Balancing availability, reliability and future regulatory impact against overall project capex for offshore wind farms

RWE Innogy is developing a 750 MW offshore wind farm, Gwynt y Mor (GyM), 20 km off the north Wales coast and adjacent to the existing near-shore wind farms of North Hoyle and Rhyl Flats. This paper highlights some of the challenges faced in developing a large offshore wind farm in a climate of evolving renewable technology, challenging market conditions and a new GB regulatory framework for offshore transmission systems. The paper also focuses on some of the key decisions taken in the electrical system design, balancing capital expenditure with power system availability in the light of the energy value. Project appraisal from a life cycle cost perspective shows that, given the forecast value of renewable energy, it can be economically justifiable to design offshore substations above the minimum security standards being developed for offshore transmission systems in GB i.e. building in additional redundancy to improve electrical system availability. Finally, the paper discusses the use of the Wind Turbine Generator's reactive range for the provision of reactive power/voltage control, i.e. as an alternative to fully rated onshore dynamic compensation, e.g. SVC/STATCOM.