Browsing by Author "Alemayehu, Worku"

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    Assessment of Surface Water Potential to Manage Frequent Drought Disaster (A Case of Dhas District in Borana Zone of Oromia Region, Ethiopia)
    (Addis Ababa University, 2019-06) Alemayehu, Worku; Daniel, Fikreselassie (PhD)
    The study was conducted in Dhas district, which is located in Borana Zone of Oromia region; geographically it is situated 4.00 o -4.39 o N and 38.39 o -39.46 o E with altitude range of 1082 – 1666m a.m.s.l. Total area of the district is 3,183.22km 2 ; its length from West to East is 120 Km and width from South to North is 41km. There is not any river and gauging station in the district; the study was conducted aiming at estimation of surface water potential of the district and evaluation of its sufficiency for managing of drought disaster in the district. The surface water potential assessment of the district was conducted using SCS model with the aid of remote sensing and GIS. The assessment output was contextualized with the study finding of Genale Dawa integrated Master plan study (Dhas district is located in Dawa sub-basin; finding from separate analysis of Dawa sub-basin was referred). For the recent land use/ land cover information of Dhas district; satellite images were downloaded from USGS (United States Geological Survey) website with acquisition dates of December 2018, and the image processing was done using ERDAS Imagine 2015. With the aid of HEC-GeoHMS tool that is specifically designed in the ArcGIS environment to process geospatial data, the curve number was generated using the required information (hydrologic soil group, DEM, LULC map). The district was divided in to twelve sub-watersheds using Global mapped software, and direct runoff estimation was done for each sub-watershed separately; the summation of direct runoff from each sub-watershed was made to get the total direct runoff amount of the district. Thirty years daily grid rainfall data that was collected from NMA was used for the estimation of the direct runoff. Estimation of runoff volume was computed for all thirty years period, and the estimated minimum and maximum runoff volume were found to be 8Mm 3 and 361Mm 3 respectively. Twenty years of forecast was made to estimate the major requirements in the district. Human and livestock’s water requirement estimation based on the population sized of 2039 was computed to be 10Mm 3 / year. The abundant of estimated runoff volume was evaluated, whether it is enough or not to satisfy the major water requirements in terms of managing the frequent drought disaster. As the analysis shows, Dhas district is having sufficient surface water potential that can be developed for managing of the frequent drought disaster in the district. This study was conducted focusing only on the available surface water potential of the district, and its sufficiency for managing of the drought disaster in the district. Its finding is also expected to be an entry point for development of the resource in the large scale. But for its implementation, it needs further feasibility and detail studies.
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    Experimental Analysis of Biogas Compression and Purification from Biogas Digester: A Case Study at Sidist Killo Campus
    (Addis Ababa University, 2019-07) Alemayehu, Worku; Wondwossen, Bogale (PhD)
    The study encourages a way to recover energy from food wastes with the objective of producing clean biogas fuel (methane) from a food waste by using anaerobic digestion (biological decomposition). This waste to fuels technology reduces the amount of waste to be sent to the living areas, recovers energy from bio waste, helps to generate income from the selling of the produced biogas fuel (methane) and solves the energy problems. This thesis assesses the compression and purification of biogas mainly methane through anaerobic digestion, using a 10m 3 digester installed at Sidist killo campus. Biogas which is a clean and environmental friendly fuel emerged as one of the potential alternative fuels. Raw biogas contains about 60-70% methane (CH4), 30-40% carbon dioxide (CO2), traces of hydrogen sulfide (H2S) and fractions of water vapors. But its wide spread use is disadvantaged by the associated problems like low energy density due to the presence of impurities, generation at low pressures and the absence of means for storing and transporting. Biogas is widely used for cooking and lighting, but its commercial use has not been realized due to difficulties in its storage and transportation. This work intends to establish a facility at the site of biogas production in the sidist killo campus for purifying, compressing, bottling and making it transportable. Solution identified to the problem is to increase the energy density of the gas through removal of incombustible and corrosive gas and consequent compression which is experimented on this paper. This paper presents all the results of removal of impurities of biogas which are mainly carbon dioxide gas, hydrogen sulphide and water from biogas using reasonable chemicals selected. Sodium hydroxide, activated carbon powder and silica gel are chemicals selected to remove carbon dioxide, hydrogen sulphide and moisture respectively from the raw biogas. Experimental results are evaluated by ever-changing the amount of chemical used from 0 up to 10 gm. As a result, the purity of biogas increases with increasing the amount of chemicals. The gas purified after the scrubbing unit constitutes 61% of methane which is in the acceptable range of methane content in the biogas. Further, compression of biogas was carried out by a commercial compressor and stored into a 500lt biogas bag and tire inner tube at a pressure of 2 and 1 bar respectively. And finally the stored biogas is bottled in to 2lt commercial gas cylinder using modified cycle pump at a pressure of 5 to 8 bar which a normal person can exert