In order to obtain maximum power output of a Wind Energy Conversion System (WECS), the rotor speed needs to be optimised for a particular wind speed. However, due to inherent inertia, the rotor of a ...WECS cannot react instantaneously according to wind speed variations. As a consequence, the performance of the system and consequently the wind energy conversion capability of the rotor are negatively affected. This study considers the use of a time series Adaptive Linear Prediction (ALP) technique as a means to improve the performance and conversion efficiency of wind turbines. The ALP technique is introduced as a real time control reference to improve optimal control of wind turbines. In this study, a wind turbine emulator is developed to evaluate the performance of the predictive control strategy. In this regard, the ALP reference control method was applied as a means to control the torque/speed of the emulator. The results show that the employment of a predictive technique increases energy yield by almost 5%.
•A representation of the performance of a real wind turbine subjected to variable wind.•Adaptive Linear Prediction to improve performance and conversion efficiencies of WECS.•Wind turbine emulator as a means to evaluate time series linear prediction.•Wind sensor method offers an optimal power mapping technique.
National targets for increased renewable energy are common-place internationally and small/micro-generation may help achieve such goals. Energy yields from such technologies however, are very ...location and site specific. In rural environments, the average wind speed is relatively high and the homogeneous landscape promotes laminar air flow and stable (relatively) wind direction. In urban environments however, the wind resource has lower mean wind speeds and increased levels of atmospheric turbulence due to heterogeneous surface forms. This paper discusses the associated costs per unit of electricity generated by micro wind energy conversion systems from the perspective of both urban and rural locations, with three case studies that consider the potential and financial viability for such systems. The case studies ascertain the cost of energy associated with a standard HAWT (horizontal axis wind turbine), in terms of exemplar rural and urban locations. Sri Lanka, Ireland and the UK, are prioritised as countries that have progressive, conservative and ambitious goals respectively towards the integration of micro-generation. LCOE (Levelized cost of energy) analyses in this regard, offers a contextualised viability assessment that is applicable in decision making relating to economic incentive application or in the determination of suitable feed-in tariff rates.
•Levelized cost of energy analysis of rural/urban wind energy systems is presented.•Progressive, conservative and ambitious wind energy case studies are compared.•Design of Experiments analysis (DOE) considers LCOE parameter intra-dependencies.•Urban wind energy harvesting for each case proved to be a cost preclusive option.
The micro-turbine wind market in cities faces significant challenges due to the complexities associated with the urban terrain but, if a renewable solution to increasing energy demand is to be ...achieved, energy conversion systems where populations are concentrated, that is cities, must be considered. This research evaluates the urban wind resource by employing a physically-based empirical model to link wind observations at a conventional meteorological site to those acquired at urban sites. The approach is based on urban climate research that has examined the effects of varying surface roughness on the wind-field between and above buildings. Here, this is applied to link observations at Dublin Airport, outside the urban area, to those made at an urban and sub-urban site in Dublin where instruments were placed near roof-level and well above roof height. The log model to describe the vertical wind profile is tested against observations made over the course of a year. It is shown to have sufficient accuracy to assess the potential for micro-turbine energy generation in cities and illustrates that the urban wind resource can be evaluated from measurements made at a nearby site, adjusted for the urban site location.
•The article investigates if a viable wind resource, worth exploiting, exists at an accessible height above a city (Dublin, Ireland).•Urban climatology and the simple logarithmic profile, are employed to successfully extrapolate the wind resource at the city Airport into an associated suburban and urban location, to a height between 1.5 and 2 times the respective average building height at both locations.•The analysis shows that in conjunction with urban surface roughness, the urban frictional velocity must also be considered for urban wind resource modelling.•Other models are utilised to investigate the nature of the wind resource below the recognised lower limit of the logarithmic profile, namely the power law and a methodology primarily developed for urban air pollution modelling.•The research is provided a renewable energy context by considering the productivity of a commercially available wind generator. The results show that the wind resource available at roughly twice the average building height at either an urban and suburban location is worth harnessing, but within a very short height reduction, the wind resource depletion renders the consideration economically unviable.
Current knowledge of spiders in agroecosystems (excluding tree crops) reported in European and US literature is discussed comparatively, in an attempt to relate spider community structure to pest ...control potential.
The spider fauna of agroecosystems in the northern-temperate zone of Europe is strongly dominated by small linyphiid spiders that capture tiny insects in their sheet webs, including large numbers of pest aphids. In the US, spider guild structure is more complex, and hunters (especially, Oxyopidae, Salticidae, Clubionidae, Thomisidae, and Lycosidae), that have broader diets (including lepidopteran and heteropteran pests), numerically prevail in many locations. Spider populations increase to high densities (2–600
m
−2) in European field crops, but densities are typically much lower (0.02–14
m
−2) in US annual crops. Agroecosystem spiders, in both Europe and the US, feed rather infrequently, but they contribute to pest control as part of larger assemblages of natural enemies, and there is potential for increasing their density and impact in both continents.
Many of the differences between continents in spider guild structure, density and feeding patterns highlighted in this paper are likely to be attributable to climatic differences. Most of the US data originate from more southern latitudes (i.e., subtropical and Mediterranean climates) with distinctly higher mean annual temperatures compared to the European study areas, which are in the northern-temperate zone. Spider communities may respond to climate directly, and also indirectly via food availability and antagonists. In addition, differences in crop structure and cultural practices (including habitat diversification and the provision of ground cover) could influence spider density and community organisation. Mean farm size is an order of magnitude less in Europe than in the US and this is likely to be associated with greater habitat diversity, which is known to increase spider abundance.
Currently, there is a dearth of field studies from southern Europe (Mediterranean climate) and the northern regions of the US (humid continental climate). The few data available from such regions indicate that the patterns of spider predation may differ less between the two continents if sufficient study areas with similar climatic conditions could be compared. The conclusions in terms of biological control are, however, widely applicable, because a large proportion of the productive agricultural land area of Europe is located in more northern latitudes and the reverse is true in the US.
Wind energy harvesting for electricity generation has a significant role in overcoming the challenges involved with climate change and the energy resource implications involved with population growth ...and political unrest. Indeed, there has been significant growth in wind energy capacity worldwide with turbine capacity growing significantly over the last two decades. This confidence is echoed in the wind power market and global wind energy statistics. However, wind energy capture and utilisation has always been challenging. Appreciation of the wind as a resource makes for difficulties in modelling and the sensitivities of how the wind resource maps to energy production results in an energy harvesting opportunity. An opportunity that is dependent on different system parameters, namely the wind as a resource, technology and system synergies in realizing an optimal wind energy harvest. This paper presents a thorough review of the state of the art concerning the realization of optimal wind energy harvesting and utilisation. The wind energy resource and, more specifically, the influence of wind speed and wind energy resource forecasting are considered in conjunction with technological considerations and how system optimization can realise more effective operational efficiencies. Moreover, non-technological issues affecting wind energy harvesting are also considered. These include standards and regulatory implications with higher levels of grid integration and higher system non-synchronous penetration (SNSP). The review concludes that hybrid forecasting techniques enable a more accurate and predictable resource appreciation and that a hybrid power system that employs a multi-objective optimization approach is most suitable in achieving an optimal configuration for maximum energy harvesting.
Recently, a prognostic index including six risk factors (RFs) (unfavourable Eastern Cooperative Oncology Group performance status ECOG PS, presence of liver metastases, short response to luteinizing ...hormone-releasing hormone LHRH agonists/antagonists, low albumin, increased alkaline phosphatase ALP and lactate dehydrogenase LDH) was developed from the COU-AA-301 trial in post-chemotherapy metastatic castration-resistant prostate cancer (mCRPC) patients treated with abiraterone acetate. Our primary objective was to evaluate this model in a cohort of chemotherapy-naive mCRPC patients receiving abiraterone.
We identified 197 chemotherapy-naive patients who received abiraterone at six BC Cancer Agency centres and who had complete information on all six RFs. Study endpoints were prostate-specific antigen (PSA) response rate (RR), time to PSA progression, time on treatment, and overall survival (OS). PSA RR and survival outcomes were compared using Χ
test and log-rank test. Multivariable Cox proportional hazard analysis was performed to identify RFs independently associated with OS.
Patients were classified into good (0-1 RFs), intermediate (2-3 RFs), and poor (4-6 RFs) prognostic groups (33%, 52%, and 15%, respectively). For good-, intermediate-, and poor-risk patients, PSA RR (≥50% decline) was 60% vs. 42% vs. 40% (p=0.05); median time to PSA progression was 7.3 vs. 5.3 vs. 5.0 months (p=0.02); and median OS was 29.4 vs. 13.8 vs. 8.7 months (p<0.0001).
The six-factor prognostic index model stratifies clinical outcomes in chemotherapy-naive mCRPC patients treated with abiraterone. Identifying patients at risk of poor outcome is important for informing clinical practice and clinical trial design.
Natural enemies that control pests usually allow farmers to avoid, or reduce, the use of pesticides. However, modern farming practices, that maximize yields, are resulting in loss of biodiversity, ...particularly prey diversity. Does this matter? Pests continue to thrive, and without alternative prey the predators should, perforce, concentrate their attentions upon the pests.
We showed that a diverse diet significantly enhances predator fecundity and survival. Experiments were conducted using common generalist predators found in arable fields in Europe, the carabid beetle Pterostichus melanarius (Coleoptera: Carabidae) and the linyphiid spider Erigone atra (Araneae: Linyphiidae). We tested the hypothesis that mixed species diets were optimal, compared with restricted diets, with respect to parameters such as predator weights, egg weights, numbers of eggs laid, egg development times, egg hatching rates and predator survival. In carabids, an exclusive earthworm diet was as good as mixed diets containing earthworms for egg production and hatching, but less good than such mixed diets for increase in beetle mass and sustained egg laying. For spiders, aphids alone (Sitobion avenae) or with the Collembola Folsomia candida, drastically reduced survival. Aphids plus the Collembola Isotoma anglicana improved survival but only aphids with a mixed Collembola diet maximized numbers of hatching eggs.
Predators offered only pests (slugs or aphids) had lowest growth rates and fecundity. We therefore demonstrated that conservation of a diversity of prey species within farmland, allowing predators to exploit a diverse diet, is essential if predators are to continue to thrive in crops and regulate agricultural pests.
The effect of relative humidity on egg hatch success for Iphiseius degenerans, Neoseiulus californicus and N. cucumeris was described by a binomial model with a parallel slope. The shape of the ...response differed for Phytoseiulus persimilis and a model with separate parameters gave a significantly better fit. Fitted response curves showed that I. degenerans, N. cucumeris, N. californicus and P. persimilis were ranked by decreasing tolerance to low humidity, with egg mortalities of < 0.5, 3, 12 and 16% respectively at 75-80% RH at 20 degrees C. Egg stage duration for I. degenerans and N. cucumeris was unaffected over the range 60-82% RH. For N. californicus and P. persimilis egg duration was significantly longer at 60 and 70% than for either 82 or 90% RH. No effect of relative humidity was found on the mean life span of adult females when food was available continuously to the mites. N. californicus lived significantly longer (58 days after the first egg was laid) than the other species. No significant difference was observed in mean life span between adult females of I. degenerans and N. cucumeris (25 and 28 days respectively). The mean life span of adult female P. persimilis (19 days) was significantly shorter than the other species. In the absence of both food and water, the survival of adult female mites was reduced to 2-4 days. Survival time was at least doubled when free water was available in the absence of food. Mean survival of adult female mites with water but without food was 10 days for N. cucumeris, 18 days for N. californicus, 6 days for P. persimilis and 4 days for I. degenerans. Survival of adult female N. cucumeris and N. californicus was increased significantly, to 20 and 22 days respectively, when fungal hyphae were present along with water but in the absence of other food.
The interplay between dietary specialism, the tolerance of food and water stress and level of cannibalism is likely to be important in determining the outcome of biological control using inundative ...releases of multiple natural enemies, such as phytoseiid mites in protected crops. The dietary specialist, Phytoseiulus persimilis, with a short immature development time (4-5 days) when plentiful food was available had a low ability to survive without food (5 days), even with access to water. The dietary generalists, Neoseiulus californicus, N. cucumeris and lphiseius degenerans, had longer immature development times (by up to 2 days) than P. persimilis. Survival ability differed amongst the generalist species when they were starved but provided with constant access to water. Both N. californicus and N. cucumeris survived the longest (8-10 days) and I. degenerans survived the shortest period (4 days). No negative intra-specific interaction between immatures was observed with P. persimilis when food was available and in the absence of food this species tended to starve rather than act cannibalistically. Both N. californicus and N. cucumeris showed a low degree of cannibalism between immatures, either when food was available, or when starved but given access to water. Even when food was available survival of I. degenerans fell by 30% in 4 days and remained at 60-70% for 3 further days; survival continued to decline rapidly when they were starved but provided with water. This indicates that immatures of I. degenerans could either feed on dead conspecifics or that they were capable of a degree of cannibalism. Adult females of P. persimilis did not feed on conspecific eggs even when deprived of food but provided with water. Adult female N. californicus and N. cucumeris did feed on conspecific eggs but at a low level (<1 egg per day), which occurred only after 48 h starvation. Although egg cannibalism occurred more consistently with adult female I. degenerans than with other mite species it was at a low level (<1 egg per day). If the tendency to cannibalism, not just of eggs but with more susceptible life stages such as larvae, is reduced when water is available freely this could be important in determining the interactions that occur under natural conditions.
PDF
