The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

Microgrids energy management systems: A critical review on methods, solutions, and prospects

Renewable energy, such as hydro power, photovoltaics and wind turbines, has become the most widely applied solutions for addressing issues associated with oil depletion, increasing energy demand and anthropogenic global warming. Solar and wind energy are strongly dependent on weather resources with intermittent and fluctuating features. To filter these variabilities, battery energy storage systems have been broadly accepted as one of the potential solutions, with advantages such as fast response capability, sustained power delivery, and geographical independence. During the implementation of battery energy storage systems, one of the most crucial issues is to optimally determine the size of the battery for balancing the trade-off between the technical improvements brought by the battery and the additional overall cost. Numerous studies have been performed to optimise battery sizing for different renewable energy systems using a range of criteria and methods. This paper provides a comprehensive review of battery sizing criteria, methods and its applications in various renewable energy systems. The applications for storage systems have been categorised based on the specific renewable energy system that the battery storage will be a part. This is in contrast to previous studies where the battery sizing approaches were either arranged as an optimised component in renewable systems or only accounted for one category of renewable system. By taking this approach, it becomes clear that the critical metrics for battery sizing, and by extension the most suitable method for determining battery size, are determined by the type of renewable energy system application, as well as its size. This has important implications for the design process as the renewable energy system application will drive the battery energy storage system sizing methodology chosen.

Battery energy storage system size determination in renewable energy systems: A review

A microgrid (MG) is a local entity that consists of distributed energy resources (DERs) to achieve local power reliability and sustainable energy utilization. The MG concept or renewable energy technologies integrated with energy storage systems (ESS) have gained increasing interest and popularity because it can store energy at off-peak hours and supply energy at peak hours. However, existing ESS technology faces challenges in storing energy due to various issues, such as charging/discharging, safety, reliability, size, cost, life cycle, and overall management. Thus, an advanced ESS is required with regard to capacity, protection, control interface, energy management, and characteristics to enhance the performance of ESS in MG applications. This paper comprehensively reviews the types of ESS technologies, ESS structures along with their configurations, classifications, features, energy conversion, and evaluation process. Moreover, details on the advantages and disadvantages of ESS in MG applications have been analyzed based on the process of energy formations, material selection, power transfer mechanism, capacity, efficiency, and cycle period. Existing reviews critically demonstrate the current technologies for ESS in MG applications. However, the optimum management of ESSs for efficient MG operation remains a challenge in modern power system networks. This review also highlights the key factors, issues, and challenges with possible recommendations for the further development of ESS in future MG applications. All the highlighted insights of this review significantly contribute to the increasing effort toward the development of a cost-effective and efficient ESS model with a prolonged life cycle for sustainable MG implementation.

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Review of Energy Storage System Technologies in Microgrid Applications: Issues and Challenges

The deployment of energy storage systems (ESSs) is a significant avenue for maximising the energy efficiency of a distribution network, and overall network performance can be enhanced by their optimal placement, sizing, and operation. An optimally sized and placed ESS can facilitate peak energy demand fulfilment, enhance the benefits from the integration of renewables and distributed energy sources, aid power quality management, and reduce distribution network expansion costs. This paper provides an overview of optimal ESS placement, sizing, and operation. It considers a range of grid scenarios, targeted performance objectives, applied strategies, ESS types, and advantages and limitations of the proposed systems and approaches. While batteries are widely used as ESSs in various applications, the detailed comparative analysis of ESS technical characteristics suggests that flywheel energy storage (FES) also warrants consideration in some distribution network scenarios. This research provides recommendations for related requirements or procedures, appropriate ESS selection, smart ESS charging and discharging, ESS sizing, placement and operation, and power quality issues. Furthermore, this study identifies future research opportunities in relation to challenges for optimal ESS placement planning, development and implementation issues, optimisation techniques, social impacts, and energy security.

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Overview of energy storage systems in distribution networks: Placement, sizing, operation, and power quality

This paper presents a new concept for district energy (DE) systems using central battery storage and decentralized hybrid renewable systems. The proposed DE consists of five buildings integrated with centralized 300 (V), 6.5 (A.h) batteries, locally distributed generations such as 8.5 (kW) wind turbines and 10 (kW) solar cells rated at 110 (V) and three‐phase loads. The central battery can be connected to each home for exchanging power. To increase the resilience, the proposed control system connects home 1 to the external 380 (V) and 50 (Hz) network when the battery is operating above the limited power (ie, 50 [kW] for this case study). The connection to the external grid is done by assessing and confirming a set of necessary conditions. The proposed integrated control system for DE is designed to achieve the following objectives: maximum power extraction from local wind/solar units by maximum power point tracking, optimal charge‐discharge process for central battery, connecting DE to the upstream network under outages and supplying the loads under all operating conditions. These goals are investigated by implementing six different scenarios of performance. In scenario 1, wind and solar units produce 6.6 (kW) and 24 (kW), respectively. Therefore, to feed the total load of 42.5 (kW), the central battery produces 15 (kW). In scenario 2, the total load in the first step is 35 (kW) and it is 95 (kW) in the second step. The power of solar and wind units in both loading steps is constant. The battery power increases from 6.5 (kW) absorption in the first step to 22 (kW) injections in the second step. In scenario 3, the solar units are switched off and in scenario 4, both solar and wind units are switched off. In such conditions, the battery responds to supply loads of homes. Increasing the energy resilience of DE during grid outages is modeled in scenario 5; where the battery power increases from 21 to 51.7 (kW) to deal with such outages. The nonlinear simulations in MATLAB/SIMULINK software show that the developed control strategy is able to control local renewable energies as well as the central battery while increasing the resilience and harvesting maximum power from decentralized wind/solar units.

A novel resilient concept for district energy system based on central battery and decentral hybrid generating resources

District energy systems (DESs) and integrated electricity-gas systems (IEGSs) are closely related. The performance of these systems under critical situations, such as faults and equipment outages, has not been adequately investigated. The operation of DESs may also be significantly affected by installing central generating systems for gas or electricity sectors. These central generating units may deal with outages and faults. In the literature, there is not a comprehensive model that considers renewables in IEGS, uncertainties of generating systems, mutual connection between electricity and gas sub-grids, ability of exchanging power with upstream grid, centralized storage device for electrical sector, and centralized power supply for gas sector. All these points are considered and modeled in the proposed model. This paper presents several multi-purpose control strategies for DES that are designed and implemented on an IEGS. Electricity and thermal loads are used to model the DES energy needs. In the electricity subsystem, by using several local renewable energy sources (RESs) and a central battery, not only the electric loads are supplied, but also the DES can be connected to the upstream grid and trade the scheduled power in accordance with the electricity market contract in all normal and critical conditions. On the other hand, the gas subsystem is powered by a central fuel cell. Gas and electricity subsystems in the DES region are designed to assist each other during outages and events in order to increase the resilience. All RESs, central battery, and fuel cell are equipped with individual controllers to achieve the above objectives. A centralized control framework is used to manage all these controllers under a variety of operating conditions. Numerical simulations in MATLAB software verify the model ability to control DES and IEGS properly. 

Centralized Multifunctional Control of Integrated Electricity-Gas Network in District Energy System Considering Resilience

Nowadays, the resilience enhancement is one of the most important concerns in electric power networks. The division of the main microgrid into several sub-microgrids, i.e., microgrid formation (MF), is a resilient strategy for distribution systems against natural disasters and cyber-physical attacks. Such effective solution not only increases the resilience and load restoration but also reduces the costs. The extensive penetration of renewable resources in microgrids increases the issues about safe operation under faults. This chapter presents a resilient microgrid formation in the presence of solar, wind, and diesel Distributed generation (DG) for load restoration maximization. In order to carry out the microgrid formation, several candidate breakers and tie-line switches are considered, and their optimal on-off conditions are determined. Both the active and reactive powers are included in the model. The model is expressed as mixed-integer linear programming (MILP) and is simulated under three various cases including case 1, without formation strategy; case 2, formation strategy with line breaker switch; and case 3, formation strategy with both line and tie breaker switches. The numerical results are carried out based on IEEE 33-bus and 69-bus standard distribution networks. The results emphasize on the effectiveness of the developed formation strategy with both the breaker and tie line switches for load restoration and resilience enhancement.

Microgrid Formation Strategy Including Multiple Energy and Capacity Resources for Resilience Improvement

Multi-objective and resilient control on hybrid wind farms under healthy/faulty and off-grid/grid-tied states

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Reza Hemmati

Papers

A novel resilient concept for district energy system based on central battery and decentral hybrid generating resources

Centralized Multifunctional Control of Integrated Electricity-Gas Network in District Energy System Considering Resilience

Microgrid Formation Strategy Including Multiple Energy and Capacity Resources for Resilience Improvement

Multi-objective and resilient control on hybrid wind farms under healthy/faulty and off-grid/grid-tied states

Proračun kratkih optičkih impulsa pomoću pasivnog diodnog lasera Q-uključivanja s dva dijela