Realism and visions at Nordbatt 2013
Future concepts for Li-ion batteries, particularly the need for improved batteries for electric vehicles, was the theme for the first Nordic battery conference.
The conference attracted researchers from the Nordic countries along with internationally well-distinguished battery scientists. Part of the program was devoted to vehicle perspectives, and opened by Dr. Bor Yann Liaw of University of Hawaii, invited by SHC.
-Dr. Bor Yann Liaw works with a method for battery diagnosis, which simulates battery behavior under different ageing and operating conditions, says Elna Holmberg, manager at SHC. His work is in many ways related to the battery research at SHC. His presentation included two case studies of cell aging behavior, the first illustrating the impact of cell design on aging behavior, and the second showing the impact of overcharging the battery.
The vehicle oriented part of the program then ranged from realistic to visionary, starting with Scania, Volvo Cars and AB Volvo presenting their current battery research and ending with Göran Lindbergh, KTH, talking about carbon fibers in structural batteries and how to make use of multifunctional properties. Battery research for heavy duty vehicles and the importance of safety standards were among the other topics that were discussed during the day.
-An interesting and well composed conference with high relevance, concludes Elna Holmberg.
Text: Emilia Lundgren
Structural batteries – a unique compromise for lighter electric cars
The weight of the battery is one of the largest obstacles to overcome for electric and hybrid vehicles. By using the battery as part of the chassis significant weight reductions are possible. In a recently completed EU/FP7-funded project on structural batteries, one of the participants was Prof. Patrik Johansson at Applied Physics, Chalmers, likewise one of our SHC researchers.
– We have investigated materials that can store and deliver energy and also carry load, says Patrik Johansson. The idea is neither to make the best energy storage nor the best construction material. But the compromise, the ’multi-functionality’, is really unique.
The batteries are made as laminates and are extremely strong. Patrik Johansson shows something most of all looking like a weave of carbon fibres, a few millimetres thick.
– This is a composite of glass fibres and carbon fibres. It is moldable as any composite. Within there is a special electrolyte, not a liquid, but based on a gel polymer matrix. In our research group we have foremost investigated the transport properties of this kind of electrolytes.
Composite materials for reduced weight
The thin and flat batteries are shaped to be part of the chassis of the car. This way the parts that need mechanical strength also be used to contain energy. For example batteries have been integrated in the plenum cover, replacing metal by the lighter composite material. The gain is a severely reduced weight. This construction was made by Volvo Car Corporation – a partner in the project.
– With this basic idea we avoid the battery being solely a ’burden’ for the vehicle, says Patrik Johansson. This conceptual thinking we keep in mind for future projects.
Partial replacement for traditional car batteries
The aims with the structural batteries are to provide enough energy to relieve the traditional 12 V battery and to be chargeable also from an external source. They will, however, not likely be enough for the propulsion of an electric car.
– As I see it today, we will not be able to store enough energy to enable vehicle propulsion, says Patrik Johansson.
Many issues remain to be solved regarding the integration in vehicles of these batteries from a production perspective, but Patrik Johansson anyway believes that structural batteries have a bright future.
– Yes, I firmly believe so. However, it is not at all for sure that the final implementation will be in vehicles. Vehicles have very tough demands on safety, cost, and recycling. But there are perhaps other niches in the future, unknown to us at present. It is the basic idea and the concept itself that is cool!
The EU/FP7-funded project on structural batteries, STORAGE, was finalized in June 2013.
Volvo Car Corporation
Chalmers University of Technology –
The Departments of Applied Physics and Materials and Manufacturing Technology
ETC Battery and Fuel Cells Sweden AB
Text and photo: Emilia Lundgren
Energy efficiency attractive for heavy utility vehicles
Energy usage surveys and energy improvement of hydraulic systems are some of the topics that attract the interest of utility vehicle manufacturers.
Anders Grauers, Chalmers, driveline expert within SHC, was recently invited to talk about driveline solutions at a workshop on Energy efficiency, arranged by The Association of Heavy Vehicles (Tunga fordon). The association is a cluster of heavy utility vehicle manufacturers in southern Sweden, active within the sectors of forestry, construction and heavy material handling.
Did you arrive at any interesting results at the workshop?
-Yes, one interesting result was that a change in the driveline which can increase the vehicle productivity possesses a greater value than just that of reduced fuel consumption. As a rule, increased productivity will lead to lower fuel consumption for each task performed by the machine. Hence, it could be of interest to investigate if hybridization can increase the productivity, e.g. by increased precision and quicker driveline control.
What did you talk about?
-I talked about the reasons for hybridization, fuel saving being one important motive. I also described how hybridization will affect the vehicle in many different ways, and showed ways to reason in order to determine which solution is the most adequate for a certain vehicle. To inspire to think freely around different hybridization aspects, I provided examples from various types of vehicles where the solutions and reasons for hybridization vary. Finally, I pointed out that there is a difference between what is profitable and requested today, and the demands that will be put on the vehicles in the future.
What are the differences between drivelines for utility vehicles and road vehicles?
-The differences between different types of utility vehicles are often at least as big as the differences between road vehicles and utility vehicles. It is not easy to speak of utility vehicles as a group. However, one significant difference is that the energy used for propulsion is generally just a fraction of the total energy consumption of the utility vehicle, which often makes it more important to study energy improvements in other parts of the vehicle than the propulsion system.
Could you say something more specifically about the types of vehicles manufactured by the participants of Heavy vehicles?
-One important factor is that the utility vehicles in question are produced in small series. Therefore it is not reasonable to develop special components for just one type of vehicle. The required components must be suitable for a number of different vehicles.
Can any of the studies made within SHC be of use for The Association of Heavy Vehicles?
-Yes, at the workshop there was a great interest for surveying the energy consumption in the vehicles in order to find out the potentials for fuel saving with different solutions. Several of the energy study methods made within SHC could be useful for such an analysis.
What kind of questions did the workshop participants ask you?
-They asked about how to hybridize heavy road vehicles, and they were curious about the differences and similarities between hybridization of “their” vehicles and traditional trucks and buses. In the part of the workshop where future projects were discussed, there was a lot of talking about the hydraulic systems and whether it is possible to regenerate energy from them in an efficient way.
How far do you think they have come towards hybridization?
-Of course there are big differences between the companies, where some are working with, or have made investigations into the possibilities of hybridization, while others only just have asked themselves what it would mean for them. It is also important to understand that these companies are aiming to present vehicles with good properties at an attractive price. This means that hybridization is not a goal in itself, but one of many ways to produce a cost effective vehicle.
The workshop Energy efficiency was part of a project in cooperation with Chalmers Energy Initiative.
The Association of Heavy Vehicles (Tunga fordon) is hosted by SP Sveriges Tekniska Forskningsinstitut. Participants: Volvo CE, SP Maskiner, Svetruck, Semcon, Ljungby Maskin, Gremo, Cargotec, Alucrom, Dasa Control Systems, Kärcher-Belos, Fogmaker International, Rottne Industri AB
Text: Emilia Lundgren
Photo: Oscar Mattson
Log data will provide relevant driving cycles for hybrids
Lars Nielsen, Professor at Linköping University, runs the project and is supervisor of one of the doctoral students. Lars says that the use of driving cycles in the automotive industry is increasing, but that so far they have proved difficult to generate and have been criticized for not being adapted to the prerequisites of the actual customers. The use by scientists of data e.g. from gps devices opens up new opportunities for customizing cars and correcting any mistakes earlier in the production chain.
– Now we can make use of large amounts of logged data from actual vehicles and take into account factors such as country, season and climate, explains Lars Nielsen. Such systematical use of large amounts of data to produce driving cycles is new and almost untried.
Further opportunities for hybrid vehicles
For hybrid vehicles, access to log data provides further opportunities to test how the driveline can be utilized optimally. From the driving cycle, load curves can be extracted for the internal combustion engine as well as for individual hybrid components.
– There is not much previous knowledge about hybrid cars, explains Lars Nielsen. Therefore more studies are required before launching a hybrid car. Relevant driving cycles make it possible to study for example how the battery is affected or how the energy management is acting during various types of driving.
Looking for methodology for the use of log data
There are no established methods as yet for how the logged data should be used in the driving cycles. The research will include the question of what such methodologies could be like.
-We ask ourselves how one can describe a large database using statistical measures and then generate a driving cycle with the same statistical measures, says Lars Nielsen. We also want to investigate how long the cycle needs to be for all the relevant data to certainly be incorporated, and find out which characteristics must be included.
The researchers want to develop a number of cycles which are equivalent but not exactly the same, which in a characteristic way describes what the vehicle is undergoing. By comparing the cycles, their relevance may be assessed and erroneous conclusions avoided.
The project involves researchers from Chalmers and Linköping University, whereof two doctoral students.
Participants including the steering group:
Lars Nielsen, LiU
Jonas Sjöberg, Chalmers
Anders Grauers, Chalmers
Viktor Judez, Chalmers
Peter Nyberg , LiU
Sören Eriksson, VCC
Mattias Björkman, Scania
Sixten Berglund, AB Volvo
Text: Emilia Lundgren
Photo: Peter Modin
Four questions for Daniel Wanner
Daniel Wanner will shortly hold his licentiate seminar entitled “Faults and their influence on the dynamic behavior of electric vehicles”.
You have developed a methodology to analyze and classify faults for electric vehicles. Why do you think this is important?
-The electrification of vehicles brings new functionalities of the vehicle in terms of safety, comfort and handling. However, these innovative systems might also fail once in a while. Therefore it is important to know what type of fault in these systems that leads to what kind of failure in the vehicle.
What have you focused on?
– I focused on faults in the electric driveline. All of its components are new to the automotive industry and therefore not as well-known as those of the internal combustion engine.
Above: A vehicle with and without fault-tolerant control strategy. When a fault occurs leading to a failure braking the rear left wheel, only the vehicle with fault-tolerant control (green trajectory) keeps stable, avoiding an accident.
Which has been the greatest challenge in your work so far?
–The biggest challenge was to limit the scope of the project. After I got the position, the project was defined very broad. However, to be able to analyze something in detail, you need to narrow down the scope in the beginning. In a later stage, the results can then be used to make more general conclusions again.
The seminar will be in a few days. How will you proceed from there?
– After the faults are analyzed and classified, I will use the results to develop new control strategies that can cope with the faults to help the vehicle to stay on the road. I will implement these strategies in a prototype vehicle to evaluate if the results from my simulations will be valid in real world experiments.
Daniel Wanner will hold his licentiate seminar at KTH on October 18th 2013.