Bird detection and species classification with time‐lapse images around a wind farm: Dataset construction and evaluation

Collisions of birds, especially endangered species, with wind turbines is a major environmental concern. Automatic bird monitoring can be of aid in resolving the issue, particularly in environmental risk assessments and real‐time collision avoidance. For automatic recognition of birds in images, a clean, detailed, and realistic dataset to learn features and classifiers is crucial for any machine‐learning‐based method. Here, we constructed a bird image dataset that is derived from the actual environment of a wind farm and that is useful for examining realistic challenges in bird recognition in practice. It consists of high‐resolution images covering a wide monitoring area around a turbine. The birds captured in these images are at relatively low resolution and are hierarchically labeled by experts for fine‐grained species classification. We conducted evaluations of state‐of‐the‐art image recognition methods by using this dataset. The evaluations revealed that a deep‐learning‐based method and a simpler traditional learning method were almost equally successful at detection, while the former captures more generalized features. The most promising results were provided by the deep‐learning‐based method in classification. The best methods in our experiments recorded a 0.98 true positive rate for bird detection at a false positive rate of 0.05 and a 0.85 true positive rate for species classification at a false positive rate of 0.1.     

Energy crop cultivations of reed canary grass — An inferior breeding habitat for the skylark,a characteristic farmland bird species

Here, I present the first comparison of the abundance of farmland birds in energy grass fields and in cereal-dominated conventionally cultivated fields (CCFs). I demonstrate that in boreal farmland, skylark (Alauda arvensis) densities were significantly lower in reed canary grass (RCG) (Phalaris arundinacea) fields than in CCFs. I found that during the early breeding season RCG fields and CCFs are equally good habitats, but over the ensuing couple of weeks RCG rapidly grows too tall and dense for field-nesting species. Consequently, RCG is an inferior habitat for skylark for laying replacement clutches (after failure of first nesting) or for a second clutch after one successful nesting. The results imply that if RCG cultivation is to be expanded, the establishment of large monocultures should be avoided in farmland landscapes; otherwise the novel habitat may affect detrimentally the seriously depleted skylark population, and probably also other field-nesting bird species with similar breeding habitats.     

Ground flora,small mammal and bird species diversity in miscanthus (Miscanthus×giganteus) and reed canary-grass (Phalaris arundinacea) fields

Wildlife monitoring of two miscanthus and two reed canary-grass fields in Herefordshire, England was carried out in 2002, 2003 and 2004 to investigate the ecological impact of perennial biomass grass crops on ground flora, small mammals and birds. Quadrats were used to record percentage ground vegetation cover within and around the periphery of each crop. Small mammals were sampled by live trapping using Longworth traps. The common bird census technique was used to monitor populations of birds. Miscanthus fields were richer in weed vegetation than reed canary-grass or arable fields. Bird use of the biomass crop fields varied depending on species. There were considerably more open-ground bird species such as skylarks (Alauda arvensis), lapwings (Vanellus vanellus) and meadow pipits (Anthus pratensis) within miscanthus than within reed canary-grass fields. There was no particular crop-type preference by the small mammal species, but rather a preference for good ground cover and little land disturbance, which was provided by both biomass crops. Ground flora, small mammals and most of the bird species (except open-ground birds) were found more abundantly within field margins and boundaries than in crop fields indicating the importance of retaining field structure when planting biomass crops. The miscanthus work relates entirely to young crops, which may be representative of part of the national crop if large areas are cultivated for rhizomes. The findings from the current project indicate that perennial biomass grass crops can provide substantially improved habitat for many forms of native wildlife, due to the low intensity of the agricultural management system and the untreated headlands.     

The impact of growing miscanthus for biomass on farmland bird populations

Miscanthus is a newly introduced crop grown primarily to produce biomass for energy production and the area grown in the UK is anticipated to increase. Major differences in crop management from conventional arable crops have led to speculation that miscanthus may also have effects on farmland biodiversity. Six miscanthus fields were paired with six of a conventional crop, winter wheat, and bird diversity and abundance were compared in winter and during the breeding season along with potential food sources. Miscanthus fields had a greater abundance and diversity of birds than did wheat in winter and summer. In winter, the greater numbers of birds in miscanthus fields were probably attracted by the shelter provided by the crop and by the abundance of non-crop plants. During the breeding season, the abundance of non-crop plants in miscanthus fields, and greater numbers of insects associated with these plants, provided food resources. However, the miscanthus crop plants provided less insect food than wheat crop plants. Changes in crop structure during the breeding season influenced the breeding birds. The results from this study suggested that an increase in the area of miscanthus grown in the UK may have temporary benefits for farmland bird populations during establishment. These benefits are likely to diminish with age of crop and as crop management improves with experience. Management for wildlife will be required to maintain the diversity of features attractive to birds because many of these will be lost if miscanthus is managed solely to maximise crop yields.     

Numerical modelling of the effect of turbines on currents in a tidal channel – Tory Channel,New Zealand

Numerical modelling is used to assess the effect of a turbine array on tidal currents in the Tory Channel, New Zealand. The Tory Channel is the smaller of two entrances from Cook Strait to the Queen Charlotte Sound with a large island separating the narrow Tory Channel from the main entrance. The 2D depth-averaged finite element model is validated against velocities from shipboard ADCP transects from a survey during spring tide conditions, and water levels recorded at the study site. Turbine drag is introduced to the model as a stress term in the momentum equations, and includes both the turbine thrust and the structural drag. Turbine array drag is a function of the number and size of turbines, which can be parameterised in a non-dimensional number. This non-dimensional turbine drag number D can be used to represent the drag of several different turbine designs. Restrictions are placed on the size of the array to ensure that turbines are placed in realistic locations. In this study, turbines are restricted to areas with water depths greater than 30 m, and where spring tide currents (in the absence of turbines) are greater than 2.0 m s⁻¹, and consequently the turbine array does not span the entire channel width or length. The modelling shows turbines will reduce current speeds both within the turbine array, and also throughout much of the Tory Channel, with local increases in speed immediately adjacent the array. Cut-in and maximum or rated turbine speeds are also incorporated to compare how these factors influence both the power production and effect on currents. The study shows that, due to the restrictions placed on the array location, the likely power production that can be achieved is considerably less than what an analytical prediction suggests might be obtained from the channel. Due to the effects of turbines on current speeds, optimising the area occupied by an array is likely to be an iterative procedure. The power produced per turbine unit could be substantially improved, with little impact on total power produced by the array, by removing turbines from areas where power produced was low. Turbine operational limits, applied in the form of cut-in speeds below which no power is produced, and design speeds above which load shedding occurs, affect both the magnitude and spatial distribution of power production and thus need to be considered in array design.     

Comparing least cost scenarios for 100% renewable electricity with low emission fossil fuel scenarios in the Australian National Electricity Market

Policy makers face difficult choices in planning to decarbonise their electricity industries in the face of significant technology and economic uncertainties. To this end we compare the projected costs in 2030 of one medium-carbon and two low-carbon fossil fuel scenarios for the Australian National Electricity Market (NEM) against the costs of a previously published scenario for 100% renewable electricity in 2030. The three new fossil fuel scenarios, based on the least cost mix of baseload and peak load power stations in 2010, are: (i) a medium-carbon scenario utilising only gas-fired combined cycle gas turbines (CCGTs) and open cycle gas turbines (OCGTs); (ii) coal with carbon capture and storage (CCS) plus peak load OCGT; and (iii) gas-fired CCGT with CCS plus peak load OCGT. We perform sensitivity analyses of the results to future carbon prices, gas prices, and CO₂ transportation and storage costs which appear likely to be high in most of Australia. We find that only under a few, and seemingly unlikely, combinations of costs can any of the fossil fuel scenarios compete economically with 100% renewable electricity in a carbon constrained world. Our findings suggest that policies pursuing very high penetrations of renewable electricity based on commercially available technology offer a cost effective and low risk way to dramatically cut emissions in the electricity sector.     

Hydrokinetic turbine array characteristics for river applications and spatially restricted flows

Multiple hydrokinetic turbines in three array configurations were characterized computationally by employing Reynolds Averaged Navier-Stokes equations. The simulations were conducted for pre-existing turbines operating at their optimum power coefficient of 0.43 which was obtained by design and optimization process. Mechanical power for two adjacent units was predicted for various lateral separation distances. An additional two-by-two turbine array was studied, mimicking a hydro-farm. Numerical simulations were performed using actual physical turbines in the field rather than using low fidelity models such as actuator disk theory. Steady state simulations were conducted using both Coupled and SIMPLE pressure-velocity solvers. Steady three dimensional flow structures were calculated using the k-ω Shear Stress Transport (SST) turbulence model. At a lateral separation distance of 0.5D_t, the turbines produced an average 86% of the peak power a single turbine producing. Interaction effects at lateral separation distances greater than 2.5D_t were negligible. The wake interaction behind the upstream turbines causes a significant performance reduction for downstream turbines within 6D_t longitudinal spacing. Downstream turbines employed for the present study performed around 20% or less of a single unit turbine performance for the same operating conditions. Downstream turbines yielded comparable reductions in power to that of experimental results.     

Local wind-energy potential for the city of Guelph,Ontario (Canada)

Municipalities around the world are using community energy plans (CEPs) to drive progress towards a more sustainable energy future. Many recognize the supply of local and renewable energy as a crucial component of a resilient future including the potential use of wind power generation. The city of Guelph (Ontario, Canada) included wind energy as a component of its CEP. The goal of this work was to estimate the potential for wind power generation within the municipal boundaries of this city. This paper summarizes the methodology used and results obtained with site and meteorological data, wind maps, and turbine power curves. The methodology relies on the use of a geographically uniform array of turbines, spread throughout the community. An array of utility-scale turbines could potentially generate 29% of Guelph’s 2005 total electricity demand, whereas one consisting of small-scale turbines could achieve 10% of that demand.     

Dynamic modelling and control of fully rated converter wind turbines

Today, many countries are integrating large amount of wind energy into the grid and many more are expected to follow. The expected increase of wind energy integration is therefore a concern particularly to transmission grid operators. Based on the past experience, some of the relevant concerns when connecting significant amount of wind energy into the existing grid are: fault ride through requirement to keep wind turbines on the grid during faults and wind turbines have to provide ancillary services like voltage and frequency control with particular regard to island operation.While there are still a number of wind turbines based on fixed speed induction generators (FSIG) currently running, majority of wind turbines that are planned to be erected are of variable speed configurations. The reason for this is that FSIG are not capable of addressing the concern mentioned above. Thus, existing researches in wind turbines are now widely directed into variable speed configurations. This is because apart from optimum energy capture and reduction of mechanical stress, preference of these types is also due to the fact that it can support the network such as its reactive power and frequency regulation. Variable wind turbines are doubly fed induction generator wind turbines and full converters wind turbines which are based on synchronous or induction generators.This paper describes the steady state and dynamic models and control strategies of wind turbine generators. The dynamic models are presented in the dq frame of reference. Different control strategies in the generator side converter and in the grid side converter for fault ride through requirement and active power/frequency and reactive/voltage control are presented for variable speed wind turbines.     

Roof mounting site analysis for micro-wind turbines

Building-integrated micro-wind turbines are promising low-cost renewable energy devices. However, the take-up of micro-wind turbines in high density suburban environments is still very limited due to issues such as: a) low wind speeds; b) high turbulence intensity; and c) the perception of potentially high levels of aerodynamic noise generated by the turbines. The wind flow field above the roof of buildings in this environment is different to that over flat terrain or around isolated buildings. The effect of the local suburban topology on the wind speed and turbulence intensity fields in a given locality is therefore an important determinant of the optimal location of micro-wind turbines. This paper presents a numerical study of above roof wind flow characteristics in three suburban landscapes characterized by houses with different roof profiles, namely: pitched roofs, pyramidal roofs and flat roofs. Computational Fluid Dynamic (CFD) technique has been used to simulate the wind flow in such environments and to find the optimum turbine mounting locations. Results show how the wind flow characteristics are strongly dependent on the profile of the roofs. It is found that turbines mounted on flat roofs are likely to yield higher and more consistent power for the same turbine hub elevation than the other roof profiles.     

Three routes forward for biofuels: Incremental,leapfrog, and transitional

This paper examines three technology routes for lowering the carbon intensity of biofuels: (1) a leapfrog route that focuses on major technological breakthroughs in lignocellulosic pathways at new, stand-alone biorefineries; (2) an incremental route in which improvements are made to existing U.S. corn ethanol and soybean biodiesel biorefineries; and (3) a transitional route in which biotechnology firms gain experience growing, handling, or chemically converting lignocellulosic biomass in a lower-risk fashion than leapfrog biorefineries by leveraging existing capital stock. We find the incremental route is likely to involve the largest production volumes and greenhouse gas benefits until at least the mid-2020s, but transitional and leapfrog biofuels together have far greater long-term potential. We estimate that the Renewable Fuel Standard, California's Low Carbon Fuel Standard, and federal tax credits provided an incentive of roughly $1.5–2.5 per gallon of leapfrog biofuel between 2012 and 2015, but that regulatory elements in these policies mostly incentivize lower-risk incremental investments. Adjustments in policy may be necessary to bring a greater focus on transitional technologies that provide targeted learning and cost reduction opportunities for leapfrog biofuels.     

Multi-objective,multi-period optimization of biomass conversion technologies using evolutionary algorithms and mixed integer linear programming (MILP)

The design and operation of energy systems are key issues for matching energy supply and demand. A systematic procedure, including process design and energy integration techniques for sizing and operation optimization of poly-generation technologies is presented in this paper. The integration of biomass resources as well as a simultaneous multi-objective and multi-period optimization, are the novelty of this work. Considering all these concepts in an optimization model makes it difficult to solve. The decomposition approach is used to deal with this complexity.Several options for integrating biomass in the energy system, namely back pressure steam turbines, biomass rankine cycles (BRC), biomass integrated gasification gas engines (BIGGE), biomass integrated gasification gas turbines, production of synthetic natural gas (SNG) and biomass integrated gasification combined cycles (BIGCC), are considered in this paper. The goal is to simultaneously minimize costs and CO₂ emission using multi-objective evolutionary algorithms (EMOO) and Mixed Integer Linear Programming (MILP).Finally the proposed model is demonstrated by means of a case study. The results show that the simultaneous production of electricity and heat with biomass and natural gas are reliable upon the established assumptions. Furthermore, higher primary energy savings and CO₂ emission reduction, 40%, are obtained through the gradual increase of renewable energy sources as opposed to natural gas usage. However, higher economic profitability, 52%, is achieved with natural gas-based technologies.     

Vanadium redox flow batteries for the storage of electricity produced in wind turbines

In this work, accelerated degradation charge‐discharge tests have been applied to compare the performance of a bench‐scale vanadium redox flow battery (VRFB), when charged under galvanostatic conditions and under the highly variable conditions of current produced by wind turbines. Wind speed patterns applied for the VRFB charge were obtained during 3 representative days in winter, in Ciudad Real (Spain). The accumulated and delivered charge capacities and the different efficiencies (coulombic, voltage, and energy) were analyzed during 3 charge and discharge cycles. The conversion of the different vanadium species during the charge‐discharge cycles indicated that the operation mode had a strong influence on the performance of the VRFB and helped to explain the charge profiles obtained. Although, similar efficiencies and charge/discharge capacities were found, the VRFB operated in wind‐charging mode performs slightly worse than the VFRB operated in galvanostatic mode. Increased crossover of vanadium species in the negative electrolyte compartment explains the differences found. Nevertheless, it can be concluded that this type of technology seems to be promising for the storage of electricity produced by wind turbines.     

Tower shadow induced blade loads for an extreme‐scale downwind turbine

The downwind rotor configuration provides a structural advantage compared with an upwind design. However, tower shadow has long been a concern for downwind systems. The tower shadow negatively affects the blade by introducing a load impulse during the wake passage. An aerodynamic fairing could shroud the tower reducing the wake. However, there is no clear consensus on the importance of a tower shadow for utility‐scale wind turbines. Simulations were conducted in FAST to determine the general parameters that influence the importance of the tower shadow effect for the differently sized wind turbines. The lock number of the blade was a significant driving quantity. Lower lock numbers (typical of small‐scale wind turbines) lead to greater relative fatigue damage from tower shadow effects. It was determined that a fairing is very helpful for small‐scale wind turbines operating in a low‐turbulence environment (such as a subscale wind tunnel test). However, the tower shadow increased the damage equivalent loading on an extreme scale blade by less than 5% in a turbulent environment. These results indicate that the cost of a tower fairing is likely unnecessary for utility‐scale wind turbines in operation.     

Likelihood of a marine vessel accident from wind energy development in the Atlantic

Offshore wind energy development is planned for areas off the Atlantic coast. Many of the planned wind development areas fall within traditional commercial vessel routes. In order to mitigate possible hazards to ships and to wind turbines, it is important to understand the potential for increased risk to commercial shipping from the presence of wind farms. Risk is identified as the likelihood that an occurrence will happen, and the consequences of that occurrence, should it occur. This paper deals with the likelihood of commercial vessel accidents, because of the development of offshore wind energy along the US Atlantic coast. Using Automatic Identification System (AIS) data, historical shipping routes between ports in the Atlantic were identified, from Maine to the Florida Straits. The AIS data were also used as inputs to a numerical model that can simulate cargo, tanker and tug/towing vessel movement along typical routes. The model was used to recreate present day vessel movement, as well as to simulate future routing that may be required to avoid wind farms. By comparing the present and future routing of vessels, an analysis of potential maritime accidents was used to determine the increased marginal risk of vessel collisions, groundings and allisions with stationary objects, because of the presence of wind farms. The outcome of the analysis showed little increase in vessel collisions or allisions, and a decrease in groundings as more vessels were forced seaward by the wind farms. Copyright © 2015 John Wiley & Sons, Ltd.     

Review of design conditions applicable to offshore wind energy systems in the United States

Offshore wind turbines are now being considered for use in the United States. Ensuring proper design of offshore wind turbines and wind farms requires knowledge of the external conditions in which the turbines and associated facilities are to operate. The primary external conditions are due to the wind and waves. Also, for many locations, floating ice will also be a major factor in the design. This review examines the following aspects of external conditions for the design of offshore wind turbines for the United States: (1) design requirements, (2) available offshore data sources, (3) data estimation and extrapolation techniques, (4) on-site data collection, and (5) likely sources of extreme events, including hurricanes and northeast storms.     

Fundamentals applicable to the utilisation of marine current turbines for energy production

The potential of electric power generation from marine tidal currents is enormous. Tidal currents are being recognised as a resource to be exploited for the sustainable generation of electrical power. The high load factors resulting from the fluid properties and the predictable resource characteristics make marine currents particularly attractive for power generation and advantageous when compared to other renewables. There is a paucity of information regarding various key aspects of system design encountered in this new area of research. Virtually no work has been done to determine the characteristics of turbines running in water for kinetic energy conversion even though relevant work has been carried out on ship’s propellers, wind turbines and on hydro turbines. None of these three well established areas of technology completely overlap with this new field so that gaps remain in the state of knowledge. This paper reviews the fundamental issues that are likely to play a major role in implementation of MCT systems. It also highlights research areas to be encountered in this new area. The paper reports issues such as the harsh marine environment, the phenomenon of cavitation, and the high stresses encountered by such structures are likely to play a major role on the work currently being undertaken in this field.     

Steam cracking and methane to olefins: Energy use,CO2 emissions and production costs

While most olefins (e.g., ethylene and propylene) are currently produced through steam cracking routes, they can also possibly be produced from natural gas (i.e., methane) via methanol and oxidative coupling routes. We reviewed recent data in the literature and then compared the energy use, CO₂ emissions and production costs of methane-based routes with those of steam cracking routes. We found that methane-based routes use more than twice as much process energy than state-of-the-art steam cracking routes do (the energy content of products is excluded). The methane-based routes can be economically attractive in remote, gas-rich regions where natural gas is available at low prices. The development of liquefied natural gas (LNG) may increase the prices of natural gas in these locations. Oxidative coupling routes are currently still immature due to low ethylene yields and other problems. While several possibilities for energy efficiency improvement do exist, none of the natural gas-based routes is likely to become more energy efficient or to lead to less CO₂ emissions than steam cracking routes do.     

Aeroelastic instability problems for wind turbines

This paper deals with the aeroelastic instabilities that have occurred and may still occur for modern commercial wind turbines: stall‐induced vibrations for stall‐turbines, and classical flutter for pitch‐regulated turbines. A review of previous works is combined with derivations of analytical stability limits for typical blade sections that show the fundamental mechanisms of these instabilities. The risk of stall‐induced vibrations is mainly related to blade airfoil characteristics, effective direction of blade vibrations and structural damping; whereas the blade tip speed, torsional blade stiffness and chordwise position of the center of gravity along the blades are the main parameters for flutter. These instability characteristics are exemplified by aeroelastic stability analyses of different wind turbines. The review of each aeroelastic instability ends with a list of current research issues that represent unsolved aeroelastic instability problems for wind turbines. Copyright © 2007 John Wiley & Sons, Ltd.