Browsing by Author "Barasa, Henry"

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  • Publication
    Publication
    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%.
  • Publication
    Publication
    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.
  • Publication
    Publication
    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 10.0.0.3). 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.