Investigations into microgrid sizing and energy management strategies

PhD ThesisThe evolution of microgrids represents a significant step towards the transition to more sustainable power systems. Recent trends in microgrids include the integration of renewable energy resources (RERs), alternative energy resources (AERs) and energy storage systems (ESSs). However, the integration of these systems creates new challenges on microgrid operation because of their stochastic and intermittent nature. To mitigate these challenges, determining the appropriate size together with the best energy management strategy (EMS) systems are essential to ensure economic and optimal performance. This thesis presents an investigation into sizing and energy management of microgrids. In the first part of the thesis, an analytical and economic sizing (AES) approach is developed to find the optimal size of a grid-connected photovoltaicbattery energy storage system (PV-BESS). The proposed approach determines the optimal size based on the minimum levelised cost of energy (LCOE). Fundamental to this approach obtains an improved formula of LCOE which includes new parameters for reflecting the impact of surplus PV energy and the energy purchased from the grid. In the second part of this thesis, an integrated framework is proposed for finding the best size-EMS combination of a stand-alone hybrid energy system (HES). The HES consists of PV, BESS, diesel generator, fuel cell, electrolyser, and hydrogen tank. The proposed framework includes three consecutive steps; first, performing the AES to obtain the initial size of the HES, second, implementing the initial EMS using finite automata (FA) and instantiating multiple EMSs; and third, developing an evaluation model to assess the instantiated EMSs and extract the featured conditions to produce an improved EMS. Then the AES approach is re-exercised using the improved EMS to obtain the best size-EMS combination. The core of this framework is utilising FA to implement various EMSs and capturing the impact of selecting the best EMS on the sizing of the HES. Furthermore, a sensitivity analysis is performed to address the uncertainty in demand and solar radiation data showing their effect on the HES performance. The analysis is carried out by assuming variations in solar radiation and demand annual data. Several scenarios are generated from the sensitivity analysis, and a number of performance indices are computed for each scenario. Following that, a vii fuzzy logic controller is designed using the performance indices as fuzzy input sets. The objective of this controller is to modify the EMS obtained from the integrated framework. This can be accomplished by detecting any changes in the demand and solar radiation and accordingly modify the operating conditions of the diesel generator, fuel cell, and electrolyser. The performance of the proposed approaches is validated using real datasets for both demand and solar radiation. The results show the optimal size and EMS for both grid-connected and stand-alone microgrids. Moreover, the designed fuzzy logic controller enables the microgrid to mitigate the uncertainty in the demand and generation data. The proposed approaches can be used with various scales of microgrids to extract manifold benefits where reliability, environmental and cost requirements can not be tolerated.Applied Science Private University in Jorda

Abuse among school going adolescents in three major cities of Pakistan: is it associated with school performances and mood disorders?

Objective: To assess the proportion of various types of abuses and their association with school performances and psychological stress among adolescents from three major cities of Pakistan. Methods: The cross-sectional school survey was conducted from March to September 2009, comprising adolescent students at six schools in Karachi, Lahore and Quetta. Data was collected using a self-administered and pre-tested questionnaire by trained medical students. SPSS 16 was used for statistical analysis.. Results: Of the 414 subjects in the study, there were 223(54%) boys and 191(46%) girls with an overall mean age of 14.36 ±1.08 years. In all, 140(33.7%) participants were physically abused and 236(57%) participants were verbally abused in the preceding 12 months. Besides, 245(59.2%) were involved in physical fight and 195(47.1%) had suffered injury during the preceding year. There were 171(41.4%) subjects having suffered bullying during the same period. Verbal abuse (p=0.05), physical fight (p=0.05) and bullying (p\u3c0.001) were significantly associated with poor school performances among adolescents. Physical abuse (p=0.05), verbal abuse (p=0.003), injury (p=0.02) and bullying (p\u3c0.001) were significantly associated with psychological stress. Conclusion: Various types of abuse were quite prevalent in adolescents that were significantly associated with poor school performance and poor mental health

Safety Evaluation of Stay Cables of Cable-Stayed and Extradosed Bridges via Deterministic and Non-deterministic Methods

Cable-stayed and extradosed bridges are thought to be identical structures because both bridges use stay cables for reinforcement. However, the safety factors of their stay cables are stipulated differently in many international standards, i.e., Japanese specifications suggest the safety factors of 2.5 and 1.67 for the design of cable-stayed and extradosed bridges, respectively. In this chapter, a parametric study is carried out for the evaluation of safety factors of stay cables by employing the deterministic and nondeterministic methods at limit states. As a result, it is found that the safety factors in the range of 2.3–2.5 and 1.67 are indispensable for the safe design of cable-stayed and extradosed bridges, respectively, to satisfy the conditions of limit states and target reliability index

Breaking bad news: exploring patient\u27s perspective and expectations

OBJECTIVE: To explore patient\u27s perspectives and expectations from physicians with respect to breaking of bad news. METHODS: A cross-sectional survey was carried out in the Community Health Centre of a tertiary care teaching hospital in Pakistan. All consenting individuals from 18 to 60 years of age were interviewed on the basis of a structured, pre-tested questionnaire. RESULTS: The response rate for this study was 91.3%. A total of 400 respondents completed the full interview. About 60% patients had a fairly accurate idea about the implications of the phrase bad news . A big proportion (44.1%) of people reported that bad news had been broken to them previously with incomplete details. From their personal experience, most respondents quoted disease diagnosis and chances of survival as most commonly encountered bad news. Diagnosis of cancer or its recurrence was stated as the most likely example of bad news (35.5%). A significant majority of respondents (40.5%) stated that it\u27s the patient\u27s absolute right to know bad news. A significant association for the relationship between both age as well as the gender of the respondents and type of emotional response expressed on hearing bad news (p = 0.000) was observed. CONCLUSION: This study documents the perceptions and expectations of patients from their physicians with regards to breaking of bad news. Most of the respondents wanted their doctors to be honest and upfront during the process

Clinical profile and outcomes of paediatric patients with diabetic ketoacidosis at a tertiary care hospital in Pakistan

OBJECTIVES: This study aims to present an experience in the management and clinical features of 88 children presenting with diabetic ketoacidosis (DKA) from Pakistan. METHODS: A retrospective medical chart review of all patients, \u3c or = 15 years of age, who presented to the Aga Khan University Hospital, Karachi, Pakistan in the last ten years with a diagnosis of diabetic ketoacidosis was carried out. Severity of DKA was defined as mild (venous pH \u3c 7.30 or bicarbonate=15mEq/l), moderate (venous pH \u3c 7.2 or bicarbonate = 10 mEq/l) and severe (venous pH \u3c 7 or bicarbonate \u3c 5 mEq/l). These classes correspond to 1st, 2nd and 3rd degrees of diabetic ketoacidosis severity respectively. Cases in which diabetic ketoacidosis had occurred at onset of diabetic diagnosis were not included in the study. RESULTS: Mean age was 7.5 +/- 3.6 years; 58 (66%) patients were male. Twenty six patients had mild diabetic ketoacidosis, 44 had moderate while 18 had severe diabetic ketoacidosis at the time of presentation. Severity of diabetic ketoacidosis was significantly associated with the presence of infection, history of omission of insulin, poor compliance, presence of shock at time of presentation, length of stay in the hospital, final outcome (p \u3c 0.01 for each of these associations) and Glasgow Coma Scale score (p = 0.02). Mortality in this series was 3.4%. CONCLUSION: Poor compliance was associated with the severity of diabetic ketoacidosis. Paediatric endocrinologists\u27 should ensure that patients and their parents understand the importance of the need for regular insulin injections and regular monitoring of blood glucose

Prevalence of obesity in school-going children of Karachi.

Background: Obesity is an emerging problem in Pakistan. The authors sought to determine prevalence of obesity and malnutrition in school-going children, from grades 6(th) to 8(th) of different schools of Karachi and assess associations that affect the weight of the children. Methodology/Principal Findings: A cross sectional Study Design with children studying in grades 6(th) to 8(th) grade, in different schools of Karachi. We visited 10 schools of which 4 consented, two subsidized government schools and two private schools. A questionnaire was developed in consultation with a qualified nutritionist. Height and weight were measured on calibrated scales. A modified BMI criterion for Asian populations was used. Data was collected from 284 students. Of our sample, 52% were found to be underweight whereas 34% of all the children were normal. Of the population, 6% was obese and 8% overweight. Of all obese children, 70% belonged to the higher socio-economic status (SES) group, while of the underweight children, 63.3% were in the lower SES. Amongst obese children in our study, 65% ate meat every day, compared to 33% of normal kids. Conclusion: Obesity and undernutrition co-exist in Pakistani school-children. Our study shows that socio-economic factors are important since obesity and overweight increase with SES. Higher SES groups should be targeted for overweight while underweight is a problem of lower SES. Meat intake and lack of physical activity are some of the other factors that have been highlighted in our study.

The role of computed tomography for identifying mechanical bowel obstruction in a Pakistani population

Objective: To retrospectively review our experience of CT scan in cases with a final diagnosis of surgically confirmed mechanical bowel obstruction. Methods: It is a retrospective analytical study, done from 2003 to 2008. All adult patients having undergone laparotomy in addition to a preoperative abdominal CT scan over a 5 year period were identified through the medical records and their case notes reviewed. Taking surgery to be the gold standard for diagnosing mechanical bowel obstruction, we compared results of the CT with operative findings to determine the sensitivity, specificity, positive and negative predictive values of CT scans. The data was analyzed using SPSS version 16.0. Results: A total of 271 patient records were reviewed. The mean age was 46 +/- 19 years and (64%) were men. Mechanical intestinal obstruction was found in 104 patients on laparotomy and CT scan had diagnosed 97 of these. The sensitivity and specificity was 93% respectively. CT scanning correctly identified the cause of the obstruction in 72 (74%) cases. The common reasons for bowel obstruction identified by surgery were adhesions 29 (40%), neoplasm 12 (17 %) and hernias 7 (10%). Conclusion: CT scans are reliable at diagnosing intestinal obstruction with a high sensitivity and specificity but they are not as accurate at defining the etiology of the obstruction

Effect of visible range electromagnetic radiations on Escherichia coli

Background: Escherichia coli is the agent responsible for a range of clinical diseases. With emerging antimicrobial resistance, other treatment options including solar/photo-therapy are becoming increasingly common. Visible Range Radiation Therapy/Colour Therapy is an emerging technique in the field of energy/vibrational medicine that uses visible spectrum of Electromagnetic Radiations to cure different diseases. In this study, our goal was to understand the effect of Visible Range Electromagnetic Radiations on E. coli (in vitro) and therefore find out the most appropriate visible range radiation for the treatment of diseases caused by E. coli.Materials and Methods: A total of 6 non-repetitive E. coli isolates were obtained from urine samples obtained from hospitalized patients with UTI. Single colony of E. coli was inoculated in 3 ml of Lysogeny Broth (LB) and 40 μl of this E. coli suspension was poured into each of the plastic tubes which were then irradiated with six different wavelengths in the visible region (Table. 1) after 18 hours with one acting as a control. The Optical Densities of these irradiated samples were then measured. Furthermore, scanning electron microscopy (TEFCAN ZEGA3) was carried out.Results: The analysis of the microscopic and SEM images of irradiated E. coli samples with six different visible range radiations is representative of The fact that E. coli responded differently to every applied radiation in the visible region and the most profound inhibitory effects were that of 538nm Visible Range Radiation (Green) which proved to be bactericidal and 590nm Visible Range Radiation (yellow) which was bacteriostatic. The enhanced growth of E. coli with varying degrees was clearly observed in 610nm (orange), 644nm (red), 464nm (Purple) and 453nm (blue).Conclusion: It can be concluded that 538nm (Green) and 590nm (Yellow) can effectively be used for treating E. coli borne diseases.Keywords: Visible Range Radiation Therapy, E. coli, UTI, Alternative Treatment, Colour Therap

Severe combined immune deficiency syndrome

Objective: To determine the clinico-demographic features and laboratory parameters of children with severe combined immunodeficiency (SCID). Study Design: Case series. Place and Duration of Study: Department of Paediatrics and Child Health, the Aga Khan University, Karachi, from July 2006 to July 2011. Methodology: Thirteen infants who were discharged with a diagnosis of SCID were inducted in the study. Their clinicodemographic features and laboratory parameters were determined. Descriptive statistics has been used for computing frequency and percentage. Results: The median age at diagnosis was five months; 5 infants presented within 3 months of life. Three-fourth (77%) were males. Most of the infants were severely malnourished (85%) at the time of presentation. More than two-thirds (69%) were products of consanguineous marriages. All subjects had severe lymphopenia {absolute lymphocyte count (ALC) ranging between 170 – 2280} and low T and B lymphocyte counts. Conclusion: SCID should be considered in infants presenting with severe and recurrent infections. Low ALC (\u3c 2500/mm3), is a reliable diagnostic feature of SCID. These infants should be promptly referred to a facility where stem cell transplant can be done