High Speed flywheel and test rig design for rural energy storage

There is considerable growth in the renewable energy sector to contribute to sustainable development, environmental conservation and most importantly to provide affordable energy to isolated rural communities of sub-Saharan Africa. Renewable energy sources such as solar and wind require energy storage since the source of energy is intermittent. Electrochemical batteries especially from lead acid are commonly used to store energy in Solar Home Systems (SHS) for rural electrification in sub-Saharan Africa. Disadvantages such as low efficiencies, low life cycle costs, high maintenance, comparatively short life and serious environmental and human toxicity effects exist. Since recycling is not widespread, replacement costs are high, as are the resultant environmental damage and health hazards from lead and sulphuric acid. In this thesis, an electromechanical flywheel energy storage device is proposed as an alternative to a lead acid battery in order to increase efficiency, life expectancy, increased high depth of discharge, low life cycle cost and elimination of adverse environmental effects. Due to income and service skill constraints in rural areas, the proposed, high speed flywheel systems (for long time energy storage) will require the use of low cost configurations and topologies, special considerations on the flywheel rotor profile design, robust electrical machines, simple power electronics and a low cost bearing set. Low loss magnetic bearings are also possible but were limited by time while also making their maintenance complex especially in rural areas. Conventional high strength composite materials used in flywheel rotor manufacture for high speed operation are expensive. Therefore there is a need to develop techniques to profile the rotor shape so as to improve on material usage and exhibit lower mechanical stresses. A robust electrical machine topology for high speed operation and a simple drive system are investigated to ensure simple assembly, low cost and low maintenance. vii The various flywheel components were designed using analytical and numerical methods. Two techniques were used to develop two optimal profiles for the flywheel rotor structure. Partial differential equations and analytical solutions were employed to develop the profiles. Analytical equations were used to design the electrical machine, drive, bearing system and other accessories. The final electromechanical battery prototype consisted of a composite flywheel rotor made from E-glass fibre materials, double rotor Axial Flux Permanent Magnet (AFPM) machine and a drive system using Brushless DC (BLDC) mode of operation. The system was designed for 300Wh of energy storage for the delivery of 100W and 500W of power and an operating speed range of 8,000 rpm-25,000 rpm. The design and development of the flywheel energy storage system and test rig using locally available materials was investigated. Experiments were conducted for speeds up to 6,000 rpm. The electromechanical battery was able to store a maximum of 77Wh of energy. The shortfall of the system to meet its design specifications was investigated and found to have been caused by vibrations resulting from prototyping issues. A thermal model was developed to predict the temperature rise in the system which showed a good correlation with the experimental results

Practical considerations for low pressure solar water heaters in South Africa

This paper presents the results of the design parameters that affect natural convection of Low Pressure (LP) Solar Water Heaters (SWH) in South Africa. Fluid flow plays an important role in the heat transfer process associated with natural convection. Three partial differential governing equations were considered. These equations are non-dimensionalized and a similarity solution was applied to obtain two coupled non-linear ordinary differential equations which are solved in MATLAB. Two scenarios were considered for the simulation, a vertical wall with a constant wall temperature and a vertical wall with a constant heat flux. The temperature and velocity profiles were obtained for both scenarios and compared. The effect of the length, diameter and tilt angle of the tube in relation to the amount of heat transferred to the water was investigated specifically for Cape Town. These results are used to discuss design and installation considerations for LP SWHs and are presented in the paper

Considerations for a sustainable hybrid mini-grid system: A case for Wanale village, Uganda

The extension of modern energy services to rural sub-Saharan Africa has continuously provided a challenge to energy utilities. The continued reliance on diesel generators for rural electrification is increasingly becoming unsustainable, due to a number of factors, among which includes their high fuel dependency, and the uncertainty surrounding the price and availability of fossil fuels. While the influx of renewable energy technologies has provided a means for providing off-grid electrification services, the intermittent nature of renewable resources poses a challenge, as energy generation does not always coincide with usage. Through a combination of renewable energy technologies, energy storage, and conventional diesel generation, a hybrid mini-grid system is able to achieve synergy in operation, hence providing a reliable means of extending electricity services to rural consumers. In this paper, a hybrid mini-grid system is proposed for the supply of electricity to a remote village in Uganda. Renewable energy resources are identified, an estimation of the projected village short-term electricity demand is modelled, and using HOMER software, a hybrid mini-grid system is designed, components sized, and the system optimized for efficient and reliable operation to meet the village demand at an affordable cost. A well designed and operated hybrid mini-grid system offers a viable tool for the electrification of even the remotest of areas

The potential impact of small-scale flywheel energy storage technology on Uganda’s energy sector

The energy crisis in Uganda has caused a sharp decline in the growth of the industry sector from 10.8% to 4.5% between 2004/5 and 2005/6. This crisis has escalated the power disruptions, which have had adverse effects on various sectors. While business owners have resorted to importation of fossil fuel generators that have increased the cost of production, others have resorted to battery energy storage systems to cater for short outages, which are limited in life span, depth of discharge, among others. These interventions have, thus, further in-creased the cost of goods and services. In addition, the rural populations using solar home systems incur high battery maintenance and replacement costs. In this paper an electromechanical flywheel battery is proposed as a better alternative in mitigating energy storage problems. It is found that by replacing the battery storage systems with the electromechanical flywheel battery, a saving of up to 35% on cost of energy can be made in the solar home systems and for the industry sector, the power disruptions could be reduced

Considerations for a sustainable hybrid mini-grid system: A case for Wanale village, Uganda

The extension of modern energy services to rural sub-Saharan Africa has continuously provided a challenge to energy utilities. The continued reliance on diesel generators for rural electrification is increasingly becoming unsustainable, due to a number of factors, among which includes their high fuel dependency, and the uncertainty surrounding the price and availability of fossil fuels. While the influx of renewable energy technologies has provided a means for providing off-grid electrification services, the intermittent nature of renewable resources poses a challenge, as energy generation does not always coincide with usage. Through a combination of renewable energy technologies, energy storage, and conventional diesel generation, a hybrid mini-grid system is able to achieve synergy in operation, hence providing a reliable means of extending electricity services to rural consumers. In this paper, a hybrid mini-grid system is proposed for the supply of electricity to a remote village in Uganda. Renewable energy resources are identified, an estimation of the projected village short-term electricity demand is modelled, and using HOMER software, a hybrid mini-grid system is designed, components sized, and the system optimized for efficient and reliable operation to meet the village demand at an affordable cost. A well designed and operated hybrid mini-grid system offers a viable tool for the electrification of even the remotest of areas

Practical considerations for low pressure solar water heaters in South Africa

This paper presents the results of the design parameters that affect natural convection of Low Pressure (LP) Solar Water Heaters (SWH) in South Africa. Fluid flow plays an important role in the heat transfer process associated with natural convection. Three partial differential governing equations were considered. These equations are non-dimensionalized and a similarity solution was applied to obtain two coupled non-linear ordinary differential equations which are solved in MATLAB. Two scenarios were considered for the simulation, a vertical wall with a constant wall temperature and a vertical wall with a constant heat flux. The temperature and velocity profiles were obtained for both scenarios and compared. The effect of the length, diameter and tilt angle of the tube in relation to the amount of heat transferred to the water was investigated specifically for Cape Town. These results are used to discuss design and installation considerations for LP SWHs and are presented in the paper

Identification of PKD1L1 Gene Variants in Children with the Biliary Atresia Splenic Malformation Syndrome

Biliary atresia (BA) is the most common cause of end‐stage liver disease in children and the primary indication for pediatric liver transplantation, yet underlying etiologies remain unknown. Approximately 10% of infants affected by BA exhibit various laterality defects (heterotaxy) including splenic abnormalities and complex cardiac malformations — a distinctive subgroup commonly referred to as the biliary atresia splenic malformation (BASM) syndrome. We hypothesized that genetic factors linking laterality features with the etiopathogenesis of BA in BASM patients could be identified through whole exome sequencing (WES) of an affected cohort. DNA specimens from 67 BASM subjects, including 58 patient‐parent trios, from the NIDDK‐supported Childhood Liver Disease Research Network (ChiLDReN) underwent WES. Candidate gene variants derived from a pre‐specified set of 2,016 genes associated with ciliary dysgenesis and/or dysfunction or cholestasis were prioritized according to pathogenicity, population frequency, and mode of inheritance. Five BASM subjects harbored rare and potentially deleterious bi‐allelic variants in polycystin 1‐like 1, PKD1L1, a gene associated with ciliary calcium signaling and embryonic laterality determination in fish, mice and humans. Heterozygous PKD1L1 variants were found in 3 additional subjects. Immunohistochemical analysis of liver from the one BASM subject available revealed decreased PKD1L1 expression in bile duct epithelium when compared to normal livers and livers affected by other non‐cholestatic diseases. Conclusion WES identified bi‐allelic and heterozygous PKD1L1 variants of interest in 8 BASM subjects from the ChiLDReN dataset. The dual roles for PKD1L1 in laterality determination and ciliary function suggest that PKD1L1 is a new, biologically plausible, cholangiocyte‐expressed candidate gene for the BASM syndrome

Household and maternal risk factors for malaria in pregnancy in a highly endemic area of Uganda: a prospective cohort study.

BACKGROUND: Malaria in pregnancy is a major public health challenge, but its risk factors remain poorly understood in some settings. This study assessed the association between household and maternal characteristics and malaria among pregnant women in a high transmission area of Uganda. METHODS: A nested prospective study was conducted between 6th September 2016 and 5th December 2017 in Busia district. 782 HIV uninfected women were enrolled in the parent study with convenience sampling. Socioeconomic and house construction data were collected via a household survey after enrolment. Homes were classified as modern (plaster or cement walls, metal or wooden roof and closed eaves) or traditional (all other homes). Maternal and household risk factors were evaluated for three outcomes: (1) malaria parasitaemia at enrolment, measured by thick blood smear and qPCR, (2) malaria parasitaemia during pregnancy following initiation of IPTp, measured by thick blood smear and qPCR and (3) placental malaria measured by histopathology. RESULTS: A total of 753 of 782 women were included in the analysis. Most women had no or primary education (75%) and lived in traditional houses (77%). At enrolment, microscopic or sub-microscopic parasitaemia was associated with house type (traditional versus modern: adjusted risk ratio (aRR) 1.29, 95% confidence intervals 1.15-1.45, p < 0.001), level of education (primary or no education versus O-level or beyond: aRR 1.13, 95% confidence interval 1.02-1.24, p = 0.02), and gravidity (primigravida versus multigravida: aRR 1.10, 95% confidence interval 1.02-1.18, p = 0.009). After initiation of IPTp, microscopic or sub-microscopic parasitaemia was associated with wealth index (poorest versus least poor: aRR 1.24, 95% CI 1.10-1.39, p < 0.001), house type (aRR 1.14, 95% CI 1.01-1.28, p = 0.03), education level (aRR 1.19, 95% CI 1.06-1.34, p = 0.002) and gravidity (aRR 1.32, 95% CI 1.20-1.45, p < 0.001). Placental malaria was associated with gravidity (aRR 2.87, 95% CI 2.39-3.45, p < 0.001), but not with household characteristics. CONCLUSIONS: In an area of high malaria transmission, primigravid women and those belonging to the poorest households, living in traditional homes and with the least education had the greatest risk of malaria during pregnancy

Erratum to: Mutation screening in 86 known X-linked mental retardation genes by droplet-based multiplex PCR and massive parallel sequencing

Item does not contain fulltext[This corrects the article DOI: 10.1007/s11568-010-9137-y.].1 december 200

Large-scale sequencing identifies multiple genes and rare variants associated with Crohn’s disease susceptibility

peer reviewe