http://erepository.uonbi.ac.ke/handle/11295/82046 Mon, 18 May 2026 20:39:39 GMT 2026-05-18T20:39:39Z http://erepository.uonbi.ac.ke/handle/11295/163902 Iron and Manganese Alginate for Rechargeable Battery Electrodes Kiriinya, Lindah K; Kwakernaak, Markus C; Akker, Simone Van den; Verbist, Guy L M M; Picken, Stephen J; Kelder, Erik M We present a sustainable, inherently safe battery chemistry that is based on widely available and cheap materials, that is, iron and manganese hosted in alginate bio-material known from the food and medical industry. The resulting battery can be recycled to allow circularity. The electrodes were synthesised by the alginate caging the multi-valent metals to form a hydrogel in an aqueous environment. Characterisation includes FTIR, XPS and Mössbauer spectroscopy. The electrochemical performance of the electrodes was investigated by performing cyclic voltammetry (CV) and (dis)charge experiments. Mn and Fe ions show good co-ordination with the alginic acid with higher oxidation states demonstrating complex bonding behaviour. The non-optimised iron and manganese alginate electrodes already exhibit a cycling efficiency of 98% and 69%, respectively. This work shows that Fe and Mn atomically disperse in a bio-based host material and can act as electrodes in an aqueous battery chemistry. While demonstrated at cell level, it is furthermore explained how these materials can form the basis for a (semi-solid) flow cell. Sun, 01 Jan 2023 00:00:00 GMT http://erepository.uonbi.ac.ke/handle/11295/163902 2023-01-01T00:00:00Z http://erepository.uonbi.ac.ke/handle/11295/155742 A Webgis Based Vehicle Parking Management System: Case Study of Upper Hill, Nairobi Mwongela, Dominic M In an effort to address challenges that face urban transportation, technological innovations that put cities towards sustainable smart cities are imperative. Nairobi County faces enormous challenges in offering efficient parking services to its residents. Some of these challenges include lack of information on available parking lots and also the most convenient routes to navigate to those lots. To solve these problems, technology reviews of implemented systems across the globe needed be carried out. Potential application of GIS in car parking solutions was studied in detail. Present systems were found from documented literature to be majorly focused on Internet of Things (IoT) with few systems having included capabilities of GIS in their implementation. The gaps inherent in the present systems were identified and incorporated in the design of a vehicle management system that not only looks at the bird’s eye view of the parking lots, but also focuses on the spatial location of the individual parking lots to incorporate user preferences. This study concludes that, utilizing GIS analytical and visualization capabilities will help drivers locate individual preferred parking lots easily and navigate to those lots. The study recommends implementation of a webGIS based vehicle parking management system that would be a market place for willing parking lots’ owners to have their parking lots put online for any user to access them and thereby generate revenue. Fri, 01 Jan 2021 00:00:00 GMT http://erepository.uonbi.ac.ke/handle/11295/155742 2021-01-01T00:00:00Z http://erepository.uonbi.ac.ke/handle/11295/154438 Factors Affecting Time and Cost Performance of Construction Projects in Rwanda. A Case Study of High-rise Building Projects in Kigali. Tuyishime, Pascal Highrise building projects are naturally complex due to the involvement of numerous parties from the project owner, professionals, consultants, contractors, stakeholders, suppliers and regulators. Most multistorey projects in Rwanda encounter problems and issues of performance such as extensive schedule and budget overruns. Any project success always rests on the performance which is proven by completion on time within the allocated budget and expected quality that is required by the users of the facility and satisfaction of the client. The research objectives were: To identify factors causing significant delays in Highrise building projects, to find out factors causing significant cost overrun in Highrise building projects and to propose strategy to minimize the causes leading to significant delay and cost overruns in high Highrise building projects. Questionnaires were distributed to professionals who were involved in the execution of in the execution of Highrise building projects. The number of these building projects were collected from Kigali Construction Urban Planning One Stop Center as this department is assigned the responsibility of approving or disapproving construction project plans before the execution phase starts to ensure that they compliance with regulations. Statistical Package for Social Science (SPSS) was used to analyze the collected data. The findings revealed that variations of design change , late payment to contractors, delay in decision making, delay in receiving clearances through customs for the imported materials, financial difficulties encountered by contractor are the main cause of time overrun in Highrise building while variation in the cost of construction materials, Frequent change in specifications and designs, inaccurate cost estimation , high cost of transport of construction materials and poor contact management were ranked as major cause of cost overrun. The recommendation of this study were: the funding of the project by client should always be adequate and be determined at the planning stage of the building project, The clear rules and regulations on evaluating contractors’ bids are needed and they should be used by clients and his agents in awarding contracts, The architects must select the most economical design for basic elements without compromising the quality and safety of the project such as foundations, structural frame, external cladding and roofing, Rwanda Institute of Architects (RIA) (Quantity Surveyors Chapter) should produce semi-annual journal containing cost data of construction materials in different locations of Rwanda because the techniques used to produce estimates vary according to the information available at the time of preparation. Wed, 01 Jan 2020 00:00:00 GMT http://erepository.uonbi.ac.ke/handle/11295/154438 2020-01-01T00:00:00Z http://erepository.uonbi.ac.ke/handle/11295/109228 Optimization of the Performance of a Hybrid Solardesiccant Dryer Mwiti, Frankline M A hybrid solar desiccant dryer (HSDD) was designed, developed and optimized with the aim of preconditioning the air for maize grain drying. The effect of four solar collector configurations in optimizing dryer performance was studied, comprising of (1) Radiation concentration lenses to increase solar radiation intensity and achieve high temperatures, (2) High density longitudinal finned elements for enhanced thermal contact and heat transfer rates, (3) Desiccant exhaust dehumidification conduits to enhance thermal recuperation of waste heat for regeneration into the dryer and (4) Combined effect of the three configurations. The collectors were tested and grain drying experiments performed on a loaded HSDD with the most efficient collector configuration and results compared with open sun drying method. Temperature changes of the solar collector configurations, heat transfer rates, collector efficiencies, grain drying rates and drying time were analysed. Moreover, the HSDD experimental moisture ratio data was fitted to 18 mathematical models of dying and regressed using MATLAB (Version R2016a) to evaluate goodness of fit by comparing coefficient of determination (R2), sum of square error (SSE) and root mean square error (RMSE). Results showed that collector configuration with finned elements, desiccant exhaust air regeneration conduits and radiation concentration lenses had average temperature change of 8°C, 17°C and 21°C above ambient respectively; while the combined collector had the highest average temperature change of 28°C. Similarly, changes in relative humidity were 6%, 16%, 19% and 25% for finned elements surfaces, desiccant exhaust air regeneration, radiation concentration lenses and the combined collector respectively. Analysis of variance using Stratigraphic16.1 software showed statistically significant differences in temperature changes under different test configurations at 95% level of confidence. Moreover, multiple range tests indicated significant differences between the means of temperatures from the contrasted collector configurations. The temperature and relative humidity changes increased linearly, and the rate of change was highest in the combined configuration and least in finned elements. Thermal efficiency increased with temperature changes as well as with useful heat gain and solar insolation. Useful heat gain increased to reach the maximum average values of 0.104 kJs, 0.19 kJs, 0.244 kJs and 0.289 kJs for the finned elements, desiccant exhaust air regeneration, radiation concentration lenses and the combined configurations respectively at maximum solar insolation time (13.30hrs). The average collector efficiencies were 17%, 36%, 45%, and 61% for the finned elements, desiccant exhaust air regeneration, radiation concentration lenses, and the combined collector configuration respectively. The integrated collector configuration improved thermal efficiency from individual configurations by 44%, 25% and 16% for the longitudinal finned elements, desiccant exhaust air regeneration and radiation concentration lenses alone respectively. The combined collector set up had lowest heat loss coefficient (7.1528) while the collector with radiation concentration lenses only manifested the highest value (12.336) despite achieving high temperatures than finned elements surfaces (10.008) and desiccant exhaust regeneration (9.0295). The HSDD achieved maize grain drying from 24.1% to 13.1% M.C (w.b) in 18 hours compared to 54 hours for open air sun drying method. Moisture removal rate increased from 0.162 kg/hr to 0.485kg/hr while the drying time was reduced by 67% using HSDD. Regressed moisture ratio datasets of the eighteen fitted mathematical models reviewed that the Two term model characterised the drying kinetics of maize grain in the HSDD with highest R2 (0.9676) and lowest SSE (0.05655) and RMSE (0.04078) values. The performance of the dryer was optimised by incorporating radiation concentration lenses, longitudinal finned element surfaces and desiccants exhaust regeneration system to increase drying temperatures, heat transfer and waste heat recovery for subsequent drying. This study is useful in scaling-up dryer design and prediction of tempering effects during conditioning of grain in planned drying schedules. It optimizes drying process parameters for improved dryer performance and efficiency enhancement to reduce time loss and possible grain damage during drying to benefit grain and seed industry for sustainable food security. Keywords: Solar collector, Grain dryer, Finned element, Exhaust regeneration, Desiccant, Radiation concentration lenses, Drying rate, Drying kinetics. Tue, 01 Jan 2019 00:00:00 GMT http://erepository.uonbi.ac.ke/handle/11295/109228 2019-01-01T00:00:00Z