Tetrahedron 8 Prototype – Cutting cost in offshore wind lifting

Publieke samenvatting / Public summary

Driven by cost reduction, the offshore wind industry sees a rapid increase in demand for larger Wind Turbine Generators (WTGs). A problem that has arisen is that many existing wind installation Jack-Up vessels are becoming obsolete because their cranes cannot reach the heights that are required for installing/maintaining these new WTGs. The cause of this is that the lifting height of a conventional 'luffing boom' crane used on these vessels is limited by the dimensions of the jack-up vessel itself. One option is to build larger vessels on which a larger crane can be placed; this trend is seen in the last years with the orders of very large and expensive newbuild vessels. Tetrahedron comes with an alternative; a crane design that can lift higher than a conventional luffing boom crane on the same foundation. This makes the Tetrahedron crane a more efficient alternative for the installation and maintenance of offshore WTGs. Throughout its development the past three years, the patented Tetrahedron crane has reached a TRL (Technology Readiness Level) of 4 to 5.

In this project the Tetrahedron 8 NSP (Non Slewing Prototype) will be realised and tested. This is a large scale Tetrahedron crane prototype allowing the analysis of unique aspects of the Tetrahedron crane's structural behaviour and performance, such as its unique lateral overload protection system, nonlinear load characteristic and dynamic response to extreme loading conditions. Among other tests, the prototype will simulate the lift of a representative load (>160t) to a lifting height relevant for offshore wind maintenance and installation operations. The crane will be extensively monitored to validate the structural design models, load monitoring system and lifting capacity characteristics of this type of crane, which will allow upscaling of the concept to a slewing prototype which can be used for an offshore testing campaign in a follow-up project. Upon completion of this project, the Tetrahedron crane will have reached a TRL above 6 and Tetrahedron will have the required input for the realisation of a subsequent offshore test campaign on short term through which a TRL of 7 to 8 will be reached.

Korte omschrijving
The Tetrahedron 8 NSP will be fabricated, assembled and tested onshore. During the tests, realistic static and dynamic loading conditions will be simulated and extensive measurements will be performed, with which Tetrahedron will be able to verify and adapt its design and analysis models to correctly describe the unique aspects of the crane's structural behaviour, accurately determine crane load curves and adapt the design of the crane for optimal performance in the WTG installation and maintenance market. In parallel to the prototype realisation and testing, a business case analysis, a Life-cycle assessment (LCA) and a local content analysis will be performed to quantify the benefits of a circular vessel upgrade in Europe compared to a (Asia-built) huge newbuild vessel.

The primary results of the research are as follows: - Tetrahedron crane will have reached a TRL higher of 6 based on the fundamental input and proof obtained from the large scale prototype Tetrahedron 8 NSP. - Collection and processing of critical input for verifying and improving the engineering models describing the global structural behaviour of the crane - Verification and validation of load curve estimation program describing crane performance - Analysed and tested different unique methods for Tetrahedron crane fabrication and assembly