Old Wind Farm Life Extension vs. Full Repowering: A Review of Economic Issues and a Stochastic Application for Spain

Abstract

The installation of wind power technology is growing steadily and the trend can be expected to continue if the objectives proposed by the European Commission are to be achieved. In some countries a considerable percentage of installed wind power capacity is near the end of its useful lifetime. In the case of Spain, the figure is 50% within five years. Over the last 20 years, wind energy technology has evolved considerably and the expected capacity factor has improved, thus increasing annual energy production, and capital expenditure and operational expenditure have decreased substantially. This paper studies the optimal decision under uncertainty between life extension and full repowering for a generic wind farm installed in the Iberian Peninsula when the future hourly electricity prices and the capacity factor evolve stochastically and seasonally. The results show that in economic terms, full repowering is the best option, with a net present value of €702,093 per MW installed, while reblading is the second best option. The methodology can be transferred to other specific wind farms in different electricity markets and can be used to develop national wind energy policy recommendations to achieve projected shares in the electricity mix.

Data-Driven Assessment of Wind Turbine Performance Decline with Age and Interpretation Based on Comparative Test Case Analysis

“…Unfortunately, a non-negligible fraction of operating wind turbines undergo performance decline in their lifetime: this can happen for a variety of reasons and the decline process can have a variety of characteristic times, which can be clearly highlighted only through appropriate SCADA data analysis. This kind of consideration should be incorporated in intelligent repowering or lifetime extension decisions [4,[31][32][33].…”

“…This has gradually become a more timely problem as a growing number of wind turbines have been reaching the end of their expected lifetime: actually, for example, the percentage of wind turbines aged fifteen years or more is in the order of 50% in some European countries as Germany, Denmark and Spain. The decision between the options of extending the lifetime of old wind farms or repowering or decommissioning [4] can be supported by an improvement in the knowledge of how the technical performance of wind turbines declines in time.…”

Design for Repowering of Wind Farms: An Initial Framework

“…For partial repowering, RUL is essential to informing whether an aged component can function safely as required if reused, or whether it must be replaced during the repowering process. Typically, full repowering provides more value to a project than partial repowering [5,12], in which case it is not as important to track RUL of components, as they are all replaced at end-of-life. However, tracking RUL for "planned repowering" cases can prove beneficial even in full repowering cases, as turbines can be replaced earlier than EOL if the RUL shows signs of degradation.…”

Self-reconfiguration simulations of turbines to reduce uneven farm degradation

“…Scenario 1 (S1) -A WT's life was extended (beyond C fatigue = 1) as modelled in other life extension studies [57,58]. Changes to O&M costs were broken down into three additional costs.…”