While expert opinion varies regarding the evolution of transport, there is one aspect on which there is convergence: electric vehicles of all types lie at the heart of future sustainable transport systems.
There are two main reasons underlying this consensus. With transport-related greenhouse gas emissions growing faster than any other energy end-use sector, an integrated electro-mobility ecosystem is vital to limit the global temperature increase. Secondly, electric vehicles produce no harmful tailpipe emissions and therefore have a hugely beneficial impact on local air quality.
The media sometimes gives the impression that an “electric vehicle” is a car with a lithium ion battery. But this is only part of the story. Electric cars include battery electric vehicles (BEVs) but also plug-in hybrid electric vehicles (PHEVs), and fuel-cell electric vehicles (FCEVs). While PHEVs use a combination of an internal combustion engine and a battery electric drive system, BEVs and FCEVs are, quite simply, all-electric vehicles with the potential to bring tailpipe-related emissions down to zero.
Like BEVs, FCEVs use a completely different powertrain system to conventional vehicles.
Both use electricity to power an electric traction engine, they emit no tailpipe pollutants and have many similar components associated with an electric drivetrain.
The main differing feature is the way in which electric power is obtained. BEVs use a battery to store electrical energy, which is recharged by plugging the vehicle into a power source. While FCEVs use hydrogen from an onboard fuel tank, along with oxygen from ambient air, to generate electricity.
This crucial distinction makes a major difference to drivers.
Fully charging an FCEV takes a matter of minutes at a refueling station, whereas BEV owners typically require access to overnight charging facilities.
The latter is not an option for everyone as this usually necessitates owning a private garage or driveway for charging. A second major difference is range. FCEVs typically have longer driving ranges than BEVs, reaching distances similar to those of gasoline cars.
A fuel cell generates electricity by combining hydrogen with oxygen. Hydrogen is supplied to an anode where hydrogen molecules release electrons, which travel towards the fuel cell’s cathode creating an electrical current that is directed toward an electric motor. The hydrogen cations move through a polymer electrolyte membrane towards the cathode where ambient air is supplied. They bond with oxygen and electrons on the cathode catalyst, forming pure water and heat in the process — the only byproducts.
The inherent similarity of the battery and fuel cell technologies is underlined here: both involve electrodes, electrolytes, and the production of electrons to drive an electric motor. In a fuel cell the reactants are stored externally (hydrogen in the vehicle’s storage tank and ambient air) and the electrodes have a catalytic role in the conversion.
A fuel cell will create a current for as long as the reactants are supplied.
Whereas for BEVs, the reactants are contained within the battery where chemical reactions allow the release of electrons. Recharging reverses these reactions, enabling energy to be stored again.
Fuel cell technology has advanced exponentially in recent years, helping to accelerate the growing interest in FCEVs. While the potential for hydrogen power as a green energy solution has been well understood for decades, there have been bottlenecks to its mass adoption, which can be grouped into two categories: technological and infrastructural.
Today, commercially available FCEVs such as Hyundai’s ix35, Toyota’s Mirai, and Honda Clarity which were put into production in 2013, 2015 and 2016 respectively, demonstrate that the technological barriers to the use of hydrogen in transport have been consigned to history. The US Department of Energy, just one of the key players working to overcome these challenges to commercialization, recently published a summary of its research that illustrate the scale of the advances. It achieved a 50% reduction in high volume automotive fuel cell costs since 2007 (including a five fold reduction in the platinum content of fuel cell catalysts, along with the development of durable membrane electrode assemblies); and a quadrupling of fuel cell durability since 2006.
Not only have these barriers been effectively tackled, the latest scientific research suggests we are on the cusp of even greater reductions in terms of fuel cell costs. One recent breakthrough was the discovery that the insertion of atom-sized holes into the platinum catalyst surface hugely increases efficiency. The new catalyst design could be up to three times as active, which means the amount of platinum could be reduced accordingly. The figures are striking: instead of 30–40 grams, only 10–15 grams of platinum would be required, which is close to the amount needed for a conventional car.
Other researchers are designing new fuel cells with the aim of replacing platinum altogether. New catalysts known as “molecular catalysts”, which combine much less expensive non-metal molecules (nitroxyls and nitrogen oxides), have an efficiency approaching that of platinum.
The second category of bottlenecks, infrastructural issues, is sometimes referred to as a chicken-and-egg conundrum: manufacturers cannot sell high volumes of hydrogen FCEVs if customers do not have access to sufficient infrastructure to keep their cars up and running; while potential hydrogen fuel providers are understandably reluctant to build more stations without sufficient numbers of FCEVs on the road.
Breaking the status quo required one side to make the first move.
And with giant automotive manufactures like Toyota and Hyundai going ahead with commercial FCEV production, the ball was firmly in the court of the hydrogen infrastructure pioneers. Today, government and industry initiatives are opening the floodgates for FCEVs all over the world.
For example, the company H2 Mobility has announced plans to install up to 400 hydrogen refueling stations in Germany by 2023 to establish a nationwide supply network. In the UK, the government has announced an £11 million fund to help prepare the country for the roll-out of hydrogen FCEVs.
In Japan, where Prime minister Shinzo Abe has pledged to make the nation a “hydrogen society”, the Ministry of Economy, Trade and Industry aims to double the number of hydrogen stations to about 160 by 2021, and then 320 in the following five years (to support a target of 40,000 hydrogen-powered cars by 2020, and 800,000 by 2030).
In the US, H2USA and the Department of Energy have launched the Hydrogen Refueling Stations Analysis Model and the Hydrogen Financial Analysis Tool to address key technical and financial barriers to hydrogen fueling infrastructure deployment, and in California specifically, Assembly Bill 8 dedicates up to $20 million a year to support the continued construction of the state’s hydrogen fueling station network.
Based on electric traction engines, producing no tailpipe pollutants, and with the potential to slash carbon emissions, FCEVs are all-electric vehicles, as much as BEVs. Both look certain to play a pivotal role in clean and green mobility in future. And it looks like the technological achievements now being made are about to give a further boost to the commercial viability of FCEVs. The future for the electric powertrain is surely bright.