Results 1 - 10 of 127
Results 1 - 10 of 127. Search took: 0.02 seconds
|Sort by: date | relevance|
[en] Highlights: ► Super-capacitors are used to store regenerative braking energy in a metro network. ► A novel approach is proposed to model easily and accurately the metro network. ► An efficient approach is proposed to calculate the required super-capacitors. ► Maximum energy saving is around 44% at off-peak period and 42% at peak period. ► Benefit/cost analyses are performed for the suggested ESS. - Abstract: In this paper, the stationary super-capacitors are used to store a metro network regenerative braking energy. In order to estimate the required energy storage systems (ESSs), line 3 of Tehran metro network is modeled through a novel approach, in peak and off-peak conditions based on the real data obtained from Tehran metro office. A useful method is proposed to predict the maximum instantaneous regenerative energy which is delivered to each station before applying ESS and based on that the ESS configuration for each station is determined. Finally, the effectiveness of the proposed ESS is confirmed by economic evaluations and benefit/cost analyses on line 3 of Tehran metro network.
[en] Highlights: ► PV systems with sun tracking and concentrators (CPVS) can reduce the cost of energy per kWh produced. ► The V-trough low-concentration system solution is compatible with flat PV module technologies. ► Optical, thermal and electrical models are needed to forecast real power production. ► The description of a PV grid connected system with batteries, a one-axis tracker and CPV photovoltaic system is presented. ► Outdoor measurements of the generating system are provided and discussed. - Abstract: Photovoltaic systems (PVSs) combined with either some form of storage, such as a battery energy storage system (BESS), or direct load control, can play a crucial role in achieving a more economical operation of the electric utility system while enhancing its reliability with additional energy sources. At the same time, it is also important to use cost-effective PV solutions. In this context, a low-concentration PVS (CPVS) is analysed as a feasible alternative. This paper, present a case study of a complex PVS, composed of two PVSs, a storage system (BEES) and an inverter that allows the system to operate in both the island and grid-connected modes. The first PVS, is a 2.76-kWp single-axis tracking system (azimuth) with modules facing south and tilted 30°, while the second PVS is a dual-axis tracking system, rated 860 Wp, consisting of a concentrator at the flat mirrors (DoubleSun® Four). The system is installed on the roof of the main building of the “ITIS Marconi” school (Italy). A detailed description of the system is provided, and preliminary operating data are presented and discussed. The efficiencies of the PV systems are calculated and measured to evaluate the cost effectiveness of a low-concentration system.
[en] Highlights: • A review of power converter interfaces for electrochemical energy storage (EES) system is presented. • EES devices and their specificities regarding to integration with the electrical systems are also described. • Power converters are divided into standard, multilevel and multiport technology. • The smart storage concept and the interface requirements to integrate the EES devices are also reviewed. - Abstract: Energy storage concept that supports important technologies for electrical systems is well established and widely recognized. Several energy storage techniques are available, including an electrochemical energy storage system used to support electrical systems. These storage systems require interfaces based on power electronic converters for interconnection with an electrical system. This paper reviews the literature covering the various types of interfaces developed for electrochemical energy storage systems. Different electrochemical energy storage devices and their specificities regarding to integration with the electrical systems are described. . The various power converter interfaces that can be used for electrochemical energy storage systems are presented. These interfaces have been divided into standard, multilevel and multiport technology. The main characteristics and specificity of each topology considering its application to electrochemical energy storage systems are presented. The review also covers the smart storage concept and the requirements of the interface to integrate the electrochemical energy storage devices upon this concept
[en] Highlights: • The control of a hybrid storage system using a Three Level NPC converter is analysed. • A sinusoidal PWM with an offset injection is used to control the storage system. • The operation of the selected converter is analysed in its entire operation range. • The operational limits of the Three Level NPC converter are defined. - Abstract: This work analyses the use of a Three-Level Neutral Point Clamped (3LNPC) converter to control the power flow of a Hybrid Energy Storage System (HESS) and at the same time interconnect it with the common AC bus of a microgrid. Nowadays there is not any storage technology capable of offering a high energy storage capacity, a high power capacity and a fast response at the same time. Therefore, the necessity of hybridising more than one storage technology is a widely accepted idea in order to satisfy the mentioned requirements. This work shows how the operational limits of the 3LNPC converter can be calculated and integrated in a control structure to facilitate an optimal use of the HESS according to the rules fixed by the user
[en] Highlights: • Little study reviews the load shifting control using different facilities. • This study reviews load shifting control using building thermal mass. • This study reviews load shifting control using thermal energy storage systems. • This study reviews load shifting control using phase change material. • Efforts for developing more applicable load shifting control are addressed. - Abstract: For decades, load shifting control, one of most effective peak demand management methods, has attracted increasing attentions from both researchers and engineers. Different load shifting control strategies have been developed when diverse cold thermal energy storage facilities are used in commercial buildings. The facilities include building thermal mass (BTM), thermal energy storage system (TES) and phase change material (PCM). Little study has systematically reviewed these load shifting control strategies and therefore this study presents a comprehensive review of peak load shifting control strategies using these thermal energy storage facilities in commercial buildings. The research and applications of the load shifting control strategies are presented and discussed. The further efforts needed for developing more applicable load shifting control strategies using the facilities are also addressed
[en] Highlights: ► The system model is embedded in a dynamic decision model. ► The model has been applied to a specific case study. ► Optimal results are reported for two main cases: the presence/absence of the energy storage system. - Abstract: Renewable energy sources (RES) are an “indigenous” environmental option, economically competitive with conventional power generation where good wind and solar resources are available. Hybrid systems can help in improving the economic and environmental sustainability of renewable energy systems to fulfill the energy demand. The aim of this paper is to present a dynamic model able to integrate different RES and one storage device to feed a “Green” building for its thermal and electrical energy needs in a sustainable way. The system model is embedded in a dynamic decision model and is used to optimize a quite complex hybrid system connected to the grid which can exploit different renewable energy sources. A Model Predictive Control (MPC) is adopted to find the optimal solution. The optimization model has been applied to a case study where electric energy is also used to pump water for domestic use. Optimal results are reported for two main cases: the presence/absence of the energy storage system.
[en] Highlights: • Control of BES for smoothing and hourly dispatch of a PV farm output is developed. • Optimal control strategy for SOC and size of BES are evaluated using GA. • Effectiveness of the control system has been investigated for the case of Malaysia. • The proposed optimal SOC feedback controller has been found effective. • Payback calculations of BES investment is given to highlight the economic benefits. - Abstract: The effects of intermittent cloud and changes in temperature cause a randomly fluctuated output of a photovoltaic (PV) system. To mitigate the PV system impacts particularly on a weak electricity network, battery energy storage (BES) system is an effective means to smooth out the power fluctuations. Consequently, the net power injected to the electricity grid by PV and BES (PV/BES) systems can be dispatched smoothly such as on an hourly basis. This paper presents an improved control strategy for a grid-connected hybrid PV/BES systems for mitigating PV farm output power fluctuations. A feedback controller for BES state of charge is proposed, where the control parameters are optimized using genetic algorithm (GA). GA-based multi objective optimization utilizes the daily average PV farm output power profile which was obtained from simulation using the historical PV system input data of Malaysia. In this way, the optimal size for the BES is also determined to hourly dispatch a 1.2 MW PV farm. A case study for Malaysia is carried out to evaluate the effectiveness of the proposed control scheme using PSCAD/EMTDC software package. Furthermore, the validation of results of the proposed controller and BES size on the actual PV system output data are also given. Finally, a simple payback calculation is presented to study the economical aspects of the BES investment on the proposed mitigation strategy under Malaysian Feed-in Tariff program
[en] Highlights: • In this paper an expert energy management system (EEMS) is presented. • A power forecasting module for wind generation capacity is presented. • The objective functions that must be minimized are operating cost and net emission. • A smart energy storage system (EES) for electrochemical batteries is presented. • A new modified Bacterial Foraging Optimization (MBFO) algorithm is presented. - Abstract: Recently, the use of wind generation has rapidly increased in micro-grids. Due to the fluctuation of wind power, it is difficult to schedule wind turbines (WTs) with other distributed energy resources (DERs). In this paper, we propose an expert energy management system (EEMS) for optimal operation of WTs and other DERs in an interconnected micro-grid. The main purpose of the proposed EEMS is to find the optimal set points of DERs and storage devices, in such a way that the total operation cost and the net emission are simultaneously minimized. The EEMS consists of wind power forecasting module, smart energy storage system (ESS) module and optimization module. For optimal scheduling of WTs, the power forecasting module determines the possible available capacity of wind generation in the micro-grid. To do this, first, an artificial neural network (ANN) is used to forecast wind speed. Then, the obtaining results are used considering forecasting uncertainty by the probabilistic concept of confidence interval. To reduce the fluctuations of wind power generation and improve the micro-grid performances, a smart energy storage system (ESS) module is used. For optimal management of the ESS, the comprehensive mathematical model with practical constraints is extracted. Finally, an efficient modified Bacterial Foraging Optimization (MBFO) module is proposed to solve the multi-objective problem. An interactive fuzzy satisfying method is also used to simulate the trade-off between the conflicting objectives (cost and emission). To evaluate the proposed algorithm, the EEMS is applied to a typical micro-grid which consists of various DERs, smart ESS and electrical loads. The results show that the EEMS can effectively coordinate the power generation of DERs and ESS with respect to economic and environmental considerations
[en] The major technical issue in gas hydrates energy storage systems is how to increase the refrigerants-water mass and heat transfer and how to realize a rapid formation of clathrate hydrate. Borrowing ideas from heat transfer enhancement of the fluid with the addition of nano-sized particles, the formation and dissociation of HFC134a (CH2FCF3) hydrate were studied in nano-copper suspensions of different mass fractions. The experimental results indicate that the addition of nano-copper enhances the heat and mass transfer process of HFC134a hydrate formation, which was shortened with the increasing mass fraction of nano-copper. Compared with the dissociation pressure at a given temperature below the critical dissociation point, a significant upward shift of the dissociation pressure of the HFC134a hydrate formed in the nano-fluid was observed. The critical dissociation point shifts from the former point (283.15 K, 414.86 kPa) to the latter one (282.65 K, 401.35 kPa), and the dissociation curve does not shift with the change of mass fraction of the nano-copper
[en] Highlights: • The ReSOC EES system can achieve LCOS • Balance-of-plant hardware can be compatible between operating modes. • Storage tank dynamics have minimal impact on system performance. • The ReSOC system can operate down to 15% of rated capacity and with RTE of 54%. • The ReSOC system investigated is economically competitive with other technologies. - Abstract: Reversible solid oxide cells may be a cost competitive energy storage technology at the distributed scale. Leveraging C–O–H chemistry and operating near 600 °C allows the cells to be exothermic in both modes, improving efficiency and operability. This study characterizes ReSOC balance-of-plant hardware off-design performance to investigate component mode compatibility, the effect of tank dynamics, and part-load performance for a 100 kW/800 kWh plant. We also introduce a variable volume floating piston tank concept to improve energy storage density and evaluate operability advantages. Results show that with proper system design, balance-of-plant components are compatible, and tank dynamics have minimal impact when tanks are uninsulated and designed for storage near ambient temperature. System AC roundtrip efficiency is between 53% and 54%, depending on the tank technology selected and the compressor operating approach. Energy density is 84.4 kWh/m3 for rigid tanks, and 146.1 kWh/m3 for the variable volume tank concept at 100 bar storage pressure. This study also shows that ReSOC systems can maintain high efficiency at part-loads as low as 15% of rated capacity. Economic analysis of the system estimates an installed capital cost of $422–452/kWh, and a levelized cost of storage of 18.8–19.6 ¢/kWh, values competitive with state-of-the-art battery technology.