Thermal Comfort for Electric Vehicles – Longer driving range for electric vehicles through optimized battery management

Thermal Comfort for Electric Vehicles – Longer driving range for electric vehicles through optimized battery management

What is the ideal operating temperature for electric cars? At what temperature do they perform best? The participants of the European research project JOSPEL are addressing just these questions by assessing the optimization potential of electric vehicles. The project aim is to increase the energy efficiency and range of electric vehicles by applying efficient and cost-effective climate control solutions especially developed for battery electric vehicles. Experts at Fraunhofer ISE are working with industry partners on optimizing battery operation, with the goal of increasing battery lifetime through improved thermal management.

Battery Electric Vehicles – Major Potentials, Major Obstacles

Today there is much discussion about transforming the transportation system and thus battery electric vehicles (BEV), i.e. electric cars, buses and the like. Environmental pollution due to traffic in urban areas is becoming increasingly evident. This is supported by air pollution measurements that show the upper boundaries set down by law are often exceeded. The diesel scandal and the public debate about implementing restrictions on driving are examples of the problems facing today’s transportation system.

Electric vehicles can help solve this problem, yet they are only slowly finding their way onto the streets. Hesitation still exists, although various types of electric autos are available that have long been proven fit for daily use. Reasons for this are the high cost of purchase, some uncertainty about the future development as well as a shorter range, which is especially critical due to the longer charging times.

The JOSPEL Project

The JOSPEL-project’s aim is to increase the energy efficiency and range of electric vehicles by applying efficient and cost-effective climate control solutions especially developed for battery electric vehicles. By climate conditioning, one thinks immediately of the passenger compartment, however, it also is relevant for the optimized thermal management of the car battery. Fraunhofer ISE is working on this particular aspect together with partners from industry.

The goal of the working package under the leadership of Fraunhofer ISE is to increase the battery lifetime by at least 15 percent and at the same time reduce the energy needed for battery cell temperature control by 12 percent. The name “JOSPEL” stems from a combination of the Joule and Peltier effects that serve as the basis for the technologies developed.

The Simulation Model: Searching for the Optimal Temperature

At the beginning of the project, we informed our partners about the available lithium ion battery cells and their most important characteristics. Then, a suitable battery cell was selected for the project using a tool, developed at Fraunhofer ISE, to carry out a cost-benefit analysis. The chosen cell was then measured in detail in the Center for Energy Storage Technologies and Systems. Using the measurement results, we developed simulation models to determine the electric and thermal behavior and the course of aging. These were verified by performing additional measurements.

A battery cell being placed in a climate chamber and connected to the measurement electronics. In the background, one can see two other test cells, fastened between aluminum plates. ©Fraunhofer ISE
A battery cell being placed in a climate chamber and connected to the measurement electronics. In the background, one can see two other test cells, fastened between aluminum plates. ©Fraunhofer ISE

Based on these models, we developed a simulation to determine the effect of different parameters on the efficiency and battery aging. The parameters considered included various operating parameters, cooling and heating scenarios and operating strategies.

Decrease in the battery cell capacity at no load over time (calendrical aging). Measurements were carried out on two cells at different storing temperatures and states-of-charge. It was observed that higher states-of-charge and higher temperatures accelerated the aging process.
Decrease in the battery cell capacity at no load over time (calendrical aging). Measurements were carried out on two cells at different storing temperatures and states-of-charge. It was observed that higher states-of-charge and higher temperatures accelerated the aging process.

Measure the Success:  Increases in Efficiency and Lifetime

Using development tools, we can not only determine the ideal temperature range for the chosen battery but also define various beneficial operating strategies. One example looks at preconditioning the temperature of the battery system before start. The simulations showed that it is better to heat up a cold battery system before starting to drive.

Although additional energy is required to heat the battery, a warmer battery provides more energy, that is, it runs more efficiently at higher temperatures. The higher energy efficiency on the other hand positively influences the range and aging. In all, these aspects justify the additional energy expenditure. With the simulation tools of Fraunhofer ISE, such synergy effects can now be identified for special applications and also be proven with hard numbers.

Thanks to optimized operating strategy and increased efficiency, smaller decrease in electric vehicle battery capacity evidenced over the period of use.
Thanks to optimized operating strategy and increased efficiency, smaller decrease in electric vehicle battery capacity evidenced over the period of use.

The project is currently in the final third of the project duration. In this phase two demonstrators are to be built in order to test the functionality and advantages in the field.

 

Further Information…

 

Further videos of the project partners

Research Topic »Battery Systems for Stationary and Mobile Applications«

 

Das EU-Projekt »Jospel« verfolgt u. a. das Ziel, durch optimierte Batteriebetriebsführung Energieeffizienz und Reichweite von Elektroautos zu erhöhen.

Maximilian Bruch

Maximilian Bruch

Project Manager at Fraunhofer ISE
Maximilian Bruch hat Maschinenbau an der Hochschule Augsburg studiert und den Master of Science im StudiengangSENCE (sustainable energy competence) an der Hochschule Ulm erlangt. Er arbeitet seit 2013 am Fraunhofer-Institut für Solare Energiesysteme in der Gruppe Batterietechnik. Hier beschäftigte er sich hauptsächlich mit der Simulation von Flussbatterien, der Weiterentwicklung des Formierungsverfahrens in der Herstellung von Lithium-Ionen Zellen, der Charakterisierung von Lithium-Ionen Voll- und Halbzellen sowie Beratungs- und Messdienstleistungen. Aktuell leitet er im europäischen Forschungsprojekt JOSPEL die Entwicklung des Batteriesystems mit optimiertem Betriebsmanagement.
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Maximilian Bruch studied Mechanical Engineering at the University of Applied Sciences Augsburg and received his Master of Science in the course of studies SENCE (Sustainable Energy Competence) at the University of Applied Sciences Ulm. He has been working at the Fraunhofer Institute of Solar Energy Systems ISE in the Battery Technology Group. His work focuses mostly on the manufacture of lithium ion cells, the characterization of half and full lithium ion cells as well as consulting and measurement services. Currently he is head of the European research project JOSPEL, in which battery systems with optimized operating management are being developed.
Maximilian Bruch

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