Parabolic trough solar collectors (PTSCs) are generally utilized to reach high temperatures in solar-thermal applications. The current work investigates entropy production analysis and the influence of nano solid particles on a parabolic trough surface collector (PTSC) installed within a solar powered ship (SPS). For the current investigation, the non-Newtonian Maxwell type, as well as a porous medium and Darcy–Forchheimer effects, were used. The flow in PTSC was produced by a nonlinear stretching surface, and the Cattaneo–Christov approach was used to assess the thermal boundary layer’s heat flux. Similarity transformation approach has been employed to convert partial differential equations into solvable ordinary differential equations allied to boundary conditions. Partial differential and the boundary conditions have been reduced into a group of non-linear ordinary differential equations. A Keller-box scheme applied to solve approximate solutions of the ordinary differential equations. Single-walled carbon nanotubes -engine oil (SWCNT-EO) and Multiwalled carbon nanotubes/engine oil (MWCNT-EO) nanofluids have been utilized as working fluid. According to the findings, the magnetic parameter led to a reduction in the Nusselt number, as well as an increment in skin friction coefficient. Moreover, total entropy variance over the domain enhanced for flow rates through Reynolds number and viscosity fluctuations were monitored by using Brinkman number. Utilizing SWCNT-EO nanofluid increased the thermal efficiency between 1.6–14.9% in comparison to MWCNT-EO.

In the current paper, different thermal energy storage unit-integrated photovoltaic thermal (PVT) air collectors with and without nanoparticles have been designed, fabricated and tested. Aluminum oxide nanoparticles have been integrated into the thermal storage unit to increase the performance of the PVT collector. The developed collectors have been tested in a drying application at two different mass flow rates. The major goals of this work are upgrading the performance of the PVT air collector by employing a nano-embedded thermal energy storage unit and analyzing the impacts of using nanoparticles in the latent heat storage unit in the PVT collector on the drying performance of the system. The drying time was reduced by approximately 15–22% by employing nanoparticles in the thermal storage unit. Moreover, overall exergy efficiency values were obtained in ranges of 12.49–14.67% and 13.64–16.06%, respectively, for modified and unmodified PVT air collectors. It should be indicated that the overall energy and exergy efficiencies of the PVT air collectors were improved in the ranges of 6.91–6.97% and 9.20–9.47%, respectively, by using nanoparticles in the thermal energy storage unit. The combination of increasing the flow rate and integrating nanoparticles into the storage unit improved the overall exergetic efficiency of the PVT air collector by 28.58%. The mean exergetic efficiency of the drying room was between 48.33 and 54.26%. In addition to the experimental analysis, dynamic models for thermal and exergy efficiencies of developed collectors were constructed by employing the system identification method.

Solar desalination systems are effective and sustainable applications that are utilized to obtain potable water from saline or contaminated water. In this research, three solar desalination systems, including a conventional system, a phase change material (PCM)-based thermal energy storage unit (TESU), and a natural dolomite powder integrated PCM-based TESU, were structured and experimentally investigated. The developed solar desalination systems were analyzed simultaneously and the findings were discussed in detail. According to the empirically obtained outcomes, utilizing PCM-based TESUs and dolomite-powder-embedded PCM-based TESUs increased daily cumulative productivity by 10.15% and 17.70%, respectively, in comparison to the conventional distiller. Employing dolomite powder increased the energy and exergy efficiencies of the conventional distiller from 15.91% to 18.28% and from 1.26% to 1.78%, respectively. Moreover, environmental metrics such as global warming potential and the sustainability index of the developed solar desalination systems were analyzed within the scope of this work.

In this work, numerical and experimental analyses of a double-pipe heat exchanger with SiO₂ nanoparticles were performed. The numerical study was conducted by using the k-e turbulence model with the Galerkin weighted residual finite element method. The nanofluid was used in the inner pipe at various solid particle volume fractions. Effects of flow rate and temperature on the overall heat transfer coefficient were examined. The Brownian motion effect was included in the effective thermal conductivity of the nanofluid. It was observed that the overall heat transfer coefficient enhanced with the inclusion of nanoparticle and increasing the volumetric flow rate of nanofluid. Even though the validation of the experimental study was conducted, there are discrepancies between the numerical and experimental studies which become higher for a higher mass flow rate. The deviations are 4.60% and 27.50% at volumetric flow rates of 0.87 L/min and 2.15 L/min.

This study aims to upgrade the effectiveness of unglazed solar air heating walls (SWs) using mesh packing and nano-enhanced black paint. In this regard, two SW cases with 10 cm and 15 cm plenum thicknesses have been fabricated and tested simultaneously with different modifications. In other words, six different SW configurations have been designed and empirically investigated in this research. Unmodified SWs with two plenum thicknesses have been tested in the first experiment. Iron meshes have been utilized in both SWs in the second test. In the third experiment, the impact of the combined usage of mesh packing and Fe (iron) nanoparticle-enhanced black paint (absorber coating) at 2% w/w concentration on the performance has been evaluated. Experimental results exhibited that the combined usage of mesh packing and nano-doped paint in the SWs with 10 cm and 15 cm plenum thicknesses improved the average effective efficiency value by 29.54% and 31.20%, respectively, compared to the unmodified cases. Also, the average exergy efficiencies of the six tested SW configurations were attained in the range of 6.24–12.29%. Moreover, the findings of this study showed that reducing the plenum thickness and applying the combination of meshes and nano-coating improved the annual carbon dioxide savings by 44.72%.

Waste production is an important problem for the developing world and globalization. The waste materials can be reused through recycling process and its environmental effects can be minimized. Utilizing renewable energy sources at the maximum level is also an important issue for a sustainable development in future as well as waste management. In this study, small-scale solar air heating systems were produced from waste materials to analyze the usability of waste material in renewable energy systems. Scrap metal elbows were used in the production of heaters. The first solar heater is hollow (SH) and the second one was modified by filling it with aluminum wool (SHAW). Both heaters were tested simultaneously at different flow rates (0.014, 0.010 and 0.006 kg/s). According to the experimental results, the thermal efficiency values for SH and SHAW were found in the range of 33.63-42.90% and 42.69-56.98%, respectively. In addition, it was observed that a low cost modification such as using aluminum wool can significantly increase thermal performance of the solar heating system.