Muzaffar Ali

Comparison of Performance Measurements of Photovoltaic Modules during Winter Months in Taxila, Pakistan

This paper presents the comparative performance evaluation of three commercially available photovoltaic modules (monocrystalline, polycrystalline, and single junction amorphous silicon) in Taxila, Pakistan. The experimentation was carried out at outdoor conditions for winter months. Power output, module efficiency, and performance ratio were calculated for each module and the effect of module temperature and solar irradiance on these parameters was investigated. Module parameters showed strong dependence on the solar irradiance and module temperature. Monocrystalline and polycrystalline modules showed better performance in high irradiance condition whereas it decreased suddenly with decrease in irradiance. Amorphous solar module also showed good performance in low irradiance due to its better light absorbing characteristics and thus showed higher average performance ratio. Monocrystalline photovoltaic module showed higher monthly average module efficiency and was found to be more efficient at this site. Module efficiency and performance ratio showed a decreasing trend with increase of irradiance and photovoltaic module back surface temperature.

Performance Investigation of Air Velocity Effects on PV Modules under Controlled Conditions

Junction temperature of PV modules is one of the key parameters on which the performance of PV modules depends. In the present work, an experimental investigation was carried out to analyze the effects of air velocity on the performance of two PV modules, that is, monocrystalline silicon and polycrystalline silicon under the controlled conditions of a wind tunnel in the presence of an artificial solar simulator. The parameters investigated include the surface temperature variation, power output, and efficiency of PV modules under varying air velocity from near zero (indoor lab. conditions) to 15 m/s. Additionally, the results were also determined at two different module angular positions: at 0° angle, that is, parallel to air direction and at 10° angle with the direction of coming air to consider the effects of tilt angles. Afterwards, the thermal analysis of the modules was performed using Ansys-Fluent in which junction temperature and heat flux of modules were determined by applying appropriate boundary conditions, such as air velocity, heat flux, and solar radiation. Finally, the numerical results are compared with the experiment in terms of junction temperatures of modules and good agreement was found. Additionally, the results showed that the maximum module temperature drops by 17.2°C and the module efficiency and power output increased from 10 to 12% with increasing air velocity.

Design optimization and experimental investigation of solar assisted 1 Ton (3.516 KW) vapor absorption air conditioning system

Solar Energy is one of the most attractive and well-known source among all known renewable energy resources therefore, solar assisted air-conditioning systems attract researchers interests. Solar cooling technology is environment friendly and contributes to a significant decrease of the CO2 emissions which cause the greenhouse effect and thus helpful in reduction of Ozone depletion. According to the operating temperature of driving thermal source, single - effect Li Br/H2O absorption chillers have the advantage of being powered by ordinary flat-plate or evacuated tube solar collectors available in the market. The objective of this work is to develop an experimental rig based on the simulation results of an optimized - single-effect absorption air conditioning system using LiBr/H2O solution as working fluid assisted by solar thermal energy. Detailed mathematical design is prepared by applying energy and mass balances on each component. Afterwards parametric analysis is performed on EES to determine the effects of evaporator temperature, condenser temperature, and generator temperature on COP of the system. Then simulation based optimization of the proposed design is conducted on dynamic simulation program TRNSYS and GenOpt, based on local weather profile of Taxila. The results of the simulation of the absorption chiller indicate a thermal performance coefficient, COP of 0.756. The results of the simulation are validated by the locally fabricated experimental rig.

Small-Sized Parabolic Trough Collector System for Solar Dehumidification Application: Design, Development, and Potential Assessment

The current study presents a numerical and real-time performance analysis of a parabolic trough collector (PTC) system designed for solar air-conditioning applications. Initially, a thermodynamic model of PTC is developed using engineering equation solver (EES) having a capacity of around 3 kW. Then, an experimental PTC system setup is established with a concentration ratio of 9.93 using evacuated tube receivers. The experimental study is conducted under the climate of Taxila, Pakistan in accordance with ASHRAE 93-1986 standard. Furthermore, PTC system is integrated with a solid desiccant dehumidifier (SDD) to study the effect of various operating parameters such as direct solar radiation and inlet fluid temperature and its impact on dehumidification share. The experimental maximum temperature gain is around 5.2°C, with the peak efficiency of 62% on a sunny day. Similarly, maximum thermal energy gain on sunny and cloudy days is 3.07 kW and 2.33 kW, respectively. Afterwards, same comprehensive EES model of PTC with some modifications is used for annual transient analysis in TRNSYS for five different climates of Pakistan. Quetta revealed peak solar insolation of 656 W/m2 and peak thermal energy 1139 MJ with 46% efficiency. The comparison shows good agreement between simulated and experimental results with root mean square error of around 9%.

Thermal analysis of a mini solar pond of small surface area while extracting heat from lower convective layer

Solar energy is major renewable energy resource which can potentially fulfill 100% energy demand of the world while releasing no polluting agents to the atmosphere in contrast to the conventional fossil fuels. However, due to its intermittent nature, solar energy requires effective storage of energy for utilizing during the night and cloudy weather. A solar pond is a promising solution because it has its own energy storage which is suitable for low temperature application like building heating and cooling. This paper presents a thermal analysis of a salt gradient solar pond while extracting heat from the lower convective zone. A mathematical model of surface area is developed. Efficiency analysis is performed numerically using a MATLAB code for steady temperature difference of 30°C as well as 20°C across the gradient layer for three different pond sizes of depths 1.5 m, 1.0 m, and 0.5 m. The thermal efficiency of first pond of 1.5 m depth varies from around 21% in summer to 11% in winter. Thermal efficiency of solar pond drops significantly by reducing its size and non-convective zone thickness. Annual average efficiencies are 21%, 19%, and 9.5% for the three ponds of 1.5 m, 1.0 m, and 0.5 m depths, respectively. So it is recommended to prefer a pond of 1.5 m over others. However, the efficiency of smaller the pond can be significantly improved by compromising on quality the of thermal energy, efficiency of 0.5 m pond rises to 17% when operating at temperature just 20°C above ambient, compared with 9.5% for 30°C above ambient. Solar pond therefore proves to be suitable for effectively utilizing solar energy and can present an effective solution for low temperature energy needs like space heating.

Variation of Heat Flux at Lower Frequencies of Vibration in a Vibrated Granular Bed

Granular flows in vibrated bed exhibit various physical phenomena primarily driven by vibrating base. As the vibrating surface is the only source of energy in an otherwise dissipative flow, most of the theoretical models relate the steady state energy input to the RMS velocity of vibration. Here variation of heat flux is studied at varying frequency of vibration while keeping the RMS vibration velocity and the cell loading constant. Using single particle analysis and MD simulations, an extended version of grain-base collision is observed resulting in the reduction of heat flux at lower frequencies (<50 Hz) of vibration. The presented findings are important as most experimental studies are reported at these frequencies of excitation.