Our team of experts explain why Energy Yield Assessments (EYAs) Are Crucial in the development of wind farms. EYAs estimate the amount of electricity a site is likely to generate by analysing local wind conditions, turbine configuration, and advanced modelling techniques. These assessments are a cornerstone of renewable energy planning, helping to shape project design, support investment decisions, and inform grid connection strategies.
Wind Turbine Energy Yield Assessments: Foundations and Importance
Wind Resource Assessment: The Starting Point
The foundation of any energy yield model is the wind resource assessment. This step estimates long-term wind speed and direction using datasets such as ERA5, MERRA2, or NEWA, often combined with mesoscale modelling software like WRF or Vortex. Where available, onsite measurements from meteorological masts or LiDAR greatly improve the accuracy of this analysis.
For example, a wind rose is commonly used to visualise wind direction and frequency. It helps identify prevailing wind directions and informs turbine orientation and layout decisions.
An example wind rose generated from synthetic data is shown below.
How the Energy Yield Is Modelled
Once the wind resource is characterised, software like WindPRO or OpenWind is used to simulate how wind interacts with terrain and turbines. This includes wake effects, turbulence, shear, and other local site conditions. The model outputs a gross energy estimate, which is then reduced by various loss factors to produce a net yield.
Inputs typically include:
- Wind speed at hub height
- Site terrain and roughness
- Turbine spacing and orientation
- Power curve data
- Grid curtailment or connection limitations
- Losses (e.g. availability, wake, electrical)
The turbine power curve, for example, which maps wind speed to output power, is essential to this modelling. It defines the operational limits of the turbine and significantly influences yield estimates.
A simple example of a generic power curve is shown below.
It is also important to distinguish between gross and net capacity factors. Gross refers to theoretical output, while net accounts for real-world losses. Mislabelled or misinterpreted values can distort investment forecasts or compliance assessments.
Why Energy Yield Assessments Are Crucial to Investors and Developers
Energy yield assessments are central to wind energy project planning. A small error in projected output, even 1–2%, can significantly affect a project’s internal rate of return (IRR). For developers, EYAs guide decisions on turbine selection, layout optimisation, and grid connection strategy.
EYAs are also used by lenders, insurers, and regulators. A high-quality, transparent assessment builds confidence and supports investment-grade analysis. Conversely, incomplete or inaccurate EYAs can delay projects or undermine bankability.
At Blake Clough Consulting, we often go beyond conventional assessments by incorporating curtailment modelling, especially for sites located in constrained grid areas. This ensures developers have a realistic view of net output, not just theoretical generation.
Next Steps: How Blake Clough Can Support Your Project
At Blake Clough Consulting, we offer specialist services in energy yield modelling for wind and hybrid renewable projects. Our team includes experienced consultants with backgrounds in engineering, physics, and power systems analysis. We bring a unique perspective by combining traditional wind resource assessment techniques with an understanding of network constraints and curtailment risks.
Whether you’re preparing for project financing, submitting a grid connection application, or reviewing third-party assessments, we can help you build confidence in your energy yield projections.