MST-Department of Energy Engineering

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Characterization, Evaluation and Performance Optimization of Wheat Straw – Bagasse Fuel Pellets
(Kenyatta University, 2024-11) Matasyoh, Isabel Musula
The current transition of the utilization of fossil fuels to sources of renewable energy has led to the exploitation of biomass energy from agricultural residues such as wheat straw and bagasse. The conversion of biomass waste into fuel pellets will provide an alternative source of reliable and affordable energy for cooking. This would help to curb the issue of over-dependence on fuel wood which results in deforestation. This research focused on the characterization, evaluation and performance optimization of wheat straw – bagasse fuel pellets. Wheat straw and bagasse were compacted to form fuel pellets. However, the fuel pellets could not be utilized directly before investigating their properties in order to determine their quality. The physical characteristics of the fuel pellets that were investigated included the moisture content, volatile matter, fixed carbon, ash content, calorific value, bulk density and mechanical durability. The effect of blend ratio, moisture content and raw material particle size on the ignition time, burning rate and specific fuel consumption of the wheat straw – bagasse blended fuel pellets was also studied. The water boiling test was used to determine the ignition time, burning rate and specific fuel consumption of the fuel pellets. This study involved varying four particle sizes (2 mm, 4 mm, 6 mm, 10 mm), four levels of moisture content (9.1%, 10.6%, 12.6%, 14.7%) and four blend ratios (10:90, 30:70, 70:30, 90:10). The results revealed that the fuel pellets with larger particles size, low moisture content and blends containing more bagasse had favorable burning characteristics. By using Response Surface Methodology, an optimization of the parameters was achieved. The results indicated that an optimum combination of blending ratio 10:90, moisture content of 14.70 % and a raw material particle size of 9.0481 mm resulted in the lowest ignition time of 38.001 seconds, highest burning rate 15.9511 g/min and lowest specific fuel consumption of 153.1153g/l. The findings of this work reveal that wheat straw – bagasse blended fuel pellets can be produced at optimal conditions by the use of optimization tools and practically utilized as a source of biomass energy.
Performance Evaluation and Optimization of the 600 Kwp Grid-Tied Solar Photovoltaic System at Strathmore University, Kenya
(Kenyatta University, 2024-03) Ayora, Emmanuel
Kenya boasts of abundant solar irradiation across its expansive regions, averaging between 4.5 kWh/m2 and 6 kWh/m2 per day. Despite this advantageous condition, solar energy's contribution to the national energy mix remains relatively low. This is partly occasioned by the solar PV systems degradation over time due to aging and other environmental factors. To boost solar energy contribution to the national grid, it is crucial to assess the performance of existing grid-tied solar PV systems and develop strategies to improve their energy yields and further help in designing and installing new plants. This study presents a technical performance analysis of a 600 kWp grid tied solar PV system at Strathmore University, monitored over one year between January and December 2019. Economic and thermographic analysis of the solar PV system was done. In addition, tilt angle optimization was done and experimentally validated. The performance indices studied according to IEC 61724 standard include performance ratio, capacity utilization factor, array yield, reference yield, final yield, total collection losses, and total energy yield. This solar plant generated 735 MWh in 2019. The annual average monthly performance ratio, capacity factor, and annual specific energy yield were 57.4%, 13.97%, and 1,225 kWh/kWp, respectively. The annual average monthly final yield, array yield, reference yield, and total system collection losses were 3.37 kWh/kWp, 4.49 kWh/kWp, 5.9 kWh/kWp, and 2.53 kWh/kWp, respectively. The thermographic analysis done showed that the system exhibits normal temperature distribution. The economic analysis demonstrated Levelized Cost of Energy and simple payback period of US$ 0.143/kWh and 9.1 years, respectively. The optimal tilt angle obtained through experimental validation was 11°. Further analysis on the effect of air gap on the PV performance indicated that by increasing the air gap of the solar panel from 100 mm to 150 mm, the back sheet temperature of the module decreased by 7.5% due to the increased flow of cooling convection air currents. The study reveals that the Strathmore University system's performance is comparable to other solar plants worldwide.
Rebound Effect of Kenya's Energy Efficiency Initiatives
(Kenyatta University, 2023-09) Omondi, Cynthia Achieng; Francis Njoka; Fenwicks Musonye
Abstract
Development of a Biogas to Bio-Methane Upgrading System for Domestic Cooking in Kenya
(Kenyatta University, 2023-06) Reuben, Mugagga Gad; Isaiah B. Omosa; Thomas F.N. Thoruwa
Abstract
Design and Performance Evaluation of a Biomass Gasifier: Case Study of Coffee and Rice Husks
(Kenyatta University, 2021) Mutuku, Kilaka; Thomas F. N. Thoruwa; Jeremiah Kiplagat
About 36.1% of Kenya’s population lives below the poverty line. Low income has forced most of the Kenyans to opt for the cheapest available sources of energy. Biomass fuels are the most important source of energy in Kenya with wood-fuel (firewood and charcoal) accounting for over 68% of the total primary energy consumption. In spite of past efforts to promote substitutes for wood-fuel, the number of people relying on them is not decreasing. Consequently, it is projected that biomass will continue to be the main source of energy for the majority of the rural population and urban poor. Each year, over 2.8 million people in the world die prematurely from diseases caused by inhaling smoke from indoor fires due to incomplete combustion of biomass fuels in open fires and inefficient stoves. As a result of deforestation, biomass resources (fire wood and charcoal) are getting scarce. Waste products from agro-processing industries such as coffee husks, rice husks have been a major challenge in disposal. Biomass gasification is one of the few technologies that can potentially turn these wastes into energy for both industrial and domestic use. Although gasification has been around for more than 200 years, the technology is still new in Kenya. This study involved designing and developing a household-size biomass gasifier for the production of syngas using locally available biomass fuels namely; rice husks and coffee husks. Characterization of test fuels was based on their calorific value, percentage moisture content, volatile matter, ash content, fixed carbon, bulk density and porosity. Calorific value of rice husks and coffee husks was 15.9±0.8kJ/g and 18.1±0.8 kJ/g respectively. Bulk density of sampled rice husks and coffee husks was 127.4±1.2 kg/m3 and 218.0±1.6 kg/m3 respectively. Porosity of sampled rice husks and coffee husks was 87.4±0.9% and 71.9±0.6% respectively. Moisture content of sampled rice husks and coffee husks was 8.0±0.0% and 8.8±0.3% respectively. The percentage volatile matter of sampled rice husks and coffee husks was 62.8±0.3% and 78.4±0.0% respectively. The percentage ash content of sampled rice husks and coffee husks was 20.2±0.4% and 3.9±0.1 respectively. The percentage fixed carbon of sampled rice husks and coffee husks was 17.0±0.7% and 17.7±0.1% respectively. The maximum temperature obtained inside the gasifier reactor was mainly in the range 800°C to 1100°C. 1.5 liters of water at an average temperature of 24°C boiled in the stove within 4.7 to 8.5 minutes. Economic analysis of the gasifier found out that if a family shifts from LPG to using the constructed gasifier the payback period is 1.09 years, net benefit is Ksh45,000 (450USD) and rate of return on investment is 214.29%.
Development and Performance Evaluation of Solar green house Dryer with Desiccant Energy Storage system for Tomatoes
(Kenyatta University, 2021) Mbacho, Susan Andrew; Thomas F.N. Thoruwa; Nickson K. Lang’at
Tomato is one of the most important horticultural crops widely grown in the tropical East Africa countries. It is mostly used as vegetable recipe for food preparation at most homes or consumed raw as a salad. However, during the rainy season, tomato farmers experience widespread post-harvest losses due to insect and molds infestation. Also, during harvesting seasons, most markets in East Africa are flooded with the produce leading to over- supply against low demand resulting to heavy postharvest losses. Therefore, it is necessary to use appropriate drying technologies especially solar drying technology to reduce these losses. The use of solar drying technology is a good alternative solution to the problem of crop drying and especially the perishable tomato crop. Literature review show that most solar crop drying technologies developed for the past 50 years have very small loading capacity and cannot operate during the night. Therefore, in this study, we developed an integrated greenhouse solar dryer with Clay-CaCl2 solid desiccant energy storage system. Solar greenhouse drying systems have an advantage over other solar drying systems because its structural simplicity combined with high loading capacity. In addition, they have relatively good thermal crop drying performance compared to most solar dryers. The system was tested under no-load and load conditions. The experimental study with no-load condition exhibited the mean collector temperature of 41.9 °C giving an average temperature rise of 14.7 °C (35%) above the ambient (27.2 °C) with an average R.H. value of 32.6% at the flow rate of 0.28 m3/s on the test date. When the desiccant energy storage was used during night an average greenhouse temperature recorded within the drying chamber was 26.5 °C higher than the ambient temperature of 15.9 °C (40 % temperature rise). The results obtained under desiccant energy storage showed that at a 0.07 m3/s air flow rate with an average rise in temperature of about 13.6 (32.3%) against the average ambient temperature of 28.5°C. The average relative humidity within the system was found to be 36.5% lower than the ambient R.H. (84.1%). The collector efficiencies obtained from no load test was 46.2% and 40.8% for the dryer and desiccant chamber respectively. The performance of the dryer was evaluated with fresh tomato load during the month of September - December 2019 at Kenyatta University field site. The dryer demonstrated capacity to dry fresh tomatoes from 93.9% (wb) to 8.3% (wb) within 27 hours with solar greenhouse drying efficiency of 23% while at night the dryer demonstrated desiccant drying efficient of 19.9%. The drying rate for the two-day solar drying was 0.985 kg/h and 0.875 kg/h respectively and that in night drying using desiccants was 0.34 kg/h. The economic analysis of the drying system shows a payback period of less than a year (0.54 year) with benefit-cost ratio of 8.4 implying that the system is economically viable. On the basis of these results, it was concluded that prototype solar greenhouse dryer with Clay-CaCl2 energy storage system has great potential for tomato drying and other high moisture agricultural products in East African countries.
Development of Biomass Wastes Briquette Stove for Domestic Use
(Kenyatta University, 2015-11) Mulindi, Humphrey M.
Biomass energy in the form of woodfuel and charcoal contributes close to 68% of the total energy demand in Kenya. The continued depletion of biomass resources has led to the use of agricultural residue to supplement energy needs for domestic cooking. Biomass stoves used to burn these fuels in Kenya are characterized by high inefficiencies and high emissions that pose environmental and health risks to the users. This research aimed to reduce biomass fuels consumption, reduce fuel indoor air pollution and deforestation. The project was carried out in two phases. First, in 2010 there was a survey of the status of bio-waste fuel briquetting technology in Nairobi and peri- urban Nairobi area. Secondly, a semi-gasification stove that uses briquettes derived from solid organic waste material was developed. The survey involved an interview of 63 briquette producers identified from desktop research within Nairobi and its per-urban areas, out of which 40, 15 and 8 were community based groups, NGOs and briquette producing companies respectively. A total 175 briquette users were randomly selected and interviewed from a list of briquette consumers given by briquette producers interviewed. Based on the results of the field survey, a semi- gasifier stove was designed and constructed. The semi-gasifier stove construction took place at Kenyatta University Engineering workshops. Tests were done to determine the thermal efficiency, specific fuel consumption and power of the stove. Standard stove emission test were conducted using KANE 455. About 33% of the briquettes made were from a mixture of charcoal dust and paper. Characterization of briquettes was based on their calorific value, percentage moisture, volatile matter, ash content, fragility of briquettes and burning characteristics. The calorific value of briquettes was between 14.21kJ/g and 24.64kJ/g for water hyacinth based and carbonized baggasse briquettes respectively. Moisture content of the briquettes ranged from 5.8% to 14% for carbonized baggase briquettes and for charcoal with bean stocks plus paper respectively. Carbonized coffee husks with starch binder had the lowest volatile matter of 10.1% while coffee husks with paper had the highest volatile matter of 71.2%. Briquettes made from sawdust and paper had the lowest ash content of 8.8% whereas briquettes from charcoal dust and clay had ash content of 66.8%. The percentage fragility of the briquettes sampled ranged from 0.1% to 80.4% for charcoal with clay and sawdust with paper respectively. The semi-gasifier stove had an average thermal efficiency of 30%±3 and an average fire power of 2.5kW±1.5. The emission testing of the stove using KANE 455 gas analyzer for CO, CO2 and CO/CO2 ratios showed the average values of 0.2067 ± 0.0259ppm, 2.6771 ± 0.13307ppm and 2.31374 ± 0.13184 respectively. Economic analysis show that if a family were to invest in the stove, they would save about Ksh 30($ 0.35), Ksh 1000 ($11.7) and Ksh 2200 ($25.8) ,if their initial cooking stove is open fire, kerosene stove and charcoal stove respectively. If a family claimed carbon credits by using the stove, it would be entitled to up to Ksh 8,000 ($94.1) during its entire life. For mass production the stove would retail at an average of Ksh 800 ($9.4). The prototype stove developed was found to meet the intended need for being used by fuel briquettes.
Design, development and testing of a liquefied petroleum gas powered tomato dryer with water energy stotage
(Kenyatta University, 2015) Njoroge, John Kamindo
Potential of using maize stalks for fuel ethanol production.
(2012-02) Mwangi, Lucy K.
In Kenya, a country that has not been successful in getting its own fossil fuel deposits, the main material used for ethanol production has been molasses but its supply compared to demand is becoming limited. There is need for alternative materials to produce ethanol without affecting food supply. This study investigated the potential of juice from maize stalks grown locally and normally a byproduct of maize farming, for production of fuel ethanol. Selected Kenyan maize varieties were grown in two seasons, March and September of year 2008. This was done under typical field conditions and sampled at three growth stages, the silking, the milk stage and dry maize stage. Maize varieties for three agroecological zones in Kenya were used, the low dry lands, the medium altitude and the highlands varieties. The juice was extracted by crushing the stalks with a 3- roller mill sugarcane crusher and analyzed for total sugars using a digital refractometer (NR-151, China) and specific sugars using a high performance liquid chromatography (HPLC) with a reverse phase column and refractive index detector (RID). The juice was then fermented using baker's yeast (Saccharomyces cerevisiae) at constant temperature of 27DC and a pH range of 4-5, distilled at 78 DC and the yield of alcohol determined. The ethanol obtained was tested in a Chinese wick stove (wheel brand model 62) for fuel properties (specific fuel consumption, fire power, burning rate and thermal efficiency) for domestic cooking application. Its performance was compared to that of kerosene fuel. The highest juice yield obtained was 176.67mllstalk (18840litres/hectare) for maize variety HB625 at the green maize stage, while the lowest was 8.33ml/stalk (616Iitres/hectare) for variety Katumani in the dry maize stage. The two varieties also had the highest and lowest ethanol yields at 1445.5litres/hectare and 42litres/hectare respectively. Hybrids had the highest juice and ethanol yields per hectare. The three main sugars identified in the maize stalk juice were sucrose, glucose and fructose. The trend for the sugars was a decrease for fructose and glucose and an increase in sucrose as the maize plant matured. Ethanol obtained burnt with a blue flame compared to the yellow flame of kerosene, with a power output of 1.08kW and a thermal efficiency of 38.2%. However, about 2 times the quantity of fuel and heating time was required for ethanol compared to kerosene to bring to boiling point the same amount of water at the same conditions. The average cost of producing llitre of ethanol (93%v/v) from the maize stalks was found to be KSh.63.56 (about 1USD). The study has contributed positively to the search for a clean sustainable energy resource and consequently reduction of dependence on the fossil petroleum fuels in Kenya and other countries. Use of maize stalks as feedstock for ethanol production gives a renewable source of energy for the motor industry and for domestic cooking. Maize grows in plenty in Kenya and this can boost energy security for the country and also contribute to economic growth for the country, specifically the rural economy through diversification of the agro-industry.
Utilization of energy saving Cookstove Technology: The case of improved institutional cookstoves in Kisii and Nyamira Districts of Kenya
(Kenyatta University, 1999) Mosomi, Evans Nyamweya; Laichena, Justus K.
The main objective of this study was to determine the factors that influence the adoption and utilization of improved institutional cookstoves, which have a higher thermal efficiency, are safer to use, and are more user-friendly than the traditional cookstoves. Evaluation of the utilization, operation, and maintenance of the improved cookstoves, by those using them, was another major objective of the study. The study was carried out in institutions that offer catering services in Kisii and Nyamira Districts of Kenya. These included schools, colleges, hospitals and hotels. The study area falls under the highly populated regions of the country, where the shortage of fuelwood is currently acute. Institutions used in the study were randomly selected and constituted 61% all of the institutions offering catering services in the study area. These included 53 schools, 4 colleges, 10 hospitals, 10 hotels and restaurants. Three manufacturers-cum-disseminators of improved institutional cookstoves were also interviewed, two of which were based in Nairobi and one in the study area. The study was conducted by use of questionnaire and interview method. By use of three different sets of questionnaires, responses from the interviewee and observations by the interviewer were recorded. The first set of questionnaires was for cateresses and/or administrators of the study institutions, the second for kitchen staff, and the third for the cookstove manufacturers-cum-disseminators. Only 57% of the sample institutions were found to have adopted and were using the improved cookstoves. This is rather low considering the acute shortage of fuelwood in the study area, hence the need for use of energy-saving devices. The study established the main factors causing hindrance to the adoption of institutional improved cookstoves as the lack of awareness, among the non-users, on the existence and advantages of the improved cookstoves and the lack of information on where to acquire them. A reasonable number of the non-users knew about the improved cookstoves, had interest of acquiring them, but did not know where to buy them from. The initial cost of the improved cookstove was also reported as a limiting factor, though not rated very high. Reduction in the fuelwood used for a given cooking activity was generally acknowledged as being attainable with usage of the improved cookstoves. Such fuelwood saving translated directly to monetary gain through reduced expenditure on the cost of purchasing fuelwood. The study also found that the most desired characteristics of the improved cookstoves, by the kitchen staff, are that they provide a smoke-free and cool kitchen environment, are safer to work with, cook faster and keep the food hot for a long period after cooking. They however did not like their lack of tilting mechanism. In spite of the numerous advantages cited, the study showed that there were some users of the same cookstoves who did not realise their advantages. This was due to misuse of the cookstove through improper operation, poor preparation of fuelwood, poor or no maintenance of the cookstove system, and failure to repair or replace broken or damaged parts of the cookstove. This was mainly due to lack of training on the operation, repair, and maintenance of the improved cookstoves. Manufacturers-cum-disseminators of improved cookstoves by conceded that they had not marketed the cookstoves widely. This was actually the cause of the lack of awareness to potential buyers. There is, therefore, a clear need for better promotion strategies by the disseminators of the improved cookstoves since there is an existing large market.
Enhancing efficiency of biomass carbonization for high Quality and quantity charcoal production by using Metallic clay insulated kiln
(Kenyatta University, 2014) Mulei, Fredrick Mwange; Laichena, Justus K.; Okwach, Silvester
The main objective of this study was to construct a metallic clay insulated kiln to enhance charcoal yield in quality and quantity. This research project aims at improving the charcoal quality in terms of calorific value and smoke - free, and maximum yield of charcoal (per kilogram of biomass substrate loaded). The quantity of charcoal harvested per kilogram of primary four biomass materials loaded as substrates was determined in four tests in each substrate. The main objective was to develop metallic clay insulated kiln with high efficiency, economical and environmentally friendly. metallic clay insulated kiln would offer solution to the problems of low efficiencies of existing charcoal kilns, for example, Traditional Earth Mould Kiln, Mark V. Kiln, Beehive kiln, and Half Orange kiln, among others. These kilns have efficiency of 10%, 31%, 32% and 28.8%, respectively, compared to the achieved 40.85 ± 5.04 % for this metallic clay insulated kiln. In this research a metallic clay insulated kiln was constructed and tested. The major aspect is that a proto type 0.15 m' drum was used to provide feedstock housing. This was tightly covered such that no fraction of feedstock was burned to provide carbonization heat. Clay insulation housing was constructed while the drum was provided with metallic stands and each of the substrates was loaded in the drum. Insulation wall made of clay/mud was constructed to prevent heat loss from the drums and combustion area. The quantity of charcoal produced from the metallic clay insulated kiln was compared with the quantity of wood substrate used. To determine the quality of the charcoal (in terms of calorific value and smoke), universal standard charcoal testing method was used that is Water Boiling test. The quality of charcoal produced from the kiln was then compared with charcoal produced from other different existing kilns in the literature. The data analysis was done by the help of statistical package for social science (SPSS) and Microsoft Excel. In conclusion, efficiency of charcoal production should be emphasized so as to make the practice of charcoal production sustainable by use of metallic clay insulated kiln. It was also found that metallic clay insulated improved kiln had higher efficiency (40.85 ± 5.04 %) than existing kilns such as Beehive, Mark V, Half Orange, Traditional Earth Mould, drum kilns adopted by FAO and others. Adoption! utilization of the metallic clay insulated kiln (with high efficiency as obtained in this research project (40.85 ± 5.04 %)) will reduce/cut-off the problems experienced in use of the _existing low - efficiency kilns. It is both an economical benefit, and environmental friendly. Charcoal production using improved charcoal kilns with high efficiency would give much higher yields of charcoal of excellent quality (in sense of HHV and smoke-free). This can make the practice very profitable, and users will have motivation for sustainable production of charcoal.
Performance of a Double Reflector Solar Box Cooker with Phase Change Material Energy Storage
(2014-02-19) Mwaura, Margaret Muria; Thoruwa, T. F. N.; Okwach, Silvester
The use of solar energy for cooking offers an alternative source of energy to the high cost of petroleum products and the diminishing wood fuel products for cooking and heating applications. An effective solar cooker is the one that can be used throughout the day and in the evening when there is no sunshine. Most areas in Kenya can be considered as a high potential solar energy area because Kenya is located on the equator. Most of the solar cooker designs do not have thermal storage systems and can be used for cooking when there is sunshine and cannot be used during cloudy weather or in the evening. The aim of this study was to design and assess the performance of a double reflector solar box cooker with an energy storage unit. The use of phase change materials (PCMs) as a technique of storing energy was used to overcome the time mismatch between solar availability and demand. The PCM used in this study is acetanilide with a melting point ranging from 113 to 116 °C. The box cooker was designed so that the length to width ratio for the reflector and the glass window was 4:1. This eliminated the azimuth tracking towards the sun. Three sets of experiments were carried out, one without loading the cooking pot of the cooker, one with water as the cooking load and one with different actual cooking loads in the School of Engineering and Technology Demonstration Center, Kenyatta University. The measured parameters included, the solar radiation, ambient air temperature, temperatures of the different components of the solar cooker, load temperature and wind speed. The data values were read and recorded by use of a data logger at regular intervals of 10 minutes. Data analysis was done using statistical measures. An average stagnation temperature of 85.9 ± 24.0 °C and 82.7 ± 24.3 °C was achieved in the two pots. The average solar radiation was 637.1 ± 212.0 W/m2. The cooking power tests achieved a coefficient of performance of 0.754. The results showed that the double reflector solar cooker with energy storage can be used to cook meals throughout the day and in the evening. Noon cooking does not affect evening cooking. The adoption of this study will be beneficial to Kenyans as it will increase the acceptability of the solar cookers hence reduce the consumption of wood fuel and petroleum products. This will reduce the rate of depletion of wood resources, save time and reduce expenses for the user which could be diverted to increased productivity and monetary gains thus raising the living standards and a clean environment devoid of hazardous emissions associated with wood and fossil fuel combustion.
Calcium Chloride Supported on Purified Spent Bleaching Earth as Potential Adsorptive Material for Air Dehumidification Application
(2013-03-22) Mathaga, Kihara John
Thecosmic limitation of high humid environment in tropic regions spurs a lot of interest to the developmentof low cost desiccants. Calcium chloride has been indicated as the oldest adsorbent desiccant among chemicals and gas dehydration industries. However, calcium chloride dissolution behaviour makes it difficult to be utilized well as desiccant. The first attempt to suppressdeliquescence behavior for dehumidification purpose was in 1976 where silt loam was usedas the host material. Further work has been presented to achieve the same goal using pure clay.The pollution effect of the spent bleaching earth (SBE) necessitated an investigation to determinewhether SHE could be used to eradicate the deliquescence behaviour of calcium chloride.The spent bleaching earth was purified to remove the entrained hydrocarbons through three steps; solvent extraction using hexane, oxidation of the hexane residues using 30% hydrogenperoxide and thermal oxidation. The ratio of 1 gram spent bleaching earth to 5 ml hexane and reactivation temperature of 550 DC in thermal oxidation were established as the optimalconditions for reactivation of spent bleaching earth. Hexane was found to remove about 25% of the entrained hydrocarbons mainly oil which was characterized. The results for the characterization indicated that the oil recovered could be utilized in non-food applications such as bio-lubricant, detergents, soap and other oleochemicals. Hydrogen peroxide removed about 10%of the remaining hydrocarbons after hexane extraction and thermal treatment about 5% after the two preceding steps. Laboratory studies were conducted to assess the mixing ratio of the inorganic salt, auxiliary binder and purified spent bleaching earth in the development of the composite adsorbent. Samples with different ratios were subjected to a humid environment of 88%relative humidity, by preparing a saturated solution of potassium chromate in a sealed beaker.The samples which recorded.minirnum surface wetting, spalling and cracking as well as high water uptake were further subjected to multiple sorption cycle tests. For all the tests performed, sample ratio of 3 :1 :0.25 of PSBE :CaCb :starch recorded the best results and was furthertested for its sorption properties at different relative humidity's. Sorption properties were carried out in a humidity chamber at 11.3, 32.78, 43.16, 52.89, 75.5 and 93.58% relative humidity where the sorption capacity recorded 14.88, 17.60, 20.95, 24.40, 33.40 and 45.55% water uptake respectively. The desiccant developed was found to be effective in high moisture content and thus viable in tropic regions where such environs are common. The sorption data obtained were subjected to the Langmuir, Freundlich and Brunaeur-Emmett- Teller (BET) adsorption models in order to determine the type of adsorption isotherm that best interpreted . water sorption by the material. Results indicated that, water adsorption onto adsorbent developed followed BET and Langmuir type III isotherm which indicated the formation of multilayer. The sorption capacity of the adsorbent matrix developed recorded 40 to 45% water uptake which cohered with commercially available desiccant such as silica gel. Since the SBE is normally disposed on potential land and limitations for this method of disposal is enormous, it is recommended that, oil manufacturing industries should emphasis on regenerating and re-using this waste in making products such as desiccants which they can use to preserve their products as well as sell to other consumers.
Performance of a modified vehicle drive system in generating hydropower
(2012-04-03) Muriithi, James Muchira
Micro hydropower generated electricity can function as an effective tool for rural development. One of the barriers to smooth implementation of community/village micro hydropower schemes in the country is lack of appropriate hydraulic turbines, thus making the site specific costs of micro hydropower rather high, hence not easily affordable by the rural communities. The purpose of the study was to investigate the use of a vehicle live axlepropeller shaft system to replace conventional turbines for micro hydropower generation. There are axle-propeller shafts of many vehicles that have fallen into disuse and are commonly found in many motor vehicle scrap yards. New ones are also entering the Kenyan market with the small vehicles (saloon cars; station wagons; panel Vans, Pick-ups, lorries/trucks, buses/coaches and minibuses/matatus) comprising the biggest percentage, for example in the year 2008, out of 121,831 newly registered vehicles 65,556 (53.8%) belongs to this category. The study was carried out mainly to investigate and establish the performance of the live rear vehicle axle-propeller shaft as a micro hydropower electricity generation system with the objective of lowering the unit cost of hydropower generation in small water streams. This was done by modifying a vehicle axle propeller shaft system by fixing designed buckets on the wheel rim to take the role of a turbine runner and replacing the propeller shaft right from the rear universal joint with a solid bright steel shaft where mechanical power is generated and tapped. A wheel rim/turbine casing with a nozzle for creating a water jet was fabricated and together with a mounting frame for the axle formed a complete Vehicle Propeller-Axle as a Turbine (PAA T). A jet of water from the nozzle strikes the buckets and the kinetic energy is converted into rotating shaft power by the wheel rim and the rear axle. The power is transmitted through the differential box with an accompanying speed increase to the rear universal joint where a shaft is fixed for eventual mechanical power take off. The power can be used to drive mechanical equipments or an alternator to generate electricity. The performance of the propeller-Axle as a turbine was tested at a community hydropower site in Kirinyaga, constructed for this purpose. The tests were conducted to determine the power output and efficiency under a constant head and different discharges. The final result of the study was a low cost vehicle axle-propeller shaft system operating as a turbine cost of USD 274.4), generating 1.18 kW of shaft power at an optimum flow rate ofO.0238 m /s at a gross head of 21.874 m and at an optimum loaded runner speed of 500 rpm. The specific speed of the modified vehicle system as a hydraulic turbine was 12. The energy cost from a hydropower scheme using a vehicle axle-propeller shaft as a turbine is 10 times cheaper than that of a similar scheme using a diesel generator as its source of power. These research findings are an important contribution to providing a solution to increasing use of micro hydropower for rural electrification by making the technology available and affordable to individual and communities in the rural areas. Vehicle drive systems are available as dumped materials in most metal scrap yards and car garages scattered across the country and they are an environmental hazard as there are no vehicle parts re-cycling facilities in the country.
Performance of a 2-element plane reflector augmented flat plate collectors for solar water pasteurisation
(2011-12-07) Ako, Elias Onyango
Access to safe and adequate water supply and improved sanitation is a fundamental need and a basic human right vital for health and dignity of all people. The situation has therefore called for concerted effort which has been expressed in the global commitments reiterated in the Millennium Development Goal (MDG), to reduce to half the population of people who lack access to safe and adequate water supply by 2015 and provide safe and adequate water for all by the year 2025. There are various techniques that have been used ,to disinfect water and make it safe to drink. These include: chlorination, ultra-violet disinfection, use of ozone gas, pasteurization and mixed-oxidant gaseous systems which is the most recent technology. Conventional water treatment methods rely heavily on chemicals, high energy consumption, use of expensive equipments and huge capital investments. Although they are suitable where large amount of water is required, they are not suitable for most rural settings existing in Kenya today that are normally scattered making centralized system a very expensive venture. Direct application of heat is one of the oldest and most reliable method of water disinfection. This study has pursued the concept of heating water using solar thermal energy to kill disease causing organisms, mainly E. coli which is one of the major indicator of fecal pollution in water. The direct heating of water was investigated using a 2m2 flat plate collector with a 2- element plane mirror reflector used to concentrate solar radiation from an aperture area of 4m2. Two experimental collectors were investigated; one having 20mm diameter galvanized pipe with a 26 gauge stainless steel absorber sheet and the other with 18mm diameter copper pipe with a 32 gauge aluminum absorber sheet. In both investigations, collector without reflectors was used as control experiment. Thermal performance tests have been conducted using continuous flow operation at controlled flow-rate (30±31/hr and 40±31/hr) and using pasteurization tests with thermostatic valve installed with a valve opening temperature of 82°C. In both the experimental systems under investigation it was observed that the use of mirror increased the day average instantaneous efficiency by up to 10% during continuous flow operation and up to 100% in output of pasteurized water discharged via the thermostatic valve. Water quality tests were done for both raw and pasteurized water samples using presumptive test for total coliform and Eijkman test for confirmation of E. coli in water. There was no E. coli found in pasteurized water. Data analysis was done using both descriptive and inferential statistic. An economic analysis of the solar pasteurization system has indicated an annual saving of up to 5tonnes of wood for collector with reflectors and an aperture area of 4m2 having a daily pasteurization output of up to 1001iters for a day under clear sky condition with an average solar radiation of 720W/m2, ambient temperature of 28°C and average wind speed less than 2m/s. Thus, the adoption of this study would not only reduce the number of uses of water borne diseases such as cholera and typhoid which have been identified as major cause of morbidity in Kenya by the Health Sub-sector Strategic Plan (19992004) but also lead to a reduction in environmental degradation, green-house gas emissions and health effects associated with inhaling smoke.

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