Suchergebnisse

This paper reports on the modelling of a commercial 1.2 kW proton exchange membrane fuel cell (PEMFC), based on interrelated electrical and thermal models. The electrical model proposed is based on the integration of the thermodynamic and electrochemical phenomena taking place in the FC whilst the thermal model is established from the FC thermal energy balance. The combination of both models makes it possible to predict the FC voltage, based on the current demanded and the ambient temperature. Furthermore, an experimental characterization is conducted and the parameters for the models associated with the FC electrical and thermal performance are obtained. The models are implemented in Matlab Simulink and validated in a number of operating environments, for steady-state and dynamic modes alike. In turn, the FC models are validated in an actual microgrid operating environment, through the series connection of 4 PEMFC. The simulations of the models precisely and accurately reproduce the FC electrical and thermal performance. ; The authors acknowledge the Spanish Ministry of Economy and Competitiveness under grant DPI2010-21671-C02-01 and the Government of Navarre and FEDER funds under project "Microgrids in Navarra: design and implementation".

The growing interest in e-mobility and the increasing installation of renewable energy-based systems are leading to rapid improvements in lithium-ion batteries. In this context, battery manufacturers and engineers require advanced models in order to study battery performance accurately. A number of Li-ion battery models are based on the representation of physical phenomena by electrochemical equations. Although providing detailed physics-based information, these models cannot take into account all the phenomena for a whole battery, given the high complexity of the equations. Other models are based on equivalent circuits and are easier to design and use. However, they fail to relate these circuit parameters to physical properties. In order to take the best of both modeling techniques, we propose an equivalent circuit model which keeps a straight correlation between its parameters and the battery electrochemical principles. Consequently, this model has the required simplicity to be used in the simulation of a whole battery, while providing the depth of detail needed to identify physical phenomena. Moreover, due to its high accuracy, it can be used in a wide range of environments, as shown in the experimental validations carried out in the final section of this paper. ; The authors acknowledge the support of the Spanish State Research Agency (AEI) and FEDER UE under grants DPI2013 42853 R, DPI2016 80641 R and DPI2016 80642 R; of Government of Navarra through research project PI038 INTEGRA-RENOVABLES; and the FPU Program of the Spanish Ministry of Education, Culture and Sport (FPU13/00542).

Over the coming years, major growth in the use of Li-ion batteries is expected, both in electric mobility as well as in stationary applications, be it in self-consumption systems and micro grids or in large renewable power generation plants. The proper characterization of lithium-ion cells is of vital importance for the development of precise models that permit the simulation and prediction of their behavior, so as to suitably configure cell groupings for the resulting battery packs, and to properly select the most suitable cells from the extensive manufacturer offer. In this work, an analysis is conducted of the main techniques used in the literature to characterize batteries. Also, an experimental comparative is carried out on 18650 Liion cells from three large global manufacturers, focusing on the primary methodologies used to characterize capacity, internal resistance and open circuit voltage. Finally, the advantages and disadvantages are presented for the methodologies used, based on the experimental results obtained. ; The authors would like to acknowledge the support of the Spanish State Research Agency (AEI) and FEDER-UE under grants DPI2016-80641-R and DPI2016-80642-R and of Government of Navarra through research projects PI020 RENEWABLE-STORAGE and 0011-1411-2018-000029 GERA.

This contribution analyses lifetime estimation errors due to the effect of power fluctuations in lithium-ion batteries connected to microgrids when different time steps are used for the calculations. Usually, not every second data are available or the computational cost is excessively high. Those facts result in the use of larger time steps. However, the increase of the time steps may turn out in too optimistic predictions. Data from a real microgrid make it possible to optimize calculation times while keeping low errors. The results show that when 1 minute time step is set, the computation time is reduced by 14.4 times while the lifetime overstatement is only 3.5-5.2% higher, depending on the aging model. ; The authors would like to acknowledge the support of the Spanish State Research Agency (AEI) and FEDER--UE under grants DPI2016-80641-R and DPI2016-80642-R and of Government of Navarra through research projects PI020 RENEWABLE-STORAGE and 0011-1411-2018-000029 GERA.

The unpredictable nature of renewable energies is drawing attention to lithium-ion batteries. In order to make full utilization of these batteries, some research works are focused on the management of existing systems, while others propose sizing techniques based on business models. However, in order to optimise the global system, a comprehensive methodology that considers both battery sizing and management at the same time is needed. This paper proposes a new optimisation algorithm based on a combination of dynamic programming and a region elimination technique that makes it possible to address both problems at the same time. This is of great interest, since the optimal size of the storage system depends on the management strategy and, in turn, the design of this strategy needs to take account of the battery size. The method is applied to a real installation consisting of a 100 kWp rooftop photovoltaic plant and a Li-ion battery system connected to a grid with variable electricity price. Results show that, unlike conventional optimisation methods, the proposed algorithm reaches an optimised energy dispatch plan that leads to a higher net present value. Finally, the tool is used to provide a sensitivity analysis that identifies key informative variables for decision makers ; The authors would like to acknowledge the support of the Spanish State Research Agency and FEDER-UE under grants DPI2016-80641-R and DPI2016-80642-R; of Government of Navarra through research project PI038 INTEGRA-RENOVABLES; and the FPU Program of the Spanish Ministry of Education, Culture and Sport (FPU13/00542).

Nowadays, electric vehicle batteries reutilization is considered such as a feasible alternative to recycling, as it allows to benefit from their remaining energy and to enlarge their lifetime. Stationary applications as self-consumption or isolated systems support are examples of possible second life uses for these batteries. However, the modules that compose these batteries have very heterogeneous properties, and therefore condition their performance. This paper aims to characterize and analyze the existing capacity dispersion of Nissan Leaf modules that have reached the end of their lifetime on their original application and of new modules of this Electric Vehicle, in order to establish a comparison between them. ; The authors would like to acknowledge the support of the Spanish State Research Agency (AEI) and FEDER-UE under grants DPI2016-80641-R and DPI2016-80642-R and of Government of Navarra through research projects PI020 RENEWABLE STORAGE and 0011-1411-2018-000029 GERA.

Energy storage systems are playing an increasingly important role in a variety of applications, such as electric vehicles or grid-connected systems. In this context, supercapacitors (SCs) are gaining ground due to their high power density, good performance and long maintenance-free lifetime. For this reason, SCs are a hot research topic, and several papers are being published on material engineering, performance characterization, modelling and post-mortem analysis. A compilation of the most important millstones on this topic is essential to keep researchers on related fields updated about new potentials of this technology. This review paper covers recent research aspects and applications of SCs, highlighting the relationship between material properties and electrical characteristics. It begins with an explanation of the energy storage mechanisms and materials used by SCs. Based on these materials, the SCs are classified, their key features are summarised, and their electrochemical characteristics are related to electrical performance. Given the high interest in system modelling and the large number of papers published on this topic, modelling techniques are classified, explained and compared, addressing their strengths and weaknesses, and the experimental techniques used to measure the modelled properties are described. Finally, the market sectors in which SCs are successfully used, as well as their growth expectations are analysed. The analysis presented herein gives account of the expansion that SC market is currently undergoing and identifies the most promising research trends on this field. ; This work was supported in part by the Spanish State Research Agency (AEI) and FEDER UE under Grant DPI2016-80641-R and Grant DPI2016-80642-R, in part by the Government of Navarre through the Research Project PI020 RENEWABLE-STORAGE, and in part by the FPU Program of the Spanish Ministry of Education, Culture and Sport under Grant FPU13 /00542.

The electric vehicle contributes to reduce greenhouse gases emissions and get a greater integration of renewable energy. In this context, the implementation of urban buses implies the development of new grid infrastructures in order to carry out the electricity supply required by the charging stations. In order to optimize the size of these infrastructures and to have more power capacity, this contribution proposes the design and the sizing of a fast charging station with a stationary energy storage system (ESS) installed, to supply the energy of the buses that run on one of the lines of Pamplona (Spain). In this contribution, first, the power demanded by the charging point is measured at the fast charging station located at the Public University of Navarre. Second, three energy management strategies are developed with which to use ESS. Finally, the proposed energy management strategies are simulated with the measured data obtained. The results achieved in this contribution show that with a 40 kWh ESS, the power demanded from the grid can be reduced by a whole 70%, that is, from 250 kW to 74 kW. In addition, the power contracted in the electricity rate is reduced too. ; The authors would like to acknowledge the support of the European Union under the H2020 project STARDUST (774094), the Spanish State Research Agency (AEI) and FEDER-UE under grants DPI2016-80641-R, DPI2016-80642-R, PID2019-111262RB-I00 and PID2019-110956RB-I00, the Government of Navarra through research project 0011-1411-2018-000029 GERA and the Public University of Navarre under project ReBMS PJUPNA1904.

Nowadays, the reuse of electric vehicle batteries is considered to be a feasible alternative to recycling, as it allows them to benefit from their remaining energy capacity and to enlarge their lifetime. Stationary applications, such as self-consumption or off-grid systems support, are examples of second-life (SL) uses for retired batteries. However, reused modules that compose these batteries have heterogeneous properties, which limit their performance. This article aims to assess the influence of degradation in modules from electric vehicles, covering three main aspects: performance, capacity dispersion, and extended SL behavior. First, a complete characterization of new and reused modules is carried out, considering three temperatures and three discharge rates. In the second stage, intra- and intermodule capacity dispersions are evaluated with new and reused samples. Finally, the behavior during SL is also analyzed, through an accelerated cycling test so that the evolution of capacity and dispersion are assessed. Experimental results show that the performance of reused modules is especially undermined at low temperatures and high current rates, as well as in advanced stages of aging. The intramodule dispersion is found to be similar in reused and new samples, while the intermodule differences are nearly four times greater in SL. ; This work was supported in part by the Spanish State Research Agency (AEI) under Grant PID2019-111262RB-I00/AEI/10.13039/501100011033 and Grant DPI2016-80641-R, in part by the European Union under the H2020 Project STARDUST under Grant 774094, in part by the Government of Navarra under Research Project 0011-1411-2018-000029 GERA, and in part by the Public University of Navarre under Project ReBMS PJUPNA1904.

The use of lithium-ion batteries is increasing year after year, especially in the automotive sector. Given the high requirements of electric vehicles, their energy storage systems are discarded when they still have around 70% of its initial capacity. These discarded batteries are being studied as a low-price option for stationary systems, mostly related to renewable energy generation, with lower battery requirements. However, the increasing dispersion of cell capacity detailed in this contribution limits the use of second-life cells if regular battery management systems and power converters. We present in this contribution an experimental comparison of the capacity dispersion between fresh and second-life cells, and detail the relationship between the capacity dispersion and the required BMS functionality. Furthermore, we include the ageing phenomena in the analysis by means of experimental ageing results, given that the capacity dispersion is enlarged as the battery ages. After this, we use this data to quantify advantages and disadvantages of a combined BMS and power converter, based on a multilevel topology, compared to a conventional BMS. The most relevant result, when a 55-cell battery is analysed, is a 65% increase in capacity during its whole second life if the BMS and power converter are combined by means of a multilevel topology. The increased level of complexity required by the combined BMS-power converter architecture is analysed in this contribution, providing a convenient tool for the selection of the most suitable option for each application. ; The authors would like to acknowledge the support of the Spanish State Research Agency (AEI) and FEDER–UE under grants DPI2016-80641-R and DPI2016-80642-R and of Government of Navarra through research projects PI020 RENEWABLE-STORAGE and 0011-1411-2018-000029 GERA.

Lithium-ion batteries are gaining importance for a variety of applications due to their improving characteristics and decreasing price. An accurate knowledge of their aging is required for a successful use of these ESSs. The vast number of models that has been proposed to predict these phenomena raise doubts about the suitability of a model for a particular battery application. The performance of three models published for a Sanyo 18650 cylindrical cell in a self-consumption system are compared in this work. Measured photovoltaic production and home consumption with a sampling frequency of 15 minutes are used for this comparison. The different aging predictions calculated by these three models are analyzed, compared and discussed. These comparison is particularized for two management strategies. The first of them maximizes the self-consumption PV energy, while the second reduces the maximum power peak demanded from the grid. ; The authors would like to acknowledge the support of the Spanish State Research Agency (AEI) and FEDER-UE under grants DPI2013-42853-R, DPI2016-80641-R and DPI2016-80642-R; of Government of Navarra through research project PI038 INTEGRA-RENOVABLES; and the FPU Program of the Spanish Ministry of Education, Culture and Sport (FPU13/00542).

Lithium-ion batteries are gaining importance for a variety of applications due to their price decrease and characteristics improvement. For a proper use of such storage systems, an energy management algorithm (EMA) is required. A number of EMAs, with various characteristics, have been published recently, given the diverse nature of battery problems. The EMA of deterministic battery problems is usually based on an optimization algorithm. The selection of such an algorithm depends on a few problem characteristics, which need to be identified and closely analyzed. The aim of this article is to identify the critical optimization problem parameters that determine the most suitable EMA for a Li-ion battery. With this purpose, the starting point is a detailed model of a Li-ion battery. Three EMAs based on the algorithms used to face deterministic problems, namely dynamic, linear, and quadratic programming, are designed to optimize the energy dispatch of such a battery. Using real irradiation and power price data, the results of these EMAs are compared for various case studies. Given that none of the EMAs achieves the best results for all analyzed cases, the problem parameters that determine the most suitable algorithm are identified to be four, i.e., desired computation intensity, characteristics of the battery aging model, battery energy and power capabilities, and the number of optimization variables, which are determined by the number of energy storage systems, the length of the optimization problem, and the desired time step. ; This work was supported in part by the European Union under the H2020 Project STARDUST under Grant 774094, in part by the Spanish State Research Agency and FEDER-UE under Grants DPI2016-80641-R, DPI2016-80642-R, PID2019-111262RB-I00, and PID2019-110956RB-I00, in part by the Government of Navarra through Research Project 0011-1411-2018-000029 GERA, and in part by the Public University of Navarre under Project ReBMS PJUPNA1904.

Lithium-ion batteries are gaining importance for a variety of applications due to their price decrease and characteristics improvement. A good energy management strategy is required in order to increase the profitability of an energy system using a Li-ion battery for storage. The vast number of management algorithms that has been proposed to optimize the achieved profit, with diverse computational power requirements and using models with different complexity, raise doubts about the suitability of an algorithm and the required computation power for a particular application. The performance of three energy management algorithms based on linear, quadratic, and dynamic programming are compared in this work. A realistic scenario of a medium-sized PV plant with a constraint of peak shaving is used for this comparison. The results achieved by the three algorithms are compared and the grounds of the differences are analyzed. Among the three compared algorithms, the quadratic one seems to be the most suitable for renewableenergy applications, given the undue simplification of the battery aging required by the linear algorithm and the discretization and computational power required by a dynamic algorithm. ; The authors would like to acknowledge the support of the Spanish State Research Agency (AEI) and FEDER–UE under grants DPI2016-80641-R and DPI2016-80642-R and of Government of Navarra through research projects PI020 RENEWABLE-STORAGE and 0011-1411-2018-000029 GERA.