Center for Energy Technology

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Analysis & Development of Solid Waste Management System of Addis Ababa
(Addis Ababa University, 2002-01) Belete, Zerayakob; Kitaw, Daniel(phd)
Solid waste, which is a consequence of day-to-day activity of human kind, needs to be managed properly. Addis Ababa like other cities in developing countries, faces problems associated with poorly managed waste collection operation. This thesis deals with the city’s current solid waste management problems, collection and disposal. The city’s refuse collection operation is modeled using queuing/simulation model. Spreadsheet Monte Carlo simulation technique is used to simulate the collection activities of the vehicles. In a similar manner, the average waite time of the customer( unit volume of waste) is also simulated. The result obtained shows that the collection operation is affected by the relative location of zonal centroid with reference Repi landfill site. Based on the simulation result, vehicle performance in collection operation is also evaluated. The number of vehicles that are required to carry out the operation has been calculated. In regard to solid waste disposal, alternative models are evaluated to meet the city’s disposal need. Land filling with other disposal options is found to be better alternative. The four proposed landfill sites are modeled using linear programming technique for optimized collection/disposal operation. Energy recovery potentials of various disposal options like landfill, incineration and anaerobic digestion have been assessed. Material recovery potential of the city’s refuse is also evaluated for reprocessing. Better solid waste management option is also proposed.
Performance of Ethanol Water Mixture as Fuel for Household Stove
(Addis Ababa University, 2011-11) Tekle, Atakelti; Alemu, Demiss (PhD)
Ethiopia is one of the world’s least developed countries where population pressures and an over reliance on traditional biomass fuels have led to deforestation. The combustion of unsustainably harvested biomass releases large quantities of greenhouse gases into the atmosphere and when burnt indoors has been strongly linked to acute respiratory infections and a major cause of death in developing countries. In order to protect the environment, it is urgently required to substitute the utilization of firewood for cooking purposes. Ethanolwater mixture oil, as one of the best solutions, is a promising alternative energy source offering a variety of economical and ecological advantages. A new pressurized cooking stove was developed according to the principles of the appropriate technology that can be operated on ethanol-water mixture. According to the chemical, physical and combustion properties of fuel oil, a new nozzle socket, a new burner head and a new tank as well as a hand pump device were designed and manufactured. The stove was evaluated by varying ethanol concentration by water boiling test and also was evaluated against wheel brand stove, a typical example of an adapted kerosene stove. The procedure followed for the test is in accordance with the standard test methods recommended by Volunteers in Technical Assistance (VITA). A pressurized-ethanol stove running on 40 % (w/w) ethanol concentration (40% ethanol and 60% water) has been developed. Based on one litre boil of water, it showed no significant difference in performance; its efficiency as high as 29.5% as compared to 33% with that of conventional kerosene stove was observed. However, the pressurized-ethanol stove had advantages over kerosene in that it produced smokeless burning and no irritating smells. Thus, the prototype stove was found to be potentially appropriate for use.
Characterization and Optimization of Biodiesel Production From Mexican Poppy (Argemone Mexicana)
(Addis Ababa University, 2012) Tsega, Metshet; Kiros, Snolomon (PhD)
Biodiesel production has generated heated debate on energy security for food crisis. This debate has changed the direction of biodiesel research into the use of non-edible oil sources referred to as second generation biodiesel feedstock. Ethiopia despite having high potential of various non-edible oily plant species, only very few non edible sources of biodiesel are known compared to the number of non-edible oily plant species identified. Thus, exploration of cheap and non-edible sources of biodiesel such as Argemone Mexicana can help to increase the production and use of biodiesel. This plant has invaded many ecosystems and communities in Ethiopia. However, due to lack of research and skill, there was a gap to find optimum conditions and properties of newly identified non-edible oil plant of oil methyl ester. Therefore, the objectives of the present study was to find a way of converting this invasive plant to useable form for the society which was affected by A. Mexicana by converting the seed oil to biodiesel production, characterization of the oil and fatty acid methyl ester (FAME). After the seed samples were collected and purified, the physicochemical and instrumental parameters were determined. The biodiesel was produced by heterogeneous CaO catalyst from A. mexicana oil through transesterification method. Experimental design using design expert 7.0.0 software were implemented to identify the oil yield, the effects of different process parameters for FAME production and to find the optimum conditions to maximize the yield of FAME. A total of 40 % yield of oil was extracted and converted into methyl ester by the process of transesterification. The physicochemical studies and the comparisons revealed that transesterification improved the important fuel properties. The best performance result was obtained at a catalyst concentration of 1.0%, molar ratio 9:1 and reaction time of 1 hr, while the reaction temperature and agitation speed was set at 600C and 600 rpm. The FAME yield obtained from transesterification process ranged from 56.3 to 91.2% while the optimum result was found 93% from the design expert software. The results showed that transesterification improved the important fuel properties testes which were relatively closer value with the ASTM and EN standards. Key words: Biodiesel production, Argemone Mexican , transesterification, FAME
Application of Solar-Wind Hybrid for Water Lifting (in Borena Zone, Oromia Region)
(Addis Ababa University, 2012-02) Melkamu, Ibsa; Edessa, Dribssa (PhD)
Water is the primary source of life for mankind and one of the most basic necessities for rural development. The rural demand for water for crop irrigation and domestic water supplies is increasing. At the same time, rainfall is decreasing in many arid countries, so surface water is becoming scarce. Groundwater seems to be the only alternative to this dilemma, but the groundwater table is also decreasing, which makes traditional hand pumping and bucketing difficult. As these trends continue, mechanized water pumping will become the only reliable alternative for lifting water from the ground. Diesel, gasoline, and kerosene pumps have traditionally been used to pump water. However, the non-renewable energy is on the way of depleting from the world and due to this cost of the oils are increasing from time to time, in addition to these the exhausting gases from them is polluting the environment. So due to the cost of the oils, the developing country such as Ethiopia may not able to buy to generate water from the ground for the people and livestock. Since our country is reach in renewable energy, it is the must to replace for generation of power to the renewable one such as solar energy, wind energy, and others. Currently, hybrids of PV and wind with or without backup generators are more promising for supplying uninterrupted power because they work independently of each other. Such systems do not require each component to be oversized. For the Semento kebele, Liban woreda, which has the problem of drinking water for the people and livestock the solar-wind hybrid system with the specification 270kw PV, 11BWC Excel-s, 110kw inverter, Total net present cost (NPC) $1,305,958, levelized cost of energy (COE) $0.458/kwh, and operating cost $47,179/yr is selected after optimizing by using the HOMER software. The demand of water for the site is 2200m3/d and this is easily fulfilled by installing two systems for the kebele. From the installed hybrid system there is excess electrical power which is used for the lighting purpose by using battery and there is also excess water which we use it for the irrigation purpose. So even if our aim is to solve the problem of drinking water there is also problems that are solved with the system.
Comparative Analysis of Briquetting Most Viable Biomass Waste to Substitute Charcoal in Ethiopia
(Addis Ababa University, 2014-04) Belay, Anteneh; Alemu, Demiss(PhD)
Agricultural residues seem to be the most promising energy resources for developing countries. However, the majority of them have low energy density. One of the favorable technologies for enhancing that property is charcoal Briquetting. A large amount of agricultural and solid wastes are left in the field after harvest. The primary objective of the study was to investigate the comparative analysis of resource availability, physico-chemical properties and performance of biomass charcoal produce from the most promising wastes. Specific objective were to develop and characterizing composite charcoal briquettes, investigate factors affecting densification of composite charcoal briquettes and compare resources availability, physic-chemical property and performance of charcoal briquettes with wood charcoal. The composite charcoal briquettes were produced using ASTM standard by a combination of process factors. The three process factors were dwell time, clay binder ratio and pressure. Design expert software, Box-Henken model were employed to investigate the effect of process factors. The Density was found in the range of 783.00-1,187.00 kg/m^3. The coefficient of multiple determinations for prediction of the proposed density model was about 95.7%. The effect of the three variables against density was investigated. When every two combinations of the above variables were increased, density of briquettes was also found to increase. Optimum point of dwell time, pressure and clay binder concentration was found at 3.6 minute, 45 bars and 18.27% respectively. The optimal point was validated. The Production of 1300 tones/yr briquettes plant was evaluated. The total investment cost was found to be 1.9137milloion birr. The net present value and the internal rate of return of the project were 2,753,976 Birr and 19% respectively it implies the project was feasible. Base on the resource estimation using production to residue ratio, the quantity of available agricultural residue, cotton stalk, coffee husk, bamboo residue and jatropha press cake in Ethiopia was approximately 4,655.887, 219.933, 109.757, 109.757,1,000 and 0.228Ktones/yr respectively. When the fixed carbon of charcoal made from bamboo, cotton stalk, coffee residue and composite with that of Acacia charcoal, 60.85, 58.4, 63.9, 68.25 and 69.74w/w % were found respectively. The above value all had relatively similar which makes it possible to substitute wood charcoal. Regarding heating values of briquettes produced from bamboo, cotton Comparative Analysis of Briquetting Most Viable Biomass Waste to Substitute Charcoal in Ethiopia AAU, AAiT, M.Sc. Thesis by Anteneh B. xiv stalk, coffee residue, composite and Acacia spp. charcoal were 29135.94KJ/Kg, 19209.03KJ/Kg, 11710.48KJ/Kg , 23446.08KJ/Kg and 32573.304 KJ/Kg respectively. But all the heat values of briquettes were lower than that of charcoal. If the country substitutes wood charcoal by charcoal briquettes, it will reduce 47.06 CH4 / year and 1530.383 Co2/year for every production of 1300 tons per year. The study showed that charcoal from bamboo; cotton stalk, coffee residue and agricultural residue could be used as substitutes for Acacia charcoal as they had comparable potential energy. But jatropha press cake currently had a low possibility to be use in our scenario. Generally, this research concludes that the biomass charcoal had positive value of production method, fixed carbon and performance, but one negative value was obtained from calorific value. With ¾ positive values, these biomass wastes can substitute wood charcoal in Ethiopia.
Prediction of Performance Parameters and Determination of Aerodynamic Characteristics of Wind Turbine Airfoil Using CFD Modeling:
(Addis Ababa University, 2014-08) Merid, Million; Assefa, Abebayehu (PhD)
In the current situation of global energy crisis, generation of energy derived from renewable energy resource has grown a significant attention. Wind energy is a very interesting due to the fact that fuel is free of cost. The most important aspect of wind energy technology is the wind turbine and its aerodynamic characteristics of the airfoil forming the blade. Thus predicting the performance parameters and determining aerodynamic characteristics of airfoil section are important. However, this requires continued experimental wind tunnel test and validation tools such as computational fluid dynamics (CFD). The primary objective of this study was learning the CFD software and its applications. Secondly, this study was focused on predicting aerodynamic characteristics of an airfoil for varying angles of attack (AOAs). Simulation was done to deduce aerodynamic parameters (lift, drag, lift to drag ratio, contour plot of velocity and pressure distribution over the airfoil section). This can reduce dependence on wind tunnel testing. The simulation was done on airflow over a two – dimensional NACA 63-415 airfoil using FLUENT (version 6.3.26) at various angles of attack varied from -50 to 200 using two turbulence models (S-A and SST k- ω) with the aim of selecting the most suitable model. Domain discretization was carried out using structured quadrilateral grid generated with GAMBIT (version 2.3.16), the fluent pre-processing tool. Comparisons and validation were made with available experimental data for NACA 63-415 airfoil with numerical results. Accordingly, it was found that the two turbulence models achieved a reasonable and a good agreement in predicting the coefficients especially for angle of attacks prior to stall. Among the model, studied the most appropriate turbulence model for the simulations were the SST k- ω two equation models, which had good agreement with the experimental data than S-A one equation model. As a result, it was decided to use the SST k- ω turbulence model for the main analysis with acceptable deviations in results (9.028% for lift and 12.203 % for drag coefficients). This study concluded that CFD simulation provides sufficiently accurate results for a majority of AOAs. The discrepancy in calculating the lift and drag values comes from limitations in the turbulence model behavior. However, the majority of the lift and drag curves match the experimental data. Finally, this study includes simulation results of Adama I wind turbine airfoil section and predicted results was complied.
Adopting Building Integrated Photovoltaics (BIPV) for Harnessing Green Economy in Ethiopia: A Study on the Design, Modeling and Economic Analysis of Grid-Tied BIPV
(Addis Ababa University, 2015-01) Berhanu, Tsion; Assefa, Abebayehu (PhD)
Contrary to add-on Photovoltaics (PV), Building-integrated PV (BIPV) refers to the application of PV arrays where they are integral parts of the building envelope having the function of producing electricity as well. Ethiopia, as a country having average daily solar radiation of 5.2kWh/m2, can make use of this technology as a means of achieving the country’s goal of expanding electric power generation and green growth strategy. In addition, by producing power close to the point of use, the technology shall contribute to the reduction of the current 23% transmission and distribution losses encountered in the power system of the country. To this end, the opportunities of meeting some of the country’s electricity demand by introducing grid-tied BIPV in commercial and residential buildings of urban Ethiopia were investigated by taking the new Zemen Bank Headquarter 30-storey Building as a case study. A detailed design, simulation and economic analysis of a grid-tied BIPV system were conducted for four different scenarios of the building using PVsyst software. The results of the simulation showed that with an optimal design a significant amount of energy, 897,000kWh/year, which covers 69.54% of the estimated demand of the building can be generated. This can save up to 26,910USD per year based on the current electricity tariff of Ethiopia. The simulations of the four scenarios revealed that best results can be achieved by considering the system starting from the initial architectural design of the building rather than retrofitting an existing one. On the other hand, the economic evaluation resulted in an energy cost of US$0.11/kWh for the optimal design which is much higher than the prevailing electricity retail price of Ethiopia, US$0.03/kWh. From this it was concluded that grid-parity shall be achieved in the long run since the costs of PV modules is dropping while their efficiency is rising.
Feasibility Study of Off-Grid Hybrid Systems: Mini-Hydro, PV, and Wind Power Systems for Rural Electrification in Ethiopia (Study Area: Mojana Wodera District, North Shewa, Amhara Regional State, Ethiopia
(Addis Ababa University, 2015-03) Tesfa, Abraham; Bekele, Getachew(PhD)
Ethiopia is a country of about 85 million people. About 85%of its people are living in rural remote areas. Those rural areas are either inaccessible to the central grid system or not covered by grid extension to date. About 2% of these areas are accessible to electricity. Among those areas is Mojana Wedera District in Amhara Regional State; North Shoa zone. The study area in this district is called Asofe and Filagenet villages. The run-off river Ajana (Mugil Wahsha), which is the focus of this feasibility study, runs through these villages. The study site‟s location is 9°53'17.62"N and 30° 34'11.41"E. The people in these villages live both is highland and semi lowland with the attitude ranging from 2,860 to 2,400m. Ajana River is a tributary of Jema river and Jema is in turn one of the main water feeders to Blue Nile. In Asofe and Filagenet, about 4,434 people live. The two villages have 739 households, two 1st to 8th grade schools having about 1000 students with 20 teachers in each school, five flour mills (assumed), two milk processors (assumed), two health posts and five churches. Though this area is rich in economically harnessable renewable energy sources, the people are not benefited from these resources. Among those resources which are not yet exploited are: Small-hydro, Wind and Solar. Without electricity, modern life is unthinkable to these societies. This feasibility study focuses on hybrid off-grid renewable potentials of Small-Hydropower, Wind and Solar Photovoltaic (PV) with battery backup and Diesel generator to supply the community with continuous electricity for twenty four hours. HOMER software is used for simulation, optimization and sensitivity analysis of the hybrid system. Given all the necessary inputs to the software, the results showed a list of feasible hybrid electric supply systems sorted out in accordance to their total present cost (NPC) in ascending order. Cost of energy (COE in $/kW), penetration level into the renewable resources (renewable fraction), the amount of Diesel oil used by the generator per year and the generator‟s working hour per year are also shown in the result list. In addition, a sensibility analysis is carried out for the major sensitivity components of the hybrid system. The major sensitivity components of the system recognized are the changing price of solar panel and wind turbine against increasing Diesel oil price. From the sensitivity result, solar ii energy is not promising in the study area. But, wind turbine is the most promising resource and can easily be utilized. Using the same software, the optimal costs of the hybrid system result is compared with the cost of grid extension to these villages are computed. The electricity, produced from this hybrid system will replace the conventional energy sources like wood, animal dung and kerosene. Besides, it brings work and technology opportunities linked to the electrical availability which transforms peoples‟ life style and gives its contribution to the development of the country. Keywords: Small Hydropower Potential; Wind Energy Potential; Solar Energy Potential; Hybrid; Primary Load; Deferrable Load; Un-gauged Run-Off River, Net Present Cost(NPC).
An Investigation of Integrated Reservoir and Power System Operation, an Optimal Dispatch of the Ethiopian Electric Power System
(Addis Ababa University, 2015-06) Ashenafi, Alemu; Solomon, Abebe (PhD)
Ethiopian Electric Utility (which is born from EEPCo) has been running a Load Dispatch Center (LDC), which is tasked with the responsibility of an optimal power dispatch from an operational point of view. However, to date most operational decisions (including reservoir management) are done manually. Under such circumstance, integrated reservoir management and power system dispatch become more challenging as more and more plants with different technologies are to be added in coming years. Thus, it is very important to perform high resolution system dispatch to identify short term challenges, opportunities and potential solutions. This study was performed using two parallel, linear optimization, models that have been developed using MATLAB optimization toolbox. The first one, which is termed as energy model, deals with year round reservoir operations subject to the energy requirement of the power grid. This model has 73 time steps, with each time step representing a block of successive five days. The second one uses the output of the former model to test the hourly power balance and hourly reserve needs subject to the requirements of hourly water balance in reservoir and power systems operation over the selected days. The second model has 120 time steps, with each time step representing an hour. The result for the reference scenario shows that hydropower contributes significant amount of energy (approximately 90%) to meet 2017’s annual demand at least cost. It also indicates that this could be achieved while maintaining steady state reservoir level and fulfilling the power reserve requirement. However, vulnerability related to heavy reliance on hydropower puts the power grid at significant risk that would lead to high cost of electricity due to shortage of water during dry year and high demand conditions. It was also shown that 3 GW capacity of GERD power plant should be available at the beginning of 2017 in order to avoid high cost of electricity generation and unserved energy that could occur if the construction is delayed. The result shows that depending on scenarios’ the increase in cost of electricity, including cost of unserved energy, was approximately 6.3 to 8.75 fold the cost at the reference scenario. The major causes of this cost increase are the direct cost related to the use of more expensive electricity generators, and the indirect cost due to unserved energy (lost GDP per kWh). In short, it is concluded that integrated reservoir and power system operation leads to efficient resource utilization (Especially water and power system infrastructure), which should be given due attention during hydropower power resources development and operation. Future mitigation of the observed vulnerability should look into the following four solutions. These are: (i) implementing an optimal integrated operation; (ii) emphasizing the use of diverse generation resources; (iii) implementing strategies that enhance water inflows to reservoirs; (iv) designing power plants with higher capacity factors.
Simulation, Modeling and Control of Distributed Hybrid Generation System
(Addis Ababa University, 2015-06) Shikur, Mohammed; Dama, Tesfaye(PhD)
An autonomous decentralized distributed generation hybrid system supplies electricity to the user load both in grid tied or standalone modes. This kind of decentralized system is frequently located in remote and inaccessible areas. It is essential for about one third of the world populations who are living in undeveloped or isolated regions and have no access to utility grid. Most people live in remote and rural areas, with low population density, lacking even the basic infrastructure. The grid extension to these locations might not be cost effective option and sometimes technically not feasible even. This decentralized energy generation system is essential for countries which has low installed capacity. The purpose of this thesis is modeling, simulation and control of a grid ties hybrid power system. It couples wind turbines, photovoltaic generators (PV), alkaline water electrolyser, a storage gas tank, fuel cell (SOFC) to give different system topologies. The system is intended to be an environmentally friendly solution since it tries maximizing the use of a renewable energy source. Besides the grid, electricity is produced by a both wind turbines and PV generators to meet the requirements of user load. During periods of low solar radiation, wind speed and also when the grid system is disconnected because of some reason, the fuel cell stack serves as standby to supply the load required by users. Different methodologies have been applied to address each objective of this study. Matlab Simulink software is used for the modeling and simulation of the hybrid system. Data were collected for the case study area in order to perform the optimization and financial analysis for the case study area using the Homer optimization software. Based on the dynamic component models, a simulation model for the proposed hybrid wind/PV/FC energy system has been developed successfully using MATLAB/Simulink. In the conclusion of this work the most optimum hybrid system is selected for the case study area from the output of Homer hybrid optimization software and comparison of the cost between the optimum homer output with that of the grid extension to the case study area is done.
Wind Energy Resource Analysis: A Case Study of Aysha Wind Farm
(Addis Ababa University, 2015-10) Wudu, Mengesha; Assefa, Abebayehu (PhD)
Ethiopia satisfied 92 % of its energy demand using biomass sources while petroleum and electricity (hydropower) only contribute 7 % and 1 %, respectively, in 2009. Due to this limited electricity availability, among the total population only 23.3 % had access to electricity and among 82.7 % of Ethiopians living in rural areas only 2 % in 2011. In addition 99 % of the electricity production is from hydropower source which is highly vulnerable to fluctuations in energy supply due to varying water inflow to reservoirs. However, the country is well endowed with other renewable energy resources (solar, wind and geothermal) that can be used to develop electricity. Among these resources, harnessing Ethiopian wind energy potential (10,000 MW) is a promising solution as it offers better generation mix and seasonal complementarity to avoid vulnerabilities associated with hydropower. It also helps in improving the life of population who are unlikely to have access to electricity supply in foreseeable future. Accordingly, this study is conducted at Aysha Wind Farm with the aim to analyze its wind energy resource based on 10 minute mean data for the year 2008 G.C. Using different software and statistical model, the wind data has been analyzed to: select wind turbine class, power density & estimate farm AEP, develop site wind resource map and perform preliminary turbine micro-sitting. Based on the analysis and site survey, site roughness and wind shear exponent are also determined. Detail wind energy resource study is performed for the site using MS Excel, MATLAB and WAsP software. Analyzing a wind-mast data at a height of 10 m using MATLAB and MS Excel, mean wind speed of 8.455 m/s and average power density of 571 W/m2 have been found at the farm. To take the effect of the roughness of the site in to consideration, a wind resource map of 28.44 km x 36 km area is performed on the site. This is done based on two nominated wind turbines namely: Sany SE8220III 2 MW and Gamesa G80 2 MW at respective hub heights of 70 m and 67 m using WAsP software. Considering the nearby transmission line capacity i.e., 300 MW, 150 sets of each type of turbine has been put at the farm, analyzed and compared to each other. Accordingly, Gamesa G80 2 MW is selected for its least wind farm cost of 0.0193 USD per kWh. As per the preliminary analysis of the farm based on the selected turbine, total gross AEP of 1819.21 GWh and total net AEP of 1183.62 GWh (after considering total loss factor of 0.651 on the total gross AEP) have been found. In addition the average power density and CF at the wind farm are estimated at 1392.6 W/m2 and 44.92 %, respectively. Moreover the mean wind speed at hub height (67 m) is 11.83 m/s whereas the average Weibull shape factor (k) and scale factor (A) are estimated at 3.13 and 13.22 m/s, respectively. In conclusion, according to the wind power classes, Aysha wind farm is categorized as class 7 (excellent wind energy resource) which is promising to construct large wind farm. It is, therefore, recommended that Ethiopian government consider investing on Aysha wind farm as the farm has an excellent wind resource potential at a capacity of 300 MW. KEYWORDS: Wind Farm, Wind Climate, Energy Production, Wind Resource, Wind Shear Exponent, WAsP, Wind-Mast, Capacity Factor, Ethiopia, Power Density, Wind Turbines
Wind Resource Data Analysis for Mosoboharena Wind Farm
(Addis Ababa University, 2015-10) Abdella, Mezid; Assefa, Abebayehu (PhD)
Ethiopia has been relied much on hydroelectric plants for of its power demand. But Hydro power is exposed to the effects of climatic change. Problem of water level fluctuation is increasing continuously in most of the hydropower dams resulting from the climate change. As the demand for safe and clean electricity increases due to industrial development and population growth in the country, expanding wind energy industry is greatly helpful to Ethiopia to meet its growing massive energy demand and to promote sustainable development. The country has enormous potential to generate electricity from wind. This study investigates the wind energy resource potential for Mosobo-Harena using different statistical methods and software. MS-Excel and MATLAB programs were used to generate time-series graphs of wind speed and direction , frequency distributions of wind speeds (wind speed histogram) and a wind rose for 12 continuous months from January 1/2007 to December 31/ 2007. And WAsP (The Wind Atlas Analysis and Application Program) was used for predicting wind resources, wind atlas generation, develop site wind resource map, identify wind potential sites, sitting of wind turbines and estimating farm annual energy production (AEP). The analysis was conducted based on one year 10 minutes interval wind speed collected data from mast at Mosobo-Harena at heights of 10m and 40m above ground level. This site has an average wind speed of 5.47 m/s and annual wind power density is 161w/m2 at mast height of 10m. The digital map of the study area was prepared by digital map generating software called Global Mapper considering an area of 20km by 20 km. Grid resource map for the wind farm was generated at some standard heights of 10m, 40m, 60m, 80m and 100m. Then from these standard heights, the hub height of the turbine was decided to be 60m for this project. And thus wind turbine Vestas V60-850kw was selected from WAsP documentation catalogue. The proposed wind farm has 72 turbines. At the selected turbine hub height of 60m, the annual mean wind speed and wind power density of the farm are 6.79m/s and 316W/m2 respectively, this is categorized as IEC class-III wind resource at this height. And the farm installed capacity is 61.8 MW, the net farm AEP is estimated to be 201686.7 MWhr and the average capacity factor was calculated to be 37.6%.
Design and Simulation of Grid-Tied Photovoltaic, Thermal and Biogas Energy Generating Systems to Power Universities in Ethiopia :A Case of Addis Ababa University , Collage of Natural and Computational Science.
(Addis Ababa University, 2015-12) Abiti, Gezahegn; Assefa, Abebayehu (PhD)
This paper confers with a study and unfold to systematic know how on how to furnish Ethiopian universities with power using their own abundantly available renewable energy resources and to establish a project for the same purpose. In pursuance of that, it was conducted by collecting and analyzing relevant and required data like electrical energy consumption, weather and site of the targeted universities while also rendering comprehensive attention to other design standards as well as specifications of machineries. The worst case design is thoroughly regarded herein the design section for it is more convincing with respect factor of safety in the event solar radiation falls below the annual average and when there is a minimum amount of biogas resource. The simulation, optimization and sensitivity analysis of the project is dealt by renewable energy tools of HOMER software. Foundation of the hybrid energy generating system is surfaced and actualized by making estimation of solar and biogas resource at a given site. The source data for AAUCNCSc revealed that a mean incident solar radiation of 3.66 kWh/m2/day and a potential of about 24 tons of biogas resource per a day can be collected considering safety factor for the variation as per day to day and month to month basis. The data collected for this study further showed that the electrical energy demand of the site was 104,870 kWh in the design year (July 2012) in which a combination of the two systems are going to offset the necessity. The assessment conducted revealed that out of the total of 104,870 kWh energy needed close to 81% is furnished by and fulfilled with biogas energy generating system while the remaining 19% of it is contributed by PV/T system and yet 0.00492kWh/yr (0.00%) is found to be excess which ought to be sold to the national grid . Pursuant to the financial analysis of HOMER, given to designed HPV/TBS and within an optimum cost of electricity (COE) of 0.263 $/kWh, renewable fraction (RF) of 1 can be obtained. Generally, if and when the total cost of PV/T modules, the Biogas generators and the converter are US$ 535,750.00, US$ 50,000.00 and US$ 8,000.00 respectively. The software further showed that in the emission analysis 4,172,041kg/yr of CO2, 18,099 kg/yr SO2 and 7,935 NO can be removed if this renewable design of the hybrid system is to be implanted instead of non renewable equivalent.
Integration of Solar Thermal System for Improved Energy Consumption in Low Temperature Industrial Processes, Case: Harar Brewery.
(Addis Ababa University, 2016-05) G/Hawariat, Ashenafi; Assefa, Abebayehu (PhD)
The objectives of this paper are to analyze thermal energy production of heat pipe evacuated tubes solar collector and investigate the integration of solar thermal system with conventional system in low-temperature industrial processes in Harar Brewery Factory. In this study, Matlab program and RET Screen software were implemented to identify technical and financial feasibility of the system. Six low temperature processes, such as feed water pre-heating, kegging, CIP, Mashing at 780C, bottle cleaning and mashing at 520C were selected in the industry for integration of solar thermal system. The total annual conventional thermal energy consumption of the selected processes is 11,176.18MWthr. This covers 54.15% of the annual total thermal energy consumption in the industry from the chemical energy of fuel (20638.23MWthr). The solar thermal system of a single heat pipe evacuated tubes solar collector was analyzed. The maximum outlet water temperature is 800C for mass flow rate of 47.52 kg/hr through the manifold. However, the maximum outlet water temperature is 520C in mashing process for the mass flow rate of 75.60kg/hr. and, the maximum outlet water temperature for bottle cleaning at 650C. It should have a mass flow rate of 66.6kg/hr. The maximum instantaneous efficiency is during sun shine and sun set hours. And, the minimum instantaneous efficiency is 84.96% on March 31 at 11:00 in the morning for the mass flow rate of 47.52kg/hr. However, the minimum instantaneous efficiency is 83.02% when the mass flow rate is 66.6kg/hr. And, the minimum instantaneous efficiency of the system is 62.19% when the mass flow rate of water is 75.60kg/hr. The maximum solar thermal energy harvested form a single collector at a mass flow rate of 47.52kg/hr is 3.19KWt on March 31 at 11:00 in the morning. However, the highest daily solar thermal energy produced on March 12 is 22.01KWthr and the lowest daily solar thermal energy produced on July 19 is 3.66KWthr. The appropriate location of solar collectors is identified to harness the maximum possible solar energy. The optimal number of collectors needed for partial supply of thermal energy to the industry are 368 (30 for mashing at 520C, 62 for mashing at 780C, 59 for bottle cleaning, 22 for feed water pre heating, 168 for CIP and 27 for kegging ). The Annual solar thermal energy production was analyzed for all processes. Those are 127.03MWhr, 333.47Mwhr and 1613.98MWhr for mashing at 520C, bottle cleaning and other thermal processes at 78-800C respectively. The total annual solar thermal energy harvested for all selected processes is 2074.48MWhr. vi Due to the integration of solar thermal system in low temperature industrial processes, the consumption of conventional thermal energy for the selected processes are reduced to 9101.70MWhr/year. Which means 18.56% of thermal energy consumption for selected processes in the industry could be saved. However, the total annual thermal energy consumption of the industry is reduced to 18147.76MWthr. This means 12.07% (10.05% from selected processes, 2.01% from overall heat loss and 0.01% from pre heating of fuel) of the fuel consumption in the industry is saved. In other way, 205,840.65 liter of furnace oil is saved every year. The total initial investment cost of the project is $440,864 (50% is project equity and the remaining is project debt). This project saves $165,813 of the annual cost of the industry for thermal energy application and reduces 729.54 tons of carbon dioxide (CO2) emission per year. The project equity is returned back with 1.6 years.
Design and Analysis of Solar Thermal System for Hot Water Supply to Minilk II Hospital New Building
(Addis Ababa University, 2016-06) Kebede, Dagim; Tadesse, Yilma (PhD)
Solar energy technology has led to the development of a number of solar appliances used for lighting, electricity, cooking and solar thermal systems. The most hopeful among them is the solar thermal system, to achieve the energy necessity for different applications at domestic as well as at the industry level. In this research work an attempt has been made to design and analyses solar thermal system for hot water supply to Minilik II Hospital new building. The selected solar collector and the heat storage are also designed based on: the amount of hot water supplied to the hospital throughout the day and the energy needed to heat the demanded hot water. Mechanical system of hot water distribution in the hospital, building structure, array of solar collector and thermal storage system of the project will be investigated. Transient performance of the system is computed using a numerical heat transfer model of a single glass cover flat plate collector solar water heater with riser and header type active system. The various design parameters are gathered from the inside country solar water heater manufacturers and dealer companies and also from the world experience. The meteorological data for simulation was prepared by taking the average of six years starting from 2010 - 2015. From the annual contribution of solar energy to the heating load and solar fraction the estimated values of investment cost, the unit solar energy cost and the pay-back period of the system was calculated. It was found that for Minilik II hospital of total daily hot water consumption of 30.475 m3, a total of 108 collectors with two storage tanks of each capacity 18.3 m3 are needed with initial capital cost of 1,006,865 Birr per project, which will cost a total of 1,864,054 Birr per project through-out its life time and the life cycle cost saving will be Birr per project. The unit price of solar thermal energy is 0.033 Birr per KWh and the payback period of the project is 2.2 year. Since the unit cost of solar energy (0.033 Birr/KWh) is less than the unit cost of electricity (0.46 Birr/KWh) in Ethiopia, therefore water heating by solar energy is a viable alternative to heating by electricity and fossil fuel (furnace oil).
Optimization of Biogas Production From Slaughterhouse Waste and Digester Sizing: A Case in Addis Ababa Abattoirs Enterprise
(Addis Ababa University, 2016-07) Tsegaye, Genet; Asefa, Birhanu (PhD)
This study focuses on production of biogas from slaughter house waste to generate optimal methane yield. Which has high calorific value under Optimum temperature, pH and substrate proportion (blood, manure and undigested stomach content). And also Digester Design for dumping waste of AAAE. In this study first experiment was carried out to determine pH, total solid, volatile solid and ash content of each type of waste fermented independently at optimal temperature (350c) and at pH 7. Second experiment was by mixing three type of wastes based on crossed D-Optimal design expert software which had 42 run at different proportion of substrate Blood and Manure at range of (10%-20%)’ undigested stomach content at range of (60%-80%) , pH range (4-10) and temperature at range of (20oc-45oc). After the experiment the following parameters: methane content, caloric value or energy generation capacity and volume of biogas, pH, temperature, total solid, volatile solids, and Ash content of each type of waste were determined. From individual type of 350ml sample waste (blood, manure and undigested stomach content) Maximum Biogas production and methane composition was 0, 7lit, 4lit and 0%, 66% and 54% respectively. From 42 run experimental result by crossed D-Optimal Design Expert software the best optimal methane composition and biogas production was 79.26% and 0.381lit/gm of VS respectively. Optimal condition was 20% blood, 20% manure and 60% undigested stomach content substrate composition, at pH=7.88 and temperature 32.49oc. 79.26%CH4 composition has a potential 7.88kwh per m3 of Biogas. The amount of biogas produce from AAAE waste is2968m3/day which has a potential to generate 23,393.4kwh/day of energy. 3,148.8 kwh/day apply to facilitate anaerobic digestion activity and remaining 17, 207.9kwh/day for steam generation. Which can cover for 70.7% of boiler furnace oil and gas oil consumption and save7, 087,740.ETB birr/year of its budget. This study has shown that application of biogas plant for AAAE is financially, environmentally and socially feasible. The cost benefit analysis shows that NPV is positive and benefit cost ratio is 2.03 which is greater than the proposed value for application of given project. As the financial analysis shows after implementation of this project AAAE can annually save Birr 6,006,520. Which can be invested to construct four digester plants having a volume of 753.75m3 with daily 120.6m3 total feedstock fed to the digesters. At optimal mixture of three waste and optimal condition. Key words- Digester, Biogas, Methane, slaughterhouse waste, anaerobic digestion
Study on Biogas Energy Production from Cactus Opuntia Ficus-indica (L.) Mill
(Addis Ababa University, 2016-08) Beshir, Jemal; Yimam, Abubeker (PhD)
Energy plays a driving role in socio-economic development arena; poverty reduction and improvement of the quality of life. Conversion of animal waste to biogas energy to replace traditional fuel and use of the slurry as a fertilizer is the current focus of the national biogas program of Ethiopia (NBP 2013). This paper presents the experimental results of the anaerobic digestion of cactus (Opuntia ficus-indica) (L.) Mill. The total solid (TS), volatile solid (VS), fixed solid (FS) and the C:N ratio of the feed stock (cactus) had been determined before the anaerobic digestion process began and then estimation of biogas production and methane content of each of the treatments, T1 (<1 year cactus at 27oC), T2 (<1 year cactus at 37oC), T3 (1 year cactus at 27oC), T4 (1 year cactus at 37oC), T5 (2 year cactus at 27oC), T6 (2year cactus at 37oC), T7 (3 year cactus at 27oC) and T8 (3year cactus at 37oC) were performed. From 500g of cactus it was found that the amount of biogas production and quality was highest in T2 (3500ml of biogas and 49% CH4) and T4 was the second highest in the amount of production and quality (3400ml of biogas and 45% CH4). T7 produced the minimum biogas production and quality (2500ml of biogas and 33% CH4). Moreover, compare to other source of energy, cactus produced a good volume of biogas but low in quality due to its C: N ratio. Thus, Cactus can be digested alone or it can be one of the feed stock for co-digestion process. This could give better quality biogas.
Optimizing the Technical and Social Benefits of Solar Photovoltaic Technologies in Ethiopia.
(Addis Ababa University, 2016-11) Tesfay, Abadi; Abebe, Solomon
Despite the abundance of renewable energy resources in the country, the rural and urban communities in Ethiopia are suffering from shortage of electricity. The grid electricity could not reach many areas due to inaccessibly related to remoteness. Solar energy, a resource widely available throughout the country, is also not utilized. Accordingly, this study tries to identify limits on technical and social benefits of solar photovoltaic technologies in Ethiopia thereby its use to increase electricity access. Thus we assess factors affecting the dissemination activities, such as solar PV installation practices, Solar Home and institutional system distribution strategies, system failures and their causes. To conduct this research, we performed desk reviews, Key informant interview, focus group discussions and field surveys. In addition, we analyzed the impact of PV orientation by comparing simulation result made by PVsyst software at various angles observed during field survey. One Kebles from each four regions, namely SNNPR, Amhara, Oromia and Tigrai regions were selected, where about 20 households were surveyed. In doing so, Factors affecting the dissemination activities as well as best orientation were able to be determined. The study also assess that, how Availability of replacement and maintenance, lack of Public awareness creation and institutional problems, tariff and shortage of market can affect the accessibility and large scale distribution of PV system. In order to disseminate the solar PV in ample amount throughout the country, this study would like to recommend that factors affecting the distribution needs to be considered at all levels in way to achieve maximum result, technical capability of the solar PV needs to optimized through appropriate installation with a recommended tilt and azimuth angle. By doing so, the vision that we aspire to have sustainable energy supply in the country as well as a reduce level of emission from biomass will be garnered. Key Words: SHS and institutional PV systems, social benefit, factors affecting solar PV dissemination, orientation optimization, tilt angle and azimuth angle, modeling.
Design of Coolant Heater For An Emergency ELECTRIC Generator Drive Diesel Engine By Solar Energy For A Cement Industry
(Addis Ababa University, 2016-12) Meleta, Tadesse; Alemu, Demiss(PhD)
coolant and lubricant to attain the optimum operating temperature without delay in an industry using diesel engine to drive emergency electric generator in attaining its rated power capacity for one of the diesel engine driven emergency electric generator installed for Mugher Cement Factory. The result will serve for avoiding the cement production equipment of the rotary kiln and related drive systems from thermal gradient deformation immediately after unexpected main grid failure. In order to improve the circulating coolant temperature and the pre-heating time requirement, electric heater has been installed. To measure the improvement of engine efficiency during starting up period after main grid failure, temperature data are collected from the generator set controller and measuring instruments both before and after installation of electric heater. These data have been collected when this experiment was made on site in Mugher Cement Factory. The data contain readings of temperatures [°C] obtained from measuring instruments and installed controller. The analysis of the system has been done by using controller performance display readings and performance measuring instruments. Besides, temperature reading data has been analyzed by using some statistical methods, particularly to investigate the improvements achieved or the severity of the existing problem. From the performance improvements, the results computed from observed data as well as from test instruments, the generator set shows that its performance has been clearly improved by using heater to heat the coolant. Besides these, it can be deduced, even if not tested, that coupling of the solar thermal technology can further improve its performance. Based on these preliminary results, a solar water heater of 100 litre capacity, with provision of auxiliary electrical heater in addition to solar heater, in comparison with the cases of electrical heater, is designed in detail to be locally fabricated and installed for the case of Mugher Cement Factory. Generally, selecting and adopting proper solar water heating technology for the circulating coolant of emergency electric generator drive diesel engine has improved preheating time in attaining engines thermostat opening temperature in a lesser time to avoid the rotary kiln and related drive-driven systems thermal gradient deformation immediately after the main grid failure of a cement industry. This is an indication of the applicability of the result of this thesis. xvii The output of the research shall contribute reliability for industry’s production processing equipment, especially the key equipment that operate at high process temperature, by avoiding rapid cooling that causes the thermal gradient deformation and leads to complete equipment damage and consequently loss of production, revenue and employee lay off due to inefficiency of the engine. The finding of this research can be used as the potential of making the diesel engine driven electric generator that enable to attain its full load immediately by adopting similar technologies for institutions that require immediate back up. Furthermore, it creates an opportunity in looking at heating water by harnessing energy from the sun for industrial and commercial firms in order to overcome the rising of oil prices as well as utilization of environmental-friendly alternative sources of energy, specifically renewable energy technologies and promoting green energy technology. Key words: Engine coolant, heating time, delay time, heater, emergency generator, kiln, cooler, solar radiation, solar collector.
Biogas System Planning for Rural Households Based on Energy Demand (The Case of Holeta District)
(Addis Ababa University, 2017) Mesfin, Debebe; Abubeker, Yimam (PhD)
This research is conducted to study the energy consumption trend and to make easy of planning the biogas system design which can helps to meet the energy demand of the rural households found in Holeta district. The energy demand of the households is assessed based on the questionnaire paper. The information of the assessed households is collected randomly from different family sizes that live in “Geda Jogo” and “Ada odo” Villages. Households are using electricity mostly for lighting purpose. Fire wood, Charcoal and dung cake are the main sources of energy to meet the cooking Energy demand. The average amount of annual fertilizer consumption by the peasant households is 220 kg. Spreadsheet modeling tool is prepared and it is used to estimate Households biogas demand, gas production potential of the households and Digester volume including the expected Loading rate. It is also used to forecast the basics of Economical aspects which should be known before the plant is designed. To crosscheck the proper functionality of the spreadsheet modeling tool Manual calculations has been performed for the average and peak values observed in the surveyed households and compared with the values found from the spreadsheet model. For the average values, the Biogas demand, the gas generating potential of the Households and digester volume observed in the spreadsheet calculation tool are 6.001m 3 /day, 6.8 m 3 / day and 20.3949 m 3 respectively. The values gained using manual calculations are 6.114m 3 /day, 6.8m 3 /day and 20.4 m i 3 . For the peak values calculation in spreadsheet modeling tool, the Biogas demand, the gas generating potential of the Households and the digester volume needed are 9.19m 3 /day, 8.8 m 3 / day and 26.3934 m 3 respectively. Where as in the manual calculation the values are 9.16 m 3 /day, and the digester volume is . Priority rank on the households energy demand has been performed, so that it will help on the biogas system design. The economical aspect of the biogas system is also included and how the households could be benefited using this technology. The estimated cost to construct the plant for the average values are ETB 29,840 with a payback period of 3 years. The cost spent to buy chemical fertilizer could be saved. Finally the benefit cost ratio is calculated to be 1.44 which is greater than 1.

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