Hydrogen Car by Riversimple

Figure 1: Riversimple hydrogen car, The Rasa, prototype, with the four key areas of research indicated [1, modified]

Team 6l: Hydrogen Car Presentation Video https://mediaspace.carleton.ca/media/CCDP2100I+-+Team6A+Presentation+of+Findings/1_g6ybd9si  

Hydrogen Fuel Cell: Hannah Vu

Figure 2: A hydrogen fuel cell taking in hydrogen and oxygen molecules to produce electricity and water [2]

While traditional cars run on diesel or gasoline, hydrogen cars use hydrogen gas as a cleaner alternative fuel to power the electric motor of the car, hence eliminating the production of CO2​ pollutants. The hydrogen fuel cell that is found in a hydrogen car replaces what would normally be the engine of the automobile and is able to convert hydrogen into energy through a series of reduction–oxidation (redox) reactions. That said, when hydrogen gas is supplied, a chemical reaction involving the exchange of broken-down protons and electrons from hydrogen occurs inside the fuel cell. The flow of electrons is forced through an external circuit to generate the electricity needed to drive the motor. Compared to the toxic carbon emissions of conventional vehicles, this process only releases water and heat back into the atmosphere. 

In-Wheel Electric Motors as Brakes: Maheen Moazzam

Figure 3: Energy flow between the in-wheel electric motors​ ​, supercapacitor​ ​, and fuel cell​ ​ within a hydrogen car [1, Maheen Moazzam]

Incorporating in-wheel electric motors as brakes into hydrogen cars is important because this mechanism allows the car to convert energy, in order to store and reuse it. In Riversimple’s hydrogen car, there are four in-wheel electric motors, one on every wheel. Energy flows from the hydrogen fuel cell into the in-wheel motors, producing kinetic energy, which allows the car to accelerate. In traditional cars, when brakes are normally applied to slow down the vehicle, the kinetic energy used is transformed into heat, due to friction, and is essentially wasted. To be more energy–efficient, Riversimple has incorporated a brake function within the wheel systems of the in-wheel electric motors in their hydrogen cars. This brake function relies on the energy conversion theory, and allows for the recovery of over 50% of the kinetic energy from breaking, that would otherwise be lost as heat, and converts it into electric energy that can be stored and reused. 

Super-Capacitors: Lakshana Namasivayam     

Figure 4: Super-capacitor used in a hydrogen car for acceleration [3, modified]

Gas and electric vehicles typically use batteries to provide enough power for acceleration, but hydrogen cars have created an efficient method using super-capacitors instead. While hydrogen fuel cells provide energy for the hydrogen car to move, it does not provide enough energy for acceleration. Energy that is typically wasted from the brakes is conserved and stored into the super-capacitor in order to be released alongside fuel cells for acceleration.

Super-capacitors are a powerful version of capacitors and have the ability to store energy using double-layer capacitance. When energy in the form of current flows into the supercapacitor, its insulating layer attracts ions and separates the positive and negatively charged ions on both sides of the layer. This attraction creates and stores double layers of charge into the super-capacitor, and this process is what is called double-layer capacitance.

Lightweight Composite Monocoque: Rayah Aboukarr 

Figure 5: Monocoque structure of Riversimple’s Rasa [4]

A composite material is made from the fibres of a material that are woven into a sheet, for example carbon fibres. To create solid products from carbon fibre, the sheets are submerged in a glue and stacked until a certain thickness is reached. Carbon fibre materials can have a lighter weight than steel and a greater strength. A way to reduce the weight of a vehicle is by replacing the steel frame of the vehicle with a carbon fibre monocoque. A monocoque is a single shell frame that is used in the structure of vehicles. 

Specific power is a concept where the power outputted by a vehicle’s engine is divided by the mass of the vehicle. This is a way to measure the efficiency of a vehicle. The higher the specific power the more efficient a vehicle is. By using a carbon fibre monocoque rather than a steel frame, not only is the power required by the vehicle reduced, but the vehicle can also output more power when moving because there is more power applied for each kg of mass.

References

[1] Riversimple, “The Design of the Rasa,” The Design of the Rasa​, 23-Aug-2017.​     [Online]. Available: https://www.riversimple.com/the-design-of-the-rasa​/.​ ​ [Accessed: 24-Nov-2020]. 

[2] C. Anderson, “Fuel Cells: Stationary Power,” Medium​​, 23-Sep-2020. [Online]. Available: https://medium.com/prime-movers-lab/fuel-cells-everything-else-bbbad62333f9.​ [Accessed: 25-Nov-2020].  

[3] H. Zhao and A. F. Burke, “Fuel Cell Powered Vehicles Using Supercapacitors-Device Characteristics, Control Strategies, and Simulation Results,” Fuel Cells​      ​, vol. 10, no. 5, pp. 879–896, Oct. 2010. [Online]. Available doi:10.1002​       /fuce.200900214. [Accessed: Sept. 28, 2020].

[4] Riversimple, “Structure of the Rasa,” ‘CAD Build’ of the Rasa, 2020. [Online]. Available: https://s3.eu-central-1.amazonaws.com/riversimple1405/index.htm​l.​ [Accessed: 24-Nov-2020].