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Modifying Electrical Architecture to Maximise Wind Farm Production
As wind energy seeks to become cost-competitive with traditional forms of generation, developers and operators in the maturing European onshore market continue to look for ways to optimise project performance and bring down long-term costs. While there are many ways to boost the efficiency of operational portfolios, arguably the most effective way to make cost reductions is to return to the drawing board and explore how subtle design modifications based on operational experience can influence the long-term performance of a project before it is constructed.
By Thomas Blondot, Construction Project Manager, and Carla Vico, Operations Director, Greensolver, France
While every project is different, proactively targeting potential inefficiencies through design adjustments in the early phases of project planning can have a significant impact on the performance of a wind farm over its 15–20 year lifetime – and a direct influence on long-term returns.
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Using Hydrogen and Ammonia Fuels via Underground Pipelines
Humanity's greatest challenge at present is converting the world's largest industry from around 85% fossil to 100% renewable energy (RE) sources as quickly as we prudently and profitably can. Nothing less will allow us to escape the likely synergistic consequences of large-scale fossil fuel combustion, including rapid climate change and global warming, accelerating sea-level rise, ocean acidification, species extinctions and violent human conflicts. Although large amounts of RE could be produced, existing electricity grids are not capable of transmitting this energy to where it is needed. The author argues that rather than just extending electricity grids it would be worth looking at alternatives (such as hydrogen and ammonia carried via underground pipelines) for storage and transmission of RE.
By Bill Leighty, The Leighty Foundation, Juneau, Alaska, USA
Jacobson and Delucchi have demonstrated that we can run the world on wind, water and solar (WWS) energy [ref. 1]. The wind energy of the 12 Great Plains states, if fully harvested on about 50% of these states’ aggregate land area, transmitted to distant markets, and guaranteed to be available (‘firmed’) at an annual scale with storage, could supply the entire annual energy demand of the USA (about 10,000 terawatt-hours, TWh). However, the existing Great Plains electric transmission export capacity is insignificant relative to this resource. Any large, new electric transmission systems, or fractions thereof dedicated to wind energy, will:
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Supporting Wind Turbines Cost-effectively at Hub Heights of over 80 Metres
Wind energy production at the utility scale has commonly been limited to an 80-metre tall hub height in the USA and elsewhere. Strangely enough, this limitation comes from transportation constraints and how the 80-metre-tall steel tubular towers are manufactured and transported. If transportation always controlled how tall we build our infrastructures, urban cities around the world would look completely different today. Transportation capabilities by no means should constraint the evolution of structures; otherwise, the kilometre-plus-high Kingdom Tower under construction in Jeddah, Saudi Arabia, could only be a dream. It is no surprise that studies have shown that as wind turbine towers get taller, a concrete solution may become more cost-effective than the steel tubular option. So, why are we not routinely building concrete towers to reach taller hub heights? How do we get there?
By Sri Sritharan, Wilson Engineering Professor, Department of Civil, Construction and Environmental Engineering, Iowa State University, USA
The Hexcrete concept offers a concrete tower solution with an intention of reaching newer hub heights cost-effectively. The concept eliminates transportation challenges and associated costs by using prefabricated columns and panels. Concretes with compressive strengths higher than that of normal concrete combined with prestressing offer competitive dimensions for tapered Hexcrete towers.
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Challenges and Solutions for Wind Turbines
Rotor blades in wind turbines are growing longer – but also slower. Multi-megawatt wind turbines will turn even more slowly, so reproducible low-frequency vibration monitoring will gain in importance not only for the main rotor but also for the slow-operating gearbox components and roller bearings. Reliably measuring low frequencies, however, can be rather tricky. This article discusses some of the issues that pose new challenges to sensor and measurement hardware manufacturers and some possible solutions.
By Dr Edwin Becker, Pruftechnik Condition Monitoring GmbH, Germany
What Are Low-Frequency Vibrations?
According to VDI 3834 and ISO 10816-21, low-frequency vibrations are defined as vibrations between 0.1 and 10Hz. These vibrations are analysed for their velocities and acceleration rates, and the least favourable values count.
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How a New Class of Wind Turbine was Developed
What do you do when you want a wind turbine, but it is not possible because of local planning regulations? Most people would just give up and look elsewhere for their renewable energy, but not Win Keech. Win lives in the North York Moors National Park, a beautiful part of northern England, with extremely rigorous planning requirements, so much so that in the 1,500 km2 park (which is in one of the windiest parts of the UK) there is only one wind turbine installed. To Win, the solution was obvious, he decided to invent his own wind turbine that would be acceptable to the planners.
By Dean Gregory, Co-founder, The Power Collective Ltd, UK
The brief was simple – the turbine had to be as unobtrusive as possible, efficient at all wind speeds, work well in the urban environment, and be silent, vibration free and inexpensive.
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A Study of Torsional Reversals Caused Through Wind Events and Operating Conditions
Although wind turbines have been around for decades, recent research has been focused on what occurs with a wind turbine under various wind conditions. It is understood anecdotally that high gusts and turbulent winds can add to the chance of breakdown of wind turbine equipment and lead to an increase in O&M and capital costs. Ridgeline and downwind turbines see higher O&M costs. Most of the earlier focus was on the effects on blades and tower structures. New data shows how the entire drive-train sees an impact from these transient events. Drive-train torque monitoring on various turbine models has shown that an asymmetrical torque control device reduces the damaging loads and helps extend turbine life.
By Doug Herr, General Manager, AeroTorque Corp., USA
Types of Transient Wind Conditions Faced by Wind Turbines
Wind turbines see a broader range of dynamic loads than other rotating equipment. They experience variation from the grid/generator (in the form of curtailments, grid loss, voltage changes etc) and also see very frequent wind changes. Storms, gusting conditions and even a sudden wind loss can cause significant variability in drive-train loads. These common events all contribute to the reduction in the expected life of drive-train components.
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Root Cause Hypotheses and How to Prevent Failures
The failure of bearings due to the development of white-etching cracks (WEC) in the inner ring of the bearing has become a leading cause of wind turbine gearbox unreliability. The failures are not confined to any single gearbox or bearing manufacturer, but are systemic throughout the industry. The root cause of the failures is not known, although many theories have been proposed and are currently under investigation. Even though the cause of failures is not well understood, risk factors that make a bearing more prone to experience WEC failures are known, as are factors that make a bearing less prone to these failures. By following some simple best practice guidelines in the selection of bearings, WEC bearing failures can be minimised or prevented altogether.
By Rob Budny, President, RBB Engineering, USA
Background on WEC Failure Mode
WEC failures are a relatively recent phenomenon, and can occur at stress levels much lower than those required to cause ‘classical’ rolling contact fatigue. WEC failures were first observed in the automotive industry in the 1990s. The failures occurred in alternator bearings, and the failure rates and consequences of failure were both much lower than what is seen in wind turbine gearboxes today. The components of a cylindrical roller bearing are shown and labelled in Figure 1. The WEC failure mode occurs most often in the inner ring of a bearing. The reasons for this are twofold:
