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Hydrogen energy storage system (HESS) has excellent potential in high-proportion renewable energy systems due to its high energy density and seasonal storage characteristics. After detailing the volatility of wind speed, irradiance and load, this paper proposes a bi-level optimization model to analyze the economic operation of the wind-photovoltaic-hydrogen hybrid system (WPH-HS). First, the relationship between the source-load output matching and operating conditions of HESS is studied, two evaluation indicators are described, which can be adjusted by wind-solar complementarity on the source side and demand response on the load side. Second, considering the levelized cost of storage (LCOS), the total annual cost (TAC) calculation method of WPH-HS is presented, and this paper provides a new hybrid optimization technology of chaotic search, particle swarm optimization and non-dominated sorting genetic algorithm2. Finally, the system is simulated with the MATLAB software to determine the optimal sizing of components and minimize the LCOS while ensuring the optimal TAC. The simulation results are elaborated in detail. In particular, the added source-load interaction reduces the TAC and LCOS by 7.3% and 10.3%. When two indicators reach 0.03 and 0.1745, the system is economically viable with the LCOS of 0.276 USD/kWh. The hybrid optimization algorithm can achieve better result in fewer iterations. • The cross-season utilization of the hydrogen energy storage system is discussed. • A price bi-level model about the levelized cost of storage and the total annual cost is established. • Evaluation indicators are presented to promote the source-load interaction. • Effects of wind speed, irradiance, and loads are investigated for the levelized cost of storage. • A hybrid optimization algorithm based on three common algorithms is designed. [ABSTRACT FROM AUTHOR]

Local energy sharing (LES) is a concept that enables sharing between distribution system participants such as consumers, producers, and prosumers at the local level in a transparent and cooperative manner. It can improve local supply-demand balancing, reduce voltage deviations, and improve social welfare. However, the feasibility of such an approach is highly dependent on the regulatory framework and implementation requires investment in an adequate information and communication infrastructure. This paper examines components for the implementation of LES within energy communities in the EU, with a focus on price-forming methods that can be integrated into a net-billing system and adopted for different regulatory set-ups. Further, a method for the assessment of impacts on market participants is provided. The approach is applied for the assessment of the opportunities for LES in the city of Križevci, considering local generation, flexibility options, and real-life regulatory requirements. It is shown that LES under appropriate regulatory provisions can be an effective market-based mechanism for stimulating local generation and flexibility activation, and that way support decarbonization and local self-sufficiency. All members can benefit from participating in the energy community, but the distribution of the benefits notably depends on the applied LES price-forming method. On the other hand, subject to regulatory setup, the trade-offs are reflected on reduced revenues for market participants that generate income based on transmission fees, taxes, and/or surcharges. • Components for local energy sharing (LES) implementation within energy communities. • Framework for feasibility evaluation of LES under different regulatory set-ups. • MILP LES market-clearing model with energy sharing compensation price method. • LES price-forming methods integrated into a net-billing system. • Simulation of LES as a market with a local energy sharing coordinator. [ABSTRACT FROM AUTHOR]

The concept of off-grid hybrid wind energy system is financially attractive and more reliable than stand-alone power systems since it is based on more than one electricity generation source. One of the most expensive components in a stand-alone wind-power system is the energy storage system as very often it is oversized to increase system autonomy. In this work, we consider a hybrid system which consists of wind turbines, photovoltaic panels, diesel generator and battery storage. One of the main challenges experienced by project managers is the sizing of components for different sites. This challenge is due to the variability of the renewable energy resource and the load demand for different sites. This paper introduces a sizing model that has been developed and implemented as a graphical user interface, which predicts the optimum configuration of a hybrid system. In particular, this paper focuses on seeking the optimal size of the batteries and the diesel generator usage. Both of these components are seen to be trade-offs from each other. The model simulates real time operation of the hybrid system, using the annual measured hourly wind speed and solar irradiation. The benefit of using time series approach is that it reflects a more realistic situation; here, the peaks and troughs of the renewable energy resource are a central part of the sizing model. Finally, load sensitivity and hybrid system performance analysis are demonstrated. [ABSTRACT FROM AUTHOR]

• A green hybrid system based on liquid air energy storage, Kalina, and wind farm. • A comprehensive and systematic evaluation of the proposed hybrid concept. • Applying the monte carlo method and genetic algorithm for the whole proposed system. • Achieving the optimum round trip efficiency and total cost rate of 44.7% and 476 $/hr. • Reaching a payback period of 5.5 years, reducing to half in the reference design. The liquid air energy storage is a cutting-edge technology that covers the geographical drawbacks of other utility-scale energy storage alternatives. The coupling the liquid air storage system with renewable energies and heat recovery units can compensate the grid unstability and lack of their round trip efficiency, respectively. In the present paper, an off-shore wind farm including different wind turbines is assessed from technical, availability, and economic viewpoints to be combined with a liquid air energy storage unit, expolits a Kalina cycle for waste heat recovery. First, a comprehensive energy, exergy, and economic analyses are conducted for the integrated system; then, a coupling of artificial neural network and multi-objective genetic algorithm optimization method are carried out to find the optimum design condition. The findings show that around 93 MWh of the generated power in the wind site during off-peak period can be utilized to charge the system. Then, in addition to power generation in the wind farm, the reference system generates 76.4 MWh of extra power and 585 tons of domestic hot water during peak hours for peak shaving. Based on the optimization results, the round trip efficiency and total cost rate are 44.7% and 476 $/hr, repectively. The result of economic analysis demonstrated that the Enercon E-126 EP4 is the most cost-effective wind turbine for the proposed system, resulting in a period of 5.5 years. It has been also resulted that the existence of the LAES-KC system can half the paybacks. [Display omitted] [ABSTRACT FROM AUTHOR]

Photovoltaic and wind power generations are currently seen as sustainable options of in rural electrification, particularly in standalone applications. However the variable character of solar and wind resources as well as the variable load demand prevent these generation systems from being totally reliable without suitable energy storage system. Several research works have been conducted on the use of photovoltaic and wind systems in rural electrification; however most of these works have not considered other ways of storing energy except for conventional battery storage systems. In this paper, an energy dispatch model that satisfies the load demand, taking into account the intermittent nature of the solar and wind energy sources and variations in demand, is presented for a hybrid system consisting of a photovoltaic unit, a wind unit, a pumped hydro storage system and a diesel generator. The main purpose of the developed model is to minimize the hybrid system’s operation cost while optimizing the system’s power flow considering the different component’s operational constraints. The simulations have been performed using “fmincon” implemented in Matlab. The model have been applied to two test examples; the simulation results are analyzed and compared to the case where the diesel generator is used alone to supply the given load demand. The results show that using the developed control model for the proposed hybrid system, fuel saving can be achieved compared to the case where the diesel is used alone to supply the same load patters. [ABSTRACT FROM AUTHOR]

This paper presents a novel energy dispatching based on Model Predictive Control (MPC) for off-grid photovoltaic (PV)/wind turbine/hydrogen/battery hybrid systems. The renewable energy sources supply energy to the hybrid system and the battery and hydrogen system are used as energy storage devices. The denominated “hydrogen system” is composed of fuel cell, electrolyzer and hydrogen storage tank. The MPC generates the reference powers of the fuel cell and electrolyzer to satisfy different objectives: to track the load power demand and to keep the charge levels of the energy storage devices between their target margins. The modeling of the hybrid system was developed in MATLAB-Simulink, taking into account datasheets of commercially available components. To show the proper operation of the proposed energy dispatching, a simpler strategy based on state control was presented in order to compare and validate the results for long-term simulations of 25 years (expected lifetime of the system) with a sample time of one hour. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents two novel hourly energy supervisory controls (ESC) for improving long-term operation of off-grid hybrid systems (HS) integrating renewable energy sources (wind turbine and photovoltaic solar panels), hydrogen system (fuel cell, hydrogen tank and electrolyzer) and battery. The first ESC tries to improve the power supplied by the HS and the power stored in the battery and/or in the hydrogen tank, whereas the second one tries to minimize the number of needed elements (batteries, fuel cells and electrolyzers) throughout the expected life of the HS (25 years). Moreover, in both ESC, the battery state-of-charge (SOC) and the hydrogen tank level are controlled and maintained between optimum operating margins. Finally, a comparative study between the controls is carried out by models of the commercially available components used in the HS under study in this work. These ESC are also compared with a third ESC, already published by the authors, and based on reducing the utilization costs of the energy storage devices. The comparative study proves the right performance of the ESC and their differences. [Copyright &y& Elsevier]

• An optimal configuration model of multiport SSTs integrated AC/DC hybrid system is proposed. • A general multiport SST model is established for optimal planning of SST integrated system. • An optimal strategy of multiport SSTs in parallel operation is proposed. • A coordinate strategy of AC and DC cross-zone distributed energy storage is proposed. With the rapid growth in DC energy-using equipment and distributed DC power, traditional AC distribution networks increasingly have problems, such as high loss and poor flexibility. This paper studies an AC/DC hybrid system integrated with multiport solid-state transformers (SSTs) and distributed renewable energy and proposes an optimal configuration model for the AC/DC hybrid system based on a coordinate operation strategy of SSTs and energy storage. First, the composition and topology of the AC/DC hybrid system are proposed. Then, a realistic efficiency model of a multiport SST is established. Based on the minimum operating loss of the SST, a multiport SST dual-machine parallel optimal operation strategy is established. A multi-energy storage system collaborative optimization operation strategy is established based on the electricity price, grid-connected mode and synergistic relationship among each energy storage system. Finally, based on the proposed AC/DC hybrid system model, the optimization objective of the system life cycle net present cost (NPC), constraints and GA algorithm are set. The proposed method is verified by industrial scenarios. The simulation results show that the proposed model can improve the economic and efficiency of the SST integrated AC/DC hybrid system. [ABSTRACT FROM AUTHOR]