MST-Department of Electrical and Electronic Engineering
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Item Design and Optimization of a Solar Photovoltaic Mini-Grid: Case Study of Rwumba Village of Nyamasheke District, Rwanda(Kenyatta University, 2021) Augustin, Munyaneza; Maurice Kizito Wafula Mangoli; Keren KaberereUniversal access to clean energy is very paramount and brings along with it a lot of socio-economic benefits to the citizens in terms of poverty reduction, cost effectiveness and safeguarding the environment. However, most rural areas in developing countries have no access to electricity due to the high cost of power transmission and this hinders their development. In this perceptive, Rwumba Village of Nyamasheke district of Rwanda has no access to electricity from the grid. This research focused on the design of an optimum solar photovoltaic (PV) mini-grid system that can provide the required power and energy to the village. The solar PV mini-grid was designed and optimized using HOMER software. To achieve good results, two sites were visited and specific data were collected for each site by means of questionnaires. The first site visited is an existing standalone solar PV system known as Banda solar PV mini-grid and the second site is Rwumba village which is the case under study. The data collected from the existing Banda solar mini-grid include among others installed capacity and size of various system components, load data, energy and power requirements. Analysis of these data showed that this system is not optimum. The PV panels were found to be oversized whereas the storage batteries are undersized. Thus, using HOMER software, a model for optimizing this existing mini-grid was developed, simulated and validated using the data collected from the same mini-grid. The software simulated the combinations of inputs (PV panel, battery, power inverter and cost) at different capacity shortages and proposed the most optimum combinations. The best results corresponding to the optimum PV mini-grid were obtained at the capacity shortage of 3% which means that the mini-grid can meet the load at the reliability of 97% throughout the year. The estimated peak power and daily energy requirement was found to be about 7.5 kW and 51 kWh respectively. This is to be provided by PV panel capacity of 16 kW, battery bank storage of nominal capacity of 192 kWh that will be able to store energy for 3 days during cloudy days and power inverter of 12 kW. Then, the same procedure was followed to achieve most optimum results for Rwumba solar PV mini-grid. The optimum system size was found to have PV Panel capacity of 34 kW, a battery bank storage of 384 kWh nominal capacity, and power inverter of 15 kW serving an estimated daily load of 111 kWh. The power distribution system for the mini-grid was designed to be single phase supply two wire with distribution voltage of 230 V. The layout of households in the village dedicated the power to be distributed using three feeders from the power generation point. Feeder 1 is 0.4 km long, with power demand of 4.2 kW and a voltage drop of 4.5%; feeder 2 is 0.45 km long, power demand of 3.9 kW and voltage drop of 4.7% while feeder 3 is 0.45 km long, power demand of 5.9 kW and voltage drop of 4.4%. These results revealed that, the same size of the conductor present different voltage drop and power losses depending on the power demand and the location distance of the load being electrified from the generation plant. Economic analysis of the designed system was done using the life cycle cost technique. An annual interest rate of 6% and 20 years project life were used. The initial capital was found to be about USD 143,660. The payback period was found to be around 10 years at the system’s annual cash inflow of USD 13,435 and cost of energy of USD 0.419 per kWh. This means that there will be around 10 years of realizing the profit. Therefore, it was concluded that the project is financially feasible since the payback period is less than the project lifetime.Item Design and Fabrication of a Greenhouse Monitoring and Control System Based on Global System for Mobile Communication and Bluetooth(Kenyatta University, 2020) Nyaga, Stephen GitongaGreenhouse technology should be embraced as a way of minimizing food insecurity in Kenya. The insecurity is brought about by climate uncertainties. Greenhouses have attempted to solve this problem by enclosing crops in a climatically controlled environment. Each greenhouse has distinct parameters. Data on these parameters need to be collected at regular intervals. Depending on the type of crop, these parameters need to be controlled within the specified limits to achieve the maximum efficiency and yields. In the past, greenhouses utilized electromechanical devices such as thermostats to monitor and control the environment. Mechanical systems lack the flexibility and precision required for greenhouse control. Some modern greenhouses use computers to control the environment. Computers based controllers are station based, bulky and costly. In this study a wireless prototype greenhouse monitoring and control system that is flexible, cheap, easy to maintain and easy to assemble was developed and implemented. The general objective of this research work was to design, fabricate and implement a microcontroller-based prototype to monitor and control greenhouse parameters using sensors, SMS technology and Bluetooth signals. The hardware consisted of ATmega328 microcontroller, Global System for Mobile communication (GSM) SIM800L module, HC05 Bluetooth module, HD44780U Liquid Crystal Display (LCD) module, 5 volt 4 channel relay module, Light dependent resistor (LDR) sensor and digital humidity and temperature (DHT11) sensor. The LDR sensor was utilized to measure light intensity while the DHT11 sensor was utilized to measure humidity and temperature levels in the prototype greenhouse. The DHT11 and LDR sensors, the relay, the LCD, the GSM and the Bluetooth modules were interfaced to the ATmega328 microcontroller. Through Arduino software, a program was written in C language, developed and uploaded to the ATmega328 microcontroller to run the greenhouse prototype. The program is designed to operate in automatic or manual mode. In automatic mode, the microcontroller constantly monitors the digitized values from the sensors and compares them with the optimized values and checks if any control procedures needs to be taken. In manual mode, the system could be operated wirelessly by use of GSM or Bluetooth module. The designed prototype greenhouse system is able to measure temperature, humidity and illuminance levels in the prototype greenhouse and display the values on the LCD. The system transmits the sensor measured values to owner’s phone via Bluetooth or a GSM and keeps these parameters at optimum levels by use of two fans, heater, bulb and a sprinkler. The GSM module is used for remotely monitoring and controlling the devices via a smart phone by sending and receiving Short Messaging Service via GSM network. If the user is in the vicinity of the prototype, the Bluetooth and a software installed in the smart phone provides a wireless link between the prototype and the cell phone. This project therefore provides a cost effective and efficient means of monitoring and controlling greenhouse parameters. In addition the system allows mobility during monitoring and control process. The reliability of the designed system can be exploited to build a network of such monitoring and control systems for several greenhouses. A website can be incorporated in the designed system to monitor the actual greenhouse values and save the data in an online database for future reference. The designed prototype greenhouse can be applied in the agricultural sector in the design and implementation of greenhouses.Item Characterization Of Snse-Cdo:Sn P-N Junction For Solar Cell Applications(2014-08-26) Nyakundi, Makori EvansEnergy crisis occasioned by a decline in the availability of fossil fuels and increasing carbon dioxide emissions that are causing global warming has enhanced interest in the development of clean and renewable sources of energy. Solar energy has a great potential of meeting a large fraction of energy needs using photovoltaics. While most PV cells in use today are Silicon-based, cells of other semiconductor materials have been manufactured. Considerable research has been focused in search of thin-film PV cells with high conversion efficiency. In this study, SnSe and CdO:Sn thin films were optimised for photovoltaic applications. SnSe and CdO:Sn thin films were successfully deposited by thermal and reactive thermal evaporation respectively using Edward’s Auto 306 Magnetron Sputtering System . Their optical and electrical properties were studied using Solid Spec-3700 DUV Spectrophotometer and Keithley 2400 Source Meter respectively. Transmittance of the SnSe thin films deposited had transmittance ranging between 19-50% while reflectance ranged between 10-50%. The band gap values of SnSe thin films obtained were in the range of 1.71-1.76eV. SnSe thin films showed decrease of resistivity from 181-120Ωcm with increase in film thickness from 112-148nm. The optical properties of CdO:Sn showed high transparency in the visible region which varied with Sn doping, this makes CdO:Sn an excellent candidate for optoelectronic applications as a window layer. CdO and CdO:Sn had a transmittance of 70-85% and 50-89% respectively within the visible range of the electromagnetic spectrum. Reflectance of doped and undoped CdO was between 19-28%. Band gap energy for undoped CdO was 2.43eV while that of tin doped CdO ranged between 3.19-3.29eV for tin doping of 1-7%. Resistivity of CdO and CdO:Sn ranged between 16-93Ωcm. The optimised thin films were used to fabricate SnSe-CdO:Sn P-N junction. The I-V characteristics obtained were; Isc=0.993mA, Voc=273mV, Imax=0.905mA, Vmax=207mV, FF=0.69 and η = 0.59%.Item Performance of a photovoltaic module with an integrated compound parabolic concentrator and a cooling system(2012-01-19) Tanui, Jeremiah KiplagatIn recent years, Photovoltaic (PV) power generation has been receiving considerable attention as one of the promising energy alternatives for rural areas in developing countries. However, their widespread adoption has been hampered by the high capital cost and low conversion efficiencies of the available systems. Incorporation of a solar concentrator has been found by a number of researchers to increase the electrical power output of a PV module. However it exceedingly raises the module temperature, consequently lowering further its conversion efficiency. The study was carried out to improve the conversion efficiency of an amorphus silicon PV module and to reduce the cost per unit output of the energy generated. This was done by incorporating a Cooling Unit (CU) and a Compound Parabolic Concentrator (CPC) to the PV module, forming a Combined Heat and Power (CHP) system generating electricity and hot water. By circulating a fluid with a lower inlet temperature at the back surface of a PV module, heat is extracted from the PV module, thus maintaining the module cell temperatures at a lower level. This improves the electrical conversion efficiency of the cells. The extracted heat can be directed into useful purposes. This forms a Combined Heat and Power (CHP) PV system. Use of low cost concentrators on a CHP system increases the radiant energy available per unit surface of the module resulting in lower cost per unit of energy generated. Four experimental system were investigated: (i) Plain PV module (ii) PV module with cooling unit (PV/CU) (iii) PV module with a CPC (PV/CPC) and (iv) PV module with a CPC and a Cooling Unit (PV/CPC+CU). Water was used as the cooling agent at a controlled flow rate. Three flow rates of 20 l/hr and 40 l/hr were tested in the study. Data collected were: current, voltage, solar radiation, ambient temperature, module temperature, and the inlet and outlet cooling water temperatures. A data logger (model Fluke 2286 series, U.K) was used to record data continuously at regular intervals from 9.00AM to 5.00PM. The power output, electrical and thermal efficiencies for the various study modules were computed and compared. Financial evaluation was performed by comparing the Levelized Energy Cost (LEC) of the systems tested. The results obtained indicated that the cooling of a 51Wp PV module increases its electrical conversion efficiency. The PV module was cooled by an average of 14°C from 48.5°C to 34.4°C, which increased the electrical power output and efficiency by 45.6% and 37.5% respectively. Combined CPC and cooling showed better electrical performance on the PV system than either the CPC or cooling alone. In total, an integrated CPC/CU had the best performance at a colling water flow rate of 40 l/hr, which increased the electrical power output and efficiency by 118.74% and 120.0% respectively in comparison to PV Plain. The 25% truncated CPC also increased the thermal energy output of the combined heat and Power (CHP) PV system. The maximum thermal energy output was observed at a cooling water flow rate of 30 l/hr. At this point the thermal energy output was 3.018 KWh/day. This study has shown that a CHP-PV system with added CPC increased the electrical power output of conventional PV modules with the benefit of generating useful heat energy in the process. These findings are important contributions in the research efforts aimed at increasing the acceptability and affordability of solar technology in the rural areas of developing countries.Item Design of a solar tracking concentrator system for process heat generation(2011-12-07) Githuku, Simon MwangiIn Kenya, biomass energy accounts for 75% of the energy consumed for domestic heating and industrial process applications. This has lead to massive deforestation and environmental degradation. In seeking solutions, this project was undertaken to develop a solar concentrating system for process heat generation in Kenya. The goal of the study was to design, construct and evaluate the thermal performance of the solar tracking concentrator for process heat generation. The solar tracking concentrator was designed, constructed and tested under field conditions in Kenya from February to August 2004. About 70 trials were conducted to investigate its thermal performance. The system components included rotating support structure, tracking unit with cylinders loaded with evaporative solvents, collector assembly (parabolic concentrator and receiver) and heat recovery unit. Locally available materials (including shock absorbers, solvents, square metal tubes & plywood) were used to construct the system. The measured parameters included solar radiation, ambient temperature, wind speed, tracking cylinders temperatures, water inlet and outlet temperatures, water flow, air inlet and outlet temperatures, airflow and tracking angle. The tracking unit utilized solvents for its operation. Three types of solvents used included chloroform, carbon tetrachloride and methylated spirit. The tracking angle was read and recorded manually at a regular interval of 10 minutes. Average process temperature ranging between 41.8 ± 9.7°Cand 59.3 ± 147.7°C was generated with an average insolation of 665 ± 302.1 W/m2 and 684.4 ±147.7 W/m2 for the non-tracking and the solar tracking systems respectively. From 70 field tests conducted in Kenya with system loaded with methylated spirit, chloroform and carbon tetrachloride the following was concluded: (a) Chloroform solvent with an average tracking accuracy of 82+13.2% proved to be better than that of carbon tetrachloride that had tracking accuracy of 74.1± 2.5%. (b) The use of mirrors on the solar concentrator's surface and integration of a solar tracking system increased the thermal efficiency by an average of 9.0 ± 1.5%. (c) Concentrating system loaded with chloroform showed potential to generate 82.5± 5kWh per day when operating with averaged solar radiation of 644.3 ± 30.5 kW/m2. (d) The solar tracking concentrator loaded with chloroform solvent demonstrated great potential for use in process heat generation, industrial and agricultural drying operations in sunny countries.Item Modern technology adoption trends of small and medium electrical/electronics manufacturing enterprises registered in Nairobi(2011-12-01) Magu, David M.Growth in the manufacturing sector is widely considered a great vehicle for economic development, a fact taken up by Kenyan policy makers by setting a policy of ensuring industrialization by the year 2020. However, as evidenced by the case of newly developed countries, meaningful industrial development is preceded by technological advancement. In Kenya, performance of the manufacturing sector has been on a decline in the last decade. This has been attributed to lack of adequate technical and entrepreneurial skills coupled with inadequate research and development, which constrained technological advancement. In the Electric and Electronic sub-sector, most of the enterprises have engaged in production of traditional electrical products such as electric cables, lamps, electrodes and fans. Only a few have been involved in the manufacture of the more modern and high growth potential products such as computation, automation and communication equipment. Yet, studies in more successful economies, such as USA and South Korea, have shown manufacture of modern and dynamic electric and electronic products to be the growth vessel in the subsector. This study focused on modern technology adoption efforts by the Small and Medium Electrical and Electronics Manufacturing Enterprises (SMEEMEs) in Nairobi. The main objective was to find out how the SMEEMEs in Nairobi, and by extension, Kenya, can build up their technological capabilities which would in turn raise their product quality, productivity, product variety and engage in production of the modern high growth potential products. The study was carried out between May and December 2004, in Nairobi industrial area, Parklands and Baba Dogo road, among fourteen electric and electronic manufacturers that employed between 10 and 249 workers. The researcher, through face-to-face interviews, conducted data, collection with the entrepreneurs, using interview guides. Descriptive statistics were used for data analysis and presentations. All the SMEEMEs were found to be engaged in the manufacture of the earlier generation products, except 14% who were also manufacturing the modern generation products. Though some firms in the manufacture of the earlier generation products were equally doing well as those in both the earlier and the modern generation, it came out clearly that those firms that were encroaching on modern technology practices as indicated in the status of their machinery, their new products, their product development methods and their skills upgrading approaches, were thriving and had high plans and hopes for future growth. However, 43% of SMEEMEs showed little or no tendency towards improved technological activity and were just coping and others struggling in the globalized market where `survival for the fittest' bluntly applies. Of the constraints facing the SMEEMEs, competition from imports was cited as the number one most severe constraint by 8_5.7% of the SMEEMEs, while lack of adequate financial resources was ranked second by a similar. percentage. Poor utilities were ranked third by 71.43% of the firms. However, 14% of the SMEEMEs that were more technologically advanced highlighted the problems of lack of markets for the high technology products and lack of trained manpower. Taking the sub-sector as a whole, the study found out that the technology upgrading methods that had spurred tremendous growth in the sub-sector in the newly developed countries, such as joint ventures, foreign direct investment and hire of technical licenses/contracts, were hardly exploited. Most of the firms emphasized on research and development, and acquisition of hardware for their new technology requirements, which were in turn limited by the constraints mentioned above. Recommendations from the study were that, first, further improvement of the enabling environment be done, especially through macro-economic interventions, and establishment of more deliberate technology upgrading initiatives such as a national technology foresight programme and establishment of technology parks. Secondly, individual firm initiatives are required to take advantage of the enabling environment and following conventional best manufacturing practices such as new product development and agility.