The resistance−capacitance (RC) model is one of the most applicable circuits for modeling the charging and discharging processes of supercapacitors (SCs). Although this circuit is usually used in the electric and thermal investigation of the performance of SCs, it does not include leakage currents. This paper presents exact analytical formulas of leakage-current-based supercapacitor models that can be used in industrial applications, i.e., constant-power-based applications. In the proposed model, current and voltage are represented as a solution of nonlinear equations that are solved using the standard Newton method. The proposed expressions’ accuracy is compared with the results obtained using traditional numerical integration methods with leakage current formulation and other methods, found in the literature, with no leakage current formulation. The results confirm that including leakage current represents a more accurate and realistic manner of modeling SCs. The results show that th... [more]

The cryogenic carbon capture (CCC) process is a promising post-combustion CO2 removal method. This method is very novel compared with conventional and well-developed methods. However, cryogenic carbon capture is not yet commercially available despite its techno-economic benefits. Thus, a model-based design approach for this process can provide valuable information. This paper will first introduce the cryogenic carbon capture process. Then, a comprehensive literature overview that focuses on different methods for modeling the process at the component level will be given. The modelling methods which are deemed most effective are presented more in depth for each of the key system components. These methods are compared with each other in terms of complexity and accuracy and the simplest methods with an acceptable level of precision for modelling a specific component in the CCC process are recommended. Furthermore, potential research areas in modeling and simulation of the CCC process are a... [more]

In the future, there will be more and more abandoned oil-gas wells with the exploitation of onshore oilfield resources. However, the large height difference in abandoned oil-gas wells can be used as building blocks for gravity power generation, thus maximizing the economic value of abandoned oil-gas wells. In this study, a scheme of gravity power generation by virtue of the spud-in casing depth of oil-gas wells is proposed, and a gravity power generation model based on abandoned oil-gas wells is established. The parameters and economic benefits of gravity energy storage are calculated for oil-gas wells in the Huabei oilfield, the Daqing oilfield, and the Xinjiang oilfield. It is shown that the power density and discharge time of the gravity energy storage system in abandoned oil-gas wells are suitable for distributed power generation. In addition, the fast response characteristics of energy storage in abandoned oil-gas wells are verified, which makes the system suitable for correcting... [more]

An energy storage system based on a Proton Exchange Membrane (PEM) electrolyzer system, which could be managed by a nanoGrid for Home Applications (nGfHA), is able to convert the surplus of electric energy produced by renewable sources into hydrogen, which can be stored in pressurized tanks. The PEM electrolyzer system must be able to operate at variable feeding power for converting all the surplus of renewable electric energy into hydrogen in reasonable time. In this article, the dynamic electric simulation model of a PEM electrolyzer system with its pressurized hydrogen tanks is developed in a proper calculation environment. Through the calculation code, the stack voltage and current peaks to a supply power variation from the minimum value (about 56 W) to the maximum value (about 440 W) are controlled and zeroed to preserve the stack, the best range of the operating stack current is evaluated, and hydrogen production is monitored.

Bidirectional DC/DC converters are widely adopted in new energy power generation systems. Because of the low conversion efficiency and non-isolation for conventional, bidirectional DC/DC converters in the photovoltaic energy storage complementary system, this paper proposes a bidirectional isolation LLC converter topology, with compensating inductance for the energy storage system; it has excellent characteristics, such as wide input voltage range and soft switching in full-load range. First, an AC equivalent model based on the fundamental wave equivalent method is established to derive the voltage gain. Meanwhile, a small signal model is also built to design a reasonably closed-looped controller. Finally, the improved bidirectional LLC resonant converter is applied to the photovoltaic energy storage complementary system. The correctness and feasibility for the bidirectional LLC converter topology under the proposed charging and discharging control strategy of the DC bus are verified b... [more]

Thermo-mechanical energy storage can be a cost-effective solution to provide flexibility and balance highly renewable energy systems. Here, we present a concise review of emerging thermo-mechanical energy storage solutions focusing on their commercial development. Under a unified framework, we review technologies that have proven to work conceptually through project demonstration at a scale above 1 MW by describing the current state of commercial development, quantifying techno-economic parameters, outlining the challenges, and assessing each technology’s potential for commercial viability. The levelized cost of storage for thermo-mechanical energy storage at storage duration between 8 h and 1 week is cheaper than that of lithium-ion batteries and hydrogen storage; however, energy storage for such duration does not pay for itself at the current renewable penetration levels. For medium-term energy storage to be viable, at the realistic storage cost of 15 USD/kWh to 40 USD/kWh, the inves... [more]

This paper aims to analyse two energy storage methods—batteries and hydrogen storage technologies—that in some cases are treated as complementary technologies, but in other ones they are considered opposed technologies. A detailed technical description of each technology will allow to understand the evolution of batteries and hydrogen storage technologies: batteries looking for higher energy capacity and lower maintenance, while hydrogen storage technologies pursuing better volumetric and gravimetric densities. Additionally, as energy storage systems, a mathematical model is required to know the state of charge of the system. For this purpose, a mathematical model is proposed for conventional batteries, for compressed hydrogen tanks, for liquid hydrogen storage and for metal hydride tanks, which makes it possible to integrate energy storage systems into management strategies that aim to solve the energy balance in plants based on hybrid energy storage systems. From the technical point... [more]

Increased renewable energy production and storage is a key pillar of net-zero emission. The expected growth in the exploitation of offshore renewable energy sources, e.g., wind, provides an opportunity for decarbonising offshore assets and mitigating anthropogenic climate change, which requires developing and using efficient and reliable energy storage solutions offshore. The present work reviews energy storage systems with a potential for offshore environments and discusses the opportunities for their deployment. The capabilities of the storage solutions are examined and mapped based on the available literature. Selected technologies with the largest potential for offshore deployment are thoroughly analysed. A landscape of technologies for both short- and long-term storage is presented as an opportunity to repurpose offshore assets that are difficult to decarbonise.

A plethora of multi-functional materials with properties that can be adjusted and tuned to meet the needs of energy storage and conversion has emerged over the last years [...]

As wearable electronic devices are becoming an integral part of modern life, there is a vast demand for safe and efficient energy storage devices to power them. While the research and development of microbatteries and supercapacitors (SCs) have significantly progressed, the latter has attracted much attention due to their excellent power density, longevity, and safety. Furthermore, SCs with a 1D fiber shape are preferred because of their ease of integration into today’s smart garments and other wearable devices. Fiber supercapacitors based on carbon nanotubes (CNT) are promising candidates with a unique 1D structure, high electrical and thermal conductivity, outstanding flexibility, excellent mechanical strength, and low gravimetric density. This review aims to serve as a comprehensive publication presenting the fundamentals and recent developments on CNT-fiber-based SCs. The first section gives a general overview of the supercapacitor types based on the charge storage mechanisms and e... [more]

Slovenia is a Central European country with a long history of hydropower. This paper gives a brief introduction to the current status of hydropower utilization and informs about some selected successful examples of hydropower plant operation. One such example is fish passage and flood risk reduction on the lower reaches of the Sava River at the Brežice hydroelectric power plant, taking into account a complex of morphological, hydrological, hydraulic, and anthropogenic factors. Future development is considered against the background of the National Energy and Climate Plan, which does not envisage any significant expansion in the capacity or function of the hydropower sector. The envisaged capacity increase is from the current 4430 GWh to around 4580 GWh by 2030. It is shown that the current energy storage capacity of Slovenia’s only pumped storage plant will be sufficient to offset the introduction of new non-dispatchable renewable energy sources by 2030. By around 2028, the country wil... [more]

Moving towards clean energy generation seems essential. To do so, renewable energy penetration is growing in the power systems. Although energy sources such as wind and solar are clean, they are not available consistently. Using energy storage will help to tackle variability. Liquid air energy storage is gaining attention among different energy storage technologies, as it is a promising option for grid-scale energy storage. This paper presents a detailed mixed integer linear model of liquid air energy storage to be used in scheduling and planning problems. A comprehensive cycle diagram of different processes of liquid air energy storage is presented, and a model has been developed accordingly. Simulations of the proposed model are carried out for the power system of Tenerife island and compared with the basic models. Basic models overlook specific characteristics of liquid air energy storage systems, such as charging and discharging start energy. Results confirm that the use of simple... [more]

The energy storage is an important character for sustainable energy structures and the prospective future economy. This paper aims to propose a multi-attribute decision analysis (MADA) approach to prioritize and choose the energy storage system (ESS) alternatives in terms of the different technical, economic, environmental and social aspects of them. In this line, an integrated approach is developed with the combination of intuitionistic fuzzy sets (IFSs), a method using the removal effects of criteria (MEREC), rank sum (RS) and the measurement of the alternatives and ranking based on compromise solution (MARCOS) methods for prioritizing the ESSs. The IF-MEREC-RS was used to find the integrated weight by combining the objective and subjective weights of the different indicators for prioritizing the ESSs. The MARCOS method was implemented to rank the various ESSs over several crucial indicators of sustainability. The practical outcome illustrates that the Li-ion battery (LIB) is the bes... [more]

Electrical energy storage systems have a fundamental role in the energy transition process supporting the penetration of renewable energy sources into the energy mix. Compressed air energy storage (CAES) is a promising energy storage technology, mainly proposed for large-scale applications, that uses compressed air as an energy vector. Although the first document in literature on CAES appeared in 1976 and the first commercial plant was installed in 1978, this technology started to gain attention only in the decade 2000−2010, with remarkable scientific production output and the realization of other pre-commercial demonstrators and commercial plants. This study applies bibliometric techniques to draw a picture of the current status of the scientific progress and analyze the trend of the research on CAES and identify research gaps that can support researchers and manufacturers involved in this entering technology. Recent trends of research include aspects related to the off-design, the de... [more]

To manage the imbalance between energy supply and demand in various energy systems such as energy storage and energy conversion, “phase change materials” are presented as promising options for these applications. To overcome the long-standing disadvantages of PCMs, for instance, small values of thermal conductivity, liquid leakage, separation of phase, and the problem of supercooling, advanced phase change composites (PCCs) manufactured by chemical modifications or the incorporation of functional additives are essential to overcome these disadvantages and promote the large-scale application of PCMs. Herein, we discuss a complete assessment of the recent development and crucial topics concerning PCCs, with a brief description of PCC preparation using different techniques, enhancing PCCs thermal conductivity approaches, and their applications. The various techniques of elaboration of PCCs used can be illustrated as polymerization, encapsulation, and hybrid confinement. Phase change mater... [more]

Functional materials, in the combination of lignocelluloses, known as natural fibers, with oxide materials, can result in cultivating functional properties such as flexibility, relativity good electrical conduction, good electrical charge storage capacity, and tunable electric permittivity. This study presents the morphological, dielectric, and impedance properties of lignocellulose−lead oxide (LC/PbO2) composite sheets electrodeposited with silver metallic nanoparticles for various time spans. The uncoated samples show a rather simple behavior where the impedance data fit well to the two-system model with different relaxation times. On the other side, the impedance spectra of the electrodeposited sample have varying features, which mainly depend upon the deposition thickness of the Ag particles. The common feature is the drift of conductive species, as seen from the straight-line behavior in the Nyquist plots, which were fitted using a Warburg element in the equivalent circuit model.

The enormous number of automobiles across the world has caused a significant increase in emissions of greenhouse gases, which pose a grave and mounting threat to modern life by escalating global warming and polluting air quality. These adverse effects of climate change have motivated the automotive sector to reform and have pushed the drive towards the transformation to fully electric. Charging time has been identified as one of the key barriers in large-scale applications of Electric Vehicles (EVs). In addition, various challenges are associated with the formulation of a safe charging scheme, which is concerned with appropriate charging converter architecture, with the aim of ensuring a safe charging protocol within a range of 5−10 min. This paper provides a systematic review of thharging technologies and their impacts on battery systems, including charger converter design and associated limitations. Furthermore, the knowledge gap and research directions are provided with regard to th... [more]

The proposed anthraquinone-bromate cell combines the advantages of anthraquinone-bromine redox flow batteries and novel hybrid hydrogen-bromate flow batteries. The anthraquinone-2,7-disulfonic acid is of interest as a promising organic negolyte due its high solubility, rapid kinetics of electrode reactions and suitable redox potentials combined with a high chemical stability during redox reactions. Lithium or sodium bromates as posolytes provide an anomalously high discharge current density of order ~A cm−2 due to a novel autocatalytic mechanism. Combining these two systems, we developed a single cell of novel anthraquinone-bromate flow battery, which showed a power density of 1.08 W cm−2, energy density of 16.1 W h L−1 and energy efficiency of 72% after 10 charge−discharge cycles.

This paper numerically models the thermal performance of offshore hydro-pneumatic energy storage (HPES) systems composed of a subsea accumulator pre-charged with a compressed gas. A time-marching numerical approach combining the first law of thermodynamics with heat transfer equations is used to investigate the influence of replacing air within an HPES system with carbon dioxide (CO2). The latter is able to experience a phase change (gas−liquid−gas) during the storage cycle in typical subsea temperatures when limiting the peak operating pressure below the critical point. The influences of integrating a piston and an inner liner within the accumulator to mitigate issues related to gas dissolution in seawater and corrosion are explored. It is found that the energy storage capacity of subsea HPES accumulators increases substantially when CO2 is used as the compressible fluid in lieu of air, irrespective of the accumulator set up. It is also noted that the length-to-diameter ratio of the a... [more]

Due to their attractive properties, such as high energy and power density, Lithium-ion batteries are currently the most suitable energy storage system for powering portable electronic equipment, electric vehicles, etc. However, they are still affected by safety and stability problems that need to be solved to allow a wider range of applications, especially for critical areas such as power networks and aeronautics. In this paper, the issue of overdischarge abuse has been addressed on Lithium-ion cells with different anode materials: a graphite-based anode and a Lithium Titanate Oxide (LTO)-based anode model. Tests were carried out at different depths of discharge (DOD%) in order to determine the effect of DOD% on cell performance and the critical conditions that often make the cell fail irreversibly. Tests on graphite anode cells have shown that at DOD% higher than 110% the cell is damaged irreversibly; while at DOD% lower than 110% electrolyte deposits form on the anodic surface and st... [more]

The importance of renewable energies and energy storage system forming a micro-grid and integrating it to the electrical grid is widely spread. A supervisory system plays a crucial role in controlling, managing, and planning the micro-grid. This paper demonstrates the development of a new custom supervisory system based on Internet of Things (IoT), creating an information sharing environment. The proposed supervisory system is based on open-source tools for a micro-grid, composed of a photovoltaic power plant and a storage system, employing smart devices and making non-smart devices compatible with IoT systems. The new supervisory improves the available system by incorporating new features and devices and increasing the data polling rate when necessary. A comparison between the current supervisory system and the proposed one is performed, showing that the new system is more flexible, easily modified, cost-effective, and more fault-resilient.

Power electronic systems have a great impact on modern society. Their applications target a more sustainable future by minimizing the negative impacts of industrialization on the environment, such as global warming effects and greenhouse gas emission. Power devices based on wide band gap (WBG) material have the potential to deliver a paradigm shift in regard to energy efficiency and working with respect to the devices based on mature silicon (Si). Gallium nitride (GaN) and silicon carbide (SiC) have been treated as one of the most promising WBG materials that allow the performance limits of matured Si switching devices to be significantly exceeded. WBG-based power devices enable fast switching with lower power losses at higher switching frequency and hence, allow the development of high power density and high efficiency power converters. This paper reviews popular SiC and GaN power devices, discusses the associated merits and challenges, and finally their applications in power electron... [more]

The energy sector is nowadays facing new challenges, mainly in the form of a massive shifting towards renewable energy sources as an alternative to fossil fuels and a diffusion of the distributed generation paradigm, which involves the application of small-scale energy generation systems. In this scenario, systems adopting one or more renewable energy sources and capable of producing several forms of energy along with some useful substances, such as fresh water and hydrogen, are a particularly interesting solution. A hybrid polygeneration system based on renewable energy sources can overcome operation problems regarding energy systems where only one energy source is used (solar, wind, biomass) and allows one to use an all-in-one integrated systems in order to match the different loads of a utility. From the point of view of scientific literature, medium- and large-scale systems are the most investigated; nevertheless, more and more attention has also started to be given to small-scale... [more]

Underground salt caverns are widely used in large-scale energy storage, such as natural gas, compressed air, oil, and hydrogen. In order to quickly build large-scale natural gas reserves, an unusual building method was established. The method involves using the existing salt caverns left over from solution mining of salt to build energy storages. In 2007, it was first applied to Jintan Natural Gas Storage of China. Based on this successful project, several existing salt caverns were screened to build energy storages in China. Engineering experience indicates that the key to successful reusing is how to select the most suitable of the numerous available caverns and confirm it. This paper summarizes and reviews relevant theories and testing methods, including: (1) the primary selection principle for using existing salt caverns to build energy storage, (2) the testing method and evaluation theory of tightness of the existing salt cavern, and (3) the typical project case of using the exist... [more]

Near-Zero-Energy Buildings are a challenge in terms of energy production, storage, consumption and management, but these technological solutions remain financially difficult to access in developing countries. To this end, a complete low-cost and reliable home energy-management prototype was first developed and implemented on a scale model. A PWM charge controller drove the flow of energy produced and consumed in order to ensure the optimization of both the consumption of energy and energy savings. Battery storage was also managed by the home automation module using a set of sensors. The prototype of the scale model incorporated complete energy management of all electrical devices with group priorities through a graphical interface in a real-time mode. After testing this system, the lighting management part was implemented in a large-scale smart solar home. A smart lighting system via a complete algorithm integrated on an Arduino Mega board was then realized and implemented in the life-... [more]