Global Blockage Effect in Offshore Wind (GloBE)

Understanding how the wind flows through, over and around large offshore wind farms.

The Global Blockage Effect (GBE) has become a hot topic in offshore wind in recent years. While there is a broad industry consensus that the GBE causes decelerations in front of offshore wind farms which reduce the energy yield, different opinions exist on how to consider its downstream impacts and how to account for its redistributive effect. This is commercially relevant as uncertainty in wind farm performance drives a high cost of capital for offshore sites. Any over estimation of the GBE leads to the de-valuation of offshore wind projects.

The GloBE project has succeeded in:

Measuring the decelerations and accelerations of the wind around the Heligoland windfarm cluster
Understanding their sensitivity to atmospheric parameters such as the height of the boundary layer
Testing various hypotheses and modelling approaches against the measured data
Building an industry consensus around how blockage should be modelled

These advances allow offshore wind developers to reduce the uncertainties assigned to blockage effects, making it easier to finance the construction of new offshore wind farms.

The top-level conclusions from the project are summarised in a Joint Statement, accessible here. This has been supported by the GloBE Partners and the Independent Technical Review Group, who represent the leading technical advisors active in the financing of large offshore wind farms. Initial results were presented at the Wind Energy Science Conference in Glasgow on 24 May 2023. The slides are available online here.

We will follow up with two public webinars explaining the measurement campaign and the conclusions drawn regarding the modelling of blockage. Watch this space…

Lead Partner

RWE

Partners

EDF Renouvelables, EnBW, Equinor, Ørsted, Shell, ScottishPower Renewables, Vattenfall, Vaisala, the Technical University of Denmark, TotalEnergies, Ocean Winds, The Crown Estate