Browsing by Author "Munji, Mathew"

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    Effect of Substrate Temperature on the Optical Properties of SnxSey/ZnO:Al P-N Junction Solar Cell
    (Scientific & Academic Publishing, 2017) Gitonga, John; Munji, Mathew; Musembi, Robinson; Mugambi, Nelson; Gitonga, Geoffrey
    Zinc Oxide was doped with various percentages of Aluminum ranging from 0% to 10% by mass. Tin (Sn) and selenium (Se) metal samples were mixed in different ratios of increasing selenium. Deposition of both SnSe and ZnO:Al thin films on glass substrate was done by a method of evaporation using Edwards Auto 306 RF/DC Magnetron evaporation system under the following conditions; deposition temperature 500K, pressure of 3.5×10-5 millibars and a current of 3.5A. Transmittance and reflectance data in the range 300nm-1500nm was obtained using a double beam solid spec 3700 UV-VIS-NIR shimadzu spectrophotometer. Doping of 5% aluminium and a synthesized ratio of 1:1.0 for ZnO:Al and SnSe thin films respectively was obtained as the optimum values. The optimized Al doped ZnO was deposited at different deposition temperature ranging from 350K-550K. Transmittance percentage in the visible region was used to optimize deposition temperature and 510K was obtained as the optimum value. Band gap energies of optimized ZnO:Al and SnxSey was found to be 3.61±0.05 eV and 1.37±0.05 eV respectively.
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    Impact of Annealing Thin Films In(OH)xSy Growth By Solution Technique
    (Publishing Center Dialog, 2017) Mosiori, Cliff Orori; Magare, Robert; Munji, Mathew
    Indium Hydroxy Sulphide has demonstrated abundance in resources, low prices, nontoxic characteristics, radiation resistance, high temperature resistance, and chemical stability, and therefore it has become an extremely important photoelectric, photovoltaic, and light sensing thin film material. Some treatment on this material include thermal annealing which is a process used for intrinsic stress liberation, structural improving, and surface roughness to control its electro-optical properties. In a qualitative way, annealing modifies surface morphology, intrinsic parameters, and electron mobility with temperature and time. In this work, an explanation on the surface modification of In(OH)xSy thin films when subjected to an annealing process is discussed. Both electrical and optical effects caused by annealing were carried out and characterizations were performed at different annealing temperatures in nitrogen in the temperature range 373–573 K. Using optical measurements data and simulated data, Scout software was employed and the results showed that increasing annealing temperature causes a slight decrease in transmittance with a consequence of modifying the energy band gaps values between 2.79–3.32 eV. It was concluded that annealing influence optical transmittance and resistance of the film make the thin films potential for photovoltaic, and light sensing applications.
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    Performance Analysis of 600 Kwp Grid-Tied Rooftop Solar Photovoltaic Systems at Strathmore University in Kenya
    (Results in Engineering, 2023-07) Ayora, Emmanuel; Munji, Mathew; Kaberere, Keren; Bundi, Thomas
    Kenya boasts of abundant solar irradiation potential across its expansive regions, averaging between 4.5 kWh/m2 and 6 kWh/m2 per day. Despite this advantageous condition, solar energy's contribution to the national energy mix remains relatively low. To boost solar energy contribution to the national grid, it is crucial to assess the performance of existing grid-tied solar PV systems and develop strategies to improve their energy yields and further help in designing and installing new plants. This paper presents a technical performance analysis of a 600-kWp grid-tied solar PV system at Strathmore University, monitored over one year between January and December 2019. Economic and thermographic analysis of the solar PV system is done. The performance indices studied according to IEC 61724 standard include performance ratio, capacity utilization factor, reference yield, final yield, total collection losses, and total energy yield. This solar plant generated 735 MWh in 2019. The annual average monthly performance ratio, capacity factor, and annual specific energy yield were 57.4%, 13.97%, and 1225 kWh/kWp, respectively. The annual average monthly final yield, array yield, reference yield, and total system collection losses were 3.37 kWh/kWp, 4.49 kWh/kWp, 5.9 kWh/kWp, and 2.53 kWh/kWp, respectively. The thermographic analysis done shows that the system exhibits healthy temperature distribution. The economic analysis demonstrated Levelized Cost of Energy (LCOE) and simple payback period of US$ 0.143/kWh and 9.1 years respectively. The study reveals that the Strathmore system's performance is similar to other solar plants worldwide.