Airborne wind energy systems use tethered flying devices to harvest wind energy beyond the height range accessible to tower-based wind turbines. Current commercial prototypes have reached power ratings of up to several hundred kilowatts, and companies are aiming at long-term operation in relevant environments. As consequence, system reliability, operational robustness, and safety have become crucially important aspects of system development. In this study, we analyze the reliability and safety of a 100-kW technology development platform with the objective of achieving continuous automatic operation. We first outline the different components of the kite power system and its operational modes. In the next step, we identify failure modes, their causes, and effects by means of failure mode and effects analysis (FMEA) and fault tree analysis (FTA). Potentially hazardous situations and mechanisms which can render the system nonoperational are identified, and mitigation measures are proposed. We find that the majority of these measures can be performed by a failure detection, isolation, and recovery (FDIR) system for which we present a hierarchical architecture adapted from space industry.

@en

Due to the emerging interest in Airborne Wind Energy, a considerable number of prototype installations is approaching a commercial stage. As a consequence, operational safety and system reliability are becoming crucial factors for technology credibility and public acceptance. In our case study, we investigated the reliability and safety level of the current 20 kW technology demonstrator of Delft University of Technology, which is also the starting base of the EU Horizon 2020 project REACH. The objective of the REACH consortium is to develop a commercial 100 kW version of the demonstrator. The project team systematically improves the system’s reliability and robustness with the aim of demonstrating 24 hours of continuous automatic operation without any pilot intervention. To achieve this goal, reliability and the safety level of the system are analyzed using two traditional methods, FMEA (Failure Mode and Effects Analysis) and FTA (Fault Tree Analysis). From the conducted analyses, hazardous situations and the mechanisms that lead to unoperational or hazardous states are defined. Consequently, mitigations are offered to prevent these mechanisms. It is found that a majority of the proposed mitigations can be performedby a FaultDetection, Isolation and Recovery (FDIR) software component. Development process improvements are offered for the components for which it is impossible to decrease the risk using the FDIR. In this talk, author will present the key points and the important results of the reliability analyses. In addition, proposed FDIR architecture will be discussed. @en