Presentations

Abstract

Ambitious political declarations have been made for offshore wind in Europe. By 2050, the North Sea should have 300 GW, and the Baltic Sea should have nearly 20 GW of installed wind capacity. We need to be able to convert this ambition of capacity into cost-effective and efficient wind power production. This need, and the unprecedented capacities on unprecedented scales, requires an improved understanding of wind farm wakes and a greater confidence level in how we model wind farm wake effects at the mesoscale. This presentation describes our latest developments in wind farm parameterization in the WRF mesoscale model. One of our developments, in particular, builds on the combining elements of the WRF WFP scheme (often called the Fitch scheme) and our WRF EWP scheme. The new parameterization gives special attention to handling the Turbulence Kinetic Energy (TKE), which is problematic in the existing schemes. In the Fitch scheme, wind farms act as immediate sources of TKE. In the EWP scheme, TKE is generated by the mesoscale model boundary-layer scheme from shear production. In our new scheme, the EWP scheme is modified to incorporate a TKE source, but it is a delayed and slower release of TKE based on an analysis of sub-grid scale wind speed perturbations. The new scheme is compared with simulations using WRF-LES (Large Eddy Simulations) for a 36-turbine wind farm set-up and against the existing WRF wind farm parameterizations. The new scheme performs better in capturing the wind speed deficit of the wind farm wake and the wind farm wake recovery. These are important attributes to assess intra-farm and inter-farm wake losses, i.e., losses due to a wind farm's own wake and losses from neighbouring wind farms' wakes, respectively. The audience will learn that this new modelling is a step towards better understanding and assessing the impact of wind farm wakes for wind farm clusters. It is an important step towards providing modelling tools to aid international coordination in the use of our resources offshore.