Sustainable Energy Consumption

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    Optimization of Binary Mixtures of Biodiesel and Fossil Diesel for Clean Energy Combustion
    (Springer Nature, 2019-05-31) Mosonik, Bornes C.; Kibet, Joshua K.; Ngari, Silas M.
    There is an urgent interest initiated to develop clean energy resources with the aim of reducing exposure to environmental pollutants and explore model fuels that can hasten the achievement of clean energy combustion. This work investigates various ratios of biodiesel and commercial diesel in order to propose model binary fuels for clean energy combustion. Accordingly, diesel blends of ratios 1:1, 3:2 and 2:3 were each pyrolyzed at a contact time of 5 s in a quartz reactor at 1 atmosphere pressure. A model temperature of 500 °C was explored in these experiments. The charcoal content for pure fossil diesel was compared with the binary diesel residue. Gas-phase molecular components were determined using Gas chromatography (GC) coupled to a mass selective detector (MSD). Elemental composition of thermal char was determined using Smart Elemental Analyzer. Radical intensities for the three types of char (biochar, bio-fossil char, and fossil char) were measured using an X-band electron paramagnetic resonance spectrometer. It was noted that at a ratio of 2:3 (Biodiesel: Fossil diesel), harmful molecular products reduced significantly, 76–99%. Elemental analysis data indicated that the carbon content from commercial diesel was very high (≈ 70.61%) as compared to approximately 53% for biodiesel-fossil diesel mixture in the same ratio 2:3. Interestingly, the free radical content was reduced by nearly 50% in favour of the biodiesel/fossil diesel mixture. These results are encouraging and suggest that a better optimized fuel mixture has been found for better clean energy combustion.
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    Synthesis, characterization and spectroscopic properties of Cu2+:ZnO, Ce3+:ZnO, and Cu2+, Ce3+:ZnO
    (Springer Nature, 2020-06-22) Mulwa, Winfred Mueni
    Pristine ZnO, Cu2+:ZnO, Ce3+:ZnO and Cu2+, Ce3+:ZnO nanopowders with different doping concentrations (0, 0.31, 0.62, 0.93 and 1.24% of dopant) were synthesized by sol–gel technique with low sintering temperature of 600 °C. The powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), UV–Vis optical absorption and photoluminescence (PL) spectroscopy analysis. XRD patterns revealed that all the compounds are hexagonal wurtzite crystalline structure and that all the dopant atoms substituted Zn atoms in the ZnO lattice and there was no formation of extra Phases. SEM photographs displayed morphology of the prepared nanopowders. The UV–Vis absorption spectrum presented an absorption peak at 355 nm which was ascribed to ZnO nanoparticles. The photoluminescence spectrum displayed emission peaks at 486 nm and 527 nm. The 486 nm peak conformed to bandgap excitonic emission and the 527 nm peak was attributed to the existence of independently ionized oxygen vacancies. Sol–gel technique has capability for application in manufacturing units, because its process is simple and the reagents used are economical. Particle sizes in the range 10–51 nm were realized from the TEM analysis.
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    Energy Efficiency of Building Technologies and Climate Change- a Case Study of Carbon Sequestration in Migori County
    (University of Nairobi Research Archive, 2021-09-06) Sangori, Robert O.
    The global population has continued to increase leading to a greater demand for housing and associated building materials and products which affects the environment and climate in various ways. The effects on environment happens at different phases mainly at the extraction and manufacturing phase where energy consumed depends on the building technology adopted. Due to inadequate research, data and literature on the application of the building materials in meeting the housing demand, the energy consumed and equivalent carbon dioxide emitted in entire stages of production by building technology processes are lacking in developing countries with no exception to Kenya. This study estimated how building technologies by using soil, water and forest/tree cover affect carbon sequestration potential of these resources. The study was done in Migori county with the objective of establishing energy expenditure of building technologies and their effects on carbon sequestration processes and hence potential contribution to climate change through atmospheric CO2 accumulation. The study identified the dominant building materials adopted in the county and their embodied energy levels; assessed the extent of adoption of energy efficient building, resource efficiency of mortarless compared to mortared technologies, established the relationship between building materials use and greenhouse gas emissions; and determined suitability of approval processes to promote selected building technologies by Regulatory Authorities. The main hypothesis of the study was that building technologies have no significant effects on carbon sequestration and hence does not contribute to adverse climate change.The study applied survey, experimental and correlation design approach and adopted both quantitative and qualitative sampling methods to generate primary data towards addressing the research objectives. The survey method was essential in obtaining building technologies, embodied energy and the resultant carbon dioxide emission equivalent of the selected building materials. The county of study was identified by way of purposive sampling. Multi-stage sampling was employed with county as a unit of study, sub-counties forming the study first stratum and the nature of wards (urban and rural) as the second stratum unit of study from which the wards were sampled. The study identified the major approved walling materials in the study area to be bricks and concrete with specific embodied energy of 3.0 MJ/kg and 0.670 MJ/Kg respectively. The study further revealed that there is low application of energy efficient technologies such as interlocking stabilized soil blocks, prefabricated and precast materials. The experimental design revealed that the building materials extraction, manufacture, transportation, and construction consume significant amount of energy and emit greenhouse gas into the atmosphere and that the level of emission of greenhouse gas is dependent on the building technologies adopted. The mortared technology was associated with large amount of embodied energy and equivalent greenhouse gas emission which impact negatively on human life due to high social cost of pollution.The study findings were used to show national outlook of embodied energy and equivalent CO2e projections for the years 1800, 2019 and 2050 of the various walling materials. It is demonstrated that less efficient building technologies continues to dominate the housing sector with bricks leading over the period of analysis at 7,176 GJ in 1800, 306,730 GJ in 2019 andxxi590,263 GJ in 2050 if the current environment of Migori is to prevail nationally. The CO2 emission associated with the walling materials shows a direct relationship since bricks attracted higher values of CO2 emission at 22,404 tons in 1800, 575,317 tons in 2019 and 1,104,363 tons in 2050. Similarly, energy efficient building technologies such as ISSB attracted low greenhouse gas emission. The study concludes that there is a strong relationship between the applied building technology and building materials and climate change demonstrating the need to minimize the embodied energy by using energy efficient building technology and adopting the use of walling materials with minimized embodied energy in order to reduce the greenhouse gas emission. The study revealed that there was minimal knowledge on the application of energy efficient technologies and that the approval process does not promote the use of energy efficient building materials and technologies due to lack of policy to spearhead the initiative.This study is significant in the policy formulation related to the energy efficiency building codes, green building regulations, implementing sustainable environmental strategies and action plans. It is also essential in providing professional knowledge on the causal relationship between building technologies, building material, climate change, environmental sustainability and environmental degradation in the built environment in regard to carbon sequestration relating to soil, water and tree/forest cover
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    Polycyclic Aromatic Hydrocarbon Emissions Arising from Domestic Combustion: A Kenyan Case Study
    (Research Gate, 2022-10-07) Forbes, Patricia; Osano, Aloys; Maghanga, Justin; Munyeza, Chiedza; Chaka, Bakari; Adeola, Adedapo; Nsibande, Sifiso
    A vast number of people in developing countries rely on solid fuels, including wood and charcoal, for domestic energy supply. We have studied the gaseous polycyclic aromatic hydrocarbon (PAH) concentrations in Kenyan homes in order to better understand the potential health risks associated with domestic combustion practices and to advise mitigation strategies. A comprehensive survey was conducted to elucidate the complex and multi-faceted factors governing fuel use in Kenyan coastal and inland regions. Results showed an almost equal distribution in fuel type usage between firewood, charcoal, kerosene and liquid petroleum gas (LPG). In rural areas, three-stone stoves were still predominant, whilst cleaner devices burning kerosene and LPG were used more widely in urban communities. Indoor air was subsequently sampled in a range of urban and rural households using portable polydimethylsiloxane sampling tubes. These were extracted using the plunger assisted solvent extraction (PASE) technique, followed by GC-MS analysis of the U.S. Environmental Protection Agency (EPA) priority PAHs. Total PAH concentrations in samples collected varied considerably (0.82-173.69 µg/m 3), which could be attributed to differences in fuel type, combustion device, climate, and nature of the households. Higher PAH concentrations were found in rural homes, although ambient PAH concentrations were higher in urban environments, likely due to traffic contributions and population density. Toxicity equivalent quotient values varied widely between households and emphasised the importance of good combustion practices to minimise human exposure.
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    Analysis of gaseous polycyclic aromatic hydrocarbon emissions from cooking devices in selected rural and urban kitchens in Bomet and Narok counties of Kenya
    (Springer Link, 2022-05) Adeola, A. O.; Nsibande, S. A.; Osano, A. M.; Maghanga, J. K.; Naudé, Y.; Forbes, P. B. C.
    Traditional combustion devices and fuels such as charcoal, wood and biomass, are widely utilised in rural and urban households in Africa. Incomplete combustion can generate air pollutants which are of human toxicological importance, including polycyclic aromatic hydrocarbons (PAHs). In this study, portable multi-channel polydimethylsiloxane rubber traps were used to sample gas phase emissions from cooking devices used in urban and rural households in Bomet and Narok counties of Kenya. A wide range of total PAH concentrations was found in samples collected (0.82 - 173.69 µg/m3), which could be attributed to the differences in fuel type, combustion device, climate, and nature of households. Wood combustion using the 3-stone device had the highest average total PAH concentration of ~71 µg/m3. Narok had higher indoor total gas phase PAH concentrations averaging 35.88 µg/m3 in urban and 70.84 µg/m3 in rural households, compared to Bomet county (2.91 µg/m3 in urban and 9.09 µg/m3 in rural households). Ambient total gas phase PAH concentrations were more similar (Narok: 1.26 - 6.28 µg/m3 and Bomet: 2.44 - 6.30 µg/m3). Although the 3-stone device and burning of wood accounted for higher PAH emissions, the charcoal burning jiko stove produced the highest toxic equivalence quotient. Monitoring of PAHs emitted by these cooking devices and fuels is critical to public health and sustainable pollution mitigation.
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    Insights into household fuel use in Kenyan communities
    (Elsevier, 2020-01-11) A, Osano; J, Maghanga; C. F, Munyeza; B, Chakaa; W, Olala; P. B.c, Forbes
    Clean household fuel use is a cornerstone of the development of sustainable cities, in order to minimisehousehold combustion emissions in communities and the negative air quality and human health impacts associatedwith this. In developing countries, factors determining fuel use are multi-faceted and complex. A surveywas thus conducted to better understand the current household fuel usage profile in four regions of Kenya;namely Bomet, Voi, Mombasa and Narok. The fuel use parameters investigated covered bio-data and economicstatus, dwelling type, fuel choice and usage, combustion devices and ventilation in kitchens. The fuel type usagewas distributed between firewood (25 %), charcoal (24 %), kerosene (24 %) and liquefied petroleum gas (LPG)(23 %). Three-stone stoves were still predominant in rural communities, whilst cleaner devices burning keroseneand LPG were used more widely in urban Mombasa. With the exception of Voi, there were more chimneys inurban dwellings than in the rural homes, even though brick houses were the most popular dwelling type overall(52 %). The results of this study will provide a useful basis for decision making regarding potential future cleanenergy intervention strategies in Kenya in order to promote sustainable development.
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    Effect of Formulation, Binder and Compaction Pressure of Rice Husk-Bagasse Briquettes on Thermal and Physical Properties
    (Journal of Scientific Research & Reports, 2020-12-31) Kerich, Daniel; Otara, Siagi; Ogola, Julius
    Aims: This study investigated the use of agro-wastes for the production of briquettes. It was carried out to investigate the effect of formulation, binder and compaction pressure of rice husk-Bagasse briquettes on thermal and physical properties. Study Design: The experimental design for this study was 6x5x2 Randomized Complete Block Design Place and Duration of the Study: Rice husks and bagasse were collected from Lake Basin Development Authority’s rice mill and Kibos sugar and Allied company respectively. The binders were sourced locally in Kisumu. The study was conducted between March 2019 and February 2020. The fabrication and laboratory analysis were carried out in the engineering and laboratory departments of Kenya Industrial Research and Development institute, Kisumu. Methodology: The experimental design for this study was 6x5x2 Randomized Complete Block Design. This study involved six formulations ratios (0:100, 20:80, 40:60, 60:40, 80:20, 100:0), five compaction pressure levels (108kPa, 180kPa, 253kPa, 325kPa, 397kPa) and two binders (clay, cassava) They were arranged in Randomize Complete Block Design with three replications per experiment. Results: The briquettes bulk density was in the range of 849 to 1001 kg.m−3, while the calorific value ranged from 5.541 kcal/g for 100% Rice husk clay binder to 7.345 kcal/g 20% Rice Husk cassava binder. Briquettes with blend ratio of 40-60% Rice Husk took longer time to burn. Briquette formulations with clay binder had burning rates ranging from 0.28 g/min to 0.15 g/min while with cassava binder from 0.52 g/min to 0.37 g/min. The ignition time of the briquettes ranged from 62 sec to 95 sec with cassava binder and 110 sec to 191sec with clay binder. The shatter index ranged from 0.94 to 0.99 with cassava and 0.9 to 0.98 with clay binder. Conclusion: Higher compaction pressures and use of cassava binder produced stronger briquettes with higher calorific values. Briquettes with higher percentage of bagasse had low ignition time and low bulk densities. The bulk densities and ignition time showed significant rise with increase in the compaction pressure but inversely affected the burning rate. The binder used significantly affected both the thermal and physical properties of all the formulations.
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    Optimization of the Performance of Hybrid Solar Biomass Dryer for Drying Maize Using ANSYS Workbench
    (Journal of Energy Research and Reviews, 2020-02-03) Aukah, Jackis; Muvengei, Mutuku; Ndiritu, Hiram; Onyango, Calvin
    In this paper ANSYS workbench was used to optimize the performance of hybrid solar biomass dryer for drying shelled maize in order to find the optimal operating input variables when the air temperature within the drying chamber set within the permissible range at reasonably high flow velocity. Hybrid Solar dryer with biomass as a source of fuel for auxiliary heating during absence or low solar insolation is a feasible option for small scale maize farmers [1]. At times high temperatures are induced in this dryer which may result in grain fissures and breakage during milling, thus reducing the grain quality. Optimization results indicate that in order to keep the air temperature within drying chamber to permissible range [2], the air velocity at collector inlet and biomass heat exchanger outlet should be improved to 3 m/s and 2.8 m/s respectively while the capacity of the biomass heat exchanger should also be enhanced to provide hot air at 85°C. It be concluded from the study that HSBD is suitable for drying maize as well as other agricultural products since continuous interrupted drying can be achieved. The capability of the dryer to maintain uniform temperature and air flow within the drying chamber enable high quality dried products within a short duration.
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    Quantifying Greenhouse Gas Emissions and Carbon Stocks in Maize-Soybean Cropping Systems in Siaya County, Kenya
    (Kenyatta University, 2020-11) Karanja, Anne Njeri
    As climate change continues to threaten ecosystems’ functions, agriculture remains one of the major source of greenhouse gas (GHG) emissions that are responsible for global warming. The major GHG in agriculture are; carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4). Unfortunately, agriculture is also one of the most affected sectors by climate change. There is therefore need to reduce emissions by adopting agricultural practices with mitigation potential. This is by enhancing soil carbon sequestration to offset emissions, or reducing emissions while safeguarding crop yields. However, little is still known about GHG quantities and intensities that major cropping systems in Kenya emmit. Site specific studies on GHG emissions to establish interventions for mitigation of climate change and enhanced crop production is therefore of essence. The objective of this study was to examine the effect of reduced tillage, crop residue retention and use of controlled release urea (CRU) in maize-soybean cropping systems on GHG emissions, soil N mineralization, organic carbon stocks and yields. Field measurements were carried out in a 13 year old researcher-managed trial in Siaya county, Kenya between March 2016 and January 2017. Four treatment combinations: ZT M-S NU (reduced tilage+maize soybean rotation+normal urea), ZT M-S CRU (reduced tillage+maize soybean rotation+controlled release urea), ZT M/S (reduced tillage+maize soybean intercrop without urea), CT M-S NU (Conventional tillage+maize soybean rotation+normal urea) were tested. The treatments were laid out in a randomized complete block design. DAYCENT model was used to simulate soil carbon, N2O emissions and maize yields. Results showed that daily fluxes of N2O ranged between -0.5-26 g ha-1 d-1 and -2-10 g ha-1 d-1 in the long and short rainy seasons respectively. Cumulatively, N2O emissions were between 0.2 - 0.7 kg ha-1 and 0.2 - 0.4 kg ha-1 in the long and short rainy seasons respectively. In the long rainy season, ZT M-S CRU had significantly higher N2O fluxes than the other treatments (P=0.05). In the short rainy season there were no significant effects of treatment on N2O emissions. In the long rainy season, CO2 daily fluxes were between 9 to 42 kg ha-1 while the cumulative emissions ranged between 2.5 to 2.8 t ha -1. In the short rainy season daily CO2 fluxes ranged between 6 to 30 kg ha-1 while cumulative emissions were 1.8- 2.5 t ha -1. There was no significant effect of treatment on CO2 emissions. Methane emissions were largely negative, and did not differ significantly among treatments. Yield was significantly low for ZT M/S but N2O emission intensities were not significantly different among treatments. DAYCENT simulated soil carbon and maize yield within the same ranges observed by measurement. N2O emissions by DAYCENT were higher during the peak of the seasons, but were comparable with observed measurements later in the seasons. Even though the long rainy season had higher N2O and CO2 emissions, the difference was not significant. These results indicate that emissions in the study area were low.These results further indicate that the current soil management practices in Siaya County influence GHG emissions, and the higher emissions observed with ZT M-S CRU in the long rainy season calls for further investigations of the effect of CRU on N2O emissions. The lower emission intensity shown by ZT M/S despite having lower yield points to the need of evaluating cropping systems for climate change mitigation and adaptation. These results indicated that DAYCENT model can be used to simulate soil carbon and yield but not N2O emissions in the study area.
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    Cost benefit analysis of different energy sources used in public secondary schools in Mtito Andei Division, Makueni County
    (South Eastern Kenya University, 2020-09-02) Kazungu, Arnold T.
    Energy affects all aspects of development: social, economic and environmental,including livelihoods, access to water, agricultural productivity, health, populationlevels and education. Public schools spend a lot of money every year on energy bills.Currently, they are experiencing an exponential increase in student enrolment whichputs more pressure on energy needs. This study focuses on cost benefit analysis ofdifferent energy sources used in public secondary schools in Mtito Andei Division,Makueni County. The specific objectives are to: (1) establish the sources of energyused in public secondary schools, (2) investigate the factors determining the choice ofthe energy source(s), (3) assess environmental and socio-economic impacts of majorenergy sources and (4) conduct cost benefit analysis of major energy sources. Thestudy used Survey Research Design (SRD) and a census survey, with all 30 schools inthe study site studied via questionnaire administration, observation, interview andphotography for data collection. Both descriptive and Benefit Cost Ratio analyticalprocedures were used. The study findings showed that firewood was the most popularcooking energy source with all (100%) schools using it while charcoal came second(23%) followed by LPG gas (10%) and paraffin (7%). Only 3% of the schools usedelectricity for cooking. The over reliance on firewood for cooking is expected to havenegative environmental consequences in the study area. Electricity was the mostpopular source of energy for lighting (60%) followed by solar energy (27%) andparaffin (7%). These are expensive sources of energy. An investigation into forms oflow cost energy technologies as perceived by the respondents revealed energy savingstoves (87%), solar power (27%) and energy saving bulbs (10%). The reasons foradoption of these energy technologies was mainly high cost of other energy sourcesand need to conserve the environment. The challenges associated with the differenttypes of energy identified were; electricity (unreliability), firewood (scarcity),charcoal (scarcity) and solar power (high installation cost). The study found firewoodconsumption was on average 10 tonnes per school per term and that firewood hadbeen used for cooking for more than 13 years on average in all schools in the studyarea. The study found the Benefit cost ratio (BCR) of solar power at 1.19 and BCR offirewood at 0.19. The study concludes that there was over reliance on firewood forcooking and adoption of modern energy technologies like solar power was very lowwith adoption by only 27% of schools. The study recommends: (1) the national andcounty governments to come up with policies such as subsidies, grants and tax reliefthat will make these technologies affordable and accessible to schools for adoption,(2) establishment of school-based woodlots consisting of fast-growing tree varieties toaddress the school wood fuel demands instead of escalating the destruction and loss ofindigenous forest ecosystems in the area, (3) since solar power has a BCR greater than1, the study recommends that schools should consider installing more of solar powerto reduce huge energy bills and to reduce over dependency on firewood.
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    Sustainable utilization of woodfuel in selected sites of Mwala Sub-county, Machakos County, Kenya
    (IJRES, 2017-01) Maingi, Luke N.; Kimiti, Jacinta M.; Kilungo, Julius K.
    Biomass energy provides 68% of Kenya’s national energy requirements and it is expected to remain the mainsource of energy for the foreseeable future (Mugo, F. and Gathui, T. (2010). The traditional stoves whichhappen to be very popular with most households wastes a lot of fuel due to its low energy efficiency and thisleads to negative environmental impacts such as deforestation and pollution. This study focused onunderstanding the sustainable utilization of woodfuel in two (2) Sub-locations of Mwala Sub-county namely:Mwala and Kibauni. The primary objective of this study was to determine if woodfuel utilization by thehouseholds in the study areas is sustainable. The specific objective of the study was to establish the level ofadoption of the energy saving techniques in the selected sub-locations. This study used survey methodology andobservation to collect data. The total household sample size was 160. Data collection instrument wasquestionnaires. Data was analyzed using descriptive statistics and inferential statistics and the software wasStatistical Package for Social Sciences (SPSS) version 23.0. The study revealed low adoption of rationing ofwood with majority of the respondents 84% in Kibauni and 65% in Mwala not practicing it. There wassignificant relationship between rationing of woodfuel and the number of days taken to consume a bundle ofwood (df=1 and 158, F=462.898, p=0.00 ). The study also revealed low adoption of splitting of wood with 70%of respondents in Mwala and 88% in Kibauni not doing the splitting. There was significant relationship betweensplitting of wood and pollution challenges ( df=1 and 158, F=28.456, p=0.00 ). Low adoption of the practice ofputting off fire after use was also revealed with 66% of respondents in Mwala and 80% in Kibauni not practicingit. The study revealed a significant relationship between putting off fire after use and the number of days taken toconsume one bundle of wood (df=3 and 156, F=57.292, p=0.00.). It was also found out that there was nosignificant relationship between the type of stove and pollution challenges (df=1 and 158, F=0.072, p=0.789).The study recommended that aggressive campaign in dissemination of improved stoves and related technologyin order to reduce pressure on forests, the Government to have a structured management in production ofcharcoal and fuel wood by small scale farmers so as to have a source of income, promote capacity of fieldextension staff in the energy sector and establish an Energy Centres in the Sub-county to help disseminateknowledge and materials related to energy conservation.
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    Power Quality Assessment of Renewable Energy Sources Integration on MV Networks.
    (INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH, 2019-10-10) Itote, Francis; Irungu, George; Saulo, Michael
    The amount of energy harnessed from Renewable energy sources (RES) is constantly increasing. This rise can be attributed to technological advancement that has lowered generation costs, financing from governments and private sector, efficient payment plans (e.g. Pay As You Go), and need for clean energy. RES are either integrated into the local distribution grids or used as standalone/off grid solutions that facilitate easy energy access to meet the ever-increasing power requirements. Extensive studies on the behavior of power networks integrated with RES is therefore required so as to facilitate the changes that will be made on the current grid configuration. This study assessed the impact on the harmonics and flicker of distributed networks due to the integration of wind and solar energy sources. To achieve this, the IEEE-33 bus system was integrated with RES at selected locations and power quality and harmonic analysis performed using DigSILENT PowerFactory software. Results obtained indicate increased harmonic and flicker levels of distribution networks. The levels of harmonic distortion and flicker obtained were found to be reliant on the type, penetration level and installation patterns of RES.
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    Factors influencing use of multipurpose trees and shrubs in arid and semiarid lands of Kenya
    (Elsevier, 2021-01) Kisangau, Patrick D.; Kimiti, Jacinta M.; Mburu, Mary W. K.; Snelder, Denyse J.
    Multipurpose trees and shrubs are vital components of arid and semiarid ecosystems. They offer both regulatory and production services, yet there is inadequate information on their actual use and factors affecting utilization of these plant resources. A study was carried out in three agroecological zones (counties) of southeastern Kenya: Machakos (subhumid zone), Kajiado (semiarid zone), and Kitui (arid zone). The research objective was to assess the local uses of multipurpose trees and shrubs and determine how socioeconomic factors (gender, type of occupation, and education level) influenced their use. A field survey was conducted along a 324-km transect across the three agroecological zones. Data were collected from 196 respondents using focus group discussions, key informants, and individual household questionnaires. A total of 86 plant species belonging to 47 plant families were recorded. The Mann-Whitney U-test revealed that women significantly used a higher number of different plant species than men (P < 0.05). The level of education and type of occupation also significantly affected plant use (P < 0.05), with subsistence farmers having primary or no formal education, reporting the highest number of species. Fifteen plant-use categories comprising production and service provision were identified. Plant species use-value index (UVI) revealed 10 indigenous and wild woody species of high value in the study area. Acacia tortilis (Forssk.) Hayne had the highest UVI of 0.33, followed by Commiphora africana (A. Rich.) Engl. (0.17), Terminalia brownii Fres. (0.13), and Zanthoxylum chalybeum Engl. (0.12). There was a significant positive correlation between the reporting frequency for woody species and the overall UVI (P < 0.05). Economic development, climate change, and land use changes jeopardize distribution, utilization, and knowledge preservation of multipurpose woody species. There is a need for monitoring and adoption of gender-sensitive strategies for their sustainable utilization in order to safeguard these unique plant resources from degradation and overexploitation.
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    Estimating On-Road Vehicle Fuel Economy in Africa: A Case Study Based on an Urban Transport Survey in Nairobi, Kenya
    (MDPI, 2019-03-26) Mbandi, Aderiana Mutheu; Böhnke, Jan R.; Schwela, Dietrich; Vallack, Harry; Ashmore, Mike R.; Emberson, Lisa
    In African cities like Nairobi, policies to improve vehicle fuel economy help to reduce greenhouse gas emissions and improve air quality, but lack of data is a major challenge. We present a methodology for estimating fuel economy in such cities. Vehicle characteristics and activity data, for both the formal fleet (private cars, motorcycles, light and heavy trucks) and informal fleet—minibuses (matatus), three-wheelers (tuktuks), goods vehicles (AskforTransport) and two-wheelers (bodabodas)—were collected and used to estimate fuel economy. Using two empirical models, general linear modelling (GLM) and artificial neural network (ANN), the relationships between vehicle characteristics for this fleet and fuel economy were analyzed for the first time. Fuel economy for bodabodas (4.6 ± 0.4 L/100 km), tuktuks (8.7 ± 4.6 L/100 km), passenger cars (22.8 ± 3.0 L/100 km), and matatus (33.1 ± 2.5 L/100 km) was found to be 2–3 times worse than in the countries these vehicles are imported from. The GLM provided the better estimate of predicted fuel economy based on vehicle characteristics. The analysis of survey data covering a large informal urban fleet helps meet the challenge of a lack of availability of vehicle data for emissions inventories. This may be useful to policy makers as emissions inventories underpin policy development to reduce emissions.
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    Energy Characteristics of Five Indigenous Tree Species at Kitulangalo Forest Reserve in Morogoro, Tanzania
    (INTERNATIONAL JOURNAL of RENEWABLE ENERGY RESEARCH, 2014-11-29) Warburg, Christopher T; King’ondu, Cecil K
    This study presents the investigation of material composition and energy characteristics of B. spiciformis, B. boehmii, C. molle, P. maprouneifolia, and S. birrea indigenous tree species at kitulangalo forest reserve in Tanzania. Energy content of each species mostly depends on its chemical content (C, H and O) and it is reduced by inorganic elements and moisture. Biomass chemical composition was done by proximate and ultimate analyses. Regarding the elemental composition, P. maprouneifolia and C. molle had high energy content of 18.62 and 18.30 MJ/Kg, respectively because of their higher H:C ratio and relatively low O:C ratio. Carbon, oxygen, and hydrogen were found to be highest in P. maprouneifolia with 46.71, 41.96, and 5.7%, respectively. In contrast, P. maprouneifolia had the lowest N:C ratio of 0.014, implying good efficiency for nitrogen use to fix carbon. On the other hand, ash, moisture, and volatiles were highest at 4, 55, and 85% for S. birrea, B. spiciformis, and S. birrea, correspondingly. The ratio of macronutrients to carbon for each species was also calculated. Results show that all species have high demand for nitrogen followed by potassium and calcium, in that order. Finally, heating values have been shown to decrease with increasing moisture content. These experimental results were used for ranking these biomass materials for energy generation. They also furnish vital biomass information for equipments and process designers.
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    Assessment of the implementation of energy conservation opportunities arising from energy audits; A study of four-star and five-star hotels in Nairobi Kenya
    (Scientific Research Publishing, 2023-09-26) Ogola, Nicholas; Musau, Peter M.; Wekesa, Cyrus
    This study assesses the implementation of energy conservation opportunities in four-star and five-star hotels in Nairobi. The Covid-19 pandemic had a significant impact on the Hospitality Industry. Currently, there is a growing inclination to furnish guests with superior and sustainable services in an energy-efficient and eco-friendly way. Comprehensive research was conducted from energy audits gathered from the establishments and contracted auditing companies, on top of this, hotel staff were given digital questionnaires. To add to the data, the researcher surveyed the hotels with engineering managers. The Energy Audits found that all 10 hotels had adopted Energy Conservation Opportunities (ECOs). After further analysis, the mean adoption rate of Energy Conservation Opportunities (ECOs) during the past three years was 55.83%, which was below the aim of 100%. According to studies, hotel staff manages energy to cut costs. The researcher found that hotels use up a lot of energy. However, they have conservation potential, depending on government policies, costs, ease of implementation, and management commitment to sustainable practices. Essentially, Energy Conservation Opportunities (ECOs) reduce energy expenditures and boost reliable revenues, especially during high energy prices and uncertainty.
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    Enhancement of anaerobic digestion by co-digesting food waste and water hyacinth in improving treatment of organic waste and bio-methane recovery
    (Elsevier Ltd, 2022-09-01) Oduor, William W.; Wandera, Simon M.; Murunga, Sylvia I.; Raude, James M.
    In Kenya, 57% of the municipal solid waste generated is Food waste (FW) which has high organic content. However, the treatment and bioconversion of FW to biogas have always been challenging due to its rapid biodegradation, resulting from rapid hydrolysis and accumulation of volatile fatty acids and lowering pH in the bioreactor. In this study, the anaerobic digestibility of FW as a mono substrate was compared to co-digestion of FW with water hyacinth (WH) for improved biogas production and organic matter removal efficiency in a laboratory batch reactor. Different mix proportions of FW and WH were co-digested under mesophilic conditions (37 °C) at a dilution of 6% (w/v) Total Solids (TS) content. The TS of the substrates (Food waste and Water Hyacinth) were pre-processed to have a concentration of TS at 6% (60 g/L) to operate a wet AD which requires the substrate to be less than 15% TS. The proportions of WH: FW (v/v) were 100:0, 85:15, 70:30, 55:45, 30:70, 15:85, and 0:100. In the batch rectors the anaerobic co-digestion was conducted with Substrate to Inoculum (S/I) ratio of 1:1. FW is generally considered to have high volatile solids which hydrolyze rapidly lowering pH arising from excess production of Hydrogen which in presence of CO2 and acetogenic bacteria leads to more production of acetate, formate and other long chain fatty acids which inhibits methanogenesis as a result of rapid acidification. The rapid acidification of the bioreactors that are used to treat FW results in the inhibition of the methanogenesis process. The co-digestion of the substrates could have improved the process parameters by reducing acidity caused by the high C/N ratio, reducing the inhibitory range, and increasing the buffer capacity which enhanced the bio-methane potential and the microbial activity. The batch experiments were set in triplicate for both cases of FW, WH, mixtures, and Inoculum. The results showed that the average gas yields after 81 days for the various mix proportions were 256.27and 357.69 ml/g-VS for mono-digestion of WH and FW respectively. For the mixtures of WH: FW the average reported biogas production were 305.01, 280.27, 548.91,616.01 and 270.87 ml/g-VS for mixtures of 15:85, 30:70, 55:45,70:30 and 85:15 respectively. The modified Gompertz model showed that the digesters with WH and FW alone had lag times of 2.599 and 1.052 days respectively. The mix substrates of WH: FW 85:15, 70:30, 55:45, 30:70 and 15:85 shown lag times of 2.456, 3.777, 2.574, 1.956 and 1.75 days respectively. A mix (WH: FW) of 70:30 had the highest maximum specific biogas production Rmax and the maximum biogas production potential of 18.19 mlCH4/gVS per day and 607.7mlCH4/gVS respectively. The R2 and RSME values ranged from 0.9867 to 0.9963 and 2.663 to 9.359 respectively in all the digesters. The study shows that the co-digestion of WH and FW in the mix ratio of 70:30 improved the volume of biogas produced and organic matter removal efficiency reached 79%.