Storage Of Renewable Energy Sources Research Articles

Calcium hydride with aluminium for thermochemical energy storage applications

Addition of aluminium to calcium hydride delivers excellent operating conditions for utilisation as a thermal energy storage material.

Dynamic system modeling and simulation of a power-to-methanol process based on proton-conducting tubular solid oxide cells

The importance of methanol as a basic building block of the chemical industry and as a means of chemical energy storage of renewable energy sources (e.g. wind & PV) will steadily increase in the upcoming years. Based on renewable electricity and through the coupling of a proton-conducting steam electrolyzer for the generation of pure H2 with a heterogeneously catalyzed direct synthesis of methanol from anthropogenic CO2, an attractive method for the production of methanol can be provided. The efficient and economic application and operation of these so-called power-to-methanol processes requires suitable system control and heat integration concepts for alternating operating conditions. In this work, a transient and real-time capable system model of a power-to-methanol process based on tubular proton-conducting high temperature electrolyzers is presented. The obtained stationary simulation results reveal beneficial operational windows and system efficiencies (0.488 to 0.637) with respect to the chosen process design and heat integration concept. The power-to-methanol process model also incorporates a multitude of feedback control loops or controllers, to manipulate relevant operating parameters of all employed sub-processes in case of fluctuating power inputs. Furthermore, the presented studies assess the transient responses of the power-to-methanol system to defined step changes of the apparent cell voltage based on a multitude of negative feedback control loops.

Lithium Bis(oxalate)borate Additive for Self‐repairing Zincophilic Solid Electrolyte Interphases towards Ultrahigh‐rate and Ultra‐stable Zinc Anodes

AbstractThe artificial solid electrolyte interphase (SEI) plays a pivotal role in Zn anode stabilization but its long‐term effectiveness at high rates is still challenged. Herein, to achieve superior long‐life and high‐rate Zn anode, an exquisite electrolyte additive, lithium bis(oxalate)borate (LiBOB), is proposed to in situ derive a highly Zn2+‐conductive SEI and to dynamically patrol its cycling‐initiated defects. Profiting from the as‐constructed real‐time, automatic SEI repairing mechanism, the Zn anode can be cycled with distinct reversibility over 1800 h at an ultrahigh current density of 50 mA cm−2, presenting a record‐high cumulative capacity up to 45 Ah cm−2. The superiority of the formulated electrolyte is further demonstrated in the Zn||MnO2 and Zn||NaV3O8 full batteries, even when tested under harsh conditions (limited Zn supply (N/P≈3), 2500 cycles). This work brings inspiration for developing fast‐charging Zn batteries toward grid‐scale storage of renewable energy sources.

Lithium Bis(oxalate)borate Additive for Self-repairing Zincophilic Solid Electrolyte Interphases towards Ultrahigh-rate and Ultra-stable Zinc Anodes.

The artificial solid electrolyte interphase (SEI) plays a pivotal role in Zn anode stabilization but its long-term effectiveness at high rates is still challenged. Herein, to achieve superior long-life and high-rate Zn anode, an exquisite electrolyte additive, lithium bis(oxalate)borate (LiBOB), is proposed to in-situ derive a highly Zn2+-conductive SEI and to dynamically patrol its cycling-initiated defects. Profiting from the as-constructed real-time, automatic SEI repairing mechanism, the Zn anode can be cycled with distinct reversibility over 1800 h at an ultrahigh current density of 50 mA cm-2, presenting a record-high cumulative capacity up to 45 Ah cm-2. The superiority of the formulated electrolyte is further demonstrated in the Zn||MnO2 and Zn||NaV3O8 full batteries, even when tested under harsh conditions (limited Zn supply (N/P≈3), 2500 cycles). This work brings inspiration for developing fast-charging Zn batteries toward grid-scale storage of renewable energy sources.

Nanocellulose‐Carboxymethylcellulose Electrolyte for Stable, High‐Rate Zinc‐Ion Batteries

AbstractAqueous Zn ion batteries (ZIBs) are one of the most promising battery chemistries for grid‐scale renewable energy storage. However, their application is limited by issues such as Zn dendrite formation and undesirable side reactions that can occur in the presence of excess free water molecules and ions. In this study, a nanocellulose‐carboxymethylcellulose (CMC) hydrogel electrolyte is demonstrated that features stable cycling performance and high Zn2+conductivity (26 mS cm−1), which is attributed to the material's strong mechanical strength (≈70 MPa) and water‐bonding ability. With this electrolyte, the Zn‐metal anode shows exceptional cycling stability at an ultra‐high rate, with the ability to sustain a current density as high as 80 mA cm−2for more than 3500 cycles and a cumulative capacity of 17.6 Ah cm−2(40 mA cm−2). Additionally, side reactions, such as hydrogen evolution and surface passivation, are substantially reduced due to the strong water‐bonding capacity of the CMC. Full Zn||MnO2batteries fabricated with this electrolyte demonstrate excellent high‐rate performance and long‐term cycling stability (>500 cycles at 8C). These results suggest the cellulose‐CMC electrolyte as a promising low‐cost, easy‐to‐fabricate, and sustainable aqueous‐based electrolyte for ZIBs with excellent electrochemical performance that can help pave the way toward grid‐scale energy storage for renewable energy sources.

Experimental investigation of the effect of thermal cycling on the thermomechanical properties of three rock varieties for high temperature thermal energy storage

During the past years “rock batteries” have become increasingly relevant for the storage of renewable energy sources, such as wind and solar energy, because of their economic and ecological advantages with respect to previously more common materials for thermal energy storage (TES) such as salt. In rock-based TES systems, thermal energy is stored in packed-bed rock using air as heat transfer fluid. We investigated three different rock types with respect to changes in thermomechanical properties after different numbers of thermal cycles, Ruhr sandstone (Oberste quarry in Dortmund - Germany), basalt (commercial MTV basalt) and Calanca gneiss. Cylindrical samples were heated to 800°C within 11,5 h before temperature was kept constant for another 30 min and then decreased within 11,5 h. Samples were thermomechanically investigated before thermal treatment, and again after 1, 3, 7 and 15 cycles. Additionally, two samples of each rock type were subjected to a thermal cycle with a maximum temperature of 450°C and to 1000°C, respectively, at a heating/cooling rate corresponding to that of the samples heated to 800°C. Samples were characterised with respect to ultrasound wave velocity, bulk density, thermal conductivity, thermal diffusivity, uniaxial compressive strength, splitting tensile strength, mineral content (X-ray powder diffraction) and microstructure (thin section analysis). Samples of basalt could not withstand the standard heating rate. The samples crushed into small pieces also when heating rates were reduced and at a maximum heating temperature of 800°C. For sandstone and gneiss, the ultrasound wave velocity, bulk density, thermal conductivity, thermal diffusivity, uniaxial compressive strength and splitting tensile strength decreased systematically with increasing number of cycles, while the maximum reduction occurred after the first cycle and the relative reduction was similar between both rocks. Microstructural analysis indicated an increase in crack density and minor mineralogical changes upon heating. Both rocks, Ruhr sandstone and Calanca gneiss, appear suitable for TES, but Calanca gneiss is less suitable for temperatures above 800°C due to a significant reduction in bulk density and uniaxial compressive strength when heated to 1000°C. Also, its anisotropy and anisotropic response to heating can lead to preferred flow paths of the heat transfer fluid. Ruhr sandstone maintains a high uniaxial compressive strength of about 100 MPa even after 15 cycles while thermal capacity was only slightly reduced or even increased, and can be recommended for use in high temperature TES. This study is the outcome of a research-oriented teaching program at Ruhr-University Bochum within the Geoscience curriculum for students with focus on Engineering Geology. Student authors (Fränzer to Thomas) are listed in alphabetical order.

Cobalt Doped Sulfonated Polyaniline with High Electrocatalytic Activity and Stability for Oxygen Evolution Reaction

AbstractThe oxygen (OER) evolution reaction plays a crucial role for storage of renewable energy sources but, active sites of the active electrocatalysis remain in challengeable. In this work, we have developed sulfonated polyaniline (SPANI) coordinated with Co sites to investigate the OER process. To improve the electrical conductivity and electrocatalytic efficiency towards OER herein, we report Co@SPANI synthesized by solvothermal method. The different physical characterization (SEM, TEM, XRD, IR, XPS and UV‐DRS) and electrochemical methods (voltammetry, chronopotentiometry and EIS) have been used to characterize Co@SPANI materials and examined the correlation of materials with activity. The cobalt doped SPANI (Co@SPANI‐800) exhibits higher electrocatalytic activity, showing smaller Tafel slope of 167 mV dec−1 with lower overpotential of 312 mV at 10 mA cm−2 in 1 M KOH, which reveal that abundant Co‐metal sites remarkably supporting the OER activity. Co@SPANI‐800 exhibits exceptional OER performances and durability over 200 h with loss of <3.5 % in alkaline medium. At 1.54 V, solar powered water electrolysis confirmed the effectiveness of newborn electrocatalyst in solar energy to hydrogen energy conversion. Therefore, this work offered new path for designing materials as self‐supporting electrode for water splitting and for other potential applications.

Experimental Study of Varying Heat Transfer Fluid Parameters within a Latent Heat Thermal Energy Storage System Enhanced by Fins

Latent heat thermal energy storage (LHTES) systems can be used to combat the limited collection and long-term storage of renewable energy sources. The key component of an LHTES system is its phase change material (PCM), which thermally stores energy. Despite extensive research on thermal conductivity enhancement within PCM, little attention has been paid to the heat transfer fluid (HTF) within the system. This study aimed to observe the impact of variable HTF flow rates and temperatures on the speed of charging and discharging an LHTES system enhanced with annular fins. Two copper fin configurations of 10 and 20 annular fins were tested within an LHTES system with Rubitherm RT-55 PCM. The configurations were tested during charging processes with HTF parameters of 65 °C and 70 °C at 1, 2, and 3 gpm. Discharging processes were tested with HTF parameters of 15 °C and 20 °C at 0.5, 1, and 1.5 gpm. The system energy response and PCM temperature were recorded throughout the tests. The results of the study revealed that a higher flow rate produced a shorter processing time, but furthermore, that a larger temperature gradient between the PCM and HTF caused a more significant decrease in charging and discharging times.

Design of Battery management system for Residential applications

Battery management system plays an important role for modern battery-powered application such as Electric vehicles, portable electronic equipment and storage for renewable energy sources. It also increases the life-cycle of the battery, battery state and efficiency. Monitoring the state of charge of the battery is a crucial factor for battery management system. This paper deals with monitoring the state of charge of the battery along with temperature, current for Solar panel fitted with battery for residential application. Microcontroller is used for controlling purpose, analog sensors are used for sensing the parameters of voltage, current. The information of the battery is given with tabular form and shown in photograph. Battery parameters are displayed with the LCD screen.

Graphite Anode for Potassium Ion Batteries: Current Status and Perspective

With the increased demand from the storage of renewable energy sources, some safe and inexpensive energy storage technologies instead of Li‐ion batteries become urgently needed. Therefore, K‐ion batteries (KIBs) have attracted much attention and evolved significant development because of the low price, safety, and similar property compared with Li‐ion batteries. Due to the high reversibility, stability, and low potential plateau, graphite becomes a current research focus and is regarded as one of the most promising KIB's anode materials. In this review, we mainly discuss the electrochemical reaction mechanism of graphite during potassiation‐depotassiation process and analyze the effects of electrode/electrolyte interface on graphite for K‐ion storage. Besides, we summarize several kinds of methods to improve the performance of graphite for KIBs, including the design of graphite structure, selection of appropriate binder, solvent chemistry, and salt chemistry. Meanwhile, a concept of “relative energy density” is raised, which can be more accurate to evaluate the genuine electrochemical performance of graphite anode involving the specific capacity and potential. In addition, we also summarize the considerable challenges to current graphite anode in KIBs and we believe our work will offer alterative solutions to further explore high‐performance graphite anode of K‐ion storage.

Advances in Underground Energy Storage for Renewable Energy Sources

The use of fossil fuels (coal, fuel, and natural gas) to generate electricity has been reduced in the European Union during the last few years, involving a significant decrease in greenhouse gas emissions [...]

Green hydrogen: A new flexibility source for security constrained scheduling of power systems with renewable energies

Green hydrogen, i.e. the hydrogen generated from renewable energy sources (RES) will significantly contribute to a successful energy transition. Besides, to facilitate the integration and storage of RES, this promising energy carrier is well capable to efficiently link various energy sectors. By introduction of green hydrogen as a new flexibility source to power systems, it is necessary to investigate its possible impacts on the generation scheduling and power system security. In this paper, a security-constrained multi-period optimal power flow (SC-MPOPF) model is developed aiming to determine the optimal hourly dispatch of generators as well as power to hydrogen (P2H) units in the presence of large-scale renewable energy sources (RES). The proposed model characterizes the P2H demand flexibility in the proposed SC-MPOPF model, taking into account the electrolyzer behavior, reactive power support of P2H demands and hydrogen storage capability. The developed SC-MPOPF model is applied to IEEE 39-bus system and the obtained numerical results demonstrate the role of P2H flexibility on cost as well as RES's power curtailment reduction.

Synthesis and characterization of Bi-doped g-C3N4 for photoelectrochemical water oxidation

Photoelectrochemical (PEC) water splitting has emerged as a promising technology for the storage of renewable energy sources, via the production of hydrogen, a clean and multi-purpose chemical energy vector. The key component in a PEC cell is the photoanode where light energy is absorbed and transformed into electron-hole pairs of appropriate energy for water photo-oxidation. We report on the synthesis of g-C3N4 materials, with an elongated nano-structure, fabricated by the direct pyrolysis of supramolecular melamine used as a chemical precursor. The as-prepared material was used to host specific amounts of bismuth, a doping element used to adjust the band gap of the hosting matrix. The presence of Bi in the photoanodes was confirmed by energy dispersive x-ray analysis (EDX) analysis. Powder X-ray (p-XRD) and Fourier transform infrared (FT-IR) measurements performed on the photoanodes confirmed the absence of Bi-based oxides, and showed that bismuth may bonded to nitrogen atoms inside the voids of the g-C3N4 skeleton. Differential reflective spectroscopy (DRS) measurements revealed that the band gap energy was reduced upon introduction of Bi into g-C3N4. From photoluminescence (PL) plots, it was observed that the 2.5% Bi doping induced a 6-fold electron-hole separation, compared to the pristine g-C3N4. PEC water splitting measurements showed that 2.5% Bi doping approximately doubled the activity of g-C3N4 towards water oxidation. Electrochemical impedance spectroscopy (EIS) measurements showed that Bi doping was an effective method for decreasing the charge transfer across the electrode/electrolyte interface; 2.5% Bi-g-C3N4 was reduced by around 2.4 times compared to that of pristine g-C3N4. Bode-phase plots accompanied EIS spectra revealed that the lifetime of the photo-generated electrons in neat g-C3N4 was improved as a result of Bi doping. The band gaps and the positions of the valence and conduction bands were determined from Mott–Schottky plots.

Manganese Complexes: Hydrogen Generation and Oxidation

Innovative breakthroughs by designing cheap, sustainable and efficient systems for the conversion and storage of renewable energy sources can help to solve the energy demand. An economically viable way could be the production of hydrogen. Designing noble metal‐free catalysts can play an important role in the path towards sustainable hydrogen economy. Nobel metal catalysts are limited by their cost and scalability. In nature, the hydrogenases and photosystem II use iron, nickel and manganese ions for catalysis. Drawing inspiration from nature, several attempts have been made by chemists to design cheap and robust catalysts. Though there are many reviews on the Fe and Ni complexes, there are very few that have discussed Mn. Therefore, in this review a comprehensive description is given on Mn‐based complexes reported as catalysts for the hydrogen evolution and oxidation reactions.

Sodium Titanate Material for Sodium-Ion Battery

The current top leading electrochemical system for energy storage is lithium-ion battery. This kind of battery become commercially available in year 1991, it is almost 30 years ago. The technology and human society evolution of that time was different form the technology of the contemporary world. New applications like off or on grid stationary energy storage systems with power in orders of megawatts. These new applications totally differ from the original intention for using of lithium-ion batteries in smart portable devices like camera. These applications have specific requirements as low cost, sustainable environmentally friendly energy storages. The lithium-ion batteries are adapted for these applications, but the economic and environment point of view mirror the fact that we need another electrochemical system for these applications that will better respect their requirements. In case of energy storage for renewable energy sources, as the most promising seems to be a sodium-ion battery.

Flexible and Scalable Energy Management of Islanded Renewable Energy Sources Storage Systems

Power management in islanded off-grid hybrid power-to-power (P2P) systems is challenging due to multiple decisions that need to be taken at each time instance within a perpetually changing environment. In this work, an energy management strategy (EMS) is proposed as a supervisory control framework that relies on a finite state machine (FSM) approach. The FSM offers a systematic way to develop a flexible decision-making algorithm that is combined with propositional-based logic in order to describe the transitions between the different operating states of the integrated system’s components. Easy extension of the EMS to larger and more complex systems without compromising the operational objectives is the major contribution of the developed algorithm. The proposed approach is implemented in an off-grid demonstration site located in Ginostra, Italy. At this site, the only source of power is a photovoltaic (PV) installation array that supports the specified residential loads. An operation analysis is conducted accompanied by an assessment of the site’s environmental footprint. The results indicate that power is supplied without interruption to the load, and CO2 emissions are decreased by 95.6 % in comparison with the former energy solution applied (diesel generators – DSG).

An organic ligand promoting the electrocatalytic activity of cobalt oxide for the hydrogen evolution reaction

In electrocatalytic water splitting, active, stable and low-cost hydrogen evolution electrocatalysts play key roles in the conversion and storage of renewable energy sources.

Microgrid Control Based on the Use and Storage of Renewable Energy Sources

Technological and functional diagrams of control by microgrid objects based on wind and photovoltaic installations using pumped-storage power plants, as well as a new control device for low-power energy plants, are considered in the work.

Review on Health Management System for Lithium-Ion Batteries of Electric Vehicles

The battery is the most ideal power source of the twenty-first century, and has a bright future in many applications, such as portable consumer electronics, electric vehicles (EVs), military and aerospace systems, and power storage for renewable energy sources, because of its many advantages that make it the most promising technology. EVs are viewed as one of the novel solutions to land transport systems, as they reduce overdependence on fossil energy. With the current growth of EVs, it calls for innovative ways of supplementing EVs power, as overdependence on electric power may add to expensive loads on the power grid. However lithium-ion batteries (LIBs) for EVs have high capacity, and large serial/parallel numbers, when coupled with problems like safety, durability, uniformity, and cost imposes limitations on the wide application of lithium-ion batteries in EVs. These LIBs face a major challenge of battery life, which research has shown can be extended by cell balancing. The common areas under which these batteries operate with safety and reliability require the effective control and management of battery health systems. A great deal of research is being carried out to see that this technology does not lead to failure in the applications, as its failure may lead to catastrophes or lessen performance. This paper, through an analytical review of the literature, gives a brief introduction to battery management system (BMS), opportunities, and challenges, and provides a future research agenda on battery health management. With issues raised in this review paper, further exploration is essential.

Electrodeposited-film electrodes derived from a precursor dinitrosyl iron complex for electrocatalytic water splitting.

In artificial photosynthesis, water splitting plays an important role for the conversion and storage of renewable energy sources. Here, we report a study on the electrocatalytic properties of the electrodeposited-film electrodes derived from irreversible electro-reduction/-oxidation of a molecular dinitrosyl iron complex (DNIC) {Fe(NO)2}9 [(Me6tren)Fe(NO)2]+ (Me6tren = tris[2-(dimethylamino)ethyl]amine) for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in alkaline solution, individually. For HER, the overpotential and Tafel slope for the electrodeposited-film cathode are lower than those of the equiv.-weight Pt/C electrode. The electrodeposited-film anode for the OER is stable for 139 h. Integration of the electrodeposited-film cathode and anode into a single electrode-pair device for electrocatalytic water splitting exhibits an onset voltage of 1.77 V, achieving a geometrical current density of 10 mA cm-2.