الملخص
Abstract The thermal energy is considered as one of the most important sources for the renew sources for the renewal energy because this energy is a low cost and safe in application and not toxic. So, we can consider this renewable energy is a very important to application in many fields. It is a significant technology in the thermal storage materials involving renewable energy as well as other energy resources as it can make their operation more efficient, particularly by bridging the period between periods when energy is harvested and periods when it is needed. Therefore the thermal energy storage is helpful for balancing between supply and demand of energy. The phase change materials (PCMs) play an important role to increase the contribution of various types of renewable energy in the thermal storage materials. The charging and discharging process for the thermal storage materials is a very importantprocess in many engineering applications. It is achieved with greatly differing technologies that collectively accommodates a wide range of needs. The PMCs, such as sensible heat (solid-solid) phase latent heat (solid-liquid) or (liquid-solid) phase and thermo-chemical storage can be applied in these applications. The sensible heat mainly depends on the temperature of the system to change the specific heat and the other thermal parameters in the (solid-solid) phase change. The latent heat depends on the phase transformation of the thermal storage materials a.e. (solid-liquid) or (liquid-solid) phases. The sensible heat and latent heat for the thermal storage materials represent the principles factors for the charging and discharging process. So that, it is necessary to study the effect of the additive nano materials to the thermal storage media on the thermophysical parameters, which lead to more increase in the efficient operation for the charging and discharging process. Hence we can obtain the optimum thermal energy during this process. Here we study many different systems based on a storage media (Na0.6k0.4)NO3 as a principle matrix and noted as M0. Four systems have been produced by adding different contraction of nano-silica and nano-carbon. The first one is M01, which was produced by adding nano-silica of (x=1, 2, 3, 4 %.wt) by weight to M0. The systems M02 and M03 were produced by adding x=2% and x=4% wt of nano-carbon by weight to M01 respectively. Finally the M04 system is produced by adding different concentration of nano-carbon (x= 2, 4, 6% wt) to M0 mixed with nano-silica of x=2% wt. The thermo-physical properties of the different systems M0, M01, M02, M03 and M04 under investigation are deeply studied here in the case (solid-solid) phase P1, (solid-liquid) phase P2 and (liquid-solid) phase P3 by various experimental techniques to clarify the effect of the nano-silica andnano-carbon on the efficient of the thermal storage during the charging and discharging process. The different analyses used in the experimental investigations are the thermal analysis (DSC), electrical conductivity, thermal properties, microstructure by using x –ray and SEM & EDAX analysis. These analyses clarify the effect of the additives materials on the dynamics structure for the M0 system with the different concentration of the nano-silica and nano-carbon. From the DSC analysis, it is clear that the thermal parameters; variation energy, transient time, transient temperature, specific heat CP, Enthalpy (∆H) and the amount of heat ∆Q, for the M0 systems are mainly depending on the different contcentration of the nanosilica (x=1, 2, 3, 4 % wt). From this thermal analysis, it is clear that the optimum concentration for the nano-silica is observed at x=2% which represents the optimum distribution of the nano-silica inside the M0 system. This leads to improve the porous system due to the degree of homogeneity caused by the thermophoresis effect distribution, the high surface area of the nano-silica with the activity of the M0 matrix alongside the degree of the alkalinity of the nano-silica. The other experiment analysis on the M01 system like electrical, thermal properties and the microstructure revealed and supports the optimization condition for the nano-silica (x=2 %wt) added to the M0 system. The analysis also clarifies the role controlling the effect of nano-carbon on the thermo-physical properties for the M01. It is clear from the all analysis for the different experiments listed before on the M02 system (M01+2% wt nano-carbon) lead to the same result obtained for the M01. The most important sample in this matrix M02 system can be considered at x=2% nano-silica +2%wt nano-carbon. Also, all the above experiments are used for the M03 system (M01 +4%wt of nano carbon). Finally, the previously mentioned different experiments were also used to study the thermo-physical properties of the M04 system (M0 +2% nanosilica and different concentration from nano-carbon x=2, 4 and 6%wt).From the all analysis results, it is clear that the nano-silica the effect on the M0 system (thermal storage material) is clearly appeared at x=2%wt of nano-silica. This effect is quite clear in all thermo-physical parameters (ΔQ, ΔH, etc.). This ratio is considered as an optimum condition for the concentration of nano -silica inside the matrix M0. This optimum ratio is also confirmed from all the other analysis (DSC, σ, k, X-Ray, SEM and EDAX). This means that this percentage of nano-silica modified the pore ratio of system for the M0 Matrix, and the distribution of the nano-silica inside the M0 System, mainly depending on the thermophoresis effect, beside that the high thermal and chemical stability of the nano-silica, which having a high surface area with a high potential activity of the disphasic phase (NaK) in the matrix M0. From the analysis experiments for M01, M02, M03 and M04, which are concerned with the increase of the effect of the nano carbon inside the matrix M01, it is clear the increasing of the concentration of the nano-carbon, leading to variation in all the thermophysical properties for these systems, this variation mainly depending on the concentration percentage inside the matrix M01. The optimization condition for the concentration of the nano-carbon is clearly observed at x=2%wt, this concentration is more effected than the other concentration, especially in the thermo-physics ΔQ and ΔH that means that there is enhancement for the heat transfer for this matrix M01, at x=2%wt nanosilica and x=2%wt from the nano-carbon, that is mainly related to the physical and chemical stability for the nano-carbon, and the activity of the disphasic phase (NaK) inside the M0 system. So that we consider from the all analysis for all different M01, M02, M03 and M04 systems, that the optimization condition for the critical concentration for the nano-silica and nano-carbon, can be represented at x=2%wt by weight for each nanomaterials. The enhancement for the thermo-physical for the M0 system with the additive 2%wt from nano-silica and 2% wt from nano-carbon leading toenhancement the pore ratio, due to the high homogenty distribution of the nano- partials, the interstitial distribution of the nano-carbon and the high activity of the nano-carbon for thermal and electrical conduction. The enhancement of the thermo-physical properties is very important to increase the efficiency of the charging and discharging process during the phase chang
