The overestimation and underestimation of wind production can be problematic as well as having a negative effect on project evaluations, business models and project transactions in the further course – according to the speakers during a recent Windpower Monthly and Vestas webinar.
How inaccurate energy forecasts can affect projects
Overestimating production can result in different units taking “discounts” on project value, which is not standardized, said Jamie Scurlock, director of strategic sourcing at RES. “If the fixes come through, it will effectively be individual regions and individual investors who have their own opinions, and it will be different from managing industry,” he says.
“On one or two projects, an under-forecast can win because the investor gets a better deal on that project, but then the next project will not be built because it is not properly assessed for the value it could bring,” he says.
From an investor’s perspective, a project’s bankability can sometimes be improved through price adjustments, says Natalia Svejgaard, investment director at IFU. However, she says from experience that inaccurate energy forecasts, often combined with other factors such as exaggerated wind scenarios, can have an impact on senior debt mobilization, debt measurement and failure to meet the completion dates set out in loan agreements.
Accurate power generation is key to advancing the industry, says Scurlock. “We need models that are as accurate as possible and harmony throughout the industry. The problem is due in part to the various sources of energy production estimates that are included in the development of a project.
“If an ‘independent engineer’ is involved in an energy yield forecast and someone else on the customer side and another on the investment side – if there is disagreement between these independent engineers about how to deal with blockages or lag, or other problems, then the Change project value fairly quickly during this period if the investor and developer and all parties want certainty during the transaction period. “
Accounting for inaccuracies in the business model of a project
Jean-Philippe Salomé, Vice President of Industry at EDF Renewables, says that after 20 years with EDF Renewables, the team understands the importance of the quality and accuracy of power generation evaluations. In the future, this will become even more important for wind as it competes with PV projects in technology-independent auctions.
In the case of a project or portfolio where the uncertainty is higher than the developer would normally expect, a bias, which can be up to 5%, is applied to the adjustment factor / P50. “We can include a buffer for production if the uncertainty is too high.”
“Sometimes it is when we have a level of uncertainty that is below our target. This can happen when we have flat terrain and a lot of wind or an extremely good measurement campaign. In the case of repowering, it is important to us that we can rely on precise long-term real production data from the location. This brings more security and value to the project, ”says Salome.
“Reliable energy estimates definitely affect the way we evaluate a project and ultimately the business case,” he adds.
Identify factors that distort the energy forecast
Factors that can contribute to large discrepancies in energy forecast bias and loss factor calculations within the industry can in part be attributed to the trend towards taller turbines with larger swept areas designed to extract more wind resources. Scurlock compares the challenge to using an instrument the size of a tennis ball to measure and predict a swept area the size of three soccer fields to determine turbine performance, which is further affected by variations in wind speed and extreme weather conditions can .
The methods of monitoring and measurement that were appropriate five to ten years ago may now be out of date, says Scurlock, who notes the increasing use of lidar / remote sensing as an important addition to meteorological masts for campaigns to establish more accurate measurements. However, more recent developments can also lead to the challenge of harmonizing methods and approaches across industries.
The fluctuations the industry experiences in interpreting the data gathered from measurement campaigns for energy forecasting can lead to higher capital costs, according to Svejgaard.
Requirement for a higher accuracy of the energy forecast
Improved modeling and reporting of uncertainties is a priority, says Svejgaard. If the expected performance ratio cannot be achieved in a solar PV project by the time the commercial operating date (CoD) is reached, additional modules can be added. “But a wind project isn’t just about adding another turbine or two – that’s not really a likely scenario.”
She says improved modeling and reporting of uncertainties is a priority. “We want accurate evidence-based uncertainty models that may be based on time-based energy forecasting approaches using risk assessments to identify, report and potentially mitigate technical risks … as well as improved location measurement tools and more accurate wind flow and wake models.”
Advances in harmonizing energy forecasts
Good examples of efforts towards harmonization and standardization in relation to energy prediction are the Power Curve Working Group and also the work of the Consortium for Advancement of Remote Sensing (CFARS) to inform the industry of the advantages and also the shortcomings when using the technology insert.
“CFARS is a great example of collaboration that has shown some great results so far and will continue to evolve, providing the industry with better insights and better ways of working. It is a good example of an industrial group that emerges from people whose interests are aligned, ”says Dr. Chris Ziesler, Director Advisory Services, North America UL Renewables,
The industry has made progress with standardization, says Ziesler. “As technical consultants, it is our job to be consistent and provide good reading for everyone.”
He refers to the IEC-15 committee, which brings “more refinement and precision” and is a good example of standardization and collaboration. “It gives us a helpful and common framework to talk about loss factors in particular. The majority of people now understand what to do to get good data on Met campaigns, but there is still a lot of discussion and argument about loss factors, so it is important to have a common framework. ”
Paul Leask, Service Line Leader for Project Development and Analytics, Energy Systems DNV would like to see a better or better understanding of the measurement uncertainty of remote sensing. “These devices are increasingly being used by developers, and as an industry, we need to support and enable this if developers want to do that.”
DNV advocates also advocate a common definition of validation or its implementation, so that a comparison between the different methods is possible. “This would remove the noise in the competitive environment,” he says.
Bridging the power curve measurement and the real turbine power
Another challenge is to narrow the gap between power curve measurement standards and turbine performance under real-world conditions. To address this, Vestas has published work to have a track record of predictability of performance curves by being more transparent about its modeling and methods of predicting performance curves.
Vestas Senior Product Performance and Warranty Specialist Michael Pram Nielsen says, “In practical terms, this has reduced the power prediction loss factors.” This was achieved by the OEM providing more than 300 IEC-compliant performance test results for audits. “We have also seen the positive effects on several wind farm construction projects,” he says.
Stroller Nielsen says this focus on energy prediction risk factors that may lead to it to various loss of income is important in the future. “Perhaps the variation is less important from year to year, but we need to improve our understanding of what causes this variation. We need more industry standardization in terms of uncertainty and loss variation methods. ”
By building trust in different parts of the renewable industry, energy consultants can build trust in models that OEMs work with, he says.
• Click here to watch the full length webinar.