Phase Change Materials For Energy Storage Research Articles

Preparation and Heat Transfer Performance of Steel Ball Phase Change Concrete

Accompanied by a large amount of heat absorption and release during the phase change process, phase change concrete has the advantages of high energy storage density, low volume expansion ratio and approximate isotherm in the heat exchange. It is widely used in the building field. For this, using steel balls as the carrier material and butyl stearate as the phase change material (PCM), the authors combined the phase change energy storage material with the energy pile to prepare a new type of concrete energy pile enhanced with the PCMs. Then, the tests and numerical simulations were conducted to study the optimal mix ratio and thermal conductivity of the phase change concrete. The results show that adding steel balls (10% of the coarse aggregate volume), and slag and fly ash (5% of the cementitious material mass) to the ordinary concrete C30 can greatly improve the heat transfer efficiency of the energy pile. The research findings provide a guidance for engineering practice.

Performance Investigation of Solar Water Heating System with V-Shaped Absorber Plate Integrated PCM Storage

The use of solar energy source using Solar Water Heating (SWH) system for hot water supply is increasing due to environmentally friendly technology. The increase of the application of solar energy equipment is beneficial for technology development related to the issue of sustainable energy and green energy buildings. This study develops a SWH system for hot water supply with modification of absorber plate. An integrated V-shaped absorber plate with phase change material (PCM) energy storage in the SWH system has been installed and its performance has been investigated experimentally. Two SWH systems consisting of V-shape absorber plate with and without PCM storage are built. The V-shape absorber plate is constructed and integrated with PCM storage in the system. The experimental tests of the two SWH systems using V-shaped absorber plate with and without PCM storage have been carried-out in the same operation time with various flowrates. The temperature of the paraffin has increased until the melting temperature and has decreased with the decrease of solar radiation in the afternoon. Paraffin as PCM storage contributes to increase the outlet water temperature. The results show that the average efficiency of the SWH system with PCM storage using paraffin is higher than the one of the SWH system without PCM storage. It has increased significantly of 20%, 14% and 13% with flowrates of 0.5; 1 and 1.5 L/min respectively. In addition, the characteristics of the PCM storage are shown clearly from 16:00 to 20:00 local time. After 16:00 local time, the storage energy can be a source of heat energy to heat the water up to the end of the day.

Analysis of Nonlinear Transient Energy Effect on Thermoelectric Energy Storage Structure.

In complex flight conditions, due to the large amount of unusable heat generated by aerodynamic heating, the thermal protection system of an aircraft needs to withstand a large temperature shock, which brings great challenges to the design of the structure. In order to effectively utilize the irregular aerodynamic heat, and improve structural heat conduction, a composite structure is formed by using phase change energy storage materials on the basis of the thermoelectric structure, which transforms the aerodynamic waste heat into stable electric energy for the internal system. Through the study of the response of nonlinear transient energy, it is found that the thermoelectric and mechanical properties of the new structure can be improved by adding phase change energy storage materials. Under actual flight conditions, the new structure can reduce the maximum temperature by 180 K and the maximum thermal stress by 110 Mpa. The mechanical properties of the structure are effectively improved, the service life of the structure is prolonged, and the waste heat can be converted into stable electrical energy output to improve the thermoelectric output performance. On the premise of ensuring conversion efficiency, the output power of the new structure has been improved by 64.8% through structural optimization under actual flight conditions.

Preparation and characterization of sodium thiosulfate pentahydrate/expanded graphite phase change energy storage composites

AbstractIn order to solve the problems of high supercooling, poor thermal conductivity and phase separation after repeated use of Na2S2O3·5H2O with additives. In this paper, Na2S2O3·5H2O is used as the matrix phase change material, and 1% sodium carboxymethyl cellulose, 3% SrCl2·6H2O, and 10% expanded graphite (EG) are added to prepare the modified Na2S2O3·5H2O composite phase change energy storage material. Based on the existing research, the effects of reducing supercooling, improving thermal conductivity, and improving stability are further optimized. The phase change temperature, supercooling degree, heat release time, phase change latent heat, and thermal conductivity of the material are tested by temperature data acquisition instrument, differential scanning calorimeter, hot disk thermal constant analyzer, and other instruments. The effect of EG on the thermal conductivity of the Na2S2O3·5H2O composite phase change energy storage material was explored from the microstructure through a digital scanning electron microscope; Fourier transform infrared spectroscopy verified the composition of the composite phase change materials. After 200 cycles of melting and solidification, the improved composite phase change material has a phase change temperature of 43.49°C, a supercooling degree of 2.19°C, a phase change latent heat of 198.7 J/g, and a thermal conductivity of 3.42 W/m·K. Composite phase change material shows good thermal stability and provides strong support for phase change energy storage technology.

Characterisation and stability analysis of eutectic fatty acid as a low cost cold energy storage phase change material

Abstract Phase Change Material (PCM) is one of the most promising material for storing thermal energy and supplying the stored energy for cooling applications but low cost, easily available PCM are quiet less. The present work focused on the development of a suitable eutectic PCM for low temperature applications like building cooling, based on organic fatty acids, capric acid (CA) and myristic acid (MA) in the mass ratio of 85:15 and investigating their thermal properties, chemical and thermal stabilities by using by using DSC, FT-IR, TGA and KD2 Pro. Thermal cycle test were also investigated through developed thermal cycle equipment. The properties were also compared with their individual fatty acids. From the DSC test, the latent heat capacity was determined as 156.99 J/g and the phase change temperature as 20.86 °C. Thermal conductivity of liquid CA-MA PCM was measured as 0.152 W/mK. Thermal gravimetric analysis results revealed that the eutectic PCM had high thermal stability. Fourier Transform Infrared spectroscopy (FT-IR) revealed that the binary eutectic mixture had good chemical stability. Thus, the new low-cost, CA-MA eutectic PCM possessed high latent heat for low temperature with good thermal and chemical stabilities making it a potential phase change material for cold energy storage applications.

Exothermic process and heat transfer of iron foam/paraffin composite phase change energy storage materials

Exothermic process and heat transfer of iron foam/paraffin composite phase change energy storage materials

Evaluation of pumice for development of low-cost and energy-efficient composite phase change materials and lab-scale thermoregulation performances of its cementitious plasters

Integration of a building mass with a phase change-energy storage material is able to improve its thermal efficiency. With this respect, pumice was evaluated as low-cost supporting material for development of energy-efficient composites containing capric acid (CA) and polyethylene glycol(PEG) as phase change material (PCM). The developed leak-proof composites was also incorporated separately with ordinary cement (OC; Portland Cement) to produce novel plaster with thermal energy storage (TES) ability for thermoregulation of buildings. The DSC analysis results demonstrated that the shape-stabilized composite PCMs (S-SCPCMs) had melting temperatures of 31.03 °C and 8.80 °C and TES capacity of 116.27 J/g and 98.39 J/g, respectively. Cycling thermal degradation stability and TES dependability of the leak proof composites were examined by TGA techniques. The lab-scale test revealed that the indoor center temperatures (ICT) of the cubic chambers plastered separately by pumice/CA/OC and pumice/PEG/OC mortars were maintained at comfortable temperature range for relatively longer times compared to the control chamber plastered by OC mortar.

Demand Control Strategies of a PCM Enhanced Ventilation System for Residential Buildings

A ventilated window system enhanced by phase change material (PCM) has been developed, and its energy-saving potential examined in previous works. In this paper, the ventilation control strategies are further developed, to improve the energy-saving potential of the PCM energy storage. The influence of ventilation airflow rate on the energy-saving potential of the PCM storage is firstly studied based on an EnergyPlus model of a sustainable low energy house located in New York. It shows that in summer, the optimized ventilation airflow rate is 300 m3/h. The energy-saving of utilizing a ventilated window with PCM energy storage is 10.1% compared to using a stand-alone ventilated window, and 12.0% compared to using a standard window. In winter, the optimized ventilation airflow rate is 102 m3/h. The energy-saving of utilizing a ventilated window with PCM energy storage is 26.6% compared to using a stand-alone ventilated window, and 32.8% compared to using a standard window. Based on the optimized ventilation airflow rate, a demand control ventilation strategy, which personalizes the air supply and heat pump setting based on the demand of each room, is proposed and its energy-saving potential examined. The results show that the energy savings of using demand control compared to a constant ventilation airflow rate in the house is 14.7% in summer and 30.4% in winter.

Thermal energy storage and thermal conductivity properties of Octadecanol-MWCNT composite PCMs as promising organic heat storage materials

Fatty alcohols have been identified as promising organic phase change materials (PCMs) for thermal energy storage, because of their suitable temperature range, nontoxicity and can be obtained from both natural and synthetic sources. Like all other organic PCMs, octadecanol (OD) as PCM suffers from low thermal conductivity (TC). In this work, to enhance its TC, it was grafted on the functionalized MWCNT and were used as a conductive filler to enhance overall thermal properties of OD in a composite PCM (CPCMs) structure. The OD/OD-g-MWCNT sample showed better dispersion within the composites and the presence of additional OD boosted the overall heat storage enthalpy compared to that of plane composite sample with OD/MWCNT. In a non-quantitative approach, it was observed that, any increase in grafting ratio of OD increases the heat storage enthalpy of the composites. The heat storage enthalpy of (267.7 J/g) OD/OD-g-MWCNT(4:1)-5wt% composite PCM had reached very close to the heat storage enthalpy value of pure OD (269.3 J/g), and much higher than that of OD/MWCNT-5wt% (234.5 J/g). Champion sample i.e. OD/OD-g-MWCNT (4:1)-5wt%, showed good heat storage enthalpy, cycling performance, thermal stability and TC enhancement by 262.5%.

Modern Eminence and Concise Critique of Solar Thermal Energy and Vacuum Insulation Technologies for Sustainable Low-Carbon Infrastructure

A concise critique on harnessing the abundant solar thermal energy and improvement with vacuum insulation for the utilization and conversion is presented. This research implicates that the world is becoming a global solar smart city prompted by increasing daily demand of energy by the global population and land-use. Amongst all the renewable energy resources available, solar thermal energy collectors (STC) are the most copious because it is accessible in both direct and indirect modes with global solar thermal capacity in operation in 2019 was 479 GWth and annual energy yield estimated to be 389 TWh. Hybridization has been found to be the only way of improving the existing performance of (STC) such as hybrid photovoltaic thermal (PVT) with phase-change material (PCM) for energy storage and magneto-thermoelectric generators (MTEGs) and/or vacuum insulated TEG (VTEG) for waste heat energy conversion to electrical power. The concentrating solar power (CSP) technologies were also precisely studied and yet parabolic trough collector, dish sterling and solar tower are amongst the top solar thermal heat energy harvesters and its electrical power generation has also been comprehended. The modern eminence of vacuum insulation technologies on thermal comfort and sound insulation in sustainable low-carbon buildings is presented. The research implicates that there is still a scope of improving the building and construction sector and target to achieve not only zero-energy buildings (ZEB) but generating-energy buildings (GEB). A concise critique on vacuum insulated smart glazed windows is presented and the review implicates that the hybridization with PV and TEG and novelty in the constructional materials of vacuum glazing (VG) and translucent vacuum insulation panel (TVIP) are vital in the realistic move towards the GEB. The future of vacuum insulation is not only limited to GEB but vital applications occur in medical, imaging, mechatronics and manufacturing industries.

Design and experimental investigation of a phase change energy storage air-type solar heat pump heating system

To improve solar energy utilization and the stability of solar heating systems, an energy storage air-type solar collector was designed and developed. Phase change material was placed in the middle of the solar vacuum tube to reduce the impact of solar radiation fluctuations on indoor heating. Based on this, a new type of solar heat pump heating system was established, with three heating modes: solar heating, solar-assisted heat pump heating, and heat pump heating. The control system was designed to automatically switch the operational mode when environmental conditions change. The heating performance, exergy efficiency, and economic benefit of the system in engineering application were studied and analyzed for different weather conditions. The results of the investigation show that at an average solar radiation intensity of 613.4 W·m−2 and average ambient temperature of 12.5 °C, the system can provide continuous indoor heating for 9.5 h in the solar heating mode, with the solar collector operating at an average thermal efficiency of 44.8%. The energy stored in the phase change material energy storage core is still capable of running the heat pump efficiently for 3 h after solar heating ends. The exergy efficiency of the heat pump is significantly improved by an average value of 12.1%. Economic analysis shows that the system can adequately meet building heating demands, with an average coefficient of performance of 3.6. Compared with the electric boiler heating system, the proposed system can reduce annual operating costs by 72.8%, with a payback period of approximately five years in Northern China.

Numerical investigation of an innovative discontinuous distribution of fins for solidification rate enhancement in PCM with and without nanoparticles

Energy storing is one of the most vital needs in the energy industry. This paper aims to solve the problem of long energy release time in phase change material (PCM) energy storage system. In the present study, continuous longitudinal fin that had been traditionally used in literature is transformed into a new three-dimensional distribution of discontinuous strip fins. Effects of the geometric distribution of the strip fins, fins material and adding nanoparticles (NPs) to the PCM on heat transfer enhancement and energy discharge time are investigated by testing 17 different cases. According to the results, the use of discontinuous fins can improve the energy release time up to 89% and 84% comparing to continuous copper and aluminum fins, respectively. Moreover, the results indicate that effect of fin material on the thermal performance is insignificant in cases of continuous fins. The results confirmed that the optimal distribution for cases of discontinuous aluminum fins with and without NPs is different. Besides, the maximum of saving discharge time is 77.8% and 59.5% for combination of NPs with copper and aluminum discontinuous fins, respectively. Besides, the results show that the application of nanoparticles alone cannot lead to a significant discharge time improvement.

Preparation of two-dimensional nano montmorillonite/stearic acid energy storage composites with excellent stability and heat storage property

Phase change energy storage materials have the ability to store thermal energy during the phase change process, and release the stored energy when desired. As a result, this technology has been extensively studied due to its potential in improving energy utilization and alleviating the problem of energy shortage. In this paper, two-dimensional montmorillonite nanosheets (2DMts) were prepared by ultrasonic method. With 2DMts as the host and energy storage molecule stearic acid (SA) as the guest, a phase change energy storage composite material (2DMt/SA) was prepared using a self-assembly approach. The d001 value of the 2DMt/SA composite was 4.08 nm, indicating that the layer of Mt. was completely peeled off. Additionally, the 2DMt/SA composite had a high latent heat storage capacity (192.4 J/g), which was nearly identical to that of SA samples. Compared with SA, the thermal stability of 2DMt/SA was significantly improved. After 50 cycles of heating and cooling, only 0.557% of the latent heat was lost. There was no liquid leakage indicating that the composite had an excellent structure stability. In addition, after nano silicon carbide (SiC) was added to the 2DMt/SA system, the thermal conductivity of the system increased by 113.7%. This self-assembly method solved the problem of liquid leakage and poor thermal stability in phase change materials. As a result, the 2DMt/SA composite can be applied to road asphalt materials for surface protection applications.

A novel solar thermal system combining with active phase-change material heat storage wall (STS-APHSW): Dynamic model, validation and thermal performance

Due to the energy shortage and air pollution caused by heating emissions, solar energy becomes the first choice for clean heating in China. On this basis, a novel solar thermal system coupling with active phase-change material heat storage wall (STS-APHSW) is proposed in this study. And the thermal performance of STS-APHSW is numerically explored by one transient heat transfer model combined with TRNSYS. Taking indoor temperature as the evaluation index, the effect of the solar collector area, hot water flow rate, initial melting temperature and thickness of phase change material energy storage wallboard (PCMSW) on the indoor temperature maintained by STS-APHSW is discussed and analyzed. Economic comfort ratio is proposed to be as the assessment criteria. Results show that the optimal configuration is achieved when: the solar collector area per square unit building area is 0.024 m2, hot water flow rate is 2.8 kg/s, initial melting temperature is 27 °C and the thickness of PCMSW is 20 mm. This study proves that STS-APHSW can well balance the time mismatch between the solar supply and demand, thus increasing the solar fraction and solar energy application potential in the clean heating.

Palmitic Acid-Stearic Acid/Expanded Graphite as Form-Stable Composite Phase-Change Material for Latent Heat Thermal Energy Storage

The aim of this study is to prepare a novel form-stable phase-change material (PCM), palmitic acid-stearic acid/expanded graphite (PA-SA/EG) PCM, for latent heat thermal energy. A eutectic mixture of palmitic acid and stearic acid is incorporated with expanded graphite (EG). The thermal properties and microstructure of the novel PCMs were studied. The optimal mass ratio of PA-SA in composite PCM is approximately 92.8%. DSC results showed that the novel PCMs had suitable phase-change temperature (Tm: 55.18°C, Tf: 54.91°C) and high latent heat (Hm: 176.2 J/g, Hf: 175.6 J/g), and good thermal performance was maintained after 1500 times thermal cycling. The PA-SA binary eutectic mixture was uniformly distributed in the porous structure of EG, and the PCM did not leak even in molten state. EG had little effect on the thermal properties of the PA-SA binary eutectic mixture and remarkably improved the thermal conductivity of the composite PCMs. TGA test indicated that the composite PCM had nice thermostability in the range of operating temperature. Based on all these results, the PA-SA/EG composite PCM is a promising material for low-temperature thermal energy storage applications.

Preparation and Numerical Simulation of Heat Transfer Performance for Methyl Palmitate /Expanded Graphite Phase Change Composite

Methyl palmitate (MP) is a promising phase change energy storage material. It features high latent heat, suitable phase change temperature, low degree of supercooling and so on. However, like other organic phase change materials, the common problem of lower thermal conductivity makes it unable to perform better in energy storage. Expanded graphite (EG) has been proven to be high-efficiency for enhancing the thermal conductivity of organic phase change materials. MP/EG phase change composite was prepared and characterized in this research, and the heat transfer performance was numerical simulated by finite element analysis software ABAQUS. Results show that MP can be absorbed into the layered pores of EG, and the stable absorption ratio is 77%. Numerical simulation results reveal that EG can significantly enhance the heat transfer performance of MP. Moreover, EG can decrease the system temperature gradient during phase change process that makes the heat transfer and temperature distribution more uniform.

Energy saving application of phase change materials in buildings: A comprehensive review

The theoretical basis of the preparation of phase change energy storage materials is analyzed firstly, and then the preparation methods of fatty acid phase change energy storage materials are analyzed in detail. Furthermore, the application of phase change energy storage materials in building energy saving is analyzed. Finally, combined with the above contents, the application prospect and research direction of phase change energy storage materials are briefly described.

Induced dipole force driven PEG/PPEGMA form-stable phase change energy storage materials with high latent heat

Phase-change materials (PCMs) can store and release great amount of thermal energy during the phase change and thus have broad application prospects in thermal energy management, waste heat recovery, building energy conservation, and other fields. However, the before and after state changes of PCMs are often accompanied by liquid leakage, thus severely limiting their application. Introducing supporting materials can solve this leakage problem but at the expense of phase-change enthalpy and service life. Herein, a novel comb-like structural phase-change composite with high latent heat was designed by using poly (ethylene glycol) (PEG) chain, which tightly intertwines with a comb-like structural phase-change supporting material under induced dipole force due to structural compatibility. This material can achieve shape stability and obtain high phase-change enthalpies (168.9 J/g–200.3 J/g). Furthermore, the composite does not show phase separation due to the good compatibility, and its phase-change temperatures and enthalpies can be adjusted by regulating the content and molecular weight of the loaded PEG.

Preparation and thermal properties of microencapsulated paraffin with polyurea/acrylic resin hybrid shells as phase change energy storage materials

Microencapsulated paraffin with polyurea/acrylic resin hybrid shells as phase change energy storage materials was obtained in situ by combining interfacial polymerization and suspension-like polymerization. Glycerin (GC) acts as a cross-linking agent to modify the shells. The morphologies, particle size distributions, thermal storage properties, thermal stabilities and thermal reliabilities of microencapsulated phase change materials (MicroPCMs) were determined by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TG). The temperature regulation performance of the foam with MicroPCMs was investigated by an infrared thermal imager. DSC results showed that MicroPCMs with polyurea/butyl methacrylate (PU/BMA) possess an improved heat ability and thermal reliability compared to MicroPCMs with polyurea/methyl methacrylate (PU/MMA). The incorporation of GC to shell-forming composition led to an enhancement in thermal storage capacity of the MicroPCMs. The MicroPCMs with GC-modified PU/BMA hybrid shell has the highest PCMs content by as much as 82.6 mass%. The change in latent heat of MicroPCMs with GC-modified PU/BMA hybrid shell was very small of less than 4 mass% after 500 thermal cycles. The infrared thermography indicated that the PU foam incorporating the MicroPCMs with GC-modified PU/BMA hybrid shell has better temperature-regulated property. In conclusion, the MicroPCMs with PU/BMA hybrid shells, especially with GC-modified PU/BMA hybrid shell, possess a promising prospect applying in energy-conserving building materials and thermal control system of shipping packages.

Study on performance optimization of sodium sulfate decahydrate phase change energy storage materials

In this paper, sodium sulfate decahydrate (SSD) with a phase transition temperature of 32 °C was selected as the phase change energy storage material. However, SSD has the problems of large degree of supercooling, obvious phase stratification, and low thermal conductivity. To address these issues, a new SSD composite phase change energy storage material was synthesized by adding certain amounts of nucleating agents, thickeners, and high thermal conductivity agent to SSD. The results showed that when the addition of nucleating agent Na2B4O7·10H2O and thickener carboxymethyl cellulose (CMC) reached an optimal formulation ratio of SSD:Na2B4O7·10H2O:CMC = 100:5:3, the supercooling degree of the SSD composite phase change material was only 1.5 °C. Moreover, the heat release time of the phase change process was 25 min, and no phase stratification occurred. When expanded graphite with high thermal conductivity was added with the mass ratio of 9%, the effect on the supercooling degree of the SSD composite energy storage material was small, and the thermal conductivity increased by 3.9 times, reaching 2.13 W m−1 K−1. Differential scanning calorimetry method and step cooling curve method were used to test the decay rate of the thermal properties of the new composite phase change energy storage material, and the results were relatively close.