Thermal Energy Storage Density Research Articles

Experimental study of Lannea microcarpa seed oil as a heat transfer fluid or thermal energy storage material for medium-temperature applications

In this study, we investigated the suitability of Lannea microcarpa seed oil (LaMSO) as a heat transfer fluid (HTF) and thermal energy storage material (TESM) for medium-temperature applications, focusing on its performance in concentrated solar power (CSP) plants. LaMSO demonstrated higher specific heat capacity than both Dowtherm A and Xceltherm 600 across the temperature range of 30 °C to 300 °C. It also exhibited a volumetric thermal energy storage density similar to, or approximately 10 % greater than, that of Dowtherm A and Xceltherm 600 at 210 °C. The oil was subjected to isothermal aging at 210 °C for 500 h and 1000 h, followed by analysis of its thermophysical and chemical properties. Thermogravimetric analysis demonstrated excellent thermal stability, with less than 3 % mass loss after 1000 h of aging. The density remained relatively unchanged, indicating consistent performance as a HTF or TESM. Despite an increase in viscosity at 40 °C, the viscosity at 100 °C remained comparable between the new and aged LaMSO samples. Furthermore, the flash point also showed no significant change, remaining high even after 1000 h of aging. However, challenges arise from the increase in the melting point due to oil saturation, which poses a risk of solidification in pipelines or tanks in certain climates. From the perspective of thermal storage cost per kWh, LaMSO is cheaper than Dowtherm A and Xceltherm 600, being approximately 8 times and 3 times less expensive, respectively. Overall, the findings suggest that LaMSO holds promise as an effective and sustainable alternative for HTF and TESM applications across a wide temperature range, contributing to advancements in renewable energy technology.

Thermally driven MnCl2[sbnd]NH4Cl resorption cycle for seasonal thermal management of urban buildings

The frequency of extreme weather conditions caused by global greenhouse gas emissions has led to a significant increase in energy consumption for refrigeration and heating supply in urban buildings. However, conventional sensible and latent heat storage technologies hold low thermal energy storage density and short-term energy storage capabilities. Additionally, electrically driven compression refrigeration with non-negligible global warming potential (GWP) is unsuited to high ambient temperatures in summer. We propose an advanced strategy, adopting the MnCl2NH4Cl resorption cycle to achieve efficient desorption refrigeration of NH4Cl and resorption heating supply of MnCl2 under seasonal conditions. Experimental results have demonstrated that our proof-of-concept system can output 70 °C heat with a thermal energy storage density of 166.2 kJ·kg−1, providing continuous heating for 30.5 min under the winter ambient temperature of 10 °C. Moreover, COPref remained at 0.589 for continuous indoor refrigeration lasting 58.5 min under summer ambient and refrigeration temperatures of around 30 °C and 2 °C, respectively. This exceptional adaptability to ambient temperatures enables efficient adjustment of urban building comfort. Our work presents a promising zero-carbon pathway for replacing conventional fossil fuels employed in the thermal management of urban buildings with solar energy.

Hydrophobic Multilayered PEG@PAN/MXene/PVDF@SiO2 Composite Film with Excellent Thermal Management and Electromagnetic Interference Shielding for Electronic Devices.

With the rapid development of electronic industry, it's pressing to develop multifunctional electromagnetic interference (EMI) shielding materials to ensure the stable operation of electronic devices. Herein, multilayered flexible PEG@PAN/MXene (Ti3C2Tx)/PVDF@SiO2 (PMF) composite film has been constructed from the level of microstructure design via coaxial electrospinning, coating spraying, and uniaxial electrospinning strategies. Benefiting from the effective encapsulation for PEG and high conductivity of MXene coating, PEG@PAN/MXene composite film with MXene coating loading density of 0.70mg cm-2 exhibits high thermal energy storage density of 120.77 J g-1 and great EMI shielding performance (EMI SE of 34.409dB and SSE of 49.086dB cm3 g-1) in X-band (8-12GHz). Therefore, this advanced composite film can not only help electronic devices prevent the influence of electromagnetic pollution in the X-band but also play an important role in electronic device thermal management. Additionally, the deposition of nano PVDF@SiO2 fibers (289±128nm) endowed the PMF composite film with great hydrophobic properties (water contact angle of 126.5°) to ensure the stable working of hydrophilic MXene coating, thereby breaks the limitation of humid application environments. The finding paves a new way for the development of novel multifunctional EMI shielding composite films for electronic devices.

Overcoming thermal energy storage density limits by liquid water recharge in zeolite-polymer composites

Overcoming thermal energy storage density limits by liquid water recharge in zeolite-polymer composites

A comparative analysis on charging performance of triplex-tube heat exchanger under various configurations of composite phase change material

In present work, the melting performance of triplex-tube latent heat thermal energy storage (LHTES) unit was numerically studied using equal volumes of PCM and metal foam composite PCM (CPCM) in various arrangements. For the n-eicosane (as PCM), the study was conducted at the fixed Rayleigh number (Ra) = 4.08x107, Prandtl number (Pr) = 62.9, and Stefan number (Ste) = 0.14. The results showed that positioning the metal foam on the bottom side and distributing segmented CPCM with alternating PCM zones effectively improved the system performance. Moreover, this also prevents the overheating of thermal layers in the LHTES unit. While the model labelled M2 exhibited the highest economic efficiency among all isotropic models, its low dimensionless thermal energy storage (TES) density (i.e., q’ ∼ 0.6) led this study to focus on models falling under the category having a TES density of ∼ 0.8. Compared to a pure PCM model, the configurations under equal volume ratio category demonstrated up to ∼ four times higher TES rate (p’) and the significant reduction of ∼ 75 % in melting time. The optimized isotropic model achieved the highest TES rate per unit cost with peak value of ∼ 3 at a price ratio (N) of 1. Lastly, the testing of metal foam anisotropy on the chosen design showed a substantial increase in melting/heat storage rates. The largest drop of ∼ 33 % in the total melting time was noticed for model M2 as compared to isotropic case.

Al2O3 nanoparticles for enhanced thermal performance in NaCl–KCl–Na2CO3 system: From thermodynamic prediction to system level assessment

With the introduction of the Brayton cycle technology, molten salts have become one of the most promising thermal storage materials in thermal energy storage (TES) systems. In this study, a novel eutectic salt (ES) NaCl–KCl–Na2CO3 was used as the base salt and Al2O3 nanoparticles (NPs) as additives to prepare Nano-ES. Both thermal analysis and molecular dynamics results showed that the doping of Al2O3 NPs improved the thermophysical properties of the ES. In particular, the TES density and liquid-state thermal conductivity of the ES increased by 11.60 % and 28.62 %, respectively, when the content of NPs was 2.0 wt%. The improvement in thermophysical properties was attributed to the NPs-induced change in the microstructure of the ES. However, the doping of NPs led to inevitable increase in the viscosity of the ES, which directly affected the strength of natural convection. This study further analyzed the melting process of ES and Nano-ES in shell-tube TES system, and the results showed that the melting rate of TES materials was affected by natural convection and thermal conductivity. The ES with lower viscosity and thermal conductivity exhibited a melting rate close to that of Nano-ES at 420–540 s stage. The viscosity of the TES materials should not be neglected during the application of TES systems. This study provides an important guiding significance for the selection of molten salts and additives for high-temperature TES systems.

Low-carbon shape-stable phase change composite utilizing semi-coke ash for building thermal energy storage

To enhance the efficiency and cost-effectiveness of heating, air-conditioning, and solid waste recycling in buildings, this work proposed the solid waste semi-coke ash as skeleton material and the sodium carbonate as phase-change material to produce shape-stable phase-change composites using the cold compression-hot sintering method for building thermal energy storage. Eight shape-stable phase-change composites were prepared and the detailed chemical compatibility, thermal property, structural and mechanical performance, and micromorphology were investigated by X-ray diffraction, differential scanning calorimetry, laser flash analysis, N2 adsorption and desorption method, constant speed pressurization method, and scanning electron microscopy. Results demonstrated that semi-coke ash is suitable with sodium carbonate for fabricating shape-stable phase-change composites. The optimal mass ratio of semi-coke ash to Na2CO3 powder for sample CC3 was determined to be 52.5:47.5. This particular sample demonstrated a thermal energy storage density of 961.58 J/g and a maximum thermal conductivity of 1.306 W/(m ∙ K). It also exhibited excellent chemical compatibility between its components. Furthermore, sample CC3 displayed a mechanical strength of 23.57 MPa, with elements evenly distributed throughout. Importantly, CO2 emission from the production of sample CC3 was significantly low, indicating great potential for commercialization.

Sodium acetate-based thermochemical energy storage with low charging temperature and enhanced power density

The electrification of heat necessitates the development of innovative domestic heat batteries to effectively balance energy demand with renewable power supply. Thermochemical heat storage systems show great promise in supporting the electrification of heating, thanks to their high thermal energy storage density and minimal thermal losses. Among these systems, salt hydrate-based thermochemical systems are particularly appealing. However, they do suffer from slow hydration kinetics in the presence of steam, which limits the achievable power density. Additionally, their relatively high dehydration temperature hinders their application in supporting heating systems. Furthermore, there are still challenges regarding the appropriate thermodynamic, physical, kinetic, chemical, and economic requirements for implementing these systems in heating applications. This study analyzes a proposal for thermochemical energy storage based on the direct hydration of sodium acetate with liquid water. The proposed scheme satisfies numerous requirements for heating applications. By directly adding liquid water to the salt, an unprecedented power density of 5.96 W/g is achieved, nearly two orders of magnitude higher than previously reported for other salt-based systems that utilize steam. Albeit the reactivity drops as a consequence of deliquescence and particle aggregation, it has been shown that this deactivation can be effectively mitigated by incorporating 10 % silica, achieving lower but stable energy and power density values. Furthermore, unlike other salts studied previously, sodium acetate can be fully dehydrated at temperatures within the ideal range for electrified heating systems such as heat pumps (40 °C – 60 °C). The performance of the proposed scheme in terms of dehydration, hydration, and multicyclic behavior is determined through experimental analysis.

Development of a Two‐Stage Hydrogen‐Based Thermochemical Energy Storage System

Both energy conservation and the use of renewable resources are necessary due to the global increase in energy demand. A useful technique for energy storage, when renewable energy sources are available, is a thermochemical energy storage system that relies on the interaction of gases with solids. From this vantage point, hydrogen offers a sustainable and regenerative response to this pressing issue. In line with that, herein, the operation of a novel two‐stage hydrogen‐based thermochemical energy storage system (TS‐H‐TCES) is proposed to attain a higher energy density and is analyzed with the help of the thermodynamic cycle. The proposed system operates at 298, 373, 403, and 423 K as atmospheric temperature (Tatm), waste heat input temperature (Tm), storage temperature (Ts), and upgraded/enhanced heat output temperature (Th), respectively. For the given operating temperature, the thermodynamic performance of TS‐H‐TCES is evaluated using experimentally measured pressure–concentration isotherms of LaNi4.7Al0.3, LaNi4.6Al0.4, and MmNi4.6Al0.4. The maximum coefficient of performance, second law efficiency (ηII), and thermal energy storage density are found to be 0.67, 0.70, and 220.98 kJ kg−1, respectively. The impact of operating temperatures on system performance is also investigated, which is important in choosing the best temperature range for a certain application.

Effect of carbon capture on desulfurization gypsum/carbide slag phase-change composites for waste removal and renewable energy storage

To promote the recycling of industrial waste and produce ultra-low carbon energy storage materials with low-energy consumption this work innovatively proposes to capture carbon dioxide using the mixture made of 70 wt% desulphurization gypsum and 30 wt% carbide slag via a aqueous solution method, and the carbonized mixture used as skeleton material to prepare phase-change composites via cold pression & hot sintering method, and then thermal property, mechanical property and chemical compatibility are investigated. Results show that the carbon capture rate of the skeleton material can reach up to 10.6% at room temperature and can encapsulate the PCM (NaNO3) intact. C-PCC3 has good thermal stability and can undergo 2058 heating/cooling cycles. Compared with the PCC3 (absent carbon capture), the C-PCC3 exhibited a notable enhancement in thermal conductivity by 2.7%. Nevertheless, there was a decrease in mechanical strength from 134.1 MPa to 44.9 MPa, and a reduction in thermal energy storage density from 483.2 J/g to 459.3 J/g. Based on both macroscopic properties and microscopic morphology, the phase change composite materials fabricated in this work exhibit excellent comprehensive property.

Photoelectric dual-mode triggered phase change materials for all-weather personal thermal management and shape memory

To cope with the demand of more complex and variable applications, it is urgent to develop dual-mode triggered, breathable, and shape-memory wearable heaters for all-weather personal thermal management of composite phase change materials (PCMs). Herein, after high-temperature carbonization of ZnCo-MOF (metal–organic framework) nanosheet array grown in situ on flexible and breathable carbon cloth (CC) and subsequent encapsulation of polyethylene glycol (PEG), the as-prepared PEG/CC@Co/CNT (carbon nanotube) composite PCMs exhibited good breathability, mechanical strength (tensile strength of 9.15 MPa), thermal energy storage density (114.19 J/g), and shape memory due to the synergy of flexible CC skeleton and rigid PEG. More importantly, composite PCMs possessed excellent solar-thermal (93.7 %, 100 mW/cm2) and electro-thermals (94.5 %, 2.0 V) conversion and storage capacity, benefiting from the conjugation effect of high graphitized carbon/carbon heterostructure with fast electron/photon/phonon transmission and the localized surface plasmon resonance effect of Co nanoparticles. Therefore, the integration of solar heating and Joule heating into breathable composite PCMs can be accurately used for next-generation all-weather, all-season, dual-mode triggered personal thermal management, including indoor/outdoor, daytime/night, rainy/cloudy and other complex and changeable scenarios.

Silica dopant effect on the performance of calcium carbonate/calcium oxide based thermal energy storage system

The CaCO3 is being studied for its application in thermal energy storage. However, it has drawbacks of slow reaction rate during calcination and incomplete reversible carbonation which limit its use. In this paper, SiO2 has been studied as a dopant for CaCO3 to improve its cyclic performance. The CaCO3 samples were loaded with different concentrations of SiO2 and its effect on the thermal energy density of CaCO3 was determined. Afterwards, the effect of the dopant on the heat storage process of the synthesized composite along with kinetics of decarbonation reaction was investigated. Cyclic tests were performed to determine the reusability of the material. It was found that the addition of dopant helped to increase the rate of decarbonation reaction, thereby making the heat storage process more efficient as compared to pure CaCO3. The activation energy values are 255.9 kJ/mol, 280.1 kJ/mol, 244.9 kJ/mol, and 234.8 kJ/mol for 5%, 15%, 30%, and 0% doped SiO2 samples, respectively. Furthermore, thermal energy storage density increases when the amount of dopant decreases in the samples such as the 30% and 5% doped samples have gravimetric energy storage densities of 339.85 J/g and 759.24 J/g, respectively. It was observed that the large quantities (15% and 30%) of dopant had introduced a new phase of Ca3SiO5 during CaCO3 decomposition.

Energizing the Thermal Conductivity and Optical Performance of Salt Hydrate Phase Change Material Using Copper (II) Oxide Nano Additives for Sustainable Thermal Energy Storage

Due to intermittent nature of solar energy, scientists and researchers are working to develop thermal energy storage (TES) systems for effectively use the solar energy. One promising avenue involves utilizing phase change materials (PCMs), but primary challenge lies in their limited thermal conductivity, which results in slower heat transfer rate and lower thermal energy storage density. The present research work demonstrates, to develop and explore a PCM composite by embedding salt hydrate and coper (II) oxide to enhance the heat transfer mechanism for potential utilization of TES material. The optical behavior, and thermal conductivity were analyzed by using Ultraviolet visible spectrum, and thermal property analyzer. The developed copper oxide dispersed PCM composite displayed the thermal conductivity was energized up to 71.5 % without affecting the other properties. Also, the optical absorptance was remarkably enhanced and the transmittance reduced to 87 %. Increasing the concentration of copper oxide nanoparticles in the salt hydrate PCM improves the optical absorptivity and heat conductivity. With these extraordinary abilities the nanocomposite could play a significant role in progress of sustainable TES with significance to contribute towards sustainable development goal of affordable and clean energy and climate change.

Energizing the thermophysical properties of phase change material using carbon-based nano additives for sustainable thermal energy storage application in photovoltaic thermal systems

As solar energy are intermittent in nature and not predictable, researchers and scientists are actively developing efficient thermal energy storage (TES) systems intending to maximize the utilization of solar energy. Phase change materials (PCM) are potential materials that are largely accessed towards TES. However, the notable drawback of PCM is their lower thermal conductivity, leading to slower heat transfer rates and reduced thermal energy storage density. Thus, the current study focuses on developing and exploring a PCM composite by embedding paraffin wax and graphene to enhance the heat transfer mechanisms, making it a promising option for TES applications. Various aspects of the composite's performance were examined, including its microstructural behaviour, chemical stability, thermal stability, thermal conductivity, thermal reliability, and heat transfer characteristics. The findings revealed that the inclusion of graphene led to a substantial increase of up to 75.09 % in thermal conductivity while preserving the melting enthalpy of the material. The newly developed nanocomposite also demonstrated chemically and thermally stable up to a temperature of 210 °C, and the thermal stability was slightly enhanced by adding nanoparticles. This nanocomposite also exhibited improved optical absorptance and reduced transmittance, enhancing its potential for solar energy absorption. It further demonstrated durability, maintaining stability even after undergoing 500 thermal cycles. Notably, the overall efficiency of the nano-enhanced PCM integrated photovoltaic-thermal system (PVT) enhanced by 29 % and 49 % greater than the PVT system and conventional PV system. Given these exceptional characteristics and performance enhancements, this nanocomposite material holds promise for significantly advancing future sustainable TES technologies.

Self-Assembly of Binderless MXene Aerogel for Multiple-Scenario and Responsive Phase Change Composites with Ultrahigh Thermal Energy Storage Density and Exceptional Electromagnetic Interference Shielding

HighlightsThis work proposes a tactic for improving the efficiency of thermal energy conversion and expanding the application scenarios of phase change materials by constructing non-binder and oriented MXene-K+ aerogel.The prepared phase change composites (PCCs) can rapidly transform solar, electric, magnetic energy into latent heat for keeping warm, power generation, and thermal physiotherapy.Owing to the suggested tactic, the prepared PCCs achieves ultrahigh energy storage density and realize 99.9998% electromagnetic wave energy attenuation.

Multi-wall carbon nanotubes tailored eutectic composites for solar energy harvesting

Carbonaceous thermal energy storage involving PCMs has gained an increasing research interest owing to their higher thermal conductivity and energy storage density. The current work analyses the thermophysical properties of a nano-enhanced eutectic phase change material (NeUPCM) laden with different concentrations (ranges from 0 wt% - 0.7 wt%) of multi-wall carbon nanotube (MWCNT). Paraffin wax-palmitic acid (PW-PA) binary eutectic was produced initially by facile melt blending, and then MWCNTs were doped via standard two-step nanocomposite synthesis protocol. Nanocomposites showed a slower decomposition rate, and the thermal resistance index improved. MWCNT enhance the thermal conductivity of the eutectic base (140 %), which reaches a maximum value of 0.619 W/(m·K) for 0.5 wt% loadings, and the maximum increment of 13.2 % of latent heat was noted for 0.7 wt% loading of MWCNT (which is having a melting temperature of 53 °C). The sample doped with 0.5 wt% MWCNT(C3) showed the highest thermal effusivity. The NeUPCMs also displayed improved photothermal performance and solar absorptivity. Corrosion analysis against copper revealed that the composite is suitable for long-term usage. The NeUPCMs maintained good reliability even after 500 melt-freeze cycles. In short, the proposed NeUPCMs hold significant potential to be employed for thermal energy storage purposes.

Using phase change material to reduce the loss of quantum yield of fluorescent polymer when exposed to high temperature

The quantum yields (QYs) of fluorescent materials decrease significantly as temperature rises, and this loss of QYs will become irreversible when exposed to high temperature for a long time. Herein, we prepare a zinc polyacrylate (ZnPA)/polyethylene glycol (PEG) composite using PEG-20000 as the phase change material (PCM) to reduce the loss of the QY of fluorescent ZnPA when exposed to high temperature. This composite is also a PEG-based form-stable PCM that is in solid state at 90 °C, solving the leakage issue of pure PEG in the melting process. Most important, the QY of ZnPA decreases by 50.4 % after a long period of thermal cycling, while that of the ZnPA/PEG composite does not decrease at all. This comparison indicates PEG-20000 can greatly reduce the loss of the QY of ZnPA when exposed to high temperature, in virtue of its excellent thermal energy storage density and negligible temperature change in the phase change procedures, as well as the rapid heat transfer between PEG-20000 and ZnPA.

Advancements in Phase Change Materials: A Path to Sustainable Energy Solutions in China

With the rapid development of China, the country's demand for energy has significantly increased. According to the "World Energy Outlook 2020," China's annual average growth rate of primary energy consumption is 1.9%, and it is predicted that China's energy consumption will account for over 20% of global energy consumption by 2050. In the energy budget, 90% is allocated to thermal energy conversion, transmission, and storage. Facing an impending energy crisis, enhancing energy production while minimizing energy loss has become a matter of widespread concern. Phase Change Materials (PCMs), also called phase change energy storage materials, have garnered attention as a novel energy-efficient and environmentally friendly material. PCMs refer to substances that undergo a change in state and provide latent heat without changing their temperature. Phase change thermal storage materials utilize phase transitions during heat exchange processes to store energy by means of these phase changes. Compared to chemical energy storage materials, PCMs offer high thermal efficiency and energy storage density, maintain constant temperature, and are more easily controllable. They hold great potential as a promising material in the field of thermal energy storage and have been widely applied in areas such as solar energy, lithium batteries, building insulation, and medical applications. This article offers a comprehensive overview of the principles and classification of Phase Change Material (PCM), including organic PCM, inorganic PCM, and composite PCM. It discusses their applications in solar thermal energy storage, cooling of photovoltaic panels, building materials, and industrial waste heat recovery. The article also highlights China's research and development efforts in these areas, emphasizing the country's significant contributions to advancing PCM technology.

Characterization and performance investigation of UiO-66 for low-grade thermochemical adsorption heat storage

Thermochemical energy storage can improve low-grade energy utilization efficiency, thereby reducing buildings' operating energy consumption. However, common thermochemical thermal storage materials have poor stability and low energy storage density. To this end, it put forward to use UiO-66 as a novel low-grade thermal energy storage material. It was synthesized and characterized, and its thermal conductivity, optimal activation temperature and time, adsorption kinetics and thermal energy storage density were also comprehensively studied. The results showed that the thermal conductivity of UiO-66 was 0.282 W/(m·K) at 30 °C. The optimal activation temperature and time for UiO-66 were 100 °C and 1.5 h taking into account the balance between the high water uptake and energy saving. The water uptake of UiO-66 at 30 °C and 80% RH reached 0.410 g/g, 2.1 times that of Zeolite 13X. The adsorption behavior of water vapour in UiO-66 was accurately described by the pseudo-second-order kinetic model. The thermal energy storage density of UiO-66 was 818 kJ/kg, which was 1.6 times higher than that of Zeolite 13X (515 kJ/kg), demonstrating excellent thermal storage performance. To sum up, the research results showed that UiO-66 had application potential in low-grade thermal energy storage fields such as heat from solar collector and industrial waste heat.

Investigation on low-carbon shape-stable phase change composite by steel slag and carbide slag for solar thermal energy storage

Resources utilization of a variety of industrial solid wastes including steel slag (SS) and carbide slag (CS) is an effective measure that reduces environmental destruction and greenhouse gas emissions. In this work, seven shape-stable phase change materials (SSPCMs) with different mass fractions were prepared by cold compression-hot sintering (CCHS) method utilizing SS and CS as the skeleton material (SM) and NaNO3 as the phase change material (PCM). Research on critical properties of SSPCMs including thermal energy storage properties, microscopic morphology, mechanical properties, chemical compatibility, and economic properties was undertaken. Results indicated that various properties were optimized when the mass ratio of SS, CS, and NaNO3 was 2.5:2.5:5 (SC4). The mechanical strength of sample SC4 was 131.2 MPa, and the optimum thermal energy storage (TES) density in the temperature range of 100 °C–400 °C was 371.1 J/g. The maximum thermal conductivity of sample SC4 was 1.263 W/(m·K) after 1307 heating and cooling cycles. The sample SC4 exhibited favorable chemical compatibility and the elements were uniformly distributed in the sample SC4.