Operational energy assessment

Operational energy assessment

DNV GL helps clients to understand the relationship between operational efficiency and financing.

It is advisable to have pre-construction estimates of a wind farm’s long-term energy production checked once the farm is operating. For operators and investors alike an operational energy assessment is invaluable in generating accurate projections of future energy production levels, reconciling pre- and post-construction energy assessments and validating loss factors. By reducing uncertainty levels, for example, farm operators can avoid an unnecessarily high debt-to-equity ratio when refinancing is due. 

DNV GL’s Wind Farm Engineering team carries out long-term estimates of energy production and uncertainty levels based on high-resolution SCADA data and long-term wind speed measurements. A performance and availability review removes observed losses of no long-term significance from the production data, which are then extrapolated to long-term wind expectations on the basis of long-term wind speed measurements taken on site or at a local meteorological station. The final step involves performing an uncertainty analysis and calculating exceedance levels (P50, P75 and P90 on a 1- and 10-year basis).

Since the operational assessment may well differ from the pre-construction estimates on which project financing was based, DNV GL provides a useful reconciliation service aimed at qualifying and quantifying these differences. The most common causes are uncertainties in wind measurements, vertical wind speed extrapolation, topographic and wake modelling, availability or the operational wind farm model; differences in the period chosen for long-term wind speed measurements; mechanical or environmental factors resulting in power curve under-performance; and variations in electrical efficiency.

On request, DNV GL will also undertake an in-depth analysis of the SCADA data to validate loss factors. A typical analysis would involve investigating the impact of icing on power curves and availability. The advantage for a client is that loss factors can be more accurately forecast for projects in the development pipeline.



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