DRIVING ON HYDROGEN
Currently, we have two solutions for sustainable mobility: battery-electric or hydrogen-electric vehicles. A Tesla Model S or a Nissan Leaf are examples of battery-electric cars. The Hyundai ix35 Fuel Cell or the Toyota Mirai are examples of the current hydrogen-electric cars. According to our vision: hydrogen-electric will be the winner of both, but why? Therefore a few reasons.
Hydrogen is an energy carrier, just like a battery, but is has to following advantages:
- The weight of the battery pack of a Tesla Model S is 600kg, compared to the 5,6kg of hydrogen in a Hyundai ix35 Fuel Cell;
- Recharging a Tesla Model S will take about 3 to 4 hours, a Hyundai ix35 Fuel Cell can refuel within 3 minutes.
Green Team Twente therefore believes that hydrogen will play an important role in the road to sustainable mobility. More about hydrogen can be seen in this video:
MECHANICS OF THE CAR
Friction, it is all about friction. The challenge that never stops for the mechanics. Every part, every detail, everything has to be optimized to minimize friction. In consultation with our bearing manufacturer, SKF, the best bearings are chosen for each component. In this way, the friction is made a little as possible.
However, friction is connected to grip, without friction there is no traction. Without traction the car can not drive. The optimal performance can though be achieved. This year, Green Team Twente is working on a revolutionary concept witch will reduce the rolling resistance. More information will follow on the car presentation.
Last year, Green Team Twente stood in the spotlights with the gearbox. Using three engines which can switch on and off segregated from each other and are still connected with the same shaft was something exceptional. This provides a good basis for optimizing: better materials, more efficient transmission and gears that perfectly run over each other from the current gearbox.
Finally, mechanics focuses on weight. Each part is made as light as possible, every gram is counting. Stronger and lighter materials are used. Titanium brake discs, Aluminum 7075 milling parts and prepreg 160 grams carbon fiber body. The goal is to get the weight of the car beneath 100 kg.
The electrical engineers are responsible for all electronic systems in the car. Our custom made circuitry make sure the motors receive power, the buffer is charged and the hydrogen fuel cell is regulated. Besides these main tasks we have many PCBs that drive peripheral systems, such as the lights and the windscreen wiper.
The reason we make our own circuit boards is that we want to minimize all electric losses, as almost all readily available boards do not pass this criterion. We therefore have to design our own boards that are extremely efficient. This is a big challenge, but a very rewarding one! Not only are we learning a lot about efficiency and electronics, we are also working on problems that very few engineers have looked into, for example an incredibly efficient DC/DC converter with state-of-the-art Gallium Nitride transistors.
All electronic systems are part of either the primary system or the secondary system. The primary system uses the fuel cell output as power source and the secondary system uses LiPo-batteries. All systems that directly or indirectly influence the driving of the car are part of the primary system.
The primary system starts with the hydrogen fuel cell. This is the component that converts hydrogen and oxygen into water and electricity. All parts of the primary system are using this energy. Before this is used, the voltage is boosted to 48 volts with a DCDC converter. This is the voltage the rest of the system runs on. The power is then transported to the motor controllers which power the motors, after which the car starts driving. Energy that is not used in the motors is stored in the buffer, keeping in mind to minimize losses.
Which velocity is the car supposed to drive to consume the least amount of energy?
How can we boost the performance of the car?
Should the car take over in a particular lap?
All of these questions and more come together in our driving strategy and are solved by Yanna, our driving strategist. Yanna works together with all the other technical subteams to make an optimal driving strategy. The main idea is to validate and tune the performance of the system with the aids of certain methods and tools. The art is to analyze and predict the behavior of the car on track, by knowing both inside out. This is done by creating simulations and closely working together with the whole team, so sufficient information as input is assured. Finally, a plan is evaluated, taking into account the track (curves, hills, …), weather, safety, fuel load, tire wear, etc. And last but not least: a bit of luck!