Implementation and control of a residential electrothermal microgrid based on renewable energies, a hybrid storage system and demand side management

This paper proposes an energy management strategy for a residential electrothermal microgrid, based on renewable energy sources. While grid connected, it makes use of a hybrid electrothermal storage system, formed by a battery and a hot water tank along with an electrical water heater as a controllable load, which make possible the energy management within the microgrid. The microgrid emulates the operation of a single family home with domestic hot water (DHW) consumption, a heating, ventilation and air conditioning (HVAC) system as well as the typical electric loads. An energy management strategy has been designed which optimizes the power exchanged with the grid profile in terms of peaks and fluctuations, in applications with high penetration levels of renewables. The proposed energy management strategy has been evaluated and validated experimentally in a full scale residential microgrid built in our Renewable Energy Laboratory, by means of continuous operation under real conditions. The results show that the combination of electric and thermal storage systems with controllable loads is a promising technology that could maximize the penetration level of renewable energies in the electric system.This work was partially funded by the Government of Navarra and the FEDER funds under project “Microgrids in Navarra: design, development and implementation” and by the Spanish Ministry of Economy and Competitiveness under grant DPI2010-21671-C02-01, as well as by the European Union under the project FP7-308468, “PVCROPS-Photovoltaic Cost reduction, reliability, operational performance, prediction and simulation”

Development of energy management strategies for the sizing of a fast charging station for electric buses

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

Influence of the aging model of lithium-ion batteries on the management of PV self-consumption systems

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)

On the requirements of the power converter for second-life lithium-ion batteries

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