Energy

Permanent URI for this community

https://repository.nrf.go.ke/handle/123456789/10

Browse

Now showing 1 - 20 of 34

A Review of the Current Trends in the Production and Consumption of Bioenergy
(Sami Publishing Company, 2021-02-01) Korir, Benjamin K.; Kibet, Joshua; Mosonik, Bornes C.
With the current traditional fossil fuels depleting at an alarming rate coupled with environmental degradation because of toxic emissions, there is a mounting desire in search of renewable and sustainable energy resources. In this regard, bioenergy is considered one of the greatest potential to address the global energy demands in order to foster confidence in energy security, economic sustainability, and environmental protection. Global use of biomass to generate electricity and enhanced green energy transport is expected to increase in the near future. Accordingly, the demand for renewable energy is aimed at minimizing energy poverty and mitigation against climate change. Bioenergy despite bioconversion challenges is one of the key solutions to the world’s current energy demands. Model bioenergy plant sources – Croton megalocarpus, palm oil, Jatropha, and soybeans are briefly discussed in this review as major sources of bioenergy. The increased focus on bioenergy has been necessitated by high oil and gas prices, and the desire for sustainable energy resources. Nonetheless, corrupt practices and lack of political goodwill has hampered efforts towards achieving the full utilization of bioenergy. Corruption has been widely cited as a major setback to bioenergy development in a range of global jurisdictions. In order to minimize environmental damage, carbon trade has been projected as a necessary action by developing countries to reduce carbon emissions. Generally, the analysis of the use of fossil fuels across the world shows a strong interrelationship involving energy utilization, degradation of air quality, and environmental health concerns.
A Review of the Current Trends in the Production and Consumption of Bioenergy
(Sami Publishing Company(SPC), 2021) Korir, Benjamin K.; Kibet, Joshua; Mosonik, Bornes C.
With the current traditional fossil fuels depleting at an alarming rate coupled with environmental degradation because of toxic emissions, there is a mounting desire in search of renewable and sustainable energy resources. In this regard, bioenergy is considered one of the greatest potential to address the global energy demands in order to foster confidence in energy security, economic sustainability, and environmental protection. Global use of biomass to generate electricity and enhanced green energy transport is expected to increase in the near future. Accordingly, the demand for renewable energy is aimed at minimizing energy poverty and mitigation against climate change. Bioenergy despite bioconversion challenges is one of the key solutions to the world’s current energy demands. Model bioenergy plant sources – Croton megalocarpus, palm oil, Jatropha, and soybeans are briefly discussed in this review as major sources of bioenergy. The increased focus on bioenergy has been necessitated by high oil and gas prices, and the desire for sustainable energy resources. Nonetheless, corrupt practices and lack of political goodwill has hampered efforts towards achieving the full utilization of bioenergy. Corruption has been widely cited as a major setback to bioenergy development in a range of global jurisdictions. In order to minimize environmental damage, carbon trade has been projected as a necessary action by developing countries to reduce carbon emissions. Generally, the analysis of the use of fossil fuels across the world shows a strong interrelationship involving energy utilization, degradation of air quality, and environmental health concerns.
Ab Initio Study of Structural and Vibrational Properties of Fe2P-Type Materials for Near - Room - Temperature Refrigeration
(Science and Education publishing (SciEP), 2022-01-23) Thirika, Anne Mwende; Mulwa, Winfred Mueni; Makau, Nicholus Wambua; Ibrahim, Adentuji Bamidele
This work has applied density functional theory (DFT) based calculations to investigate the structural and vibrational properties of FeMnP1−xAx (A= Si, Se, Sn and In, x = 0.33) within the first-principles pseudopotential technique. The exchange correlation potentials were treated within generalized gradient approximation (GGA), in the Quantum ESPRESSO code. The Perdew, Burke, Ernzerhof (PBE) functional as implemented in Vanderbilt's ultra-soft pseudo potential (USPP) was used for all the calculations. Vibrational properties were calculated using phonopy code with 1 × 1 × 2 supercell of the conventional unit cell. Thermodynamic properties were predicted using the phonon density of states. The dependence of lattice thermal conductivity on temperature was determined using Debye theory. The optimized structural parameters and corresponding graphical values fit within available experimental data and other theoretical reports. There were no imaginary phonon modes in the phonon dispersion curves revealing that these materials are dynamically stable for magnetic refrigeration.
Dioxin and dibenzofuran like molecular analogues from the pyrolysis of biomass materials—the emerging challenge in bio-oil production
(BMC Chemistry, 2021-01-15) Kirkok, Samuel K.; Kibet, Joshua K.; Kinyanjui, Thomas; Okanga, Francis I.; Nyamori, Vincent O.
Introduction The aggressive search for renewable energy resources and essential pyrosynthetic compounds has marked an exponential rise in the thermal degradation of biomass materials. Consequently, clean and sustainable transport fuels are increasingly desirable in a highly industrialized economy, for energy security and environmental protection. For this reason, biomass materials have been identified as promising alternatives to fossil fuels despite the challenges resulting from the possible formation of toxic nitrogen-based molecules during biomass degradation. In order to understand the free radical characteristic challenges facing the use of bio-oil, a brief review of the effects of free radicals in bio-oil is presented. Methodology Pyrolysis was conducted in a tubular flow quartz reactor at a residence time of 2 s at 1 atm. pressure, for a total pyrolysis time of 5 min. The thermal degradation of biomass components was investigated over the temperature range of 200 to 700 °C typically in 50 °C increments under two reaction conditions; pyrolysis in N2 and oxidative pyrolysis in 5% O2 in N2. The pyrolysate effluent was analysed using a Gas chromatograph hyphenated to a mass selective detector (MSD). Results The yield of levoglucosan in the pyrolysis of cellulose in the entire pyrolysis temperature range was 68.2 wt % under inert conditions and 28.8 wt % under oxidative conditions. On the other hand, formaldehyde from pyrolysis of cellulose yielded 4 wt % while that from oxidative pyrolysis was 7 wt % translating to ⁓ 1.8 times higher than the yield from pyrolysis. Accordingly, we present for the first time dioxin-like and dibenzofuran-like nitrogenated analogues from an equimassic pyrolysis of cellulose and tyrosine. Levoglucosan and formaldehyde were completely inhibited during the equimassic pyrolysis of cellulose and tyrosine. Conclusion Clearly, any small amounts of N-biomass components such as amino acids in cellulosic biomass materials can inhibit the formation of levoglucosan–a major constituent of bio-oil. Overall, a judicious balance between the production of bio-oil and side products resulting from amino acids present in plant matter should be taken into account to minimize economic losses and mitigate against negative public health concerns.
Effect of Compacting Pressure on Fuel Properties of Finger Millet Briquettes
(International Institute for Science, Technology and Education (IISTE), 2017-11) Ayub, Hesborn R.
In this work, the effect of compacting pressure on fuel properties of finger millet briquettes was investigated and reported. Four different varieties of finger millet namely P224, Gulu-E, U-15 and Okhale-1 were used to produce briquettes without a binder using manual hydraulic press at predetermined compacting pressure of 15, 25 and 35MPa. The proximate analysis results of the resultant briquettes was between 68-70% volatile matter, 21-24% fixed carbon, 9-11% moisture content and 7-8% ash content which is comparable with those of other biomass materials such as rice, wheat and wood. On the effect of compacting pressure on fuel properties, the study showed an increasing trend in briquette density and compressive strength as compacting pressure increased from 15 to 35MPa. However, as compacting pressure increased, the burning rate decreased due to reduced air voids in the briquettes thus limiting mass and heat transfer during combustion.
Effect of Process Techniques on Three Feedstocks Mix on Briquette Performance Properties
(Journal of Energy, Environmental & Chemical Engineering, 2022-02-16) Okwara, Wilberforce; Nyaanga, David; Aguko, Kabok; Nyaanga, Jane
Energy availability at domestic level is a challenge across the world and especially in Africa. Firewood is the major source of energy for cooking for households in Kenya and there is need for a friendly sustainable environmental fuel. Carbonized biomass materials (briquettes) are considered a substitute. This study thus evaluated effect of selected briquetting techniques on briquettes’ performance properties. Milled charcoal dusts mixed in a ratio of 1:1:1 (Rice husk, maize cob, and sugarcane bagasse) with molasses binder in the ratio of 6:1 was hence ready for densification and agglomeration. The Water Boiling Test was used in determination of the briquette’s performance characteristics for various parameters. High (screw press); and low (drum agglomerator and hand making) pressure briquetting techniques were distinctly different in ignition time (minutes), time to boil (minutes) burning rate (g/min), specific fuel consumption (g/ml) and power output (kW) values as (4, 3, 3; 14, 12, 11: 0.8, 1.1, 1.3; 0.11, 0.13, 0.15; and 1.8, 1.4, 0.75). Diversified briquetting techniques, number and type of feedstocks are thus factors that influence performance characteristics of briquettes in converting the agricultural and or other wastes for useful energy application. This knowledge should enable users to make choices on techniques for optimum efficiency towards realization of Sustainable Development Goal Number #7 on affordable and clean energy.
Effect of Process Techniques on Three Feedstocks Mix on Briquette Performance Properties
(2022) Okwara, Wilberforce; Nyaanga, Daudi; Kabok, Peter; Nyaanga, Jane
Energy availability at domestic level is a challenge across the world and especially in Africa. Firewood is the major source of energy for cooking for households in Kenya and there is need for a friendly sustainable environmental fuel. Carbonized biomass materials (briquettes) are considered a substitute. This study thus evaluated effect of selected briquetting techniques on briquettes’ performance properties. Milled charcoal dusts mixed in a ratio of 1:1:1 (Rice husk, maize cob, and sugarcane bagasse) with molasses binder in the ratio of 6:1 was hence ready for densification and agglomeration. The Water Boiling Test was used in determination of the briquette’s performance characteristics for various parameters. High (screw press); and low (drum agglomerator and hand making) pressure briquetting techniques were distinctly different in ignition time (minutes), time to boil (minutes) burning rate (g/min), specific fuel consumption (g/ml) and power output (kW) values as (4, 3, 3; 14, 12, 11: 0.8, 1.1, 1.3; 0.11, 0.13, 0.15; and 1.8, 1.4, 0.75). Diversified briquetting techniques, number and type of feedstocks are thus factors that influence performance characteristics of briquettes in converting the agricultural and or other wastes for useful energy application. This knowledge should enable users to make choices on techniques for optimum efficiency towards realization of Sustainable Development Goal Number #7 on affordable and clean energy.
Exhaust Gases Energy Recovered from Internal Combustion Engine for Useful Applications
(IOSR Journal of Mechanical and Civil Engineering, 2017-06-01) Orido, George; Ngunjiri, Prof; Rugiri, Musa
Abstract : The importance of this study is primarily to address the energy problem. The main contribution of this study, in addition to conserving energy through recovery technique, is reduction in the impact of global warming due to exhaust gas emission to the environment. The objective of the research is to recover exhaust gases energy from internal combustion engines for utilization. The experimental set-up consisted of a single cylinder, four-stroke, multi-fuel engine connected to eddy current dynamometer for loading. Thermocouple temperature sensors and transmitters were used to measure exhaust gas to calorimeter inlet temperature and exhaust gas from calorimeter outlet temperature. Exhaust gas mass flow rate and temperature measurements were used to determine the recovered energy. Recovered heat energy was 1.257% of fuel energy when the engine was operated on diesel at 1000 rpm and a torque load of 18 Nm. 3.153% of fuel energy was recovered at 1500 rpm and a torque load of 6 Nm when biodiesel was used. At a speed of 1000 rpm 22.6% and 23.004% of the thermal energy through exhaust was recovered when the engine used diesel and biodiesel at torque loads of 6 Nm and 14 Nm respectively.
Free radicals and ultrafine particulate emissions from the co-pyrolysis of Croton megalocarpus biodiesel and fossil diesel
(Springer Nature, 2018-08-07) Kibet, Joshua K.; Mosonik, Bornes C.; Nyamori, Vincent O.; Ngari, Silas M.
BackgroundThe atmosphere has become a major transport corridor for free radicals and particulate matter from combustion events. The motivation behind this study was to determine the nature of particulate emissions and surface bound radicals formed during the thermal degradation of diesel blends in order to assess the health and environmental hazards of binary transport fuels.MethodologyAccordingly, this contribution explored the interactions that occur when Croton megalocarpus biodiesel and fossil diesel in the ratio of 1:1 by weight were co-pyrolyzed in a quartz reactor at a residence time of 0.5 s under an inert flow of nitrogen at 600 °C. The surface morphology of the thermal char formed were imaged using a Feld emission gun scanning electron microscope (FEG SEM) while Electron paramagnetic resonance spectrometer (EPR) was used to explore the presence of free radicals on the surface of thermal char. Molecular functional groups adsorbed on the surface of thermal char were explored using Fourier transform infrared spectroscopy (FTIR).ResultsFTIR spectrum showed that the major functional groups on the surface of the char were basically aromatic and some methylene groups. The particulate emissions detected in this work were ultrafine (~ 32 nm). The particulates are consistent with the SEM images observed in this study. Electron paramagnetic resonance results gave a g-value of 2.0027 characteristic of carbon-based radicals of aromatic nature. Spectral peak-to-peak width (∆Hp-p) obtained was narrow (4.42 G).ConclusionsThe free radicals identified as carbon-based are medically notorious and may be transported by various sizes of particulate matter on to the surface of the human lung which may trigger cancer and pulmonary diseases. The nanoparticulates determined in this work can precipitate severe biological health problems among humans and other natural ecosystems.
Germanium quantum dot/nitrogen-doped graphene nanocomposite for high-performance bulk heterojunction solar cells
(Royal Society of Chemistry, 2018-06-30) Amollo, Tabitha A.; Mola, Genene T.; Nyamori, Vincent O.
This study presents the successful synthesis of a novel nanocomposite, namely a germanium quantum dot/nitrogen-doped graphene nanocomposite (GeQD/NGr), and its use in the modification of the photoactive medium of bulk heterojunction solar cells (BHJ-SCs). The nanocomposite was prepared in two sequential steps. Firstly, a reduced graphene oxide-germanium oxide nanocomposite (rGO-GeO2) was synthesized by microwave-assisted solvothermal reaction. The second step involved simultaneous N-doping of graphene and reduction of GeO2 to obtain the GeQD/NGr nanocomposite by thermal treatment. The nanocomposite consists of highly crystalline, spherical shaped GeQDs with a mean diameter of 4.4 nm affixed on the basal planes of NGr sheets. Poly-3-hexylthiophene (P3HT), (6-6)phenyl-C60-butyric acid methyl ester (PCBM) and GeQD/NGr were used as the photoactive layer blend in the fabrication of BHJ-SCs. Enhanced short-circuit current density (Jsc) and fill factor (FF) is derived from the incorporation of the GeQD/NGr nanocomposite in the active layer. The nanocomposite in the active layer blend serves to ensure effective charge separation and transportation to the respective electrodes. Consequently, an improvement of up to 183% in the power conversion efficiency is achieved in the BHJ-SCs by the GeQD/NGr modification.
Improved short-circuit current density in bulk heterojunction solar cells with reduced graphene oxide-germanium dioxide nanocomposite in the photoactive layer
(Elsevier, 2020) Amollo, Tabitha A.; Mola, Genene T.; Nyamori, Vincent O.
In the quest to improve the optical absorption and electrical transport of poly-3-hexylthiophene (P3HT) and (6-6) phenyl-C61-butyric acid methyl ester (PCBM) blend film, reduced graphene oxide-germanium dioxide nanocomposite (rGO-GeO2) was employed in the photoactive layer of thin film organic solar cells. Bulk heterojunction solar cells (BHJ SCs) with rGO-GeO2 composite in the active layer exhibited an increase in power conversion efficiency (PCE) of up to 53%. Significant improvement in the measured photocurrent is achieved by the incorporation of rGO-GeO2 in the active layer. High short-circuit current density (Jsc) of up to 17 mA/cm2 is attained in the BHJ SCs. The high Jsc shows that the inlay of rGO-GeO2 in the active layer facilitates exciton separation and creates percolation pathways for charge transport to the electrodes. Charge separation is energetically favoured by a built-in potential difference between the donor and acceptor phases of the active layer. Hence, the incorporation of rGO-GeO2 composite in the active layer improves its charge photogeneration, separation and transport to yield high Jsc and enhanced PCE.
Improved short-circuit current density in bulk heterojunction solar cells with reduced graphene oxide-germanium dioxide nanocomposite in the photoactive layer
(Elsevier, 2020-11) Amollo, Tabitha A.; Mola, Genene T.; Nyamori, Vincent O.
In the quest to improve the optical absorption and electrical transport of poly-3-hexylthiophene (P3HT) and (6-6) phenyl-C61-butyric acid methyl ester (PCBM) blend film, reduced graphene oxide-germanium dioxide nanocomposite (rGO-GeO2) was employed in the photoactive layer of thin film organic solar cells. Bulk heterojunction solar cells (BHJ SCs) with rGO-GeO2 composite in the active layer exhibited an increase in power conversion efficiency (PCE) of up to 53%. Significant improvement in the measured photocurrent is achieved by the incorporation of rGO-GeO2 in the active layer. High short-circuit current density (Jsc) of up to 17 mA/cm2 is attained in the BHJ SCs. The high Jsc shows that the inlay of rGO-GeO2 in the active layer facilitates exciton separation and creates percolation pathways for charge transport to the electrodes. Charge separation is energetically favoured by a built-in potential difference between the donor and acceptor phases of the active layer. Hence, the incorporation of rGO-GeO2 composite in the active layer improves its charge photogeneration, separation and transport to yield high Jsc and enhanced PCE.
Improved short-circuit current density in bulk heterojunction solar cells with reduced graphene oxide-germanium dioxide nanocomposite in the photoactive layer
(Elsevier, 2020-11) Amollo, Tabitha A.; Mola, Genene T.; Nyamori, Vincent O.
In the quest to improve the optical absorption and electrical transport of poly-3-hexylthiophene (P3HT) and (6-6) phenyl-C61-butyric acid methyl ester (PCBM) blend film, reduced graphene oxide-germanium dioxide nanocomposite (rGO-GeO2) was employed in the photoactive layer of thin film organic solar cells. Bulk heterojunction solar cells (BHJ SCs) with rGO-GeO2 composite in the active layer exhibited an increase in power conversion efficiency (PCE) of up to 53%. Significant improvement in the measured photocurrent is achieved by the incorporation of rGO-GeO2 in the active layer. High short-circuit current density (Jsc) of up to 17 mA/cm2 is attained in the BHJ SCs. The high Jsc shows that the inlay of rGO-GeO2 in the active layer facilitates exciton separation and creates percolation pathways for charge transport to the electrodes. Charge separation is energetically favoured by a built-in potential difference between the donor and acceptor phases of the active layer. Hence, the incorporation of rGO-GeO2 composite in the active layer improves its charge photogeneration, separation and transport to yield high Jsc and enhanced PCE.
Investigating the Effect of Selected Parameters on Moisture Removal Rate of an Experimental Forced Convection Solar Grain Dryer
(Scientific & Academic Publishing, 2018) Osodo, Booker; Nyaanga, Daudi
Although forced convection solar grain dryers achieve greater drying rates than natural convection dryers, optimum air velocity, grain layer thickness and drying air temperatures are necessary for improved performance. Number of trays used also affects performance. This study investigated the moisture removal rate (ratio of mass of moisture removed to mass of wet grain per hour) of a solar grain under different drying conditions. The effect of air velocity, layer thickness, number of trays and temperature on moisture removal rate (MRR) was investigated. MRR increased with increase in both drying air velocity and temperature at constant layer thickness. For 0.02 m thickness, MRR increased from 0.048 to 0.061 kg moisture / (kg wet grain. hour). However this increase was only significant at lower temperatures (below 45°C). Changing from 40 to 45°C caused a significant increase, but increasing temperature above 45°C did not. Also, MRR decreased with increase in layer thickness at constant air velocity. At 0.408 m/s air velocity, as layer thickness increased from 0.02 to 0.08 m, MRR decreased from 0.061 to 0.022 kg moisture / (kg wet grain. hour). Finally, when drying a given layer thickness, use of two trays did not significantly improve MRR.
Investigation of magnetic properties of FeMnP1-xAx (A = In, Se and Sn, where x = 0.33) by use of GGA functionals
(Elsevier, 2021-07) Vincent, Otieno; Mulwa, Winfred Mueni; Kirui, M. S. K.
Magnetic properties of stable iron-based compounds (FeMnP1-xAx (A = Si, In, Se and Sn) were investigated by use of Quantum Espresso (QE) within the Density Functional Theory (DFT) formalism as a viable magnetic refrigerant. In this research work, DFT technique was the first principle theoretical approach that was employed along with the planewave pseudopotentials (ultrasoft), and the projected augmented wave (PAW) within the generalized gradient approximation (GGA) to describe the electronic structure and investigation of magnetic properties. Magnetic stability is described as the repeated magnetic performance of a material under specific conditions over the life of a magnet. In this case our reference compound, FeMnP0.67 Si0.33 was optimized and its properties were examined in both ferromagnetic (FM) and antiferromagnetic (AFM) states. Two Si atoms were later substituted with atoms of post-transitional metals in period four and five which has shown first-order magnetic transition at near room temperatures. In, Se and Sn were chosen to replace silicon since they would easily mimic the bond, their availability and nontoxic nature. The results showed that only ferromagnetic states of both host and doped compounds gave promising magnetic properties that can be applied in magnetocaloric effect phenomenon. Their band structure results indicated that they were all metals. Antiferromagnetic states showed no magnetic properties as the spin-polarized graph resulted in perfect symmetry of spin up projected density of states (PDOS) and spin down PDOS. From the thermo_pw calculations, it was realized that FeMnP0.67 In0.33 is the best candidate for near room temperature magnetic refrigeration among the studied compounds.
Knowledge and Awareness Determinants of Renewable Energy Technologies: A Cross Sectional Study of Rural Residents from Njoro Constituency, Nakuru County, Kenya
(IOSR Journal of Environmental Science Toxicology and Food Technology, 2020-09-03) Kimani, Martin Njoroge; Makindi, Stanley Maingi; Aboud, Abdillahi A.
Background:Awareness to renewable energy technologies (RET) can have multiple positive effects as it can be a precursor to greater RET adoption levels as well as promotion of the same. The aim of this study was to assess the level of awareness of rural residents of Njoro constituency to the different renewable energy technologiesas a precursor to their adoption. Materials and Methods: The study was based on primary data collected through personal interviews with household heads in Njoro constituency, Nakuru County, Kenya. Two stage cluster random sampling was used to select the 200 households. The results showed that majority of the respondents exhibited a moderate level of knowledge and awareness to RETs. Results:Results of the study indicated that gender and education level had a significant effect on knowledge and awareness. It was also found that age and social-economic status did not have significant effect on the knowledge and awareness. Conclusion:The overall finding of the study underlined the high importance in strengthening communication to enhance knowledge and awareness of renewable energy technologies. The findings of this study will be significant to planners, policy makers, researchers and individuals to build the case for proactive promotion of RETS. Key Word:Knowledge and awareness; renewable energy technologies; rural househol
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.
Organic solar cells: Materials and prospects of graphene for active and interfacial layers
(Taylor & Francis group, 2019-06-26) Amollo, Tabitha A.; Mola, Genene T.; Nyamori, Vincent O.
Photovoltaics is a portentous alternative to the nonrenewable energy resources. Organic solar cells (OSCs) offer several advantages over inorganic counterparts in terms of low-cost device production, simple solution-based processing, flexibility, light-weight and compatibility with roll-to-roll fabrication. This review comprehensively examines the latest research developments towards high-performance OSCs. Device processing conditions and engineering along with material developments for the active and interfacial layers are examined. Different device structures and their benefits and limitations are highlighted. The interfacial layer materials including the polymers and metal oxides together with their integration and performance in functional OSCs are examined. A salient aspect of this review is the design of donor and acceptor materials to address the optical and electronic properties requirement for optimized device efficacy of OSCs. In this regard, the prospects of tailoring the band gap of donor polymers alongside the adoption of non-fullerene acceptors with complementary optical absorption for improved solar energy harvesting is elucidated. Further, graphene’s feasibility as an active or interfacial layer material is reviewed. Hence, this article provides perspectives and strategies on further development of solution-processable donor, acceptor and interfacial materials for high efficiency devices, required in commercialization of OSCs.
Performance of an experimental biomass micro gasifier cook stove
(Egerton University, 2018-10) Wamalwa, Patrick Wafula
Most stoves based on the principle of micro gasification have improved thermal efficiencies with low emissions, however, knowledge on the effect of the stove operation at different air flow rates on thermal efficiency, fire power, emissions, specific fuel consumption and burning rate is scarce. The main objective of this research was to evaluate performance a micro gasifier cook stove. An experimental forced draft cook stove was therefore developed using the available materials based on the design equations and household energy requirements. Simulation of air flow was integrated to help in the selection of the fan. The water boiling test was used and carried out at volumetric air flow rates of 0.014 m3s-1, 0.020 m3s-1, 0.027 m3s-1 and 0.034 m3s-1 with three replications. Performance was based on carbon dioxide, carbon monoxide, particulate matter, temperature near the pot and time for boiling water recorded real time. The average thermal efficiency and boiling time were 33±4%, and 13.5±3 minutes, respectively. There was linear proportionality for variation of air flow rate with the fire power of the stove in both cold and hot phases. The resistance to airflow exerted by the fuel and by the char inside the reactor during gasification was an average of 0.125 cm of water which was the minimum resistance needed by the fan. Burning rate increased with increase in volumetric air flow rate in both cold & hot phases. Specific fuel consumption increased linearly up to 0.027 m3s-1 and then dropped drastically in cold Phase. Considering Carbon monoxide & particulate matter emissions, the optimum air flow rate was 0.021 m3s-1 that corresponded to an average thermal efficiency of 33.5% for cold phase high power. During hot phase, the optimum air flow rate was 0.029 m3s-1 which resulted to thermal efficiency of 34%. Therefore, the general performance of the stove represents tier 3 according to International Workshop Agreement. This knowledge is finally useful to the users of gasifier stoves and designers in minimizing emissions at optimum efficiency.
Physico-chemical properties of extruded cassava-chia seed instant flour
(Elsevier, 2020-12) Otondi, Everlyne A.; Nduko, John Masani; Omwamba, Mary
This study evaluated the effects of extrusion process parameters and blends of chia seed and cassava flours on the nutritional and functional properties of flour blends aiming at improving the nutritive quality of cassava flour and enhancing the use of cassava in the production of extruded products. Extrusion was carried out using a single-screw extruder with constant parameters; screw compression ratio (3:1); die shape (round), die diameter (10 mm), pitch angel 45° screw, screw speed (100 rpm), and feed rate (35 rpm). The effect of feed moisture and amount of chia seed on the proximate composition, and physical and functional properties was determined using standard methods. The protein, fat and ash contents significantly (p < 0.05) increased from 2.39 to 12.23%, 0.79–11.77%, and 2.59–4.04%, respectively, with increasing chia seed incorporation. Increase in chia seed incorporation significantly (p < 0.05) increased Bulk Density (BD) of cassava from 0.45 to 0.63g/cm3 for 60% chia seed substitution ratio and 15% moisture conditioning and the Water Absorption Index (WAI) of cassava from 1.53 to 5.94% for 20% chia seed incorporation and 20% moisture conditioning, while reducing significantly the Water Solubility Index (WSI) from 55.48 to 17.48 g/g for 60% chia seed incorporation and 20% moisture conditioning. On the other hand, solubility and swelling power of the extruded flour blends varied in no particular direction with chia seed incorporation and feed moisture conditioning. The cassava-chia seeds blends exhibited potential for the production of nutritive extruded instant porridge flour (extrudate was milled to flour) with good physical and functional properties.

Browse

Browsing Energy by Subject "Egerton University"

Results Per Page

Sort Options