Week 8 Challenge

# AIM

Complete the Ultracapacitor model and the model output should give, current, SOC and Voltage as output.

# THEORY

* Ultracapacitor

An Ultracapacitor also known as a supercapacitor or electrochemical capacitor is a device for storing electrical energy which is growing rapidly in popularity The design and mechanism of operation are somewhat between an ordinary capacitor and a battery which opens up some interesting and valuable applications

Like a battery a single ultracapacitor cell consists of a positive and negative electrode separated by an electrolyte However ultracapacitor stores energy electrostatically like e regular capacitor not chemically like a battery there is a dielectric separator dividing the electrolyte also like a capacitor

The small separation between electrodes permitted by this structure leads to a much higher energy density than a normal capacitor whilst an ultracapacitor stores less energy than an equivalently sized battery it can release it much quicker as the discharge is not dependent on a chemical reaction taking place

Because no physical or chemical changes occur when the charge is stored ultracapacitors can also be used many times over without degradation

* Equations used in the model

Three equations in the UC model are defined first which gives us SOC, current, and OCV.

These are the three parameters that influence UC.

• OCV defines the SoC of Ultracapacitor.
• Max Voltage or Voltage is directly proportional to the charge stored in the battery.
• The amount of charge is directly proportional to the current that can flow in the circuit.

Where

• eta is the Coulomb efficiency.
• Q is the electric quantity or charge on UC.
• I is the current.

• Q depends on capacitance which is the charge storage capacity measured in Farads.
• The OCV is a measure of the electric field between plates.

• Capacitance and OCV give 'Q'
• The integration of current over 'C' gives 'OCV'.
• In the UC model calculations for current and SoC are done as said below:
• Firstly the current consumed is calculated which is fed into an SOC calculation block.
• The SoC is then calculated based on the amount of current drawn and pushed back into the UC.

Hence formula for current is given as:

Where

• R is the lumped resistance
• Vmax is the max. voltage
• eta is the efficiency during the charge-discharge cycle.
• PUC is the power demand which is to be supplied by UC and it is the first input in this model which basically comes from Energy management systems.

# SIMULATION

Case 1: Input from constant block

• PUC is our input here which is nothing but the Power demand for the UC. 20K watts is the value.
• A complete Fuel cell or electric vehicle model comes from the EMS (Energy management system) block.
• This input goes inside the Current calculation block. With that inside of the Current calculation, the block is shown.

* Implementation of the Current formula

* SOC is needed in the current calculation, so the SOC block does that and its implementation is shown below:

• If you see current and SOC calculation blocks are interconnected then both take each other's quantity in their value calculation.
• The more the current is drawn the lower the SOC is going to get.
• Initial SoC has been set to 1 which basically means that we are going to drain the Ultracapacitor.

* Apart from current, the second input to the SOC block is charge Q.

* With the help of calculated current we can calculate the OCV.

* To find the voltage of the UC we need current and SOC as our input which helps us to find UC voltage.

Case 2: Here input is given from a signal builder for 598seconds

Parameters value:

• C=100
• R=0.064
• eff=0.9
• SoC initial=1
• V_max=300

# SIMULATION RESULT

Case 1

Case 2

• From the above plots, it is observed that when there is a sudden peak load power demand of above 200kW is required. It can be met by the met by ultracapacitor without any tension. It can also be charged quickly to a particular value with less amount of power of less than 50kW.
• It can also be able to meet sudden peaks three to four times the normal. For example, if the electric vehicle’s normal load is less than 100kW and only the peak load is about 600kW. Then only by going with battery to meet this demand. The battery pack has to be designed for 600kW. The cost of the vehicle is rapidly increased. Because only for a short period of time only peak load occurs. For that short duration of time, it is unnecessary to increase the battery pack which increases the cost and weight of the vehicle.
• Let us consider going on designing only with fuel cell. The fuel cell has the operating range in the polarization cure. If the fuel cell vehicle is operated above or below that operating then the efficiency of the vehicle is very poor. In order to overcome these shortcomings, the ultracapacitor is used. It can be able deliver a sudden peak load which can be three to four times the normal load. So the 100kW load can be met by battery and 600W or more peak load can be met by ultracapacitor.

# CONCLUSION

Completed the Ultracapacitor model