Founded in 2003, Liftra is recognised by the international wind turbine industry as a professional specialist in lifting and transportation solutions. Liftra has undergone rapid growth as a contributor and trusted partner, with locations in Denmark, the USA, Spain, China and Poland.
Liftra has revolutionised the installation of wind turbines by creating the LT1500 crane that ‘climbs’ the wind turbine tower as it is being assembled instead of sitting beside it. The bottom of the crane grabs onto a flange of one tower section and lifts the next section into place. Then, a hoist block travels up and attaches to the higher section and pulls the crane up the tower to attach to the higher flange. In a sequence of such grabbing and hoisting moves, an entire wind turbine, including the tower, nacelle, rotor, and blades, can be constructed. With 50 engineers working primarily in Spain and Denmark, Liftra is developing this crane for use by the original equipment manufacturers of wind turbines and maintenance staff wind farms.
In designing the smaller climbing crane that would take up less ground space and require just one truck to move to the next installation site, Liftra engineers needed to be able to ensure that the tower elements would not be crushed by the applied climbing forces, including the load on the tower and flanges, and the gripping forces.
They therefore ran finite element structural simulations both in Ansys Cloud and on their own workstations to model the loads involved when a crane is attached to and climbs up the long tower of a wind turbine as it is being assembled. They ran both linear material models and non-linear material models for elastic or plastic analysis of the towers to determine whether the crane would cause any permanent deformation to the tower, and, if so, how much. The linear material model – which included 1.8 million nodes – was run in Ansys Cloud on an HC-series virtual machine of Microsoft Azure featuring 44 Intel Xeon Platinum 8168 processor cores. Using Ansys Cloud, the simulation was completed in one hour, compared to five hours on company workstations.
Finite element simulations subsequently confirmed that the LT1500 crane climbing the tower would not cause any deformation of the wind turbine tower. Being able to set up these large models to run as a single simulation on Ansys Cloud made for a better and safer design. Instead of splitting the analysis up into multiple simulations and then having to calculate the interface forces, Liftra engineers were able to do everything in the same simulation.
“Previously we were forced to do more simplification and isolate parts to perform calculations on each separate part,” said Miguel Hoffmann, senior engineer specialist at Liftra. “Now, we can simulate the entire global assembly as a whole.”
Liftra found that the best simulation set-up was a combination of Ansys Cloud, Ansys Elastic Licensing and its own licenses. With design offices in Spain and in Denmark, the firm found it useful to be able to borrow licenses and avoid waiting until someone finishes a simulation before starting something new.
A cost analysis also revealed many barriers to Liftra maintaining its own on-premises cluster. These included maintenance costs and the need for extra licenses. Using Ansys Cloud provided a considerably less expensive option while also delivering higher computing power, allowing Liftra to run many parallel jobs with almost unlimited power.
“Delivering on time is very important, but delivering an improved, safer, optimised design is even better,” said Hoffmann “Thanks to Ansys Cloud, we can achieve more complex designs and simulate more complete models up to five times faster.”
This article was originally published in the Spring 2022 issue of Technology Record. To get future issues delivered directly to your inbox, sign up for a free subscription.