Learn more about the various technologies used in Toyota's fuel cell vehicles

Fuel cell stacks

Fuel cells generate electricity through a chemical reaction between hydrogen and oxygen. Hydrogen and ambient air are respectively supplied to the anode (negative electrode) and the cathode (positive electrode) of fuel cells to generate electricity.

Fuel cells consist of MEAs (membrane electrode assemblies) sandwiched between separators. An MEA is a solid polymer electrolyte membrane with catalyst layers applied. Since one cell can only yield less than one volt, several hundred cells are connected in a series to increase the voltage. This combined body of cells is called a fuel cell stack.

How electricity is generated from hydrogen and oxygen in a fuel cell
1. Hydrogen is supplied to the anode side.
2. Hydrogen molecules activated by the anode catalyst release their electrons.
3. The released electrons travel from the anode to the cathode, creating an electrical current.
4. The hydrogen molecules that release electrons become hydrogen ions and move through the polymer electrolyte membrane to the cathode side.
5. The hydrogen ions bond with airborne oxygen and electrons on the cathode catalyst to form water.

Here are some of the key specifications of Toyota's proprietary FC Stack.

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FC boost converter

By developing a high-capacity FC boost converter, it was possible to increase the voltage of the drive motor, reduce the number of fuel cells, and reduce the weight and volume of the system on board the Mirai.
In addition, the new system can be used with existing hybrid units, enhancing reliability and greatly reducing costs.
Innovations to voltage boost control and case structure also provide exceptionally quiet operation.

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Drive battery

The drive battery is rechargeable, storing energy recovered by the motor during deceleration. The "Mirai" is equipped with a nickel-metal hydride battery which stores energy recovered during deceleration, and then adds to the output of the fuel cells during acceleration.

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A Toyota-developed AC synchronous motor/generator is used in the Mirai. It functions as a generator under deceleration to regenerate energy.

Max. power output: 113 kW (154 PS)
Max. torque: 335 N·m (34.2 kgf·m)

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Power control unit

The power control unit in the Mirai consists of an inverter that converts DC into AC to power the motor and a DC/DC converter that draws current from and recharges the drive battery, among other systems. It exercises precise control over fuel cell power output and drive battery discharging and recharging under all driving conditions.

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High-pressure hydrogen tanks

The Mirai is equipped with in-house developed 70 MPa high-pressure hydrogen tanks. The new 70 MPa tanks have three layers; a plastic liner a plastic liner to retain pressurized hydrogen (the innermost layer of the tank), a carbon fiber reinforced plastic layer, and a glass fiber reinforced plastic layer to protect the surface. The structure of the carbon fiber reinforced plastic layer has been innovatively lightened, giving it world-leading* tank storage performance.

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