The UBC Chem-E-Car Blog

Powering The Future (Or just the Chem-E-Car)

By Fiona Abigail D'Silva, Stuthi Hegde and Jeffery Kung

February 28, 2017


Chem-E-Car’s New Fuel Cell Division

While the chemical team is building clocks and electrical team is making a new stopping mechanism, the fuel cell team is here to ensure that the car has the power to move! This year, UBC Chem-E-Car’s Junior Battery team has expanded to incorporate a new fuel cell division. Several universities have had overwhelming success using fuel cells in their cars, and we’re hoping to cash in on this as well. We are currently designing a safe and reliable way to generate, store, and transport hydrogen gas into a PEM (Proton Exchange Membrane) fuel cell. We are working towards incorporating our fuel cell system into next year’s Chem-E-Car entry.

Why We Chose a PEM Fuel Cell

There are many different kinds of fuel cells, but all of them operate on the principle of converting the potential energy of chemicals into electrical energy. We chose to use a Proton Exchange Membrane (PEM) fuel cell, which uses hydrogen and oxygen gas as reactants. The PEM fuel cell has the most realistic operating parameters, and were a lot safer to use than the other types of fuel cells. For example, the Direct-Methanol fuel cell runs on methanol (causes blindness, comas, and death), and the solid oxide fuel cell requires an operating temperature of $700^{\circ}C$.

Operating procedure of a PEM fuel cell

Hydrogen and oxygen gas are channeled through the flow fields of the fuel cell. The hydrogen enters the anode while the oxygen enters the cathode.

  1. The hydrogen gas undergoes oxidation at the anode. The anode contains a catalyst that increases the reaction rate of this process. Platinum is particularly effective at this, and is often used in anodes.

  2. The PEM blocks the electrons from moving throughout the fuel cell, creating an electric potential. Consequently, the electrons are forced to move through the circuit connected to the fuel cell, creating an electrical current.

  3. Since $H^+$ is a proton, it is able to pass through the PEM in the fuel cell. The hydrogen ion, oxygen, and the free electrons react at the cathode to produce water.

Reactions:

Cathode: $O_2 + 4H^+ + 4e^- → 2H_2O$

Anode: $2H_2 → 4H^+ + 4e^-$

Overall: $2H_2 + O_2 → 2H_2O$

Hydrogen Safety

All of CHBE’s faculty were more than a bit worried when we told them we were going to work with hydrogen gas because it explodes when it reaches its lower flammability limit. This is when we decided to use a hydrogen generator to produce high purity hydrogen. The hydrogen generator works under the principle of electrolysis which is the splitting of water molecules into hydrogen and oxygen. While the electrolysis experiments we all performed in high school results in venting the gas immediately, we will be using this hydrogen gas to run a fuel cell which will power our shoe-box car. This means that we will have to be extra careful about hydrogen generation and storage.

Schematic of our hydrogen fuel cell

Safety

We needed to prove that we would be working under safe conditions and came up with the following guidelines:

The fume hood’s ventilation must be sufficient enough to absorb hydrogen in the case of a leak. Proven by $M­_{max} = \frac{Q_{H2}}{Q_{fume}}$, where $Q_{H2}$ = flow rate of produced hydrogen; $Q_{fume}$ = flow rate of fume hood.

We must maintain a hydrogen pressure of 5 PSI as per our storage container’s specifications. We can perform partial differentiation on the Van der Waals equation to get a clean expression for the change in pressure in our storage container. This allows us to calculate how long we need to attach the pump to our generator to obtain the proper pressure and moles of hydrogen in the cylinder.

$$ ∂P = \left(\frac{RTV}{(V - nb)^2} - \frac{2na}{V^2}\right) \times ∂n $$

where $T$ is the surrounding temperature, $V$ is the volume of our storage container, $n$ is the mols of hydrogen in the storage container, $a$ and $b$ are the Van der Waals coefficients, and $∂n$ is the rate of hydrogen production.

The container that we intend to use to store and pump hydrogen on the car is made out of steel because steel does not react with hydrogen.

Conclusion

Fuel cells are particularly praised for their ability to provide sustainable energy. The only waste product in the reaction is water, making it an environmentally-friendly zero emission panacea. Given the global energy crisis that we are in and our dependence on nonrenewable energy sources to produce fuel, fuel cell technology has been embraced by scientists and engineers as an alternative means of energy production. They are quieter and more efficient than combustion engines. All of these advantages have encouraged automobile companies like Toyota, Hyundai, and even Mercedes to manufacture their own fuel cell vehicles. The fuel cell company Ballard is providing their fuel cells to power buses in China.

Who knew that this little magic box known as the hydrogen fuel cell would change transportation for the years to come? Our mission as young and enthusiastic chemical engineering students is to prove that Hydrogen Fuel Cells are a viable solution to counteract problems such as air pollution and climate change.

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