| Globally,sustainable energy support continued to advance alongside raising awareness of the multiple benefits of renewable energy sources,including curbing greenhouse gas emissions,along with bridging the gap between Energy supply and demand.Among these sources,solar energy has gained great momentum by reducing cost,availability anywhere,and enhancing system efficiency.By 2050,solar energy is expected to be the largest source of power generation globally,but this transition will not be seamless and certain difficulties are faced.Besides,the diversity of solar energy uses has attracted many scientists and engineers to maximize the efficiency of solar-harvesting technologies.Hybrid photovoltaic/thermal(PV/T)systems are one of the promising solutions that have the potential to harvest electrical power and thermal energy from the solar spectrum simultaneously,where they are able to cogenerate electricity and heat with total efficiencies of nearly 70%.These hybridized systems require developed thermal fluids able to act as efficient coolants and/or spectral-filters by controlling the thermal and electrical components of the solar spectrum.Although numerous investigations proposed various nanofluid filters,the selection of basefluid-nanoparticle combination dramatically affects the performance of hybrid PV/T systems.Hence,a series of parametric studies have been carried out to investigate the hybrid PV/T system performance by employing different base fluid-nanoparticle combinations.This thesis explores the effects of different nanoparticle concentrations,volume flow rates of applied nanofluids,as well as the solar spectrum intensities on the energetic and exergetic performances of the proposed module.Merit functions for various basefluid or nanofluid based hybrid PV/T systems are also assessed in order to determine their economic feasibility.It is shown that the suspension of nanoparticles into basefluids has a considerable influence on the radiative heat fluxes that are absorbed by each component of such system.The selection of basefluid-nanoparticle combination is dramatically affected by the desired energy form,based on the system energetic and exergetic performances.Further,the employment of liquid absorptive filters in such systems can realize a higher energy output which is 179%-240%of that of a stand-alone PV system.Adding to this,several studies have strived to develop the optical performance of thermal fluids for peaking the optical window of the PV,however,maximizing their heat-transfer capabilities have not gained widespread attention.Therefore,special attention is paid to provide the appropriate thermal-optical selective criteria of liquid spectral-filters under various solar concentrations(CRs)using a precisive 3D optical-thermal coupled numerical model.The results revealed that using liquid filters with high thermal conductivity(k)and heat capacity(Cp)jointly has the potential to improve the total solar energy conversion in all CRs.Whereas low k and Cp thermal fluids have the preference under low CRs and vice versa in high CRs from the exergy viewpoint.Besides,the presence of high thermal absorption filters above the undesired PV-wavebands promotes co-conversion efficiency across all CRs,while the high permeability filters over the spectral window of PVs are recommended from the exergy viewpoint.For further improvement of concentrated hybrid PV/T systems,a simulation method combining the multiphysics fields is necessary to accurately analyze the optical,thermal,and electric performance.Herein,a three-dimensional numerical study has been conducted on a low concentrated photovoltaic/thermal system utilizing a heat transfer fluid as the cooling medium and a compound parabolic concentrator as the mirror field.A finite volume(FV)-CFD code has been employed to simulate the entire model,where the optical modelling is validated theoretically with the Monte Carlo ray-tracing method.The influences of employing various heatsink designs and coolants are numerically investigated.Good compatibility with the empirical data is obtained when the appropriate modelling tunings are applied.It is also shown that,on a typical day,the total energy and exergy efficiencies of the system are up to 57.66%and 7.94%,respectively.Prior to implementation broadly,the realistic numerical modelling of multiphysics applications is an efficient way to precisely predict the operation of hybrid solar architectures(e.g.concentrated spectral beam splitting PV/T hybrid systems).Although many multiphysics conjugating approaches have been proposed in the literature,it is difficult to adopt such methods into simulating complex CPV/T systems.Consequently,this study also introduces novel numerical optical,thermal and electric coupling methods for hybrid compound parabolic concentrator photovoltaic/thermal(CPC-PV/T)collectors based on optical-filtering and/or lost heat recovery technologies.The main features of the proposed coupling methods are extensively analyzed and compared with the other coupling methods previously adopted.From findings,the proposed Full Coupling Method(FCM)can be applied to reveal more realistic operation characteristics of the hybridized system compared with the other approaches,since the FCM can take into account the non-uniformity of solar illumination and the direction of reflected solar beams upon the receiver,along with the variation in the optical characteristics of utilized materials over the solar irradiance.Additionally,suspending nanoparticles into the BF-filter raises the absorption rate over the thermal-bands with 62.5%higher than the use of BF-filter individually,whilst the cell temperature and the transmitted irradiance within the PV-band are obviously declined. |
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