Analysis of photovoltaic thermal performance using single and multiphase models of nanofluid flow

Abstract

The world faces a severe energy crisis due to limited non-renewable sources and increasing demand. COVID-19 and Ukraine-Russia conflict disrupt energy supply, causing shortages and price hikes. Experts suggest reducing reliance on fossil fuels and promoting clean energy sources like PV/T systems. Despite extensive research on PV/T system such as design, materials, working fluid, there is no uniform design or performance analysis for different flow regimes and nanofluid multiphase flow. This study aims to optimize PV/T system performance using single and multiphase models of nanofluid flow, addressing current challenges and promoting sustainable energy sources. At the very beginning of this study, a novel literature analysis of PV/T research named scientometric analysis is performed to findout the research gaps on this vast field of PV/T systems research. Then,a 3D nine-layered flat plate PV/T system with a rectangular shape collector is considered. Firstly, the PV/T performance is analyzed for different flow regimes: creeping flow, laminar flow, and transitional flow using water as the cooling fluid. Secondly, the study is undertaken for the same PV/T system and flow regimes, employing a water based multiwalled carbon nanotube (MWCNT) nanofluid as the cooling fluid. Thirdly, in the same system for same flow regimes performance is evaluated utilizing a kerosene based MWCNT nanofluid as the cooling fluid. At the fourth step, month-wise performance is evaluated using meteorological conditions of Dhaka, Bangladesh for MWCNT/water-based nanofluid and the laminar flow regime arising fromearlier results. Finally, the PV/T performance of nanofluid single-phase and multiphase flow (Mixture model) using water based MWCNT nanofluid is analyzed. In addition, the summer season of Dhaka, Bangladesh and laminar flow regime are taken stemming from previous results for varying Reynolds number (Re = 200 to 1000) and solar intensity (G = 200W/m2 to 1000W/m2). The software SolidWorks is used to model the geometry. Finite element based COMSOL Multiphysics® software version 5.4 is utilized for numerical simulation. Governing equations of the solid and fluid domain along with associated boundary conditions for both single and multiphase models of nanofluid flow is considered using water and MWCNT based nanofluid. An appropriate model for thermal conductivity and viscosity of nanofluid is used considering nanoparticles, based on shape and size. The thermal, electrical and overall performance of the system are analyzed for Dhaka, Bangladesh under operational and climatic conditions. The performance of the PV/T system such as cell temperature, the outlet temperature of the fluid domain, thermal, electrical and total efficiencies, and energy are presentedin terms of 3D surface plots, tables, and line diagrams.Furthermore, regression analysis of electrical efficiency and thermal efficiency are discussed for input variablesReynolds number and solar irradiation. Empirical results indicate that electrical efficiency decreases from 11.34% to 8.09% for creeping flow, 12.16% to 11.77% for laminar flow, and 12.24% to 12.07% for transitional flow when solar intensity rises from 200W/m2 to 1000W/m2. In addition, the results suggested that transitional flow is the most efficient, followed by laminar flow. However, compared to creeping flow, the difference between laminar and transitional flow is less significant. Results indicated that cell temperature and outlet temperature decline with the increased Reynolds number as a result efficiencies rise with the increased value of the Reynolds number. Month to month variation also has a considerable impact on photovoltaic thermal performance. Moreover, the nanofluid multiphase flow (mixture model) exhibits comparatively better efficiency than the nanofluid single-phase flow. Comparisons are presented with previously published work and the results are found to be in excellent agreement. This study will help to predict a better model for the PV/T system between nanofluid single phase and multiphase flow. Moreover, solar thermal heating, building-integrated photovoltaics, thermal science, industrial and residential cooling system communities would benefit from this study. Additionally, this study will perform as a reference work to install PV/T systems and other relevant renewable solar energy sources in Bangladesh or similar climateconsidering the meteorological effect.