The two leading electric vehicle technologies today are hydrogen fuel cells and lithium-ion batteries.
Although they are trying to achieve the same goal, they are approaching it in quite different manners.
Auto manufacturers are on the fence about which one to pursue, and brands including Toyota, BMW, Land Rover, and Mercedes-Benz are investing in both these technologies.
South Africa also leans more towards the hydrogen fuel cell side at the moment, with a “hydrogen freeway” in the works.
Companies such as VW and Tesla, however, are primarily focussed on battery-powered cars, SUVs, and trucks.
Below, we take a closer look at the benefits and drawbacks of these two propulsion methods.
How they work
“Green” Hydrogen, the type mostly used in powering vehicles, is made from electrolysis and water.
A strong electrical current is passed through water by means of electrodes (power-conducting rods), and this causes a chemical reaction where the water splits into hydrogen and oxygen.
The hydrogen is then stored in a tank to later be transferred to a “fuel cell”.
Inside this cell, an anode and a cathode are sandwiched around a central electrolyte.
Hydrogen is fed to the anode while air is sent to the cathode. The pressurised hydrogen molecules then split into protons and electrons when they come into contact with a platinum catalyst.
Lithium-ion (Li-ion) batteries also work with an anode, a cathode, and an electrolyte – but rather than generating power while driving, they discharge stored power.
The electrolyte sits between the anode and cathode, and the latter is able to store the energy fed into it by an electrical outlet.
When charging, the electrical current from a plug is channeled into the cathode, which sends the lithium ions to the anode.
When driving, the process reverses, and the charged anode sends the lithium ions back through the electrolyte towards the cathode – which creates an electrical current.
The main benefit of hydrogen fuel cells is that they are as convenient to use for the end consumer as “normal” fuel. Owners can fill up their vehicle’s hydrogen cells at hydrogen stations using a pump.
Hydrogen also has a greater energy to weight ratio than Li-ion batteries, meaning it offers long driving ranges while weighing much less than a battery would.
Another argument for the use of hydrogen fuel cells is that you only need hydrogen and oxygen for inputs – which are two abundant elements.
The only outputs from a vehicle are heat, electricity, and water – leaving no adverse environmental impact.
Li-ion technology also has its fair share of benefits, with a leading one being its huge market share compared to hydrogen fuel cells.
The Li-ion battery is a relatively mature technology which is already safely implemented in dozens of countries and vehicle ranges around the world.
Due to this mass-market integration it is cheaper to produce, with the required infrastructure to support living with an Li-ion-powered being very accessible.
A vehicle fitted with a Li-ion drivetrain also has fewer moving parts than the alternatives, leading to less maintenance and service-related costs.
VW is a great proponent for Li-ion technology, stating that it is the most efficient way of powering a vehicle across the current available methods – with a minimum 70% efficiency rate during production.
Both of these technologies therefore have the ability to be carbon-neutral, and both ultimately drive electric motors.
What makes hydrogen difficult to use for vehicles is that it easily bonds with other elements.
It therefore needs to be kept at freezing temperatures, meaning storage is difficult.
VW also claims that hydrogen generation is less efficient than Li-ion batteries, as around 70% of the energy is lost during the development process.
Lower efficiency leads to a higher overall production cost, and can cause a negative environmental impact depending on the sources of electricity used.
For comparison, current fossil fuels only achieve a 20% efficiency rate, said VW.
Looking at Li-ion vehicles, their biggest negative is their charging times – as you will need to wait for a few hours for the battery to fill up using a standard plug at home.
A shared drawback for both these technologies is crash safety, too.
Li-ion batteries are enclosed in a case to protect them from impacts. In the event of a crash, Li-ion vehicles have been known to spontaneously catch fire for days after the incident – as heat travels from one cell to the other inside the battery.
Hydrogen is also extremely flammable, but not more so than fossil fuels. Manufacturers of these vehicles also protect the hydrogen tanks with special materials to guard against impacts.
For example: The tank in the Toyota Mirai is wrapped in carbon fibre, and able to withstand a .50 caliber bullet, said the company.
These processes inevitably add weight and costs to the end product in both cases.