In light of the wind turbine upgrades, DNV GL recommends that upgrades have led to claims of 1-2% annual energy uplift. Yet, some of DNV GL's customers faced the impact of this kind of upgrades.
First of all, it is of a great importance for one to understand the performance of the wind plant; In this way, the owners of the wind turbine is able to manage the uncertainty over a long-term period, being able to sell or re-finance your wind plant if needed.
Also, when upgrading all turbines, if not consistent data are gathered, it will be impossible to demonstrate that these upgrades have been rightly installed and any improvements in performance are not quantifiable. DNV GL comments that 'the wind speed readings from the turbines are not suitable for this'.
In addition, DNV GL informed that its customers, during the re-financing process, noticed that the upgrade package was incorrectly installed, which affected the effect of performance. The upgrade included all turbines and had an impact on anemometry, so there was no way to conduct an energy yield assessment in order to understand the forecasted electricity production and any uncertainty to the level demanded for a financial valuation.
Consequently, the turbine manufacturer was the one to fix the problem, but the customer had to collect the operational data for an additional year to get a robust energy yield value for the site.
In the meantime, another customer found out that the performance upgrades a year ago introduced an inconsistency in the reference data and reduced the amount of data which could assessed against long-term predictions. This led to an increased level of uncertainty in the energy yield assessment.
In essence of the challenges customers face - and as explained above - DNV GL recommends:
- Validation on the wind farm can avoid both situations; A solution to test the impact of the upgrades is to conduct a toggle test or a test where the system is installed on half the turbines within a site, for instance.
Under the possibility that the impact of the upgrade is known, then the operations can be used in the analysis resulting in a lower uncertainty and higher measure of the estimated wind yield exceeding expectations 90% of the time, known as the P90 value; an essential measure which forms the basis of most financial valuations. It also provides confirmation that the upgrades have been correctly installed.
DNV GL concluded
there are significant gains to be made and it is possible to show those gains in the energy yield assessment. However, to avoid introducing additional uncertainty, care needs to be taken to quantify the improvements.