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Hybrid energy storage systems (HESS) combine different energy storage technologies aiming at overall system performance and lifetime improvement compared to a single technology system. In this work, control combinations for a vanadium redox flow battery (VRFB, 5/60 kW/kWh) and a lithium-ion battery (LIB, 3.3/9.8 kW/kWh) are investigated for the design of a HESS. Four real-time energy management/power allocation scenarios are considered for the operation of the hybrid storage solution through a 15-year economic and energetic analysis. The results obtained for each scenario are compared with a single technology battery performance. In the definition of the scenarios, real electricity generation is considered from two solar photovoltaic installations (3.2 kWp and 6.7 kWp) and an estimated representative load of a services building. HESS performance is evaluated through specific energy and economic key performance indicators. The results obtained indicate that the use of customized energy management strategies (EMSs) renders the VRFB and LIB characteristics complementary, besides enhancing the competitiveness of VRFB, as a single technology. Moreover, the HESS management impacts the seasonality factor, contributing to the overall electric system smart management., Comment: 19 pages, 7 figures, research paper

The variability of the solar resource is mainly caused by cloud passing, causing rapid power fluctuations on the output of photovoltaic (PV) systems. The fluctuations can negatively impact the electric grid, and smoothing techniques can be used as attempts to correct it. However, the integration of a PV+VRFB to deal with the extreme power ramps at a building scale is underexplored in the literature, as well as its effectiveness in combination with other energy management strategies (EMSs). This work is focused on using a VRFB to control the power output of the PV installation, maintaining the ramp rate within a non-violation limit and within a battery state of charge (SOC) range, appropriate to perform the ramp rate management. Based on the model simulation, energy key-performance indicators (KPI) are studied, and validation in real-time is carried. Three EMSs are simulated: a self-consumption maximization (SCM), and SCM with ramp rate control (SCM+RR), and this last strategy includes a night battery charging based on a day ahead weather forecast (SCM+RR+WF). Results show a battery SOC management control is essential to apply these EMSs on VRFB, and the online weather forecast proves to be efficient in real-time application. SCM+RR+WF is a robust approach to manage PV+VRFB systems in wintertime (studied application), and high PV penetration building areas make it a feasible approach. Over the studied week, the strategy successfully controlled 100% of the violating power ramps, also obtaining a self-consumption ratio (SCR) of 59% and a grid-relief factor (GRF) of 61%., Comment: Keywords: Photovoltaic solar energy; energy storage; self-consumption; ramp rate; VRFB; energy management strategies

In the residential sector, energy micro-generation and its intelligent management have been creating novel energy market models, considering new concepts of energy use and distribution, in which the prosumer has an active role in the energy generation and its self-consumption. The configuration of the solar photovoltaic system with a battery energy storage in Portugal is unclear in the technical, energetic and mostly in the economical point of view. The energy generation and consumption management, jointly with the battery operation, have a great influence in the profitability value of the configuration. The present work evaluates different photovoltaic configurations with and without energy storage for the normal low voltage C consumer profile, for a contracted power of 3.45 kVA, to evaluate the cost-effectiveness of the systems, framed in the regulation in force in Portugal, the decree-law 153/2014, which promotes the micro-generation and self-consumption. The analysis consists of three different geographical locations in the country, considering distinct electric tariffs. These are relevant parameters in the choice of the configuration, concluding that although the solar photovoltaic system by itself is already economical presently, its integration with battery energy storage is not in most of the configurations, however it is already possible to find profitable PV and battery configurations, considering all the most relevant criteria, and supported by good energy management., Comment: 39 pages (including list of figures, tables and appendices), 18 figures, Research paper