Author: Kevin Landers, BEng MIEI, electrical works project manager, Enercon GmBH GSK in Curabinny, Co. Cork has recently installed a 3MW wind turbine in order to reduce its electricity bill and carbon emissions. It is part of an overall collaborative project with other pharmaceutical and healthcare companies in the area known as the Cork Lower Harbour Energy Group (CLHEG). As part of this scheme, the nearby facilities of DePuy Synthes and Janssen have also installed a 3MW turbine. The turbine in GSK will supply 30% of the factory’s electricity needs. It is expected that the turbine will reduce the carbon emissions of GSK Cork by 4000MT of CO2 per annum. Funding for the project was approved in 2013 and is part of GSK’s sustainability target to reduce carbon footprint by 25% by 2020. As part of the planning process, GSK engaged with several regulatory bodies including the National Parks and Wildlife Services and the Irish Aviation Authority. A detailed avian impact study was carried out, which included radar tracking of bird movements in the nearby Special Protection Area and across the turbine sites. A community gain fund was set up by CLHEG, which has benefited local community and sports organisations. After a detailed tendering process, it was decided that an Enercon E-101 3MW turbine would be the most suitable from an efficiency and capacity perspective. Enercon GmBH is a German company that has Irish bases in Tralee and Dublin. The current workforce in Ireland consists of 174 people in areas such as service, repair, technical support, installation, project management, sales, site assessment and grid integration. Since 1998, Enercon has installed 760MW capacity in Ireland and aims to reach 900MW in 2015. After a detailed planning phase, construction works in GSK began with the excavation for the foundation in October 2013. The foundation itself was poured in December 2013. It measures 3.5m deep and has a diameter of 21.5m. It was poured in one day over a 14-hour period, which involved 115 truckloads of concrete. The turbine components started to arrive in January 2014. They were delivered into the nearby Ringaskiddy port. The concrete tower components were the first to arrive. These consisted of 17 sections of over 50MT each. After the concrete tower segments were installed, post tensioned and grouted, the three steel sections were installed to bring the tower to its 99m height. The installation of the nacelle, generator and hub followed before the blades were installed in April 2014. A temporary road was constructed through a field owned by IDA Ireland to facilitate the transport of the 50m blades to from the port to the site. As soon as the turbine was mechanically complete, the commissioning process commenced. The turbine produced electricity for the first time on 30 April of this year.

Turbine technology

[caption id="attachment_16404" align="aligncenter" width="640"]gsk2 Transporting the turbine (image: Skytec Ireland)[/caption] The E-101’s rated power is 3MW. The cut-in wind speed is 2.5m/s and it will produce maximum power at 12m/s. When operating at full power, the hub will rotate at 14rpm. This helps towards a much reduced noise output, as smaller turbines can rotate at up to three times this value. A storm-control feature starts to reduce the power output of the turbine at wind speeds of 25m/s and will shut down the turbine at wind speeds of 34m/s or higher. The turbine is designed to keep the environmental impact on the local area to a minimum. A shadow shut-off system programmes the turbine to shut down at certain times when the light intensity of the sun is sufficient to cause shadow flicker at nearby dwellings. An extensive study was prepared by GSK, which detailed the times where shadow flicker was possible. This study took into account variables such as the position of the sun, light intensity and wind direction. The Enercon generator is a synchronous machine with an electromagnetic rotor. At turbine start- up, an excitation controller imports current from the grid to excite the rotor. At the same time, the turbine control system sends a signal to the pitch motor control to pitch in to the wind. Once a sufficient rpm is achieved, the generator produces AC electricity at 13-14 Hz. The lack of a gearbox and use of direct-drive technology ensures a reduced noise output from the generator. A rectifier system in the nacelle converts the AC-generated power to DC. Cables are routed down the tower to transport the DC power to inverter cabinets at ground level. There are 11 inverter cabinets, each capable of processing 300kW. The inverter cabinets convert the DC electricity back to AC at 50Hz, thus making it compatible for use on the Irish grid. A transformer in a customised station outside the tower steps the voltage up to 20kV. From here, the transformer is connected to GSK’s MV room to enable the supply of the factory load via a PIR (Pre Insertion Resister). The PIR limits the voltage dip attributable to inrush when the wind turbine transformer is energised.

Power control, service and maintenance

[caption id="attachment_16407" align="aligncenter" width="1399"]gsk3 Construction of the turbine (image: Skytec Ireland)[/caption] The turbine has a reactive power range of -1700kVAr to +1700kVAr and can import or export maximum reactive power even when it is operating at as little as 10% of the rated active power. This will help GSK to improve its power factor at the point of connection with the ESB. Enercon has installed a remote transmission unit (RTU), which allows GSK to send set points for the desired active and reactive power from the turbine via Modbus protocol. Active power control is crucial for GSK as the turbine is not permitted to export to the grid under the terms of its connection agreement with the ESB. In times of low load in the plant, GSK can get the turbine output to ramp down so that the turbine does not export to the grid. The signals are implemented by measuring the import from the grid and implementing an algorithm via an ION meter that will send instantaneous set points to the turbine via the RTU. A stop command can also be issued by GSK to the RTU. This will cause the turbines blades to pitch fully out of the wind and therefore cease production. This can be used by GSK to stop the turbine before it tests its diesel generator sets, for example. The turbine service and maintenance is covered by an ‘EPK’ agreement (Enercon PartnerKonzept) between GSK and Enercon. Under this agreement, Enercon will perform routine maintenance and fault repair for at least 12 years with the option of an extension to 20 years, the design life of the machine. Enercon organises all required maintenance works to ensure a high availability. If the turbine goes down with a fault, the SCADA system will send an automatic message to the Enercon Service Dispatch Centre in Tralee. A service team is then dispatched to address the fault in a timely manner. Overall, some 28,596 man hours involving over 500 (the vast majority of whom were Irish) construction workers were completed during the implementation of the project. In what can be classed as an outstanding achievement, there were zero first-aid incidents or accidents over the entirety. GSK can look forward to a future where both its spend on energy and carbon footprint are greatly reduced. Enercon GmBH is a German company that was founded in 1984 by electrical engineer Aloys Wobben. The company has installed 20,000 wind turbines worldwide and has more than 11,000 employees. Its Irish bases in Tralee, Co Kerry (service HQ, project management) and Dublin (sales, project management, site assessment, grid integration) employ 174 people in areas such as service, repair, technical support, installation, project management, sales, site assessment and grid integration. Since 1998, Enercon has installed 760MW capacity in Ireland and aims to reach 900MW in 2015.