When I was very young, our gas stove

ran on town gas. I didn’t know it at the

time but it was a mixture of hydrogen and

carbon monoxide produced from coal.

One day a serviceman came round

to change the nozzles on our stove and

gas heater, and very quickly our house,

and eventually the city, were converted

to natural gas (methane). It was a leap

into modernity.

Not only did it eliminate

pollutants emitted during gasification, it

promised a seemingly unlimited supply of

clean burning methane from offshore gas

fields.

But that was in an era where “clean”

meant “free of the toxic chemicals and

particulates released by coal gasification”.

Today, clean also means free of carbon

dioxide.

As the global community works

to decarbonise its electricity supply, one

of the biggest remaining sources of carbon

dioxide emissions will be from burning

methane for heating and cooking. In a

back-to-the-future step, many futurists are

contemplating a variation of town gas –

pure hydrogen.



Today, most hydrogen is produced

from fossils fuels, emitting large quantities

of carbon dioxide as a by-product, so that’s

no help. But there’s increasing interest

in producing it from pure water. In a

well-known process called electrolysis,

excess electricity from wind or solar farms

is passed through water to crack it into

its atomic constituents – hydrogen and

oxygen.



When the hydrogen is used for stoves,

or space heating, the only combustion

product is water vapour! So what’s

standing in the way of this utopian fuel?

Problem one is that producing

hydrogen from electricity is only 70%

efficient, so you need a very cheap

electricity supply. It could be coming.

As

our electricity is increasingly sourced from

wind and solar, the amount available will

often exceed the electrical load. Owners of

the generators will seek an economically

worthwhile purpose for this excess, such as

charging batteries, desalinating water, or

making hydrogen.

Instead of burning

the hydrogen, an

alternative use

would be to use it

to store energy, like

in a battery, then

regenerate electricity

in a turbine generator

or a fuel cell.





Problem two is that the current large-scale

electrolysis units are so expensive

that the cost of producing hydrogen is

several times more than natural gas.

But one thing we know for sure is that as

manufacturing volumes increase, costs

come down. We’ve seen it already in

related industries.

Wind turbine prices have halved

in the past five years and solar prices

have dropped even faster. Similar cost

reductions are likely for electrolysis units.



Problem three is that steel pipes – a

major part of the current gas delivery

infrastructure – aren’t suited to

transporting hydrogen. They become

brittle because the hydrogen molecules

work their way into the spaces between

the iron atoms and eventually cause cracks

to form.

Fortunately, modern piping used

for gas distribution is mostly made from

polypropylene and does not suffer from

this problem.

Hydrogen can be mixed at up to 10%

with the methane in the existing gas

distribution network without any risk of

corrosion nor need to change the nozzles

on stoves or space heaters. Above 10%

hydrogen concentration it’s easier to

commit and convert all gas appliances to

run on pure hydrogen.

The city of Leeds in the UK has a plan

to do this in the late 2020s.

Instead of burning the hydrogen, an

alternative use would be to use it to store

energy, like in a battery, then regenerate

electricity in a turbine generator or a fuel

cell. But it makes for a very inefficient

battery.



The round-trip efficiency – electricity

to storage medium and back to electricity

– is about 35%, much worse than the 90%

efficiency of a lithium ion battery. So this is

a less attractive use for the hydrogen than

using it to replace natural gas in our cities

for space heating and cooking.



If we can successfully make the

transition to hydrogen for heating and

cooking we will have a winning fuel that we

can keep using literally forever.

The main

impediment today is cost.

I used to be sceptical that hydrogen

use would become widespread, but given

the rapid rate of reduction in the price of

renewable electricity, and a reasonable

expectation that the price of electrolysis

will continue to fall, the economics might

indeed work out.