Week 6 Fuel cell powered vehicle model
MATLAB model of Fuel Cell powered electric vehicle and results analysis
The basic principle of a Fuel Cell car is that, a fuel cell is used to produce an electro-chemical reaction. Hydrogen from the fuel tank and oxygen from the air combins, during the reaction electricity is produced. In a (PEM) Polymer Electrolyte Membrane fuel cell, an electrolyte membrane is sandwiched between a positive electrode (cathode) and a negative electrode (anode). Hydrogen is introduced to the anode, and oxygen (from air) is introduced to the cathode. The hydrogen molecules break apart into protons and electrons due to an electrochemical reaction in the fuel cell catalyst. Protons then travel through the membrane to the cathode. What makes it different from a battery is that a fuel cell only converts energy (hydrogen to electricity), without having also to store the energy within the cells.
In Fuel Cell Stack electrons are forced to make their way around to the cathode via an external circuit, and in doing so create the electric current which drives the car or charges the on-board battery. Once hydrogen reaches the other side of the membrane, it combines with oxygen - taken from the outside air - and creates water (H2O), which is expelled through the exhaust.
SimuLink model, configuration of Fuel Cell block
PEMFC choosen, The nominal Fuel Cell Stack voltage is 45Vdc and the nominal power is 6kW
DC/DC converter voltage in subsystems is loaded with 100dvc Boost
Completed SimuLink model of PEMFC applying 2 scopes, DC voltage, DC current, Fuel Cell Stack, ramp, Flow rate regulator, Flow rate selector, Step, DC/DC converter, series resistor and current signals
The Toyota Mirai uses the Toyota Fuel Cell System (TFCS) and offers both fuel cell technology. Another hydrogen car is the Honda Clarity Fuel Cell. The vehicle cover a distance of 650 km and a maximum speed of 165 km per hour, with 177 horsepower. Hydrogen-powered vehicles are lighter than battery-powered vehicles and have a more extended range. Also, hydrogen refueling takes just a few minutes compared to several hours for battery-powered cars. The voltage produced by fuel cells must be up to 600V. At low speeds, the car moves and obtains energy only from the battery. In contrast, at higher speeds, e.g., on a highway, the fuel cell brings extra power to the engines and, at the same time, recharges the battery.
Some other Fuel Cell vehicles on the market are:
Audi H Tron
BMW i Hydrogen Next
Hyundai NEXO
Riversimple Rasa
Results Analysis
The simulation is run with stop time as in drive cycle and the 2 scopes plotted the following resilts.
Scope 1
Fuel flow rate, Hydrogen and oxygen utilization, fuel and air consumption, and efficiency are available on the Scope1.
At time 10 seconds, the fuel flow rate is increased from 50 litres per minute (lpm) to 85 lpm
During 3.5 seconds reducing by doing so the hydrogen utilization. This causes an increasing of the Nernst voltage so the fuel cell current will decrease. The stack consumption and the efficiency decreases.
Scope 2
Fuel cell voltage, current, DC/DC converter voltage and DC/DC converter current signals are available on the Scope2
At start time on 0 seconds
The DC/DC converter applies 100Vdc boost to the series resistor load (the initial current of the load is 0A).
The fuel utilization is set to the nominal value of 99.56%. The current increases to the value of 133A.
The flow rate is automatically set in order to maintain the nominal fuel utilization. Observe the DC bus voltage which is very well regulated by the converter. The peak voltage of 122Vdc at the beginning of the simulation is caused by the transient state of the voltage regulator.