734 research outputs found

    Modeling and Utilizing a Vanadium Redox Flow Battery for Easier Grid and Market Integration of Wind Power

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    Power grid and market integration of wind energy is a challenge due to the fluctuating and intermittent power output resulting from the variable nature of wind resource. Energy storage is a promising alternative for effective grid integration of renewable energy. One storage technology which is under the spotlight in the recent years is the vanadium redox flow battery (VRFB) which could have certain advantages when utilized at large-scale grid connected applications. In this study, a megawatt scale VRFB was modeled based on experimental data with a kilowatt scale real life unit. The dependence of the overall system efficiency on the state of charge and power was determined. By using the model, optimal number of modules for certain power levels during charging and discharging operations were estimated for megawatt scale operations. In order to evaluate the power grid integration of wind power at a single wind farm level, a second simulation model which combines the megawatt scale VRFB model and a medium sized (10 MW) wind farm was developed and the battery was utilized to compensate for the deviations resulting from the forecast errors in an electricity market bidding structure. Using an existing electricity market model based on deviation penalties and penalty multipliers, economics of the system were evaluated by determining the payback periods for a dedicated VRFB installation at this medium sized, single wind farm level

    Stochastic Coordination of Joint Wind and Photovoltaic Systems with Energy Storage in Day-Ahead Market

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    This paper presents an optimal bid submission in a day-ahead electricity market for the problem of joint operation of wind with photovoltaic power systems having an energy storage device. Uncertainty not only due to the electricity market price, but also due to wind and photovoltaic powers is one of the main characteristics of this submission. The problem is formulated as a two-stage stochastic programming problem. The optimal bids and the energy flow in the batteries are the first-stage variables and the energy deviation is the second stage variable of the problem. Energy storage is a way to harness renewable energy conversion, allowing the store and discharge of energy at conveniently market prices. A case study with data from the Iberian day-ahead electricity market is presented and a comparison between joint and disjoint operations is discussed

    Integral approach to energy planning and electric grid assessment in a renewable energy technology integration for a 50/50 target applied to a small island

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    This paper presents an energy planning, a grid assessment, and an economic analysis, considering three growing scenarios (Low, Base and High) in the electricity consumption, to supply the energy demand for a hybrid power system (Photovoltaics/Wind/Diesel/Battery) on a small island by 2050. The main aim of this study is to present a methodology to optimize and reduce the backup time of the battery bank, included from the hybrid power generation system selected. Also, it will compare four di ff erent battery technologies, simultaneously, without changes in the renewable energy targets settled in 50% until 2050 and without changes in the safe continuous operation of the grid. The methodology includes a grid assessment analysis to obtain a reliable, strong and safe operation response based on the grid code parameters, even in case of disturbance. In the proposed methodology the analysis is developed on the basis of the use of two simulation model tools. The First simulation model tool determines the optimal values of variables that the system designer controls, such as the mix of components (Photovoltaics/Wind/Diesel/Battery) that make up the system and the size or quantity of each variable. This model uses the multiyear analysis based on a time-domain simulation run at the energy- fl ow level with discrete time-steps of 1 h. The Second simulation model tool assumes all the variables and parameters on the grid as constants during the period of the time analyzed. The power fl ow is analyzed through a programming language command script function and re fl ects the system response at a speci fi c time with given speci fi c variables and parameters. The fi nal technical proposal and its fi nancial analysis are obtained applying and validating this methodology on a small island, as well as, the selection of the system to be installed for the renewable electricity generation. The electric grid modi fi cations and reinforcements through the years until 2050, according to the grid code and the renewable energy targets settled for the island ’ s electric power system are included.Postprint (author's final draft

    Stochastic optimization for the daily joint operation of wind/PV and energy storage

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    This paper deals with the problem of optimal bidding in a day-ahead market of electricity for a power producer having joint operation of wind with photovoltaic power systems and storage of energy. Uncertainty, not only on electricity market prices, but also on wind and photovoltaic powers, has to be faced in order to achieve optimal bidding. The problem is viewed as a sort of a two-stage stochastic optimization problem formulated by mix-integer linear programming. A case study with data from the Iberian Peninsula is presented and a comparison between joint and disjoint operations is discussed, allowing concluding that the joint operation attenuates the economic impact of disjoint operation volatility

    An approach to implement PV Self-Consumption and Ramp-Rate Control Algorithm using a Day-to-Day Forecast battery charging, with a Vanadium Redox Flow Battery

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    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+storage to deal with the extreme power ramps at a domestic/services scale is not explored in the literature, neither its effective combination with other energy management strategies (EMSs). This work is focused on using a battery energy storage unit to control the power output of the PV system, maintaining the ramp rate (RR) within a non-violation limit and within a battery state of charge (SoC) range, appropriate to perform this RR management at the domestic/services scale. For this purpose, the authors explore the vanadium redox flow battery (VRFB) technology. Based on model simulation, key-performance indicators (KPI) are studied and improved, and finally, experimental validation is carried out. A comparison among three EMSs is made: a self-consumption maximization (SCM), a SCM with ramp-rate control (SCM+RR), and the last strategy performing also night battery charging based on the day ahead weather forecast (SCM+RR+WF). The weather forecast allowed the battery SoC control, preparing it to carry out the RR control the next day. The results show that SCM+RR+WF, especially in wintertime, is an excellent approach to manage PV+battery systems. This strategy successfully controlled 100 % of the violating power ramps, obtaining also a self-consumption ratio (SCR) of 59 %, and a grid-relief factor (GRF) of 61 %.Comment: Keywords: PV solar energy; energy storage; self-consumption; ramp rate; VRF

    Hybrid wind power balance control strategy using thermal power, hydro power and flow batteries

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    The increased number of renewable power plants pose threat to power system balance. Their intermittent nature makes it very difficult to predict power output, thus either additional reserve power plants or new storage and control technologies are required. Traditional spinning reserve cannot fully compensate sudden changes in renewable energy power generation. Using new storage technologies such as flow batteries, it is feasible to balance the variations in power and voltage within very short period of time. This paper summarises the controlled use of hybrid flow battery, thermal and hydro power plant system, to support wind power plants to reach near perfect balance, i.e. make the total power output as close as possible to the predicted value. It also investigates the possibility of such technology to take part in the balance of the Lithuanian power system. A dynamic model of flow battery is demonstrated where it evaluates the main parameters such as power, energy, reaction time and efficiency. The required battery size is tested based on range of thermal and hydro power plant reaction times. This work suggests that power and energy of a reasonable size flow battery is sufficient to correct the load and wind power imbalance
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