Fuel cell powered vehicle model

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

Ans:-

Fuel 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.

The first fuel cells were invented by Sir William Grove in 1838. The first commercial use of fuel cells came more than a century later following the invention of the hydrogen–oxygen fuel cell by Francis Thomas Bacon in 1932. The alkaline fuel cell, also known as the Bacon fuel cell after its inventor, has been used in NASA space programs since the mid-1960s to generate power for satellites and space capsules. Since then, fuel cells have been used in many other applications. Fuel cells are used for primary and backup power for commercial, industrial and residential buildings and in remote or inaccessible areas. They are also used to power fuel cell vehicles, including forklifts, automobiles, buses, boats, motorcycles and submarines.

Use of Fuel Cell in EV:-

FCEVs use a propulsion system similar to that of electric vehicles, where energy stored as hydrogen is converted to electricity by the fuel cell. Unlike conventional internal combustion engine vehicles, these vehicles produce no harmful tailpipe emissions. Other benefits include increasing U.S. energy security and strengthening the economy.

FCEVs are fueled with pure hydrogen gas stored in a tank on the vehicle. Similar to conventional internal combustion engine vehicles, they can fuel in less than 4 minutes and have a driving range over 300 miles. FCEVs are equipped with other advanced technologies to increase efficiency, such as regenerative braking systems, which capture the energy lost during braking and store it in a battery. Major automobile manufacturers are offering a limited but growing number of production FCEVs to the public in certain markets, in sync with what the developing infrastructure can support.

Fuel Cell Model in SIMULINK:-

In this Assignment, we are simulating pre-loaded model of Fuel Cell in SIMULINK. To open this model use “power_fuel_cell” in command prompt.

The nominal Fuel Cell Stack voltage is 45Vdc and the nominal power is 6kW. The converter is loaded by an RL element of 6kW with a time constant of 1 sec. During the first 10 secs, the utilization of the hydrogen is constant to the nominal value (Uf_H2 = 99.56%) using a fuel flow rate regulator. After 10 secs, the flow rate regulator is bypassed and the rate of fuel is increased to the maximum value of 85 lpm in order to observe the variation in the stack voltage. That will affect the stack efficiency, the fuel consumption and the air consumption.

Fuel cell voltage, current, DC/DC converter voltage and DC/DC converter current signals are available on the Scope2. Fuel flow rate, Hydrogen and oxygen utilization, fuel and air consumption, and efficiency are available on the Scope1.

Block Explanation:-

• Fuel Cell:- The Fuel Cell Stack block implements a generic model parameterized to represent most popular types of fuel cell stacks fed with hydrogen and air.

The block represents two versions of the stack model: a simplified model and a detailed model.

The nominal Fuel Cell Stack voltage is 45Vdc and the nominal power is 6kW. The converter is loaded by an RL element of 6kW with a time constant of 1 sec. During the first 10 secs, the utilization of the hydrogen is constant to the nominal value (Uf_H2 = 99.56%) using a fuel flow rate regulator. After 10 secs, the flow rate regulator is bypassed and the rate of fuel is increased to the maximum value of 85 lpm in order to observe the variation in the stack voltage. That will affect the stack efficiency, the fuel consumption and the air consumption.

Fuel cell voltage, current, DC/DC converter voltage and DC/DC converter current signals are available on the Scope2. Fuel flow rate, Hydrogen and oxygen utilization, fuel and air consumption, and efficiency are available on the Scope1.

Block Explanation:-

• Fuel Cell:- The Fuel Cell Stack block implements a generic model parameterized to represent most popular types of fuel cell stacks fed with hydrogen and air.

The block represents two versions of the stack model: a simplified model and a detailed model.

In this model we are using Preset Model of PEMFC-6Kw-45Vdc.

Flow Rate regulator:-

This block is flow rate regulator, which take input from output current and fed as feedback to the controller, Flow rate selector .

In this block there is a Math equation block by which the relation between output and input flow rate is instablisherd

Equation:- `(60000*8.3145*(273+T)*Nc*u(1))/(2*96485*(Pf*101325)*Uf_H2/100*x/100)`

Flow Rate Regulator:-

The circuit have a clock which output the current simulation time A compare to constant block is setted up, which let the signal start after 10 seconds as it is usinf >10 operator and pass it to the Edge Detector which detect the change of 10. Now the signal goes into Sample and Hold block where the holds it and pass it according to the values. Here circuit have 2(Fr_reg_in) for input, if it does not satisfy, then will go into 3(Fr_reg_out).

100 VDC BOOST CONVERTER:-

This is DC-DC Boost converter which boost the voltage level of Fuel Cell to match with the load requirement.. In this block there is one chopper circuit, one practical capacitor is present, and according with the output Duty cycle of chopper is set.

OUTPUT:-

Simulation Time:- 20 Sec

At t=0 s, the DC/DC converter applies 100Vdc to the RL 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 ow rate is automatically set in order to maintain the nominal fuel utilization. Observe the DC bus voltage scope-2 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.

At t=10s, the fuel ow rate is increased from 50 liters per minute to 95lpm during 3.5s reducing by doing so the hydrogen utilization. This caused an increasing of the Nearest voltage so the fuel cell current will decrease. Therefore, the stack consumption and the efficiency will decrease scope-1.

1. FLOW RATE(lpm): Upto 10 Sec the flow rate is increasing and remains constant, until it reaches 50 lpm. After 10sec. of the time. The flow rate increases up to 95lpm which is attained in 3.5 sec.
2. UTILIZATION (%): As Flow rate is increased to 95lpm, there is reduction in the utilization of Hydrogen 100% to 42%. Whereas, Oxygen remains constant with value of 60%.
3. STACK CONSUMPTION (lpm): We can see in the plot that, up to 10 sec. the oxygen and hydrogen consumption gradually increase and remains constant up to 10 sec. again after 10 sec. the hydrogen and oxygen consumption decreases and remains constant.
4. STACK EFFICIENCY (%): At time t = 0 due to transient state the efficiency 1st increases and then decreases and remains constant, with the constant stack consumption. Efficiency again, decreases and remains constant after 10 sec

Scope 2:- This scope represents the voltage and current behavior of Fuel cell stack.

As we can see the voltage value is decreased up to the 10 sec, but flow rate is increase after the 10 sec, hence the voltage value is increase, and to compensate this, the current value of fuel cell is decreases.