Iskender Demir: A Conversation About Solar Powered Vehicles
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Andrew: Iskender, how did you get started in the field of solar-powered cars?

Iskender: I’ve been really passionate about electromobility for more than 14 years. That is why I studied electrical engineering and began working in the field of electromobility early on, alongside my university studies.

The first rollout of Team Sonnenwagen Aachen caught my attention. The mission, the passion and the team spirit directly inspired me. To see more than 40 students who put all their free time, studies and more aside to do nothing but develop one of the most efficient electric vehicles in the world for two years and work together day and night to make this vision a reality – I just had to be part of it.

So, at the beginning of 2018, I became a member of the second team in the electrical engineering department and mainly took care of the solar cell system, but also worked on topics like the battery and the general electrical system. Our goal, the World Solar Challenge, is one of the most exciting adventures and experiences you can have as a young engineer. Pushing the limits of electric mobility and solar cells and driving 3000 km across the Australian outback with a self-developed and self-constructed solar car is something you will never forget for the rest of your life.

Andrew: The naysayers are rather confident that solar-powered cars for the masses is not a technology worth pursuing. Would you say that their assessment is fair?

Iskender: It depends very much on how you look at it. Up to now, EVs have been measured primarily by their range. And there is a lot happening here, the vehicles achieve higher and higher ranges.

However, if we look at average daily driving distances, it also starts to become interesting for solar vehicles. In Germany, for example, the average daily driven distance is just about 40 km. For these ranges, you can already easily supply the energy solely with solar cells. And, of course, solar cells continue to develop and thus the potential of solar yield. Naturally, the more days of sunshine a region has, the more self-sufficient the vehicles will be.

Due to seasonal changes in most regions of the world, there will be times, where there is just not enough solar energy for a solar car. Nevertheless, solar cells can already ensure that vehicles can manage without charging for a large part of the summer, except on long journeys. However, the vehicles can still be charged.

To summarize: driving 100% self-sufficiently only with solar energy will not be possible for many, but the technology has already advanced far enough to be able to cover a large part of the distance traveled with solar cells and to at least greatly minimize the charging processes for the user, especially in summer.

Andrew: From the different discussions you’ve had with people in the mobility industry, what is the biggest misconception you hear the most when it comes to solar-powered vehicles?

Iskender: The topic of solar vehicles is often treated according to the motto: “Let’s put solar cells on the vehicle and see if it works.” But it is not as simple as that. For solar vehicles with a high solar range, the overall concept is extremely important.

The energy we can get from the solar cells is limited by the surface of the vehicle. Solar cells are continuously evolving, and the potential yield is increasing, yet it is not enough to only look at the photovoltaic side.

One of the most decisive factors is the efficiency of the vehicle. An issue that is becoming increasingly relevant for EVs in general. Efficiency affects the range, the battery size, the charging time, if we consider the recharged km per min as a factor for charging, but also how many km a vehicle can cover only by using solar power.

In order to really assess the potential, you have to look at the overall concept.

Andrew: From your perspective, what would you say is the technical tipping point to make solar-powered cars work?

Iskender: Solar cell technology is constantly evolving and yet, of course, the area and therefore the yield that can come from solar cells is limited. During the World Solar Challenge 2019, for example, we used solar cells with efficiencies of over 34%, which are usually used in space. However, these are not yet suitable for the mass market due to their high price. Currently, mainly silicon cells come into account for this purpose, which today already achieve just under 25% efficiency. However, a lot is currently happening in this field and there is still great potential.

But even more important is the issue of efficiency, which affects the entire vehicle. Aerodynamics, for example, is an enormously important factor, and even more so for electric vehicles than for combustion vehicles. But also, the drive components such as the battery, the inverter and motor, as well as the entire tuning and combination of the vehicle, must be developed with an eye for efficiency. You can see that the mobility industry is paying more and more attention to efficiency in general, because it is also an enormously important factor for pure EVs, not just solar powered cars.

Andrew: You once participated at the World Solar Challenge. How did you get selected for the team and how was the buildup leading to the race?

Iskender: The application process at Team Sonnenwagen Aachen is easy if you are motivated and ready to get out of your comfort zone. Of course, it is also good to bring experience with you, but the most important thing is that the people in the team are passionate. Everyone in the team was responsible for doing their part in order to build the best solar car in the world and be the first to drive through the finish line in Adelaide, Australia.

At the beginning of the two-year development of a new Sonnenwagen, we start from scratch. We evaluate data from the previous vehicles and incorporate the experience into the new one, but all components are reviewed and therefore completely renewed or improved. You can see this quite clearly in the differences between the vehicle designs of the first and second Sonnenwagen. For a full year, we only did research on different topics for the car’s development.

The development phase is then followed by the production of the vehicle, which takes half a year and was an extremely intense time period. In shifts, often also at night, the car is produced by the team itself. For example, the entire team works on the production of the carbon fiber monocoque and the outer shell. You bond as a team in a completely different way when you spend hours grinding with your teammates on the same spot - a team-building exercise that I can only recommend to everyone.

After that, the vehicle is tested in Germany, the logistics are carried out and the whole team goes to Australia for two months. During those two months, the vehicle is tested in the outback, optimized and brought into race setup. The race usually starts in October and goes from Darwin to Adelaide. For the 3000 km, the better teams need around four to five days. The cars drove up to 90 km/h on average, an obvious handiap thanks to the limitation of being only powered by the sun.

You can see that the mobility industry is paying more and more attention to efficiency in general, because it is also an enormously important factor for pure EVs, not just solar powered cars.
Iskender Demir

Andrew: How did your team from Aachen adjust to the Australian setting? What kind of impact did the change in scenery have on your design?  

Iskender: We optimized the Sonnenwagen exclusively for the race in Australia. For example, the rear part of the car points down, a measure that is advantageous both aerodynamically, but also because of the solar cells. As the sun always shines north on the car and we're going south, that gives us a lot of Watt-hours of energy. The whole circuit of the solar cell system is optimized by the simulation of the shadows along the track in Australia.

In addition, we can pitch our car when going straight, allowing our vehicle to set an optimal sailing angle, a measure that has resulted in extremely low energy consumption at 100 km/h. Normally, we need power of over 1 kW for such high speeds, but we were able to undercut this significantly in certain sections by sailing. The vehicle design has the effect of a sail, so that crosswinds can be used to reduce the consumption of the vehicle. This can be seen from the bullet-like shape of our vehicle.

These are some examples and apply to all components of the vehicle. It is a race car that is optimized to compete as efficiently and as quickly as possible in the World Solar Challenge. For all the optimizations, we do a lot of research out of Aachen, analyze historical weather data, vehicle data from the last races and access a lot of other data. During testing in Australia, we then adjust details so that we have an optimum configuration for the race.

Andrew: Can you tell us about your experiences in the race?

Iskender: The entire development process, pushing the technical boundaries and dealing with extraordinary challenges has shaped me greatly as an engineer. I learned an enormous amount and gained valuable practical experience that I don't want to miss.

The World Solar Challenge is called a challenge for a reason. The race takes place on public roads without special barriers or such. Every day you have a time slot of nine hours, during which you are allowed to drive. The race day starts at 8am and ends at 5pm. When darkness falls, kangaroos head for the warmed-up roads, which poses a great risk for accidents. At 5pm, we have to stop and at this point a marker is made. No matter where we are with the Sonnenwagen at 5 p.m. - that's where we'll spend the night. Of course, during the race there are also control stops along the route that must be reached within a certain time window, where you have to stop for 30 minutes and are not allowed to touch the car. This is a welcomed break, especially for the drivers, as it gets extremely warm in the cars.

For the duration of the race, the team is divided into two crews. They are the race crew and the support crew. Every single member of the team is indispensable, and everyone contributes a very important part to the success of the race. The race crew is very close to the race. I was part of the race crew and it was an extremely nerve-racking job. You're constantly on the lookout and watching what's happening at the race. Strategies are adjusted, competitors are overtaken, the car is monitored technically. The support crew takes care of the smooth running of the race around the camp and the supply of all team members.

I highly recommend the YouTube Originals documentary "Light Speed" by Seeker, which accompanied the 2019 race. You’ll get a very good insight into the spirit of the race.

All the factors, all the effort and all the organization of the project, from fundraising, research collaborations, from the screw to the whole car and the whole race, the exchange with the teams from all over the world, at every step I learned and developed enormously.

Andrew: What would you say was the toughest problem you and the team had to solve?

Iskender: The competition is very tough. Some teams have gained a lot of very essential experiences over their multiple participations in prior events. To win the race you must make innovations and be steps ahead. And with the second vehicle, we have taken an enormous step forward from a technical and innovation point of view. Our vehicle was very fast and efficient.

The race went very well for us, even though our lack of experience in Darwin meant that we got caught up in rush hour traffic in the first few hours of racing and hit a lot of red lights, which knocked us back from 2nd to 7th place initially. But we made up the places over the race and already had the podium in sight, our race strategy had calculated a very good finish time.

2019 was a very tough year and the race was accompanied by forest fires, very hot temperatures and very strong winds and sandstorms. On the penultimate day of the race, unfortunately, it hit us, like many other top teams: In a moment with extremely strong crosswinds of up to 100 km/h, bad road conditions and a road train, big trucks with two or more trailers, that caused turbulence, our vehicle lost control and overturned - a huge shock for everyone. The most important thing: nothing happened to our driver. The structure, especially the roll bar, was very well designed, so the monocoque easily endured it. Nevertheless, it was a very tough moment. We all worked for this car for 2 years, the race was going really well - and all of a sudden the car was heavily damaged.

One thing that will shape me forever: after we made sure that our driver was okay and we gathered ourselves emotionally after 10 minutes, we came together and decided not to give up. We analyzed the damage of the vehicle, checked what needed to be done, split up tasks and repaired the vehicle on the spot for hours. Everyone pitched in and gave their all, which is something I really appreciate and love about our team. And so we were still able to finish the race successfully.

Andrew: How did you guys perform in the end? Did you get to secure a podium finish?

Iskender: There is this one saying in endurance racing: To finish first, you have to finish first. And that was totally the spirit of the World Solar Challenge 2019. Many of the top teams have been kicked out of the race by the harsh weather conditions or other unpredictable incidents. Nevertheless, I think we can be extremely proud of ourselves that we managed to get back on the road again.

Before the crash we had the chance to be on the podium, if not even first place, but because of the accident we came in sixth. Which is - due to the fact that we had to fix the car for six hours – an enormously good result.

For our exemplary safety behavior and our remarkable will to continue the race after the crash we got rewarded with the Event Safety Award and the David Fewchuck Spirit of the Event Award.

Andrew: That's fantastic! I can imagine participating in such a project would help you gain the experience you otherwise wouldn't have gotten in a classroom. After such a great experience, can you tell us what you are working on these days?

In November 2020, I completed my electrical engineering master's degree at RWTH Aachen University. Since January, I have been doing an MBA at the Collège des Ingénieurs, an international MBA program for ambitious engineering graduates, which runs until November. Part of the MBA is a corporate project, which I am currently completing at Volkswagen Commercial Vehicles. There I am in the department that is developing the autonomous Volkswagen Bully, which is the autonomous Volkswagen ID.Buzz. It is an extremely exciting project and an important step for the mobility of the future.

In September the European Solar Challenge will take place in Zolder on the former Formula 1 race track. A 24-hour race on a race track in Europe - a completely different setting than the endurance races through the outback. It will be the first race for the all-new third generation Sonnenwagen. This race is a great opportunity to bond the team and practice important race procedures and communication structures.

I will be competing as part of the alumni team with the second Sonnenwagen. The closer the race day gets, the more I am looking forward to the action at the race track again. At the same time, I am also looking forward to the preparations for the race, the meetings in the office, and getting the car ready for the race again.

Andrew: Thank you very much for your time Iskender! We're very much looking forward to seeing what you accomplish in the future!

Iskender: My Pleasure!

Photos courtesy of Iskender Demir & Sonnenwagen Aachen