Estimation of electric vehicle battery capacity requirements based on synthetic cycles

The adoption of the Electric Vehicle requires a switch towards a circular system to reduce their environmental impact. Under this framework, the correct sizing of the batteries and avoiding their underuse are key actions. Based on the analysis of real data, this work proposes a model to synthesize current profiles representative of trips containing urban and highway sections. The model is used to generate cycles for common daily driving distances. Different sized batteries are analysed at their beginning and end of life to evaluate their ability to provide the required range. Based on the results, it is suggested that the ongoing trend of battery capacity increase is not justified. The commonly assumed threshold of 70–80% State of Health has proved to be too conservative in most cases, allowing for an extension of the first life that should be individually defined based on functional aspects.Peer ReviewedPostprint (published version

Redefining the EV battery end of life: internal resistance related limitations

Currently Electric Vehicle batteries are considered to reach the End of Lifeonce their State of Health reaches70-80%. However, notions of circular economy suggest that the battery first-life should be extended as much as possible to reduce their environmental impact.Previous works have considered the range limitations of the drivers, arguing that the End of Lifethreshold is too conservative for many cases. However, to validate this statement, the increase of the internal resistance must be addressed. In this work a battery model is used to simulate the battery performance under different driving cycles synthesized from real data. Results show that the functional End of Life is forced by capacity, power or safety related issues.The dominant cause for reaching the End of Life depends highly on the battery size.The under performance is in most cases found after 70-80% State of Health, validating that the first life of most batteries could be extended without affecting the performance of the vehicle.This work was supported by the ALBATROSS H2020 project with grant agreement ID 963580. Cristina Corchero and Lluc Canals Casals are Serra Hunter Fellows.Peer ReviewedPostprint (published version

Integration of a microgrid laboratory into an aggregation platform and analysis of the potential for flexibility

The increase of Renewable Energy Sources (RES) has given momentum to demand-side flexibility, led by Demand Response (DR), to counteract the uncertainties of the new electricity system. Meanwhile, consumers, with the help of Demand Aggregators (DA), are becoming active participants by engaging in flexibility actions. As a tool for the experimental assessment of DR, this work integrates a microgrid laboratory with an aggregation platform. To test the environment created and analyse the impact of DR, two consumers have been defined using virtual, emulated and real elements: a residential user with a Heating Ventilation and Air Conditioning (HVAC) unit and a prosumer equipped with Photovoltaic (PV) panels and a second-life battery.Postprint (published version

Circular economy-based alternatives beyond second-life applications: maximizing the electric vehicle battery first life

Electric vehicle battery second-life applications are gaining attention as a way to minimize the environmental impact and increase economic profits. However, the demand for stationary energy storage is expected to be saturated in the near future with these second-life batteries. This fact, in addition to the several technical and economic challenges of second-life batteries, promotes exploring other alternatives. This work analyses and compares these possible approaches in terms of battery degradation and economic profit. The results show that for large batteries, intensive Vehicle to Grid does not cause an early retirement of the battery and allows reducing the underuse of the battery. In addition, for the same battery size, Vehicle to Grid provides more economic profit than second-life applications. Nevertheless, only in a few cases does this appear to be more profitable than simply utilizing the battery for driving. Importantly, this study has shown how the assessment of the second-life tends to be too optimistic as a consequence of assuming a fixed End of Life threshold for the batteries.This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 963580. This funding includes funds to support research work and open-access publications.Peer ReviewedPostprint (published version

Are electric vehicle batteries being underused? A review of current practices and sources of circularity

The increasing demand for Lithium-ion batteries for Electric Vehicle calls for the adoption of sustainable practices and a switch towards a circular economy-based system to ensure that the electrification of transportation does not come at a high environmental cost. While driving patterns have not changed much over the years, the current Electric Vehicle market is evolving towards models with higher battery capacities. In addition, these batteries are considered to reach the End of Life at 70–80% State of Health, regardless of their capacity and application requirements. These issues may cause an underuse of the batteries and, therefore, hinder the sustainability of the Electric Vehicle. The goal of this study is to review and compare the circular processes available around Electric Vehicle batteries. The review highlights the importance of prioritizing the first-life of the battery onboard, starting with reducing the nominal capacity of the models. In cases where the battery is in risk of reaching the End of Life with additional value, Vehicle to Grid is encouraged over the deployment of second-life applications, which are being strongly promoted through institutional fundings in Europe. As a result of the identified research gaps, the methodological framework for the estimation of a functional End of Life is proposed, which constitutes a valuable tool for sustainable decision-making and allows to identify a more accurate End of Life, rather than considering the fixed threshold assumed in the literature.This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 963580. This funding includes funds to support research work and openaccess publications.Peer ReviewedPostprint (published version

Electric vehicle battery health expected at end of life in the upcoming years based on UK data

Second-life businesses from Electric Vehicle (EV) batteries are gaining attention considering that these batteries are deemed as inappropriate for transport purposes once they reach 80 or 70% of State of Health (SoH). However, the limited number of retired batteries and the trend in battery capacity increase hinder a realistic evaluation of second-life applications. To analyze battery reuse, a closer look at the End of Life (EoL) conditions of these batteries must be taken. This study presents a battery ageing model to estimate the SoH of EV batteries according to their age and mileage. The model is applied to the current retirement characteristics of combustion vehicles to statistically determine the expected SoH at the vehicle EoL. Results indicate that most EVs will reach EoL for reasons other than under-performance. Once retired, most EV batteries will have a SoH higher than 75% within the next 20 years, opening an interesting market for second-life businesses. However, battery reuse is an option that, considering the growing EV market, will rapidly saturate the stationary energy storage demand. Before 2040, most EV batteries will follow streams towards the circular economy, although at some point, they will have to be sent directly to recycling after the vehicular use.Peer ReviewedObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.2 - Per a 2030, proporcionar accés a sistemes de transport segurs, assequibles, accessi­bles i sostenibles per a totes les persones, i millorar la seguretat viària, en particular mitjan­çant l’ampliació del transport públic, amb especial atenció a les necessitats de les persones en situació vulnerable, dones, nenes, nens, persones amb discapacitat i persones gransObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesPostprint (published version

Procedure for Assessing the Suitability of Battery Second Life Applications after EV First Life

Using batteries after their first life in an Electric Vehicle (EV) represents an opportunity to reduce the environmental impact and increase the economic benefits before recycling the battery. Many different second life applications have been proposed, each with multiple criteria that have to be taken into consideration when deciding the most suitable course of action. In this article, a battery assessment procedure is proposed that consolidates and expands upon the approaches in the literature, and facilitates the decision-making process for a battery after it has reached the end of its first life. The procedure is composed of three stages, including an evaluation of the state of the battery, an evaluation of the technical viability and an economic evaluation. Options for battery configurations are explored (pack direct use, stack of battery packs, module direct use, pack refurbish with modules, pack refurbish with cells). By comparing these configurations with the technical requirements for second life applications, a reader can rapidly understand the tradeoffs and practical strategies for how best to implement second life batteries for their specific application. Lastly, an economic evaluation process is developed to determine the cost of implementing various second life battery configurations and the revenue for different end use applications. An example of the battery assessment procedure is included to demonstrate how it could be carried out.This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 963540 and No. 963580. This funding includes funds to support research work and open-access publications.Peer ReviewedPostprint (published version

Integration of a microgrid laboratory into an aggregation platform and analysis of the potential for flexibility

Due to the increase of renewable energy sources in the electricity grid, demand-side flexibility, lead by Demand Response (DR), is gaining momentum to counteract the uncertainties of the new electricity system and contribute to grid balancing. At the same time, consumers are becoming active participants by engaging in flexibility actions enabled by demand aggregators. This project aims to integrate a microgrid laboratory with an aggregation platform in order to set up and configure the necessary tools to operate the laboratory as a platform to test flexibility. This way, the potential flexibility services that consumers can provide to the grid has been analysed. With the use of virtual, real and emulated elements from the laboratory, a more realistic impact and value of DR programs can be quantified. Two types of consumers have been defined: a residential one (Scenario 1), with a Heating Ventilation and Air Conditioning (HVAC) unit and a prosumer (Scenario 2), owning a battery in a solar Photovoltaic (PV) selfconsumption system. For both scenarios, the effect of receiving flexibility activations from the aggregator has been analysed and compared with a base case in which no interaction with the aggregator occurs. In addition, OpenADR, a relevant protocol for DR has been implemented and tested in the laboratory (Scenario 3). The experimental work developed shows that demand-side flexibility can play a big role in the current and future electricity grid, as customers, demand aggregators and grid operators can benefit from these actions. From an operational point of view, the tests in the laboratory showed that the HVAC and the battery were able to follow the activations received, as long as the commands were properly calculated by the aggregator. For the Scenario 1, the aggregator modified the temperature setpoint of the HVAC, causing a shift of the consumption to different time periods. In the Scenario 2, the battery charge/discharge power setpoint was modified by the aggregator in order to reduce the electricity consumption from the grid or inject power into it when necessary. From the customer’s perspective, we saw that the DR actions can increase the energy cost in some cases, highlighting the importance of economic incentives to attract customer engagement. In addition, in the Scenario 1, involving the HVAC system, the thermal comfort of the users was not affected by the presence of the aggregator, as the indoor temperatures were maintained in an adequate range. Finally, allowing the aggregator to control the battery in Scenario 2 did not have any effect on the self consumption factor of the user. Regarding OpenADR, a test was developed first virtually and then between the laboratory and the aggregator in Scenario 3. OpenADR proved to be a reliable and useful protocol that has the potential to be used in DR applications due to the different use cases it can coverObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.1 - Per a 2030, garantir l’accés universal a serveis d’energia assequibles, confiables i modern

Integration of a microgrid laboratory into an aggregation platform and analysis of the potential for flexibility

Due to the increase of renewable energy sources in the electricity grid, demand-side flexibility, lead by Demand Response (DR), is gaining momentum to counteract the uncertainties of the new electricity system and contribute to grid balancing. At the same time, consumers are becoming active participants by engaging in flexibility actions enabled by demand aggregators. This project aims to integrate a microgrid laboratory with an aggregation platform in order to set up and configure the necessary tools to operate the laboratory as a platform to test flexibility. This way, the potential flexibility services that consumers can provide to the grid has been analysed. With the use of virtual, real and emulated elements from the laboratory, a more realistic impact and value of DR programs can be quantified. Two types of consumers have been defined: a residential one (Scenario 1), with a Heating Ventilation and Air Conditioning (HVAC) unit and a prosumer (Scenario 2), owning a battery in a solar Photovoltaic (PV) selfconsumption system. For both scenarios, the effect of receiving flexibility activations from the aggregator has been analysed and compared with a base case in which no interaction with the aggregator occurs. In addition, OpenADR, a relevant protocol for DR has been implemented and tested in the laboratory (Scenario 3). The experimental work developed shows that demand-side flexibility can play a big role in the current and future electricity grid, as customers, demand aggregators and grid operators can benefit from these actions. From an operational point of view, the tests in the laboratory showed that the HVAC and the battery were able to follow the activations received, as long as the commands were properly calculated by the aggregator. For the Scenario 1, the aggregator modified the temperature setpoint of the HVAC, causing a shift of the consumption to different time periods. In the Scenario 2, the battery charge/discharge power setpoint was modified by the aggregator in order to reduce the electricity consumption from the grid or inject power into it when necessary. From the customer’s perspective, we saw that the DR actions can increase the energy cost in some cases, highlighting the importance of economic incentives to attract customer engagement. In addition, in the Scenario 1, involving the HVAC system, the thermal comfort of the users was not affected by the presence of the aggregator, as the indoor temperatures were maintained in an adequate range. Finally, allowing the aggregator to control the battery in Scenario 2 did not have any effect on the self consumption factor of the user. Regarding OpenADR, a test was developed first virtually and then between the laboratory and the aggregator in Scenario 3. OpenADR proved to be a reliable and useful protocol that has the potential to be used in DR applications due to the different use cases it can coverObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.1 - Per a 2030, garantir l’accés universal a serveis d’energia assequibles, confiables i modern

Development of a platform for the assessment of demand-side flexibility in a microgrid laboratory

Demand-side flexibility has gained attention as a powerful tool to increase the flexibility of the electricity system and counteract the uncertainties caused by the increase of Renewable Energy Sources. Up to date, few markets allow the participation of Demand Aggregators, which are key to make use of the flexibility of small consumers. Therefore, research surrounding demand aggregation is in many cases limited to simulations or resource consuming pilot programs. This project integrates a microgrid laboratory with a commercial aggregation platform in order to set up and configure the necessary tools to operate the laboratory as a platform to test flexibility. The flexibility platform defined in this work offers a customizable and controllable environment for Demand Response and aggregation testing, while providing a realistic assessment due to the consideration of a commercial aggregator and the use of real and emulated devices. As a first application of the platform, two customer types have been defined and tested: a residential one with a Heating Ventilation and Air Conditioning Unit and a prosumer owning a second-life Electric Vehicle battery in a solar Photovoltaic self- consumption system. The scenarios have shown how, for defined users, the interaction with the aggregator can be beneficial for all sides, as long as proper activations and incentives are defined for the customers. Through future applications of the platform, new use cases can be covered and used to gather valuable information for the aggregator or any interested stakeholder.Peer ReviewedPostprint (author's final draft