beginning about one year ahead of the start of construction. Actual construction on site began in August 2015, with concrete for the first foundation being poured in early November and the first turbine completed in January 2016. At points during construction, three main cranes were employed plus a set of auxiliary cranes doing pre-erection. With erection being carried out on four different fronts (three main cranes and one set of auxiliary cranes) and BOP in parallel, it called for a coordination team of about 40 people. At the peak of construction, close to 500 people were working on site. Riedweg commented: “With three main cranes erecting turbines plus the BOP, it was fairly intense.” In spite of the numerous challenges, turbine erection went pretty much to plan. According to Riedweg, it took just eight months to erect the entire wind farm, with as many as 12 turbines being erected per month at the peak of activities. Like at Amakhala, a “starlift” technique was used, wherein all three blades are assembled at the base of the tower and the whole “star” lifted to the top of the tower and connected to the nacelle. This has become Nordex’s standard method of installation. “We only do single blade installation when the wind is too high, or it is not possible to erect the rotor on the ground, or on higher towers,” commented Riedweg. Special Project Supplement N117/2400 offered the best load factor of the competition at the time. “When we launched the machine in around 2013/14, we were probably 6-12 months ahead of the competition. With the high load factor we were able to offer the best cost of energy. There was also good feedback on the machine’s reliability.” The N117/2400 has been specially developed for low-wind sites. With a rotor diameter of 117 m and a swept area of 10 715 m2, the N117/2400 is one of the most efficient IEC 3 turbines in its class. According to Nordex, in typical low-wind regions, it will achieve over 3500 full-load hours. At Pampa, the turbine’s high load factor will see the wind farm yield an expected 640 GWh of electricity per year. The N117/2400 is the result of over a decade of ongoing technical enhancements to the multi-megawatt platform. The rotor consists of three rotor blades made of high-quality glass fibre-reinforced polyester, a hub, slewing rings and drives for adjusting the rotor blades. A pitch system is used to control and optimise output. The variable-speed rotor enhances the aerodynamic effects and reduces the wind load on the system. If necessary, each rotor blade can be locked in any position by means of an innovative locking system to facilitate servicing. The three redundant and independently controlled rotor blades can be set at full right angles to the rotation direction for aerodynamic braking. In addition, the hydraulic disc brake provides additional support in the event of an emergency stop. The wind turbine has two anemometers. One anemometer is used for controlling the turbine, the second for monitoring the first. All operational data can be monitored and checked on a control screen located in the switch cabinet or via an external laptop. The data and signals are transmitted via ISDN for remote monitoring and the operator can download all key data for the turbine from the internet. The necessary communications software and hardware is supplied by Nordex. The drive train consists of the rotor shaft, the gearbox, an elastic coupling and the generator. Nordex equips the turbines with a two-stage planetary gearbox with a spur gear stage or with a differential gearbox. The gearbox is fitted with a cooling circuit with variable cooling output. The gearbox bearing and tooth engagement are kept continuously lubricated with oil. The generator is a double-fed asynchronous machine. Nordex has been using this type of generator with variable-speed turbines successfully for many years. The main advantage is that only 25-30 per cent of the energy produced needs to be fed into the electricity grid via a frequency converter. The deployment of this generator/ frequency converter system thus cuts the total cost of the wind power system. The gearbox, generator and converter of the turbine each have independent active cooling systems. The cooling system for the generator and frequency converter is based on a cooling water circuit, while the gearbox is cooled by an oil-based system. This ensures optimum operating conditions in all types of weather. A separate cooling system room at the rear of the nacelle facilitates access to the cooling units and ensures optimum performance of the individual systems. The nacelle consists of the cast machine frame, a welded generator frame, a steel structure for the crane system and for supporting the nacelle housing and the nacelle housing itself, which is made of glass fibre- reinforced plastic. Ergonomically designed, it is spacious and thus service friendly. The nacelle features two redundant wind direction sensors to continuously monitor wind direction. If the permissible deviation is exceeded, the nacelle yaw is actively adjusted by means of up to four geared motors. When installing the machines, care has to be taken to ensure the blades and yaw are used in the most optimised way for energy production. Convinced of the turbine’s technical capability, UTE first began discussing the project with Nordex around the end of 2013 and the deal was closed by the end of 2014. Riedweg recalls: “At that time we were executing the Juan Pablo Terra project with them and we received the Notice to Proceed on Pampa in March 2015.” Pampa is a huge site, covering some 70 km2. In the first instance, this called for the construction of 42 km of roads in and around the wind farm to supplement the existing public roads. As the EPC contractor, with responsibility for all the coordination and handling the environmental issues, Nordex had its work cut out. “It was not easy dealing with the environmental issues, said Riedweg. “We also had to source and procure some equipment, including some key equipment like transformers, from local manufacturers. This meant we had to support them with engineering, certification and the quality process. There was a lot of work to do in terms of getting some constructors up to speed. At one point we also had to step in to do additional coordination after one of our sub-contractors faced bankruptcy in the middle of construction. Everything that could go wrong went wrong. There was flooding in April, which closed the site for more than two weeks. There were a lot of challenges.” And with the general public being a significant shareholder, everything was under the spotlight. Riedweg added: “We attracted a lot of attention. Some we wanted but some we would have liked to avoid.” The challenges were compounded by the tight timeline – around 20 months to erect 59 turbines, build the substation and complete the balanceof plant (BOP). This was around 6-7 months shorter than the Amakhala wind farm in South Africa, which with 56 turbines was Nordex’s previously biggest project. “The consequences of having a very tough timeline, was that we had to do BOP and erection in parallel. So there was a lot of coordination to do,” said Riedweg. “We were finishing a platform, bringing a crane, constructing a turbine, running the cables underground and connecting everything the next day.” It all required careful planning, THE ENERGY INDUSTRY TIMES - FEBRUARY 2017 The turbine blades were shipped to the port of Montevideo before being transported to the site Turbine blades being transported to site by road: 42 km of roads had to be constructed in and around the wind farm Nordex’s scope also included construction of the substation
Energy Industry Times February 2017
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