Toyota has promised to launch a production hydrogen-electric fuel cell vehicle by 2015. But how does this ultimate eco-car technology work?
The revolution starts here… The countdown to the launch of Toyota’s advanced new fuel cell vehicle has finally begun.
On sale in 2015, the Toyota FCV been described as the nearest thing yet to the ultimate eco-car, and a key step in finding a solution to energy demands and emissions issues associated with traditional petrol and diesel engines.
But Toyota’s new fuel cell vehicle is much more than the realisation of cutting-edge science theory.
So how do fuel cell vehicles actually work?
A fuel cell converts fuel into electricity by forcing it to react with oxygen.
Hydrogen is the most common fuel used in today’s fuel cells, but almost any hydrocarbon, including gas and alcohol can be used. For more detail on this process, please see below.
Fuel cells require a constant supply of fuel and oxygen to sustain the electricity generating reaction; however, as long as fuel is supplied, the cells can produce electricity continuously.
It’s worth pointing out that the idea of fuel cells is nothing new… In fact the first examples were designed in the mid-1800s. However, it took more than 100 years for the idea to get off the ground – literally, as NASA refined their use for the Apollo Moon project.
This environmentally friendly and highly energy-efficient process of generating electricity in a fuel cell produces no tailpipe emissions, but lots of pure water – great news, if you are running one inside a spaceship.
Back on Earth the same things make fuel cell vehicles ideal for achieving sustainable mobility, which is why Toyota has been striving to make this technology widely available as soon as possible.
In road cars, the technology is still developing. At their core, fuel cell vehicles marry the output of the fuel cell with established hybrid battery technologies, like those developed for the Toyota Prius.
As the world-leader in hybrid vehicles, Toyota’s Hybrid Synergy Drive technology provides this foundation, with the hydrogen fuel cell replacing the internal combustion engine as the primary power source. An explanation of Hybrid Synergy Drive technology can be found by following this link.
That understood, it is now necessary to explain the functions of the two primary components used in a fuel cell vehicle.
The fuel cell generates electricity through a chemical reaction between hydrogen and oxygen. This is achieved by supplying hydrogen to the negative anode of the fuel cell and ambient air to the positive cathode.
A fuel cell consists of individual cells within a membrane electrode assembly (MEA) sandwiched between separators. The MEA consists of a polymer electrolyte membrane with positive and negative catalyst layers on either side. Each cell yields less than one volt of electricity, so several hundred cells are connected in series to increase the voltage. This combined body of cells is called a stack, which is commonly referred to as a fuel cell unit.
Though it is possible to use other elements in a fuel cell, the advantage of hydrogen is its high energy efficiency. Since electricity can be produced directly from hydrogen without combustion, it is possible to convert 83% of the energy within a hydrogen molecule into electricity. This is more than double the energy efficiency of a petrol-powered engine.
HIGH-PRESSURE HYDROGEN TANK
Hydrogen is stored in two high-pressure (70 MPa) tanks like the one pictured above. The innermost layer features a polyamide resin liner that has high strength and superb resistance to hydrogen permeation. This is necessary because the diameter of hydrogen molecules are the smallest known to science and tend to escape through inferior materials.
Further use of optimal materials has increased tank capacity (historically, most FCVs have needed four separate tanks to improve capacity and therefore cruising range) and reduced weight. This can be seen in the winding angle, tension, volume and wall thickness of the carbon fibre used in the outer shell.
HOW A HYDROGEN FUEL CELL GENERATES ELECTRICITY
* Hydrogen is supplied to the anode (negative) side of the fuel cell
* Hydrogen molecules activated by the anode catalyst release electrons
* The electrons travel from the anode to the cathode (positive) side of the fuel cell, creating an electrical current
* The hydrogen molecules that released the electrons become hydrogen ions and move through the polymer electrolyte membrane to the cathode side
* Hydrogen ions bond with ambient oxygen and electrons on the cathode catalyst to form water
* Electricity produced by the fuel cell is directed to an electric motor to deliver drive to the vehicle
* Regenerated energy is stored in a secondary battery that supplements power from the fuel cell by providing auxiliary power to the electric motor
THE TOYOTA FCV CONCEPT
Toyota’s research into fuel cell technology began in 1992 and the culmination of its development is seen in the practical FCV Concept, which made its public debut at the 2013 Tokyo Motor Show. Producing nothing but water as a by-product of converting hydrogen into electricity, the vehicle has a range of over 300 miles and is powerful enough to provide a Japanese home with more than a week’s worth of electricity.