Thermodynamic Modeling of Allothermal Steam Gasification in a Downdraft Fixed-bed Gasifier

A process of converting a solid carbonaceous fuel into a gaseous energy carrier in presence of a gasifying medium at high temperature is called gasification. The resulting gaseous energy carrier, known as producer gas, is more versatile in its use than the original solid fuel. Gasification is widely considered as a more efficient and less polluting initial thermochemical upstream process of converting biomass to electricity. The objective of this study was to investigate the process of allothermal steam gasification in a fixed-bed downdraft gasifier for improved quality (HHV, high hydrogen content) of the producer gas generated. The study involved thermodynamic equilibrium modeling based on equilibrium approach in which the concentrations of the gaseous components in the producer gas at equilibrium temperature are determined based on balancing the moles in the overall gasification equation. The results obtained suggest that the maximum equilibrium yield of producer gas with high energy density is attained at a gasification temperature of around 820oC and a steam/biomass ratio of 0.825 mol/mol. The equilibrium yield was richer in hydrogen at 52.23%vol, and with a higher heating value of 11.6 MJ/Nm3. Preliminary validation of the model results using experimental data from literature shows a close relationship. The study has further shown the advantage of using steam as a gasifying medium towards the improved quality of the producer gas generated.
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Technical, Economic and Sustainability Considerations of a Solar PV Mini Grid as a Tool for Rural Electrification in Uganda

The challenges facing rural electrification in Uganda are diverse with less than 3% of the rural population having access to electricity. The establishment of mini-grids powered by renewable energy sources makes it possible to electrify remote areas at affordable rates. In this study, an assessment of a solar PV mini-grid system to provide electricity to forty households in rural Uganda was carried out. The considered system comprised six solar modules each rated 175 Wp, a controller, off-grid inverter and batteries with a capacity of 600 Ah. Manufactured by SMA, the Sunny Island inverter proposed for the mini-grid would ensure provision of grid-quality electricity. The study aimed to investigate the mini-grid’s technical design with focus on optimal distribution against constraints of voltage drops, electrical losses and increasing load. Customised load limiters shared between households using thermistors were included to reduce costs and limit consumption. The incomes of rural households are often seasonal and thus issues pertaining to affordability and sustainability were also considered. Results of the economic analysis showed a payback period of less than 5 years given an affordable fixed monthly tariff for the case study area.
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Diffusion of solar energy technologies in rural Africa: Trends in Kenya and the LUAV experience in Uganda

The diffusion of Modern Energy Technologies Africa has been found to be very low especially for solar energy systems. The installed solar PV capacity in Africa is a major issue of concern globally. This low trend in technology adoption is of interest because Africa enjoys some of the best solar radiation levels in the world averaging between 4 – 6 kWh/m2/day for most of the year. It was initially speculated that the low uptake of solar technology was associated with the continent’s high poverty levels and limitations in technical capacity as well as awareness; nevertheless, the introduction of Mobile Telephony Technology (MTT) has cast some doubt on those speculations due to the rapid assimilation and diffusion of the technology in several African countries. The paper elaborates on the approach taken by a successful MET business model known as the Lighting-up-a-village (LUAV), designed by an energy company, Barefoot Power (BFP), in Uganda. This model has been used to distribute micro solar home systems in rural Uganda and exhibited a rapid uptake rate that resulted in the establishment of 18 LUAV projects in a span of 12 months. Through the LUAV program, more than 3000 households took up the technology securing their own independent power generation hub. The success factors noted in the LUAV business model were identified and highlighted so as to present recommendations on the key factors that can possibly drive a rapid adoption of METs.
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Entrepreneurial capacity, government intervention and diffusion of technologies in Uganda: Comparing the supply side of modern types of energy and mobile telephony technologies

The diffusion of modern technologies plays a critical role in job creation. Mobile Telephony Technology (MTT) has been successfully diffused in Uganda, within a short time, and with minimal government intervention. However, despite heavy government interventions, Modern Energy Technology (MET) remains outside the reach of most Ugandans. Low access to MET seems to be contributing to Uganda’s under-development and unemployment. Projects initiated to spur MET diffusion haven’t been very successful, and METs widely used in other developing countries and successfully piloted in Uganda have found minimal diffusion and failed to up-scale. Although policy makers are quick to blame poverty and ignorance for the slow diffusion of MET, the rapid diffusion of MTT in similar environments have put to doubt most these arguments. This study explored the diffusion of technologies in Uganda, using entrepreneurial capacity as an independent variable. By comparing the fast diffusing MTT with the slow diffusing MET, this study helps to provide a better understanding of the dynamics of technology diffusion in Uganda. Using government documents and a questionnaire survey targeting employees of MTT and MET vending firms, the study identifies differences in intervention related to governance, regulation and funding between MTT and MET vendors, which significantly affect some aspects of Entrepreneurial capacity. The study also found evidence of significant differences in the constructs of Entrepreneurial Capacity measured for MET and MTT vending firms that affect technology diffusion.
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Models for conductor size selection in single wire earth return distribution networks

The use of the ground as the current return path often presents planning and operational challenges in power distribution networks. This study presents optimization-based models for the optimal selection of conductor sizes in Single Wire Earth Return (SWER) power distribution networks. By using mixed integer non-linear programming (MINLP), models are developed for both branch-wise and primary-lateral feeder selections from a discrete set of overhead conductor sizes. The models are based on a mathematical formulation of the SWER line, where the objective function is to minimize fixed and variable costs subject to constraints specific to SWER power flow. Load growth over different time periods is considered. The practical application is tested using a case study extracted from an existing SWER distribution line in Namibia. The results were consistent for different network operating scenarios.
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Wood Gasification in Uganda – Is this a solution for the Energy Crisis? Hard facts from installed units

Abstract
There is urgent need to increase Uganda’s electricity supply and more importantly reduce the country’s dependence on the presently meager hydro electric power generation. Uganda is a growing economy with an average GDP growth rate estimated at 6.4% per annum. Economic growth is matched by growth in energy demands; fortunately we have a number of options at our disposal. Of interest to the country is harnessing electricity from biomass. In small scale this can be done by gasification of the biomass. There are already some players in this sector of energy in Uganda. Musizi Tea Estate/James Finlay Uganda Limited has a 205 kW wood gasification unit. Yet another small unit belongs to Kasenge Electricity Power owned by a retired British civil engineer, Brian Frawley. A 10 kW unit generates electricity by wood gasification. Nonetheless gasification is a complex process when compared with diesel genset electricity generation, maintenance is rather intensive. High level engineering and technical skills are require on a full time basis. This is lacking at the moment. In addition, the fuel supply chain has to be sustainable and it may require some added costs and organization, etc. In an attempt to address these constraints CREEC, Centre for Research in Energy and Energy Conservation has developed a program to work with these pioneers to sustain the units and make viable the technology. It is also exploring alternative fuels such as agricultural residues. This paper presents experiences from the use of gasification to meet small scale electricity generation using this technology and proposes some strategies for small scale gasification systems implementation.
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Using renewable energy in a sustainable and holistic manner as a tool to eradicate rural poverty in Africa

Abstract
Rural poverty in developing countries is a social problem that is well recognized and causes concern globally. The UN recently met to review the MDG’s and acknowledge that there was limited progress to date; a looming target date have highlighted the difficulty in addressing development issues on the ground where people are trying to survive, often on as little as $2 per day or less. This paper demonstrates the model of rural village energy services centres by using solar energy to provide solution to most of the problems of a typical African rural village. This stand alone system provides energy services solution leveraging sustainable resources in a holistic, community-integrated fashion to improve health, information, communication, education and preserving the environment while it kick-starts micro-economies in rural villages. It intends to increase productivity and ultimately eradicate poverty. This solution is still in a prototype stage but has its special interest because it hopes to provide clean water and biogas apart from the solar generated electricity. Through the implementation of community energy services, stand alone decentralised solutions intend to divert rural current expenditure on kerosene, offering significant reductions in carbon emissions, environmental damage and respiratory-illness related deaths which were recently estimated at 1.6M per annum worldwide as per a World Bank report. This corresponding increase in energy efficiency drives an increase in productivity and thus a step closer to the realization of the MDGs as has been documented in various case studies (Annual Report 2008 (. (2008). Renewable Energy Services for Developing Countries – In Support of the Millenium Development Goals) [8]. This paper covers the technology implementation starting from demand until it reaches the level of success which then makes it suitable for replication.
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