Estimating the Yield of Micro Wind Turbines in an Urban Environment: A Methodology

Micro wind turbines currently have the majority share of micro (electricity) generation installations in Ireland. These technologies are being installed predominantly in rural environments, and current applications to the Distribution Services Operator (DSO) for connection of all types of micro generator stand at less than 500. Poor market dissemination of information and research findings compounded with poor options for spill payment - as well as onerous planning restrictions do not –it appears - create a platform conducive to encouraging development in this market. This paper outlines the complexities associated with evaluating the wind resource within an urban environment and investigates the means to ‘estimate’ wind regimes in an urban environment based on an extrapolation of a reference wind speed from a rural environment into the urban area. Methodologies for estimating the wind speed in such circumstances are considered with modeled wind data – benchmarked against wind data acquired from a site in the city centre - being applied to a set of commercially available wind turbines

Impact Assessment of High-Power Domestic EV Charging Proliferation of a Distribution Network

Transport electrification is becoming the mainstream as a means to improve efficiency, performance, andsustainability of transportation systems. Electrical vehicles (EVs) can help to de-carbonise the environment, but a downside isthe technical issues presented to the low-voltage distribution network. To quantify the stochastic nature of transport-affectedelectrification, probabilistic load flow is employed. Monte Carlo-based simulation is applied to accommodate the probabilisticuncertainties associated with variable EV charging patterns. This study considers high-power charging (up to 11 kW) at thedomestic level while monitoring power quality variations (voltage drop, voltage unbalance factor, voltage sag) standards. Thiswork focuses on the Irish and UK, distribution system operator\u27s–transmission system operator\u27s perspectives, as it will help toidentify the likely impacts due to high-EV charger proliferation at household locations. The results indicate that if a 3.68 kWcharger is used at the domestic level, it is possible for 40% of total household consumers to connect EVs directly to thedistribution network without any power quality breaches. Furthermore, the proliferation of EV can be increased up to 100% ifconstrained to the start, and middle portions of the network (relative to the feeder substation transformer). For higher chargercapacities (up to 11 kW), a bottleneck is presented regarding a resultant voltage unbalance factor

The Potential for Power Quality Problem Mitigation Through STATCOM

Consideration of spatial and temporal diversity of EV charging demand has been demonstrated to reduce the estimating impacts on the distribution networks. The data formulation is based on impact studies of Electrical vehicles (EV s) on distribution networks. It is suggested that Distribution System Operator (DSO) could benefit for new innovation/advancement in the market (BESS-STATCOM) in a way that makes networks more reliable/robust, In this regard such innovation creates more opportunities for demand side management, reduces planning uncertainties associated with stochastic nature of EV charging and makes space for demand side management. This work considers probabilistic load flow in a representative unbalanced distribution network and through Monte Carlo simulation increased the hosting capacity for DG/EV is considered in an Irish/UK context. Furthermore, this paper considers the potential for a distribution network deployed STATCOM in supporting EV penetration, while maintaining appropriate power quality (voltage) standards. To reduce the computation burden of Monte Carlo simulation an alternative (novel but simple) method is applied. In terms of the Irish/UK DSO perspective, this work will help to increase the hosting capacity of DG/EV without breaching power quality limits

Estimating the Wind Resource in an Urban Area: a Case Study of Micro Wind Generation Potential in Dublin, Ireland

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

Role of reactive power (STATCOM) in the planning of distribution network with higher EV charging level

In recent years, new trends in electrification of the transport sector have been a major concern for distribution grid operators. New types of flexible, uncontrollable loads, such as EV, influence the reliability of distribution networks. This work is related to the distribution system planning framework, with a particular focus on uncoordinated flexible EV loads. The main focus is the enhancement of the hosting capacity of EVs on distribution networks, while maintaining power quality (especially voltage magnitude and voltage unbalance), which is ultimately a pre-requisite for increasing prosumer engagement. Several EV charging scenarios, in the context of UK/Irish distribution networks with increased penetration of EV prosumers are considered. The results show that reactive power compensation through STATCOM, in the context of EV integration, can provide continuous voltage support and thereby facilitate 90% penetration of network customer EV connections at a normal EV charging rate (3.68 kW). If fast charging (up to 11 kW) is employed, \u3c30% of network EV customers can be accommodated due to bottlenecks presented by the substation transformer loading

Surgical management of posterior fossa metastases

The diagnosis of brain metastases is associated with a poor prognosis reflecting uncontrolled primary disease that has spread to the relative sanctuary of the central nervous system. 20 % of brain metastases occur in the posterior fossa and are associated with significant morbidity. The risk of acute hydrocephalus and potential for sudden death means these metastases are often dealt with as emergency cases. This approach means a full pre-operative assessment and staging of underlying disease may be neglected and a proportion of patients undergo comparatively high risk surgery with little or no survival benefit. This study aimed to assess outcomes in patients to identify factors that may assist in case selection. We report a retrospective case series of 92 consecutive patients operated for posterior fossa metastases between 2007 and 2012. Routine demographic data was collected plus data on performance status, primary cancer site, details of surgery, adjuvant treatment and survival. The only independent positive prognostic factors identified on multivariate analysis were good performance status (if Karnofsky performance score >70, hazard ratio (HR) for death 0.36, 95 % confidence interval (CI) 0.18–0.69), adjuvant whole brain radiotherapy (HR 0.37, 95 % CI 0.21–0.65) and adjuvant chemotherapy where there was extracranial disease and non-synchronous presentation (HR 0.51, 95 % CI 0.31–0.82). Patients presenting with posterior fossa metastases may not be investigated as thoroughly as those with supratentorial tumours. Staging and assessment is essential however, and in the meantime emergencies related to tumour mass effect should be managed with steroids and cerebrospinal fluid diversion as required

Enhanced Network Voltage Management (NVM) Techniques Under the Proliferation of Rooftop Solar PV Installation in Low Voltage Distribution Network (LVDN)

Proliferation of rooftop solar PV distributed generator (PVDG) installation in low voltage distribution network (LVDN) imposes voltage fluctuation challenges that are a threat to distribution system operators. Reactive power control (RPC) methods are insufficient in isolation to combat the overvoltage fluctuations manifested in LVDN with significant grid-tied PVDG installations. Whereas active power curtailment (APC) control can alleviate the voltage fluctuation in such situations and it is achieved at the cost of reduced active power injection. This paper explores how deficiencies in both RPC and APC as separate approaches can be mitigated by suitably combining RPC and APC algorithms. Strategies combining two RPCs and one RPC in conjunction with APC are proposed as two coordinating algorithms by means of instantaneous measurement of node voltage and active power. These coordinating algorithms are embedded in all the rooftop PVDG grid-tied-inverters (GTI), where the GTI coordinates among them for voltage support without exceeding individual inverter VA rating. The result of the combined approach show significant improvement in managing and stabilising the voltage and allows the penetration of PVDG to be increased from 35.65% to 66.7% of distribution transformer (DT) kVA rating

The Progressive Development of Turbulence Statistics and Its Impact on Wind Power Predictability

Wind resource assessment is a critical parameter in a diverse range of considerations within the built environment. Engineers and scientists, engaging in building design, energy conservation/application and air-quality/air-pollution control measures, need to be cognisant of how the associated wind resource imposes increased complexities in their design and modelling processes. In this regard, the morphological heterogeneities within these environments, present significant challenges to quantifying the resource and its turbulent characteristics. This paper presents three aspects of turbulence assessment within the built environment. Firstly, an analysis of how turbulence is currently quantified is considered. The industry standard, Turbulent Intensity (TI) is compared with a proposed alternative metric described as Turbulent Fourier Dimension modelling (TDf). Secondly, the application of the turbulence assessment is considered with respect to how TI affects the productivity of small/micro wind turbines in complex environments though Gaussian distribution analysis. Finally, an extended discussion on current developments such as the concept of a turbulence rose and the ongoing development of statistical modelling is presented

Levilised Cost of Energy Analysis: a Comparison of Urban (Micro) Wind Turbines and Solar PV Systems

The relatively high capital cost associated with micro wind energy systems and the resulting long payback periods, makes for a challenging argument for these technologies. However, as the global population becomes increasingly concentrated in urban areas, the potential for accessing any available renewable energy resource, including wind and solar PV, could become a necessity. This infers that the economics associated with small/micro energy systems need to be better appreciated. This paper presents a levelised cost of energy (LCOE) analysis for rural/urban small/micro wind energy systems that is contextualised by a solar PV system comparison. Further insight is offered through a design of experiments (DOE) consideration that affords an understanding of how system parameters, such as primary energy (rural/urban wind resource and solar insolation), capital cost and loan/finance interest rate individually and collectively affect the respective technologies. The results suggest that from an economic justification perspective, urban installations are difficult to justify and solar PV systems, with the associated lowering system costs, are challenging the viability of small/micro rural wind energy systems

Advances in the Quantification of Turbulence: a Wind Resource Characteristic

Wind resource assessment is a critical parameter in a diverse range of considerations within the built environment. Engineers and scientists, engaging in building design, energy conservation/application and air-quality/air-pollution control measures, need to be cognisant of how the associated wind resource imposes increased complexities in their design and modelling processes. In this regard, the topographical heterogeneities within these environments, present significant challenges to quantifying the resource and its turbulent characteristics. Indeed, from the perspective of assessing the wind resource within the built environment, topographical heterogeneity is the primary proponent of turbulence and the main inhibitor to acquiring meaningful measurements. This paper presents two aspects of turbulence assessment within the built environment. Firstly, an analysis of how turbulence is quantified is considered. The industry standard, turbulent intensity (TI) [1] is compared with a proposed alternative metric described as Fourier Dimension modelling (Df). Secondly, the application of the turbulence assessment is considered with respect to how it affects the productivity of small/micro wind turbines in complex environments. The TI metric is the only metric utilised in the consideration of wind turbine productivity though Gaussian distribution analysis [2]. The TDf model has yet to be developed sufficiently to apply it in this regard. [1] IEC, International Standard 61400-2. Wind Turbines - Part 2: Design requirements for small turbines, ed, 2006. [2] A. Albers Turbulence Normalisation of Wind Turbine Power Curve Measurements, Deutsche WindGuard Consulting GmbH,2009