Fuel cell development program for electric vehicle The Hong Kong Polytechnic University EE4006A Individual Project Fuel cell development program for electric vehicle Name: CHIM Kwan Kit Student ID: 13029367d Supervisor: Dr. K. W. Cheng Department: Electrical Engineering

Content Introduction Objectives Methodologies Results Conclusion Al-air battery Boost-converter PWM Regenerating system Results Conclusion

Introduction Hybrid and electric vehicle are the trend Many vehicles companies are starting to analyze hybrid and electric vehicles (e.g. Phinergy, Toyota) The environmental batteries used now are AlO and ZnO The project included Power processing Energy conversion Battery analyzing

Objectives Primary goals: Find a control method to control power processing Find a optimization of the battery Apply on electric vehicles successfully Secondary goals: Have a contribution to the environmental work Encourage people to start using electric vehicles

Methodologies- Board diagram

Methodologies- Al-air battery Characteristic of Aluminum-air battery High energy density (8kWh/kg) High power and service hour Non-rechargeable

Methodologies- Al-air battery The electrochemistry of aluminum-air battery Anode: Al + 3OH− → Al(OH)3 + 3e− -2.3 V Cathode: O2 + 2H2O + 4e− → 4OH− +0.40 V Total reaction: 4Al + 3O2 + 6H2O → 4Al(OH)3 + 2.71 V

Methodologies- Al-air battery Some factors affecting battery performance Voltage level Current drain of discharge Temperature of battery during discharge Different material and concentration of electrolyte Service life

Methodologies- Al-air battery Producing an Al-air battery Carbon electrode part Cut the barbed wire to the shape that fits the size of the plastic case Wrap the barbed wire around iron mesh to give a better contact with the carbon Separate large activated carbon by using sieving Shake carbon granules to uniform layer Mix epoxy glue Add carbon granules into the glue and stir Strew and smear the mixture Shake carbon granules to both sides in order to make sure the electrode full of carbon Put the electrode under high pressure Make sure the electrode is low resistance in order to reduce loss

Methodologies- Al-air battery Producing an Al-air battery Battery part Make two carbon electrodes from the previous procedure Place the carbon electrodes together with the aluminum foil at the middle into the plastic case Use the butter paper to separate the electrode and the aluminum foil Test by using multi-meter (check the resistance) that there is no short circuit between the electrode and aluminum foil Use measuring bottle to make certain volume of solution Add the solution into the plastic case Test the no load voltage and current to make sure the battery is work.

Methodologies- Boost converter The reasons using boost converter: High output voltage Fast transient response High efficiency Economical

Methodologies- Boost converter The input/output voltage ratio: Vin(DTs) = (Vo – Vin)(1 – D)Ts 𝑉𝑜/𝑉𝑖𝑛 = 1/1−𝐷 (𝑉𝑜 > 𝑉𝑖𝑛) Power relationship: VinIin = VoIo

Methodologies- Boost converter Design of boost converter

Methodologies- Pulse-width modulation (PWM) Function of PWM Encoding message into a pulsing signal Controlling the voltage supply to electrical devices Advantages of PWM Low switching power loss Little heat whilst working Efficiency up to 90%

Methodologies- Pulse-width modulation (PWM) Design of PWM

Methodologies- Pulse-width modulation (PWM) NE555 is used Frequency = 1.44 / ( RA + 2RB ) C Output driver duty cycle = tL / ( tH + tL ) = RB / RA + 2RB Output wave form duty cycle = tH / ( tH + tL ) = 1 - RB / RA + 2RB Low to high ratio = tL /tH = RB / RA + RB RA = 1k + 20kΩ, where 20kΩ is a variable resistor. RB = 6.2kΩ

Methodologies- Regenerative braking A regenerative brake is an energy recovery mechanism When the car is on load or braking, the motor would act like a generator to generate reverse energy flow in backward direction. Advantage of regenerative braking Increase efficiency of the system

Results- Al-air battery

Results- Al-air battery

Results- Al-air battery

Results- Al-air battery Aluminum foil in 5M NaOH solution Aluminum foil in 2M NaOH solution

Results- Al-air battery

Results- Al-air battery

Results

Results Duty cycle of the 17.1% Duty cycle of 25.6%

Results- Regenerative braking

Conclusion Al-air battery The solution using KOH is better than using NaOH with higher power generated Voltage and current generated would be increased when the concentration increased The lifetime of the battery is based on the aluminum corrosion rate Different connection can affect the performance of the battery The numbers of the carbon electrodes affects the amount of the current

Conclusion Boost converter and PWM Regenerative braking output voltage > input voltage Duty ratio is changed by the variable resistor PWM plays the role of controller Output voltage affects the speed of the motor Regenerative braking A capacitor is used to store the energy one more MOSFET has to be used