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".
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 Permanent Magnet Synchronous Generator (PMSG) with diode bridge is frequently used in small Wind Energy Conversion Systems (WECS). This configuration is robust and cheap, and therefore suitable for small WECS. In order to achieve Maximum Power Point Tracking (MPPT) with no mechanical sensors, it is possible to impose the relationship between the DC voltage and the DC current on the optimum operating points. However, this relationship is difficult to calculate theoretically since the whole system is involved. In fact, as there is no model of the whole system in the literature, the optimum curve IL*(Vdc) is obtained with experimental tests or simulations. This paper develops an accurate model of the whole WECS, thereby making it possible to relate the electrical variables to the mechanical ones. With this model, it is possible to calculate the optimum curve IL*(Vdc) from commonly-known system parameters and to control the system from the DC side. Experimental results validate the theoretical analysis and show that maximum power is extracted for actual wind speed profiles. ; This work was partially funded by the Spanish Ministry of Economy and Competitiveness under Grants DPI2009-14713-C03- 01 and DPI2010-21671-C02-01, by the Government of Navarra and the FEDER funds under project "Microgrids in Navarra: design and implementation" and by the Public University of Navarra.
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).
The Public University of Navarre joined with Navarre Government has created the Women, Science and Technology Chair. This chair arises due to the plummeting tendency of the percentage of women in STEM degrees with the aim of reversing this trend. The programme of activities is defined throughout this contribution by six activities: a Theatre Play, a Poster Award on Final Degree/Masters Project, The 1st Week of Women, Science and Technology, the Promotion of Technical Degrees in schools and high-schools, a Workshop about Gender Stereotypes and the Fostering of Women among Science and Environment. Each activity gained great success and the preset goals were highly accomplished, especially, the 1st Week of Women, Science and Technology activity. The latter achieved a great success both in participation and in repercussion, contributing to visualize the role of women in science and technology. ; Authors are grateful to Navarre Government, Caja Navarra Foundation, Spanish Foundation for Science and Technology (FECYT-Ministerio de Economía, Industria y Competitividad), Public University of Navarre, IEEE CAS Spain Chapter and the Chair in Renewable Energy of the Public University of Navarre.
[Aim]To analyse the biogeographic patterns of Temperate Deciduous Forests (TDFs) in Western Eurasia based on different life-forms and forests layers and explore their relationships with the current climate, Last Glacial Maximum (LGM) climate and topography. ; [Location] Western Eurasia. ; [Methods] We delimited nine regions encompassing the variability of TDFs in Western Eurasia and collected 1000 vegetation plots from each. We deconstructed the plant communities into three layers, tree, shrub and floor. We used (i) generalized linear mixed models (GLMM) to analyse the influence of current climate, historical climate and topography on species richness by accounting for regional effects and (ii) redundancy analysis (RDA) with variance partitioning to describe the variation in life forms along abiotic gradients. The three forest layers were analysed jointly and separately. ; [Results] The Balkans, Alps and Carpathians appeared to be the richest in plant species, whereas the British Isles and the Hyrcanian region were the poorest. Annual temperature range and annual mean temperature were the best predictors of species richness for the whole dataset and for the shrub layer. The tree layer richness was mainly explained by the annual temperature range and by elevation, whereas the forest floor richness was more related to the annual temperature range and the annual mean temperature differences between the LGM and current climate. The current climate was the main predictor of the composition of the whole community, the tree layer and the floor layer, while the shrub layer was also influenced by historical climate. ; [Main conclusions] Our overview of the diversity of temperate deciduous forests in Western Eurasia demonstrates different patterns and drivers across life-forms and forest layers. While the diversity of trees is mainly linked to current climatic conditions, the shrub layer is also driven by postglacial-glacial climatic stability, suggesting a different origin from forest trees. ; The authors are indebted to the custodians of the EVA databases for providing the vegetation-plot data, and to all the scientists who sampled these plots. MC, IK, PN and CM were funded by grant no. 19-28491X of the Czech Science Foundation and JL, IB, JAC and CM by grant no. IT936-16 of the Basque Government. The data used for this survey have been extracted with the permission of the EVA (European Vegetation Archive) and the Hyrcanian Forest Vegetation Database. ; Peer reviewed