Absorption Energy Storage Research Articles

Investigation on Saturation Vapor Pressure of NH3–H2O–LiBr in Absorption Energy Storage System

Energy storage technology applied between building energy and renewable energy exhibits inherent characteristics of continuity, stability, and high efficiency of energy density. To improve the energy storage density and efficiency of solution absorption energy storage system, an innovative method is proposed by adding ammonia to regulate the saturated vapor pressure of Lithium Bromide solution, which is used as the energy storage working fluid for the absorption energy storage system. Based on the static method principle of vapor–liquid equilibrium of multiple working fluids, a testing platform for the vapor pressure of multiple working fluids was built. The pressure of the Lithium Bromide solution and the Lithium Bromide solution added Ammonia with a concentration of 58% were measured. The results show that the pressure of the Lithium Bromide solution added Ammonia is 2–5 times higher than that of the Lithium Bromide solution. The maximum relative deviations between the calculated value of the models fitted by Antoine equation and Peng Robinson state equation and the experimental value are 4.65% and 10.88%, respectively. That indicates that the model fitted by Antoine equation is more precise for the calculation of the equilibrium pressure of the ternary working fluid. The equilibrium pressure of the Lithium Bromide solution added Ammonia is predicted by the model fitted by the Antoine equation.

Dynamic characteristics and performance analysis of a double-stage energy storage heat transformer with a large temperature lift

Intermittence and low grade are significant barriers for the widespread application of renewable/waste energy. An absorption energy storage heat transformer with adequate energy storage and temperature lift characteristics effectively addresses this challenge. An advancement in this technology is the double-stage energy storage heat transformer (DESHT), which further enhances the range of temperature upgrade through twice temperature lifts. This paper proposes a time-dependent approach for a comprehensive study of the DESHT cycle with a working pair of LiBr/H2O. Firstly, the dynamic characteristics of the DESHT cycle are shown. Subsequently, the effects of discharging temperatures, charging temperatures, and solution mass ratio on cycle performance are analyzed. Results show that the DESHT cycle can achieve a temperature lift from 35 °C to 55 °C. 90 % of the total storage capacity can be reached in 60–70 % of the total charging time. The maximum discharging time per unit of charging time is achieved at a temperature lift of 45 °C. Besides, compared to the conventional double-stage absorption energy storage cycle, the DESHT cycle shows a higher exergy efficiency. Optimizing the solution mass ratio can enhance the cycle performance. These findings can serve as a valuable reference in exploring the DESHT cycle.

Effect of chitosan on the insulation and smoke absorption properties of expanded vermiculite composites

ABSTRACT In order to improve the thermal insulation and smoking properties of expanded vermiculite matrix composites, a kind of expanded vermiculite (EV)/chitosan (CS) composites was prepared by hot pressing. The effects of CS on smoke density, fire-resistance, insulation, and mechanical properties of the EV/CS composites were studied. The results show that with the increase of CS content, the smoke absorption performance and energy storage modulus of the composites is improved. Thermogravimetric (TG) analysis shows that the thermal stability of the EV/CS composite is improved by the presence of chitosan. The pores appear on the surface of the composites after the single-side fire-resistance test. After that, the thermal conductivity of the composites gradually decreases and the insulation performance is improved as the CS content increases. The CS carbonized during the preparation of the composites and thermal decomposition during the test. The morphology results show phase separation of the composites, and the porosity of the composites increases after the test. The reticular structure formed between the EV particles, sodium silicate, and CS molecules reduces the strength loss of the composites.

Finite time thermodynamic optimization for performance of absorption energy storage systems

Absorption energy storage (AES) has attracted worldwide attention due to the high energy storage density and environmental friendliness. To optimize the performance of the AES system, a finite time thermodynamic (FTT) model considering some influencing factors such as time, heat transfer area, heat transfer temperature difference, internal friction and dissipation has been developed in this paper. A new concept of ratio of charging and discharging time is proposed. The general relation of the energy storage efficiency, energy storage rate and energy release rate are induced based on FTT analysis. The distribution of the total thermal conductivity was optimized under the condition of a certain total thermal conductivity and the optimized maximum cooldown release rate has been increased by 14%. The optimal operating conditions of the AES system are obtained. Furthermore, the influences of the internal irreversibility, ratio of charging and discharging time and heat source temperatures on the performance of the AES system are analyzed. The research results can provide theoretical basis and guidance for the AES system design and optimization.

Preparation and characterization of bifunctional wolfsbane-like magnetic Fe3O4 nanoparticles-decorated lignin-based carbon nanofibers composites for electromagnetic wave absorption and electrochemical energy storage

Recently, with the pursuit of high-efficiency electromagnetic wave absorption (EMWA) and electrochemical energy storage (EES) materials, multifunctional lignin-based composites have attracted significant interest due to their low cost, vast availability, and sustainability. In this work, lignin-based carbon nanofibers (LCNFs) was first prepared by electrospinning, pre-oxidation and carbonization processes. Then, different content of magnetic Fe3O4 nanoparticles were deposited on the surface of LCNFs via the facile hydrothermal way to produce a series of bifunctional wolfsbane-like LCNFs/Fe3O4 composites. Among them, the synthesized optimal sample (using 12 mmol of FeCl3·6H2O named as LCNFs/Fe3O4–2) displayed excellent EMWA ability. When the minimum reflection loss (RL) value achieved −44.98 dB at 6.01 GHz with an thickness of 1.5 mm, and the effective absorption bandwidth (EAB) was up to 4.19 GHz ranging from 5.10 to 7.21 GHz. For supercapacitor electrode, the highest specific capacitance of LCNFs/Fe3O4–2 reached 538.7 F/g at the current density of 1 A/g, and the capacitance retention remained at 80.3 %. Moreover, an electric double layer capacitor of LCNFs/Fe3O4–2//LCNFs/Fe3O4–2 also showed a remarkable power density of 7755.29 W/kg, outstanding energy density of 36.62 Wh/kg and high cycle stability (96.89 % after 5000 cycles). In short, the construction of this multifunctional lignin-based composites has potential applications in electromagnetic wave (EMW) absorbers and supercapacitor electrodes.

Ternary mixture thermochromic microcapsules for visible light absorption and photothermal conversion energy storage

Thermochromic microcapsules with photothermal conversion properties were prepared by melamine urea formaldehyde resin (MUF) coated ternary mixtures (color coupler, color developer and solvent). The particle characteristics, chemical structure, heat storage properties, discoloration effect, thermal cycling durability and photothermal conversion properties of microcapsules were analyzed and characterized by ESEM and LPSA, FTIR and XRD, DSC and TGA, SC-10 and UV–Vis, thermal cycling test and solar simulator. The thermochromic and photothermal conversion mechanisms of microcapsules were analyzed. The results showed that the thermochromic microcapsules with a core material ratio of (1:3:60) have the best comprehensive performance. The chromatic aberration value of RTPCMs-C3 and RTPCMs-O3 is 23.35 and 12.14, respectively, which has a certain visible light absorption capacity and excellent thermal cycle durability. The photothermal conversion efficiencies of RTPCMs-C3 and RTPCMs-O3 under simulated solar irradiation were 55.4% and 72.9%, respectively. The conjugated organic polymer core material selectively absorbs the electromagnetic radiation frequency which are matching its internal electronic transition, causing the atomic lattice vibration to generate heat. The heat changes the state of the core material and dissociates the internal conjugated double bonds, eventually causing the microcapsules to change color.

Optimal scheduling of combined cooling, heating, and power system-based microgrid coupled with carbon capture storage system

The paramount role of microgrids (MGs) in strengthening the energy network and supply of many users in more cost-effective, safe, and sustainable manner cannot be overlooked. Energy carriers' interdependence on each other, as well as the rapid rise of tri-generation technologies, provide several obstacles to ensuring the network's best performance. A combined-cooling heat and power (CCHP) system based on various renewable-based resources and MGs is capable of supplying electricity, thermal, and cooling loads, in which the operation of CHP-based MG (CBM) is heavily influenced by the interaction between these carriers. On this basis, this paper is proposed a comprehensive analysis of CBM operation, which is coupled with electrical and absorption chillers (ACs), energy storage, and renewable-based units like solar and wind power under a multi-objective optimization (MOO) technique. In addition, a Power-to-Gas (PtG) technology is utilized in the proposed system to enhance the overall operation, reduce CO2 emission, and to contribute to the cooling and heat supply in the presence of various uncertainties. The suggested MOO methodology evaluates the operation cost of the system as the first objective and the reduction of CO2 emission as the second objective. An epsilon-constrained approach and Pareto solution are considered to assess the methodology. As a result, this study examines the system's reliance on individual carriers as well as the interdependence of those carriers. The results reveal the effectiveness of the proposed model to reduce CO2 emission and operational costs.

A systematic thermodynamic performance assessment of a solar-driven double-effect absorption chiller integrated with absorption energy storage

Sensible heat storage in the form of hot water is usually applied to solar-driven cooling systems to increase their cooling coverage. The main limitation of sensible heat storage is high thermal losses. A double-effect absorption chiller is operating in a typical generating temperature range of 150–180 °C and has a better performance compared to the single-effect type. Due to the high operating temperature range of the chiller, this study suggests the integration of an absorption energy storage (AES) on a double-effect chiller based on H2O-LiBr solution and driven by parabolic trough solar collectors. This is because in AES, heat is stored in the form of chemical potential and the issue of heat loss is minimal. The paper presents a model of the integrated system and its performance evaluation considering the undesirable solution crystallization phenomena under various operating conditions. The results show that, under certain operating conditions, there is a high risk of solution crystallization in the chiller during the charging operation when the solution distribution ratio is below 50 %. Moreover, the results indicate that when a solution with an initial lithium mass fraction of around 55 % in the strong tank is considered, there is a tendency for crystal formation in the solution storage tank and at some locations within the chiller. There is a potential risk of solution crystallization in the solution storage tank and at some locations within the chiller cycle when a solution with an initial LiBr mass fraction of 55 % and an initial mass of 64,000 kg is considered. Considering the weather data of Dhahran, the best-operating conditions are obtained at an initial solution mass of 64,000 kg in the storage tank, initial solution LiBr mass fraction of 0.5, and solution distribution ratio of 55 %. At these and other conditions detailed in the paper, the highest energy storage density is about 136.8 kWh/m3, with an average cooling effect of 1700 kW, overall solar system COP, and exergy efficiency of 0.985 and 0.067 respectively, during a fourteen-hour operation. The findings in this study provide useful information to researchers on sizing the storage unit considering the appropriate initial conditions to avoid solution crystallization.

Optimal design and performance assessment for a solar powered electricity, heating and hydrogen integrated energy system

Incorporating solar energy technologies into integrated energy systems (IES) plays an increasingly important role to mitigate energy supply shortages and climate challenges. However, the low efficiency of solar energy utilization and land limitation for system deployment greatly restrict the development of the solar powered IESs. In this paper, a solar powered electricity, heating and hydrogen IES based on photovoltaic (PV), photothermal (PT) and photocatalysis of hydrogen production (PH) is proposed and investigated. The system comprises solar radiation spectrum splitting technology, PV, PT, PH, electric heating device, compressive heat pump, solid oxide fuel cell, absorption heat pump and energy storage components. A component sizing method based on a region contraction algorithm is employed to find the system optimal design with minimizing the cost of energy. Two scenarios of the solar powered IES based on solar spectrum splitting unit and independent energy supply unit are analyzed and compared. The results show that the solar powered IES can completely meet the electricity, heating and hydrogen energy demands and achieve cost savings for consumers. Compared to independent energy supply unit-based IES, the use of solar spectrum splitting unit can significantly improve the total energy efficiency by 21.74% and reduce the land area for solar capture by 52.5%, but increase the cost of energy by 27.3%.

Multifunction lignin-based carbon nanofibers with enhanced electromagnetic wave absorption and surpercapacitive energy storage capabilities

It is difficult for green sustainable lignin-based materials to simultaneously obtain efficient electromagnetic wave absorption (EMWA) and supercapacitive energy storage (SCES), which has not yet been reported. Herein, the light-weight lignin-based carbon nanofibers (LCNFs) with proper pore size, well graphitization degree, and heteroatom doping were tailored through electrospinning and carbonization processes. Interestingly, the graphitization degree and porous structure of LCNFs could be easily adjusted by changing the activating temperature, and the higher conductivity was achieved for preparing LCNFs at higher activating temperature due to the differences in the crystal size and activating degree of LCNFs. As a result, in the field of EMWA, the LCNFs-950 exhibited the minimum reflection loss (RL) value was −41.4 dB and the absorbing frequency was 9.05 GHz at 2.5 mm thickness, which meant this absorbent could absorb and/or dissipate more than 99.9% of incident electromagnetic wave (EMW). Furthermore, the LCNFs-950 also exhibited excellent SCES ability. In two-electrode system, the optimal LCNFs-950 symmetric supercapacitor specific capacitance reached 139.4 F/g at a current density of 0.5 A/g, meanwhile, the energy density was 41.4 Wh/kg at a power density of 3500 W/Kg. These multifunctional features of LCNFs will be highly promising for the next-generation environmental remediating materials.

Thermodynamic analysis of absorption energy storage cycle with choline based green solvents

The absorption refrigeration and heat pump system and the thermochemical energy storage technology have natural and easy combination characteristics. The working pairs store and release low-grade heat in the form of thermochemical energy by changing the concentration of the solution, which can realize thermal or cold storage. This paper uses three deep eutectic solvents of choline chloride as absorbents and water as the refrigerant. The working fluid pair has a competitive or higher performance, ignoring the power consumption caused by flow resistance. The influence of generation or charging temperature on refrigeration performance and energy storage density were theoretically studied. The results show that water/Ethaline performs best under a typical single-effect working condition in cycle heat storage ratio and energy storage density, up to 0.87 and 677.8 kJ/kg; Glyceline and Reline have a better application potential when driven temperatures increase.

Advanced Modeling of Nanofluid-Based Solar Receivers in the Concentrated Solar Power Trough to Enhance the Heat Absorptivity

Nanofluids utilized as volumetric absorbers of solar energy have shown significant potential to enhance solar energy absorption and storage. The majority of numerical models currently employed to design and optimize the nanofluid-based solar receiver and storage systems involved assumptions and simplifications that can adversely impact performance prediction. Due to the inherent complexity of nanofluid systems, including interactions between the optical and thermo-physical properties of each phase, the development and optimization of solar energy absorption and storage systems in nanofluid-based receivers require advanced use mathematical–physical models for more effective design and optimization. This study aims to assess the impact of these critical assumptions on predicting thermal absorption and thermal energy storage capacity for such systems and developing accurate predictive modeling to aid the design and optimization of such systems. The results presented in this paper will assist in creating accurate mathematical models of Concentrated Solar Power (CSP) using nanofluids, and therefore enhance its thermal absorptivity and storage capacity.

A versatile N-doped honeycomb-like carbonaceous aerogels loaded with bimetallic sulfide and oxide for superior electromagnetic wave absorption and supercapacitor applications

Electromagnetic pollution and electrochemical energy consumption have driven enormous endeavors in electromagnetic wave absorption materials and energy storage devices, however, designing versatile composites for addressing the issue remains a huge challenge. Herein, a versatile honeycomb-like N-doped carbon/bimetallic sulfide and oxide (N–CoFe2O4-CoxSy/FexSy@C) composites aerogel was designed via a simple mechanical mixing, freeze-drying and heat treatment method. As-prepared N–CoFe2O4-CoxSy/FexSy@C composites exhibited excellent electromagnetic wave absorption and electrochemical performances. The minimum RL can reach −51.9 dB at 15.5 GHz, with an effective frequency bandwidth (RL < −10 dB) of 4.01 GHz (13.73–17.74 GHz) at a thickness of 1.5 mm, these remarkable properties were originated from the abundance dipole/interfacial polarization along with multiple magnetic attenuation process. More importantly, an outstanding specific capacitance of 2883 F g−1 at 1 A g−1 and excellent cycling stability of 89.5% after 5000 cycles were also achieved, which is ascribed to the affluent active sites and well-defined hetero-architecture. Considering the novel N–CoFe2O4-CoxSy/FexSy@C composites aerogel possessing a unique blend of excellent electromagnetic wave absorber and supercapacitors electrodes, these multifunctional features would be highly promising for the next-generation environmental remediating materials.

Economic analysis of a novel solar-assisted air conditioning system with integral absorption energy storage

The application of solar cooling systems is directly linked to the availability of solar radiation. Consequently, energy storage is important to achieve extended cooling coverage. This paper presents the economic performance evaluation of a novel solar-assisted absorption air conditioning system integrated with absorption energy storage (AES). The proposed solar-assisted air conditioning system consists of a parabolic trough solar collector (PTC), parallel-flow double-effect water-lithium bromide (H2O–LiBr) absorption chiller, and AES. In this paper, the economic feasibility of the system is evaluated based on the annuity method. The results indicate a payback period of about 5 years to recover the initial investment of the proposed system for a commercial building based on the weather conditions of the Eastern region of Saudi Arabia. The existing vapour-compression air conditioning system operating alone consumes more energy compared to that when supplemented with the solar-driven absorption chiller with AES. A maximum of 58% energy-saving is achieved from the integrated solar-assisted cooling system in July and August. Furthermore, a solar fraction of 63% is obtained from the integrated solar cooling system. Finally, the annual levelized cost of energy-savings of about 137,944 USD is achieved from the proposed cooling system.

A novel metal-organic framework derived carbon nanoflower with effective electromagnetic microwave absorption and high-performance electrochemical energy storage properties.

Here we report on the electrochemical performance and electromagnetic microwave absorption (EMWA) properties of a novel metal-organic framework derived carbon nanomaterial. This carbon material shows high-performance electrochemical energy storage, and has a maximum reflection loss of 27.6 dB with an effective absorption bandwidth of 2.24 GHz.

Magnetically-accelerated photo-thermal conversion and energy storage based on bionic porous nanoparticles

Recently, the technology of mixing phase change materials with high thermal conductivity fillers was developed, which has allowed thermal energy storage to be implemented in a wide range of industrial technologies and processes. In the present study, a hierarchical bionic porous nano-composite was prepared, which efficiently merged the nanomaterial characteristics of magnetism and high thermal conductivity in order to form a magnetically-accelerated solar-thermal energy storage method. The morphology and thermo-physical properties of materials were analysed. The experimental outcomes of phase change heat transfer demonstrated that the maximum storage efficiency increases by 102.7% when the hierarchical bionic porous structure is used, and a further 27.1% improvement can be achieved with the magnetic field. At the same time, the heat transfer process of energy storage in hierarchical porous composites under external physical fields is explained by simulation. Therefore, this magnetically-accelerated method demonstrated the superior solar-thermal energy storage characteristics within a hierarchical bionic porous structure which is particularly beneficial for the utilisation of solar direct absorption collectors and energy storage technology.

Charging and discharging characteristics of absorption energy storage integrated with a solar driven double-effect absorption chiller for air conditioning applications

The operation of solar driven air conditioning systems is limited to the availability of solar radiation. Consequently, to achieve extended cooling period, energy storage is necessary. This study presents performance evaluation and charging and discharging characteristics of an absorption energy storage coupled with solar driven double-effect water-lithium bromide (H2O-LiBr) absorption system through thermodynamic modeling and simulation. The absorption energy storage stores the solar heat in the form of chemical energy during the day and discharges later for cooling application. The integrated system achieved effective cooling for about fourteen hours on daily basis. The results indicate an average coefficient of performance (COP) of 1.35 for the integrated absorption chiller-storage unit and exergy efficiency of 25%. Furthermore, the overall COP of the integrated solar cooling system is 0.99 and the overall exergy efficiency is 6.8%, while the energy storage density for typical climatic conditions of Dhahran, Saudi Arabia is found to be 444.3 MJ/m3. The energy storage density obtained from the integrated solar driven H2O-LiBr double-effect absorption system is found to be higher by 13–54% compared to other integrated systems based on single-effect configuration.

High energy-density multi-form thermochemical energy storage based on multi-step sorption processes

A novel multi-form thermochemical energy storage method is proposed for high energy-density thermal energy storage based on multi-step sorption processes. The proposed multi-form thermochemical energy storage combines the physisorption energy storage of a porous matrix, the chemisorption energy storage of a salt hydrate, and the absorption energy storage of the salt solution. High-performance composite sorbent of MgCl2@zeolite was prepared to demonstrate the feasibility of the proposed multi-form thermochemical energy storage. The water uptake contributions of physisorption, chemisorption and absorption of the composite sorbent were measured by a “three-step” hydration method. The multi-step desorption processes measured by TG at an extremely slow heating rate shows the apparent decrease of decomposition temperature of MgCl2 hydrates in zeolite matrix. The maximum sorption capacity of the MgCl2@zeolite composite sorbent without solution leakage is as high as 0.55 g/g and its gravimetric and volumetric thermal energy densities reach 1368 kJ/kg and 308 kWh/m3 respectively with charging temperature of 200 °C. This gravimetric energy density is about 2.26 times higher than that of pure zeolite 13X. The experimental results verified that the proposed multi-form thermochemical energy storage is an effective method to improve sorption capacity and to achieve high energy-density thermal storage.

Creating a Polar Surface in Carbon Frameworks from Single-Source Metal–Organic Frameworks for Advanced CO2 Uptake and Lithium–Sulfur Batteries

Creating a polar surface and a large surface area in porous materials offers a powerful strategy for various applications, like gas absorption and separation and energy storage and conversion. High...

Performance characteristics of a solar driven lithium bromide-water absorption chiller integrated with absorption energy storage

The use of solar–assisted absorption chiller for space cooling is limited to availability of solar radiation; hence, energy storage is very crucial in order to achieve extended hours of cooling operation. In this study, operational and performance characteristics of a solar driven lithium bromide-water absorption chiller integrated with absorption energy storage of the same working fluid are investigated. The integrated system simultaneously provides cooling and charging of the absorption energy storage during the hours of solar radiation. Simulation of the integrated system is carried out based on first law of thermodynamics. Effects of weather variables such as solar radiation and the influence of coupling absorption energy storage with an absorption chiller are investigated. The results indicate that cooling effect of the chiller varies with the variation of solar radiation, with maximum value of 20kW for a collector area (Ac) of 96m2 on a typical day in July, Dhahran, Saudi Arabia. The cooling COP of the integrated system during cooling/charging and discharging is found to be 0.69 and the energy storage density of the absorption energy storage is 119.6kWh/m3. Furthermore, the operational characteristics of the proposed system showed that the internal operating parameters of the integrated chiller-absorption energy system such as solution temperatures and pressures are within reasonable levels. Hence, this indicates the possibility of integrating the absorption energy storage with absorption chiller.