Green Team Twente is developing a hydrogen-powered car that will compete in Shell's Eco-Marathon - a race to develop an ultra-efficient vehicle. The challenge: reliability. Because last year the car didn't make it to the finish line because of overheated fuel cells. Otherwise they would have been a good contender in the title race, as they could potentially cover some 900 km on 1 litre of fuel. That very low fuel consumption requires a good flow meter to steer the conversion process accurately and to gain insighst into possibilities for improvement. That's why they use a mass flow meter.
Marieke Altena, Hydrogen System Engineer, Green Team Twente
"This year our goal is to make the system reliable, but also to gain on efficiency where possible. The mass flow meter will give us a better insight into the hydrogen consumption of the system and the car during testing."
the battle of the team
It is June 2019 and the Green Team Twente is feverishly making the final adjustments to its vehicle. During the last test - a race in May in Eindhoven - it turned out that the fuel consumption is still too high, the range of the car is 1 litre of fuel is 210km and has to be brought to 900km in a few weeks if they want to have a chance of winning the title at the Shell Eco-Marathon in London on 5 July. Fortunately the problem seems to be relatively easy to solve.
Last year the team faced major challenges during the race: it was 30°C in London and the fuel cells overheated. In addition, the electronics suffered from interference. The finish line was not reached and the disappointment was enormous, because the car was a winner on paper.
flowmeter controls the process
At that time, during development in 2019, the flow of hydrogen could not be read. Grip on the process was necessary to prevent the uncontrolled rise in temperature that fatally affected them.
In fundamental, the reaction process in the fuel cell is faster as the temperature rises, but too hot also results in a loss of efficiency. The optimum is at 70°C.
The solution lies on two sides: measuring and controlling the flow of hydrogen and a better regulated cooling system with a higher capacity.
A flow meter has been chosen, which is being read via Modbus. This allows the team to precisely control the mix of air and hydrogen in the fuel cell. In addition, the team can correlate the data with data from other sensors in the system and thus, for example, optimise engine control.
The fuel cell is also equipped with thermocouples to determine the cooling requirement.
After testing in heat cabinets, the system was tested under race conditions. During a race in Eindhoven in May 3 hours were driven in which the temperature rose to just 70°C at an outside temperature of 25°C. And this without using cooling fans. A proof of concept to be proud of.
Hydrogen fuelcell development
25g hydrogen per 250km
Controlloop with zero drift