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Turbine nameplate capacity, hub height and rotor diameter have all increased significantly over the past 15 years, and since 2000, the average nameplate capacity has more than doubled. As a result, many lower wind regions previously thought non-viable are now experiencing healthy wind project development and operations.

Despite the many positives of the technological advancements, every design change to a turbine, even an evolutionary one, creates some level of risk in either the design or, possibly, the supply chain. As an independent engineer, it is important to consider whether the velocity of new product development may lead to a greater probability of defects, which, in turn, could increase long-term operations and maintenance (O&M) costs. Because many projects have warranties as short as two years, long-term maintenance costs can be a significant risk for the long-term financial health of a wind project.

As new or hybridized components (those paired together to enhance capability or profitability) are scaled up in order to maximize energy capture at lower costs, careful consideration of the testing that has been conducted on each component is essential to make sure it is as representative of the real world as it can be. Additionally, as uprates are implemented, it is important to consider the impact of reduced design margins on turbine and component life, in addition to long-term O&M costs.

The main driver behind the evolving turbine technology is to meet ever-more aggressive cost targets. In order to be competitive with other sources of energy and secure power off-take arrangements, wind energy project economics demand a lower cost of energy. Manufacturers have answered the call and have found ways to reduce the cost of energy, primarily through introducing larger rotor diameters.

This has allowed wind energy to remain a cost-effective option, even in lower wind regions, in a market where power purchase pricing has reached all-time-low values. Other advancements, such as improved control strategies and aeroelastic tailoring of blades (blades that are designed so their deflection or structural deformation from sudden gusts helps to reduce system loads), have also dramatically increased turbine energy production. By controlling costs and increasing energy production, turbine manufacturers have significantly reduced the cost of energy and have resulted in the recent expansion of wind energy projects on a global basis.

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Shorter prototype testing

In the early days of wind energy, every turbine model was prototype tested in the field, often for several years. Some manufacturers even deployed small numbers of turbines to gain field experience before committing to serial production runs. This resulted in a very long cycle between product development and introduction into the market. In today’s rapidly changing marketplace, long product development cycles could mean that a new turbine design is no longer competitive by the time it reaches the market. In order to avoid this, prototype testing cycles have been shortened, again introducing a degree of risk. Manufacturers are mitigating this risk by building greater internal expertise and intensifying component, subcomponent and full-scale prototype testing, albeit over a shorter timescale than the testing cycles in the past.

Lengthy prototype testing is avoided by conducting highly accelerated life testing on each component. Consequently, it is not unusual now to have production turbines shipped to the site for installation before the prototype has been running for a full year. Where issues have arisen, the top-tier manufacturers have demonstrated the capability to address these issues in the field under warranty. Although this shortening of prototype testing is supported by more complete sub-system testing, it does not replicate all of the unique aspects of the complex wind environment under which turbines actually operate. Therefore, the risk of unforeseen issues remains, but one could argue this was the case even under the earlier paradigm of longer testing cycles.

With all of these factors changing at a rapid pace, how does an independent engineer evaluate and quantify risk? The answer lies in digging below the surface and understanding the turbine model family and its track record. How has it evolved over time? What are the similarities and differences from previous designs of this type? What is the rationale for and the engineering behind the changes implemented? In addition to these more fundamental questions, it is critical to understand the performance and technology issues that have occurred in the field and the underlying cause of each issue, as well as to implement an assessment of the success and durability of any solutions that have been implemented to address these issues. This investigation extends to the testing that has been conducted on each component and ensuring that the testing has included the magnitude of loading that will be experienced as the component is scaled up. Fleet leaders can generally be relied on as a guide to the issues that the turbines may experience on new projects and with different site characteristics, but it is also important to independently track the history of each component supplier to monitor its product quality so that any issues are identified and mitigations strategies understood.

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The certification process was intended to document design calculations for a turbine model, ensuring compliance with consensus requirements for safe operation over a target life of at least 20 years. This detailed look into the hardware and design loads is labor-intensive and can be a challenge for manufacturers looking to keep up with a continuously evolving turbine market and multiple sub-suppliers. Guidelines for the International Electrotechnical Commission allow an increase of 5% of rated power without recertification, but any structural change or other significant modification will trigger the need for recertification. In order to provide certification for the evolving turbine models being offered, turbine manufacturers are constantly certifying or recertifying their turbine models as they evolve and change to meet market needs. Although the certification cycle may lengthen product development cycles, it does play an important role in the risk mitigation of new technologies and acts as a form of checks and balances for the manufacturers.

 

Quantifying risk

Although the velocity of turbine model development has increased, the wind industry has also developed mechanisms to mitigate the risk of rapid product development. These mechanisms include highly accelerated life testing of components, careful quality control of components and their supply chain, and statistical risk assessment. Certification bodies have played an important role in ensuring new technologies still meet consensus requirements for safe operations. The final step in quantifying these risks is evaluating their impact on the project’s economics.

By understanding the problems that can be experienced on each component and the turbine as a whole, the likelihood of issues and resulting lifecycle costs can be estimated. These costs should be adequately addressed in a project’s commercial and financial structure. In addition, the appropriate stress cases should be run on a project’s economics to ensure that the project is able to withstand a number of possible downside scenarios that may occur in real-life deployment. By evaluating the impact of potential defects or serial defects, reduced production, or increased O&M costs, the risks of these new technologies can be adequately quantified and mitigated, which should ensure the long-term fiscal health of the wind project.

 

Dan Bernadett is chief engineer and Emil Moroz is senior turbine engineer at Albany, N.Y.-based AWS Truepower. They can be reached at dbernadett@awstruepower.com and emoroz@awstruepower.com, respectively.

Turbine Technology

Evaluating Wind Project Risk With Changing Turbine Technology

By Dan Bernadett & Emil Moroz

By understanding the problems on each component and the turbine, the likelihood of resulting lifecycle costs can be estimated.

 

 

 

 

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