Thermal management is important for electric and hybrid electric vehicles. Automotive IQ spoke with Phil Barker, Chief Engineer - Hybrid & Electric Vehicles at Lotus Engineering, to gain some insight into the topic. This is Part 1 of a 2 part interview and is part of our series: Automotive Industry Faces.
"One aspect that we do see with hybrids that we don't necessarily see with combustion vehicles is that there are lower temperature operating ranges as well as high"
Automotive IQ: Could you describe your background and your role with Lotus Cars?
Phil Barker: My background is actually in mechanical engineering. That’s what I graduated in back in 1990 and I've worked in the automotive industry ever since then. I started out in the UK at an independent design consultancy called International Automotive Design. That company was taken over by Daewoo Motor Company when they wanted to become active in the European market and so they created a technical center with what was left of IAD. So I continued working with Daewoo Motor Company and then after some years they went into liquidation and in the UK its assets were taken over by TWR, Tom Walkinshaw Racing. The technical centre continued with TWR until they went into receivership in 2003. So over the years, I've worked 100% in the automotive industry as an independent design consultant, as an OEM through Daewoo Motor Company and prior to joining Lotus, I worked at Jaguar Land Rover also in the UK. I worked with them for about a year on the Range Rover Sport program amongst others and then I made the move to Lotus in January 2004.
Automotive IQ: That's quite a progression.
P.B.: Indeed. As I mentioned, I graduated in mechanical engineering and I reached the position of Technical Specialist on all chassis systems and that's what I was taken on for by Lotus Engineering. The first program that I worked on, I was responsible for suspension systems and steering systems, but I very quickly migrated on to hybrid vehicles with my knowledge of the complete vehicle - all the chassis systems and knowing how all the systems operate and interact with each other. This was a very good grounding for working on hybrid vehicles because the knowledge of how all the systems are integrated into the vehicle is an incredibly important aspect of hybrid vehicles.
Automotive IQ: Why is thermal management particularly important modern EVs or hybrid vehicles?
P.B.: It's not just for modern EVs or hybrids. If you consider thermal management of conventional vehicles, it's also incredibly important. Engines need cooling, if they don't get cooled then they will fail and it's a simple crossover into hybrid vehicles. If you don't operate the systems within the temperature capabilities then things will go wrong and that's why thermal management is very important.
One aspect that we do see with hybrids that we don't necessarily see with combustion vehicles is that there are lower temperature operating ranges as well as high. So for combustion engines you need to cool them, for battery packs, again, you need to cool them, but also you need to operate the battery pack at temperatures that are the right side of zero degrees, the right side of freezing. So thermal management, both cooling and warming, is important for hybrid and electric vehicles.
Automotive IQ: Do you draw some of the knowledge of, particularly, the heating part of the battery from more traditional car batteries?
P.B.: A lot of it depends on the actual battery chemistry. We've got to create a thermal management system that operates the cells within the stated characteristics. The whole world is very familiar with lithium chemistries now but even within the lithium family of chemistries there are cells that can operate at wider temperature ranges than others. So it's very important to have a very good understanding of the operating characteristics for the particular cell that you're using for the particular chemistry, and in some cases we have chemistries that are alternative to lithium. In one case, the battery pack actually uses some of its energy to heat the battery pack because its operating temperature is elevated in the region of maybe 250 degrees. This creates an entirely different aspect to thermal management.
Automotive IQ: In terms of the greatest challenge that you see, it tends to be operating in this optimal temperature range. What are some of the strategies that you use to overcome that particular hurdle?
P.B.: Generally the projects that we've been working on have created demonstrator vehicles and these are vehicles that are used in a very controlled environment. So, for example, we understand that the majority of the thermal management for battery packs is cooling, so keeping them working below a certain temperature level. For some chemistries it's maybe 60 degrees that you want to keep the battery below. The batteries can operate at higher temperatures, even with some of the lithium chemistries they can tolerate 120 or 150 degrees. So generally it's the cooling aspect. But when we're working on projects or concepts that are looking at production solutions then it's important to understand what we need to put in place for vehicles that are maybe operating in lower temperature environments. Typically an OEM would design their vehicles to operate at -35° C up to +45° C. In that way, you would need some sort of heating system. Some of the systems that we've worked on in the past for cooling have been simply ducted air. So we have fans making sure that there's a constant stream of airflow within the battery pack. In other cases we've had a liquid cooling system where we've had, for example, cooling plates with cooling channels in and we simply have a water/glycol solution going to a heat exchanger like a radiator, for example.
Automotive IQ: Would you foresee then that you would have different variations of the car for different markets? Or do you try to design so there's just the one and it really manages to operate efficiently in the whole range of temperatures it would encounter?
P.B.: That depends on the program. If it's a one-off demonstrator or a handful of vehicles that you're doing as a demonstration fleet then the solutions that you put in place may well be very suitable for those kinds of vehicles but not necessarily the level of thermal solution required for a production solution. So really it's matching what is the most appropriate solution for that particular project or that particular application.
This is part 1 of a 2 part interview and is part of our series: Automotive Industry Faces.
Read the Conclusion to our interview with Phil Barker