Renewable Energy Alternatives

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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.
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.
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.
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.
Polymer solar cells with reduced graphene oxide–germanium quantum dots nanocomposite in the hole transport layer
(Journal of Materials Science: Materials in Electronics, 2018-02-19) Amollo, Tabitha A.; Mola, Genene T.; Nyamori, Vincent O.
Reduced graphene oxide–germanium quantum dots (rGO–Ge QDs) nanocomposite has been successfully employed in modifying poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the hole transport layer (HTL) in the preparation of a P3HT:PCBM-based polymer solar cell (PSC). The effect of the surface morphology and the optical transmittance of the PEDOT:PSS/rGO–Ge QDs HTL on the devices’ photovoltaic performance is examined. A significant improvement of up to 50% in the power conversion efficiency is achieved by the incorporation of the composite in the HTL. The modified HTL devices exhibited higher short-circuit current density values which resulted from better transportation and collection of photo-generated charge carriers. The synergistic effect of the high electrical conductivity of the composites and the formation of good ohmic contact at the interface between the anode and the active layer not only facilitates charge carrier transport but also impairs their recombination to yield better photovoltaic performance.
Selection and Verification of a Drying Model for Maize (Zea mays L.) in Forced Convection Solar Grain Dryer
(science and education publishing, 2017) Osodo, Booker; Nyaanga, Daudi; Muguthu, Joseph
Various researchers have fitted experimental drying curves for various products to existing drying models. In this study, an experimental forced convection solar grain dryer was used to select the best fitting drying model for shelled maize. 0.04 m thick grain layer of shelled maize was dried an air velocity of 0.408 m/s and a 40°C drying air temperature. Using Root Mean Square Error (RMSE), Coefficient of Determination (R2) and Chi Square (𝜒𝜒2) the selected drying model was the one by Midilli et al. (2002), with R2, 𝜒𝜒2 and RMSE values of 0.9487, 0.4278 and 0.1723 respectively. The model coefficients were determined for drying air temperatures of 40, 45, 50 and 55°C. It was found that the predicted and experimental data agreed satisfactorily with R2 and RMSE values of 0.9225-0.9786 and 0.0325-0.0750 respectively. A computer simulation model was developed to predict moisture ratio at a given drying time.
Solar Radiation Prediction Models Analysis for Varying Climatic Conditions
(International Journal of Engineering and Technology, 2017-07) Wainaina, Patrick M.; Owino, George O.; Musa, Njue R.
This study has investigated global solar predictive models, modiﬁed, validated and compared ﬁve models, for prediction of monthly daily mean solar radiation in four different locations of Kenya that represents the four major climatic conditions. The input variables to the models Were; latitude, day length, sunshine hours, relative sunshine hours, temperature, and precipitation. Solar radiation data from 2000 to 2013 was used to obtain the monthly daily mean global solar radiation, to analyze, validate and compare the performance of the models. The predicted and measured data was simulated using MATLAB. Statistical indicators, MBE, RMSE, t-test and R, were performed to determine the models performance. The results showed that sunshine hours based models predicted global solar radiation with higher accuracy in wet and cold, wet and warm climatic conditions, while the temperature and precipitation models were accurate in solar radiation prediction in hot and dry climatic conditions. Key words: Global solar radiationl, Sunshine hours2, Day length3
Theoretical analysis of the electrical characteristics of lead-free formamidinium tin iodide solar cell
(Wiley, 2023-09-14) Katunge, Elizabeth K.; Njema, George G.; Kibet, Joshua K.
Green energy transition and climate change have gathered significant momentum in the world because of the rising population and increased clean energy demands. For this reason, renewable energy alternatives such as inexhaustible photo energy from the sun appear to be the ultimate solution to the world's energy needs. Formamidinium tin tri-iodide (HC(NH2)2SnI3)-based perovskites are found to be more efficient and stable than their methylammonium tin tri-iodide (MASnI3) counterparts because of its wider bandgap and better temperature stability. A device simulation of FASnI3-based solar cell is numerically performed using solar cell capacitance simulator (SCAPS-1D). The focus is to investigate the effect of changing working temperature, metal back contact, absorber thickness, defect density, and doping concentration on the performance of the proposed solar cell device. The optimised solar cell parameters of the proposed solar cell were: short-circuit current density (Jsc) of 28.45 mAcm−2, open-circuit voltage (Voc) of 1.0042 V, fill factor of 63.73%, and power conversion efficiency of 18.21% at 300 K, thus, paving the way for novel perovskite solar cells which are environmentally benign because they are lead-free, have better absorption efficiency, and can be injected into the production work flow for commercial applications.

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