Renewable Energy Alternatives

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Browsing Renewable Energy Alternatives by Subject "Kenyatta University"

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  • Publication
    Publication
    Characteristics of TiO2 Compact Layer prepared for DSSC application
    (Path of Science, 2018-11-04) Musila, Nicholas; Munji, Mathew; Simiyu, Justus; Masika, Eric; Nyenge, Raphael; Kineene, Miriam; Musila, Nicholas; Munji, Mathew; Simiyu, Justus; Masika, Eric; Nyenge, Raphael; Kineene, Miriam
    Dye-sensitized solar cells (DSSCs) offer an economically reliable and suitable alternative in moderating the challenges presented by the existing convectional photovoltaic cells. However, the efficiency of dye-sensitized solar cells has remained relatively low. For this reason, this research was aimed at studying the characteristics of TiO2 compact layer that can be applied in DSSCs as a way of improving efficiency. To achieve this, TiO2 compact layer was deposited on a conductive glass substrate by using Holmarc’s Spray Pyrolysis system, using Ultrasonic Spray Head and spraying in the vertical geometry. X-ray Diffraction studies revealed that TiO2 compact layer was of anatase phase and had tetragonal crystalline structure. Raman spectroscopy showed that the most intense peak appeared at 142 cm-1 due to the external vibration of the anatase structure. Hall Effect studies revealed that TiO2 compact layer has a high density of charge carriers’ value of 1.25 × 1019 cm-3 hence it can be used in DSSC applications.
  • Publication
    Publication
    Effect of TiO2 Compact Layer on DSSC Performance
    (Social Science Research Network, 2018-09-30) Musila, Nicholas; Munji, Mathew; Simiyu, Justus; Masika, Eric; Nyenge, Raphael
    Dye-sensitized solar cells offer an economically reliable and suitable alternative in moderating the challenges presented by the existing convectional photovoltaic cells. Whereas, for convectional solar cells the semiconductor adopts both the duty of light absorption and charge carrier transport, these two functions are separated in dye-sensitized solar cells. However, the efficiency of dye-sensitized solar cells has remained relatively low. For this reason, this research was aimed at how to increase the dye-sensitized solar cells performance. To achieve this, compact cover of TiO2 was deposited on a conductive glass substrate by using Holmarc’s Spray Pyrolysis system, using Ultrasonic Spray Head and spraying in vertical geometry, while TiO2 nanoparticles and nanotubes were deposited by screen printing technique on top of a transparent conducting FTO glass slide with or without the TiO2 compact layer. Transmission characteristics showed that introducing TiO2 compact layer on the conductive film lowers the transmission while reflectance properties were less than 15 % for all the prepared thin films. SEM micrographs showed that TiO2 nanotubes had a skein-like morphology with abundant number of nanotubes intertwined together to form a large surface area film. Solar cell performance properties revealed that introducing compact layer to dye-sensitized solar cells improved the performance by 145 % (from 1.31 % to 3.21 %) while TiCl4 treatment on compact layered dye-sensitized solar cells increased the efficiency by 28.79 % (from 0.66 % to 0.85 %).
  • Publication
    Publication
    Electron Impact Elastic Scattering of Strontium Using Distorted Wave Method
    (Kenyatta University, 2018-11)
    Differential and integral cross sections for electron-atom are useful for interpretation and understanding of electron contact with the targets and for determining dynamics of the collision processes. They are useful in X-ray photoelectron spectroscopy (XPS), upper atmosphere dynamics, Monte-Carlo simulation (MCS), Auger-electron spectroscopy (AES), in gaseous-exchange, laser development, plasma physics and fluorescent lighting. For elastic scattering of strontium very few calculations have been performed and currently there are no known results using the present method. Also the available theoretical results do not have other results to be compared with so it makes it important to obtain results to compare them and to be compared with future experimental results. In calculation of differential and integral cross section for elastic scattering of electron by strontium atom, first-order distorted wave born approximation method has been used to determine DCS and ICS at impact energies of 10eV to 200eV and scattering angles ranging from 00 to 1800. Also in this study at the initial state, both initial and final channel distortion potential of elastic scattering of electron by a strontium atom are taken as the static potentials since it is an elastic scattering. The distorted waves are expanded in terms of radial wavefunctions and spherical harmonics, Numerov method was then used to solve the radial equations to obtain the radial wavefunctions. The Madison and Bartschat computer program DWBA1 for e- - H scattering was modified to perform the mathematical computations for e - - Sr scattering and the results for differential and integral cross sections are calculated and compared with the available results. The integral cross sections (ICS) results agree well qualitatively with the other theoretical results. At lower incident energies (10-30 eV), the present differential cross section (DCS) results disagree with results obtained from optical potential method. This is because the first order distorted wave method gives poor results at low impact energies and also the nature of the distortion potential used. At intermediate and higher energies (60-200 eV), the present DCS results agree well with the results obtained from optical potential method. In conclusion, the DWBA was developed and applied to 𝑒− - Sr scattering, changes on the DWBA1 computer program were made for strontium, differential cross section (DCS) and integral cross section (ICS) at impact energies 10-200eV for elastic scattering of electron-strontium were determined using DWBA at intermediate and high energies and the results compared with the other available results. From this work it was recommended that some experimental studies on electron impact elastic scattering of strontium should be made to give results for comparison with the calculated results, more theoretical studies using other methods should be conducted on DCS and ICS for purposes of comparison with the present results, a distortion potential that incorporates the polarization potential, exchange potential and absorption potential should be used in the calculation and the present method incorporating all the distortion potentials should be extended further for electron impact elastic scattering of other alkaline earth metals such as beryllium, cesium, ytterbium, and radium.