Planning and levelized cost of energy analysis of a floating offshore wind farm and a fixed bottom offshore wind farm project

Today wind energy is one of the significant resources of the world's energy. Although offshore wind industry has the added attactions due to increased rated power and large turbines, there are several additional cost and risk factors that offshore industry faces including additional technical requirements of turbines, complex foundation structures, complex electrical infrastructure and additional challanges during transportation, installation and maintenance works. Bottom – fixed offshore wind farm solutions that have been established the most in the industry are not economically competitive especially due to the low achievement rates of utilization of installation vessels in the chartered period, which result in financial damages and remarkable amount of costs and due to the harsh weather conditions at offshore that limit the available workable durations. As the industry tends to move into deeper waters, far away from the shore, bottom – fixed concepts become less feasible solution. Floating offshore wind turbines have more potential to overcome the challanges of offshore wind industry. The advantages of Glosten PelaStar tension leg platform concept that is analyzed in this thesis to evaluate its competitivesness vs. bottom – fixed solution, have been demonstrated in terms of enabling better weather conditions and working environment, early project completion, reduced site manning costs and elimination of the risk of financial losses due to time target failures of installation vessel charters.These advantages indicate lower levelized cost of energy results, which are very significant on the pathway to commercialization of floating offshore wind turbines. As currently there isn't a floating wind farm installed in the scale that have been modelled in this thesis, the detailed planning results of a conceptual floating offshore wind farm consisting of 83 PelaStar tension leg platform turbines provide comparable basis in order to evaluate the competitiveness of this concept vs. dominant bottom – fixed solutions in the offshore industry. In addition to advantages, the additional costs that is estimated due to unique hull structure production and support barge design have also been considered when calculating life cycle costs and levelized cost of energy of both solutions. Levelized cost of energy depends on life cycle cost of a wind farm including capital, operational and maintenance costs and as well as on annual energy production of the wind fam. The phases of life cycle costs of a wind farm consist of conception & definition, design & development, manufacturing, installation, exploitation and dismantling costs. Annual energy production depends on turbine rated power, capacity factor and annual mean wind speed of the wind farm.An annnual energy production calculation for a 7 MW turbine has also been demonstrated in this thesis based on the annual wind speed data at hub height of an operating offshore wind farm at North Sea. In this study LCOE calculations have been conducted by evaluating three different methods that are commonly used in the offshore industry. By keeping all the cost parameters and annual energy production amount same, LCOE is calculated as 124.9 Euro/MWh, 141.8 Euro/MWh and 148.36 Euro/MWh respectively using simple LCOE method, cash flow LCOE method and leveraged cash flow LCOE method. Leveraged cash flow LCOE method is chosen to further evaluate PelaStar tension leg platform and bottom-fixed projects. Assuming the wind farm is located at 75 meter water depth, 156.46 Euro/MWh LCOE is calculated for PelaStar concept. Conducting the same calculation for a location at 57 meter water depth, 156.71 Euro/MWh value is obtained while for bottom fixed project at 40 meter water depth, LCOE is calculated as 164 Euro/MWh. In order to evaluate the impact of delay in projects' timeline on LCOE values, further calculations have been conducted assuming both projects will be delayed 90 days. The increase in LCOE for PelaStar concept at 57 meter is calculated as 0.55 Euro/MWh while for bottom fixed concept the increase in LCOE has seen to be much higher as 1.28 Euro/MWh. Finally in order to evaluate the impact of wind speed on LCOE results, calculations have been repeated for PelaStar project assuming that annual mean wind speed is 10.5 m/s and 11.4 m/s. The increase in wind speed, resulting in increase of annual energy production, reduced the LCOE results to 143.02 MWh and 135.23 MWh respectively.