Bio

DR. WAITA SEBASTIAN M

Personal Information

Areas Of Specialization

Condensed Matter Physics (Materials for Solar Energy conversion)

Research Interests

Photovoltaic (Solar Energy) Research & Training
 Materials for Solar Energy conversion
 Nanotechnology for Technology Applications
 Thin film characterization

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Publications


2016

WAITA, SEBASTIAN, Aduda B.  2016.  Emphasis on Photovoltaic (PV) Solar System Installation Training: A case study of a PV solar System Installed in Makueni County, Kenya. International Advanced Research Journal in Science, Engineering and Technology (IARJSET). 3(3) Abstract

The installation of Photovoltaic (PV) solar systems in institutions as well as homesteads in the rural areas in Kenya is increasing at a high rate; and so is the need for the stake holders to make sure the PV solar systems are professionally designed, sized, installed and maintained. In PV solar system installation, the designing, sizing and the installation are very critical steps. A wrongly designed, sized and installed system will not perform optimally and will underperform (for undersized systems) and waste energy and resources (for oversized systems). Furthermore, undersized systems do not perform to the user’s expectation discouraging the user and eventually a negative customer attitude creeps in which may affect the uptake of solar PV systems. On the other hand, an oversized PV system is extra expense on the side of the client, creating an exaggerated high cost of PV solar systems, again discouraging potential clients from the adoption of the technology. Both scenarios mean loss of business, jobs and the economic and social benefits associated with PV technology. We present a case study of poorly installed PV systemsin Makueni County, Kenya. We observed that the solar modules specifications at the back of the modules were not clearly done, the batteries were poorly matched and the cables used in the installation were undersized. Due to these issues, even a normal television set was not able to work since the system was installed four years ago (in 2012).The above case emphasizes the need for training in PV solar system design, sizing, installation, and maintenance.

Waita, 6. S, Aduda B.  2016.  Photovoltaic (PV) Solar Sizing for Off grid Solar Home Systems. International Journal of Applied and Natural Sciences . 5(5):73-78. Abstract

The sun releases tremendous amount of energy, which if harnessed would provide all energy needs of mankind. One of the strategies to trap this immense energy is the use of solar modules/panels. However, these solar modules need to be properly sized and installed to be able to function and generate electricity optimally. The successful installation of an off grid Photovoltaic (PV) solar system is a process that begins with a site visit to the area of installation, the determination of the client’s energy needs, installation of the solar PV system, commissioning of the installed solar system and ends with user training. Every step is critical for it determines the final performance of the solar system and hence the delicate balance between a satisfied or unsatisfied client. However, the system sizing step tends to attract more attention for it determines the system size and the matching of the balance of system components and so if this is not properly done, then the entire system may not perform as intended. Most documented sizing methods tend to be too complicated and require significant computer knowledge in simulation, modeling and even programming. For practical purposes, many designers and PV installers, especially in developing countries have basic education may not be well equipped for these complicated sizing methods. Furthermore, very few have been professionally trained in PV solar system Sizing and although there are commercially available sizing software’s, they are too expensive for majority of the people and even if available, they are too complicated for them. In actual sizing therefore, most untrained PV technicians use mere estimates that may not be appropriate for the outcome, more often than not is disappointing. We present a simple sizing method that can easily be learned and applied in a simple calculation, for example in a simple excels sheet formulas for easier sizing of PV systems The method is recommended for adoption in developing countries for faster dissemination of professional PV services in system sizing.

2014

Simiyu, J, WAITA SEBASTIAN, Robinson Musembi, Ogacho A, Aduda B.  2014.  Promotion of PV Uptake and Sector Growth in Kenya through Value Added Training in PV Sizing, Installation and Maintenance. Energy Procedia . 57 :817–825.

2013

Sebastian, W, Justus S, Robinson M, Alex O.  2013.  Promoting photovoltaic energy in Kenya through training. http://www.epsnews.eu/2013/03/photovoltaic-energy-in-kenya.
Fanuel Mugwang'a Keheze, Karimi Mwangi Patrick, Walter N, WAITA SEBASTIAN.  2013.  Copper Based Solar Cell Materials. EPS. , London: LAP LAMBERT Academic Publishing
WAITA, SEBASTIAN.  2013.  Performance of TiO2/In(OH)iSj/Pb(OH)xSy Composite ETA Solar Cell Fabricated from Nitrogen Doped TiO2 Thin Film Window Layer. International Journal of Materials Engineering . 3(2):11-16.

2012

Ayieko, CO, Musembi RJ, Waita SM, Aduda BO, Jain PK.  2012.  Performance of TiO2/In(OH)iSj/Pb(OH)xSy Composite ETA Solar Cell Fabricated from Nitrogen Doped TiO2 Thin Film Window Layer. AbstractPerformance of TiO2/In(OH)iSj/Pb(OH)xSy Composite ETA Solar Cell Fabricated from Nitrogen Doped TiO2 Thin Film Window Layer

In this work, Titanium Dioxide (TiO2) thin films were prepared by spray pyrolysis and thermally annealed at 400 oC. The films were characterized as deposited (no annealing) as well as after annealing. Optical studies showed that the energy band gap of the films was lowered from 3.25 eV to 2.90 eV on Nitrogen (N2) doping. The reduction in energy band gap was attributed to the introduction of N2 impurity states on the bands (conduction band and or valence band). The effect of N2 doping of Titanium Dioxide window layer on the efficiency of the ETA TiO2/In(OH)iSj/Pb(OH)xSy solar cell was investigated using a conventional current-voltage (I-V) technique. The photovoltaic conversion efficiency (η) increased from 1.06% for the solar cell with undoped films to 1.32% for the solar cell with N2-doped films. The increase in photovoltaic conversion efficiency on doping was attributed to increased light absorption due to the Nitrogen doping.

Mugwang’a, FK, Karimi PK, Njoroge WK, Omayio O, Waita SM.  2012.  Optical Characterization of Copper Oxide Thin Films Prepared By Reactive Dc Magnetron Sputtering For Solar Cell Applications. AbstractOptical Characterization of Copper Oxide Thin Films Prepared By Reactive Dc Magnetron Sputtering For Solar Cell Applications

— Cu2O thin films have been deposited using reactive dc magnetron sputtering technique using an Edward Auto 306 Magnetron Sputtering System. Transmittance and reflectance data in the range 300 nm-2500 nm were obtained using UV-VIS NIR Spectrophotometer Solid State 3700 DUV for all the thin films samples that were prepared. Transmittance values of above 70% were observed. The optical measurements were simulated using SCOUT 98 software to determine optical constants and optical bad gap of the thin. The optical properties in these films were varied by varying oxygen flow rate at constant powerof 200 W. Optical studies show a direct allowed transition and a shift in the optical absorption edge as the oxygen flow rate varies at constant argon flow rate and other deposition parameters. These results show that single phase Cu2O thin films can be synthesized at a relatively low substrate temperature using the reactive dc magnetron sputtering technique. Band gap values of 1.62 eV –2.54 eV is observed. The surface sheet resistivities at room temperature of 298 K were found to vary with the deposition parameters and film thickness. Urbach energy varied between 0.6 ×10-4 to 1.92 ×104

WAITA, SEBASTIAN.  2012.  Dark J-V Characterization of a Dye-Sensitized Module. International Journal of Professional Practice (IJPP),. 3(1&2):165-168.: International Journal of Professional AbstractWebsite

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WAITA, SEBASTIAN.  2012.  Structural and Optical Characterization of Nitrogen Doped TiO2 Thin Films Deposited by Spray Pyrolysis on Fluorine Doped Tin Oxide (FTO) Coated Glass Slides. International Journal of Energy Engineering. 2(3):67-72.: International Journal of Energy Engineering AbstractWebsite

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WAITA, SEBASTIAN.  2012.  Application of Dye-Sensitized Solar Cell Technology in the Tropics: Effects of Radiation Intensity and Temperature on DSSC Performance. International Journal of Advanced Renewable Energy Research (IJARER). 1(2):17-25.: International Journal of Advanced Renewable AbstractWebsite

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WAITA, SEBASTIAN.  2012.  Application of Dye-Sensitized Solar Cell Technology in the Tropics: Effects of Air Mass on Device Performance. International Journal of Renewable Energy Research (IJRER). 2(3):369-375.: International Journal of Renewable Energy Research AbstractWebsite

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2011

WAITA, SEBASTIAN.  2011.  Training on Photovoltaic Application and Installations, 4-5 August. PV TRAINING AND INSTALLATION. , Department of Physics, University of Nairobi: Elsevier Abstract

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WAITA, SEBASTIAN.  2011.  Workshop on Research Grant and Project Grant Training on proposal writing, 09/26-30/2011. Chiromo Conference Centre, University of Nairobi. , NAIROBI: Elsevier Abstract

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2010

WAITA, SEBASTIAN.  2010.  Extraction of Resistances in Dye Sensitized Solar Cells Fabricated from Obliquely Sputtered TiO2 Films,, 8-9 JULY. Opto-Electronics Devices: Their potential for Sustainable Development, conference held at the Department of Physics, University of Nairobi. , DEPT OF PHYSICS, UON: Elsevier Abstract

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WAITA, SEBASTIAN.  2010.  Electrochemical Characterization of TiO2 Blocking Layers Prepared by Reactive DC Magteron Sputtering, 3-7 MAY. African School on Nanoscience for solar Energy Conversion, Addis Ababa, Ethiopia.. , AKAKI CAMPUS, ADDIS ABABA: Elsevier Abstract

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2009

WAITA, SEBASTIAN.  2009.  Optical characterization of sputtered TiO2 compact under layers for dye-sensitized solar cell applications, 3-5 OCTOBER. 1st International conference on Solar Energy Materials Dar Es Salaam, Tanzania.. , Dar es Salaam: Elsevier Abstract

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WAITA, SEBASTIAN.  2009.  Electrochemical characterization of TiO2 blocking layers prepared by reactive DC magnetron sputtering. Journal of the Electroanalytical Chemistry 637, 79-83.. 637: Elsevier AbstractWebsite

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2008

Waita, SM, Aduda BO, Mwabora, J.M; Niklasson GA, Lindquist SE, Granqvist CG.  2008.  DC sputter deposited TiO2 photoelectrodes: Effect of deposition angle on the efficiency of dye sensitized solar cell..

2007

WAITA, SEBASTIAN.  2007.  Columnar and passivated nanoporous TiO2 based excitonic solar cell, 20-27 January. US/Africa workshop on frontiers in Material Science, Abuja, Nigeria.. , Abuja, Nigeria: Elsevier Abstract

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WAITA, SEBASTIAN.  2007.  Charge transport in bare and MgO-coated TiO2 thin films and in dye-sensitized solar cells: effect of film thickness, 31st July-3rd Au. ICE2007, International conference on Electroceramics, Arusha, Tanzania.. , Arusha, Tanzania: Elsevier Abstract

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WAITA, SEBASTIAN.  2007.  Electron Ttransport and Recomination in Dye Sensitized Solar Cells Fabricated from Obliquely Sputtered and Thermally Annealed TiO2 films. Journal of the Electroanalytical Chemistry 605(2), 151-156.. : Elsevier AbstractWebsite

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WAITA, SEBASTIAN.  2007.  Effect of nitration on pressed TiO2 photoelectrodes for dye-sensitized solar cells. African Journal of Science and Technology,Vol. 8 No. 2, pp 63-71. : ANSTI AbstractWebsite

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2006

WAITA, SEBASTIAN.  2006.  Nanostructured TiO2 for dye sensitized photoelectrochemical solar cells, 14-25th August. ICTP-NCNNC . , Beijing, China: Elsevier Abstract

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WAITA, SEBASTIAN.  2006.  Performance of Dye Sensitized Solar Cells Fabricated From Obliquely DC Sputtered TiO2 Films. African Journal of Science and Technology Vol. 7, No. 2, 125-138. : ANSTI AbstractWebsite

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2000

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