Solar air heaters (SAHs) are renewable energy systems that utilise solar radiation to heat air, offering sustainable solutions for space heating, agricultural drying, and industrial processes. These systems are simple in design, cost-effective, and environmentally friendly, making them essential to the renewable energy landscape. However, challenges such as low thermal efficiency, dependency on climatic conditions, and significant thermal losses limit their adoption. Recent advancements in design, materials, and operational strategies have significantly improved their performance. This review explores the principles of SAHs, innovations in design, thermal storage integration, and efficiency enhancement techniques. Applications in various sectors are discussed, highlighting ongoing research to maximise efficiency while maintaining economic viability and ecological benefits.

This research is carried out to investigate and examine the critical benefits and significant contributions of integrating nanoparticles into the ETSC system to enhance the thermal efficiency, thermal performance, temperature out, and energy storage of the ETSC. The Simcenter STAR-CCM+ 2022.1 software package implemented numerical analysis and thermal simulations. Further, a comparative analysis is conducted on two case studies to validate the critical role and contributions of employing the aluminum oxide nanomaterial in the solar collector system to enhance its thermal efficiency and improve its thermal performance and heat transfer, including (1) conventional ETSC and (2) ETSC with Al2O3. According to the numerical analysis and comparative study findings, the results of this research revealed that employing and adding the aluminum oxide nanomaterial into the ETSC system had contributed to several beneficial impacts and significant advantages. In addition, using Al2O3 achieved enhancements in the thermal efficiency, increases in the outlet collector’s temperature, improvements in the rate of heat flux of the pipes, the tube inside the collector, heat transfer of the hot water storage tank, and a rise in the temperature gradient the hot water temperature increased from (between 44.3 and 74.8 ºC) to (between 49.6-80.3 ºC). Besides, the velocity of the water flow inside the solar collector in the second case in which the aluminum oxide nanoparticles are used was higher due to the absorption of further solar radiation and thermal energy, which resulted in a considerable increase in the kinetic energy of water molecules from 0.01 to 0.07 m/s. Also, it was found that the velocity directions and profile were slightly more turbulent in the second case than the conventional solar collector due to more thermal energy absorbed and stored in the ETSC from solar radiation.

Cooling towers are indispensable in dissipating heat from industrial processes and HVAC systems, hence playing a significant role in operational efficiency and sustainability. This review describes the classification of cooling towers based on airflow mechanisms, methods of heat transfer, and applications. This study highlights recent developments in hybrid cooling systems that combine wet and dry cooling technologies for improved water conservation and thermal efficiency. Through the analysis of recent developments in the domain, this work describes innovative design considerations that optimize thermal performances by including environmental concerns; designs that are in the counterflow and crossflow configuration. These insights underline continuous improvements within cooling tower technologies in light of evolving industrial and ecological demands.

This research aims to improve thermal performance and compare the performance of two common crystalline PV panel types (Mono and poly). Modules with a back-cooling system were designed and numerically analyzed with SolidWorks and ANSYS-Fluent-2021-R2 for the simulation under Baghdad weather at noon. The cooling system used consists of a phase-change material, paraffin wax (RT55), with a thickness of 5 cm and a heatsink with 33 fins with heights of 10, 20, and 30 mm and thicknesses of 2, 4, and 6 mm. to select the best height of the wax 1, 3, 5, 10, 20 cm examined. The result showed that for polycrystals, the panel temperature was reduced by 8.4°C using PCM and 11.9°C using PCM-fins. Also, output power was enhanced to 200.6 W by 10.2 W, and efficiency improved by 5%. Similarly, using PCM and PCM-fins lowered the temperature of the monocrystalline by 8.3 and 12.5°C, respectively. Therefore, the output power is enhanced to 202.4 W by 10.7 W and improves the electrical efficiency by 5.2%. The results of the study showed that mono had better performance than poly. This result is acceptable and is in good agreement with previous studies.