New Scientist 2018 sep

8 September 2018 | NewScientist | 21

an electric car’s battery. You can
also go further on a full tank of
hydrogen – about 500 kilometres,
compared with 300 kilometres
for a standard fully charged
battery (see table, below).
But although hydrogen reacts
cleanly – the only thing coming
out of the exhaust pipe is water –
hydrogen vehicles are more
energy-intensive than electric
ones if you factor in fuel
production and transport, says
Jake Whitehead at the University
of Queensland, Australia.
At the moment, most hydrogen
is extracted from natural gas –
a fossil fuel. “Green” hydrogen
can be made by splitting water
using solar or wind power,
but this involves multiple steps,
each using energy along the way.
In contrast, a single energy step
is required to directly recharge
a car battery at home.

Clean fuel?

If you account for this complete
energy cycle, Whitehead’s
modelling shows that hydrogen
vehicles require between 80 and
100 kilowatt-hours of electricity
to travel 100 kilometres, compared
with about 20 kilowatt-hours to
travel the same distance in a
battery vehicle. This is the main
charge levelled by Musk at
hydrogen cars. “[The efficiency is]
terrible, so why would you do
that? It make no sense,” he told
reporters at the Automotive News
World Congress in Detroit in 2015.
Hydrogen fuel is also more
expensive than petrol. Hydrogen
cars currently cost about 13 cents
per kilometre to run, compared
with 8 cents per kilometre for
petrol cars. However, some
projections suggest that the costs
will become equivalent by 2025
as the technology to produce
hydrogen becomes cheaper.
At the moment, there are only
about 6000 hydrogen vehicles
on the road globally, compared
with 2 million electric vehicles.
But Ogden says that hydrogen
vehicles may end up becoming

more popular among certain

drivers. “If you’re only using your

car for short commutes or to get

around the city, battery cars can

handle all your needs,” she says.

“But if you want a big car that

you can take on long drives in the

mountains on a whim, a hydrogen

fuel cell car might be better.”

The shorter refuelling time

and longer range of hydrogen

fuel cells also make them

appealing for taxis, buses and

long-haul trucks, says Dolan.

“These vehicles can’t afford to

be stopping for hours at a time

to recharge,” he says.

Hydrogen fuel cells are already

finding applications in these

heavy-use vehicles. Japan will

showcase 100 hydrogen buses

at the 2020 Tokyo Olympics, and

South Korea plans to introduce

1000 hydrogen buses by 2022.

A fleet of 180 hydrogen taxis,

private-hire and police cars

is being trialled in London,

Paris and Brussels, and retailer

Amazon has recently invested in

hydrogen-powered forklifts for

its warehouses. US manufacturer

Nikola Motors, meanwhile, says

it has received 11,000 pre-orders

for its hydrogen fuel cell truck.

Japan and South Korea are

leading this push because they

want to embrace zero-emissions

technology, but their combination

of small land masses and large

populations means they don’t

have enough solar, wind or other

renewable energy to support large

numbers of battery electric

vehicles, says Dolan.

They can’t import renewable

energy itself, but they can import

hydrogen made from renewable

energy in other countries.

Australia, for example, could use

its abundant solar energy to split

water and export hydrogen to

these countries, says Dolan.

“You can see hydrogen basically

as a carrier for renewable energy.”

Many people feel jittery

about hydrogen because of its

connection with hydrogen bombs

and the 1937 Hindenburg disaster,

in which a hydrogen-filled airship

spectacularly caught fire, killing

36 people. But the hydrogen tanks

used in modern fuel cell vehicles

are made from multiple layers of

resin, carbon fibre and fibreglass

that keep the flammable gas

safely contained. Tests show they

can even survive being shot

at or set on fire. New ways of

transporting hydrogen – like

in the form of ammonia – will

also make its deployment safer,

says Macleod.

The most probable future

scenario is that we will have a

mix of vehicles run by batteries,

hydrogen and petrol, each

performing different roles, says

Ogden. “There are proponents of

the different technologies saying

it’s all going to be all hydrogen

or all batteries, but auto-makers

are putting their money on both,”

she says. According to the KPMG

survey, car-makers are predicting

an even four-way split between

electric, hydrogen, petrol and

hybrid vehicles by 2040.

The final mix will depend on

the willingness of governments

and industry to invest in

hydrogen infrastructure – for

example, by building refuelling

stations and introducing

hydrogen buses – as well as

consumer enthusiasm for

hydrogen cars. But whether it

ends up being hydrogen or battery

power that wins the bigger share,

any dent in the dominance of

petrol vehicles is likely to be a

good thing. With less emitted

carbon warming our globe, less

toxic exhaust fumes choking our

lungs and less smog staining our

skylines, we will all be better off. ■

“There are only about 6000

hydrogen vehicles on the

road globally, versus

2 million electric vehicles”

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A chemical reaction between oxygen and hydrogen generates electricity, which is fed to the car’s

battery and motor. Water is the only by-product, leading to clean emission

generationPower Battery

Motor

High-pressure

hydrogen tank

O 2 H^2

Fuel cell stack

Water out

Air in (oxygen)

Hydrogen in

SOURCE: TOYOTA

Car type Petrol Battery Hydrogen

electric fuel cell

Emissions Carbon dioxide, None Water

carbon monoxide,

NOx gases etc.

Typical refuel/ 3-5 minutes 8 hours 3-5 minutes

recharge time

Typical range 400 kilometres 300 kilometres 500 kilometres

Typical 8 cents/ 3 cents/ 13 cents/

running cost kilometre kilometre kilometre