Wind Power Project Development : Financial Viability of Repowering with RETScreen as a Decision Aid Tool

Abstract: There is a need for an efficient adjustment of the energy supply system towards renewable energy resources in the near future. This raises the question whether it is financially efficient to repower an onshore wind turbine or wind farm in operation with respect to specific surrounding conditions? To this purpose, the objective of this Thesis is a quantitative analysis of a wind power project repowering addressing certain legislative parameters, varying economic factors and WT models respectively. To enable this analysis, a case-study considering a number of hypothetical scenarios for repowering a wind farm in Germany has been applied. The scenarios address in particular the widely implemented limitation in overall building heights of 100m depending upon varying economical parameters. Nevertheless, this case-study applies three different WT models whereof one model matches the legislations and the other two models exceed the legislations by a varying degree in order to evaluate a potential productivity growth. The varying economic conditions are represented by a base case projection applying average wind power construction costs and financial rates whereas a best case and worst case projection consider deviating interest rates, capacity factors, investment and O&M costs respectively.   The economic calculations together with the determination of the capacity factor with respect to each WT model are performed by utilising the decision aid tool RETScreen. The results obtained by this case-study show versatile economic and technological performance. WT models of minor size addressing in particular local existing legislation regarding the limitation of overall height which must not exceed 100m are inefficient regardless of varying economic conditions. Exceeding the limitation, WT models provide a significant increase in performance and thus return positive economic results independent of varying economic conditions. The main conclusion is that existing local legislations based on previous considerations from the past but which no longer correspond to the state of technology have to be questioned in general or have to be mitigated by subsidy instruments in order to support a generation shift in technology before the end of life of operational wind farms and thus promptly increase efficiency by repowering.