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    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.
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    Effect of Total Solids on Biogas Production in a Fixed Dome Laboratory Digester under Mesophilic Temperature
    (Annals of Advanced Agricultural Sciences, 2020-05) Barasa, Henry; Nyaanga, David; Njue, Musa; Matofari, Joseph
    An investigation on the effect of total solids on biogas production was done using a laboratory scale batch reactor of 0.15 m3 capacity. The feedstock was dung from dairy cows managed under a free-range system. Experiments were done on a substrate having total solids of 6%, 7%, 8%, 9%, and 10% at a constant temperature of 35°C; and the mean biogas production was 0.249, 0.304, 0.487, 0.287, and 0.244 m3 of biogas per m3 of digester volume per day (m3/m3d), respectively. It was concluded that the highest average biogas production of 0.487 m3/m3d is attained at total solids of 8%.
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    Effect of Stirring Intervals on Biogas Production from Cow Dung and Maize Silage Mix Ratio
    (International Journal of Power and Energy Research, 2021-04-30) Chol, Monyluak M. Y.; Muchuka, Nicasio M.; Nyaanga, D.
    Most biogas plants’ poor performance may be attributed to inadequate stirring strategy. The study evaluated the effect of stirring intervals on biogas production from cow dung and maize silage mixture (at mixed ratio 3:1) digested in a 0.15m3 laboratory digester at 30℃. SIEMENS LOGO PLC and ATV12HU15M2 Drive automatically controlled the stirring of 100 rpm for 3minutes at intervals of 1hour, 2hours, 6hours and 12hours with no stirring as control. The stirring intervals showed a significant effect on biogas production (P≤0.05) with 6hours and 12hours increased biogas by 3.11% and 1.48%, and the methane increase of 8.77% and 1.75%, respectively. The 2hours and 1hour reduced biogas by 26.5% and 39.35%, and methane decreased by 3.52% and 15.79%, respectively compared to control (implying that the frequent stirring is not good for biogas). The stirring interval of 6hours is thus recommended for 0.15m3 laboratory batch reactor of cow dung and maize silage.
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    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.
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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.
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    Isolation of Actinomycetes from Geothermal Vents of Menengai Crater in Kenya
    (International Journal of Molecular Biology, 2017-07-20) Waithaka, Paul Njenga; Mwaura, Francis; Wagacha, John M.; Gathuru, Eliud Mugu
    The current study was carried out to isolate actinomycetes from the geothermal vents of Menengai crater. Soil samples were collected from vents A and D in sterile polythene papers and transported to Egerton University, Department of biological sciences laboratories. The samples were air dried on the benches for one week. To kill vegetative bacteria, the soil samples were heat in a hot air oven for 1h before serial dilution to 10-6. The samples separately plated on Starch casein agar, Luria Bertani agar and starch nitrate agar in which nystatin and nalidixic acid had been added to reduce the growth of fungi and other types of bacteria. Incubation was carried out at 30 o C for up to a period of one Month. The isolated actinomycetes were characterized by cultural, morphological and biochemical means. There was no significant difference in the number of actinomycetes isolated between vents A and vents D(P=0.439). However, the number of actinomycetes isolated using the three isolation media varied significantly (F=37, P=0.03). Totally, 16 actinomycetes were isolated from the vents. It is recommended that the isolates be tested for antagonism against pathogenic microorganism.
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    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.
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    Graphene for Thermoelectric Applications: Prospects and Challenges
    (Critical Reviews in Solid State and Materials Sciences, 2017-04-10) A, Amollo; Mola, Genene Tessema; Nyamori, Vincent
    Thermoelectric power generators require high-efficiency thermoelectric materials to transform waste heat into usable electrical energy. An efficient thermoelectric material should have high Seebeck coefficient and excellent electrical conductivity as well as low thermal conductivity. Graphene, the first truly 2D nanomaterial, exhibits unique properties which suit it for use in thermoelectric power generators, but its application in thermoelectrics is limited by the high thermal conductivity and low Seebeck coefficient resulting from its gapless spectrum. However, with the possibility of modification of graphene's band structure to enhance Seebeck coefficient and the reduction of its thermal conductivity, it is an exciting prospect for application in thermoelectric power generation. This article examines the electronic, optical, thermal, and thermoelectric properties of graphene systems. The factors that contribute to these material properties in graphene systems like charge carriers scattering mechanisms are discussed. A salient aspect of this article is a synergistic perspective on the reduction of thermal conductivity and improvement of Seebeck coefficient of graphene for a higher thermoelectric energy conversion efficiency. In this regard, the effect of graphene nanostructuring and doping, forming of structural defects, as well as graphene integration into a polymer matrix on its thermal conductivity and Seebeck coefficient is elucidated.
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    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.
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    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
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    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.
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    High-performance organic solar cells utilizing graphene oxide in the active and hole transport layers
    (Elsevier Ltd, 2018-06-22) Amollo, Tabitha A.; Mola, Genene T.; Nyamori, Vincent O.
    We have successfully synthesized and employed graphene oxide (GO) to boost photons harvesting and charge transport process in thin film organic solar cells (TFOSCs). The graphene oxide was inlayed in both the P3HT:PCBM-based photoactive medium of the device, as well as, a dopant in PEDOT:PSS hole transport buffer layer (HTL). The parameters of the solar cells produced with the inclusion of GO in the HTL and the active layer results in high short-circuit current densities (Jsc), which translated into high power conversion efficiencies (PCEs). GO in the HTL facilitates charge transport, selective electron blocking and hole injection at the interface for enhanced device performance. On the other hand, the use of GO in the active layer remarkably improves the optical absorption leading to high charge carriers photogeneration requisite to efficient OSCs. Similarly, effective exciton dissociation is energetically favoured in the GO modified active layer devices which corroborated with improved conductivity of the medium that assisted charge carriers transport processes. Enhanced photocurrent has been recorded, as high as 18 mA cm−2, from the TFOSCs by the inlay of GO in the active layer. Consequently, increased PCE of up to 40% and 120% is achieved by the inclusion of GO in the HTL and photoactive layers, respectively.
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    Optimization of Biogas Production in a Batch Laboratory Digester Using Total Solids, Substrate Retention Time, and Mesophilic Temperature
    (International Journal of Power and Energy Research, 2020-07) Barasa, Henry; Nyaanga, David; Njue, Musa; Matofari, Joseph
    Optimization was done by investigating the interaction effects of total solids, mesophilic temperature, and substrate retention time on biogas production in a batch biodigester. The volume of the biodigester was 0.15m3. Central composite design of Response Surface Methodology was used to design the experiment. Total solid levels were varied from 6.31% to 9.68%, temperature was from 26.59°C to 43.41°C, and substrate retention time was from 9.95 to 20.04 days. Analysis of results was done using Design Expert software statistical package (version It gave a coefficient of determination of 0.9665 which indicated a high correlation between the variables. All the variables had a significant effect. The highest biogas production rate of 75.41litres/day (or 0.50 m3 of biogas per m3 of digester volume per day, m3/m3d) was achieved at a level of 8% total solids, a temperature of 43.41°C, and a substrate retention time of 15 days.
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    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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    Performance Evaluation of Silicon-Based Photovoltaic Modules Found in the Kenyan Market
    (Kenyatta University, 2015) Njeru, Elosy Gatakaa
    Various kinds of photovoltaic (PV) modules have been developed and practically deployed as PV systems over time. The performance of PV modules found in the Kenyan market has not been documented and therefore their reliability and stability in providing an alternative source of energy has not been sufficiently established. In this study the I-V data of Silicon-based mono crystalline, poly crystalline and amorphous modules was collected. The choice of the modules was done randomly depending on their availability, the cost of the modules and their power rating. They were selected randomly from PV module vendors within Nairobi Central Business District (CBD). The manufacturers’ specifications were taken. The modules were then mounted at an optimum fixed tilt angle of 15 degrees. Initial measurements of short circuit current Isc, open circuit voltage Voc, ambient temperature and module temperature were taken immediately on mounting the modules. Measurements of current and voltage to obtain I-V data was done daily at solar noon for four months. The back of the module temperature and ambient temperature at the time of measurement was measured using thermocouple while the irradiance at the time of measurement was measured using a pyranometer. The pyranometer was mounted at the plane of array of 15 degrees as the modules. The collected I-V data was normalized and I-V curves were plotted. Performance parameters of the modules were then calculated from the I-V curve. There was a decrease in Voc of the modules with time with the amorphous modules clearly showing the Staebler-Wronski effect. The Isc of the modules showed little variation while Pmax of the modules had reduced significantly. The Pmax of most of the modules was found not to match with the manufacturers specifications provided in their data sheet. On inspection of the modules, the 10W polycrystalline module revealed a defect which was as a result of overheating of the cells that contributed greatly to its poor performance in comparison to the other polycrystalline modules. The efficiency of the amorphous modules ranged between 3%- 5% while that of mono crystalline and polycrystalline was above 10%.
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    Status of Micro-Hydrokinetic River Technology Turbines Application for Rural Electrification in Africa
    (MDPI, 2022-11-28) Awandu, Willis; Ruff, Robin; Wiesemann, Jens-Uwe; Lehmann, Boris
    Energy accessibility, reliability and availability are key components of improved quality of life and human development in all spheres. As the United Nations’ SDG 7 calls for access to electricity for all by 2030, Africa still has a wide gap to fill as the statistics show that 85% of the population that will not have access to electricity is in Africa. As the world tries to wean itself off non-renewable energy and transition to green through use of renewable energy sources, hydropower energy remains at the heart of Africa for this venture. With majority of the rural population in Africa lacking electricity, there is need for a low-tech system that utilizes river flow to generate just enough energy for normal operation in these regions. Micro-hydrokinetic river turbine technology (µ-HRT), which offers less intermittency, can potentially contribute to sustainably electrifying Africa rural areas. The technology has been adopted by few countries worldwide, with limited comprehensive study in Africa even though the technology seems viable for use in African rivers. This paper reviewed the status of the µ-HRT applications in Africa and some of the barriers to its development. The study found out that the technology has not been vastly developed in Africa. Despite numerous barriers, the technology is simply a low-tech technology that requires the use of local resources and capacity building for its sustainability in terms of construction, operation and maintenance requirements. It is therefore recommended that R&D and field trials be conducted for its possible adoption.
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    Thickness Dependence of Window Layer on CH3NH3PbI3-XClX Perovskite Solar Cell
    (International Journal of Photoenergy, 2020-07-28) Isoe, Wycliffe; Mageto, Maxwell; Maghanga, Christopher; Mwamburi, Maurice; Odari, Victor; Awino, Celline
    CH3NH3PbI3-xClx has been studied experimentally and has shown promising results for photovoltaic application. To enhance its performance, this study investigated the effect of varying thickness of FTO, TiO2, and CH3NH3PbI3-xClx for a perovskite solar cell with the structure glass/FTO/TiO2/CH3NH3PbI3-xClx/Spiro-OMeTAD/Ag studied using SCAPS-1D simulator software. The output parameters obtained from the literature for the device were 26.11 mA/cm2, 1.25 V, 69.89%, and 22.72% for Jsc, Voc, FF, and , respectively. The optimized solar cell had a thickness of 100 nm, 50 nm, and 300 nm for FTO, TiO2, and CH3NH3PbI3-xClx layers, respectively, and the device output were 25.79 mA/cm2, 1.45 V, 78.87%, and 29.56% for Jsc, Voc, FF, and , respectively, showing a remarkable increase in FF by 8.98% and 6.84% for solar cell efficiency. These results show the potential of fabricating an improved CH3NH3PbI3-xClx perovskite solar cell.
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    Optical modelling of TCO based FTO/TiO2 multilayer thin films and simulation in hydrogenated amorphous silicon solar cell
    (Elsevier, 2023-07) Isoe, Wycliffe M.; Mageto, Maxwell J.; Maghanga, Christopher M.; Mwamburi, Maurice M.; Odari, Benjamin V.
    Hydrogenated Amorphous silicon (a:Si:H) has low amounts of defects making it attractive for photovoltaic applications. To improve power conversion efficiency (PCE) of a:Si:H solar cells, this study investigated the effect of introducing FTO/TiO2 multilayer thin films into its structure to serve as antireflection coating. The multilayer thin films were characterized and optimized by optical simulations using a computer program, GLSIM (glazing simulator). The program was written in FORTRAN and implemented in MATLAB. The multi-Fresnel equations were employed to create the GLSIM program. Then using the program, together with the pairs of real and imaginary values of complex refractive index, n and k respectively, the transmittance and reflectance data of FTO/TiO2 multilayer thin films on glass substrate were computed. The optimized FTO/TiO2 multilayer thin films were then incorporated into silicon solar cell with structure glass/FTO/TiO2/n-a-Si:H/i-a-Si:H/p-a:Si:H/P+-BSF and characterized using SCAPS-1D software. The effect of varying layer thickness on the solar cell performance was also investigated. The optimized solar cell had a thickness of 100 nm, 50 nm, 900 nm, 100 nm, 10μm and 5μm for FTO, TiO2, n-a-Si:H, i-a-Si:H, p-a-Si:H and P+-BSF respectively. The device output performance were 37.96 mA/cm2, 1.34 V, 56.37% and 28.72% for Jsc, Voc, FF and η respectively showing a remarkable improvement in the solar cell performance. These results show potential of fabricating an improved hydrogenated silicon solar cell.
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    Numerical study of lead free CsSn0.5Ge0.5I3 perovskite solar cell by SCAPS-1D
    (Elsevier, 2021-12) Nalianya, Milimo Amos; Awino, Celline; Barasa, Henry; Odari, Victor; Gaitho, Francis; Omogo, Benard; Mageto, Maxwell
    Lead free perovskite solar cells (PCS) are becoming a distinctly predominant area of study due to the toxicity and stability hurdles of the lead halide perovskite. Current lead-free perovskites are also plagued with low efficiency. This work is concerned with the design and analysis of CsSnGeI3 that is a viable competitor to lead based perovskites by SCAPS-1D simulator (ver.3.3.08). The primary solar cell’s structure is FTO/PCBM/ CsSn0.5Ge0.5I3 / spiro-OMeTAD/Au which achieved a power conversion efficiency (PCE) of 7.11% [1]. To enhance device performance, the effect of optimizing absorber layer defect density (1 × 1015 cm−3) and thickness (700–800 nm), doping concentration of absorber layer (1 × 1015 cm−3), variation of Electron Transport Material (ETL) and Hole Transport Material (HTL) parameters (effect of CBO and VBO and doping concentration) and potential material options for ETL and HTL are studied. The results of the simulation are as follows; maximum power conversion efficiency (PCE) 18.79%, short circuit current density (Jsc) 27.05 mA/cm2, open circuit voltage (Voc) 0.87 V and fill factor (FF) 79.25%. By choosing appropriate material parameters, improving fabrication and encapsulation processes, CsSn0.5Ge0.5I3 proves to be an environmentally friendly solar cell with high efficiency.
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    Numerical Study of Copper Antimony Sulphide (CuSbS2) Solar Cell by SCAPS-1D
    (Heliyon, 2023-07-27) Obare, Nancy; Isoe, Wycliffe; Nalianya, Amos; Mageto, Maxwell; Odari, Victor
    Copper antimony sulphide has ability in applications on photovoltaics since it is a promising, less toxic, earth abundant absorber material. In this study, the photovoltaic characteristics of copper antimony sulphide (CuSbS2) photovoltaic cell were simulated and studied by one dimensional solar cell capacitance simulator (SCAPS-1D) to improve their operations. This study investigated the impact of modifying the thicknesses of fluorine-doped tin oxide (FTO), cadmium sulphide (CdS), carbon(C), and CuSbS2 absorber layer, Also the amount of doping and the number of defects on CuSbS2 photoactive layer, the structure of the solar cell is made up of glass, FTO, n-CdS, p-CuSbS2, C, and Au. The optimum parameters of the designed photovoltaic cell yielded 0.9388 V of open-circuit voltage (Voc), the short-circuit current density (Jsc) was 28.31 mA/cm2, the fill factor (FF) of 60.8%, and the solar cell efficiency of 16.17%. The ideal thickness was discovered to be 300 nm for the CuSbS2 solar cell. The defect density increment led to a decrease in carrier lifetime resulting also to decrease in diffusion length and the optimum absorber layer doping concentration was found to be 1018 cm-3