Field Of Thermal Energy Storage Research Articles

Biomass porous potatoes/MXene encapsulated PEG-based PCMs with improved photo-to-thermal conversion capability

Encapsulated phase-change materials (PCMs) have been widely studied in the field of solar thermal energy storage due to the advantages of stable shape and repeatability. In this work, a series of potatoes phase-change materials (PPMs) were conceived and synthesized via a common vacuum impregnation method, with biomass porous potatoes (PP) as substrate, polyethylene glycol (PEG) as phase change medium and MXene nanosheets as functional filler. The experimental results show that the introduction of MXene nanosheets not only significantly improve the photo-to-thermal conversion efficiency, but also help to increase the adsorption rate of PEG in PCMs. The PEG percentage of potatoes phase-change material (PPM) increases from 60.9% (PPM-0) to 82.1% (PPM-12.5), melting/freezing enthalpy values are also increases from 94.08 J/g/100.46 J/g of PPM-2.5 to 135.57 J/g/139.88 J/g of PPM-12.5, and its enthalpy efficiency λ and relative enthalpy efficiency η also increase from 57.6%/91.5% to 77.7%/98.3%. The results show that the prepared PPMs can be effectively applied to solar photo-to-thermal energy storage.

The relevance of thermochemical energy storage in the last two decades: The analysis of research evolution

The research field on thermochemical energy storage (TCS) has shown consistent growth over the last decade. This study analysed over 1196 scientific publications in indexed journals and books from the last decades. What can we learn from analysing the evolution of research? There is no other study that has used bibliometrics to perform a detailed analysis of the TCS field, which has only been assessed from the perspective of the whole thermal energy storage field to date. The trends obtained in this study provide an important perspective of the field, indicating the strengths and weaknesses of the thermochemical materials and systems applied to energy storage. The main publication trend shows an exceptional increase in TCS research and in both defined research sub-areas (sorption and chemical reaction heat storage). The sub-category chemical reaction heat storage has fewer publications compared to sorption heat storage, indicating that it is a less explored field. In general, the evolution of the keywords in publications reflects technology maturity since the most recent terms are associated more with final use applications. Remarkably, there has been a change from a total dependence on funding for scientific output to a scenario in which a significant number of publications mention no specific funding, but this trend has changed in recent years.

Preparation and thermal performance of a novel alloy microencapsulated phase change material (MEPCM)/ceramic composite

Phase change material (PCM)/ceramic composite is qualified to be a novel composite thermal energy storage (TES) material, which can simultaneously utilize the latent heat of phase change materials and sensible heat of ceramic matrix materials to accomplish the storage and release of thermal energy. It exhibits a wide application prospect in the field of medium and high temperature thermal energy storage. However, based on the ceramic porous adsorption PCM, there is still the risk of leakage after the PCM melts in the thermal energy storage stage. In this paper, SnBi58 alloy microencapsulated phase change material (MEPCM) with high thermal reliability was prepared by “double-layer coating, sacrificing inner layer” method, which a thermal expansion void was constructed to accommodate volume expansion of PCM. On this basis, SnBi58 alloy MEPCM/ceramic composite was prepared by the cold-pressing sintering method and its thermal performance was studied. The experimental results show that SnBi58 alloy MEPCM/ceramic composite does not leak at the MEPCM/Matrix mass ratio of 2.5:1, but SnBi58 alloy/ceramic composite leaks at the SnBi58 alloy/Matrix mass ratio of 1.5:1, indicating that SnBi58 alloy MEPCM has good thermal reliability and leak resistance. In addition, compared with the ceramic matrix material, the latent heat of MEPCM/ceramic composite with a mass ratio of 2.5:1 is increased by 30.24 J/g and the thermal conductivity reaches 2.853 W/(m·K), which is 3.67 times of the matrix material. Furthermore, thermal performances of four MEPCM/ceramic composite with different proportions were tested and compared, including thermal conductivity, thermal response curve and infrared thermal imaging. The results show that the higher the proportion of MEPCM, the better the thermal performance of the MEPCM/ceramic composite. Moreover, to predict the thermal conductivity of the novel composites, six thermal conductivity models were compared based on the experimental results, and the results show that the prediction error of Maxwell-Eucken is the smallest which can be used to predict the thermal conductivity of MEPCM/ceramic composite. Finally, the thermal reliability of the composite was tested. The results of DSC and XRD showed that the thermal properties and chemical structure basically have no change before and after thermal cycling. MEPCM/ceramic composite has excellent thermal reliability.

Efficacy of angled metallic fins for enhancing phase change material melting

Research on enhancing phase change material (PCM) heat transfer is concentrated in latent heat thermal energy storage (LHTES) field, especially with utilization of metallic fins. One interesting fin parameter that was less explored for a rectangular PCM system, is the metal fin's inclined angle. This research aims to experimentally validate the hypothesis and evaluate the efficacy of angled metallic fins enhancing PCM melting in a sidewall heated cuboid LHTES system. Experiments indicate that three-dimensional PCM melting in the LHTES unit can be characterized as two dimensional. The angled fins considerably influence temperature evolution of local solid PCM around fins. Compared to the horizontal fin, positive inclined fins with angles of +30° and +15° prolong the PCM melting time by 4.0% and 3.8% respectively, while the downward tilted inclined fins at −15° and −30° promote PCM melting by up to 5.2% melting fraction difference. Extending simulations with seven fin angles and three fin lengths explicate the substantial effect on PCM heat storage, melting time, and temperature uniformity. Particularly, the longest fin at the downward angle of −15° reduces the PCM melting time most. The study shows feasibility of utilizing downward angled fins to enhance PCM transient melting in the LHTES unit.

Polymer Encapsulation Strategy toward 3D Printable, Sustainable, and Reliable Form-Stable Phase Change Materials for Advanced Thermal Energy Storage.

Form-stable phase change materials (PCMs) have garnered tremendous attention in thermal energy storage (TES) owing to their remarkable latent heat. However, the integration of intelligent manufacturing, recycling, and optimized multifunction is considered not feasible for form-stable PCMs due to the restriction of encapsulation technology. Here, an excellent polymer encapsulation strategy is proposed to prepare 3D printable, sustainable, and reliable form-stable PCMs (SiPCM-x), which are universal for petroleum-based and biobased long alkyl compounds. SiPCM-x have top-class latent heat, and the phase-change temperatures are tunable from body temperature to high temperature. The in situ formative bottlebrush phase-change polysiloxane networks are used as supporting materials, and the encapsulation mechanism is clarified. Sirbw-250 can be degraded and re-encapsulated to achieve recycling. Besides, Sirbw-250 is fabricated as the customer-designed objects with shape-changing behavior via 3D printing. By introducing the metal foams and nano-coatings, the resulting phase-change composites simultaneously exhibit excellent superhydrophobicity, mechanical properties, thermal conductivity, electromagnetic interference shielding behavior, and solar-, electric-, and magnetic-to-thermal energy conversion ability. Besides, S-Ni-SiPCM-250 can be applied in the wearable functional devices and movable solar-thermal charging. This strategy will lead to huge renovation in the TES field and provide an efficient guideline for designing advanced form-stable PCMs.

Electromagnetic self-encapsulation of carbon fiber reinforced Al matrix composite phase change material for high-temperature thermal energy storage

Realizing the effective encapsulation of eutectic Al-Si melt is of paramount significance for developing the Al matrix phase change materials in the high-temperature heat storage field. In this paper, a carbon fiber reinforced Al matrix composite phase change material with a Si-rich◎Si-poor cladding structure ([Cf×Si-rich]◎EAl-Si cPCM) was prepared by controlling the precipitation behavior of primary Si under electromagnetic stirring, which can realize the self-encapsulation of eutectic Al-Si alloy. The thermal and structural properties in steady state and non-steady state of the [Cf×Si-rich]◎EAl-Si cPCMs were systematically investigated. The results show that the [Cf×Si-rich] shell has a high thermal conductivity of 53.3–100.7 W/m·K at 200 °C~500 °C. With the increase of Si content in initial Al-Si melt, the high-temperature damage tolerance of the [Cf×Si-rich]◎EAl-Si40 cPCM prepared by Al-40Si is 62.8% higher than that of the [Cf×Si-rich]◎EAl-Si25 cPCM prepared by Al-25Si, but the heat storage capacity is decreased by 22.7%. The [Cf×Si-rich]◎EAl-Si30 cPCM prepared by Al-30Si melt is considered to have the best comprehensive property. Under the non-steady working condition, the [Cf×Si-rich]◎EAl-Si30 cPCM exhibited excellent structural stability and great phase change characteristics (0.3% fluctuation of the melting latent heat and 1.4% fluctuation of the phase change temperature). This work offers new self-encapsulation strategy for extending the application process of Al matrix PCM to the field of high-temperature thermal energy storage.

PCM Thermal Storage Technology and its Military Applications: A Review

Abstract: Phase Change Materials (PCM) are the most promising and budding technology in the field of Thermal Energy Storage (TES) and thermal comfort in buildings. PCMs are being extensively used and researched across the world for the improvement of thermal performance of buildings by smoothening temperature peaks as well as act as a power-saving tool in buildings where heating or cooling is required. PCMs can absorb and release heat or cold energy when it undergoes a phase change from solid to liquid and vice versa. This process takes place at a constant temperature absorbing a huge amount of energy in form of latent heat of fusion or vaporization in comparison to sensible heat which is absorbed with an increase of temperature. India’s frontiers stretch across a few of the world’s extreme terrains having extreme climatic conditions varying from extremely hot climates on western borders to extremely cold climates on its northern extremities. The unique characteristic of PCM based latent heat storage system can be utilized in lightweight prefabricated PUF insulated shelters used by security forces, to increase its thermal resistance or store excess heat from intermittent renewable sources during daytime for use during the night, thereby helping in maintaining a comfortable temperature inside the shelters. The PCMs characteristic of absorbing and releasing heat at a constant temperature can be effectively utilized in various other applications where thermal management or temperature control is of importance. It can also help in enhancing the mission reliability of its vehicles, equipment, plant, and electronic instruments when deployed in areas having extreme temperatures. In the present work, a broad study has been conducted based on recent progress and research across the world on PCM technology and its probable applications in the defense sector. The aim is to highlight the potential of PCMs to be utilized for the enhancement of the performance of manpower and critical equipment deployed under extreme climatic conditions encountered by the Security forces. Keywords: Phase Change Material, Thermal Energy Storage, Latent Heat Storage, Military Applications, Security forces, Indian Armed forces.

Temperature profile of PCM and HTF in packed bed storage during the process of solidification in spherical capsules

Amassing of cold energy is a foremost area in the field of thermal energy storage. The storing of cold thermal energy in a phase shift material is an art of solidification. The following experimentation depends on the domain of packed bed storage in which the 74mm spherical nodules of HDPE material whose fill volumes is around 90% is been solidified in a packed bed. The solidification curves and the HTF temperature profile concerning various set conditions have been analysed. The results revealed that layer 1 takes a minimum time to attain a lower temperature when compared with other reference layers. The results reveal that when the HTF temperature is brought from -6 to -9°C this trend is also maintained in the HTF temperature profile and found to be rapidly decreasing. Hence it is concluded that the inlet temperature of HTF plays a significant role during the process of solidification.

Cellulose nanofiber/melanin hybrid aerogel supported phase change materials with improved photothermal conversion efficiency and superior energy storage density

Organic phase change materials (PCMs) have been widely applied in thermal energy storage fields due to their good structural stability, high energy storage density, adjustable phase change temperature and non-toxicity. However, the poor solar-thermal conversion performance and structure stability restrict the large-scale application of organic PCMs. Herein, novel PCM composites (CMPCMs) with good structural stability, improved photothermal conversion efficiency, and superior energy storage density were successfully synthesized by impregnating poly (ethylene glycol) (PEG) into cellulose nanofibers/melanin hybrid aerogel. The three-dimensional (3D) aerogel framework had good shape stability and strong encapsulation ability, which inhibited the leakage of PEG and enhanced the shape stability of the synthesized PCM. The differential scanning calorimetry (DSC) results showed that CMPCMs exhibited relatively high melting enthalpies ranging from 168.3 to 175.9 J/g, and the introduction of melanin almost unchanged the energy storage density of the synthesized PCM composites. Simulated sunlight tests revealed that the introduction of melanin significantly improved the photothermal conversion efficiency of CMPCMs (from 47.2 to 85.9%). The thermal cycling test and thermogravimetric analysis showed that CMPCMs possessed excellent thermal stability and good encapsulation ability. In conclusion, the synthesized CMPCMs showed great potential in the practical utilization and storage of solar energy.

Combined effects of composite thermal energy storage and magnetic field to enhance productivity in solar desalination

The conventional solar still is limited to a daily yield of approximately 2–3.5 kg/m2/day. To increase the yield, this study investigates experimentally the combined effects of latent and sensible energy storage together with magnetization. Paraffin and novel high-thermal conductivity nanomaterial (graphite plate) were used as latent and sensible heat storage materials, respectively. There was an overall increase of 62% and 235% in the daytime and night-time yield, respectively, giving a total yield of 5.5 kg/m2/day compared to 3.4 kg/m2/day for a conventional still. Enviro-economic parameters like emissions, CO2 mitigation and carbon credit (CC) earned were also investigated. Energy matrices analysis and water quality checks were performed to estimate the energy-payback time, life cycle conversion efficiency (LCCE) and purity of desalinated water. The cost per liter of freshwater was found to be 3.7% cheaper than for a conventional still and 69% cheaper than bottled water in India. Over a 30 year period, 40.3 Tonnes of CO2 will be mitigated contributing a CC and LCCE of $402 and 0.52, respectively. The proposed modified still is recommended as a substitute for conventional stills and stills with simple energy storage.

Heat transfer enhancement in latent heat thermal energy storage unit using a combination of fins and rotational mechanisms

Due to the rapid growth of research in the field of thermal energy storage (TSE), optimization of these systems (especially the method of latent heat thermal energy storage (LHTES)) is significantly investigated in last couple of years. Using fins is one of the conventional ways to increase the heat transfer rate. In the present study, a numerical simulation is conducted to assess the combined effects of applying both fins and rotation. This study investigates the solidification and melting process by using the enthalpy porosity method. Solidification and melting time and heat transfer rate are two essential parameters in the operating of LHTES heat exchangers. Results show that rotational speed has a positive effect on the operating system, with a reduction in time for the solidification process of 83.21% and the increased heat transfer rate of 12.89 W. Additionally, increased rotational speed has a direct relationship to the improvement of the heat transfer ratio by 2.45 and 3.87 times in the charging and discharging process, respectively.

Study on Modification of Room Temperature Vulcanized Silicone Rubber by Microencapsulated Phase Change Material

Ice coating seriously threatens the safe operation of the power system. Some electrical equipment made of vulcanized silicone rubber also suffered from ice hazards. Vulcanized silicone rubber has poor thermal insulation properties under low temperatures, which causes its surface to freeze quickly. To improve its thermal insulation properties, room temperature vulcanized silicone rubber (RTV) was mixed with microencapsulated phase change material (MEPCM) to increase its latent heat. As the ambient temperature decreases, the latent heat in the modified RTV will be released to keep it around the phase transition temperature (PCT). MEPCM having a silica shell and n-tetradecane nucleus are prepared by in-situ interfacial polymerization. Tests analysis shows that the freezing temperature of MEPCM is 2.3°C, and the latent heat is 130.8 J/g. The ratio of MEPCM to RTV, latent heat and PCT determine the thermal insulation performance of silicone rubber at low temperatures. When the mass ratio of microcapsules and silicone rubber is 1:5, the modified RTV can keep the temperature above 0°C for about 6 minutes at an ambient temperature of -10°C. The addition of MEPCM reduces the self-cleaning ability of RTV, but the self-cleaning coefficient is still greater than 85%, showing has a good self-cleaning ability. MEPCM with PCT close to 0°C has certain research significance in the field of anti-icing and thermal energy storage.

Novel flexible polyurethane/MXene composites with sensitive solar thermal energy storage behavior

In this study, the novel flexible polyurethane/MXene solid–solid phase change materials (SSPCMs) with improved solar-to-thermal conversion efficiency and mechanical strength were constructed using polyethylene glycol (PEG)/MXene blends and hexamethylene diisocyanate trimer (HDIT) through an efficient polyurethane reaction. The obtained SSPCMs exhibit leakage-proof properties, which can be attributed to the formed three-dimensional crosslinking network by HDIT and PEG. The melting phase transition enthalpy and relative enthalpy efficiency of SSPCMs with 2.0 wt% MXene (2.0-MPH) are 127.97 J/g and 76.96%, respectively, moreover, its solar-to-thermal conversion efficiency (θ) is as high as 90.45%. After 200 times thermal cycling and 50 times light cycling, its enthalpy values and θ value remained almost unchanged, indicating that the obtained 2.0-MPH possessed excellent solar-to-thermal reliability and cycle reusability. Simultaneously, the great comprehensive mechanical properties have further broadened the application of SSPCMs in the field of solar thermal energy storage.

Bionic topology optimization of fins for rapid latent heat thermal energy storage

The latent heat storage (LHS) technique has been widely applied in various thermal energy conversion and management fields. However, LHS device suffers from very slow heat storage/release process. Here, a bionic topology optimization method is proposed to enhance thermal storage/release performances considering different objective functions and heat transfer mechanisms. Taking minimized capacity dissipation as the optimization function and considering natural convection, the optimized fin structure can reduce the melting and solidification time by 93% and 80%, respectively. The underlying mechanism can be attributed to better synergy between flow and heat transfer. Moreover, the fractal dimension of optimized fins is similar to the leaf structure. This research provides a new route for the design of high performance LHS devices, and promotes the application of bionics in thermal energy storage fields.

Effect of perforated fins on the heat-transfer performance of vertical shell-and-tube latent heat energy storage unit

Annular finned tube has been widely employed in the latent heat thermal energy storage (LHTES) field to accelerate the charging/discharging process. Nevertheless, the obstruction of fins on the liquid flow restrains natural convection development in the LHTES unit. In the present work, we propose several three-dimensional perforated-fin models to enhance the heat storage performance. The perforated fin structure is studied in detail by varying the hole diameter and hole location. It is observed that the two hole-parameters have significant effects on the charging performance of the LHTES unit. With the increase of the hole diameter, natural convection is reinforced, but thermal conduction is weakened simultaneously. Besides, the farther the hole is from the fin root, the stronger the thermal conduction is, while the weaker the natural convection is caused. The findings reveal that although the perforated fin is conducive to enhancing natural convection, it weakens thermal conduction compared with the solid-fin model. There is an optimal perforated-fin structure for achieving the maximum enhancement on the heat transfer. The structure, in which the hole diameter is 3 mm, hole location is L = 8 mm, and hole number is 6, reduces the complete melting time by 5.49% compared with the solid-fin model, and the heat storage capacity is commendably enhanced by 0.21%. Consequently, the perforated fins are worthy of being employed in the annular finned tube LHTES unit.

Thermal energy storage system applicable to vehicles

The paper presents the state of the art for thermal energy accumulators using the latent heat phase change usable in cars with either internal combustion engine or electric. The new materials with high storage capacity are presented and the most important achievements in this field of thermal energy storage on vehicles. The case study presented in the paper brings some information necessary for the development of thermal accumulators, with phase change materials, showing the important parameters and characteristics and what values they must have (e.g.: required and accumulated energy; charging and discharging time; latent heat, geometric characteristics). The paper presents a possible classification of these types of batteries, thus facilitating the development of products specific to the applications in which they are included. The work will continue with numerical and experimental studies on models developed based on the case study described here. If at present, in the case of electric cars, a reduction of approx. 20% of electricity was obtained by implementing thermal batteries with phase change material, then studies or research become necessary to accelerate their development on an industrial scale in competitive economic conditions.

Researchers perception regarding socio-technical approaches implementation in their own research. Thermal energy storage researchers as example

The enhancement and the understanding of the societal dynamics in the energy systems within transition entails the inclusion of innovative policy and research strategies. This inclusion raises several questions that change profoundly the nature of the research and innovation endeavour, questions that have not been sufficiently explored in the literature. These questions are, among others, the complexities an scope of socio-technical integration or the emergence of new roles and patterns such as user-inspired innovations or community innovations. Based on the assumptions of the responsible-based approaches advocating to energy system actors to collaborate sharing responsibility and the benefits that perspectives integration brings in the development of proactive and archivable energy and climate policies, this study analyses a group of researchers within the field of thermal energy storage (TES) for renewable energy applications, for the purpose of evaluating their perception regarding to the inclusion of alternative policy proposals and collaborative research strategies. The proposed methodology was based on the use of the common theoretical backgrounds of socio-technical transition for the construction of an responsibility-based approach and the proposal of a survey tool for gathering the empirical evidence from researchers opinions. The survey data was collected from a representative group of researchers (33 countries, 215 targeted researches completing the surveys at 31% with a final N = 72). Findings shows willingness to include citizens as beneficiaries but not as participants of research decisions, the prevalence of the use of social sciences to increase the acceptance of technology and remarkable unawareness regarding collaborative research strategies. This paper brings an important contribution for the selected researchers that can be extrapolate to other energy communities since illuminates the possibility of adapting and asses TES to include new patterns and new governance strategies based in RRI.

Thermal analysis and heat capacity study of even-numbered fatty alcohol (C12H25OH-C18H37OH) phase-change materials for thermal energy storage applications

Fatty alcohols (FAs) have been widely studied as typical phase-change materials for their high latent heat, low undercooling, non-toxicity, and low cost in thermal energy storage applications. The thermal properties, especially the heat capacity, play a vital role in designing-related energy storage techniques. However, there are few studies on the thermal properties of FAs systematically investigated in a wide temperature region, which greatly limit their application in thermal energy storage field. In this study, the thermal properties of even-numbered FAs (C12H25OH-C18H37OH), such as thermal stability, thermal conductivity, phase transition temperature, and enthalpy have been systematically investigated using a combination of various thermal analysis and calorimetry methods. The corresponding thermodynamic functions such as the standard molar heat capacity, entropy, and enthalpy at 273.15 K and 0.1 MPa have been calculated based on the heat capacity curve fitting. Most importantly, the heat capacities of 1-tetradecanol and 1-hexadecanol are reported for the first time in the wide temperature range of 1.9–370 K. Furthermore, by fitting the heat capacities of FAs, a function of molar heat capacities (Cp) related to the number of carbon atoms (n) and temperature (T) has been established, which can express the heat capacity of FAs between C12H25OH and C22H45OH reasonably in the temperature region of 50–240 K. This work provides accurate and systematic thermodynamic data of FA samples for the future study on their thermodynamic property and related processing design of thermal energy storage application.

Solid-solid phase-change materials with excellent mechanical property and solid state plasticity based on dynamic urethane bonds for Thermal Energy Storage

Solid-solid phase change materials (SSPCMs) with small volume change and leak-proof characteristic during the whole process of phase change play a vital role in development of PCM for thermal energy storage (TES). However, the non-recyclability of the materials due to their permanent cross-linking networks limited their practical application. Herein, a dynamic urethane bond cross linked SSPCM with PEG as phase change functional segments was successfully fabricated which was in solid state even at 130°C.Meantime, it exhibited excellent solid-state plasticity, resulting from dynamic urethane bond exchange. Moreover, the dynamic behavior of urethane bond in SSPCMs was firstly investigated. The topology freezing transition temperature (Tv) is about 113°C and the relaxation activation energy of SSPCM is calculated to be about 90 kJ/mol. The crystalline PEG endows SSPCM with high enthalpy value (reached up to 85 J/g), meantime, the cross-linked structure endows SSPCMs with remarkable mechanical flexibility (possess ultra-stretchability of 600%), thermal reliability and chemical stability. The combined thermal storage ability, appealing recyclability and flexibility endow the SSPCM promising application in the field of TES.

Molten salt in-situ exfoliation of graphite to graphene nanoplatelets applied for energy storage

The in-situ exfoliation of graphite in molten NaCl–KCl salt at 750 °C yielded a homogeneous composite, from which graphene nanoplatelets (GnP) could be easily and completely separated. The GnP product displayed relatively large-size particles (12 μm, TEM, SEM, laser diffraction) and low defect density (Raman, XPS), indicating the superiority of the molten salt exfoliation approach over the conventional liquid-phase approach for producing GnP. The mechanism of GnP production involves the formation of cavities in the molten salt, such that impregnation of the graphite by the molten material facilitated gentle exfoliation of the graphite to GnP. The methodology for the in-situ production of GnP in molten salt is highly applicable in the field of thermal energy storage, where molten inorganic salts are one of the most widely used heat-transfer fluids, such as phase-change materials. In graphite-GnP-salt composite, the thermal conductivity is enhanced by more than one order of magnitude compared to the neat salt matrix, which is essential for efficient thermal energy storage applications.