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METMASTS FEATURE


ALL ABOUT THE DATA


When tackling the tricky early demands of the project, it might be easy to forget that what really matters is the data coming from a few fragile instruments mounted on the mast.


FOUNDATION OPTIONS


To date, several different foundations have been installed to support masts, including: monopiles, jackets, suction buckets and the Keystone “twisted jacket”. there are many factors that influence the selection of foundation solutions, but the largest cost is that of installation. To keep costs as low, a flexible approach to installation vessel options is essential to securing competitive charter rates.


The offshore environment is an onerous one and the mast and foundation must be designed for these conditions. Industry concerns have been raised about the durability of met masts offshore. The lattice towers must also be checked for loads resulting from the foundation oscillating due to wave action. These oscillations induce a cyclic load effect in the lattice, causing fatigue to its joints and members. These fatigue loads can be significant and must be assessed during the design stage by using an integrated design process.


Getting the specifications and detailed mounting arrangements right is crucial. At GL Garrad Hassan we have analysed data from a large number of offshore masts and found examples where this part of the design process has not been given sufficient attention. Some masts have delivered data which failed to follow best measurement practice, thereby impacting project profitability. In delivering on the “hard part” of the meteorological mast, they failed to deliver on what is sometimes perceived to be the “easy part”.


Data must also be complete and reliable. probably the most common cause of data gaps are issues relating to the supply of power to the instruments. Delivering a reliable power supply solution is always worthwhile.


AN OPPORTUNITY


Integrated model above INTEGRATION


Integrated design is as essential for offshore meteorological masts as it is for wind turbine structures. GL Garrad Hassan have performed assessments of offshore towers and foundations using the bladed fully dynamic simulation programme, the results of which have established the importance of damping, the system’s resistance to oscillation. The level of damping used in the integrated analysis is critical to accurate calculation of the fatigue loads in the mast and foundation. Damping sources are described in the equations below:


Savvy developers are starting to understand how challenging offshore meteorological masts can be, but also how crucial the data is to project profitability. they also recognise that many of the issues encountered in their design and installation mirror future challenges that projects will face.


Investing the time and money needed to build a team with the competencies to overcome these challenges should be a priority for all developers.


GL Garrad Hassan www.gl-garradhassan.com


GL Garrad Hassan found that omitting the aerodynamic damping component in the integrated analysis can overestimate fatigue loads in the mast by up to 30%.


www.windenergynetwork.co.uk 103


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