Latent Heat Storage Capacity Research Articles

Analysis of Heat Transfer and Natural Convective of a Phase Change Material

A phase-change material (PCM) is a substance with a high latent heat storage capacity which on melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. Various PCM like Paraffin wax, stearic acid are considered which are used to absorb heat from the coolant water from the engine. The conduction and convection criterion of heat transfer enable the PCM to store this heat as latent heat. The amount of convection and temperature change brought about due to the heat flux has been simulated and studied in detail using FLUENT. The thermal energy storage device (TESD) works on the effect of absorption and rejection of heat during the solid-liquid phase change of heat storage material. The overall function of the TESS is dominated by the PCM. The PCM material should be selected considering the application and the working conditions. Depending on the applications, the PCMs should first be selected based on their melting temperature for heat recovery system.

Microencapsulating n-docosane phase change material into CaCO3/Fe3O4 composites for high-efficient utilization of solar photothermal energy

Microencapsulating phase-change materials (PCMs) into CaCO3 shell is considered as an effective way to resolve the leakage problem of the microcapsule system and enhance its heat transfer. Herein, we designed and fabricated a type of phase-change microcapsule system based on an n-docosane core and CaCO3/Fe3O4 composite shell using a nonaqueous emulsion-templated self-assembly technology for enhancing solar photothermal energy absorption, conversion and storage performance. The type and addition amount of templating agent and the mass ratio of PCM core to wall material play key roles in the formation of microcapsules with a controllable spherical or rhombohedral morphology and a perfect core-shell microstructure. The resultant phase-change microcapsules show a satisfactory latent heat-storage capacity of around 140 J/g, high encapsulation ratio of over 59%, high thermal conductivity of 0.795 W m−1 K−1, excellent leakage prevention capability and good thermal cycle stability when synthesized under the optimum synthetic condition. More importantly, the phase-change microcapsules exhibit a significant enhancement in solar photothermal conversion and storage performance due to the presence of Fe3O4 nanoparticles in their shell, and their photothermal conversion efficiency was improved by 47.9% compared to the corresponding microcapsules without Fe3O4. In conclusion, the phase-change microcapsules developed in this work show considerable potential in high-efficient solar energy utilization.

Surface construction of Ni(OH)2 nanoflowers on phase-change microcapsules for enhancement of heat transfer and thermal response

A phase-change microcapsule system based on an n-docosane core and SiO2/nanostructural Ni(OH)2 layer-by-layer shell was designed with the aim to enhance the heat transfer and thermal response capability of phase-change microcapsules. This system was fabricated through emulsion-templated interfacial polycondensation to form a SiO2/n-docosane microcapsule system, followed by anchoring Ni(OH)2 nanoflowers on the surface of the SiO2 shell via structure-directed interfacial precipitation. The resultant microcapsule system achieved a satisfactory latent heat-storage capacity of around 130 J/g with high energy-storage efficiency over 99%. Compared to conventional SiO2/n-docosane phase-change microcapsules, this microcapsule system not only presents high thermal conductivity, rapid heat transfer rate, good leakage prevention capability, high heat charging-discharging stability, but also exhibits a good phase-change reversibility and resilience ability to perform repetitious solid-liquid phase transformations. The combination of traditional phase-change microcapsules with a nanostructural Ni(OH)2 outer layer results in a significant enhancement in heat transfer, which makes the system a fast thermal response ability to satisfy a variety of applications where fast and stable thermal energy storage/release is required. Through constructing the Ni(OH)2 nanoflowers on the surface of conventional phase-change microcapsules, this study offers a promising strategy for the design and fabrication of high-performance phase-change microcapsules with fast thermal response.

Improvement in thermal properties of PCM/Expanded vermiculite/expanded graphite shape stabilized composite PCM for building energy applications

This work investigates the combined effect of loading Expanded Graphite (EG) and Expanded Vermiculite (EV) on the thermophysical properties of the low-cost commercially available PCM (OM37) and there capability of regulating the indoor temperature when embedded in the building element. Shape Stabilized Composite Phase Change Material (ss-CPCM) was prepared using PCM, EV, and EG through physical blending followed by vacuum impregnation. Latent heat storage capacity, phase change parameters, melting and freezing response, thermal stability, thermal reliability, and leakage proof performance was investigated. Melting enthalpy of 114.23 J/g, 111.56 J/g, 105.08 J/g, and 99.32 J/g at melting temperature of 40.61 °C, 39.12 °C, 38.83 °C, and 37.41 °C was obtained for ss-CPCM-1, 3, 5, and 7 respectively. A rise of 114.4% in the thermal conductivity was observed by adding 7 wt% of EG in ss-CPCM. ss-CPCM loaded with 7 wt% of EG heats 25.9% faster and cools 19.2% faster in comparison to pristine PCM. The prepared ss-CPCM preserves its thermal characteristics even after 1000 heating and cooling cycles. Moreover, when embedded in the wallboard, the ss-CPCM-7 has shown the excellent capability of regulating indoor temperature.

High internal phase emulsion templated-polystyrene/carbon nano fiber/hexadecanol composites phase change materials for thermal management applications

Porous high internal phase emulsion templated polymers (PHPs) with/without carbon nanofiber (CNF) frameworks were synthesized for shape-stabilization of hexadecanol (HD) selected as phase change material (PCM) for thermal energy storage (TES) applications. This impregnation process was resulted in creation of seepage-free composite PCMs with high latent heat storage (LHS) capacity and enhanced thermal conductivity. Morphology, chemical structure, LHS properties and thermal stability of prepared composites were characterized by SEM, FT-IR, DSC and TGA techniques. DSC analysis indicated that the PHP/HD and PHP@CNF/HD(80wt%) composites have a LHS capacity of over 200 J/g at about 46–47 °C. The cycled-composite PCMs showed outstanding thermal reliability and chemical stability. Thermal decomposition temperature of HD was considerably extended after impregnation with PHP and PHP/CNF scaffolds. Thermal conductivity of PHP/HD and PHP@CNF/HD was enhanced compared to that of pure HD. The reduction in heat storing/releasing times of PHP@CNF/HD composites relative to PHP/HD composite was proved by considering the measured temperature-time change. Accordingly, especially PHP@CNF/HD composites PCMs have promising prospective for medium temperature-TES practices.

Li4(OH)3Br-Based Shape Stabilized Composites for High-Temperature TES Applications: Selection of the Most Convenient Supporting Material.

Peritectic compound Li4(OH)3Br has been recently proposed as phase change material (PCM) for thermal energy storage (TES) applications at approx. 300 °C Compared to competitor PCM materials (e.g., sodium nitrate), the main assets of this compound are high volumetric latent heat storage capacity (>140 kWh/m3) and very low volume changes (<3%) during peritectic reaction and melting. The objective of the present work was to find proper supporting materials able to shape stabilize Li4(OH)3Br during the formation of the melt and after its complete melting, avoiding any leakage and thus obtaining a composite apparently always in the solid state during the charge and discharge of the TES material. Micro-nanoparticles of MgO, Fe2O3, CuO, SiO2 and Al2O3 have been considered as candidate supporting materials combined with the cold-compression route for shape-stabilized composites preparation. The work carried out allowed for the identification of the most promising composite based on MgO nanoparticles through a deep experimental analysis and characterization, including chemical compatibility tests, anti-leakage performance evaluation, structural and thermodynamic properties analysis and preliminary cycling stability study.

Thermally-stable, solid-solid phase change materials based on dynamic metal-ligand coordination for efficient thermal energy storage

• A novel SSPCM based on dynamic metal-ligand bonds was successfully prepared. • The devised DS-PCMs can be reprocessed in two simple and convenient ways. • The DS-PCMs have superior energy storage ability and thermoplastic performance. Thermal energy storage offers enormous potential for the development of modern energy technologies. Solid-solid phase-change materials (SSPCMs) have drawn great attention due to their efficient energy utilization and excellent thermal stability. However, it is still a challenge to synthesize SSPCMs capable of the intriguing properties of reprocessability and recyclability. Herein, we reported an effective strategy to construct dynamic cross-linked SSPCMs, namely DS-PCMs, through incorporating reversible metal-ligand coordination. The synthesized DS-PCMs can keep in a solid state during the phase change process with a high latent heat storage capacity of up to 99.3 J/g. Especially, the energy storage capacity, chemical structure and thermal stability of the reprocessed DS-PCMs can be consistent with that of original one after being reprocessed by hot pressing and ultrasound-assisted water solution casting. Additionally, these DS-PCMs have repeatable thermo-plasticity to manipulate permanent various 3D shapes without complex molds. Briefly, these designed DS-PCMs simultaneously have excellent stability, dual reprocessability, and reconfigurable thermoplastic performance. Our works provide a facile design strategy to prepare reprocessable SSPCMs, unlocking opportunities for the sustainable use of phase change materials.

Effects of Phase Change Materials on heat flows through double skin facades

The potential of exemplary organic and inorganic Phase Change Materials (PCMs) as facade integratedstorage is tested. The impact of two PCMs on heat flows is assessed in comparison with water andconcrete. The simulation-study employs a transient Modelica simulation model of a test cell featuringthe Solar Energy Balanced Facade (SEBF). It is shown that, when compared to water, PCMs of identicalvolume change the seasonal energy balance in winter and summer by only ± 4%. Other than water,the PCMs maintain this effect even if the storage volume decreases. Due to spatial constraints, thiscan support the integration of thermal storage in facade design considerably. Preliminary resultsindicate that designing thermal storage in facades with PCMs must not only consider the latent heatstorage capacity, but also take into account the combined effects of latent heat capacity, meltingpoint, conductivity, and dead load. The application of PCMs promises to foster the integration of thetechnology of SEBF into facades, but the necessary deliberate selection of, and design with, PCMsrequires further research.

Application of Machine Learning (ML) for Enhancing the Transient Performance of Thermal Energy Storage (TES) Platforms Using Radial Basis Function (RBF)

Thermal energy storage (TES) can be utilized as supplemental platforms for improving operational reliability and systemic efficiency in variety of industries, such as for reducing water usage in power production (food-energy-water/ FEW nexus), chemical and agro-process industries and for improving sustainability (e.g., desalination), etc. Phase change materials (PCMs) can be used in TES due to their high latent heat storage capacity during phase transformation. Inorganic PCMs typically have the highest latent heat capacity and are attractive for their ability to store the larger quantities of thermal energy in small form factors while conferring respectable power ratings (however, they suffer from compromised reliability issues, that often arise from the need for subcooling). Subcooling (also known as supercooling) is a phenomenon where the temperature needs to be reduced substantially below the melting point to initiate solidification. A technique for obviating subcooling issues is to allow a small portion of the PCM to remain un-melted. This allows the PCM to initiate nucleation from the un-melted portion of PCM (this is termed as the “cold finger” technique). Thus, reliability is enhanced at the expense of substantial reduction in storage capacity. A fundamental challenge for using this technique is the inability to reliably predict and control the amount of melt fraction in the total volume of the PCM (such that a target amount of the PCM remains solidified or un-melted at the end of each melt-cycle during repeated melting and solidification of the total mass of PCM). However, using Machine Learning (ML) techniques, this deficiency can be addressed by reliably predicting and thus controlling the amount of melt fraction in the total volume of the PCM with a higher accuracy than conventional techniques (such as using multi-physics-based models or numerical solvers). Conventional techniques for predicting transient characteristics in real time control schemes typically leverage multi-physics-based models that are often effective only for a narrow range of operating conditions with concomitant disadvantages: they are highly sensitive to small variations in the measurement uncertainties and are therefore susceptible to large levels of error in the real time predictions (and are unreliable for implementation in diverse range of operating conditions). In this pioneering study, nearest neighbor search processes (such as radial basis functions) were utilized along with machine learning (ML) algorithm using a training data set to predict the PCM melt fraction and to demonstrate the feasibility (and efficacy) of this approach. This technique is simple to implement and is device independent as well as robust (i.e., it can be deployed successfully even under conditions where the sensors malfunction, such as thermocouples that are off-calibration). This technique was demonstrated successfully for predicting the melt fraction of a PCM with high accuracy and robustness. With this method, the melt fraction of a PCM can be accurately determined, which allows the maximum thermal capacity of a PCM to be utilized while mitigating reliability issues (such as subcooling) and enhancing the thermodynamic efficiencies of the TES platforms. Melting experiments were performed using a digital camera (for video recording) and a graduated cylinder containing PCM for monitoring the transient values of the melt fraction based on the height of the liquid phase of the PCM in the cylinder. An array of 3 thermocouples was mounted at specific heights within the body of the PCM to monitor the temperature transients at these specific location during the propagation of the melt front within the PCM. In the final stages of the melting process, the predictions from the ML algorithm was found to be more accurate (90~95% accuracy) than that of the conventional techniques based on physics-based solvers (~60% accuracy). The accuracy of the ML algorithm was low at smaller melt fractions (~30%) and improved substantially at higher melt fractions (~95%). Furthermore, the accomplishments of this study display the feasibility of a RBF ML method which can be implemented for the accurate prediction and control of a real world stochastic system which can exhibit nonlinear and chaotic dynamics which change over time.

Azelaic Acid/Expanded Graphite Composites with High Latent Heat Storage Capacity and Thermal Conductivity at Medium Temperature.

A novel azelaic acid/expanded graphite (AA/EG) phase change composite (PCC) was fabricated as a shape-stabilized phase change material (PCM) for latent heat storage at medium temperatures. The composite exhibited a low supercooling degree and high heat storage capacity. Despite the impregnation of a high quantity of AA (85 wt %) in the porous network of EG, there was no leakage of liquid AA. This was attributed to the capillary forces and surface tension forces. The pure AA exhibited a melting temperature of 108.0 °C, with an intrinsically low supercooling degree of 5.8 °C. The melting temperature of AA in the PCC decreased slightly to 105.8 °C, and there was a significant decrease in the supercooling degree to 1.0 °C. The AA/EG PCC exhibited a high latent heat storage capacity of 162.5 J/g, and there was a significant gap between the decomposition temperature and the phase change temperature range. Therefore, the composite exhibited high thermal stability during operations. The results of an accelerated thermal cycling test (200 cycles) indicated the high cycling durability and chemical stability of the PCC. The thermal conductivity of AA increased by 15.7 times after impregnation in EG, as compared to that of the pure AA, and thus, thermal kinetics of the PCC was improved. The results of a heat storage/release test with 15 g of the PCM revealed that the melting and solidification of the AA/EG PCC were 5.0-fold and 7.4-fold faster, respectively, than those of the pure AA. This was attributed to the high thermal conductivity of the PCC.

N-Octadecane/Fumed Silica Phase Change Composite as Building Envelope for High Energy Efficiency.

A novel n-octadecane/fumed silica phase change composite has been prepared as a building envelope with a high content of phase change material and improved energy efficiency. With a high porosity (88 vol%), the fumed silica provided sufficient space to impregnate a high quantity of n-octadecane (70 wt%). The composite exhibited high latent heat storage capacity (155.8 J/g), high crystallization fraction (96.5%), and a melting temperature of 26.76 °C close to that of pure n-octadecane. A 200 accelerated thermal cycle test confirmed good thermal reliability and chemical stability of the phase change composite. The thermal conductivity of n-octadecane was reduced by 34% after impregnation in fumed silica. A phase change composite panel was fabricated and compared to a commercial polystyrene foam panel. When used as the roof of a test room, the phase change composite panel more efficiently retarded heat transfer from a halogen lamp to the room and delayed the increase in the indoor temperature than that by the polystyrene panel. The indoor temperatures of the room with the phase change composite panel roof were 19.8 and 22.9 °C, while those with the polystyrene panel roof were 29.9 and 31.9 °C at 2200 and 9000 s after lamp illumination.

Introduction of eicosane into biochar derived from softwood and wheat straw: Influence of porous structure and surface chemistry

Thermal energy storage using phase change materials (PCMs) has received great attention in a wide range of smart applications. However, the development of shape-stabilized organic composite PCMs is a significant barrier to further advancement. Herein we explore “green” composite PCMs using commercially available biochar materials, derived from two different biomaterials, wheat straw and softwood, at pyrolysis temperatures of 550 °C and 700 °C, and organic PCM, n-eicosane (ES), for efficient thermal energy storage applications. All the composite PCMs exhibited high thermal stability, medium thermal diffusivity, and good chemical compatibility with the composite constituents. Over the phase change temperature range 36.4–40.6 °C, the composite derived from wheat straw biochar pyrolyzed at 550 °C showed the largest latent heat storage capacity of 75.0 J/g due to the high mesopore content of its supporting structure, specific surface area, and active functional groups that enhance the capillary force during PCM adsorption. In contrast, softwood biochar produced at 550 °C had the lowest latent heat storage capacity of 52.0 J/g. The surface functionality, structural characteristics, type of biomaterials, intermolecular interaction between ES and biochars, and pyrolysis temperature play important roles in determining the thermal properties of the as-prepared composite samples.

A comparative analysis of biochar, activated carbon, expanded graphite, and multi-walled carbon nanotubes with respect to PCM loading and energy-storage capacities

To obtain high thermal performance composite phase change materials (PCMs), various other supporting materials have been utilized to encapsulate organic PCMs. In this study, four carbon materials (biochar, activated carbon, carbon nanotubes, and expanded graphite) were introduced to support heptadecane. The composite PCMs were designed using vacuum impregnation techniques. The structural stability, chemical compatibility, thermal stability, and thermal energy storage capacity of the as-prepared materials were systematically characterized using differential scanning calorimetry, Fourier-transform infrared spectroscopy, etc. Among the supporting materials, expanded graphite had a high PCM content of 94.5%, whereas it was low for biochar-supported PCM (25.7%). Meanwhile, the latent heat storage capacity ranged from 53.3 J/g to 195.9 J/g. It was observed that the intermolecular interactions between the PCM and supporting materials and the surface functionality of the encapsulating agents play a leading role in the thermal performance of the composite PCMs. Furthermore, pore structures such as specific surface area, total pore volume, and pore size distribution have a combined effect on the crystallinity of heptadecane in the composite PCMs. The study will provide insight into developing and designing carbon-based composite PCMs for heat-storage purposes.

Multifunctional composites silicone rubber/paraffin@lead tungstate with different core/shell ratio for thermal regulation and gamma shielding

Multifunctional, high-comfort flexible radiation protection materials are highly desired for future human health-related applications but generally hindered due to the single function, poor heat dissipation performance. Herein, a new type of flexible radiation protection shielding materials with thermal regulation function was prepared with silicone rubber (SR) as matrix and paraffin(Pn)@lead tungstate(PWO) phase change microcapsules as fillers. The effect of different core/shell ratio of microcapsules on the properties of flexible radiation protection shielding materials was discussed. The obtained flexible radiation protection material not only shows high latent heat storage capacity, but also includes excellent phase change reversibility and long-term durability. Through the programmed DSC scanning, the thermal charging and discharging behavior of the composites in the thermal management process was optimized. The thermal regulation experiment of the composites show a good temperature regulation ability. Compared with SR, the mechanical properties and gamma ray shielding ability of SR/(Pn@PWO) composites are greatly improved, and the enhancement effect is more obvious with core/shell ratio of the microcapsules decreases. The gamma ray shielding ability of SR/(Pn@PWO) composites is 144.05% higher than that of SR. This work provides a new perspective for the design and development of high comfort radiation protection products, and broadens the application prospects of radiation protection materials.

Microencapsulated heptadecane with calcium carbonate as thermal conductivity-enhanced phase change material for thermal energy storage

Heptadecane (HD) is a useful solid–liquid phase change material (PCM) because of its good thermal energy storage (TES) properties. However, leakage problems throughout the phase change and its relatively low thermal conductivity have significantly restricted its TES utility areas. Simultaneously, to prevent leakage and increase its thermal conductivity, HD was successfully encapsulated in a micro CaCO3 shell via a self-assembly mechanism. Fourier Transform Infrared (FTIR) analysis determined the chemical structures of the microcapsule's components. X-ray Powder Diffraction (XRD) results confirmed that the crystalline structures of both the HD core and CaCO3 shell were not impacted during the microencapsulation process. The SEM microstructures showed that the microcapsules had well-defined spherical morphology. Differential Scanning Calorimetry (DSC) measurements revealed that the HD within the capsule had a latent heat storage capacity in the range of 86–147 J/g when it melts and solidifies at around 16 °C. The 1000-times-cycled microcapsules demonstrated remarkable chemical stability and TES dependability. Thermogravimetry (TG) analysis showed that the microcapsules had excellent thermal degradation durability. All the produced microcapsules had greater thermal conductivity than the pure HD. The heat storage and releasing periods of the microcapsules were considerably reduced because of their enhanced thermal conductivity. The results revealed that the synthesised HD@CaCO3 microcapsules can be evaluated in different TES applications, such as the air conditioning of buildings, thermal management of textiles and thermal preservation of foods.

Numerical investigation on latent heat thermal energy storage in a phase change material using a heat exchanger

AbstractThe use of a heat exchanger using phase change material (PCM) is an example of latent heat thermal energy storage (LHTES). In this study, the charging of PCM (RT50) is studied in a double pipe heat exchanger. The designing of the heat exchanger needs to be optimized for operating and boundary conditions to store latent heat efficiently. The size of the equipment and the amount of PCM are also important to calculate the latent heat storage capacity of the LHTES device. In this study, the amount of PCM taken is quite high to avoid sensible heat transfer and to maximize the heat content of PCM. The charging process of PCM is numerically simulated using an enthalpy‐porosity model. The study includes the effect of inlet temperature and flow rate of high‐temperature‐fluid (HTF) and concludes that both play an important role in determining the charging time. The continuous increase in inlet temperature of HTF can decrease the charging time of PCM in the heat exchanger. However, the continuous increase in the HTF flow rate cannot show the same effect. The charging time can only be minimized with a specified flow rate regime for a specific inlet temperature of HTF. These factors consequently affect the efficiency of the heat exchanger.

Form‐stable phase‐change materials supported by 1‐octadecylamine‐modified montmorillonite for latent heat storage

Form-stable phase-change materials (FSPCMs) are of great significance for relieving the contradiction of energy supply and demand. Unfortunately, the practical application of FSPCMs is severely compromised by their intrinsic drawbacks including lower latent heat storage (LHS) capacities, inferior interfacial compatibility, and cycling durability. Herein, we have provided a group of novel FSPCMs with higher LHS capacities, using paraffin as the LHS materials, which tightly intertwines with the 1-octadecylamine-modified montmorillonite (C18-MMT) under the capillary action as well as induced dipole force due to its n-alkyl chains compatibility. The obtained composite FSPCMs not only exhibit high melting enthalpies (137.56 J/g) but also demonstrate enhanced shape stability and thermal stability. In addition, the composites also render an impressive long-term thermal cycling capability and structure stability even after 100 thermal cycling durability tests, which are believed to have great potential for application in the thermal management of green energy-saving buildings.

Latent heat storage capacity of NiTi shape memory alloy

The largest amount of latent heat of the martensitic transformation in nickel titanium shape memory alloy was explored. The measured amounts of heat in the alloys with different compositions between 48.0 at.% Ni and 51.0 at.% Ni were compared. The largest amounts of \(-\) 37.8 J/g in absorption and 34.8 J/g in emission were obtained as the averaged values of several samples with equiatomic composition. These magnitudes are close to those of novel heat storage ceramics, VO2 (51 J/g) and Ti3O5 (60 J/g), suggesting the NiTi alloy is potential candidate for heat storage material.Graphical abstract

Fabrication and characterization of a novel polyurethane microencapsulated phase change material for thermal energy storage

Microencapsulated phase change materials (MEPCMs) can efficiently prevent the leakage and erosion of melting phase change materials during phase change process, which exhibit a bright industrial application prospect in the fields of thermal energy storage. Herein, a novel polyurethane (PU) microencapsulated methyl laurate was successfully fabricated via interfacial polymerization. The preparation conditions of PU-based MEPCMs were comprehensively explored, offering a systematic guidance for the tailored design of novel MEPCMs. And the experimental results indicate that the obtained PU-based MEPCMs have high latent heat storage capacity. Specially, when the core/shell mass ratio is 3:1, the melting enthalpies, freezing enthalpies, and core contents of MEPCMs reach as high as 136.2 J/g, 121.2 J/g and 75.18 %, respectively. Meantime, the resulting PU-based MEPCMs also present excellent thermal reliability and storage stability. The development of novel PU-based MEPCMs may open up a new opportunity for their wider applications in the thermal energy storage fields such as architectural coatings, refrigerated storage, and functional thermal fluids.

Engineering biochar with multiwalled carbon nanotube for efficient phase change material encapsulation and thermal energy storage

Currently, numerous efforts are being made to develop shape-stabilized composite phase change materials (PCMs) to respond to unbalanced renewable energy storage systems. In this study, we engineered hybrid materials based on commercially available and environmentally friendly biochar derived from bamboo and multiwalled carbon nanotubes (CNTs) via a one-step hydrothermal method. The organic liquid n-dodecane was used as the energy storage material. The hybrid material provides favorable morphological and interconnected framework structures for PCM encapsulation and energy storage capacity in the composite PCMs. The PCM loading capacity of biochar, biochar-CNT, and CNTs reached 51.3%, 70.6%, and 83.2% with latent heat of 93.4 ± 1.1, 127.3 ± 1.1, and 152.3 ± 1.3 J/g, respectively. The integration of CNTs with biochar positively affected the latent heat storage capacity of the composite PCMs compared with that of the composite PCMs without CNTs. The pristine biochar exhibited a low PCM loading ratio and latent heat compared with biochar-CNTs and CNTs, presumably due to the limited pore space and strong intermolecular interaction between the reactive functional groups and PCM. Meanwhile, the obtained composite PCMs exhibited outstanding shape and thermal stabilities and chemical compatibilities. This synthesis strategy is expected to create a platform for fabricating biochar-based multifunctional PCMs for desired applications.