Internal Model Loss Minimization Control of Permanent Magnet Synchronous Machine

Electric drives are very useful in propelling the wheels of hybrid electric vehicles (HEVs). They also play a central function in the electric power steering (EPS). This paper describes studies carried out on the efficiency optimization of an interior permanent magnet synchronous machine (IPMSM) for application in the EPS. An analytic loss- minimization algorithm for an IPMSM was derived and the optimization problem took into consideration copper, iron and stray losses. The proposed loss minimization algorithm is simple and cost effective to implement. From the simulations carried out, significant efficiency gains are possible with this model. The internal model control (IMC) method was employed to achieve current and speed control with acceptable sensitivity to machine parameters

Analytical Prediction for Grain Burn Time and Burning Area Kinematics in a Solid Rocket Combustion Chamber

This chapter proposes the application of Newtonian particle mechanics for the derivation of predictive equations for burn time, burning and unburnt area propagation for the case of a core propellant grain. The grain is considered to be inhibited in a solid rocket combustion chamber subject to the assumption that the flame propagation speed is constant for the particular solid fuel formulation and formation chemistry in any direction. Here, intricacies surrounding reaction chemistry and kinetic mechanisms are not of interest at the moment. Meanwhile, the physics derives from the assumption of a regressive solid fuel pyrolysis in a cylindrical combustion chamber subject to any theoretical or empirical burn rate characterization law. Essential parametric variables are expressed in terms of the propellant geometrical configuration at any instantaneous time. Profiles from simulation studies revealed the effect of modulating variables on the burning propagation arising from the kinematics and ordinary differential equations models. In the meantime, this mathematical exercise explored the tendency for a tie between essential kernels and matching polynomial approximations. In the limiting cases, closed form expressions are couched in terms of the propellant grain geometrical parameters. Notably, for the fuel burn time, a good agreement is observed for the theoretical and experimental results

Energy Efficiency of Sustainable Renewable Microgrids for Off-Grid Electrification

Energy efficiency (EE) has a key role to play in the rate of electrification towards decreasing energy poverty around the world. It has benefits to electrified urban and rural areas, as well as off-grid communities. Therefore, in this paper, we explore using empirical data, the impact of EE (as a form of demandside management) on the adoption of renewable microgrids for off-grid electrification in Sub-Saharan Africa. The study shows that improvements in the energy efficiency of commercial and residential appliances will optimize the availability of existing power resources, creating more access to underserved areas. An EE-centric power distribution model will also lead to higher value per energy served to under-served communities through renewable microgrids

A review of renewable off-grid mini-grids in Sub-Saharan Africa

Sub-Saharan Africa (SSA) is home to 75% of the world’s unelectrified population, and approximately 500 million of these live in rural areas. Off-grid mini-grids are being deployed on a large scale to address the region’s electrification inequalities. This study aims to provide a comprehensive review of the research on the off-grid renewable mini-grids in SSA. The study covers the current status of the level of deployment of off-grid mini-grids. It also reviews multi-criteria decision-making models for optimizing engineering, economics, and management interests in mini-grid siting and design in SSA. The statuses of financing, policy, and tariffs for mini-grids in SSA are also studied. Finally, the current status of energy justice research in respect of mini-grids in SSA is reviewed. The study shows the important role of decentralized renewable technologies in the electrification of SSA’s rural population. Within a decade since 2010, the rural electrification rate of SSA has increased from 17% to 28%, and 11 million mini-grid connections are currently operational. Despite these gains, the literature points to several injustices related to the present model by which SSA’s renewable mini-grids are funded, deployed, and operated. Hence, several recommendations are provided for the effective application of the energy justice framework (EJF) for just and equitable mini-grids in SSA

Software For Improved Online Teaching Of Power System Analysis For Undergraduates

In electric power system study, balanced system is often assumed. This is not usually so in a practical system, most especially in a distribution network in which consumers’ loads and or loading patterns vary. Hence, a single-phase cannot be sufficient to analyse a distribution network of three-phase lines and one neutral. In this study, Carson’s equation, which is a suitable approach for modelling the series impedance and shunt admittance of overhead line, is deployed to analyse a three-phase distribution network for which a computer-based WindMil application is used to verify. WindMil application is proposed in this study for distribution network analysis because of its robustness to handle several problems associated with it such as unbalanced system, voltage regulation, etc. Moreover, WindMil application is also user friendly and it is suitable for online teaching and learning of power system analysis with respect to novel coronavirus pandemic problem

Lower intestinal endoscopy- inaugural year experience from a private centre in Lagos, Nigeria

Background: Colonoscopy is an indispensable tool for investigating and intervening in disorders of the lower intestinal tract. There is an increasing body of data showcasing the findings and experiences of the various centers that carry out the procedure in Nigeria.Objectives: This study set out to document the patterns of patient presentation, clinical characteristics of such patients and findings at colonoscopy.Methodology: This was a retrospective study carried out on the records of the patients that presented for colonoscopy during the first year of operations (August 2014 to July 2015) of the endoscopy unit of Clinix Healthcare in Lagos, Nigeria. The endoscopy register was reviewed to retrieve clinical details of patients, the colonoscopy indication and findings.Results: A total of 125 colonoscopies were performed during this period. There were 85(68%) males and 40(32%) females, giving a male to female ratio of 2.1:1. The clients’ age ranged from 23 to 94years with a mean of 52.4years ±14.2. Most clients were in the 6th decade of life. Only 7(4.8%) had been referred for a routine screen. The most common symptom at presentation were haematochezia alone (73=58.4%) or in combination with other symptoms (90=72%). Others were alteration in bowel habits (15=12%), abdominal pain (12=9.6%) and suspected gastrointestinal bleeding as indicated by melaena stools or anaemia of undetermined origin (8=6.4%). A normal study was reported in 19(15.2%) procedures. Overall, the diagnostic yield was 84.8%. The most common abnormality was haemorrhoids as seen in a total of 68 patients. Other findings were suspected cancerous lesions in 25 patients, diverticular disease in 14 patients, polyps in 12 patients and features suggestive of mucosal inflammation alone in 6 patients.Conclusion: The findings from the first year of colonoscopy in our Lagosbased privately owned centre showed that the most common indication for referral was lower GI bleeding, and the most commonly diagnosed lesion was haemorrhoids. These, are in keeping with previously documented series from other centres in the country.Keywords: Anaemia, bowel habits, haematochezia, haemorrhoids, male

Evaluation of Energy-efficiency in Lighting Systems for Public Buildings

Adoption of energy efficiency and conservation techniques in public buildings in Nigeria is significantly low due to the ignorance of its potential benefits. Consequently, this study presents the prospects of energy saving using different methods in a public building at a Nigerian University. A proposed remodelled students’ residential hostel at the University of Lagos, Nigeria was chosen as a pilot study. This research utilized three energy efficient lighting technology alternatives namely; intelligent controlled Incandescent lamp (ICIL), compact fluorescent lamp (CFL), and intelligent controlled CFL (ICCFL) and compared with a base case of conventional incandescent lighting configuration. Energy consumption, at the proposed hostel is analysed and modelled. The effectiveness of each lighting technology alternative and base case in terms of cost is estimated using economic indices such as the net present value (NPV), savings to investment ratio (SIR) and the discounted payback period (DPP). Results show that the CFL lighting technology give 39% cost benefit as compared to ICCFL which gives 11% overall cost benefit. From the study, it is established that adoption of energy efficient lighting techniques save a significant amount of energy, operational cost, electricity bills and consequently reduce emissio