Energy Storage Techniques Research Articles

Thermal behavior of a solar-assisted latent heat thermal energy storage unit on the heating season under variable weather conditions

Due to the fossil-fuel-related climatic problems which got worse in recent decades, the worldwide share of renewable energy has significantly increased. Even though solar energy is one of the most accessible renewables, it has an intermittent nature throughout the day. Different energy storage techniques are implemented to resolve the intermittency problem and make solar-aided energy accessible when it is needed. Energy use in buildings has a huge share of total energy demand, and heating/cooling demands are responsible for most energy consumption in buildings. In this study, the performance of a solar-assisted latent heat thermal energy storage (LHTES) unit integrated with a heat pump is investigated during the heating season under variable weather conditions. Phase change materials (PCMs) with different melting temperatures (Tm) and latent heat of fusions (hsf) are studied, and parametric simulations are conducted to examine the proposed systems' economic advantage and payback duration. Variable weather conditions are defined in simulations, and seven consecutive day analyses are conducted to ensure that results are not dependent on the initial conditions. Results revealed that the PCM with Tm = 35°C and hsf = 240 kJ/kg has a better thermal performance than the other alternatives, i.e., Tm = 31°C and 40°C. The integration of the solar-aided LHTES unit with the heat pump increases the COP of the heat pump, and the increment varies from 35% to 80% for heating months in Izmir. Such an improvement in COP reduces the operating costs related to the electricity consumption of the heating device significantly, and the simple payback period of the combined system is determined to be approximately 13 years in Izmir.

Modified Voltage Control Strategy for DC Network with Distributed Energy Storage using Fuzzy Logic Controller

This research provides an extraordinary distributed energy storage (DES) technique for DC distribution networks. Under exhibited virtual inertia and capacitances, the parameters of the AC and DC networks are briefly assessed. The proposed control approach for DES is based on many interactive features, which allows the DES to respond to both DC network voltage variations and make use of AC grid frequency changes. To reduce the burden of DC network voltage degradation, a cascade droop management approach with fuzzy is proposed for DES in DC microgrid. The simulation outcomes give a response that is fruitful for improving the voltage stability in DC distributed network as compared to other existing techniques. INDEX TERMS: Distributed energy storage, flexible voltage controlstrategy, AC and DC networks, fuzzy,voltage stability.

Nitrogen-rich azoles as trifunctional electrolyte additives for high-performance lithium-sulfur battery

Rechargeable lithium-sulfur (Li-S) batteries are considered one of the most promising energy storage techniques owing to the high theoretical energy density. However, challenges still remain such as the shuttle effect of lithium polysulfides (LPSs) and the instability of lithium metal anode. Herein, we propose to use nitrogen-rich azoles, i.e., triazole (Ta) and tetrazole (Tta), as trifunctional electrolyte additives for Li-S batteries. The azoles afford strong lithiophilicity for the chemisorption of LPSs. The density functional theory and experimental analysis verify the presence of Li bonds between the azoles and LPSs. The azoles can also interact with lithium salt in the electrolyte, leading to increase ionic conductivity and lithium-ion transference number. Moreover, the azoles render particle-like lithium deposition on the lithium metal anode, leading to superlong cycling of a Li symmetric cell. The Li-S batteries with Ta and Tta exhibit the initial discharge capacity of 1425.5 and 1322.2 mAh g−1, respectively, at 0.2C rate, and promising cycling stability. They also enable enhanced cycling performance of a Li-organosulfide battery.

Comparative assessment of four low voltage fault ride through techniques (LVFRT) for wind energy conversion systems (WECSs)

This paper presents a comparative assessment of four low voltage fault ride through (LVFRT) techniques that alleviate the effects of power imbalance during AC network faults for voltage source converter (VSC)-based wind energy conversion systems (WECSs). The techniques appraised include a software-based coordinated control (CC) technique, commercially available dumping resistor (DR) technique, and two energy storage techniques, namely, superconductive magnetic energy storage (SMES) and supercapacitor energy storage (SCES). The techniques presented are technically viable solutions for alleviating impacts of AC network faults on the WECS. The techniques have previously been assessed by performance-based metrics, whereas this paper aims to form a more comprehensive assessment by expanding the scope from the performance-based comparison to include economic considerations and practical limitations. Based on qualitative review of technically viable designs, this study presents quantitative substantiation with time-domain simulations of symmetrical and asymmetrical AC network faults. The comparative assessment is formulated based on assessing key performance metrics including grid code compliance, electrical and mechanical stress reduction, LVFRT response speed, hardware implementation, system efficiency and investment reduction. The assessment findings suggest that a performance-based study fails to highlight the potential financial and practical barriers that may exist regarding the implementation of the LVFRT solutions especially with energy storage-based techniques. However, the flexibility, benefits and increasing feasibility regarding energy storage systems may make them a preferred option for LVFRT of critical WECSs.

Heterogeneity in the Mo doped La0.55Sr0.45FeO3 cathode for direct CO2 electrolysis

• Mo-doping in La 0.55 Sr 0.45 FeO 3 prevents the production of SrCO 3 in CO 2 electrolysis. • Mo 6+ accelerates the adsorption/dissociation process of CO 2 /CO. • Heterogeneous regions were found to enhance the CO 2 electrolysis. • Initial performance dropping during CO 2 electrolysis is related to adsorption of CO. The large-scale integration of intermittent renewable energies into the power grid could reduce the CO 2 emission from the combustion of fossil fuel, but it requires energy storage techniques to balance the energy production and demand. The electrolysis of CO 2 that converting electricity into chemicals/fuels provides a sustainable way of energy storage and CO 2 reduction. Solid oxide electrolysis cell (SOEC) operating at around 800 °C was able to provide highly efficient transformation of CO 2 because the high temperature was able to decrease the energy demand and increase the activation of CO 2 than room temperature electrolysis. In this study, Mo-doped ferrite perovskite, La 0.55 Sr 0.45 Fe 0.85 Mo 0.15 O 3 , was studied as the cathode of an SOEC for the direct electrolysis of CO 2 at 800 °C. Cell with La 0.55 Sr 0.45 Fe 0.85 Mo 0.15 O 3 cathode showed a significantly higher current density during CO 2 electrolysis than the one with La 0.55 Sr 0.45 FeO 3 cathode. Compared with the parent La 0.55 Sr 0.45 FeO 3 cathode that will subject to a superficial decomposition into Fe 0 and SrO or SrCO 3 at an elongated cathodic bias of − 1.4 V, Mo-doping will induce the production of Ruddlesden-Popper phase ( e.g. (La,Sr) 2 (Mo,Fe)O 4 , Fe-Mo-O oxides and Fe 0 ). La 0.55 Sr 0.45 Fe 0.85 Mo 0.15 O 3 cathode was found to an unobvious current decrease at − 1.1 V, but a cell degradation was found under a high bias of − 1.4 V. During the 97 h’ aging under a cathodic bias (−1.4 V), the reduced molybdenum cation in La 0.55 Sr 0.45 Fe 0.85 Mo 0.15 O 3 was found to be less mobile than Fe 3+/2+ , La 3+ or Sr 2+ , and the perovskite with Fe-deficit region were also found to be important for the activation of CO 2 and dissociation of CO in the electrochemical process.

Novel multi-valent rechargeable ion battery: An organic nickel ion battery with Li3V2(PO4)3 cathode

Organic nickel ion battery using Ni2+ as a charge carrier has yet to be explored due to the lack of workable electrolytes and high-performing Ni2+ storage cathode materials to couple with the nickel metal anode. Herein, a feasible rechargeable organic nickel ion battery with an ether base electrolyte is demonstrated for the first time, in which Li3V2(PO4)3 and nickel foam as cathode and anode materials, respectively. The Li3V2(PO4)3 can demonstrate a high reversible specific capacity of 124 mAh g−1 at the rate of 1C and a stable cycle performance with 84% capacity retention after 50 cycles. In addition, a reversible insertion and extraction of Ni2+ ions into the cathode structure is confirmed by XRD, XPS, and EDX studies. Finally, using in-situ X-ray diffraction technology and Rietveld refinement, the reaction mechanism and structural changes during the cycle process are analyzed in detail. Therefore, the results provide an avenue to explore the organic nickel ion battery as a novel energy storage technique for renewable energies.

Utilization of symmetric electrode materials in energy storage application: A review

The development of efficient energy storage systems is an important field of research in the modern era where fossil fuels are headed toward depletion. The invention of batteries is regarded as one of the most significant advancements in the field of energy storage. From its inception, a lot of research has been done and is still being carried out to develop novel and advanced materials that provide improved performance in terms of capacity, stability, and cost. In this context, symmetric or bipolar electrodes, which utilize the same material for the anode and the cathode, emerge as a suitable solution for battery technology. In this work, different types of symmetric electrode materials for batteries are subjected to review. The various structures, methods of synthesis, and characteristics are analyzed and presented. The Na3V2(PO4)3 (NVP) is the most widely analyzed symmetric material among all the symmetric materials. The Na-based systems are widely studied in symmetric configurations for their resource availability and price economics advantages. Aqueous and solid-state symmetric batteries are the emerging systems in symmetric batteries. This review will provide insights to battery researchers involved in bipolar material design and shed light on new emerging energy storage techniques.

Recent advances and future perspectives for aqueous zinc-ion capacitors

Abstract Ion-hybrid capacitors are expected to combine the high specific energy of battery-type materials and the superior specific power of capacitor-type materials and are considered as a promising energy storage technique. In particular, aqueous zinc-ion capacitors (ZIC), possessing the merits of high safety, cost-efficiency and eco-friendliness, have been widely explored with various electrode materials and electrolytes to obtain excellent electrochemical performance. In this review, we first summarize the research progress on enhancing the specific capacitance of capacitor-type materials and review the research on improving the cycling capability of battery-type materials under high current densities. Then, we look back on the effects of electrolyte engineering on the electrochemical performance of ZIC. Finally, we propose research challenges and development directions for ZIC. This review provides guidance for the design and construction of high-performance ZIC.

In operando visualization of redox flow battery in membrane-free microfluidic platform

Redox flow batteries (RFBs) are attractive large-scale energy storage techniques, achieving remarkable progress in performance enhancement for the last decades. Nevertheless, an in-depth understanding of the reaction mechanism still remains challenging due to its unique operation mechanism, where electrochemistry and hydrodynamics simultaneously govern battery performance. Thus, to elucidate the precise reactions occurring in RFB systems, an appropriate analysis technique that enables the real-time observation of electrokinetic phenomena is indispensable. Herein, we report in operando visualization and analytical study of RFBs by employing a membrane-free microfluidic platform, that is, a membrane-free microfluidic RFB. Using this platform, the electrokinetic investigations were carried out for the 5,10-bis(2-methoxyethyl)-5,10-dihydrophenazine (BMEPZ) catholyte, which has been recently proposed as a high-performance multiredox organic molecule. Taking advantage of the inherent colorimetric property of BMEPZ, we unravel the intrinsic electrochemical properties in terms of charge and mass transfer kinetics during the multiredox reaction through in operando visualization, which enables theoretical study of physicochemical hydrodynamics in electrochemical systems. Based on insights on the electrokinetic limitations in RFBs, we verify the validity of electrode geometry design that can suppress the range of the depletion region, leading to enhanced cell performance.

Influence of guide vane profile on the flow energy dissipation in a reversible pump-turbine at pump mode

Pumped storage hydro (PSH) is a mature and widely used energy storage technique. The hydraulic dissipation of PSH will lead to the decline of power station efficiency. Therefore, it is important to find the reasons flow energy dissipation (FED). The adjustment of the flow channel will cause the change of flow energy dissipation. Guide vane is an important component of pump turbine, which has an influence on the problems of FED. In this paper, the FED in pump turbine with two guide vane profiles are analyzed. The combination of experimental method and numerical simulation method is adopted. Through experiments, the influence of two guide vane profiles on performance is clarified, and the method to judge the severity of Q-H instability is proposed. The FED under different working conditions were analyzed by entropy production. When the flow rate is at design point, the wake and local small flow separation causes FED. When the flow rate is large, FED is caused by the strong wake and flow separation in the runner. When the flow is small, the complex flow pattern in guide vane and back-flow cause high FED. The guide vane profiles have a great influence on FED. The match of blade leading edge and flow direction and flow control ability of guide vane affect the flow state caused the variation of FED.

MXenes with applications in supercapacitors and secondary batteries: A comprehensive review

Two-dimensional (2D) materials have received tremendous attention because they possess a set of merits not available in bulk materials, such as large specific surface area, low energy barrier for electron transportation and short ion diffusion path. These advantages are desirable especially for the electrodes in electrochemical energy storage devices. MXenes, first synthesized in 2011 by etching their MAX phase precursors, have plural reasons to represent a new family of 2D materials. Their rich diversity in structure and composition together with the uncommon combination of good electrical conductivity and hydrophilicity makes themselves outstand in the whole 2D materials world. Based on these advantages, MXenes hold great promise for various technologically important applications, particularly in developing new energy storage techniques for advanced smart systems, such as portable and flexible electronics. There have been remarkable research achievements in the synthesis and application of MXene-based materials. While new synthesis routes being continuously reported, MXenes with new composition and novel structure have also been routinely discovered, which will undoubtedly help understand the fundamental properties and expand the application scope of MXenes. As for their energy storage-related applications, to cope with the intrinsic weakness of MXenes, many endeavors have been made by doping, structure-tuning and compositing with hybrid ingredients. In this review, the current status of MXenes synthesis and up-to-date progress of their applications in supercapacitors, metal-ion batteries and lithium sulfur batteries are summarized and discussed, and the typical work on the application of MXenes for the aforementioned three categories is respectively tabulated for reference and comparison.

Requirements for Energy-Harvesting-Driven Edge Devices Using Task-Offloading Approaches

Energy limitations remain a key concern in the development of Internet of Medical Things (IoMT) devices since most of them have limited energy sources, mainly from batteries. Therefore, providing a sustainable and autonomous power supply is essential as it allows continuous energy sensing, flexible positioning, less human intervention, and easy maintenance. In the last few years, extensive investigations have been conducted to develop energy-autonomous systems for the IoMT by implementing energy-harvesting (EH) technologies as a feasible and economically practical alternative to batteries. To this end, various EH-solutions have been developed for wearables to enhance power extraction efficiency, such as integrating resonant energy extraction circuits such as SSHI, S-SSHI, and P-SSHI connected to common energy-storage units to maintain a stable output for charge loads. These circuits enable an increase in the harvested power by 174% compared to the SEH circuit. Although IoMT devices are becoming increasingly powerful and more affordable, some tasks, such as machine-learning algorithms, still require intensive computational resources, leading to higher energy consumption. Offloading computing-intensive tasks from resource-limited user devices to resource-rich fog or cloud layers can effectively address these issues and manage energy consumption. Reinforcement learning, in particular, employs the Q-algorithm, which is an efficient technique for hardware implementation, as well as offloading tasks from wearables to edge devices. For example, the lowest reported power consumption using FPGA technology is 37 mW. Furthermore, the communication cost from wearables to fog devices should not offset the energy savings gained from task migration. This paper provides a comprehensive review of joint energy-harvesting technologies and computation-offloading strategies for the IoMT. Moreover, power supply strategies for wearables, energy-storage techniques, and hardware implementation of the task migration were provided.

Charging and discharging analysis of thermal energy using magnesium nickel hydride based thermochemical energy storage system

A concentrated solar power plant integrated with thermal energy storage system helps to operate the plant during non-sunshine hours. This helps to increase the power generation capacity and improve the dispatchability of the power plant. Thermal energy systems are classified into sensible, latent, and thermochemical energy storage systems. Thermochemical energy storage with high energy storage density is one of the potential energy storage techniques available. The metal hydride-based thermal energy storage system has high energy storage density, better chemical reversibility, long cyclic, and high temperature stability. A dual bed metal hydride system uses high and low-temperature metal hydrides. High temperature metal hydride is used as energy storage media, while low-temperature metal hydride is used as hydrogen storage media. In this article, a detailed discussion on the energy sorption (absorption and desorption) analysis of a metal hydride suitable for high temperature in a dual bed metal hydride-based thermal energy storage system is performed. A 3-D model of Magnesium Nickel alloy in cylindrical geometry with radially distributed axial tubes is developed in COMSOL Multiphysics 5.5. The energy absorption and desorption analysis of metal hydride with variation in the number of heat transfer fluid tubes and different aspect ratio geometry are performed in detail. Study on variation of the number of heat transfer fluid tubes includes identifying the requirement of the adequate number of heat transfer fluid tubes to supply/remove heat to/from metal hydride during energy absorption/desorption. Variation of aspect ratios on the heat energy sorption characteristics and heat transfer phenomenon is studied in detail for both energy absorption and desorption cycle. The adequate number of heat transfer fluid tubes for the aspect ratio 0.5, 1, and 2 are found as is 32, 48, and 72, respectively. The stored and released energy for absorption and desorption study for the aspect ratio 0.5, 1, and 2 are 274.83 kJ, 255.44 kJ, and 240.27 kJ and 250.11 kJ, 234.43 kJ, and 224.10 kJ, respectively. The energy storage efficiency of the metal hydride bed for aspect ratios 0.5, 1, and 2 is 91%, 91.77%, and 93.27% respectively, while the overall system efficiency of the metal hydride bed for aspect ratios 0.5, 1, and 2 is 70.46%, 71.23%, and 72.39% respectively. The outcomes of this study helps to design the metal hydride based thermochemical energy storage system for process heating and power generation.

Thermal performance and behavior analysis of SiO2, Al2O3 and MgO based nano-enhanced phase-changing materials, latent heat thermal energy storage system

• Rayleigh number increases with buoyancy force. • Stefen number gives the relationship between specific heat and latent heat. • Nano inclusions undermine the energy storage capacity of the LHTSS. • During the charging cycle, conduction dominates the heat transfer. • Phase-changing materials are essential in the storage of solar energy or waste heat. The phase-changing material-based thermal energy storage method is one of the most prominent energy storage techniques used to store waste heat and surplus energy. The efficiency of the PCM-based energy storage system can be further modified by doping of nanoparticles. In the present study, the comparative effects of Al 2 O 3 , MgO, and SiO 2 nanodoping on thermal performance and the overall thermal behavior of PCM-based LHTES systems have been examined experimentally and numerically. Furthermore, the impact of Al 2 O 3 , MgO, and SiO 2- based nanoparticles on the charging and discharging rate, time, heat flux, and overall enthalpy is also studied. It is found that due to the inclusion of Al 2 O 3 , MgO, and SiO 2 nanoparticles, the charging rate is significantly increased by 33.8%, 33.8%, and 41% for Al 2 O 3 , MgO, and SiO 2 NEPCMs, respectively, in comparison to the PCM. The discharging rate is also increased by 19.6%, 25%, and 30% for Al 2 O 3 , MgO, and SiO 2 -based NEPCMs, respectively. However, the inclusion of nanomaterials decreases the control volume and enhances the dynamic viscosity, which further curtails the thermal energy storage capacity of the LHTES system. Also, the optimum value of the nano inclusions is determined by experimenting with SiO 2 doped PCM samples. It was observed that for a 0.1–0.3% rise in volume concentration, charging rates show maximum enhancements, which offers a rapid decline for a 0.3–0.5% rise in volume concentration. Therefore, an optimum volume concentration of 0.3% is established. Furthermore, it was also observed that SiO 2 doped PCM samples show a comparatively better thermal response than the other NEPCM samples, making them highly suitable for commercial applications. However, similar studies are further required to identify such potential nano-inclusions.

An Updated Review on Low-Temperature Nanocomposites with a Special Focus on Thermal Management in Buildings

Buildings contribute to 33% of total global energy consumption, which corresponds to 38% of greenhouse gas emissions. Enhancing building’s energy efficiency remains predominant in mitigating global warming. Advancements in thermal energy storage (TES) techniques using phase change material (PCM) have gained much attention among researchers, primarily to minimize energy consumption and to promote the use of renewable energy sources. PCM technology stays as the most promising technology for developing high-performance and energy-efficient buildings. The major drawback of PCM is its poor thermal conductivity which limits its potential use which could be resolved by dispersing conductive nanofillers. The acquired database on synthesis routes, properties, and performance of nano-dispersed phase change materials (NDPCMs) with various techniques presented in the paper should deliver useful information in the production of NDPCMs with desirable characteristics mainly for building construction applications. An outline of contemporary developments and use of NDPCMs as TES medium is delivered. Finally, a brief discussion on challenges and the outlook was also made. In-depth research is needed to explore the fundamental mechanisms behind the enhanced thermal conductivity of NDPCM with nanofillers dispersion and also a thorough investigation on how these mechanisms drive improvement in building performance.

Shape stabilized attapulgite/myristic-palmitic acid composite PCM for thermal energy storage implementations in buildings

Depletion of energy resources and increasingly serious environmental problems due to increasing population and technological developments has led researchers to develop advanced energy storage techniques. The latent heat thermal energy storage method, in which phase change materials (PCMs) are used, is one of the most promising methods to overcome such problems. Fatty acids have been preferred mostly as solid–liquid PCMs for different thermal energy storage (TES) applications. However, the leakage difficulty of these PCMs significantly limits their utilizations in TES systems. This study is focused on eliminating this disadvantage of myristic acid (M)-palmitic acid (P) eutectic mixture (MPEM) with proper phase transition temperatures for thermal management of buildings. The developed eutectic mixture was then incorporated with attapulgite clay (ATC) to achieve shape-stabilized composite which does not allow liquid PCM leakage. FT-IR and SEM findings indicated the existence of good physicochemical compatibility between the ATC and MPEM. DSC analysis revealed that the composite had phase change temperature of 44–45 °C and latent heat of fusion of about 74 J/g, respectively. TGA test results showed that the fabricated composite has good thermal durability and stability. It can be inferred from the results that the produced ATC/MPEM composite had noteworthy potential as new admixture material with TES ability which can be used for energy saving and indoor thermal comfort improvement in buildings.

Modelling Long-Term Transition from Coal-Reliant to Low-Emission Power Grid and District Heating Systems in Poland

Energy systems require technological changes towards climate neutrality. In Poland, where the power system is dominated by outdated coal-fired power plants, efforts to minimize the environmental impact are associated with high costs. Therefore, optimal paths for the development of the energy sector should be sought in order to achieve ambitious long-term strategic goals, while minimizing the negative impact on the consumers’ home budget. A methodology and a model for the development of the electricity and heat generation structure were developed and implemented in market allocation (MARKAL) modelling framework. Two scenarios were presented, i.e., business as usual (BAU) and withdrawal from coal (WFC) scenarios. The calculations showed a significant role of nuclear energy and offshore wind power in the pursuit of climate neutrality of electricity generation. In the BAU scenario, the model proposes to stay with coal technologies using carbon capture and storage systems. Withdrawal from coal (WFC scenario) makes it necessary to replace them by gas-fired power plants with CO2 sequestration. Solar energy can be used both in electricity and district heating. In order to build on the latter technological option, appropriate energy storage techniques must be developed. Geothermal energy is expected to be the key option for district heat generation in the long-term horizon. The proposed development paths guarantee a significant reduction in greenhouse gases and industrial emissions. However, complete climate neutrality is uncertain, given the current degree and dynamics of technological development.

Energy flexible CHP-DHN systems: Unlocking the flexibility in a real plant

The purpose of this paper is to identify and analyze the impact of flexibility enablers in cogeneration and district heating network (CHP-DHN) plants by means of a real case study located in central Italy. A wider definition of energy flexibility applicable to the entire energy supply chain (i.e. production, transport and usage) is used in this analysis. In particular the flexibility is intended as the capability of each part of the system to produce a variation in its load curve, while ensuring the required performance. In this sense energy efficiency technologies, the use of energy storage and advanced control techniques can be seen as flexibility enablers potentially available in each section of the energy system. The innovative contribution of this work is to propose flexibility strategies in compliance with the constraints imposed by both the managers and users. The study aims to show possible ways to activate flexibility services to be used with known instruments and to quantify their impact with a simulation-based approach. In particular, three different flexibility instruments are identified in different sections of the plant: (i) the use of a thermal energy storage (TES) in the generation side, (ii) the optimal management of the DHN supply temperature (energy distribution side) and (iii) the management of the thermostatically controlled loads (TCLs) of the final users (demand side) connected to the network. Through the implementation of simulation models calibrated with available measurements, the influence of these flexibility instruments on the energy/environmental performance is evaluated in comparison to the current configuration of the plant. Results confirm the great impact of the TES to increase the CHP working hours and, as a consequence, a primary energy saving increase is obtained in mid-season and in summer season. Whereas the optimal management of the water supply temperature in the DHN allows to obtain 1% fuel reduction in a typical winter week and 2% in a typical summer week. As far as the activation of the demand side flexibility is concerned, the effect of the management of TCLs on energy conservation is demonstrated: 1 °C reduction of the setpoint of all the residential users during a typical winter day produces a 7.3% reduction of the DHN thermal demand. However, its impact on the generation side (i.e. to reduce the electricity/thermal production of the CHP at specific times) is limited due to the characteristics of the considered CHP plant (the CHP engine is sized to cover only the thermal baseload and it scarcely affected by thermal demand variations). The analysis proposed helps to obtain valuable hints on unlocking the energy flexibility in CHP-DHN plants useful for a better management of such systems.

Manipulation on Two-Dimensional Amorphous Nanomaterials for Enhanced Electrochemical Energy Storage and Conversion.

Low-carbon society is calling for advanced electrochemical energy storage and conversion systems and techniques, in which functional electrode materials are a core factor. As a new member of the material family, two-dimensional amorphous nanomaterials (2D ANMs) are booming gradually and show promising application prospects in electrochemical fields for extended specific surface area, abundant active sites, tunable electron states, and faster ion transport capacity. Specifically, their flexible structures provide significant adjustment room that allows readily and desirable modification. Recent advances have witnessed omnifarious manipulation means on 2D ANMs for enhanced electrochemical performance. Here, this review is devoted to collecting and summarizing the manipulation strategies of 2D ANMs in terms of component interaction and geometric configuration design, expecting to promote the controllable development of such a new class of nanomaterial. Our view covers the 2D ANMs applied in electrochemical fields, including battery, supercapacitor, and electrocatalysis, meanwhile we also clarify the relationship between manipulation manner and beneficial effect on electrochemical properties. Finally, we conclude the review with our personal insights and provide an outlook for more effective manipulation ways on functional and practical 2D ANMs.

Energy storage enhancement of paraffin with a solar-absorptive rGO@Ni film in a controllable magnetic field

Magnetically driven photothermal conversion and energy storage techniques can enhance the energy storage performance of phase change materials (PCMs) and thus have immense potential in energy applications. Paraffin is a common PCM that melts slowly and has poor rate of heat storage capacity. In this study, the effect of a controllable magnetic field on the photothermal and heat storage properties of paraffin was investigated. First, a reduced-graphene-oxide/nickel foam (rGO@Ni foam) composite film with good photothermal ability, corrosion resistance, and oxidation resistance was prepared, and photothermal conversion and energy storage processes under different magnetic fields were experimentally studied. The movement of the composite film could be adjusted by the action of magnetic force, especially to enhance the phase interface movement, accelerate paraffin melting, and improve the photothermal capacity and heat storage characteristics of the material. The composite film and phase interface could be dynamically tuned by regulating the magnetic field, thus enhancing the photothermal conversion effect. In particular, with increasing magnetic field strength, the thermal energy storage efficiency and speed of phase interface movement increased by 29% and 50%, respectively. The proposed magnetic force-driven method will enhance solar energy conversion and promote direct solar energy applications.