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In this paper, a site-specific optimization procedure aimed at finding the optimal substructures of a 10 MW Floating Offshore Wind Turbine (FOWT) is presented. An in-house developed Frequency Domain (FD) model is adopted for the simulation of the coupled system. Two Mediterranean sites have been chosen for the characterization of the metocean environments. 20-year databases have been used to obtain the joint distributions of wind speed, significant wave height and peak spectral period. The optimizations, performed adopting a Genetic Algorithm (GA), are aimed at reducing the costs of the floating substructure, controlling the maximum system response under both extreme and fatigue wind-wave loads. Results show that the optimized solution significantly reduces the system cost with an acceptable increase of the loads, opening interesting perspectives for the reduction of the Levelized Cost of Energy (LCOE) in sites characterized by mild sea states and low wind resource. • A site-specific optimization procedure for a 10 MW semisubmersible wind turbine is proposed. • Simulations are performed using a 7-DoF coupled frequency-domain model. • Optimizations are performed considering two installation sites in the Mediterranean Sea. • Objective functions are: maximum tower load, manufacturing cost and fatigue damage. • Results show the existence of improved solutions compared to an upscaled configuration. [ABSTRACT FROM AUTHOR]

The well factory mode can effectively reduce the drilling, platform and fracturing cost in shale gas development. The scale effect is an important factor affecting the flowback fluid treatment cost, and the number of wells covered on the platform directly affects the flowback fluid treatment scale. Based on this knowledge, multi-objective optimization of water resources management is carried out to study the optimal balance between economic cost and environmental impact under given conditions. The result of numerical example analysis shows that increasing the number of wells per platform can significantly reduce 25.02% of water resources management cost and 27.2% of sewage discharge. Based on it, the optimization model of platform position under well factory mode is established. The proposed model studies the relationship among water resources management cost, drilling cost and platform position. At the same time, according to the genetic algorithm, this paper develops a strategy to solve the optimization model. The case study indicates that the optimization model can reduce the platform amount in a given area and increase the number of wells per platform. The study demonstrates that the proposed model can give full play to the technical advantages of the well factory, which significantly reduces the cost of shale gas development by 12.67% and 27.2% of sewage discharge. [ABSTRACT FROM AUTHOR]

In this paper, an optimization procedure is proposed to find platform and mooring system configurations which most effectively reduce the dynamic response of a semisubmersible 10 MW Floating Offshore Wind Turbine (FOWT). This is done by developing an efficient frequency domain simulation model able to account for the viscous drag forces and the contributions to the equation of motion stemming from turbine and mooring lines. The objective function is the value of the Response Amplitude Operator (RAO) at the eigenfrequency of the selected degree of freedom (DoF) of the system. Both parked and power production states are investigated. Feasibility constraints related to mean displacements and moorings layout are considered. Results show that optimized configurations can be found with better performances and smaller platform dimensions with respect to the configuration obtained by scaling up the 5 MW geometry. [ABSTRACT FROM AUTHOR]

In this paper, an optimal semisubmersible platform is sought considering two key geometry variables: the diameter of the outer cylinders and their radial distance from the platform centre. The goal is to identify a platform configuration able to most efficiently contrast the combined wind-wave action, keeping the platform dimensions as small as possible. The amplitude of the Response Amplitude Operator (RAO) peaks and the integral area of the RAOs in a range of excited frequencies for the selected degrees of freedom are chosen as targets to be minimised. Through an efficient frequency domain simulation approach, we show that upscaling techniques proposed in the literature may lead to overdesigned platforms and that smaller and more performing platforms can be identified. In particular, the optimised platform shows a reduction of about 51% in parked and 54% in power production of the heave RAO peak, and a reduction of about 37% in parked and 50% in power production of the pitch RAO. [ABSTRACT FROM AUTHOR]