RIASSUNTO
Abstract
In this paper, the effect of an Offshore Wind Farm (OWF) on the surrounding wave field is numerically investigated in frequency domain, using a BEM numerical model based on the potential flow theory. The analysis is performed for regular waves of various periods and incident wave directions and for irregular waves with variable peak period and significant wave height. Specific cases of regular and irregular waves are compared, revealing the differences between the regular wave model and the real sea state. By numerically simulating the incident wave and the scattering effects caused by the OWF, indications are provided regarding the impact of the OWF on the local wave climate.
Introduction
In recent years, the increasing energy demand has led to a growing interest towards the efficient exploitation of renewable energy sources. Under this framework, offshore wind energy has become an increasingly attractive option, offering multiple benefits and addressing effectively the well-known obstacles and problems associated with the exploitation of wind energy onshore (Henderson et al., 2003; Breton and Moe, 2009). Consequently, the offshore wind energy sector is continuously growing and this has resulted into large-scale commercial deployment of Offshore Wind Farms (OWFs), especially in the coastal and offshore areas of northern Europe (EWEA, 2015). So far, most OWFs operating in Europe have been installed at shallow waters of average depth equal to 22.4 m and at an average distance from the shore equal to 32.9 km (EWEA, 2015). Moreover, the deployed support structures correspond mainly to fixed bottom configurations, i.e. monopile, tripod and jacket (EWEA, 2015).
Although OWFs may contribute significantly to the coverage of the increasing energy demands, their installation and operation should be implemented by considering not only economic and engineering factors, but, additionally, by assessing and predicting reliably possible negative environmental impacts in the corresponding marine environment (e.g. undesirable effects on local wave climate, changes in sediment transport patterns, loss of biodiversity, etc). Considering that today most OWFs operate at shallow water depths and at relatively small distances from the shore, the aforementioned environmental impact assessment becomes crucial also for local communities, since the existence of any possible negative environmental impacts may affect directly the human activities (e.g. fishing, leisure activities, such as surfing, etc) and operations in the corresponding coastal environment.