacturers of small wind turbines. This design allows the standing of the tower via levering action of a gin-pole with the use of a tow-up vehicle. It is this common style of tower, as shown in Figure 11-2, which will be referred to during this section. Section 6.3.3 gives further information on various tower designs. Figure 11-2 Erecting method of a guyed tower with a gin pole and tow up vehicle Gin Tow rope The application was forwarded by the City of Cockburn Council to the WAPC for further assessment. The WAPC referred to the following government bodies for their comments and recommendations: • • • Heritage Council of W.A. Main Roads Department of W.A. Bush Forever Tower (Source: Courtesy of Westwind Turbines) Bush Forever (a Conservation Group located within the Ministry of Planning) contacted ACRE directly to clarify the location of the proposed wind turbine. The assessment period by the WAPC lasted around 3 months and approval of the use of the site was given subject to a number of conditions: • • • • The turbine and associated equipment was to be removed at the end of the tenure The turbine and associated equipment was to be removed should the Main Roads Department require the use of the land No clearing, disturbance and/or degradation of existing vegetation was to be carried out during the installation and management of the turbine No new access ways/tracks were to be permitted at the site. 11-5 After selecting the proposed site to install the turbine, the next step is to determine the exact location of the various foundations both for the tower and the guy anchor blocks. During this stage it is important to closely follow the manufacturers plans regarding the layout of the foundations and any recommendations they may have which will simplify the installation procedure. Figure 11-3 shows a typical foundation drawing for a tiltup tower. Most towers will require four separate foundations for the guy wires and a central tower foundation as shown in Figure 11-3. In tower designs such as this, the tower is hinged at its base at an axis perpendicular to the gin pole. It is therefore important to decide on the most favourable orientation of the foundations so that the tower may be easily lowered for turbine maintenance (i.e no obstructions in the lay down path including rotor area) and an adequate tow-up path exists if a vehicle is used for erecting the tower. If it is impractical to use a vehicle for raising the tower quite often a suitable sized and rated winch may be used. If a winch is to be used a separate foundation may need to be cast for anchoring the winch. 11-6 Most manufacturers recommend that foundations that lie on the tower hinge axis (the two foundations that are at right angles to the gin pole) be at the same elevation as the tower foundation. This greatly reduces complications associated with the geometry of changing guy lengths as the tower is raised. This may be achieved by using a dumpy level or else a string-line and a spirit level may be used to determine the elevations across a particular site. It is wise to peg out the proposed location of the foundations, the tower and guys in its lay down position and the tow-up path (if required) to check for conflicts with any obstructions and remedy these if necessary. Once a satisfactory layout has been achieved, the exact locations of the foundation blocks should be pegged. Each corner of all blocks should be marked with pegs or marking paint on the ground. It is essential to double check all measurements taking particular attention to ensuring that all foundations are correctly spaced and square with one another. Figure 11-3 A typical foundation plan for a wind turbine a suitable location. From the tower designer’s point of view, a wide guy spread is preferred as this results in lower guy tensions and tower axial loads thus reducing the required strength of the tower. For this reason it is important to closely follow the tower installation plan and only modify guy spread after consultation with the manufacturer. The purpose of the guy foundations is to provide a restraining force to oppose the guy tension caused by thrust on the rotor and wind load on the tower. The tower foundation spreads the axial force, acting down the tower, to the ground to prevent settling of the structure. The foundations must be able to withstand the loads caused by the maximum design wind speed acting on the structure. Foundation design is heavily dependant on the type of soil that is present at the intended installation site. Soils that have high clay content tend to have greater shear strength and can withstand greater bearing loads than loose sandy soils. Hence foundations installed in clay type soils may be smaller than those used for the same structure in sandy soils. The moisture content of the soil may also change the mechanical properties. An example of this is a tall anemometer tower that was installed in the centre of Australia where the soil is generally loose ‘pindan’ type sand. Screw anchors were used to anchor the guy wires, which proved to be adequate for a number of years. During a particularly bad storm with both heavy rain and strong wind, one of the screw anchors pulled out of the ground, drawing the core of earth with it. This occurred because the shear strength of the earth reduced to the extent that it could no longer withstand the tension load of the guys. 11.3.2.1 Concrete Foundations The most common foundation used with all wind turbines are made by casting concrete into suitably sized holes dug into the ground. Details of the grade of concrete, reinforcements and the dimensions of the block to be cast are provided by the tower manufacturer and must be closely adhered to. The concrete should be poured into the hole where it will bear against undisturbed ground, (i.e. no backfilling to reduce an oversized excavation) this provides the greatest possible key, hence high resistance to moving. A bobcat or backhoe is normally used to excavate the earth (which has been pre-marked by the paint marks or pegs) for the foundation blocks. Since it is unlikely that the site will be perfectly level in elevation it is common that wooden shutters (a low box open at the top and bottom) will have to be constructed so that the concrete level may be raised above that of the surrounding ground. See Figure 11-4. The designer often stipulates the maximum height of shuttering which is permissible. Figure 11-4 Two foundations that have been shuttered (note the string line that is used for ensuring the foundations are in line) (Source: Courtesy of Westwind Turbines) 11.3.2 Foundations and anchors As previously mentioned, most small wind turbines are normally erected on guyed towers. There are normally four sets of guys; i.e. the guy wires are attached to the tower at ninety degrees to each other and are anchored at some radial distance from the base of the tower. The distance between two opposing guys is termed the guy spread, which is determined by the particular tower design. For a given tower height a narrow guy spread results in both higher guy tension and tower axial loads than a design with a relatively wide guy spread. For ease of siting, a narrow guy spread is preferred as a smaller tower footprint makes it easier to find 11-7 11-8 (Source: B. Brix, Westwind Turbines) Concrete foundations need to be left to cure before being loaded by the operating turbine or even by raising the tower. Curing time depends on many factors such as temperature, humidity and soil moisture content, but it is good practise to leave the foundations to cure for a week before proceeding with the installation. Some manufacturers provide foundation components that must be cast into the concrete, such as the tower tilt hinge, guy wire anchoring hoops and/or ‘rag’ bolts that will later be used for fixings. While others prefer the option of first casting the concrete blocks and then drilling and bolting the necessary hardware to the blocks once they are cured. If components are to be cast into the concrete, it is essential that their locations are double checked before the concrete starts curing and becomes un-workable. See Figure 11-5 and Figure 11-6. Figure 11-5 Pouring of concrete foundations into a shuttered hole (Source: B. Brix, Westwind Turbines) 11.3.2.2 Ground Anchors Some small turbines use ground anchors to restrain the guy wires. This reduces the cost of installation as no excavation or concrete is required. Ground anchors are available in various designs, but the operating principle is similar in that they rely on the passive soil resistance and mass of ‘entrapped’ earth to resist uplift. One type of anchor commonly used resembles an auger, which is screwed into the ground. The diameter and embedded depth of the auger determines the level of restraint that may be offered. The soil type and importantly the moisture content also play a large role in the restraining load offered. The anchors are usually driven into the ground at the same angle as the guy wire so all load is taken as pure axial force, since this type of anchors has limited bending or rolling capacity. A bobcat or a tractor with a special high torque hydraulic motor is used for screwing the foundations into the ground. 11.3.3 Civil works for electrical cable The cable path for the transmission cable to the grid or battery room should also be marked out as per the site plan. Electrical standards stipulate the depth (normally 600mm) and other requirements such as safety signage that will be required. If the earth is rocky it may be necessary to line the excavated trench with a layer of clean sand before and after laying the cable to prevent damage to the cable from the rocky backfill. Figure 11.7 shows the laying of a 100metre turbine cable for the Exmouth wind farm. Figure 11-7 Trenching for the underground cable (Source: B. Brix, Westwind Turbines) Figure 11-6 Guy wire anchors cast into the concrete block (Source: B.Brix, Westwind Turbines) In some circumstances, particularly with grid connect systems, a concrete pad may have to be cast to secure electrical equipment such as inverters, switchboards, load dumps etc. These pads usually require electrical conduits to be cast into the concrete so that the underground site cable may be neatly connected within the electrical enclosure (see Figure 11-8). 11-9 11-10 Figure 11-8 (left) Lowering an inverter onto the pad (note the conduits protruding the pad) and (right) Electrical equipment after installation (dump load in the foreground, three inverters and green metering box) Figure 11-10 (top) The tower and gin pole fully assembled and attached to the hinge assembly, and (bottom) close up of the hinge assembly before standing the gin pole (Source: B. Brix, Westwind Turbines) 11.3.4 Tower and Gin pole assembly On a tilt-up style tower the tower sections are first laid out along the ground in the correct sequence from the tower base to the tower top. Firstly the tower base is fitted onto the central hinge assembly and then each section is bolted on in succession (see Figure 11-9 and Figure 11-10). Most tubular style tower have flanged joints using bolted connections. It is important to use lock-nuts on all tower bolts to prevent any fasteners from loosening due to vibrations as the turbine is running. All bolts should be torqued to the manufacturers specifications. Figure 11-9 Bolting the tower sections together (Source: B. Brix, Westwind Turbines) The gin pole is also hinged at or near the tower hinge. A sheave (pulley) system connecting the guy wire end of the gin pole to the foundation block is used to increase the mechanical advantage of the towing vehicle. Once the sheave system is installed and the guy wires have been attached the gin pole may be lifted to the vertical position. A Hiab or small crane may be needed to lift the gin pole on larger towers (see Figure (Source: B. Brix, Westwind Turbines) 11-11 11-12 11-11). Correct personal safety equipment, such as hard-hats, must be worn whenever any lifting is performed. under any component of the tower as it is being raised. Figure 11-12 shows a trial lift - note the two operators closely adjusting the guy tension of the side guy wires during this initial raising. Figure 11-11 Lifting the gin pole to the vertical position Figure 11-12 Trial raise of the tower to check guy lengths (Source: B. Brix, Westwind Turbines) A draw wire may be used to draw the tower power cable through the tower and any other cables that may be needed such as a furling wire. It is usually practical to install this draw wire section by section as the tower is being bolted together. This is especially the case if a tall tower is being constructed. (Source: B. Brix, Westwind Turbines) 11.3.5 Guy wires Most wind turbine towers use high tensile galvanised stay wires. This type of wire is appreciably stronger than ordinary steel cable of the same mass per metre. This type of cable also offers increased corrosion resistance due to the construction of fewer but thick strands of wire compared to standard wire rope that is constructed of many fine strands that tend to absorb and trap moisture. In most installations at least one end of each guy wire will have to be formed on site. This process usually involves forming an ‘eye’ in the end of the stay wire using a thimble (eyelet) and wire rope grips. It is unusual that the manufacturer will supply the guy wires with both ends formed ex-factory. This is due to any errors that may occur during foundation layout or to differing elevation of foundation blocks. With guy wires larger in diameter than approximately 10mm, special tools may be needed to form the end of the cable around the thimble. Rigging screws or turnbuckles are usually fitted on the ground level end of all guy wires to allow for fine adjustment in length, or for reducing guy tension prior to lowering of the tower. 11.3.6 Connecting the Turbine to the Tower Some manufacturers supply a small trestle structure that may be placed under the lowered tower to safely support the tower and turbine, at an easily serviceable height. This also makes assembly of the nacelle onto the tower easier. If a trestle is supplied it should be placed under the tower when the tower is being lowered after the trial lift. The first stage of installing the turbine onto the tower usually involves bolting the nacelle onto the tower top as seen in Figure 11-13. Larger turbines usually have a bolted flange connection that connects the nacelle yaw spindle to the tower top flange. Smaller turbines may have a larger diameter sleeve that slides over the tower tip and grub screws that lock the turbine in place. The tower transmission cable can then be connected to the turbines output leads. A junction box is often provided to house this connection. Connection of the tower cable to the site (underground) cable should also be done at this point before the rotor is fitted. After the gin pole has been raised to the vertical position and all guy wires installed, it is advisable to make a trial lift of the tower – without the turbine fitted. Before raising the tower, a final check of all the bolts and connections should be made; particular attention should be paid to the guy wire and tow-up cable connections. A trial lift will ensure that all guy cables are the correct length and everything has been done correctly before the installation of the turbine. The trial lift should be performed at a steady and slow pace ensuring the operator of the lifting winch or tow-up vehicle is in close communication with an observer near the tower. If a guy wire becomes excessively tight (due to incorrect length) or something looks incorrect the lift should be immediately stopped and the problems rectified. Under no circumstances should anyone stand Attaching the tail boom and fin and then the blades is the next step (see Figure 11-14 and Figure 11-15). The method of doing so differs for each manufacturer, so close consultation with the installation manual should be followed, particularly to the torques needed for the blade attaching bolts. Some manufacturers provide a nose cone to cover the hub of the turbine; this is primarily for aesthetic purposes but also may shield the blade pitch mechanism from water and dirt ingress. 11-13 11-14 Figure 11-13 Installing the nacelle onto the top tower flange Figure 11-15 Attaching the tail boom (Source: B. Brix, Westwind Turbines) (Source: B. Brix, Westwind Turbines) Figure 11-14 Fastening the blades onto the hub 11.3.7 Tower Erecting After all of the bolted and electrical connections have been re-checked the tower is ready for final raising. If possible it is advisable to short circuit the generator (if it is of the permanent magnet type) prior to raising the tower. This is usually possible at the terminal box at the tower base where the tower transmission cable connects to the site cable. Shorting the generator creates an electrical brake within the generator preventing the rotor from turning. By doing so the likelihood of the blades rotating and hitting the slack guy wires will be minimised. For safety reasons the tower should only be raised in relatively low wind strengths. After the tower has been raised, the gin pole may then be fastened to its respective foundation block usually with a short length of chain. After doing so the tension in the tow-up cable can be removed and the tow-up vehicle can be detached (see Figure 11-16). The guy wires should then be tightened to the manufacturers specifications by rotating the rigging screws. The tower should be checked for vertical in two planes at right angles. This may be done by using a spirit level or more accurately by holding a plumb bob on a string at a distance from the tower and eying the edge of the tower to the vertical string. Guyed towers are susceptible to being deformed by unevenly tensioned guy wires, thus it is important to also check the tower for straightness while the tower is being adjusted in the vertical plane. (Source: B. Brix, Westwind Turbines) 11-15 11-16 Figure 11-17 The Exmouth Mini wind farm after commissioning (3 x 20kW Westwind turbines). Figure 11-16 Attaching the gin pole tie bar between the gin pole and the foundation block (note the sheave system) (Source: B. Brix, Westwind Turbines) (Source: B. Brix, Westwind Turbines) 11.4 Final Adjustments and Commissioning After the guy wires have been correctly tensioned and the tower adjusted for vertical the riggings screws should be locked to prevent them from unscrewing during service. This is a possibility due to normal vibrations of the guy wires or more seriously by stock, which often enjoy a back scratch on the guy wires. Some rigging screws have locking nuts provided; in any case it is good practise to pass a loose loop of wire through adjacent rigging screws to prevent them from loosening. Any shackles that have been used should also be wired to prevent them from being loosened. The turbine may now be put into service. The electrical short that was previously installed to prevent the rotor from turning may be removed and the turbine un-furled. If there is sufficient wind the rotor will begin to turn. There should be no undue noises or vibrations as the rotor turns. If there is a significant vibration or noise the turbine should be shorted and the problem investigated. If the generator is turning a voltmeter may be used to read the voltages between each phase, (for a three phase output machine), with the generator disconnected from any load. These voltages should be all identical for a given rotational speed. This may be a difficult measurement to obtain in gusty conditions when the rotor speed is varying with time since the open circuit voltage of a permanent magnet generator is proportional to its rotational speed. If the turbine is in circuit, the currents in each of the three phases should be measured to see if there is a phase balance. References: [1] Gipe P. Wind Energy Basics- A guide to small and micro wind systems. Chelsea Green Publishing Co. 1999. Useful websites: www.westwind.com.au http://www.westernpower.com.au/html/about_us/environment/renewable_energy/renewable_wind.html#exm outhwindfarm www.awea.org/pubs/documents/swslides/toc.htm It is good practise to inspect the turbine paying particular attention to guy tension after the turbine has been in service for a couple of days and after the first strong wind. 11-17 11-18 ...
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This note was uploaded on 06/09/2011 for the course PV 5053 taught by Professor Aasd during the Three '11 term at University of New South Wales.

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