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Metal hydride (MH) hydrogen storage needs an external heat source to release the stored hydrogen. To enhance the thermal performance of MHs, the incorporation of phase change materials (PCM) is a way to preserve reaction heat. This work proposes a new MH-PCM compact disk configuration (i.e., a truncated conical MH bed surrounded by a PCM ring). An optimization method is developed to find the optimal geometrical parameters of the MH truncated cone, which is then compared to a basic configuration (i.e., a cylindrical MH surrounded by a PCM ring). Moreover, a mathematical model is developed and used to optimize the heat transfer in a stack of MH-PCM disks. The optimum geometric parameters found (bottom radius of 0.2, top radius of 0.75 and tilt angle of 58.24) allow the truncated conical MH bed to reach a faster heat transfer rate and a large surface area of higher heat exchange. Compared to a cylindrical configuration, the optimized truncated cone shape enhances the heat transfer rate and the reaction rate in the MH bed by 37.68%. [ABSTRACT FROM AUTHOR]

Integrating a solar water heater (SWH) with a phase change material (PCM)-based latent heat storage is an attractive method for transferring load from peak to off-peak hours. This transferring load varies as the physical parameters of the PCM change. Thus, the aim of this study is to perform a parametric analysis of the SWH on the basis of the PCM's thermophysical properties. A mathematical model was established, and a computation code was developed to describe the physical phenomenon of heat storage/release in/from the SWH system. The thermal energy stored and the energy efficiency are used as key performance indicators of the new SWH–PCM system. The obtained numerical results demonstrate that the used key performance indicators were significantly impacted by the PCM thermo-physical properties (melting temperature, density, and latent heat). Using this model, various numerical simulations are performed, and the results indicate that, SWH with PCM, 20.2% of thermal energy on-peak periods load is shifted to the off-peak period. In addition, by increasing the PCM's density and enthalpy, higher load shifting is observed. In addition, the PCM, which has a lower melting point, can help the SWH retain water temperature for a longer period of time. There are optimal PCM thermo-physical properties that give the best specific energy recovery and thermal efficiency of the SWH–PCM system. For the proposed SWH–PCM system, the optimal PCM thermo-physical properties, i.e., the melting temperature is 313 K, the density is 3200 kg/m3, and the latent heat is 520 kg/kg. [ABSTRACT FROM AUTHOR]

Thermophysical properties such as latent heat, viscosity and melting temperature could be changed for different physical properties of dispersed nanoparticle such as size, shape, and concentration. In this study, Nanocomposites-Enhanced Phase Change Materials NePCM are formed by dispersing Aluminium (Al) and Copper (Cu) nanoparticles into paraffin wax in various mass fractions (0.1, 0.3, 0.6, 1, 2.5 and 5%). The impact on the thermophysical properties of paraffin wax by the nanoparticles is also investigated. Heat conduction and differential scanning calorimeter experiments are used to investigate the effects of different nanoparticle concentrations on the melting point, solidification point, and latent capacity of nanocomposites. Experimental results show that the dispersion of nanoparticles of Al and Cu can decrease the melting temperature and increase the solidification temperature of PCM. this dispersion could also be limited due to increase in dynamic viscosity of the NePCM. Furthermore, Al and Cu nanocomposites with mass fractions of 2% and 1%, respectively, show better enhancements in the thermal storage characteristics of the paraffin compared to the next higher mass fraction. [ABSTRACT FROM AUTHOR]

Among various applications of solar energy, solar air heater is a common method to fulfill the demand of hot air for space heating. In this experimental work, a low-cost solution is discussed for solar air heating. This solution deals with integration of modified models of air heaters with graphite powder, brick powder, and desert sand. These sensible heat storage materials have been filled inside a small cylindrical-shaped container to be placed over the absorber of modified heaters for performance enhancement. Total three different configurations have been developed for comparative analysis such as, configuration 1 for graphite powder testing, configuration 2 for brick powder testing, and configuration 3 for desert sand testing. Results are compared to the same design conventional heater to find out the best configuration, which shows that the configuration 1 is the best among all tested configurations. Under the configuration 1, enhanced heat transfer is observed about 541.2 W/m2K, thermal efficiency about 37.62%, overall heat loss about 6.71 W/m2K, and maximum exhaust air temperature about 41.2°C. For a better comparative analysis, configuration 1 is further compared to some other designs of solar heaters purposely for the plate temperature and thermal efficiency. Total cost of the best configuration (model) is about $59.5. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sensible and Latent energy storage capabilities of Ionic liquids are assessed. • Nanoparticles dispersed Ionic Liquids significantly improves absorption capabilities and molar extinction coefficient. • Effects of variation in cation chain length and anion on thermophysical and optical properties are discussed. • Future challenges on the formulation of Ionanofluid are discussed. Ionic liquids are liquid salts that are composed entirely of ions having melting points lower than 100 °C. Ionic Liquid possesses some salient properties like low melting point, negligible vapor pressure, and elevated thermal stability, making them a potential candidate as a working fluid for solar energy systems. Ionanofluid is formulated by incorporating nanomaterials in Ionic Liquid, which tunes the Ionic Liquid's thermophysical, optical, and energy storage properties and allows them more reliable as a medium for energy storage and heat transfer fluids for solar systems. This current review deals with the applicability of Ionic liquids, Ionanofluids in solar systems together with the role of some advanced nanomaterials to meet the permissible properties. Energy storage capability (sensible and latent), optical properties (absorbance, transmittance, molar extinction coefficient), together with thermal stability, thermal conductivity, and viscosity are assessed. The effects of anion/cation variations on these properties are discussed. The applications of Ionic Liquids and Ionanofluids in different solar systems have been critically reviewed together with recent advances of nanoparticles in the solar energy system. Outstanding sensible energy storage properties of Ionanofluids together with improved thermophysical properties are the significant findings of this present review. Finally, the existing challenges that require to be overcome for the successful implementation in the real case are also brought to light. [ABSTRACT FROM AUTHOR]