Phase Change Materials For Energy Storage Research Articles

Self-assembled boron nitride nanosheet-based aerogels as support frameworks for efficient thermal energy storage phase change materials.

Phase change materials (PCMs) are promising in many fields related to energy utilization and thermal management. However, the low thermal conductivity and poor shape stability of PCMs restrict their direct thermal energy conversion and storage. The desired properties for PCMs are not only high thermal conductivity and excellent shape stability, but also high latent heat retention. In this study, the boron nitride nanosheets (BNNSs) were bridged by small amounts of GO nanosheets and successfully self-assembled into BNNS/rGO (BG) aerogels by hydrothermal and freeze-drying processes. The BG aerogels with interlaced macro-/micro-pores have been proven to be ideally suited as support frameworks for encapsulating polyethylene glycol (PEG). The obtained composite PCMs exhibit high thermal conductivity (up to 1.12 W m-1 K-1), excellent shape stability (maintain at 90 °C for 10 min), and high latent heat (187.2 J g-1) with a retention of 97.3% of the pure PEG, presenting great potential applications in energy storage systems and thermal management of electronic devices.

A TREE-SHAPED LAYOUT HEAT PIPE TO ENHANCE HEAT TRANSFER IN A PHASE-CHANGE MATERIAL STORAGE PROCESS

Phase-change materials (PCMs) are promising in energy storage. However, the low thermal conductivity of a PCM limits its practical application. A tree-shaped layout heat pipe has been studied in this paper to improve the heat transfer performance in PCM energy storage. Based on the thermal imaging picture distribution of conventional heat pipes within the PCM during the heat storage process, tree-shaped layout heat pipes have been designed. Additionally, their thermal performance was experimentally compared with that of conventional heat pipes. Experimental results prove that the bending of heat pipes has little influence on its own thermal performance, and the difference in average temperature between tree-shaped layout and conventional heat pipes is 0.9%. A PCM containing such tree-shaped layout heat pipes melts 15.2% faster than a PCM with conventional heat pipes. The thermal resistance of a PCM with these tree-shaped layout heat pipes decreases by 41.7% compared with that of a PCM with conventional heat pipes. Moreover, tree-shaped layout heat pipes reduce the thermal resistance of the PCM mainly before phase change in the melting process, while this layout has less impact after the completion of melting.

Self-luminous, shape-stabilized porous ethyl cellulose phase-change materials for thermal and light energy storage

Self-luminous, shape-stabilized porous ethyl cellulose phase-change materials for thermal and light energy storage

Analysis of indirect solar dryer with PCM energy storage material: Energy, economic, drying and optimization

As the food processing industry needs a lot of heat energy to remove moisture from agricultural products, there is a greater emphasis on solar energy. In this study, the energy analysis and economic feasibility of Indirect Solar Dryer (ISD) comprises a blower, three different corrugated absorber plate solar collector setups (without Phase Change Material Energy Storage (PCMES), with PCMES, and with fins inserted PCMES). The drying time of the bitter gourd slices in the developed ISD setup is significantly decreased compared to natural drying. The Weibull model is selected as the best mathematical model for predicting drying behavior based on statistical variables. The ISD’s energy analysis reported the thermal efficiencies, energy consumption, and moisture extraction rate. The ISD with fins inserted PCMES performed better than the other two setups in energy performances. However, because of the usage of fins, the same setup has a slightly higher (3.1%) capital cost than the setup without fins. ISD with fins inserted PCMES is chosen as the best setup based on energy and economic parameters from the multiple criteria decision-making techniques. The selected setup produced a robust and high-quality product; and, thus, recommended for drying agricultural products in food drying industries.

Phase Change Energy Storage Material with Photocuring, Photothermal Conversion, and Self-Cleaning Performance via a Two-Layer Structure.

Compared with the thermal curing process, the photocuring process has advantages such as high efficiency and less energy consumption. However, the preparation of photocurable phase change materials (PCMs) with photothermal conversion and self-cleaning properties is challenging due to the conflict between the transparency required by the photocurable resin system and the opacity deduced by the large number of fillers required by photothermal conversion and the negative effect of filler steric hindrance on the reaction rate and crystallinity. In this work, a "thiol-ene" click chemical reaction induced using UV was used to prepare photocurable PCMs, followed by spraying a carboxylated multiwalled carbon nanotube (CCNT) suspension (with ethyl acetate) onto the surface to achieve an effective two-layer composite of the PCM and CCNTs, by which the rough surface of the PCM and the interaction offered by the hydrogen bonds on the interface of the PCM and the CCNTs provide sufficient adhesion for the two phases. The "thiol-ene" cross-linked polymer network provided shape stability as a support material. 1-Octadectanethiol (ODT) and beeswax (BW) were encapsulated in the cross-linked polymer network as phase change components, providing phase change latent heat. The CCNT layer provided excellent photothermal conversion and self-cleaning properties. The experimental results show that the latent heat of the PCM can reach 124.2 J/g, the water contact angle is 144°, the photothermal conversion efficiency reaches 75%, and it has significant self-cleaning performance. To the best of our knowledge, this is the first report on a photocurable PCM with photothermal conversion and self-cleaning properties.

Scaphium scaphigerum/graphene hybrid aerogel for composite phase change material with high phase change enthalpy and high thermal conductivity for energy storage

Based on the disadvantages of the low thermal conductivity and easy leakage of the organic phase change energy storage material, Scaphium scaphigerum/graphene hybrid aerogel (SGA) with sparse porous structure was prepared by the template method and used as a thermally conductive reinforcing material to fabricate PEG forming composite PCMs of SGA/PEG. The results show that the three-dimensional pore structure of the SGA is composed of extremely thin graphene sheets interwoven and connected to each other. The EDA reducing agent can effectively remove the oxygen-containing functional groups, allowing the graphene sheets to re-adhere to the SC soft stencil and continuously aggregate, stack and self-assemble, resulting in thermally stable SGA. DSC result shows SGA/PEG composite has excellent overall thermal performance, especially SGA/PEG-8 with a latent thermal storage energy of 166.11 J/g, which is 99.35 % of that of pure PEG, and remains 99.20 % even after 100 heating-cooling cycles. The XRD, FT-IR and Raman spectroscopy results show that there is no chemical reaction in the SGA composite with PEG and that it is physically bonded. The TGA results show that the SGA can effectively conduct heat from the surface of the sample, showing a beneficial effect on the thermal stability of the composite. The SEM results directly demonstrate that the three-dimensional pore structure of the SGA is uniformly wrapped by PEG and that the surface of the lamellae is relatively smooth, without any significant accumulation of PEG. Furthermore, the shape-stable SGA/PEG exhibited a high thermal conductivity of 1.0621 W/(m K) which was enhanced to 378 % relative to pure PEG. This novel strategy offers enlightening prospects for the preparation of composite phase change materials with good thermal storage properties, thermal conductivity and thermal stability for a wide range of applications in energy storage.

Preparation and characterization of steel slag-based low, medium, and high-temperature composite phase change energy storage materials

In this study, industrial solid waste steel slag was used as supporting material for the first time, and polyethylene glycol (PEG), sodium nitrate (NaNO3), and sodium sulfate (Na2SO4) were used as low, medium, and high-temperature phase change materials (PCMs). A series of shape-stable composite phase change materials (C-PCMs) were prepared by vacuum impregnation and mixing-sintering methods. The morphology, thermal properties, and thermal reliability of C-PCMs were characterized by scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR), and differential scanning calorimetry (DSC). The results show that the three PCMs are uniformly dispersed in the pores of steel slag, and the maximum loading is 35 %, 40 %, and 50 %, respectively, and they have good chemical compatibility with steel slag. Compared with their pure PCMs, the three prepared C-PCMs showed a reduction in subcooling of 2.64 °C, 4.53 °C and 0.79 °C, respectively, and an increase in thermal conductivity of 172 %, 54.9 % and 82.4 %, respectively, all with good phase change thermal storage properties. Even after 100 thermal cycles, the latent heat retention rate was more than 97 %, which had good thermal reliability. Therefore, it can be concluded that the three kinds of low, medium, and high-temperature C-PCMs have considerable application potential in different temperature areas, such as building latent heat storage, solar energy storage systems, and industrial waste heat recovery system.

Effects of porous silicon carbide supports prepared from pyrolyzed precursors on the thermal conductivity and energy storage properties of paraffin-based composite phase change materials

In this work, novel shape-stabilized silicon carbide/paraffin composite phase change materials were prepared by a vacuum impregnation method. The silicon carbide increased the thermal conductivity of the composite, and its porous structure acted as the support material to improve the mechanical integrity of the composite. The pore sizes in the shape-stable silicon carbide matrix were easily adjusted by optimizing the pyrolytic conditions used to prepare the precursor. Composite phase change energy storage materials were prepared by impregnating the different porous silicon carbide support with paraffin. The prepared silicon carbide/paraffin composites were characterized with X-ray diffraction and scanning electronic microscopy. The results showed that the paraffin was adsorbed within the porous structure as well as on the surface of the SiC, and there was no chemical reaction between the two components. The results of differential scanning calorimetry analysis showed that the melting temperatures and latent heats of the composites were 58.36 °C and 89.76 J/g, respectively, and the thermal storage capacity of the composites was as high as 99.36 %. Notably, the thermal conductivity of the composite was as much as 4.28 times higher than that of pure paraffin. The excellent thermal conductivity and good thermal storage capacity of the composites prepared here make them promising materials for storing thermal energy in practical applications.

Synthesis and thermophysical properties of Tetrabutylammonium picolinate hydrate as an energy storage phase change material for cold chain

Ionic semiclathrate hydrates, the water-based phase change materials (PCMs) have potential for thermal energy storage media. There are a number of hydrates, reported in the literature, which are suitable as PCMs for air conditioning system of the required temperature range 10–15 °C. In this study, Tetrabutylammonium picolinate hydrate (TBAPi hydrate) was newly synthesized as a PCM for the cold chain, which has a lower phase equilibrium temperature than the previously reported hydrates. Thermophysical properties of TBAPi hydrate were experimentally measured. The hydrate dissociation heat was determined using a differential scanning calorimeter (DSC). The phase equilibrium temperature was measured by visually observing system with a CMOS camera and microscope. Also, the cycling test was conducted to confirm the long-term stability of thermophysical properties. The largest dissociation heat was 157.7 ± 4.9 kJ･kg−1 at a mass fraction of TBAPi aqueous solution, wTBAPi of 0.37. The highest phase equilibrium temperature of TBAPi hydrate was 5.5 °C at 0.34 ≤ wTBAPi ≤ 0.36. These thermophysical properties did not change even after 200 cycles of hydrate formation and dissociation. Based on the experimental results, TBAPi hydrate can be applied to the transport and storage of vaccines, blood packs, and perishable foods.

Optimal predictive control of phase change material-based energy storage in buildings via mixed-integer convex programming

This paper describes a mixed-integer convex programming-based control strategy to optimize the operation of phase change material-based energy storage integrated in building supply ducts. To improve the numerical feasibility, the original nonlinear control problem is pre-conditioned and transformed to a mixed-integer convex program through convexification of the cooling system control model, mixed-integer reformulation of the phase change material dynamics and discretization of the supply airflow. The overall control framework was leveraged toward development of two model predictive control strategies to optimally charge/discharge the phase change material storage, through supply air temperature reset, and the building passive thermal mass, via scheduling of the zone air temperature setpoint. These strategies were tested and compared to two baseline control strategies using a simulation case study over three summer days. Test results show that using the phase change material energy storage alone, energy cost savings of 2.9% and peak demand reduction of 46.7% could be achieved, compared to a conventional fixed-supply air temperature and zone air temperature night setup control strategy; when both the active (phase change material) and passive (building thermal mass) storage capacities are utilized, the savings potentials could increase to 8.4% for the energy cost and 65% for the demand charge. • Integration of PCM energy storage in supply ducts is effective in reducing demand. • Predictive control of PCM storage offers significant utility cost savings potential. • Charging/discharging of PCM thermal storage results in efficiency losses. • Combining active and pass storage can provide the maximum load shifting potential.

Incorporation of controllable supercooled phase change material heat storage with a solar assisted heat pump: Testing of crystallization triggering and heating demand-based modelling study

In short to long-term heat storage, the heat loss of common phase change material (PCM) systems is a big problem where heat is lost continuously to the ambient environment and is thus wasted, even when the system is not in use. Controllable supercooled PCM in the proposed system offers a solution to this problem. Latent heat is only released when the supercooled PCM is triggered to induce crystallization, so it can be stored at ambient temperature. To control the release of heat, the installation will be constructed as a group of PCM storage units, each with its own trigger, which can be activated according to the heating demand of a building perhaps over several days. The proposed versatile PCM energy storage system can play an essential role in synchronizing energy demand and supply, on a short to long-term basis (days/weeks). In this study, an electrical triggering mechanism is constructed and tested in the laboratory to control the crystallization of the PCM. The PCM temperature increased from 20 °C to 56.4°C in 20s after triggering. After validation of controllable crystallization and melting time, a solar-assisted heat pump coupled with supercooled PCM storage units was simulated considering the heating demand profile of an eco-house in Nottingham, UK. The charging time of the PCM tank was found 6.5h when 8 cm diameter PCM tubes were adapted. During discharging period, the hot water supply temperature was achieved at higher than 43 °C, considering the one-day heating profile of the building.

Application of Energy Saving and Environmental Protection Materials in Architectural Design

With the improvement of the living standards of the Chinese people, the construction of the economic system will change from one that meets the needs of the people to one that is perfect. Under the current environment of building a resource-saving socialist harmonious society, it is very necessary for architectural design practitioners to return to the original architectural design and pay attention to the design and use of building materials during construction. The purpose of this paper is to explore and analyze the application of energy saving and environmentally friendly materials in architectural design. This paper firstly analyzes the building’s energy consumption and building’s energy efficiency. Every major achievement in building energy efficiency will be an important means of mitigating the Earth’s energy. Building energy saving has become a major trend of global development, and then the optimal design of reinforcement selection for reinforced concrete beams based on a multiobjective genetic algorithm is discussed. The area of reinforcement required for the member control section is obtained according to the structural analysis program, the main purpose of reinforcement selection is to select safe, economical, and reasonable reinforcement on the premise of meeting the provisions of the code and the requirements of reinforcement structure. Finally, this paper conducts experimental research on the application of phase change energy storage building material SP28 in building energy conservation. The experimental results in this paper show that when the mass ratio of the phase change energy storage material in the wall is less than 15%, there is no wetting and leakage phenomenon. However, when the mass ratio of the phase change energy storage material contained in the wall is greater than 15%, the phenomenon of wetting and leakage will occur, which will cause greater losses when added to the wall. Therefore, it is not suitable for application and building walls. Regardless of leakage, wetting, or economic considerations, the mass ratio of phase change material of 10% is the most suitable for use in walls. It not only has no wetting and no leakage but also has a good energy storage effect and can effectively adjust the ambient temperature.

Economic and energy evaluation of a solar multi-generation system powered by the parabolic trough collectors

Due to the increase in living standards, the increased energy consumption, and the depletion of fossil fuels, it is crucial to provide part of this demand through renewable energies. Due to the high potential of solar energy and its inherent variability over time, dynamic evaluation of a multi-generation system over a long time can examine the performance of such systems more precisely, which is rarely paid attention. In this study, a dynamic solar combined cooling, heating, power, and water production has been modeled with the help of MATLAB, EES, and TRNSYS software. Moreover, a phase change material energy storage unit has been used to store solar thermal energy and reuses the stored energy in case of low or without solar radiation modes. The desired configuration has been investigated from the energy and economic points of view. Also, sensitivity analysis and parametric studies have been done on the eight effective parameters. Evaluating various organic Rankine fluids illustrates that toluene has the best annual performance. Furthermore, the amounts of LCOW, LCOE, LCOC, and LCOH for the base case are 2.984 $/m3, 0.121 $/kWh, 0.064 $/kWh, and 0.019 $/kWh. Also, the payback period is determined 6 years for the base case.

Effect of variable capsule size distribution for unstructured packed bed encapsulated phase change material system

Packed bed encapsulated phase change material (PCM) energy storage systems have considerable potential for energy storage applications involved in renewable energy systems. In this paper, a 3D unstructured packed bed system consisting of spherical encapsulated phase change material with varying sizes of spheres is modelled. The main novelty of the work is that the geometry of the capsules and the flow between the capsules are resolved, even with unequal capsule sizes arranged in an irregular manner. The size of the spheres is varied by changing the radius of the spheres following specified normal distribution curves. Then, by changing the mean and standard deviation values, different size distributions of spheres are generated which are arranged in unstructured packed bed form. The model incorporates the flow of heat transfer fluid (HTF) through the gaps between the capsules, the heat transfer in both the HTF and the PCM capsules, the melting of PCM in each capsule, and the natural convection in the melted PCM. Based on the simulations, important parameters such as the melting time and energy storage rates are compared for different size distributions. It is found that for a normal distribution of capsule radius, increasing the mean radius by 2 times while keeping the standard deviation constant increases the melting rate considerably with an increase in melting time by 29.4%. The effect of standard deviation of radius was found to be significantly less as compared to that of the mean radius.

Microstructure and thermal conductivity of paraffin@burning garbage ash phase change energy storage materials embedded in hydraulic cementitious composites: Experiments and numerical simulation

The incorporation of phase change materials into buildings such as concrete has a significant effect on tempering and energy saving. Paraffin@burning garbage ash Phase change energy storage Materials (PPMs) were manufactured through a mixed grinding-heating method, whose chemical-physical properties were observed using a series method. Then, PPMs were added to gypsum and cement paste to evaluate their mechanical properties and thermal conductivity. Finally, a thermal conductivity numerical model of cementitious materials was established using the lattice Boltzmann method and compared with the experimental results. The results demonstrate that the paraffin can be fully incorporated into the pores of burning garbage ash and the composited material can form a whole, and its chemical and thermal properties are stable. The compressive strength of the composited material hardly changes when the PPM dosage is less than 10% while the compressive strength declines by approximately 40% when the dosage reaches 30%. With the increasing PPMs, the thermal conductivity of hydraulic cementitious composites decreases significantly up to 61%. Therefore, the phase change composites have good latent heat of phase change and mechanical properties when the doping amount is between 10% and 20%. The effective thermal conductivity simulated corresponds well with the experimental results. This study provides a theoretical basis for the use of this composite phase change material for energy saving in concrete.

Experimental investigation of phase change material energy storage system integrated with thermoelectric generator under transient heat loads

ABSTRACT Thermoelectric generator (TEG) systems are often exposed to unstable heat loads with transient temperature boundary conditions. TEG behavior recognition in thermal fluctuations is necessary to increase its efficiency and protection. This research deals with the experimental study of thermoelectric module’s performance under transient thermal boundary conditions. Therefore, three types of novel prototypes of transient heat loads including rectangular, triangular, and sinusoidal were suggested. Also, a phase change material (PCM) was applied inside an aluminum box on the hot side of the module. In the mentioned system, the effect of PCM on the module performance in the unstable heat loads was investigated. Applying PCM led to the protecting the module against temperature fluctuations, storing the energy, and generating effective voltage for a long time after turning the heat source off. Voltage generation lasted for 59.5 min with 90 W input power in 3-min periods in the rectangular heat load. Meanwhile, after switching the heaters off, 42.8- and 50-min voltages were received from triangular and sinusoidal loads, respectively, each with the power ranging from 0 to 90 W in four periods, lasted for 3 min.

Effect of porous carbon on thermal and physical properties of composite pure alkane/expanded vermiculite phase change energy storage materials

Nine kinds of mixed N-alkanes with different proportions were prepared by mixed eutectic method. A set of ratios with enthalpy values up to 289.8 J/g were selected for encapsulated PCM. Using potato starch solution with a concentration of 30 % as porous carbon source, the heat transfer capacity of expanded vermiculite was enhanced by modification between expanded vermiculite channels, and matrix coated phase change material was prepared. SEM images show that the PCM are successfully adsorbed in the pores. The latent heat and temperature of phase change in the melting and solidification process are 208.1 J/g and 21.2 °C, 203.11 J/g and −3.4 °C, respectively. FT-IR, XRD, TGA and thermal cycling test results show that phase change energy storage particles have good thermal performance. Therefore, the prepared materials have excellent properties.

Effects of Branched Fins on Alumina and N-Octadecane Melting Performance Inside Energy Storage System

The importance of Phase change material (PCM) energy storage systems is no longer new in the industry. However, the influence of using branched fins inside the energy storage system on the melting process of alumina nanoparticles and n-octadecane has not been reported in the literature. Consequently, the outcome of a study on the numerical simulation for optimizing the melting performance of a PCM in various tubes, including those with branching fins is presented in this report. Four examples were assessed in relation to a suspension of alumina nanoparticles and n-octadecane paraffin that contains heated fins. A numerical technique based on the Galerkin finite element method (GFEM) was used to solve the dimensionless governing system. The average liquid percentage over the flow zone in question was computed. The primary results indicated that altering the number of heated fins might affect the flow structures, the system’s irreversibility, and the melting process. Case four, with eight heated fins, likewise produces the greatest average liquid fraction values and completes the melting process in 850s. Additionally, when 6% nano-enhanced PCM was used instead of pure PCM, the melting process is accelerated by 28.57 percent.

Synthesis and encapsulation of 1, 4-butanediol esters as energy storage phase change materials for overheating protection of electronic devices

Development and application of thermal energy storage phase change materials (PCMs) with different temperature ranges, non-toxic, high latent heat and thermostability has been the focus of research. This study aims to synthesize a series of diester PCMs with high latent heat and thermostability based on the esterification of 1, 4-butanediol and fatty acids, following microencapsulation of the synthesized diester for overheating protection application. The obtained diester PCMs show a phase change temperature range of 30–80 °C, latent heat up to 240 J/g and volatilization temperature over 230 °C. Considering the suitable phase change temperature for overheating protection, octadecanoic acid 1, 4-butanediol ester was selected and encapsulated with silica as shell by a novel one-pot interfacial polymerization route. The microencapsulated phase change material (MEPCM) achieves a high encapsulation rate of 88.4 % and a satisfactory latent heat capacity of about 211 J/g. After consecutive heating and cooling cycles, the retention rate of thermal storage capacity exceeds 98 %, showing excellent thermal cycling stability. When used in overheating protection, the MEPCM exhibits effective temperature regulation and thermal management performance. During the application of overheating protection, a remarkable temperature hysteresis was observed on a MEPCM treated semiconductor chilling chip due to the heat storage of the MEPCM. The results imply that the MEPCM can provide effective overheating protection as a passive thermal management system.

Dynamic 4E (energy, exergy, economic and environmental) analysis and tri-criteria optimization of a building-integrated plant with latent heat thermal energy storage

The buildings energy sector is expected to account for 40% of total world energy consumption and 40% participation on total carbon dioxide emissions, according to the International Energy Agency reports. The present study proposes a novel integrated system to meet all loads of the house's energy requirements. The system employs a heat storage tank rather than pricey batteries, which helps to keep the total cost of the system as low as feasible. Also, the system is developed for an on-grid operation, being capable to sell surplus energy to the grid helping to reduce the payback time. Dynamic modeling is conducted to analyze the system performance to provide heating, cooling and power demands of a case study building, for which two scenarios of with and without Phase Change Material (PCM) incorporation is considered. The influence of critical design factors is investigated, after which a tri-objective optimization is carried out. It was found that, the integration of PCM energy storage would reduce the annual heating and cooling demands of the building by 25.6%. As a result, the exergy efficiency of the proposed system increases by 13 % and the product cost is reduced by 8.57%. Based on the obtained yearly average results, the proposed building energy system yields exergy efficiency, unit product cost, and CO2 emission of 64.3 %, 0.26 $/kWh, and 0.21 kg/kWh, respectively.