Cold Energy Storage Research Articles

High‐Performance Charging Method for Cold Energy Storage Using Foam Freezing

Phase change cold energy storage can effectively stabilize the peak value of the power grid, but the cold energy charging rate of phase change material decreases seriously which will reduce the energy efficiency of the system. The cold energy charging performance can be effectively improved by foam freezing, and the foam freezing model is proposed to explore the influence factors and the advantages of this method. Foam freezing is compared with other methods based on the novel concept of cold energy charging coefficient which is carried on the analogy to heat transfer coefficient. It is found that the cold energy charging rate of foam freezing are exponential functions of the height based on e. The foam cold energy charging coefficient is affected by the superposition of convective heat transfer intensity and bubble terminal velocity. The technical path of increasing the cold energy charging coefficient by continuously reducing the bubble size is not feasible. When foam freezing at the radius of 0.6 mm, the cold energy charging coefficient is 237.1 W m−2 K−1, the water equivalent height is 18 mm, and it is the most economical. Foam freezing has advantages over the ice ball and ice‐on‐coil in cold energy charging performance.

Characterization and Reliability of Caprylic Acid-Stearyl Alcohol Binary Mixture as Phase Change Material for a Cold Energy Storage System.

This study reports the in-depth investigation of the thermophysical properties and thermal reliability of caprylic acid-stearyl alcohol (CA-SA) eutectic phase change material (PCM) for cooling applications. The phase diagram of CA-SA showed a eutectic point at a 90:10 molar ratio. The onset melting/freezing temperature and latent heat of fusion of caprylic acid-stearyl alcohol from the differential scanning calorimetry (DSC) were 11.4 °C/11.8 °C and 154.4/150.5 J/g, respectively. The thermal conductivity for the prepared eutectic PCM in the solid phase was 0.267 W/m.K (0 °C), whereas, in the liquid phase, it was 0.165 W/m.K (20 °C). In addition, the maximum relative percentage difference (RPD) marked at the end of 200 thermal cycles was 5.2% for onset melting temperature and 18.9% for phase change enthalpy. The Fourier transform infrared spectroscopy (FT-IR) result shows that the eutectic PCM holds good chemical stability. Corrosion tests showed that caprylic acid-stearyl alcohol could be a potential candidate for cold thermal energy storage applications.

Synthesis and Characteristics of Microencapsulated Decanol with TiO2 Shell as Composites for Cold Energy Storage

A novel microencapsulated phase change materials for cold energy storage was synthesised through sol-gel means using decanol as phase change material and titanium dioxide (TiO2) as encapsulated material. The micromorphology and composition of microcapsules were observed by field emission scanning electron microscope (FE-SEM), Fourier transformation infrared spectrometer (FT-IR).Using differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA) thermal properties of microcapsules were characterized. Results of FE-SEM and FT-IR indicated that micro sized decanol droplets were encapsulated with TiO2 to form the well-developed core-shell structure, which was only physical coating between them. Furthermore, the chemical and thermal stability of the microcapsules were improved and the inflammability of the microcapsules was lowered using TiO2 as shell material. The DSC result of the desirable ones melt at 3.87 ℃ with a latent melting enthalpy of 61.12 J·g-1 and solidified at – 1.32 ℃ with a latent solidification enthalpy of 59.54 J·g-1. In general, the prepared microcapsules have potential for cold energy storage.

Solar-Hybrid Cold Energy Storage System Coupled with Cooling Pads Backup: A Step towards Decentralized Storage of Perishables

Post-harvest loss is a serious issue to address challenge of food security. A solar-grid hybrid cold storage system was developed and designed for on-farm preservation of perishables. Computational Fluid Dynamic analysis was performed to assess airflow and temperature distribution inside the cold chamber. The system comprises a 21.84 m3 cubical cold storage unit with storage capacity of 2 tonnes. A hybrid solar system comprising 4.5 kWp PV system, 5 kW hybrid inverter, and 600 Ah battery bank was used to power the entire system. A vapor-compression refrigeration system (2 tonnes) was employed coupled with three cooling pads (filled with brine solution) as thermal backup to store cooling (−4 °C to 4 °C). Potatoes were stored at 8 °C for a period of three months (May 2019 to July 2019) and the system was tested on grid utility, solar, and hybrid modes. Solar irradiation was recorded in range of 5.0–6.0 kWh/(m2 × d) and average power peak was found to be 4.0 kW. Variable frequency drive was installed with compressor to eliminate the torque load and it resulted about 9.3 A AC current used by the system with 4.6 average Coefficient of Performance of refrigeration unit. The average energy consumed by system was found to be 15 kWh with a share of 4.3 kWh from grid and 10.5 kWh from solar, translating to 30% of power consumption from grid and 70% from solar PV modules. Overall, cold storage unit efficiently controlled total weight loss (7.64%) and preserved quality attributes (3.6 ⁰Brix Total soluble solids, 0.83% Titratable acidity, 6.32 PH) of the product during storage time.

Techno-economic study of nuclear integrated liquid air energy storage system

The significant increase of renewable energy source is expected to induce stability issue of electric grid due to the intermittency of renewable energy. The challenge of intermittency is making energy storage system more important. Among the grid-scale energy storage systems, a Liquid Air Energy Storage System is increasingly popular with its high energy density, long expected service lifetime, less operation and maintenance cost, and less geographical constraint. At the same time, flexibility of nuclear power plant is becoming more important with higher penetration of renewable energy sources. However, load-following operation not only causes safety issues on the fuel integrity, but also leads to economic deterioration of nuclear power plant. In this study, the new concept is suggested by mechanically integrating nuclear steam cycle and liquid air energy storage system to achieve high flexibility and economy of a nuclear power plant. At off peak hour, nuclear energy is stored by bypassing steam from nuclear steam cycle to external steam turbine which mechanically connected to air compressor in the liquid air energy storage system. Air is compressed by air compressor and liquefied by cold energy storage system. At peak hours, the stored energy is recovered by evaporating and expanding. The thermodynamic and economic analyses are conducted on standalone liquid air energy storage system and nuclear integrated liquid air energy storage system to further examine the benefits of the proposed system. The results show that the round-trip efficiency of the proposed system is around 51% and the energy density is 116 kWh/m3. The round-trip efficiency is competitive and the energy density is superior to other grid-scale energy storage system. Also, the integration improves the capacity factor of nuclear power plant by 3%p. The Levelized Cost of Electricity shows $219.8/MWh for standalone liquid air energy storage system and $182.6/MWh for nuclear integrated liquid air energy storage system, reducing 17% of the standalone systems’ cost. The results show that the proposed concept can achieve better economy than using standalone liquid air energy storage system as well as other energy storage systems. In conclusion, the proposed nuclear integrated liquid air energy storage system has very good potential to become a competitive energy storage option and can assist to stabilize the future electricity grid with high reliance on renewable energy.

High heat transfer performance of foam freezing in phase change cold energy storage process

Phase change material (PCM) has high energy storage density, but the cold energy charging rate of PCM decreases seriously with the increase of frozen thickness. The foam freezing produced by cold air flow can sharply increase the freezing rate. This research attempts to establish a theoretical model to quantify the heat transfer performance of foam freezing. The internal structure of the foam was obtained by experiment. The heat transfer process of single bubble was simulated by FLUENT, and analytical models for single bubble and foam were established. It was found that the tangent bubble array had the same heat transfer effect as the actual foam in freezing, and the bubble temperature variation obeyed the exponential distribution. The radius of more than 50% bubbles was about 2.5 mm, and the convective heat transfer coefficient in the bubble was 65 W/(m2. K). The maximum completed heat transfer rate of foam freezing was 688 kW/m3, when the air temperature was -20 °C. Foam freezing was compared with common ice storage structures, and was found had an order of magnitude higher than those structures in the heat transfer coefficient of unit volume.

Hybrid artificial ground freezing as a sustainable solution for containing hazardous-waste in critical environmental projects

Permafrost degradation represents a severe challenge for mining operations in Northern Canada. The foundations of the infrastructures rely on the steadiness of the permafrost. Accordingly, changes in permafrost durability may contribute to destructive failures if not appropriately preserved. Thus, it is of the greatest interest to maintain the integrity of permafrost in the affected areas. One of the safest methods to sustain permafrost is by employing artificial ground freezing (AGF). The associated AGF system, in contrast, is usually designed to operate continuously to sustain permafrost stability. This non-stop mode of operation requires intensive energy consumption. Therefore, an innovative, reliable operational technique is crucial to ensure permafrost sustainability. This paper presents and illustrates a novel concept of a ‘renewable energy’-based AGF system, with zero human-generated energy input, comprising a closed-loop thermosyphon coupled with a cold-energy storage tank that could be filled with a phase-change material (PCM). A mathematical model has been derived, validated, and exploited to simulate the AGF under various operating and design parameters. The results suggest that the employment of the coupled system of closed-loop thermosyphon and cold-energy storage unit reduces overall power consumption while maintaining the permafrost's thickness, notably during the summer.

An exfoliated montmorillonite as the nanosheet nucleating agent in the subzero phase change material

Cold energy storage technologies with phase change materials (PCMs) have received increasing attention, but there is still a great vacancy for PCMs that can be applied below 0°C due to high supercooling degree of aqueous solution. In this work, the nanosheet dispersion phase change materials (NDPCMs) containing the ethylene glycol (EG) aqueous solution and the modified montmorillonite (MTT) at different mass fractions were prepared, in which the modified MTT prepared by surface modification of zwitterionic surfactant and polymer quaternary ammonium salt under high speed shearing could be steadily dispersed due to the combination of charge and steric effects. And the modified MTT could be used as the nanosheet nucleating agent to effectively suppress the supercooling as well as improve the thermal properties of the PCM. The NDPCM with 0.4 wt% modified MTT had an appropriate phase transition temperature of -5.0°C, higher latent heat of fusion of 189.96 kJ•kg−1, and there was no supercooling in the test of step cooling curves. Moreover, the NDPCM still showed excellent dispersion stability after 50 thermal cycles. These results indicate that the NDPCM has practical application value in cold energy storage.

A phase change material (PCM) based passively cooled container for integrated road-rail cold chain transportation – An experimental study

• An experimental study on a PCM-based passively cooled container for cold chain. • The internal temperature can be maintained 2~8 °C uniformity for 94.6 h. • The system COP was 1.84, with an energy-saving by 86.7% than diesel-powered reefer. • The cost and emission reduced by 91.6% and 78.5% than diesel ones, respectively. This paper reports a phase change material (PCM) based passively cooled container for integrated rail-road cold chain. It was equipped with cold energy storage plates containing the PCM. A separate charging facility was built to charge the plates. Four kinds of fresh vegetables and fruits were used for integrated rail-road transportation. The charging time and efficiency, the internal temperature and relative humidity of the container during delivery, as well as the coefficient of performance (COP) of the system, were obtained. The results were compared with a diesel-powered reefer in terms of energy consumption, operation costs and environmental impact. The quality of products before and after the cold transportation was also compared. The results showed that the new container had a discharging time of up to 94.6 h and the system COP could be as high as 1.84. The results also demonstrated that the energy consumption, the operational cost, and the emission were reduced by 86.7%, 91.6%, and 78.5%, respectively.

Experimental Investigation on Enhanced Energy Storage Characteristics of Spherically Encapsulated 1-Decanol/Expanded Graphite Composite for Cold Storage System

The low solidification temperature (0°C), sporadic nucleation behaviour and supercooling phenomenon of ice are the major factors affecting the energy storage efficiency of an ice-based cold thermal energy storage system (CTESS). Due to the non-supercooling nature and high solidification temperature (~4.1°C), 1-Decanol-Expanded graphite composite (CPCM) is proposed as a prospective replacement for ice in CTESS. The CPCM was macro encapsulated inside the various diameter (42, 51 and 64 mm) spherical enclosures (S.Es), and its energy storage performance was studied at different wall temperatures (Tw) for charging (0,-3 and -6°C) and discharging (10, 13 and 16°C). It is found that the latent heat can be stored in CPCM even at a higher wall temperature (-3°C), which is not possible in the case of ice. To freeze the same mass of 1-Decanol at Tw = -6°C, the CPCM filled 51 mm S.E requires 85.37% lower time than that of PCM filled S.E. Based on experimental results, -3 and 13°C is found as an optimum wall temperature for charging and discharging, respectively. The charging and discharging rates increase with diameter. Besides, in a 51 mm S.E, the time required to store (Tw = -3°C) and recover (Tw = 16°C) a stated amount of energy in CPCM is 81.27%, and 76.45% lower than that of PCM, respectively. CPCM has superior phase change and energy storage characteristics. Therefore, the use of CPCM in CTESS ensures effective storage and recovery of cold energy.

A modeling study of sessile water droplet on the cold plate surface during freezing under natural convection with gravity effect considered

Freezing of water droplet is widely seen and important in the fields of aerospace, cold energy storage, and power production. To investigate the freezing process of a sessile water droplet on a horizontal cold plate, a theoretical model was developed. Different from previously reported models, the effects of supercooling and gravity on the physical properties and the water droplet profile are both considered, respectively. This model is validated with the experimental data of two parameters, including the freezing time and the freezing front radius. The results indicate that the deviation of freezing time is decreased from 7.69% to 0.17%, while the accuracy improved by 7.52%. The average deviation of the freezing front radius is decreased from 142.90 μm to 57.94 μm, with the accuracy improved by 59.46%. At the freezing stage, the appearance of the dynamic growth angle contributes to the less deviation of the freezing front radius. The eccentricity of droplet shape decreases from 0.45 to 0.03, with the eccentricity decreased by 93.45%. The temperature change rates inside a droplet show a gradually decreasing tendency, and the temperatures at different droplet locations present different limiting values. The findings of this study are beneficial for understanding droplet solidification process as well as new technologies for refrigeration, deicing, and defrosting.

Experimental investigation of a multi-kWh cold storage device based on phase change materials

An innovative technology to store cold energy for civil applications and based on Phase Change Materials (PCM) is presented and experimentally validated. The storage tank is coupled to a hydronic chiller in a Heating, Ventilation and Air Conditioning (HVAC) system with the aim of optimizing its performance shaving the cold energy peaks required by the users. The system is composed of a tank containing a heterogeneous mixture of an organic PCM and water. The two liquids are immiscible and water is stratified in the lower part of the tank, PCM in the upper part. A coaxial water-water heat exchanger is immersed in the PCM volume. Water stream from HVAC system (primary circuit) and the water contained in the storage tank (secondary circuit) are fed to the heat exchanger. Then, the secondary circuit water is sent back to the top of the tank through nozzles and the water drops descend by gravity into the volume of PCM. By this way, the PCM is solidified uniformly and quickly, and cold energy is stored in the form of latent heat. In this paper, a prototype able to store up to 25 kWh of energy through PCM solidification is presented. A detailed testing campaign is carried out and an optimized strategy for the cold energy storage system operation is proposed. The experimental results demonstrates that the tank is fully charged in 2.5 h and discharged in 1.6 h.

Performance enhancement of cold energy storage using phase change materials with fumed silica for air‐conditioning applications

digitalData = {"site":{"ip":"181.215.96.38","environment":"LIVE","website":"onlinelibrary.wiley.com","websiteCode":"pericles","serverDate":"2022-09-28"},"identities":[{"type":"SmartGroupUser","uuid":"b238ab85-6bb4-49e4-84ca-a0d9f3ee5a35"},{"type":"SmartGroupUser","uuid":"eabce89b-65c2-4a09-ab7c-bd2b3fea2f10"},{"type":"RegionUser","uuid":"3c5060a1-6620-438f-862b-902a4d4cd4ac"},{"type":"BasicGroup","uuid":"e623deab-c83b-41e3-84a2-d9f1d46c5f17"},{"type":"SmartGroupUser","uuid":"a86d27d2-6bcd-4b94-bca5-fe16f4882855"},{"type":"SmartGroupUser","uuid":"da88d808-3f7b-4bde-9210-10862b6d121b"},{"type":"SmartGroupUser","uuid":"8c72a733-117a-4bc9-a682-13475f13e6a3"},{"type":"SmartGroupUser","uuid":"756fc162-8722-461f-a077-ebffec4f4fae"},{"type":"SmartGroupUser","uuid":"cf9c85b9-7f3b-4309-aeaa-c41669cabe3b"},{"type":"SmartGroupUser","uuid":"db8b8d10-1aed-4809-b3ee-70938c569014"},{"type":"SmartGroupUser","uuid":"cdce41c2-a8de-4a64-a4d9-a85caaaa2314"},{"type":"SmartGroupUser","uuid":"7a2a316d-5a37-4ccd-afdb-737bfb863a48"},{"type":"SmartGroupUser","uuid":"39f911ce-44b6-4dba-9978-8b2e947a8eb0"},{"type":"SmartGroupUser","uuid":"97587ffd-dcb4-4cb5-9986-a8ce611532bd"},{"type":"SmartGroupUser","uuid":"a46a154d-979f-41ba-b459-fd34df5c071f"},{"type":"SmartGroupUser","uuid":"b7acda8c-ce18-451b-a68d-e14b72f9b5b8"},{"type":"SmartGroupUser","uuid":"055a2bdd-861f-4fa7-bd49-9773db7e0e3e"},{"type":"InstitutionUser","uuid":"1e38fbd4-113a-46cd-87fa-4155721046f6","customerRecords":[{"customerDomain":"ALM-CU","customerNumber":"CORE00000117448"}]},{"type":"BasicGroup","uuid":"197fe835-5b5f-4f4e-b8e9-a74d68491a84"},{"type":"SmartGroupUser","uuid":"b2dbfe27-ecae-4bb6-bb0d-d75e5caa3762"},{"type":"SmartGroupUser","uuid":"1a6297fb-6679-4882-a4c2-fdd124624edf"},{"type":"SmartGroupUser","uuid":"8032f17e-5050-4fb4-9c40-e1f6875d5c2b"},{"type":"SmartGroupUser","uuid":"ab743440-628f-4964-9216-9983ad3beadf"},{"type":"RegionUser","uuid":"bba2c3f6-9ab6-4436-ab12-515eeb5dc999"},{"type":"SmartGroupUser","uuid":"a4187e00-f28e-4754-9a0f-1eb306fb0679"}],"publication":{"item":{"title":"Performance enhancement of cold energy storage using phase change materials with fumed silica for air‐conditioning applications","doi":"10.1002/er.6903","access":"no","earliestDate":"2021-06-11","formats":["Abstract","First page image","Full text","PDF","References","AM pdf"],"topics":[{"taxonomyUri":"global-subject-codes","topicLabel":"MECHANICAL ENGINEERING","topicUri":"me"},{"taxonomyUri":"global-subject-codes","topicLabel":"Materials for Energy Systems","topicUri":"msl0"},{"taxonomyUri":"global-subject-codes","topicLabel":"Hydrogen, Batteries & Fuel Cells","topicUri":"eg32"},{"taxonomyUri":"global-subject-codes","topicLabel":"General Energy","topicUri":"eg00"},{"taxonomyUri":"global-subject-codes","topicLabel":"Solar Energy & Photovoltaics","topicUri":"eg34"},{"taxonomyUri":"global-subject-codes","topicLabel":"Energy Reduction","topicUri":"ce58"},{"taxonomyUri":"global-subject-codes","topicLabel":"Renewable Energy","topicUri":"eg30"},{"taxonomyUri":"global-subject-codes","topicLabel":"General & Introductory Electrical & Electronics Engineering","topicUri":"ee00"},{"taxonomyUri":"global-subject-codes","topicLabel":"General & Introductory Mechanical Engineering","topicUri":"me00"},{"taxonomyUri":"global-subject-codes","topicLabel":"Constructional Physics","topicUri":"ce50"},{"taxonomyUri":"global-subject-codes","topicLabel":"MATERIALS SCIENCE","topicUri":"ms"},{"taxonomyUri":"global-subject-codes","topicLabel":"ENERGY","topicUri":"eg"},{"taxonomyUri":"global-subject-codes","topicLabel":"CIVIL ENGINEERING & CONSTRUCTION","topicUri":"ce"},{"taxonomyUri":"global-subject-codes","topicLabel":"ELECTRICAL & ELECTRONICS ENGINEERING","topicUri":"ee"},{"taxonomyUri":"fundref-funders","topicLabel":"UK Research and Innovation","topicUri":"100014013"},{"taxonomyUri":"fundref-funders","topicLabel":"Engineering and Physical Sciences Research Council","topicUri":"501100000266"}]},"group":{"title":"","doi":"10.1002/er.v45.11","access":"no","volume":"45","issue":"11","coverDate":"2021-09-01","topics":[{"taxonomyUri":"global-subject-codes","topicLabel":"MECHANICAL ENGINEERING","topicUri":"me"},{"taxonomyUri":"global-subject-codes","topicLabel":"Materials for Energy Systems","topicUri":"msl0"},{"taxonomyUri":"global-subject-codes","topicLabel":"Hydrogen, Batteries & Fuel Cells","topicUri":"eg32"},{"taxonomyUri":"global-subject-codes","topicLabel":"General Energy","topicUri":"eg00"},{"taxonomyUri":"global-subject-codes","topicLabel":"Solar Energy & Photovoltaics","topicUri":"eg34"},{"taxonomyUri":"global-subject-codes","topicLabel":"Energy Reduction","topicUri":"ce58"},{"taxonomyUri":"global-subject-codes","topicLabel":"Renewable Energy","topicUri":"eg30"},{"taxonomyUri":"global-subject-codes","topicLabel":"General & Introductory Electrical & Electronics Engineering","topicUri":"ee00"},{"taxonomyUri":"global-subject-codes","topicLabel":"General & Introductory Mechanical Engineering","topicUri":"me00"},{"taxonomyUri":"global-subject-codes","topicLabel":"Constructional Physics","topicUri":"ce50"},{"taxonomyUri":"global-subject-codes","topicLabel":"MATERIALS SCIENCE","topicUri":"ms"},{"taxonomyUri":"global-subject-codes","topicLabel":"ENERGY","topicUri":"eg"},{"taxonomyUri":"global-subject-codes","topicLabel":"CIVIL ENGINEERING & CONSTRUCTION","topicUri":"ce"},{"taxonomyUri":"global-subject-codes","topicLabel":"ELECTRICAL & ELECTRONICS ENGINEERING","topicUri":"ee"}]},"series":{"title":"International Journal of Energy Research","doi":"10.1002/(ISSN)1099-114X","access":"no","code":"1099114x","issn":"0363-907X","eissn":"1099-114X","topics":[{"taxonomyUri":"gpt-sitename","topicLabel":"wly.civ.eng.con_000034","topicUri":"wly.civ.eng.con_000034"},{"taxonomyUri":"global-subject-codes","topicLabel":"MECHANICAL ENGINEERING","topicUri":"me"},{"taxonomyUri":"global-subject-codes","topicLabel":"MATERIALS SCIENCE","topicUri":"ms"},{"taxonomyUri":"global-subject-codes","topicLabel":"Materials for Energy Systems","topicUri":"msl0"},{"taxonomyUri":"global-subject-codes","topicLabel":"Renewable Energy","topicUri":"eg30"},{"taxonomyUri":"global-subject-codes","topicLabel":"Constructional Physics","topicUri":"ce50"},{"taxonomyUri":"global-subject-codes","topicLabel":"General Energy","topicUri":"eg00"},{"taxonomyUri":"global-subject-codes","topicLabel":"General & Introductory Electrical & Electronics Engineering","topicUri":"ee00"},{"taxonomyUri":"global-subject-codes","topicLabel":"ENERGY","topicUri":"eg"},{"taxonomyUri":"global-subject-codes","topicLabel":"Energy Reduction","topicUri":"ce58"},{"taxonomyUri":"global-subject-codes","topicLabel":"CIVIL ENGINEERING & CONSTRUCTION","topicUri":"ce"},{"taxonomyUri":"global-subject-codes","topicLabel":"General & Introductory Mechanical Engineering","topicUri":"me00"},{"taxonomyUri":"global-subject-codes","topicLabel":"ELECTRICAL & ELECTRONICS ENGINEERING","topicUri":"ee"},{"taxonomyUri":"global-subject-codes","topicLabel":"Solar Energy & Photovoltaics","topicUri":"eg34"},{"taxonomyUri":"global-subject-codes","topicLabel":"Hydrogen, Batteries & Fuel Cells","topicUri":"eg32"},{"taxonomyUri":"gpt-zonename","topicLabel":"ij-energy-res_ER","topicUri":"ij-energy-res_er"}]}},"page":{"subPage":"Abstract","page":"Article/Chapter View","pageGroup":"Publication Pages","title":"title","errorCode":200}}

Dynamic characteristics analysis of the cold energy transfer in the liquid air energy storage system based on different modes of packed bed

Liquid air energy storage (LAES) is a promising large-scale energy storage technology. The packed bed for cold energy storage (CES) has advantages of environmental protection and low cost. Dynamic characteristics in multiple cycles of the packed bed have great influence on the LAES system, but some available researches only focused on the ideal single-stage CES cycle, and the coupling relationship between the packed bed and the LAES system were seldom involved. Therefore, two-stage packed beds considering the intermittent period between the charging and discharging process and the inevitable cold energy loss is studied. The performance of packed beds with different modes during multiple cycles and dynamic response of the LAES system have been analyzed. The results show that with the continuation of cycles, the temperature distribution in the packed bed gradually evolves. The cumulative effect of the axial heat conduction in the intermittent period and the cold energy loss both lead to the decrease in system efficiencies. Considering both the intermittent period and the cold energy loss, the round-trip efficiency of the LAES system is lower than that of the ideal cycle by 16.8% after the quasi steady state.

Towards high-performance sorption cold energy storage and transmission with ionic liquid absorbents

The shortcomings of conventional working pairs in thermal energy storage and transmission based on absorption cycle have become major obstacles for practical application. Ionic liquids (ILs) are promising alternatives, while only few ILs have been evaluated with enumeration method, by which it is difficult to create a short-term breakthrough. In this study, a prediction framework is established via relating the fundamental thermodynamic properties (absorbing ability and excess enthalpy) with cycle performance (COP and energy density) in order to clarify the maximum potential of this technology and the desirable properties of potentially interesting working fluids. A comprehensive investigation of promising IL absorbents in thermal storage/transmission has been carried out by the framework. Then, theoretical analysis shows that an optimal region with both high COP and high energy density (between 31.00 kJ/mol to 37.00 kJ/mol) could be reached, indicating 57% of improvement in energy density is possible (the highest level at current stage is 23.52 kJ/mol). To pursue the optimal performance, strong affinity between the species and decreasing trend of excess enthalpy during generation are found to be key roles. Such a theoretical framework could be further extended to the fluids design and screening of absorption thermal energy storage/transmission, as well as other related technologies.

Enhancement of the round-trip efficiency of liquid air energy storage (LAES) system using cascade cold storage units

In this research, the variation of round-trip efficiency in a liquid air energy storage system (LAES) is calculated and an optimal configuration is found. The multiple stages of cold energy storage are simulated with several materials that process latent heat at different temperature ranges. The effectiveness in the charging and discharging processes of LAES is newly defined, and its relationship with the round-trip efficiency is examined. According to defined correlation, the effectiveness of the discharging process significantly affects the overall system performance. The round-trip efficiency is calculated for the combined cold energy storage materials of aqueous dimethyl sulfoxide (DMSO) solution, ethanol, and pentane theoretically. The performance of LAES varies depending on the freezing point of the cold storage materials. In particular, when the LAES uses several cold storage materials, those materials whose freezing points are close to room temperature and liquid air temperature should be included in the cold storage materials. In this paper, it is assumed that only latent heat is used for cold energy storage, but for more realistic analyzes, the additional consideration of the transient thermal situation to utilize sensible heat is required. In the case of such a dynamic system, since there is certainly more increased heat capacity of the entire storage system, the volume of the cold energy storage system will be greatly reduced.

ELEKTRİKTE PİK TALEBİ TÖRPÜLEME İÇİN KULLANILACAK FDM-HAVA SOĞUK ENERJİ DEPOLAMA CİHAZI TASARIMI VE OPTİMİZASYONU

Parametric analysis and dimensional optimization study for the melting process of the phase changing material placed in cold energy storage devices have been conducted. Phase changing material, PCM, is used to store the cold energy. A cross-flow tubular PCM-air heat exchanger is used. An electricity peak shaving for a summer day in Antalya for 5 hours (10:00-15:00) is aimed. The cooling load of a room (33 m2) in Antalya is taken as a reference value. A minimum cooling load of 2850 W is supplied throughout 5 hours to maintain the building's comfort temperature. Contrary to the studies handling air velocity constant, it is varied during melting in the present study to satisfy the minimum cooling load. The melting process is analyzed using a numerical model. A computational algorithm is implemented in MATLAB environment. The numerical model is validated for the same conditions and the dimensions with an analytical model presented in the literature. A transient analysis has been employed, and the problem is discretized for the time and space domain. A dimensional optimization algorithm is employed. A parameter “performance ratio/ cooling index”, the ratio of total cooling to fan energy consumption, is defined. Spacing between the tubes giving the maximum performance ratio is sought for aligned and staggered tube bank arrangements using this algorithm. The best performance ratio is obtained at 0.2 m/s initial velocities for both arrangements. In addition, the effect of sizing/arrangement of the tubes, PCM mass, and thermal conductivity of the PCM on the melting characteristics is investigated. As a result of increasing the thermal conductivity from 0.2 W/(m·K) to 0.6 W/(m·K), the performance ratios are raised 4.58 and 3.52 times for aligned and staggered orders, respectively. It is calculated that 10 kg PCM can be saved thanks to enhancing the thermal conductivity of the PCM.

Amassing of Cold Thermal Energy by Utilizing Phase Shift Material: A Review

Storing of cold energy is a predominant area in the cold thermal energy storage system in which the PCM plays a major role in hosting this energy storage process. This study fetches an encyclopedic review based on the current and erstwhile research in the field of cold energy storage using PCM. This dissertation provides an expansive view of the PCM solidification with the methodology of reducing the sub-cooling with the ramping up of heat flow rate besides of variegated nano-particulate and with protrusions. The effect of the fill volume of PCM in solidification is also delineated and how the size and material of PCM containment plays a role in solidification is also scrutinized and eventually, the application area of PCM cold storage is also explored.

Hydrates for cold energy storage and transport: A review

• Energy demand and CO 2 emissions from space cooling have been increasing remarkably. • Semiclathrate hydrate proposed as a sustainable PCM for cold energy storage and transport. • A comprehensive review on thermophysical, kinetic and rheological properties. • State-of-the-art cooling applications proposed based on semiclathrate hydrate technologies. The energy demand for space cooling has more than tripled for the past thirty years and was responsible for emissions of about 1 Gt CO 2 annually. The ever-increasing energy demand for cooling has posed a demanding question on improving the energy efficiency of cooling processes. On the other hand, with the growing global demand on LNG, cold energy released from LNG terminals has been growing to a historical high at 6.6 × 10 14 kJ in 2017. Thus, there is a strong need to search for a suitable phase change material (PCM) best utilizing the cold energy released from the production sectors for storage and transport to the needed sectors. Among all the PCMs, semiclathrate hydrates (SCHs) with a suitable phase change temperature (5–27 °C) and high latent heat (190–220 kJ/kg) stand out as one promising candidate (a) to store and transport the cold energy and (b) to improve the energy efficiency of the cooling processes synergistically. In this review, we focus on reviewing SCHs as a cold energy storage and transport PCM covering both its fundamental properties (thermophysical properties, kinetics of formation and dissociation, rheological and transport properties, and safety and economic aspects) and its novel applications in several cooling processes. Prospects and challenges are also delineated on commercializing SCHs as a key technology enabler for the cold energy industry. There is strong confidence that possible disruptive SCH-based cooling technologies could be developed in the near future for energy efficiency improvement and environmental sustainability.

Structure and control co-optimization for an ejector expansion heat pump coupled with thermal storages

Optimal design and control are often coupled tasks for improving energy system performances. There is a lack of study on the structure and control co-optimization of heat pump coupled with thermal energy storages, which can enhance the penetration levels of intermittent renewables in integrated energy systems, thus we proposed a coupled dynamic optimization method for the structure and control co-optimization of this kind of dynamic energy system, and applied it successfully to a transcritical CO2 ejector expansion heat pump coupled with hot and cold water storages for thermal energy charging. Based on a complicated nonlinear dynamic system model considering thermal stratification in thermal energy storages, the structure and control co-optimization solutions were obtained for this coupled system during energy charging by using the co-optimization method with genetic algorithm. The detailed structures of gas cooler, evaporator, hot and cold energy storage tanks were optimized, then a dynamic optimal control strategy was developed for the whole charging process. The overall coefficient of performance can be increased by 23.2% and the total power consumption can be reduced by 17.6% using this newly developed co-optimization strategy, compared to the constant control parameter strategy. This study would be helpful for a structure and control co-optimization of other dynamic or stable energy systems.