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Abstract: A Hybrid Energy System may been defined as a system in which different energy sources (solar, wind, hydro, diesel generator, etc.) as well as energy storage systems are interconnected to meet the load energy demand at any time. Given that the electrical contribution of energy each sources (taking individually) is dependent on the variation of the resources (sun, wind, water), and since the load energy requirement fluctuates, the main attribute of such hybrid system is to be able to generate energy at any time by optimally using each energy source, and storing excess energy for the later use in deficit generating conditions. The induced optimization problem is to compute the optimal size and operation control of the system with the aim of minimizing its initial, operation and maintenance as well as replacement costs while responding to the load energy requirements. In this paper our goal will be to propose an approach for optimal operation control of a hybrid multisource system with the aim of meeting the load energy requirement with reliability and minimized life cycle costs. The paper will be limited at the problem formulation and the development of the mathematical model for the performance of all the hybrid system's components. The proposed hybrid system model is based on a description of current flows from the different power sources, taking into account the losses and the impact of the operating decisions along the way up to the loads. The decision variables include the renewable energy sources sizes and number of modules as well as the operation control settings and strategies which lead to the determination the diesel generator and battery system output power. These developed model's decision variables can then be optimized using any suitable advanced algorithm in such a way to minimize the life-cycle costs subject while satisfying demand. [Copyright &y& Elsevier]

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]

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]