Numerical and experimental performance analysis of PCM based photovoltaic thermal system / Fayaz Hussain

Fayaz , Hussain (2019) Numerical and experimental performance analysis of PCM based photovoltaic thermal system / Fayaz Hussain. PhD thesis, Universiti Malaya.

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Abstract

Climate change due to global warming is the major on-going concern among the scientists and governments. Fossil fuels play the major role in both global warming and world’s mainstream energy resources on which global economy is almost fully dependent. However, these harmful fossil fuels are fast depleting, creating the situation of low supply and high demand along with environmental pollution. Therefore, many researchers from all over the world have researched new energy sources, which are clean and non-depleting. Abundantly available solar energy is the best option of harnessing clean and non-depleting energy among the other renewable energy resources. Irradiations incident on the photovoltaic module are not fully converted into electrical energy as PV modules convert only 15-20% with the rest are lost into heat conversion. Incorporation of thermal collectors into photovoltaic panels has two-fold advantages of increasing PV module efficiency through highest irradiations and hot water for different applications. However, low heat transfer from PV module to the thermal collector and other technical complications result in the overall reduced performance of the system. There is still need of research numerically based on 3D models to understand and investigate their performance thoroughly. Heat transfer of the system greatly depends on the design and material of the thermal collector and flow path of working fluid along with its method/technic of contact with PV module. To deal with these problems, a new design of thermal collector has been introduced for increasing the efficiency of the photovoltaic system regarding electrical energy as well as thermal. Nanofluid as multi-walled carbon nanotubes/water (MWCNT/water) is also used as working fluid to additionally investigate the performance of PVT with nanofluids. Furthermore, phase change materials (PCM) are added in the photovoltaic thermal system for studying enhanced low cell temperature and stable thermal management as compared to the photovoltaic thermal system. COMSOL Multiphysics® has been used for 3D numerical investigation of the proposed systems based on the finite element method. Numerical optimum results are validated with indoor and outdoor experimental data of fabricated PV, PVT and PVT-PCM systems with aluminium heat exchanger simultaneously with the indoor controlled environment and outdoor natural weather. Effect of parameters such as irradiation level and mass flow rates are thoroughly examined in numerical and experimental studies. For indoor case, the maximum overall efficiency of PVT and PVT-PCM systems is obtained as 92.24% and 88.32% at 200 W/m2 and 0.5 LPM with ambient and inlet water temperatures of 27°C experimentally. For outdoor case, the maximum overall efficiency of PVT and PVT-PCM systems is obtained as 88.95% and 85.53% at 200 W/m2 and 0.5 LPM with ambient and inlet water temperatures of 32°C experimentally. It has been found that PVT-PCM system is efficient in electrical performance. However, PVT system is efficient in thermal energy gain into water. For electrical efficiency requirements, PVT PCM is a better candidate, whereas, PVT system is suitable where higher thermal energy is required as compared to electrical energy.

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