The objective of the following paper is to provide a concept to consider the uncertainties and the dynamic behavior of a technically complex system in a feasibility study by the example of an offshore wind farm. In order to do that, a model of the operating phase is analyzed and three profiles are derived. The profile "uncertainties" describes the dynamic behavior of the system, such as weather conditions, while the profile "actors and subsections" describes the dependencies and influences of the individual model elements in a cause-effect diagram. The profile "costs" transfers the knowledge of the first two profiles into the feasibility study based on the Life Cycle Costing method. The result is a detailed feasibility study of a technically complex system that provides costs, revenue and profit corridors. These corridors can be used to choose an operating strategy considering maintenance and transport processes. The target audience of this paper is for operators of technically complex systems in general and operators of offshore wind farms especially and researchers in the field of offshore wind power.
The consideration of the total life-cycle costs is an important issue for investment decisions regarding offshore wind farms (OWF). Therefore, also the costs during the operating phase and the end of life phase have to be calculated beside the investment cost. Looking at OWFs, 39 % of the life-cycle costs occur during the estimated 20 years of operation (Klatt, 2014) and accounts for a share between 25% and almost 40% of levelized cost of energy (LCOE) (Pfaffel, Faulstich and Ruhrig, 2017). This shows that the costs arising during the operation phase have an important impact on the OWF profitability. To increase the profitability, the operational costs for maintenance activities have to be reduced due to the fact that the maintenance costs cover 72 % of the operational costs (Hobohm, Krampe, Peter, Gerke, Heinrich and Richter, 2013; Morning, 2018; Svobda, 2013;). For that reason, there is a high optimization potential in terms of cost reduction. Furthermore, OWFs are influenced by dynamic factors. One major uncertainty factor is the prevailing weather condition (Beinke, Quandt, Ait Alla, Freitag and Rieger, 2017). This could lead to inaccessibility of an OWF due to high waves or high wind speeds. If an OWF has to be maintained because of a sudden failure, but the weather conditions do not allow access to the offshore wind power plant (OWPP), the downtime increases and therefore the production losses as well. In order to overcome these economic challenges, new maintenance concepts have to be developed (Business Technology Consulting, 2012; Freitag, Oelker, Lewandowski and Murali, 2015; Svobda, 2013).
