‘‘Focusing on correlation coefficient is important but not sufficient, did you think about consistency?
IREC Index was created in 2011 in order to provide our clients a trustworthy and powerful tool to better understand the evolution of production capacities of their wind farms .
The force of our product lies in the permanent check of consistency in the mulltiple independent sources we use to generate it’’
Habib Leseney, CEO, Eoltech
What is an energy index ?
An energy index is a tool whih allow you to put your wind farm production data into perspective of the wind resource. It corresponds to the ratio between the wind energy available over a given period (month, quarter, year) and the long term one.
For example, a 95 % IREC Index for a given year means the wind resource over this year have implied 5 % of production shortfall regarding the expected long term production.
The added value of IREC Index
Most of people concerned by the production of a wind farm look for reference data that fit their wind farm productions at best (meaning that the correlation coefficient between production and reference data is as high as possible).
Even if this condition is important, it is not sufficient to qualify an index as reliable. Did you think about homogeneity in time ?
At least as efficient as index based on mesoscale data, IREC Index offer additionally guarantees in terms of homogeneity control. Indeed, by using and combining several independent sources, the IREC Index philosophy allows removing inconsistent sources and increasing the robustness of the results.
From our experience, this approach represents the best way to ensure that a possible drift observed between your production data and IREC Index comes from your data.
IREC Index can so be considered as a trustworthy reference source of information about available wind resource.
For each region, IREC Index is based on data from a minimum of 4 distinct and totally independent sources(1) of information, whose homogeneity in time and space is inspected each month. Data from these source are then converted in production(2) and combined to obtain a robust database of reference production per region.
(1)To ensure a continuity in this process, “back-up” sources are also inspected.
(2)thanks to correlation with wind data at hub height and a theoretical power curve.
A tried and tested tool
In the context of our research, we have been able to compare the monthly output of over 130 wind energy parks in operation (>1 600 MW) with the most relevant reference outputs generated for the IREC. This set of tests, carried out over the past three years, finds that the average level of correlation between these two sets of data is around 97% on average.
Validation of the reference production generated for the IREC
The graph below shows the number of samples taken by the level of correlation between the monthly outputs measured (adjusted in line with an availability level of 100%) and the most relevant reference outputs generated for the IREC.
Precautions for use
Before using indexes, be sure that your production data is adjusted to 100 % availability rate (Acoustic or specific management plan included). Otherwise, conditions of comparisons cannot be considered as optimal.
The use of this index on an individual park level is subject to uncertainty as it can vary somewhat or more substantially depending on the location and the levelof exposure to the wind.
The company Eotech is not responsible for how the information detailed here is used. Visitors are responsible for the consequences of any usage of this information.