Heat Storage Ability Research Articles

Numerical and Design Study of Beehive in Building for Thermal Storage During Hours of Absence of Solar Radiation

This study investigates the numerical and design performance of Phase Change Materials (PCMs) embedded in a beehive structure within building envelopes for thermal energy storage during periods without solar radiation. Using Computational Fluid Dynamics (CFD) simulations in ANSYS Fluent, the study examines how the PCM system stabilizes indoor temperatures and improves energy efficiency. The research focuses on three months: January, November, and December, in Baghdad, Iraq, where diurnal solar radiation variations and temperature patterns are prevalent. Results reveal that the PCM-enhanced structure effectively absorbs heat during peak solar radiation hours, with solar radiation peaking at 574 W/m² in January, 596 W/m² in November, and 557 W/m² in December. The heat storage and release ability of the PCM keep up the interior temperature at its maximum of 309.96K and 310.04 K in Jan and Nov and 309.23 K in Dec with slightly less drop in the evening. The heat transfer coefficient was maximum in November 11.37 W/m²·K, while the PCM mass fractions showed significant phase change and the maximum value 0.425 in November. The thermal efficiency of the system was highest in November at 68.23% and also fluctuates slightly in the other remaining months. This study suggests that PCM systems, especially with the beehive structure, additionally improve isothermal stability and energy densities of the buildings in the changing climate, which is cost-effective and a more environmentally friendly strategy for regulating heating and cooling requirements.

Nanographene oxide modified fiber reinforced cementitious composites: Thermomechanical behaviour, environmental analysis and microstructural characterization

A novel fiber reinforced cementitious composites was developed by incorporating microencapsulated phase change materials (PCMs) and nanographene oxide (NGO) to enhance the composites’ thermal properties without compromising the compressive strength. Regarding the thermo-mechanical properties, with the addition of NGO, while mechanical properties improve, thermal mass increases and the heat storage ability of the produced composite material enhances. In this situation; it can be interpreted that it will be possible to benefit more from the energy stored by PCMs, as the energy required to change the temperature of the unit mass of the material will decrease. The environmental impact assessment has also revealed that CO2 emissions from production increase with the use of PCMs. However, it has been determined that the addition of NGOs will make a positive contribution to the life cycle, as CO2 emissions resulting from cement will decrease. In conclusion, a novel fiber reinforced composite with enhanced thermal and mechanical properties by combining PCMs and NGO has shown a great potential for environmentally friendly buildings with the integration of structure, energy conservation and long term durability.

Effect of heat transfer and storage ability of silicon carbide (SiC) ceramic particles on the microwave deicing characteristics of cement-based materials

Microwave heating has been applied to improve cement-based materials (CBMs) structures deicing efficiency, which reduce the effect of icing on their service life. Moreover, the enhanced thermal properties of CBMs can further improve their deicing efficiency. In this study, silicon carbide (SiC) ceramic particles with favorable thermal properties were used to prepare the SiC cement-based materials (SCBMs). The effect of SiC ceramic on the mechanical strength of CBMs was investigated. Next, the heat transfer and storage ability of CBMs were investigated to analyze the changes in their thermal-physical parameters. Then, the surface thermal responses of the CBMs during microwave heating and off were recorded to characterize their temperature evolution in a low-temperature condition. Furthermore, the deicing efficiency of CBMs was determined using the ice layer shedding time (ILST) as the index. The results show that the filling effect of SiC ceramic on CBMs improved their mechanical strength within a certain content range. However, a large content of SiC ceramic caused an increase in the weak area and porosity within the CBMs, further reducing their mechanical properties. The thermal-physical parameters of CBMs were improved after adding SiC ceramic. The thermal conductivity and thermal effusivity of SCBMs-100 were 13.17 W/(m·K) and 1.44 W/(mm2·K), respectively, 7.90 and 2.35 times higher than the control group. Due to the favorable thermal properties of SCBMs, their heating rate and surface temperature field distribution characteristics were further improved. Furthermore, with the increase of SiC ceramic content, the ILST of SCBMs was further reduced during microwave heating. Therefore, the SiC ceramic was a favorable material, improving the thermal properties and deicing efficiency of CBMs to a certain extent. However, considering its effect on the deterioration of the mechanical properties of CBMs, the optimal content of SiC ceramic might be 75%.

Calcium-looping thermochemical energy storage and mechanical performance of bio-templated CaO-based pellets under steam-containing environments

The calcium-looping thermochemical heat storage is recognized as a promising technology due to its affordable raw material expense, eco-friendliness, and superior heat storage and release capacity. To investigate the impact of inert support, pore-forming template, and reaction atmosphere on the cyclic thermochemical heat storage capacity and mechanical properties of calcium-based sorbent, spherical CaO-based pellets were prepared using cement as an inert support and microcrystalline cellulose, starch, and sesbania gum as pore-forming templates. The test results demonstrated that the optimal composition ratio for calcium-based particles was 5 wt% cement and 10 wt% pore-forming template. Calcium-based particles containing 5 wt% cement and 10 wt% cellulose demonstrated the highest thermal storage capacity. The steam-containing atmosphere reduced the heat storage ability of the calcium-based particles, but it greatly improved their mechanical characteristics. After undergoing 50 cycles with 10 vol% steam injection during calcination, the calcium-based pellets exhibited a mere 6.09 % reduction in E¯g,N compared to the heat storage cycle without steam addition. In contrast, the average crushing strength experienced a remarkable increase of 42.65 %, while the attrition rate decreased by 30.18 %.

Novel heat storage ionomer binder for thermal management of Li-ion batteries

A novel heat storage ionomer binder with highly efficient heat-storage ability is proposed to function as an internal temperature conditioner, which allows the battery to function steadily over a wider temperature range.

Thermo-kinetic behaviour of green synthesized nanomaterial enhanced organic phase change material: Model fitting approach

Metal, carbon and conducting polymer nanoparticles are blended with organic phase change materials (PCMs) to enhance the thermal conductivity, heat storage ability, thermal stability and optical property. However, the existing nanoparticle are expensive and need to be handle with high caution during operation as well during disposal owing to its toxicity. Subsequently handling of solid waste and the disposal of organic PCM after longevity usage are of utmost concern and are less exposed. Henceforth, the current research presents a new dimension of exploration by green synthesized nanoparticles from a thorny shrub of an invasive weed named Prosopis Juliflora (PJ) which is a agro based solid waste. Subsequently, the research is indented to decide the concentration of green synthesized nanoparticle for effective heat transfer rate of organic PCM (Tm = 35–40 °C & Hm = 145 J/g). Furthermore, an in-depth understanding on the kinetic and thermodynamic profile of degradation mechanism involved in disposal of PCM after usage via Coats and Redfern technique is exhibited. Engaging a two-step method, we fuse the green synthesized nanomaterial with PCM to obtain nanocomposite PCM. On experimental evaluation, thermal conductivity of the developed nanocomposite (PCM + PJ) increases by 63.8% (0.282 W/m⋅K to 0.462 W/m⋅K) with 0.8 wt% green synthesized nanomaterial owing to the uniform distribution of nanoparticle within PCM matrix thereby contributing to bridging thermal networks. Subsequently, PCM and PCM + PJ nanocomposites are tested using thermogravimetric analyzer at different heating rates (05 °C/min; 10 °C/min; 15 °C/min & 20 °C/min) to analyze the decomposition kinetic reaction. The kinetic and thermodynamic profile of degradation mechanism involved in disposal of PCM and its nanocomposite of PCM + PJ provides insight on thermal parameters to be considered on large scale operation and to understand the complex nature of the chemical reactions. Adopting thirteen different chemical mechanism model under Coats and Redfern method we determine the reaction mechanism; kinetic parameter like activation energy (Ea) & pre-exponential factor (A) and thermodynamic parameter like change in enthalpy (ΔH), change in Gibbs free energy (ΔG) and change in entropy (ΔS). Dispersion of PJ nanomaterial with PCM reduces Ea from 370.82 kJ/mol−1 to 342.54 kJ/mol−1 (7.7% reduction), as the developed nanomaterial is enriched in carbon element and exhibits a catalytic effect for breakdown reaction. Corresponding, value of ΔG for PCM and PCM + PJ sample within heating rates of 05–20 °C/min varies between 168.95 and 41.611 kJ/mol−1. The current research will unbolt new works with focus on exploring the pyrolysis behaviour of phase change materials and its nanocomposite used for energy storage applications. This work also provides insights on the disposal of PCM which is an organic solid waste. The thermo-kinetic profile will help to investigate and predict the optimum heating rate and temperature range for conversion of micro-scale pyrolysis to commercial scale process.

Validated simulation of thermal performance of phase change material infused recycled brick aggregate in 3D printed concrete

Passive design solutions are important in reducing the amount of heating and cooling energy required to maintain thermal comfort inside a building, without adding to the problem of climate change. Phase change materials (PCMs) are a thermal energy storage passive design solution, with the ability to change phase and store heat at chosen temperatures. PCMs can be added to concrete to create PCM-concrete, a composite material with sensible and latent heat storage ability. The purpose of this research is to create an accurate 2D model which can be used to determine the heat transfer through 3D printed concrete (3DPC) building façades containing PCM. Two building façade wall sections are simulated in ABAQUS and validated by thermal tests – a reference 3DPC façade section, in which 64% of the natural aggregate is replaced with recycled brick aggregate (RBA-3DPC), and a PCM-3DPC façade section, containing the same replacement level of RBA but with PCM vacuum impregnated into the RBA. With the validated model, computational simulations of the thermal performance of the PCM-3DPC façade section with varying PCM melting temperatures and different façade surface colours are tested. Subsequently, a PCM-3DPC façade section with 100% replacement of natural aggregate with RBA, infused with PCM of two melting temperatures (such as 18 °C for activation in winter and 28 °C for activation in summer) is proposed for climates with large seasonal temperature changes. In addition, contrary to most studies, an iterative approach was used for modelling cavity convection and internal ambient temperature, and this approach is found to be necessary, so as not to over constrain the model with set façade and internal temperatures.

Experimental design of paraffin/methylated melamine-formaldehyde microencapsulated composite phase change material and the application in battery thermal management system

In order to maintain the optimal operating temperature of the battery surface and meet the demand for thermal storage technology, battery thermal management system based on phase change materials has attracted increasing interest. In this work, a kind of core-shell structured microcapsule was synthesized by an in-situ polymerization, where paraffin was used as the core, while methanol was applied to modify the melamine-formaldehyde shell to reduce toxicity and improve thermal stability. Moreover, three different types of heat conductive fillers with the same content of 10 wt.%, i.e., nano-Al2O3, nano-ZnO and carbon nanotubes were added, generating composites. The microcapsules were uniform, and were not affected by the thermal fillers, which were evenly dispersed around. The composite sample with carbon nanotubes (10 wt.%) showed the highest thermal conductivity of 0.50 W/(m K) and latent heat of 139.64 J/g. Furthermore, according to the leakage testing and battery charge/discharge experiments, compared with Al2O3 and ZnO, the addition of carbon nanotubes remarkably enhances the heat storage ability as latent heat from 126.98 J/g for the prepared sample with Al2O3 and 125.86 J/g for the one with ZnO, then to 139.64 J/g, as well as dissipation performance as a cooling effect by decreasing the surface temperature of battery from 2% to 12% of microcapsule, composite sample with carbon nanotubes presents a broad application prospect in battery thermal management system and energy storage field.

Evaluation of Thermal and Rheological Properties of Phase Change Material-Incorporated Asphalt Mastic with Porous Fillers

Incorporating phase change material (PCM) into paving materials can regulate the pavement temperature, improve the pavement durability, and mitigate the heat-island effects. In this research, porous fillers were used as the PCM carrier, and the thermal and rheological behaviors of the asphalt mastic with the PCM were evaluated. Two different carrier materials (diatomite and expanded perlite) and four types of PCMs were used in the study. The candidate filler, PCM, and proper blending ratios were determined based on the results of scanning electron microscope image analysis, the filter paper test, and the temperature sweep test. The thermal and rheological behaviors of the mastics with PCMs were further evaluated with different filler replacement ratios. Thermal analysis through a differential scanning calorimetry test, thermal conductivity and volumetric heat capacity test, and real-time temperature performance test were performed on the asphalt mastics. Rheological tests, including the complex shear modulus test, the bending beam rheometer test, and the linear amplitude sweep test, were also conducted. The modified mastics were found to have high heat capacity with the latent heat storage ability. The rheological analyses showed that with the addition of polyethylene glycol, while the low-temperature performance of the asphalt mastics was improved, the performance at intermediate and high temperatures was not adversely affected by the PCM.

Effect of the Preparation Methodology of Polydopamine-Containing Systems over Light-to-Thermal Energy Conversion Performance

Polydopamine (PDA) is an attractive material utilized for a wide range of scientific purposes, including light-to-thermal energy conversion, because of presenting plenty of advantages. The proper integration way of PDA into a system is critical to benefit from the PDA content in maximum. Here, the two main PDA-containing composite preparation methods were compared in terms of fundamental material properties and the light-to-thermal energy conversion ability of the final product. For this purpose, the classical emulsion polymerization method first synthesized an aqueous dispersion of polystyrene nanoparticles (PS). PDA was then integrated into the system via two different preparation methods: coating the surfaces of polystyrene nanoparticles with a PDA layer while PS is in a dispersion state (PS@PDA) and adding separately synthesized PDA nanoparticles into the PS dispersion medium (PS–PDA). Two prepared composite systems were fundamentally characterized by dynamic light scattering (DLS), ultraviolet–visible (UV–vis) spectroscopy, and scanning electron microscopy (SEM) while in their dispersion state, and by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) while in their solid state, which was obtained after the water evaporated. As the targeted property, the solid forms of these were investigated in terms of light-to-thermal energy conversion performance with solar and laser light exposure under 1 SUN and at 808 nm, respectively. The results showed that the composite system prepared by coating surfaces of PS nanoparticles with the PDA layer had higher light-to-thermal energy conversion under both conditions than those prepared by separately added PDA nanoparticles into the dispersion system. To show one of the possible applications of the prepared composites, in addition to the main target, the solid form of the composite system, which was prepared by coating surfaces of PS nanoparticles with the PDA layer, was also evaluated in detail concerning the latent heat-storage ability with incorporation of PEG 4000 as a phase-change material (PCM) into the system. It was found that the prepared shape-stable phase-change composite with a ratio of 1:3 between PS@PDA and PEG 4000 resulted in a latent heat of 126.9 J/g.

Preparation and characterization of Kevlar nanofiber based composite phase change material with photo/electro-thermal conversion properties

To develop phase change material suitable for multi-energy complementary applications, nanofibrous Kevlar aerogel containing paraffin and then deposited with polypyrrole (PPY-KNF/PF) were fabricated. The structure, morphology and photo/electro-thermal conversion ability of PPY-KNF/PF, especially the effect of confinement on the latent heat storage capacity of composites without PPY (KNF/PF) were investigated. The results showed that PF was induced to the interface of nanofibers, then intercalated into the nanosheets during self-assembly of KNF and formed three-dimensional porous structure. The maximum latent heat of KNF/PF with PF fraction of 78.7 % is 117.2 J·g−1 without leakage. Due to the confinement effect, the actual enthalpies of KNF/PF are all lower than the theoretical latent heats, and the difference between the actual and theoretical values enlarges with the increase of PF percentage. The deposition of PPY has no effect on the structure and morphology of KNF/PF and the PPY-KNF/PF80 displays good shape stability and high latent heat storage ability (101.9 J·g−1). Moreover, the composite was endowed with multi-properties of electrothermal and active photothermal conversion, which makes it more suitable for use in the case of insufficient solar energy. This work demonstrated an effective strategy to fabricate composite PCMs with electro/photo-thermal conversion devoting to energy conversion, storage and complementary utilization.

Heat Transfer Characteristics of Modular Heat Storage Wall Solar Greenhouse Based on Active Heat Storage System

The modular heat storage wall is a new type of solar greenhouse wall structure, which has the advantages of fast construction and good heat storage ability. This study provides data reference and practical value for producing modular heat storage wall in the construction of a solar greenhouse. In this paper, we used different heat storage materials to construct the modular wall. In the winter thermal environment test, soil module solar greenhouse (SG) and stone module solar greenhouse (PG) were controlled against each other in two greenhouses. The test results for 28 consecutive days (31 January 2021 9:00 to 28 February 2021 9:00) showed that both greenhouses could effectively increase the temperature in greenhouse by 10–12 °C. The average temperature of SG was 0.86 °C lower than that of PG during the daytime (09:00–17:00) and 0.44 °C higher than that of PG during the nighttime (17:00–09:00). Under typical sunny conditions, the average temperature differences between the inlet and outlet of SG in the heat storage and exothermic stage was less than that of PG, and the relative humidity difference was greater than that of PG. This indicated that SG had a better performance of heat preservation than PG and could raise the nighttime temperature rapidly. Under the condition of a typical cloudy day, the average temperature difference between the inlet and outlet was SG < PG and the relative humidity difference was SG > PG in the exothermic stage, which was consistent with the conclusion of sunny days. In the storage and exothermic stages of typical sunny days and cloudy days, the total heat exchange of SG was 464.87, 110.44 and 54.82 MJ and the total heat exchange of PG was 264.16, 61.60 and 46.89 MJ, respectively. Moreover, the heat storage and release of SG were more than that of PG in all stages. In summary, the thermal performance of the modular heat storage wall heliogreenhouse could meet the growth of tomato crop, in which the heat transfer performance of SG was optimum.

Influence of SiC on the thermal energy transfer and storage characteristics of microwave-absorbing concrete containing magnetite and/or carbonyl iron powder

A microwave-absorbing concrete with favorable heat transfer and storage was investigated to improve the efficiency of deicing concrete pavement during microwave heating and off in cold winter. The concrete was prepared using magnetite and/or carbonyl iron powder (CIP) as the absorbing material. The effect of SiC as the heat transfer and storage material on microwave absorption efficiency, thermal conductivity and thermal diffusivity of concrete were studied. In addition, the pore structures of concrete were investigated to analyze its influence on the thermal properties of concrete.The results showed that the SiC slightly affected the microwave absorption capacity of magnetite concrete (MC) and magnetite-CIP concrete (MCC). The SiC could effectively improve heat transfer and storage ability of concrete. When the content of SiC was 7%, SiC improved the thermal conductivity and effusivity of MC and MCC were improved by 86.4% and 110%, and 84% and 97.3%, respectively. Meanwhile, adding CIP and SiC could improve the porosity and pore diameter of concrete to make it dense, which might be an influence factor to improve the thermal properties of concrete. Under the same conditions, the thermal conductivity and storage capacity of concrete showed the same change trend. In addition, the coefficient of temperature nonuniformity (CTN) and coefficient of max temperature gradient (CMTG) as new indexes was used to evaluate the influence of SiC on the thermal properties of concrete. Therefore, to improve concrete absorption of more heat during microwave heating, and transfer and store heat quickly for road deicing, the magnetite-CIP-SiC concrete (MCSC) might be the most suitable.

Performance enhancement of solar thermal systems using phase change materials- a review

This article reviews the studies carried out with respect to the area of phase change material (PCM) coupled to solar thermal systems. Solar energy is a pure form of energy which could overcome the scarcity and ecological issues of conventional energy sources, but it requires energy storage and this stored energy is supplied to the systems for later use. The solar thermal storage system can improve the performance of a solar thermal application as the solar radiation varies throughout a day. Because of their high latent heat, PCMs offer the best alternative for thermal energy storage. PCM has the capability to hold more heat per unit capacity relative to conventional storage due to its latent heat form of storage. To enable a higher saturation of renewable energy sources and fulfil the demand, one possibility is to couple them with energy storage systems. Thus, the LHS material is used due to their heat storage ability. In this review focus is given to classification of PCM, their properties and their application in solar thermal systems.

Energy performance of a rural residential building with PCM-silica aerogel sunspace in severe cold regions

Heating, Ventilation and Air Conditioning (HVAC) systems are the important component of building energy consumption (EnC), especially in the severe cold area. Enhancing heat storage capacity and solar energy efficiency are common effective measures to save energy of the buildings. Considering the low thermal conductivity of aerogel and the excellent heat storage ability of PCM (phase-change material), a sunspace for rural residential buildings using PCM walls and silica aerogel glass (PCMS-silica) to reduce indoor temperature fluctuations in cold regions was proposed. The building EnC and the temperature of PCMS-silica were compared with the existing reference sunspace (RS) and PCM wall sunspace (PCMS). Additionally, the influences of different thickness of silica aerogel layer on building EnC and indoor thermal environment (ITE) were studied. The conclusion indicates that the heating EnC of the utilization of PCMS and PCMS-silica is reduced by 10 % and 14 % respectively, compared with RS. It is concluded that 9 mm thickness of silica aerogel layer is recommended with regard to the minimal energy saving rate and maximum average indoor temperature.

Multi-timescale hierarchical scheduling of an integrated energy system considering system inertia

The multi-energy complementary property enables an integrated energy system with great potential to consume more renewable energy efficiently. However, due to the system complexity, its coordinated scheduling remains a challenge. Inertia of key inertial components must be carefully described to avoid overestimating or underestimating system flexibility, and coordinated system scheduling should be executed on multiple timescales. This paper aims to achieve coordinated scheduling of an integrated energy system, and improve its flexibility description accuracy by considering the inertia of the heat network, the combined heat and power (CHP) unit, and other key inertial components in the proposed multi-timescale scheduling method. Specifically, heat network inertia is considered to explore its heat storage ability and enlarge the operation range of an integrated energy system. To avoid overestimating CHP unit flexibility, the CHP unit ramp process is described to identify gaps between power supply and demand caused by CHP unit inertia. Besides, different temporal resolutions for inertia description are selected to match component features, whilst multiple scheduling periods are chosen to fit component regulation rates. Optimization results show that, by utilizing heat network inertia for heat storage, the daily cost and renewable energy curtailment can be reduced by 3 and 20%. Neglecting CHP unit inertia would underestimate the power output of flexible units, and the daily cost would be underestimated by 0.9%. Additionally, the proposed method can coordinate the system to handle the fluctuation and randomness of renewable energy, reducing the daily cost by 4%.

A mini review on paraffin‐graphene and related hybrid phase change materials for building energy applications

AbstractThe thermal energy management in building is gaining the significant attention in the present energy scenario to manage the temperature. Graphene‐related additives are known for their exceptional properties viz. excellent binding and high intrinsic thermal conductivity. The hybrid phase change materials (PCMs) with graphene additives have been applied to enhance the thermal conductivity. Graphene‐related materials are drastically used to improve the properties of PCMs. Incorporating graphene‐related fillers increase the thermal conductivity and preserve the latent heat storage ability of hydrocarbon‐based PCMs. Also, graphene‐related fillers can prevent the leaching properties of the PCMs. These composites can ease concerns regarding energy demand to some level by reversibly storing an incredible quantity of renewable as well as sustainable thermal energy helping to keep up thermal comfort and this has motivated authors to write present mini review. In this review, authors have described PCMs, preparation methods, graphene, graphene oxide, and their composite related PCMs, nanographene added PCMs and their applications in building envelopes utilizing graphene and relative additives.

Investigation of physico-mechanical, thermal properties and solar thermoregulation performance of shape-stable attapulgite based composite phase change material in foam concrete

Thermal energy storage (TES) by means of phase change materials (PCM) is of great concern to decrease heating and cooling loads. In building envelopes, one of the most efficient TES methods is integration of PCMs with construction materials for preventing temperature fluctuations by taking advantage of energy storage/release feature of PCMs. Aim of this research was to develop novel foam concretes containing shape-stable attapulgite (ATP) based composite PCM as TES material. Shape-stable ATP/Capric-Myristic acid eutectic mix composite (ATP/C-M) was incorporated into foam concrete at three different ratios (15, 30 and 45 wt%) and characterized. Impacts of ATP/C-M inclusion on physico-mechanic and TES characteristics of foam concretes including composite PCM (FCPCM) were worked systematically. DSC results showed that ATP/C-M composite melts at 22.12 °C with latent heat storage capacity of 74.97 J/g, whereas FCPCM-45 melts at 21.05 °C with latent heat storage ability of 10.98 J/g. Inclusion of ATP/C-M instead of silica sand decreased flow diameter of foam concretes. Compared to reference mixture FCPCM-0, compressive strengths of FCPCM-15, FCPCM-30 and FCPCM-45 samples were reduced in the range of 11–46% while reduction in flexural strength was found to be about 35–57% at 28th day. All FCPCM samples showed lower thermal conductivity values than the specified value and could be defined as better insulation materials. Solar thermoregulation performances of foam concretes containing ATP/C-M were comparatively tested in laboratory and also actual ambient conditions. Results showed that foam concretes with acceptable mechanical properties can be used for internal temperature controlling and energy saving in buildings.

Novel composite phase change material of high heat storage and photothermal conversion ability

Using porous matrix as the supports for phase change materials (PCMs) can effectively eliminate the leakage problem of PCMs during the phase change process. In heat storage utilization, the as-prepared shape-stabilized phase change materials are highly desired to have high latent heat density, rapid heat transfer ability and less supercooling. Although mesoporous silica with large pore volume and specific surface area might be a promising matrix for PCMs, it would be more beneficial if its thermal conductivity and photo-thermal conversion capacity were further improved, especially for the utilization of solar thermal energy. Herein, a composite PCM, namely SA/CNTs@MS, was fabricated successfully using mesoporous silica coated carbon nanotubes (CNTs@MS) as the shape-stabilized matrix for the PCM stearic acid (SA). The results of characterizations showed that CNTs@MS had a core-shell structure with mesoporous silica of a thickness of about 30 nm coated on the outer surface of carbon tubes (CNTs) homogeneously. The melting enthalpy of the obtained SA/CNTs@MS composite was 125.6 J/g. Its thermal conductivity increased 64.7%, and the supercooling degree decreased 3.2 ℃ while compared with those of pure SA. The melting and solidification enthalpies of SA/CNTs@MS decreased 1.1% and 1.3%, respectively after 200 thermal cycles. Besides, it is also confirmed that SA/CNTs@MS had good photo-thermal conversion performance. These imply that the synthesized SA/CNTs@MS composite would be an ideal heat storage material, especially for solar energy utilization.

Biomass-based shape-stable phase change materials supported by garlic peel-derived porous carbon for thermal energy storage

Phase change materials with low cost, good thermal stability, and excellent shape stability are urgent in energy storage. Herein, a novel shape-stable phase-change material (SSPCM) for thermal energy storage is developed based on activated garlic peel (AGP), derived from widespread and cheap garlic peels. The paraffin (PA)/AGP composite PCM is prepared via vacuum impregnation method. The scanning electron microscope results show that AGP has many grooves, and the pores of AGP are filled by paraffin wax. The specific surface area of AGP is up to 1309 m2/g. The phase change enthalpy in the melting and freezing process is 52.5 J/g and 51.9 J/g, respectively. Moreover, the prepared SSPCM exhibits satisfied shape stability, thermal stability, and waste heat storage ability. Also, the SSPCM has a low latent heat loss rate of about 1.5% after 200 thermal cycles. This work provides an economical and environmental method for synthesizing shape-stabilized phase-change materials based on biomass materials with potential applications in waste heat recovery and recycling.