Potential Thermal Energy Storage Materials Research Articles

Stability assessment of alumina and SiC based refractories in a high temperature steam environment as potential thermal energy storage materials

Solar energy can be utilized not only for electricity generation but also for synthetic fuel production, making it a versatile option in the transition to a low-carbon and sustainable energy system. However, to enable economically viable solar fuel production, the development of efficient thermal energy storage (TES) materials is crucial. Ceramic materials have been identified as a potential solution for high-temperature TES applications. In this study, two commercially available refractories, alumina coated recrystallized silicon carbide and alumina-based refractory were investigated for their stability under long-term steam corrosion tests to evaluate their suitability as TES materials for a potential TES unit. X-ray diffraction (XRD) revealed that recrystallized silicon carbide is composed of two different SiC polytypes (moissanite 6H and moissanite 4H) while alumina-based refractory contained corundum and mullite. Upon being exposed to steam, both materials exhibited distinct characteristics. SiC experienced significant mass gain, a subtle lightning of its surface color and erosion of a porous alumina coating on the SiC. Amorphous silica phases were detected as an indication of oxidation of SiC from X-ray diffractrograms. These remarkable changes clearly indicate that SiC is unsuitable for use in a potential thermal energy storage (TES) unit. On the other hand, there was no significant visual changes in the alumina-based refractory and the weight change was only marginal after corrosion tests. However, XRD indicated mullite completely disappeared after steam corrosion tests possibly due to its decomposition into Al2O3 and Si(OH)4.

Preparation of novel hollow metal organic framework for enhancing flame retardancy of paraffin/EP thermal energy storage materials

AbstractParaffin is a potential thermal energy storage material, but leakage and flammability are the two major problems affecting its storage and safe use. Here, a novel flame retarded paraffin/epoxy resin composite was developed by using paraffin, epoxy resin and hollow metal organic framework (W‐UiO66‐PPA) as thermal energy storage material, supporting material and flame retardant, respectively. The thermal energy storage and flame retardancy performances were examined with differential scanning calorimetry, vertical burning, limiting oxygen index and cone calorimeter tests. The results show that the paraffin/epoxy resin retains intact without leakage when the content of paraffin reaches 40 wt%, and this material exhibits high melting latent heat and remarkable thermal recycling property. In addition, the flame retarded paraffin/epoxy resin shows excellent flame retardancy, which is attributed to the following three aspects: (1) the hollow structure with open vertices of W‐UiO66 is capable of absorbing and collecting the combustible gasses produced by the combustion of epoxy resin; (2) the Zr and W elements of W‐UiO66 can facilitate catalytic charring and form a dense char layer; (3) phosphorous‐containing free radicals are able to capture OH· and O· free radicals during the combustion of paraffin and epoxy resin, thus interrupting the combustion chain reaction. On the whole, the flame retarded paraffin/EP possesses excellent thermal energy storage, thermal recycling, and flame retardancy properties. Our work provides a fantastic inspiration for the rational design of other flame retarded form‐stable phase change materials.

Synthesis and Characterization of Dicarboxylic Acid Esters of 1‐Hexadecanol for a Thermal Energy Storage Application Range of 50–55 °C

Dicarboxylic acid esters for thermal energy storage (TES) have attracted increasing attention in recent years because of their easy production, offering different temperatures, and providing solutions to the handicaps of fatty alcohols, which are potential TES materials. Dicarboxylic acid esters of 1‐hexadecanol are synthesized herein from adipic, succinic, and oxalic acid for the first time as TES materials. The dicarboxylic acid esters are characterized by Fourier transform infrared and proton nuclear magnetic resonance spectroscopy. Furthermore, the thermophysical properties of the dicarboxylic acid esters are examined by differential scanning calorimetry and thermogravimetric analysis methods. Additionally, the surface morphology features of the dicarboxylic acid esters are determined by polarized optical microscopy. The synthesized dicarboxylic acid esters of 1‐hexadecanol exhibit curiously specific behaviors that they melt at 49.2, 54.1, 54.8, and 53.5 °C, respectively, and crystallize at 47.7, 50.4, 53.1, and 50.2 °C, respectively. The applicability analyses of the dicarboxylic acid esters are carried out with integral graphs showing the sum of sensible and latent heat in a certain temperature range, time‐dependent heating and cooling graphs in a constant increasing temperature environment, and structural and thermal stability analyses after 1000 times heating–cooling thermal cycle.

Thermophysical investigation of metallic nanocomposite phase change materials for indoor thermal management

This experimental work discusses the thermophysical investigation of metallic nanocomposite PCMs having a potential application in indoor thermal management. Organic fatty alcohol (lauryl alcohol) was used as a phase change material (PCM). Four metallic nanoparticles, namely Al2O3, CuO, Fe3O4, and SiC at the concentrations of 1 wt%, 3 wt%, 5 wt%, were used to prepare nanocomposite PCMs, and their phase change properties were investigated. The results showed a minor change in the phase change temperatures, and the latent heat values varied between 6.56% and 18.5%. Besides, the degree of supercooling was reduced for nanocomposite PCMs. Fourier transform infrared spectroscopy, and thermogravimetric analysis showed no chemical reaction between the nanoparticles and the base PCM. The nanocomposite PCMs decomposed above 110°C, higher than the proposed application temperature range. In addition, the maximum enhancement in thermal conductivity of PCM at 10°C with 5 wt% of Al2O3, CuO, Fe3O4, and SiC nanoparticles were about 29.1%, 52.2%, 9.2%, and 17.9%, respectively. The endothermic freezing process was carried out, and lower phase change duration was recorded for nanocomposite PCMs compared to pure PCM. Based on various experimental studies, Al2O3 and CuO nanocomposite PCMs exhibits significantly improved thermal and physical properties than the Fe3O4 and SiC nanocomposite PCMs and can be used as a potential thermal energy storage material for indoor thermal comfort applications.

Development of phase change materials using hydrolyzed Al-Bi composite powder for solar energy storage

The hydrogen generation technology using the hydrolysis of Al-based composite powders has recently gained an increasing attention. However, the emission of hydrogen generation waste residue stream is an urgent problem to be addressed in the actual manufacture. For this purpose, this study reported the development of phase change thermal energy storage materials using hydrogen generation waste residue stream from Al-based composite powder hydrolysis. Specifically, the rapid hydrolysis reaction of Al-Bi composite powders was used to generate hydrogen, and subsequently tetraethoxysilane of different masses was added to the hydrogen generation waste residue stream to prepare Al-Si/Al2O3 composite phase change materials (PCMs) with controllable melting temperature. The results indicated that the hydrogen generation yield of Al-Bi composite powders during the fabrication of composite PCMs was 537.3–565.7 mL/g. Importantly, the prepared composite PCMs, with a controllable melting temperature of 573.2–654.2 °C, thermal energy storage density of 30.9–37.3 J/g, great repeatable utilization performance and structural stability, were potential thermal energy storage materials for concentrated solar power plants. Thus, this study not only achieved the reuse of hydrogen generation waste residue stream but also offered a new method for preparing Al-based composite PCMs.

Thermal properties of thermochemical heat storage materials.

The thermal conductivity, thermal diffusivity and heat capacity of materials are all vital properties in the determination of the efficiency of a thermal system. However, the thermal transport properties of heat storage materials are not consistent across previous studies, and are strongly dependent on the sample composition and measurement method. A comprehensive analysis of thermal transport properties using a consistent preparation and measurement method is lacking. This study aims to provide the foundation for a detailed insight into thermochemical heat storage material properties with consistent measurement methods. The thermal transport properties of pelletised metal hydrides, carbonates and oxides were measured using the transient plane source method to provide the thermal conductivity, thermal diffusivity and heat capacity. This information is valuable in the development of energy storage and chemical processing systems that are highly dependent on the thermal conductivity of materials.

Novel core/void/shell composite phase change materials for high temperature thermal energy storage

• A novel core (=Al-Si/Bi)/void/shell (=Al 2 O 3 ) composite PCM was successfully prepared. • The Al-Si alloy and Al 2 O 3 shell were in-situ prepared by the displacement reaction. • The void layer was formed by the evaporation of most of the outer Bi in Al/Bi alloy. • The thermal stability of Al-Si/Bi/Al 2 O 3 was obviously improved due to the void layer. • The Al-Si/Bi/Al 2 O 3 possessed an adjustable thermal energy storage performance. Metallic solid-liquid phase change materials (SLPCMs) are crucial for the thermal energy storage technology of various industrial systems. However, the encapsulation of metallic SLPCMs is still technically difficult. In this pursuit, the present research envisaged the development of a novel technology to successfully prepare the core(=Al-Si/Bi)/void/shell(=Al 2 O 3 ) composite SLPCMs by using Al/Bi immiscible alloy powders as starting material and tetraethoxysilane as SiO 2 source. The Al-Si alloy and Al 2 O 3 shell were in-situ synthesized by the displacement reaction between SiO 2 and molten Al. Interestingly, most of the Bi distributed in the shell of Al/Bi immiscible alloy powders could not only improve the activity of alloy powders and promote the formation of precursor shell, but also be recycled by evaporation to form the void layer during the calcination process of composite SLPCMs. The produced void layer provided a space buffer to alleviate the volume expansion of the core SLPCM, and thereby improving the thermal cycling stability of the prepared composite SLPCMs. The thermal cycling test results showed that after 300 thermal cycles, the melting latent heat reduction of the core(=Al-Si/Bi)/void/shell(=Al 2 O 3 ) composite SLPCMs (24.3–31.7 J/g) was much less than that of the core(=Al-Si)/shell(=Al 2 O 3 ) composite SLPCM (58.1 J/g). Moreover, the prepared Al-Si/Bi/Al 2 O 3 exhibited an adjustable melting temperature (571.9 °C to 631.9 °C) and average particle diameter (39.3 μm to 112.6 μm), relatively high thermal conductivity [2.068 W(mK) −1 to 2.966 W(mK) −1 ], and excellent thermal energy storage capacity (209.5 J/g to 278.2 J/g). Thus, the prepared Al-Si/Bi/Al 2 O 3 composite SLPCMs are potential thermal energy storage materials, which can be used to improve the energy efficiency of various industrial systems.

Molecular dynamics simulation on local structure and thermodynamic properties of molten ternary chlorides systems for thermal energy storage

Molten alkali chlorides mixtures are potential thermal energy storage materials. The structure and thermodynamic properties of LiCl-NaCl-KCl systems with different KCl concentrations were investigated by molecular dynamics simulation. The force field was verified by experimental data for the density and viscosity, and its precision was compared with the first-principle-based molecular dynamics simulation results. The densities obtained from rigid ion model were in satisfactory agreement with experimental values with a minimum error of 4.9% underestimation. The discrepancy in the structural information obtained by the two methods was no more than 1%. The local structure and thermodynamic properties were simulated across a full range of KCl concentration from 900 to 1200 K. The stability of cations coordination was analyzed by cage-out correlation function. The calculated self-diffusion coefficients, shear viscosity, heat capacity, and thermal conductivity were in good agreements with the available experimental data. The results showed that addition of KCl strengthened the correlation between unlike charged ions pairs, which was verified by the stability analysis. The stability of the first coordination shell determined the shear viscosities. Change in the structure affected the thermodynamic properties.

The equilibrium phase diagram of the pentaerythritol-pentaglycerine-2-amino-2methyl-1,3, propanediol (PE-PG-AMPL) system

Polyalcohols and amines have been considered as potential thermal energy storage materials, owing to their energetic solid-solid phase transitions. In this paper, we present equilibrium phase diagram of Pentaerythritol (PE)–Pentaglycerine (PG)– 2-amino-2methyl-1,3, propanediol (AMPL) ternary system that has been thermodynamically assessed using the CALPHAD method. A special class of, so called, “Plastic Crystals” have tetrahederally configured molecules with O–H⋯O or N–H⋯O layered or chained bonds in the low temperature phase, and store latent heat of transformation during solid-solid phase change in orientationally disordered crystals at higher temperatures. For example, in polyalcohols, there are O–H⋯O bond rotations around the C–C bonds that are responsible for storing large amounts of solid state phase change energy. Several binary equilibrium phase diagrams of polyalcohols, amines and combination thereof have been calculated and experimentally validated. We only know of three ternary phase diagram of these plastic crystals reported, to the best of knowledge. In the thermodynamic calculations of thePE-PG-AMPL system, we used the binary phase diagram experimental data for the optimization and calculation of excess energies. The binary systems have been optimized using regular and sub-regular solution models. The binaries as well as the ternary system have been calculated from room temperature to the liquid phase. The solution phases are modeled as substitutional solutions, in which the excess Gibbs energies are expressed by the Redlich–Kister–Muggianu polynomial. There is a very good agreement between previously reported experimental data and the calculated phase diagrams.

Developing a poly(ethylene glycol)/cellulose phase change reactive composite for cooling application

In this study, it was carried out the development of a poly(ethylene glycol)/cellulose phase change reactive composite as latent heat storage material for cooling application and determination of its thermal stability. Poly(ethylene glycol) (PEG) was grafted onto a cellulose backbone as solid–solid phase change material. The change in the surface morphology of the PEG1000 was studied by using a polarised optical microscopy (POM) instrument. Thermal analysis and thermal stability upon usage of the phase change composite material were performed by using a differential scanning calorimeter (DSC) instrument. The chemical analysis of the PCM composite was carried out by using a fourier transform infrared spectroscopy (FTIR) instrument. Phase change composite melted and crystallized 10 times to determine the thermal stability. The PEG1000 grafted cellulose phase change composite before 10 times thermal cycling absorbed 78.6 J/g of heat at 7.7 °C and released 74.4 J/g at − 5.4 °C whereas the PEG1000 grafted cellulose phase change composite after 10 times thermal cycling absorbed 92.7 J/g of heat at 8.3 °C and released 83.2 J/g at 1 °C during melting and freezing respectively. It was observed that Cp of the PEG1000 grafted cellulose sample was decreased compared to Cp of the pristine PEG1000. There was a considerable difference between crystal structures of pristine PEG1000 and PEG1000 grafted cellulose phase change composite. The disappearance of diisocyanate peak of TDI observed at 2228.34 cm−1 in PEG1000 grafted cellulose sample before and after 10 times thermal cycling was accepted as the evidence of polyurethane formation. As a result, PEG1000 grafted cellulose phase change composite was found as a potential thermal energy storage material for cooling application in relevant systems.

Heterogeneous Kinetic Features of the Overlapping Thermal Dehydration and Melting of Thermal Energy Storage Material: Sodium Thiosulfate Pentahydrate

The thermal dehydration of sodium thiosulfate pentahydrate (STS-PH), which has been studied as a potential thermal energy storage material, was investigated from the points of view of the physicoge...

Characterization of wastes based on inorganic double salt hydrates as potential thermal energy storage materials

Thermal energy storage (TES) is seen today as a key technology to reduce the existing gap between energy demand and energy supply in many energy systems. There are, currently, three well known methods to store thermal energy and they are: sensible heat storage (SHS), latent heat storage (LHT) and thermochemical heat storage. Every method has its own thermophysical requirements for the mediums of storage, such as thermal stability, high enthalpy of phase change or reaction, high heat capacity and suitable temperature of the thermal phenomenon for a respective application, among others. In this regard, the composition of materials usually needs to be modified in order to improve their performance or to reach a determined requirement. As a consequence, the costs of potential TES materials to be applied in renewable energy systems are too high to compete with traditional systems using fossil fuels. On the other hand, several wastes and by-products from the non-metallic mining, such as salt hydrates and double salts, are available without any application but accumulating in the mining sites. This is the case for astrakanite (Na2SO4·MgSO4·4H2O) and lithium carnallite (LiCl·MgCl2·7H2O) with no current application, and potassium carnallite (KCl·MgCl2·6H2O) used as a supplementary raw material to obtain KCl. Since the costs of these materials are close to zero, they were characterized as TES materials taking into account the properties required for the three methods of storage. Results showed that astrakanite and potassium carnallite have potential to be applied as thermochemical material at low-medium temperature (<300°C). Also, a dehydrated product obtained from astrakanite showed potential to be applied as phase change material (PCM) at high temperature, from 550°C to 750°C. Nevertheless, lithium carnallite did not show potential to be applied as TES material due to it low thermal stability, presenting partial decomposition below 200°C.

Thermophysical Properties of Potassium Fluoride Tetrahydrate from (243 to 348) K

Potassium fluoride tetrahydrate is of interest as a thermal energy storage material, due to its large specific and volumetric enthalpy of fusion and its low melting temperature. Here, we report the thermophysical properties of solid and liquid potassium fluoride tetrahydrate at temperatures from (243 to 348) K and compare this compound to water and octadecane, two other potential thermal energy storage materials with similar melting temperatures. Furthermore, we present a modified potassium fluoride–water phase diagram and accurately determine the enthalpies of fusion and melting temperatures for potassium fluoride tetrahydrate, ΔHfus = (246 ± 2) J·g–1 and Tfus = 291.6 K, and the potassium fluoride tetrahydrate–potassium fluoride dehydrate eutectic, ΔHfus = (203 ± 2) J·g–1 and Tfus = 282.2 K.

Thermophysical Properties of Lithium Nitrate Trihydrate from (253 to 353) K

Lithium nitrate trihydrate is of interest as a thermal energy storage material, due to its large specific and volumetric enthalpy of fusion and its low melting temperature. Here, we report the thermophysical properties of solid and liquid lithium nitrate trihydrate at temperatures from (253 to 353) K and compare this compound to water and octadecane, two other potential thermal energy storage materials. Furthermore, we examine the lithium nitrate–water phase diagram and accurately determine the enthalpies of fusion and melting temperatures for lithium nitrate trihydrate, ΔHfus = (287 ± 7) J·g–1 and Tfus = 303.3 K, and the lithium nitrate trihydrate–lithium nitrate eutectic, ΔHfus = (264 ± 2) J·g–1 and Tfus = 301.4 K.

Investigation on phase transitions of 1-decylammonium hydrochloride as the potential thermal energy storage material

1-Decylammonium hydrochloride was synthesized by the method of liquid phase synthesis. Chemical analysis, elemental analysis, and X-ray single crystal diffraction techniques were applied to characterize its composition and structure. Low-temperature heat capacities of the compounds were measured with a precision automated adiabatic calorimeter over the temperature range from 78 to 380 K. Three solid–solid phase transitions have been observed at the peak temperatures of 307.52 ± 0.13, 325.02 ± 0.19, and 327.26 ± 0.07 K. The molar enthalpies and entropies of three phase transitions were determined based on the analysis of heat capacity curves. Experimental molar heat capacities were fitted to two polynomial equations of the heat capacities as a function of temperature by least square method. Smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at intervals of 5 K based on the fitted polynomials.

Thermodynamic assessment of binary solid-state thermal storage materials

Polyalcohols are potential thermal energy storage materials that exhibit energetic solid-state phase transformations, and usually referred to as ‘Plastic Crystals’. The adjustment of solid-state phase transition temperatures is of significance to practical applications; phase diagram are useful for this purpose. We have established binary phase diagrams of 2-amino-2-methyl-1,3-propanediol (AMPL)–neopentylglycol (NPG), pentaerythritol (PE)–AMPL,tris(hydroxymethyl)aminomethane (TRIS)–NPG systems. In this work, we present results of our thermodynamic assessments of these organic binary systems. The CALPHAD approach using Thermo-Calc software was utilized for this purpose. It is interesting to note that two high temperature plastic phases co-exist in all three binaries considered here. Thermal energies are predominantly stored in these cubic γ or γ′ plastic phases in molecular librations (O–H⋯O bonds) and lattice vibrations. The calculated phase diagrams are in close agreement with the experimental phase diagrams.

Solid-Solid Phase Transition in Trimethylolpropane (TRMP)

An orientationally disordered crystalline (ODIC) plastic phase (γ) was observed in Trimethylolpropane (TRMP) during heating by high resolution thermal and X-ray diffraction analyses. TRMP is a potential thermal energy storage material. The enthalpies of solid-solid (α → γ at 327.8 K) and fusion (γ → liquid at 332.7 K) transitions are 16.36 kJ/mol and 0.9 kJ/mol, respectively. Supercooling was observed during solidification of melts, and this supercooled γ phase began to transform to a metastable crystalline phase, designated as α′, after 20 minutes at room temperature. The lattice parameters of the monoclinic α phase, obtained from this study, are:

Study of solid–solid phase change of ( n-C nH 2n+1 NH 3) 2MCl 4 for thermal energy storage

A series of bis( n-alkylammonium) tetrachlorometallates (II) ( n-C n H 2 n+1 NH 3) 2MCl 4 (C n M, where n=10, 12, 16 and M=Cu, Zn, Hg, Mn, Co, Ni) were synthesized and elementary analysis carried out. Their solid–solid phase transitions were studied using DSC and IR. Transition temperatures of C n Mn, C n Co, C n Zn and C n Cu lie between 28 and 86 kJ mol −1. They are potential thermal-energy storage materials. C n Ni, C n Cd, C n Hg are unsuitable for thermal storage use, because C n Ni has poor thermal stability; moreover, C n Cd and C n Hg in the low temperature has lower latent heat for these application.

Molecular association of normal alkanoic acids with their thallium(I) salts: a new homologous series of fatty acid metal soaps

A new homologous series of thallium(I) hydrogen dialkanoates, fatty acid thallium soaps, from the dipropane up to the ditetradecane is reported for the first time. This association with 1:1 stoichiometry is the only one exhibited by the thallium derivatives. They have been prepared by solidification of molten mixtures with equimolar proportions of acid and corresponding neutral salt, through crystallization from an anhydrous ethanolic solution of the mixture has also been successful in getting pure compounds with largest chain lengths. Vibrational spectroscopies clearly characterize these crystalline compounds as very strong hydrogen bonding systems. Assignations of active modes in proton and carbon nuclear magnetic resonance spectrometry (NMR) (in ethanol) and infrared (IR) and Raman spectra (in solid state) are reported. According to X-ray diffraction (XRD) they have monomolecular lamellar structures with the acyl chains arranged up and down to the cation/H-bond network in a methyl-to-methyl fashion, and vertically oriented to the basal plane. The acyl chains present all-trans conformation and alternating configuration (perpendicular orthorhombic subcell), like the beta'-phases of other kinds of lipids. Lamellar thickness is reported for the six room-temperature crystalline members. The molecular compounds present polymorphism, one crystal/crystal transition at temperatures close to the peritectical melting. Phase transition thermodynamics are also given and discussed with respect to their acid and salt parents. Their incongruent melting involves nearly 90% of the total enthalpic increments of both constituents' melting processes, making these compounds potential thermal energy storage materials.

Ionic Conductivity in Ordered and Disordered Phases of Plastic Crystals

Pentaglycerine (PG) and tris‐hydroxy‐aminomethane (Tris) are potential thermal energy storage materials which undergo energetic solid‐state phase transformations. The low temperature α‐phase structure of PG is body‐centered tetragonal and that of Tris is orthorhombic. The high‐temperature phase structure of both compounds is face‐centered cubic. Polymorphic changes in the structure occur at 89°C for PG and 135°C for Tris. These compounds are dielectrics at low temperature with conductivities on the order of 10−8 Ω−1 cm−1 (at 21°C) and 10−9 Ω−1 cm−1 (at 25°C), for PG and Tris, respectively. Heating samples from room temperature leads to an initial decrease in α‐phase conductivities followed by an increase for both of these compounds as a result of proton hopping. Continuous increases in the conductivity were observed at the transition temperature, with discontinuity evident in the case of PG. The conductivity variations in the α‐ and γ‐phases have been found to be thermally activated. The activation energies are nearly equal suggesting similar conduction mechanisms and charge carriers. From the relaxation time data, an equation has been obtained for the charge carrier self‐diffusion coefficient for the γ‐phase of PG, just above the transition temperature; . The conductivity in the γ‐phases are independent of the frequency in the range of 10 to 103 Hz. The temperature and frequency effects on the conductivities, relaxation times, and diffusional parameters of PG and Tris are presented.