Week 6 Fuel cell powered vehicle model

- Aim: Make a MATLAB model of fuel cell powered electric vehicle and comment on results

Full cell:

- A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent(often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from metals and their ions or oxides that are commonly already present in the battery, except in flow batteries. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied.

- Fuel cells cleanly and efficiently convert chemical energy from hydrogen-rich fuels into electrical power and high-quality heat via an electrochemical process that is efficient and emits water rather than pollutants as there is no burning of the fuel.

- Fuel cells work like batteries, but they do not run down or need recharging. They produce electricity and heat as long as fuel is supplied. A fuel cell consists of two electrodes—a negative electrode (or anode) and a positive electrode (or cathode)—sandwiched around an electrolyte. A fuel, such as a hydrogen, is fed to the anode, and air is fed to the cathode. In a hydrogen fuel cell, a catalyst at the anode separates hydrogen molecules into protons and electrons, which take different paths to the cathode. The electrons go through an external circuit, creating a flow of electricity. The protons migrate through the electrolyte to the cathode, where they unite with oxygen and the electrons to produce water and heat. 

-  Although automakers could design an FCEV with plug-in capabilities to charge the battery, most FCEVs today use the battery for recapturing braking energy, providing extra power during short acceleration events and to smooth out the power delivered from the fuel cell with the option to idle or turn off the fuel cell during low power needs. 

- The figure above shows the reactions occurring while working on the fuel cell. It can be seen that when the fuel is supplied at the anode or positive electrode, where electrons are released from fuel under catalyst. The positive electrons pass through the electrolyte where are negative once passes through the external circuit and perform the work.

- On the other side, as there is a continuous flow of oxygen these hydrogen atoms combine with the oxygen and form water ( H2O ), and this water comes as an exhaust. There are no exhaust gases in this case.

Anode --> `H2 -> 2H^+ + 2e^-`

Cathod --> `2e^- + 2H^+ + 1/2O2 -> H2O`

Cell --> `H2 + 1/2O2 -> H2O`

- In the below images input parameters can be seen. First of all, the ramp block as an input is used which has the input values as shown. 

- As per the requirement the preset model is taken as 50 KW and 625Vdc. All the other input parameters are taken as it is. The necessary parameters are also mentioned in the block. There are number of different model parameters available however, the OEm is always recommended as that is the most standard model currently used.

- From the below chart the behaviour of current and voltage, and, current and power can be seen.

- The following graphs shows the fuel flow rate, H2 and O2 utilization percent, stack consumption and overall efficiency. 

- The plots below shows the voltage and current behaviour.  From the plot it can be seen that, as the voltage increases the current  value changes accordingly. The moment the voltage shifs suddenly, there is a slight change in bus voltage which increases for short period of time and again comes to its original value.

Reference:

- https://afdc.energy.gov/vehicles/how-do-fuel-cell-electric-cars-work

- https://www.fuelcellenergy.com/benefits/how-a-fuel-cell-works/