Development of hydrogen fuel cell

New liquid cooling system saves 20% of the energy

Niek Goselink is a hydrogen fuel cell engineer for the Eco-Runner Team of TU Delft. It is his responsibility to operate the fuel cell in the Eco-Runner 9 in an efficient and safe way. With the Eco-Runner 9, the team is looking forward to victory in the Shell Eco-marathon: a competition to make the most fuel-efficient hydrogen-powered vehicle. At the moment they can achieve about 9000km on 1kg of fuel. Teesing thinks along in the design and supplies components. Since the only emission of a fuel cell system is liquid water, a hydrogen fuel cell is known as a zero-emission power supply system.

Niek Goselink

“We are very grateful for the cooperation with Teesing, together we worked on a super efficient fuel cell system in a really efficient hydrogen powered vehicle! With this system we believe we are able to bring the first place in the Shell Eco-marathon back to Delft.”

The challange of the eco-runner team

"As Eco-Runner Team Delft we believe in the idea of hydrogen as an energy carrier and as a vital component in the energy transition. By building the most efficient hydrogen car, we hope to show the possibilities of hydrogen to the general public and create awareness on this subject. While raising awareness of the potential of hydrogen is one of our main drivers, our main focus in 2019 will be on building a highly efficient car. As mentioned earlier, the fuel cell is an essential part of this search for high efficiency. The fuel cell is the first component in the line that creates losses, when converting chemical energy (enclosed in the hydrogen) into kinetic energy (acceleration of the car). The fuel cell can make or break the efficiency target. With an inefficient fuel cell, the components connected to it will not be able to recover these initial losses. It is therefore of the utmost importance to optimize the operation of the fuel cell as much as possible. To do this, there are a few areas to focus on. First, the conversion of chemical energy into electrical energy is a process that takes place in the stack. By optimizing the size and conditions (temperature, pressure and humidity) in the stack, this transformation can be made more efficient, thus reducing losses.

THE OPERATION OF HYDROGEN FUEL CELLS

The fuel cell system is the heart of the car, because it produces the power that drives the car. The basic operation of a fuel cell system is very simple, it is the reverse reaction of electrolysis. In an electrolysis reaction, water H2O is split into hydrogen H2 and oxygen O2 by passing through an electric current. By reversing this reaction, in which hydrogen and oxygen are combined, an electric current is created. This is also the basic process that takes place in our fuel cell system. Both hydrogen from a small tank and oxygen in the air are added to the fuel cell stack as a reaction agent. To further understand the working principle of a fuel cell, we must first disassemble the fuel cell stack itself. The 'stack' is a series of cells in which the reactions take place. Such a cell consists of two electrodes (anode and cathode) divided by an electrolyte. In the case of the anode, the hydrogen is split into two separate protons, H+, releasing electrons and thus energy. These protons can penetrate the electrolyte, in our case a proton exchange membrane, while the electrons follow an electrical circuit to the cathode side. With the cathode, the protons that have penetrated the electrolyte will react with the electrons and oxygen from the air in the water. The flow of electrons through an external circuit from the anode to the cathode produces an electric current and can be used to drive a load, in our case an electric motor that drives the car.

Consumption saving of 20%

In addition, there is a chance for gains in the control of the fuel cell. The Balance of Plant (BOP) is the subsystem that keeps the stack of fuel cells alive. Making the energy requirements of this subsystem as low as possible increases efficiency. The system supplies the required quantities of reactants (air and hydrogen) to the stack and consists of a series of pumps, valves and circulation circuits. The BOP is fed by the energy produced in the stack. If we can reduce the power required for pumping, more power can be supplied to the motor to drive the car. Fortunately, these two areas are interrelated; the BOP regulates, among other things, the cooling circuit and the hydrogen recirculation, which influences the temperature and humidity. The aim is therefore to optimise the operating conditions while at the same time reducing the power requirements of the components. Niek: "As with any challenging engineering project, this requires a balance in our system to reduce the power required and increase the chemical reaction rate. For the development of the BOP, we are working with Teesing because they specialize in providing high quality tubes and connectors and designing subsystems." For the Eco-runner 9 we chose to renew all the tubes and connectors of the system and increase the diameter of the tubes. This in turn reduces the back-pressure created by the circulation circuits and thus lowers the energy requirement for pumping. The total energy gain in this subsystem is more than 20%.

New liquid cooling system

The redesign of the BOP is also an opportunity to take a closer look at the cooling system. The cooling system of recent years has included a heat exchanger with a cooling fan, a so-called active cooling system. Because the fan consumes a lot of power, they wanted to get rid of it and designed a more passive cooling system that uses less mechanical cooling equipment. That's why they added a thermal mass to the system, which is separated from the fuel cell itself. The thermal mass was placed in the engine compartment near the rear wheel. While driving, turning the wheel produces a turbulent air flow, which cools the thermal mass by convection. The coolant is pumped through the fuel cell and then pumped through the thermal mass. The heat extracted from the fuel cell by the coolant is released into the engine compartment, after which the fluid is returned to the fuel cell stack. Niek: "This new design requires double shut-off quick couplings for connecting and disconnecting the fuel cell system's cooling circuit. This shortens the installation time of the system. It also allows us to quickly increase the cooling capacity when the race is held on a hot and sunny day."

Consumption
Approx. 9000 km on 1 kg hydrogen

Fuel
25g hydrogen (250 km)

Weight
38 kg (without driver)

Top speed
Approx. 50 km/h

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