Temperature Thermal Energy Storage Research Articles

Sugar alcohol phase change materials for low-to-medium temperature thermal energy storage: A comprehensive review

The adoption of appropriate phase change materials (PCMs) is deemed to be the primary step during the course of application of latent heat storage technology. As a class of potential candidates, sugar alcohols are suitable for latent heat storage over medium temperature range (80–230 °C). The present work attempts to provide a comprehensive overview on the phase change behaviors, transport properties, thermal stability, charging/discharging performance and application status of sugar alcohols based on adequate amount of available investigations. Special attention is paid to their peculiar crystallization behaviors including supercooling, non-crystallization and cold-crystallization. In particular, the intrinsic mechanisms responsible for the above behaviors and properties are fully discussed, and some suitable techniques for alternating such behaviors/properties have been proposed accordingly. The specific advantages like high heat storage density and challenges such as poor thermal endurance are completely summarized for sugar alcohols. Furthermore, the potential application scenarios associated with long-term heat storage and controllable heat retrieval are put forward on the basis of the particular properties. Future studies with emphasis on the underlying fundamentals of crystallization and chemical reactions concerned with thermal stability are suggested. This review aims at building a benchmark database on the key information of sugar alcohol PCMs, thus to help deeply understand their properties. It can also provide useful guidelines to facilitate the large-scale utilization of sugar alcohols in solar thermal energy harvesting and industrial waste heat recovery.

Fabrication and investigation of paraffin based shape-stable composite phase change materials with styrene ethylene butylene styrene as supporting skeleton for low temperature thermal energy storage and management

Paraffin based composite phase change materials (PCMs) have gained intensive attentions in low temperature thermal energy storage (TES) and management application domains because of its suitable melting temperature range and advanced thermoproperties. Seeking decent structural supporting materials (SSM) and the associated manufacturing approaches that capable of fabricating paraffin composites at appropriate temperatures to avert the thermal decomposition of the paraffin particularly for low-molecule ones are in high demand. Herein, we developed a low-molecule paraffin (RT18HC) composite through a simple blending approach by using styrene-ethylene/butylene-styrene (SEBS) as SSM, and showed that such SEBS-paraffin composites could be able to fabricate at a low operation temperature of 80 °C, significantly lower than that required for the preparation of conventional high density polyethylene (HDPE)-paraffin composites. To enhance the composite effective thermal conductivity, a micro-sized graphite power as enhancer was also involved over the fabrication process. Owing to the desirable solubility of paraffin in SEBS, a crosslinking structure inlaying paraffin and graphite was formed, endowing the composite with ability to maintain the structure stabilization and eliminate the graphite sedimentation over the repeated thermal cycles. 10 wt% of SEBS gives the composite optimum formulation at which 10 wt% graphite can be involved, and also an excellent shape stability and thermal adjustment ability can be achieved.

Comprehensive thermal properties of ternary eutectic molten salt/nanoparticles composite phase change materials for high–temperature thermal energy storage

Chlorine and fluorine salts are very promising thermal storage media for high–temperature thermal energy storage (TES) systems. In this study, NaCl–KCl–NaF/nanoparticles composite phase change materials (CPCMs) were employed by an advanced high–temperature and high–pressure reactor. NaCl–KCl–NaF was adopted as the BS, while CuO and Al2O3 nanoparticles have been uniformly dispersed in different ratios to generate CPCMs from the base salt (BS). Microscopic characterization, thermal properties characterization, and economic analysis of CPCMs and the BS were performed. The findings revealed that the best results were obtained when the BS was added with 0.5 wt percent Al2O3 and 0.5 wt percent CuO nanoparticles, CPCMs have improved solid/liquid thermal conductivity by a factor of 3.70 and 1.84, and TES density by a factor of 1.13, while reducing the cost per unit of TES density by approximately 26.8%. In addition, the CPCMs and BS possess excellent operating temperature range and thermal stability, whereby they are applicable in high–temperature TES systems.

A novel one-step ultraviolet curing fabrication of myristic acid-resin shape-stabilized composite phase change material for low temperature thermal energy storage

In this work we present for the first time a simply, fast and efficient process for the fabrication of form-stable composite phase change material (PCM) by ultraviolet (UV)-curing technique. Simply by UV-curing of the PCM with a desired UV curable carrier for several minutes, a neoteric UV-cured composite that suitable for low temperature thermal energy storage (TES) can be fabricated. The feasibility of such a novel technique is demonstrated by investigating a case of myristic acid (MA) dispersed into a UV curable resin containing polyurethane acrylate (PUA). The results show that a crosslinked structure is formed in the composite after UV-curing due to the occurrence of photochemical reaction, which offer sufficient paths to accommodate the PCM, endowing the composite with the great ability to maintain the structure stabilization and prevent the liquid leakage. A good physical and chemical compatibility has been achieved in the composite and 40 wt% of UV-curing resin grants the composite optimum formula at which a melting temperature of 52 °C and an energy storage density over 210.8 kJ/kg at temperature ranged 25–100 °C are obtained. The results also reveal that the material mechanical strength can be linked to the UV-curing duration. For a given V-curing time of 5–30 mins, the composite mechanical strength is measured over 25–34 MPa, almost over twice as high as that of high-density polyethylene (HDPE) and styrene ethylene butylene styrene (SEBS) based composites. Owing to the high shape strength and excellent thermal cycling performance, such UV-curable composites can be utilized for modular design of TES devices, and also be used to precisely and directionally produce TES devices through additive manufacturing. This work exploits a new perspective for the energy-saving and time-effective fabrication of shape stabilized composite PCMs for low temperature thermal energy storage.

Effect of expanded graphite on the thermal conductivity of sodium sulfate decahydrate (Na2SO4·10H2O) phase change composites

Inorganic salt hydrate phase change materials (PCMs) are of interest for near-room temperature thermal energy storage (TES) systems, but their low thermal conductivity, ~ 0.5 W/m-K, limits their performance. In this work, we report the thermal conductivity and bulk density of composites containing sodium sulfate decahydrate (SSD) Na2SO4·10H2O with three types of graphite: expanded graphite (EG), milled EG (MG), and graphite nanoplatelets (GnP). The effect of these thermophysical properties on TES performance is presented. The composites were made using a readily scalable one-pot synthesis procedure with graphite received as-is. A 583% increase in thermal conductivity (4.1 W/m-K) was achieved with 25 wt% EG. However, as EG fraction increases, bulk density decreases and thermal conductivity plateaus. This ultimately resulted in lower thermal performance at higher EG fractions despite higher thermal conductivity. This highlights the tradeoff between PCM composite properties and performance, and why thermal conductivity is insufficient to describe PCM thermal performance. GnP is added to EG-SSD to increase bulk density and energy storage density, but these density improvements do not offset lower thermal conductivity and thus thermal performance declined. Similarly, MG-SSD composites had a higher bulk density and energy storage density, but lower thermal conductivity and thermal performance than EG-SSD composites at similar compositions. Atomistic molecular dynamics simulations were performed to understand the structure-property relationship of graphite-SSD interfaces. The simulations support the hypothesis that atomic level contact resistance between graphite and SSD increases thermal resistance at the interfaces resulting in effectively lower bulk thermal conductivity in MG-SSD compared to EG-SSD.

Synthesis and characterization of a novel high durability alloy microcapsule for thermal energy storage

Microcapsules can prevent leakage and increase the specific surface area of phase change materials (PCMs). Among them, metal microcapsule has great application prospects in the field of medium/high temperature thermal energy storage. However, it is easy to break after thermal cycling which seriously hinder its industrial application. To solve this problem, a novel alloy microcapsule with a void was prepared successfully with SnBi58 alloy as the core and TiO 2 as the shell by “double-layer coating, sacrificial inner layer” method, which can accommodate volume expansion during heat storage, thus fundamentally solving the problem of microcapsule break caused by thermal expansion. The test results indicated that the SnBi58 microcapsules melt at 141.1°Cand crystallize at 128.1 °C. It has latent heats of 46.61 J/g and 38.20 J/g for melting and crystallization, respectively. The thermal cycle test also showed that MEPCM with a void has better thermal reliability and durability than that of MEPCM without void. In addition, due to the wall material of TiO 2 , the microcapsules showed good photocatalytic performance. Furthermore, “double-layer coating, sacrificial inner layer” method can be widely used to prepare other metal microcapsule and it provides a new perspective for metal microencapsulation. • “Double-layer coating, sacrificial inner layer” method was presented to prepare alloy MEPCM. • A novel alloy MEPCM with expansion void was successfully prepared. • MWPCMs with different sizes of thermal expansion void were prepared and compared. • Durability of MEPCM was significantly improved due to the thermal expansion void.

Flexible Electricity Dispatch of an Integrated Solar Combined Cycle through Thermal Energy Storage and Hydrogen Production

In this work, the flexible operation of an Integrated Solar Combined Cycle (ISCC) power plant has been optimized considering two different energy storage approaches. The objective of this proposal is to meet variable users’ grid demand for an extended period at the lowest cost of electricity. Medium temperature thermal energy storage (TES) and hydrogen generation configurations have been analyzed from a techno-economic point of view. Results found from annual solar plant performance indicate that molten salts storage solution is preferable based on the lower levelized cost of electricity (0.122 USD/kWh compared to 0.158 USD/kWh from the hydrogen generation case) due to the lower conversion efficiencies of hydrogen plant components. However, the hydrogen plant configuration exceeded, in terms of plant availability and grid demand coverage, as fewer design constraints resulted in a total demand coverage of 2155 h per year. It was also found that grid demand curves from industrial countries limit the deployment of medium-temperature TES systems coupled to ISCC power plants, since their typical demand curves are characterized by lower power demand around solar noon when solar radiation is higher. In such scenarios, the Brayton turbine design is constrained by noon grid demand, which limits the solar field and receiver thermal power design.

Preparation and properties of novel ceramic composites based on microencapsulated phase change materials (MEPCMs) with high thermal stability

Ceramic composites are widely used in medium/high temperature thermal energy storage (TES) and catalysis. Due to the high latent heat of phase change materials (PCMs), it is an effective method to improve the TES capacity by combining PCMs with ceramic materials. However, PCMs are easy to leak after being heated, so they need to be microencapsulated. Furthermore, for porous ceramic catalytic composites, the leakage of PCMs will block the pores, which seriously hinders their application. In this paper, a novel microencapsulated phase change material (MEPCM) with thermal expansion void was prepared using “double-layer coating, sacrificing inner layer” method. Based on that, two kinds of ceramic composites have been prepared. One is a TES material which composed of alumina, glass frit (GF) and MEPCMs. Thermal analysis results showed that the composite can still maintain stable heat storage performance after 200 melting-solidification cycles with little latent heat loss. Another is a multifunctional porous composite phase change material (CPCM) by loading Ce and Mn as catalyst via solution combustion synthesis (SCS) method, which can be used in low temperature SCR catalysis and other catalytic fields (100–300 °C). Based on MEPCMs with thermal expansion void, the two ceramic composites show great potential in energy storage and catalysis.

A medium-temperature, metal-based, microencapsulated phase change material with a void for thermal expansion

Microencapsulated phase change materials (MEPCMs) have great application prospects in medium/high temperature thermal energy storage. However, it might rupture due to the thermal expansion of PCMs during the phase change process, which greatly reduces its service life and seriously restricts its development. Herein, an innovative technique to encapsulate PCMs was presented. A thermal expansion void was successfully constructed inside the MEPCMs by “double-layer coating, sacrificial inner layer” method to accommodate volume expansion of PCMs. Scanning electron microscope (SEM), differential scanning calorimeter (DSC), Powder X‐ray diffraction (XRD) and other characterizations revealed the microstructure and thermal performance of MEPCMs. The results showed that MEPCMs with thermal expansion void exhibit better thermal performance and longer thermal cycle life than that of MEPCMs without thermal expansion void. Based on this method, the rupture problem of MEPCMs caused by thermal expansion of PCMs during phase change process can be solved thoroughly. Furthermore, “double-layer coating, sacrificial inner layer” method is also suitable for microencapsulation of other metals and it provides a new perspective for medium or high temperature metal microencapsulation.

Screening of sugar alcohols and their binary eutectic mixtures as phase change materials for low-to-medium temperature thermal energy storage. (Ⅲ): Thermal endurance

The thermal endurance of four pure and three binary eutectic mixture sugar alcohols were examined as a complementary work to the previous screening efforts based on the phase change behaviors towards latent heat storage. It was shown that both the melting point and latent heat of fusion of these sugar alcohols degrade with increasing the heating duration, and that a higher degree of superheat leads to faster degradation. The melting point drift mainly attributes to the shrinking range of hydrogen bonding, whereas the decay of latent heat is likely resulted from the disruption of hydrogen bond networks and incomplete crystallization. Among the various candidates, erythritol exhibits the best thermal endurance. The infrared spectra demonstrated that sugar alcohols can be oxidized to generate aldehydes upon heating when exposed to air. It was also found that the duration for 10% degradation of the latent heat of fusion of inositol can be extended by ∼9 times when being protected by nitrogen gas. However, although the introduction of nitrogen gas could efficiently improve the thermal endurance, other complex reactions can still occur in inert gas atmosphere at high temperatures, leaving the room for further improving the thermal endurance of sugar alcohols toward real-world applications.

Multi-objective optimization and exergoeconomic analysis of a continuous solar-driven system with PCM for power, cooling and freshwater production

In this article, three different modes of a novel integrated system would be evaluated by the application of high temperature Thermal Energy Storage (TES) to produce electricity, cooling, and freshwater. Freshwater is produced using the reverse osmosis (RO) desalination unit while Absorption Refrigeration Cycle (ARC) provides cooling. In this system, a high temperature Phase Change Material (PCM) is utilized to make the system working continuously even at nights. The output heat of gas turbine (GT) is also recovered utilizing the Organic Rankine Cycle (ORC). According to exergoeconomic analysis, the efficiencies, exergy destructions and product cost rates are computed. The multi-objective optimization has also been performed considering six different ORC working fluids and the changes in the direct normal irradiation of a city in Iran. In the trigeneration condition, the optimum values of the GT’s compressor pressure ratio and ORC’s turbine inlet pressure were obtained 9.06 and 3300 kPa, respectively. The exergy efficiency of the suggested system at the optimal condition is computed to be 14.40%, while that of energy is 40.52% with the total product cost rate of 30.524 $/GJ. The produced cooling capacity of the absorption system is also 1.62 MW whereas the output amount of freshwater and electricity for the users are about 5209.5 m3/day and 2.42 MW, respectively. The Levelized Cost of Electricity (LCoE) is also calculated to be 0.2341 $/kWh, which shows promising economic performance.

MATHEMATICAL MODELLING OF LOW GRADE THERMAL ENERGY STORAGE USING AN ENCAPSULATED LIQUID MEDIUM

In the present study, we report the results obtained from numerical simulations of low grade heat storage. Four different fluid encapsulated materials were tested in four design types for their suitability as a small scale, low temperature thermal energy storage (TES). This was done by analysing and evaluating the maximum temperature reached per sphere for three different positions inside the tank, which correspond to the top right, centre and bottom right sphere. The influences of the material properties and the inlet/outlet tank designs were analysed and evaluated based on the results. The heat transfer fluid (HTF) was water and the storage materials selected were water, glycerol, MDM and MD3M. These were heated sensibly from an ambient temperature of 20°C to 90°C. The analysis shows that the materials with the highest relevant properties do not in fact charge the tank the fastest. Furthermore, the design of the inlet greatly affects the heating dynamics of the system, whereas changing the outlet design marginally affects the results.

Surfactant-free microencapsulation of sodium nitrate for high temperature thermal energy storage

Molten salt is typically used as a storage medium in high temperature thermal energy storage (TES) applications. However, salt leakage and the consequent corrosion increase the cost of TES, and hinder the expansion of its application. Therefore, to address these issues, this study proposes a surfactant-free microencapsulation method in which sodium nitrate is enclosed in protective silica (SiO2). The encapsulation ratio of the sodium nitrate core was experimentally measured by comparing the melting peaks of the pure core material and the encapsulated core using differential scanning calorimetry. A high encapsulation ratio (89% on average) was obtained from the sodium nitrate microcapsules synthesized in this study. Additionally, the morphological characteristics of the microcapsules were examined by scanning electron microscopy analysis. Furthermore, Fourier transform infrared spectroscopic analysis confirmed the formation of robust microcapsules without the use of surfactants.

System performance analyses of sulfur-based thermal energy storage

Elemental sulfur is a promising storage material for low to high temperature thermal energy storage (TES) applications due to its high chemical stability, high heat transfer rate, and low cost. In this study, we investigate the performance of sulfur-based TES systems (SulfurTES) in a single-tank thermal battery configuration. In general, the results show that a moderate shell aspect ratio and standard tube diameters can be used to provide a range of high performance. An experimentally validated 2D numerical model is used here. The model predicts system-level performance based on the energetic and exergetic efficiencies for a range of geometric parameters and operating mass flow rates. This analysis shows the competing effects of the design and operating conditions on the performance parameters, and reveals governing parameter spaces unique to the specified performance targets. We have proposed a strategy to identify this parameter space, for which, the SulfurTES system will achieve required thermal performance, and a design procedure to incorporate such parameter space in system design. This work provides a systematic approach in TES performance investigation, and establishes an important framework to design industrial-scale SulfurTES systems that will offer high thermal performance using low-cost materials.

Screening of sugar alcohols and their binary eutectic mixtures as phase change materials for low-to-medium temperature thermal energy storage. (Ⅱ): Isothermal melting and crystallization behaviors

Based on the non-isothermal phase change behaviors of twenty-one pure and mixture sugar alcohols presented in our previous study (Part Ⅰ), the isothermal melting and crystallization behaviors were further tested in this supplemental work for five selected pure sugar alcohols (xylitol, erythritol, d-mannitol, d-dulcitol and inositol) and their five binary eutectic mixtures to make an advanced screening of these candidates for low-to-medium temperature latent heat storage. The isothermal melting and crystallization behaviors of these ten candidates were tested at a constant degree of superheat (10 °C) and various degrees of subcooling up to 210 °C. The phase change temperatures, degrees of supercooling and durations of phase change were determined by the recorded temperature-history curves. It was found that the incrystallizable xylitol and its eutectic mixture of xylitol (75 mol%) + erythritol with low melting points under 100 °C are also unable to crystallize during isothermal cool-down at any degrees of subcooling (30–90 °C) due to the unavailability to nucleation. The rest eight crystallizable candidates all suffer from severe supercooling and are unable to crystallize at low degrees of subcooling (<20 °C). They undergo both one-phase supercooling due to poor nucleation performance and two-phase supercooling, which was unable to be obtained previously by non-isothermal cooling, due to slow crystallization kinetics. However, it seems difficult to find a correlation between the observed degrees of supercooling in both the liquid and solid phases and the prescribed degrees of subcooling by only three consecutive isothermal melting and crystallization cycles, as a result of the randomness of nucleation and large size of samples. The duration of crystallization was shown to decrease with increasing the degree of subcooling for both pure and mixture sugar alcohols due to the enhanced driving force for crystallization. The durations of crystallization of the mixture sugar alcohols appear to be longer than those of their pure compounds, due to the lower thermal conductivity and higher dynamic viscosity of the mixtures. Combining the present isothermal and the previous non-isothermal test results, it has been confirmed that the difficulty in crystallization and the severe supercooling are the primary issues for sugar alcohols, which must be addressed before they can be used in real-world latent heat storage systems.

Flexible electricity dispatch for CSP plant using un-fired closed air Brayton cycle with particles based thermal energy storage system

This paper presents a novel power block concept for flexible electricity dispatch in a Concentrating Solar Power (CSP) plant. The power block is based on intercooled – unfired regenerative closed air Brayton cycle that is connected to a pressurized solar air receiver. The Closed Brayton cycle uses a mass flow regulation system centered on the pressure regulation (auxiliary compressor and bleed valve) in order to control the Turbine Inlet Temperature (TIT). Doing so, the system is able to modulate turbine electricity production according to variations in the solar resource and changes in power electric demand. It has been found that the proposed power block is able to fully cover the electricity demand curve for those days with high solar resource. In case of integrating particles-based high temperature Thermal Energy Storage (TES) system, the power block can extend its production till the next day following the electricity curve demand during summer period. During winter period, the power plant can extend its production for a few hours due to the lower solar resource and the higher electric curve demand load.

Numerical characterization of thermocline behaviour of combined sensible-latent heat storage tank using brick manganese rod structure impregnated with PCM capsules

Efficient medium temperature thermal energy storage (TES) can help to eliminate the imbalance between energy demand and supply. In this study the issue of thermal ratcheting in TES system is avoided by using structured sensible heat storage material. Another technical issue of temperature drops at the end of discharging cycles occurring in only sensible material filled TES is overcome to some extent by using phase change material (PCM) between sensible rod structure (SRS) providing stable fluid outlet temperature. A comprehensive transient numerical model is formulated by solving separate equations for heat transfer fluid and storage materials using energy balance method coupled with enthalpy technique to study the influence of phase change temperature in the PCM. The numerical model predicts thermal stratification behaviour and thermocline formation along the symmetry-axis. A detailed parametric analysis of the combined sensible-latent heat thermal energy storage is performed to investigate the effect of porosity variation, inlet velocity and feature size of sensible heat storage material on total energy utilization, effective discharging efficiency and effective discharging time using thermocline characterization. The results indicate that discharging efficiency of hybrid TES tank can be increased by using lower velocity of fluid at inlet, by decreasing porosity or by using reduced SRS feature size. The study offers suggestions for optimized design and governing parameters of a new type of combined sensible-latent heat TES configuration, while avoiding thermal ratcheting with stable fluid outlet temperature for an application specific process.

Assessment for the adaptation of industrial combined heat and power for chemical parks towards renewable energy integration using high-temperature TES

A fundamental challenge of the German energy transition is the energy supply of industrial and chemical parks based on renewable energy. Presently, the energy demand of a chemical park with one third electricity and two thirds heat as a rough estimate is commonly supplied by a heat-controlled fossil fired combined heat and power (CHP) plant. If applicable, the surplus electricity generated by such plants is sold and fed into the grid. Since the reliable energy supply of all users and facilities is priority, energy storage can be incorporated, if fluctuating renewable energy sources shall be used. This paper presents energy supply concepts without adjustments to the industrial park infrastructure or the processes themselves and proposes utilization of high temperature thermal energy storage (TES) technologies such as molten-salt, as well as power-to-heat (PtH) technology in the central CHP supply infrastructure.The objective of this study is to identify the major possibilities for integrating TES in a future energy supply system for an industrial park in Germany. It shall be shown how the flexibility of an utility supplier can be increased, so that further revenue can be generated from participating in the energy market. For this task different concepts will be proposed and applicable TES technologies will be identified. The benefits for the utility supplier and how carbon dioxide reduction and integration of renewable energies can be achieved will be highlighted.Finally, an overview of concepts with additional TES and PtH components for the energy supply of industrial or chemical parks in Germany is presented qualitatively. This overview includes the following criteria: flexibility, carbon dioxide reduction and the increased use of CHP. Overall a better understanding of potential flexibility measures for the utility supply infrastructure in the chemical industry is generated.

Thermodynamic assessment of the SrBr2-MBr (M: alkali metal) binary systems

The phase diagrams of the SrBr2-MBr (M: alkali metal) binary systems based on phase equilibria and thermochemical data were evaluated and optimized using the CALPHAD method. The substitutional solution model was used to describe the Gibbs energies of all liquid phases. All intermediate compounds were handled to be stoichiometric of which the Gibbs energies comply with the Neumann-Kopp rule. Self-consistent datasets with all model parameters were developed, and thermodynamic properties of liquid phase (mixing enthalpy and activity) were also calculated for the whole range of compositions. Meanwhile, the empirical method based on ionic parameter function was successfully used to validate the mixing enthalpies calculated. Results manifest that the calculated results were in excellent agreement with the experimental values reported in the present work. By means of thermodynamic calculation, this database of strontium bromide system was used to predict the SrBr2-based multicomponent system with low melting points, which will design and prepare composite materials for low temperature thermal energy storage (TES).

Preparation and investigation of multicomponent alkali nitrate/nitrite salts for low temperature thermal energy storage

A novel eutectic salt of alkali nitrate/nitrite mixture with low melting point was investigated using thermal analysis methods for thermal energy storage. The eutectic salt mixture system LiNO3-NaNO3-KNO3-NaNO2-KNO2 was prepared based on eutectic composition XLiNO3 = 33.5, XNaNO3 = 1.2, XKNO3 = 1.2, XNaNO2 = 17.4 and XKNO2 = 46.7 (in mole fraction). Using Differential Scanning Calormetry (DSC) apparatus, the melting point, enthalpy of fusion and specific heat capacity of the eutectic salt mixture were experimentally determined under an argon atmosphere. The density of eutectic salt mixture based on Archimedean principle was measured as a function of temperature. By means of the Thermogravimetric Analyzer (TGA) equipment, the decomposition temperature and the upper limit of operating temperature of eutectic salt mixture were determined. Viscosity of eutectic salt was also measured experimentally using a rotational coaxial cylinder viscometer constructed. Meanwhile, the empirical estimation method based on additive principle was used to predict thermal-physical properties (density and viscosity) of eutectic salt mixture. Results indicate that the predicted values were in good agreement with experiment values. Based on the thermal-physical properties of eutectic salt mixture, this novel five-component eutectic system can be used as excellent heat transfer and storage materials for low temperature thermal energy storage (TES) applications.