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With the development of wind power energy, the steel-concrete hybrid tower has been gradually popularized as the onshore tall wind turbine tower. To avoid the resonant response that brings violent damage to the wind turbine tower, the fundamental frequency of the hybrid tower must be carefully analyzed. This study develops a closed-form solution of the fundamental frequency of the hybrid tower, where the abrupt changes of cross-section and material properties, the effect of prestressing, and the mass and rotary inertia of the wind turbine are taken into account. It provides an effective way to obtain the fundamental frequency in the preliminary design of the hybrid tower. The effectiveness of the proposed solution is validated by comparing it with the results of finite element analysis, showing good agreement. By using the proposed solution, a parametric analysis is conducted to investigate the variation rules of the fundamental frequency to the design parameters. It indicates that with the variation of the proportion of the concrete/steel segments, the correlations between the fundamental frequency and the design parameters also change significantly. The parametric analysis conducted herein may provide instructive guidelines to adjust the parameters in the preliminary design of the hybrid tower. [ABSTRACT FROM AUTHOR]

The development of new adhesives has allowed to expand the application of bonding into the most diverse industrial fields. This review article presents the commonly used experimental methods for the investigation of mechanical performance of adhesively bonded joints in the aerospace, wind energy, automotive and civil engineering sectors. In these sectors, due to their excellent intrinsic properties, composite materials are often used along with conventional materials such as steel, concrete and aluminium. In this context, and due to the limitations that the traditional joining techniques present, adhesive joints are an excellent alternative. However, standardized experimental procedures are not always applicable for testing representative adhesive joints in these industries. Lack of relevant regulations across the different fields is often overcome by the academia and companies' own regulations and standards. Additional costs are thus mitigated to the industrial sectors in relation with the certification process which effectively can deprive even the biggest companies from promoting adhesive bonding. To ensure continuous growth of the adhesive bonding field the new international standards, focusing on actual adhesive joints' performance rather than on specific application of adhesive joints are necessary. [ABSTRACT FROM AUTHOR]

The paper reviews the evolution of computational wind engineering from environmental and structural perspectives, since the inaugural conference of computational wind engineering held in Tokyo 30 years ago (CWE 92). The progress in computational methodologies and important aspects for accurate analysis are discussed. As a groundwork for the application of computational fluid dynamics (CFD) to various environmental issues, the importance of accurate modeling of atmospheric boundary layer, urban boundary layer, and urban canopy layer is pronounced. Environmental applications refer to urban micro-climate, pedestrian level wind, near-field pollutant dispersion, natural and urban ventilation, urban wind energy and snow/sand erosion and accumulation. Structural applications refer to wind loading on low- and high-rise buildings, including wind directionality. The most seminal contributions are examined, and their results are presented. It becomes clear that the engineering community has gained more benefits from environmental than structural computational wind engineering applications, mainly due to the usually less demanding computational needs for the former. Future challenges in CFD applications are thoroughly discussed and the need to bridge the gap between environmental and structural applications is highlighted. • Computational wind engineering progress since the seminal conference of CWE 1992, in environmental and structural applications. • Turbulence models, verification, validation, and best practice guidelines in computational wind engineering. • Progress is environmental research field of pedestrian level wind, near-field pollutant dispersion, natural ventilation, urban ventilation, urban wind energy, snow/sand erosion and accumulation. • Progress in structural research field for design of low- and high-rise buildings. • Future perspective of CFD application to environmental and structural problems. [ABSTRACT FROM AUTHOR]

Present paper shows a new procedure to obtain control algorithms based on weather conditions to fault forecast in a real wind farm during a year. In an initial study, results showed a correlation between central hydraulic level and gearbox level and asymmetric currents and the emergency stop. A second statistical study of one-way analysis of variance was selected to define groups of errors under the same weather conditions. In consequence, a clear relationship between groups of maintenance problems and weather conditions under which they happens was obtained. It was obtained that the more important weather variables for maintenance were the mean outdoor temperature and the wind velocity. Mean outdoor temperature was related with freezing of anemometers and excessive orienting time faults. On the other hand, brake shoe temperature, emergency stop, low voltage and asymmetric currents were related with wind velocity and wind direction faults. Finally, relative humidity resulted as the worst weather parameter to predict maintenance problems. Furthermore, the average values of each weather condition at which faults are expected were defined due to these values can be employed in future research works about fault forecast based on local weather forecast. [ABSTRACT FROM AUTHOR]

Large numbers of bats are killed by wind turbines worldwide and minimizing fatalities is critically important to bat conservation and acceptance of wind energy development. We implemented a 2-year study testing the effectiveness of an ultrasonic acoustic deterrent for reducing bat fatalities at a wind energy facility in Pennsylvania. We randomly selected control and treatment turbines that were searched daily in summer and fall 2009 and 2010. Estimates of fatality, corrected for field biases, were compared between treatment and control turbines. In 2009, we estimated 21–51% fewer bats were killed per treatment turbine than per control turbine. In 2010, we determined an approximate 9% inherent difference between treatment and control turbines and when factored into our analysis, variation increased and between 2% more and 64% fewer bats were killed per treatment turbine relative to control turbines. We estimated twice as many hoary bats were killed per control turbine than treatment turbine, and nearly twice as many silver-haired bats in 2009. In 2010, although we estimated nearly twice as many hoary bats and nearly 4 times as many silver-haired bats killed per control turbine than at treatment turbines during the treatment period, these only represented an approximate 20% increase in fatality relative to the pre-treatment period for these species when accounting for inherent differences between turbine sets. Our findings suggest broadband ultrasound broadcasts may reduce bat fatalities by discouraging bats from approaching sound sources. However, effectiveness of ultrasonic deterrents is limited by distance and area ultrasound can be broadcast, in part due to rapid attenuation in humid conditions. We caution that an operational deterrent device is not yet available and further modifications and experimentation are needed. Future efforts must also evaluate cost-effectiveness of deterrents in relation to curtailment strategies to allow a cost-benefit analysis for mitigating bat fatalities. [ABSTRACT FROM AUTHOR]

Abstract: The present concept of solar chimney is a tall vertical chimney constructed at the center of a large area, which is the collector. This creates questions about stability and economic viability of the chimney and also demands elaborate engineering techniques for constructing a tall chimney. We suggest geometry of “Inclined Solar Chimney” (ISC), which is constructed along the face of a high rising mountain, on which maximum solar insolation is incident throughout the year. The chimney and the collector get merged here. This makes the structure stable, cost effective and easy for construction. A mathematical model has been developed considering the total energy balance. It predicts the temperature and velocity and kinetic power of the emerging air draft for some chosen values of other parameters. The model also shows the proportion in which absorbed solar energy is divided into different forms, and hence predicts the dependence of kinetic of emerging air draft upon dimensions of the chimney and properties of materials used. Further, it is shown that external winds enhance the kinetic power of the emerging air. Thus ISC can also harness the wind energy, available at the top of the mountain. [Copyright &y& Elsevier]

Abstract: Since many years, engineering, research and development of hybrid systems for rural electrification are strongly supported by computer simulations. Different software packages have been used according to the required level of details along with the progress of the project HYRESS. For the development of optimal system control and load/energy management strategy, different simulation models from APL (Alternative Power Library) have been used for a Hybrid PV–wind-hydrogen system that will be installed in the Essaouira region in Morocco. This library provides models developed by IWES for the simulation of regenerative power supply systems and it is used to investigate the integration of a hydrogen storage path in hybrid system operation. [Copyright &y& Elsevier]

Wind-diesel systems represent a proactive step towards sustainable remote communities. However, for high ratios of wind energy, the necessity of a dump load and the diesel operating constraints need to be considered. Energy storage systems offer a means of optimizing energy use and further reducing consumption of diesel fuel. This paper proposes a methodology for storage sizing based on stochastic optimization. The problem is formulated and solved using representative data. The dependence of storage sizing and the cost of delivered energy on wind penetration levels, storage efficiency, and diesel operating strategies are considered. Results demonstrate that for high wind penetration, the availability of storage, together with an appropriate diesel operating approach, can result in significant cost savings in terms of fuel and operating costs. [ABSTRACT FROM AUTHOR]

Spinning reserve (SR) allows system operators to compensate for unpredictable imbalances between load and generation caused by sudden outages of generating units, errors in load forecasting or unexpected deviations by generating units from their production schedules. As the proportion of power produced by wind farms increases, it becomes more difficult to predict accurately the total amount of power injected by all generators into the power system. This added uncertainty must be taken into account when setting the requirement for SR. This paper proposes a technique to calculate the optimal amount of SR that the system operator should provide to be able to respond not only to generation outages but also to errors in the forecasts for load and wind power production. Using a Monte Carlo simulation, the proposed technique for setting the SR requirements is then compared with the traditional deterministic criterion (i.e., the capacity of the largest online infeed), an approach to cope with wind imbalances and an approach that combines the traditional criterion with the approach to cope with wind imbalances. The results show that, contrary to what is commonly believed, an increased wind power penetration does not necessarily require larger amounts of SR. [ABSTRACT FROM AUTHOR]

This paper presents a new method to enhance the participation of variable-speed wind energy conversion systems (WECS) in existing frequency regulation mechanisms. The proposed approach, based on a modified inertial control scheme, takes advantage of the fast response capability associated with electronically-controlled WECS, allowing the kinetic energy stored by rotational masses to be partly and transiently released in order to provide earlier frequency support. An additional improvement is achieved by communicating the WECS response to conventional generators so that these can eventually take care of the full load imbalance. Several simulations using a two-area test system are performed to demonstrate the benefits of the proposed scheme. [ABSTRACT FROM AUTHOR]

In the last decade, distributed generation, with its various technologies, has increased its presence in the energy mix presenting distribution networks with challenges in terms of evaluating the technical impacts that require a wide range of network operational effects to be qualified and quantified. The inherent time-varying behavior of demand and distributed generation (particularly when renewable sources are used), need to be taken into account since considering critical scenarios of loading and generation may mask the impacts. One means of dealing with such complexity is through the use of indices that indicate the benefit or otherwise of connections at a given location and for a given horizon. This paper presents a multiobjective performance index for distribution networks with time-varying distributed generation which consider a number of technical issues. The approach has been applied to a medium voltage distribution network considering hourly demand and wind speeds. Results show that this proposal has a better response to the natural behavior of loads and generation than solely considering a single operation scenario. [ABSTRACT FROM AUTHOR]

This paper studies the behavior of a high-voltage direct current link based on voltage-source converters, which feeds a weak ac network with power produced from an offshore wind farm (WF) of induction generators. Its control system, which is based on adaptive fuzzy controllers, manages to offer very satisfactory performance, without the need for a detailed mathematical model, but just prior knowledge of the behavior of the electrical system. Using the simulation program PSCADIEMTDC, the study was performed under both steady-state and transient conditions. The results show that the link supplies the variable power of the WF to a weak grid, keeping the ac voltage fluctuations in the point of common coupling at an acceptable level. Moreover, due to the ability of the control system to adjust the stator frequency of the induction generators in relation to the wind velocity, maximum wind power acquisition is achieved. [ABSTRACT FROM AUTHOR]

This paper introduces a small-signal dynamic model of a fixed-frequency (induction machine based) wind farm connected to an electrical power system. The model represents the system small-signal dynamics in the frequency range of a fraction of Hz to 50/60 Hz. The model includes the dynamics of the wind energy capturing mechanism, the rotating shaft system, the generator electrical system of each wind energy unit, the wind farm collector system, and the utility grid. Based on the proposed model, two performance indices are introduced to i) investigate sensitivity of the system modes, e.g., torsional modes, to the system parameters, and ii) evaluate the system capability to reject electrical and mechanical disturbances, e.g., a wind gust. The application of the model to the analysis of a system with two wind units is presented and the study results are validated based on comparison with the time-domain simulation results obtained in the PSCAD/EMTDC environment. [ABSTRACT FROM AUTHOR]

Since the pioneering studies developed by Alan G. Davenport, the equivalent static actions on structures are a key topic of the wind engineering research. Two main methods have been proposed. The former, referred to as the gust factor (GF) technique, defines wind actions through a unique load distribution scaled by a non-dimensional coefficient eventually depending on the effect considered. The latter, referred to as the load combination (LC) technique, defines wind actions, till now in the alongwind direction, as a combination of three distinct load distributions associated with the static, quasi-static and resonant parts of the response. This paper provides a rational scheme and a generalisation of these procedures with reference to cantilever vertical structures. As for the GF technique, also the LC technique is initially extended to the 3-D response, discussing critically a set of alternative models for the quasi-static part of the loading. A new method is also proposed, referred to as the global loading technique, where equivalent static wind actions are assigned as a unique load distribution independent of the load effect considered. All problems dealt with in this paper are solved in closed form. [Copyright &y& Elsevier]

• A typical CoS x -Ni 3 S 2 nanosheet array was constructed by a one-step hydrothermal method. • The nanoarray structures render the electrode with superhydrophilicity and superaerophobicity. • The CoS x -Ni 3 S 2 electrode only need a voltage of 1.63 V to afford 100 mA cm−2 for full water splitting. • Solar and wind energy for water splitting using CoS x -Ni 3 S 2 as electrocatalyst was simulated. Besides the development of effective catalysts, surface property of the electrode is also crucial in electrocatalytic hydrogen evolution. Herein, a nanosheet array electrode of CoS x -Ni 3 S 2 /NF was designed by a facile hydrothermal process. Particularly, the obtained electrode was endowed with superhydrophilicity and superaerophobicity, which not only facilitates to the exposure of active sites, but also alleviates the "bubble shielding effect" for gas diffusion. Consequently, the nanosheet array electrode demonstrated excellent full water splitting activities in alkaline condition, which only need a low voltage of 1.63 V to achieve a current density of 100 mA cm–2 and can keep a long durability for 20 h at 20 mA cm−2. Additionally, the production of hydrogen powered by the electricity derived from solar and wind energy utilizing the CoS x -Ni 3 S 2 /NF as the electrocatalysts in laboratory condition was also simulated. This work will provide a novel perspective for HER research from the engineering of electrode-architecture. [ABSTRACT FROM AUTHOR]

This article discusses a pinwheel lesson that was created from a unit on the advantages and disadvantages of wind energy. Students in this activity experienced each step of the engineering and design of a pinwheel. The purpose of the pinwheel machine is to give students the opportunity to take their scientific knowledge and use it to solve a problem that mimics problems encountered by real engineers. Design challenges of this sort are essential for preparing students to tackle real-life problems. The step by step process of this procedure is explained in the article.