Due to rapid industrialization and urbanization, upward rise in carbon emissions in the atmosphere, and depletion of fossil fuel and gas reserves have forced to find alternative renewable energy resources, where solar energy is one of the most promising source. Parabolic trough solar collectors (PTCs) can effectively transfer high temperature in the tube of receiver upto 400 °C. In this study, Computational Fluid Dynamics (CFD) analysis is used to analyse the effect of multiple working fluids on efficiency of the PTC. Two different types of nanofluids used for analyising the thermal efficiency of PTC through CFD simulations, are Alumina and Copper-oxide nanofluids. The concentration of Copper Oxide and Alumina was kept to 0.01% in the nanofluids. The efficiency for PTC is calculated at two different mass flow rates i.e., 0.0112 Kg/s and 0.0224 Kg/s. The highest efficiency is 13.01 and 13.1% using Al 2 O 3 as nanofluids at 0.0112 Kg/s and 0.0224 Kg/s flow rates, while CuO has an efficiency of 13.92% and 14.79% for these flow rates. The behaviour of absorber tube material on temperature distribution for steel, copper and aluminum as absorber tube material was also investigated. Changing the material from steel to copper and aluminum increased the outlet temperature of the fluid. The maximum output temperature was achieved for copper is 311 K while steel and aluminum showed lower temperature of 307 K and 308 K of the fluid at the outlet. Furthermore, the impact of the receiver tube’s length on the working fluid’s temperature is also studied. Copper Oxide nanofluid has higher temperature at the outlet for both mass flow rates as compared to alumina nanofluid. Accordingly, a comparison was made for the CFD results with the experimental findings from literature. The nanofluids based PTCs system is promising method for the sustainable environment applications. 

Thermal performance enhancement of nanofluids based parabolic trough solar collector (NPTSC) for sustainable environment

The paper presents a detailed study based on the energy and exergy analysis of a combined cycle power plant (CCPP) Guddu having triple pressure heat recovery steam generator (HRSG). The energy loss...

Energy and exergy analysis of a 747-MW combined cycle power plant Guddu

Synthesis, characterization and application of mono-, hybrid and ternary nanofluids in hybrid photovoltaic thermal (PV/T) solar systems—a review


 Hybridising photovoltaic and photothermal technologies into a single system that can simultaneously deliver heat and power represents one of the leading strategies for generating clean energy at more affordable prices. In a hybrid photovoltaic-thermal (PVT) system, the capability to modulate the thermal and electrical power output is significantly influenced by the spectral properties of the heat transfer fluid utilised. In this study, we report on one of the first experimental evaluations of the capability of a multimodal silver nanofluid containing various particle shapes and particle sizes to selectively modulate the solar energy for PVT applications. The diverse set of particle properties led up to a 50.4% enhancement in the solar energy absorbed by the nanofluid over the 300 nm – 550 nm spectral region, where silicon is known to exhibit poor photovoltaic conversion performances. This improved substantially the absorption of solar energy, with an additional 18 – 129 W m-2 of thermal power being generated by the PVT system. Along with the advancements made in the thermal power output of the PVT system, a decrease of 4.7 – 36.6 W m-2 in the electrical power generated by the photovoltaic element was noted. Thus, for every ~11 W m-2 increase of thermal power achieved through the addition of the nanoparticles, a reduction of ~3 W m-2 in the ability to generate clean electricity was sustained by the PVT. Despite the energy trade-offs involved under the conditions of the nanofluid, the PVT system cumulatively harvested 405 W m-2 of solar energy, which amounts to a total conversion efficiency of 45%. Furthermore, the economics of the additional energy harvested through merging of the two systems was found to reach an enhancement of 77% under certain European conditions.

Evaluation of the Potential of Nanofluids Containing Different Ag Nanoparticle Size Distributions for Enhanced Solar Energy Conversion in Hybrid Photovoltaic-thermal (PVT) Applications



This review describes the basic and application aspects of the optical properties of nanoparticles (NPs), which determine the dynamics and results of optical (laser) radiation interaction with NPs and their surroundings through NP light absorption and heat generation. In addition to the importance of primary optical processes, the thermal application of the light–NP interaction has attracted significant interest from various areas ranging from photochemistry to laser material processing and nanobiomedicine. First of all, the information provided is intended for laser specialists, photochemists and nanobiologists who are not so familiar with various optical data for understanding of the influence of NP optical properties on the results of optical or laser action on NPs and medium. Secondly, our review will be useful for researchers who conduct high-temperature investigations of the intense optical action on NPs that needs to take into account the dependence of NP optical properties on its temperature under NP heating.
Our attention is focused on two variants of the applications of NP optical properties. Firstly, we shortly reviewed the optical properties of NPs at their initial or slightly higher temperatures reached under the influence of moderate radiation intensity. They are presented in numerous publications and are used as basic data. On the other side, the development of modern high-temperature laser and optical technologies needs to use the NPs optical properties at temperatures of about 1x103 K and more. For high power laser and optical technologies, it is necessary to take into account the temperature dependences of the optical parameters of various metals, dielectrics and other materials. Among these technologies, one should list laser processing of NPs, thermal laser biomedicine, solar and photo nanocatalysis, solar nanostructured absorbers. The selection and use of suitable optical properties of NPs are crucial to successful achievements and results in high-temperature experiments and applications. 
Novel information on optical property dependence on temperature obtained from currently available literature has been presented for possible applications in optical and laser high-temperature processes interactions with NPs. However, unfortunately, the essential information on the effect of temperature on the optical properties of NPs is currently limited. In addition to the latest information, this review also includes the figures obtained by our own calculations to provide readers with a better understanding of the NP optical properties. 
From the side of the application, the use of NP optical properties is considered, which provide multiple varieties of moderate and high-temperature technology opportunities, many of which are ongoing and some of them are promising bright results in the near future. The beneficial outcome and the results of further activities in the research of intense laser and optical interactions with NPs can influence various fields of science and technology: nano and photochemistry, biomedicine, nanophysics, material science, etc.


Optical properties of nanoparticles dispersed in ambient medium and their dependences on temperature

The convective and conductive heat transfer between the solar collector and working fluids make the photothermal performance limited, a higher rate of heat loss occurs from the surface of the conventional absorber to the surroundings. Direct absorption solar collectors (DASC) are a favorable alternative for improved photothermal performance. In this study, simulation based on the performance of a nanostructured solar collector has been carried out using TRNSYS. The connective and conductive heat transfer from direct solar collectors were improved by using nanofluids, three different nanostructured materials, including CuO, GO and ZnO was used in this study. The analysis determines the outlet temperature of the working fluids passed through the direct solar collector. The TRNSYS model consists of a direct solar collector and weather model for Lahore city, the simulations were performed for the whole year for 1440 hours. The stability of these nanostructured materials in the water was investigated by using UV-spectrometer. Various performance parameters of direct solar collectors were determined, such as variation in outlet collector temperature, heat transfer rates. The numerical model has been validated with experimental results. The maximum outlet temperature of 63℃ was observed for GO based nanofluids. The simulation results show that for the whole year, nanofluids improved the performance of direct solar collectors. A significant improvement in the heat transfer rate of 23.52%, 21.11%, and 15.09% was observed for the nanofluids based on nanostructures of CuO, ZnO, and GO respectively, as compared to water. These nanostructured energy materials are beneficial in solar-driven applications like solar desalination, solar water, and space heating.

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Performance investigation of a solar thermal collector based on nanostructured energy materials

Most of the engineering analyses and energy balance of control volume systems are based upon the first law of thermodynamics which asserts that the work, energy and heat are interconvertible and there is no distinction among them. On the other hand, second law of thermodynamics states that these forms of energy do not have same quality. They are quantitatively same but qualitatively different, i.e., at different temperatures the heat transfer from a system to another having same temperature gradient is different. The measure of energy quality is known as exergy.  Exergy is the maximum extractible work from a thermodynamic system in equilibrium with its surroundings and it is the index of perfectness of a thermal system. This paper presents the exergy and energy analyses of different components of Nishat Power Limited, Pakistan. The plant is consists of a 200 MW combined cycle thermal power plant, 11 compression ignition engines (17 MW each) and one steam turbine of 15 MW. Discrete analysis of individual components of the system to calculate energetic and exergetic losses based on data from the power plant running at full capacity has been performed.   The loss of energy to the environment in steam generator and turbine have been noted as 561.18 kW and 114.12 kW, respectively. A comparison between energetic losses and exergetic losses has also been presented.

Rabia Shoukat

Papers

Performance investigation of a solar thermal collector based on nanostructured energy materials

Energy and Exergy Analysis of a 200 MW Combined Cycle Thermal Power Plant