applications ➤


offshore wind farm developers because of the way our soſtware works. Our soſtware simulates fluid flow, so an onshore wind turbine is only affected by the wind but an offshore site is affected by two fluids – the wind and the water.’ Te effect of the ocean adds a further layer


of complexity. Simulations must also take into account the mooring, balance, dynamics, and servicing of the turbines in the aqueous environment, and how this will affect the site’s power output and productivity. Ryan added: ‘Te risk is higher because, if the turbines fail to perform as expected, replacing them or servicing them is frightfully expensive – far more expensive than doing it onshore. Te need to do it right the first time is compounded.’ Te pressure to provide a cost-effective offshore


wind farm oſten comes down to the water depth. Shallower sites are the obvious choice, from the pricing perspective, as the waves are not as severe and cause less damage to the platforms; the site is also more stable as the turbines are based on the seafloor, instead of relying on more novel stabilising techniques; and there are fewer power transmission concerns as the site is closer to the shore. But offshore farms are oſten forced to move further away from the coastline because of their effects on local communities. Tis puts further pressure on the simulation


soſtware, particularly the transmission effects. Te offshore wind farms are oſten connected through high voltage direct current (HVDC) systems. Dudgeon added: ‘[Customers] have to extend the simulation of the wind farm beyond just the wind farm. Tey have to model the transmission technology and part of the electric grid.’


Getting to the grid Transferring the power generated by a wind farm from the site to the grid is a challenge for all wind farms – both on and off the shore. A novel piece of research using data analysis and graphing soſtware could resolve this issue.


Sound pressure level at 100Hz


High population regions, which also have a high demand for energy but are close to the grid, may be suitable for wind energy production, despite having a low average wind speed, the research revealed. A three-dimensional animation from


OriginLab was used graphically to represent complex wind-speed dynamics for South Palm Beach in Florida, USA. Te simulations found the investigated location had enough predictable wind supply to contribute to meeting the area’s peak demands. Te researchers needed a unique data-display


technique, as their nonlinear dynamic analysis was an untested approach to wind power evaluation. Tis differed from conventional approaches to analysing wind-speed data, as Ray Huffaker, professor of Agricultural and Biological Engineering at the Institute of Food and Agricultural Sciences at the University of Florida, explained: ‘Conventional probabilistic wind-project evaluation approaches remove patterns from wind-speed data, and consequently are not equipped to detect wind- power patterns empirically. Our work met a


THE SEPARATION AND PLACEMENT OF THE TURBINES MUST BE CAREFULLY MODELLED


critical need in project evaluation to begin modelling wind-speed dynamics that accurately reflect real-world patterns.’ Te researchers investigated the commercial


viability of Sugarland Wind, which is the first utility-scale wind project proposed in Florida. Te proposal was for a 200 megawatt wind farm with 114 turbines spread across 12,887 acres of sugarcane fields in the Everglades Agricultural Area. Huffaker said: ‘Te project received strong community support for contributions to clean energy in the region, community development and the agricultural economy, since sugar cane farmers would lease space in their fields for turbines.’ ‘We found empirical evidence that wind-


power patterns at the project site match up well with regular daily and seasonal electricity demand patterns,’ he added.


Farm optimisation Once the site has been agreed, the exact details of the wind farm must be optimised in terms of the turbine model, type and configuration. For a wind farm, you are moving away from


The sound field produced by gear teeth meshing at 100Hz, modelled by Xi Engineering using structural- acoustic interaction in Comsol Multiphysics


32 SCIENTIFIC COMPUTING WORLD


the small confined areas CFD simulations usually deal with to a grand scale simulation, covering kilometres of open terrain. Turbulence


Dirichlet inlets for U, T


Neumann outlets for U,T


Large eddy simulation set-up of wind flow over terrain


is, again, a key consideration, alongside wake effects between turbines. Basic turbine wake models depend on the turbulence level and thrust of the turbine. Trust is the downwind hitting the turbine, which directly converts to a loss of wind speed in the wake. Te wake from one turbine is detrimental to the turbulence of the other turbines and to wind speed in the farm. Te separation and placement of the turbines must be carefully modelled using large eddy simulations and full incompressible flow models. It is not just a case of choosing the equipment


you do need, but the equipment you do not need, as Dudgeon said: ‘If you have a great deal of confidence in your simulation model, you can get to a much more optimised architecture where equipment that you think may be needed – to match a production goal or a grid requirement – may not actually be needed.’ ‘Te technology choice has a significant


bearing on how you put a wind farm together, especially on how you manage a wind farm and operate each turbine to make sure your wind farm, as a whole, is doing what you expect,’ he added. From turbine selection, to electromechanical


modelling or evaluating unusual sites, simulation soſtware continues to power the decisions behind where wind farms will be located within the stringent rules and regulations governing these structures. Tose looking to build wind farms have to


solicit investment, win funding and deliver on their promises. It is a high risk scenario and the pain of making mistakes is real and recurring. Solid simulations mitigate this risk when choosing where to put a wind farm.l


@scwmagazine l www.scientific-computing.com Precursor


Temporary storage


Triangulated to ALM simulation boundaries


Vestas Wind Systems


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