A bankable wind resource assessment is a comprehensive, independent evaluation of wind energy potential at a specific site that meets the rigorous standards required by investors, lenders, and financial institutions to approve project financing.
Understanding Bankability in Wind Energy
Bankability refers to the quality and credibility of technical assessments that enable project financing. In the wind energy sector, a bankable assessment must demonstrate:
- Technical rigor: Methodologies aligned with IEC 61400 and industry best practices, using tools such as WAsP, WindPRO, and Openwind for flow modelling.
- Transparency: Clear documentation of assumptions, methodologies, and data sources including long-term reanalysis datasets (ERA5, MERRA-2).
- Uncertainty quantification: Comprehensive analysis of risks and confidence levels across all uncertainty categories.
- Independence: Conducted by consultants without conflicts of interest with the developer or turbine manufacturer.
- Reproducibility: Sufficient detail for third-party review and validation by the lender's own technical advisor.
Core Components of a Bankable Assessment
1. Long-Term Wind Climate Analysis
A bankable assessment begins with comprehensive analysis of long-term wind patterns at the project site, typically using 10–20 years of validated wind speed and direction data. Long-term correction (MCP — Measure-Correlate-Predict) is applied using reference datasets such as ERA5 reanalysis or nearby synoptic stations to translate onsite measurement periods into a representative long-term wind climate.
2. Energy Yield Assessment: P50, P75, and P90
The energy yield analysis provides probability-based estimates of annual energy production:
- P50: 50% probability of exceedance — the median estimate, used as the base case for project economics.
- P75: 75% probability of exceedance — conservative estimate commonly used by equity lenders.
- P90: 90% probability of exceedance — very conservative, used for debt sizing and stress testing.
3. Uncertainty Quantification
Comprehensive uncertainty analysis quantifies confidence levels across all major categories: measurement uncertainty, long-term climate variability (inter-annual variability), wind flow modelling uncertainty, wake loss uncertainty, and turbine performance deviations. The combined uncertainty determines the P50-to-P90 spread that governs debt case resilience.
4. IEC 61400 Site Suitability
Site suitability assessment ensures turbine design class compatibility and compliance with international standards for wind conditions, turbulence intensity (TI), extreme wind events, and vertical wind shear and veer. Non-compliant assessments risk warranty exclusions and insurance gaps.
Why Bankability Matters
Without a bankable assessment, most wind projects cannot secure the financing needed for development. Financial institutions rely on these assessments to evaluate project risks, determine loan terms, and make investment decisions. A lender's technical advisor (LTA) will independently review the methodology and assumptions — the quality of the EYA determines whether the debt case holds up under that scrutiny.