Hydrogen is already fuelling trucks, buses and industrial processes. And a large ‘green’ gas factory could replace the power (and jobs) lost if the Tiwai aluminium smelter closes. Olivia Wannan explains the hottest new lower-carbon fuel.
In 30 years, we’ve pledged to bid goodbye to the fossil fuels that power our vehicles, factories and some of our power plants. We’ll replace them with green fuels, such as electricity, wood and biofuel. Experts are also excited about the potential of another fuel: hydrogen gas.
Once created, it can be burned to create heat, replacing fossil fuels such as natural gas and LPG. Used in a fuel cell, it creates electricity. On top of that, the gas can also replace fossil fuels in industrial processes, such as the manufacture of fertiliser.
It can be made using renewable electricity, meaning it’s a sustainable fuel. (This is rare, though.)
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Unlike fossil fuels, hydrogen fuel doesn’t produce carbon dioxide, which is heating our planet. Water vapour is its main by-product.
The first element
Hydrogen is an element that dates back to the Big Bang.
When two hydrogen atoms bond they form a gas, and there are trace amounts of hydrogen in the air we breathe.
At minus 235 degrees Celsius, the gas turns into a liquid. Mostly, we store hydrogen as a compressed gas.
However, the double-bonded gas isn’t hydrogen’s preferred form. Given half a chance, the gas will nab an oxygen molecule and become dihydrogen monoxide (two hydrogen atoms and one oxygen) – in other words, water.
That reaction is set off by a spark, and a large amount of energy and water vapour is released.
The energy can send a rocket to space (liquid hydrogen is literally rocket fuel) or power whatever engine we’d like.
But there’s a second method to create energy from hydrogen gas – a fuel cell, which is often more efficient. Rather than a flame, a chemical reaction takes place.
Oxygen gas is fed into one side of the fuel cell and is divided into solitary oxygen molecules, with the help of the metal platinum.
This is an enticing prospect for the hydrogen gas fed into the other side of the fuel cell. To reach its beloved oxygen, the hydrogen splits itself into two, banishing its negatively charged electron – this constant flow of electrons equals electricity.
Hydrogen is then able to migrate through the dividing membrane, reach oxygen, reclaim an electron and form water. This technology was first invented in 1842 and provided electricity for the Apollo spacecraft.
Why the origin matters
Hydrogen exists in a number of complex chemicals, as well as water and that pure gas form. The proteins, fats and carbs we eat are full of it.
Natural gas (the fossil form of methane) contains carbon and hydrogen. It can be combined with steam to create pure hydrogen gas plus carbon dioxide. Unfortunately for the climate, natural gas is one of the cheapest ways to make hydrogen gas. Most of the hydrogen produced today is created this way.
There are lower-carbon alternatives, though – and because keeping track of the origin is so important, hydrogen is often assigned a colour. For example, ‘brown’ hydrogen is created using coal, and ‘grey’ hydrogen from natural gas.
The gas with the potential to cut emissions is ‘green’ hydrogen.
It’s made in an electrolyser, which does the exact opposite of the fuel cell. Electricity and water are fed in and ‘green’ hydrogen and oxygen come out.
One of the country’s first industrial electrolysers was installed in 2014 by industrial gas company Boc at Glenbrook. Hiringa Energy is also building electrolysers around the country.
Notably, the electricity in our wires isn’t zero carbon. Our national grid relies on fossil-fuelled power plants to provide about 20 per cent of the country’s electricity. To combat that issue, Boc and Hiringa funded new renewable generation to cover their electricity demands.
Power companies Meridian and Contact are also eyeing up huge amounts of electricity used by the Tiwai aluminium smelter every year, coming from Lake Manapouri. If the smelter closes as expected at the end of 2024, the power could be directed to a large green hydrogen factory.
Under the shadow of the Hindenburg
Mention hydrogen gas and many think of the Hindenburg, the air ship that caught fire in 1937, courtesy of static electricity and some flammable paint. When mixed with air and a spark, hydrogen ignites.
Hydrogen does have unique physical quirks.
First up, hydrogen is very light. If it leaks into the open air, it will quickly disperse. But if hydrogen leaks into a poorly ventilated space, it can build up, and is more likely to spark and catch alight (into an almost invisible flame) than fossil gas.
To evaluate the real-world consequences, the UK gas networks have built a test site with four unoccupied houses where they can simulate a hydrogen leak, to determine if the gas is at least as safe as its fossil alternative.
Gas explosions will be more of a risk in places like factories, though these industries are used to managing hazards.
But hydrogen is far more likely to leak out of a pipe in the first place – since it can actually react with the pipe itself, causing cracks.
First Gas – which owns the natural gas pipes in the North Island – has identified up to 13 per cent of its underground pipes that could be affected when hydrogen is introduced into its system from 2030. The organisation says it’s keeping an eye on the latest science.
However, engineer Johann Land says the gases aren’t interchangeable, and a pipe system designed to transport methane will need to be upgraded to carry hydrogen. “Anyone who says we can use a methane pipeline to transport pure hydrogen, I would question their engineering degree.”
Why don’t we have hydrogen vehicles?
Hydrogen fuel cells have existed for longer than the traditional petrol engine (invented in 1860) – but these engines took over because the fuel was much cheaper and more convenient. A similar thing is happening with the electric car.
There are just 13 fuel cell vehicles in the country, compared to about 30,000 EVs, according to government data. Experts think hydrogen cars are unlikely to ever catch up.
On the plus side, hydrogen refuelling is speedy: when you arrive at the station, it takes only about five minutes to top up your tank of compressed hydrogen, compared to at least half an hour to juice a car battery.
But at the moment, New Zealand has no hydrogen refuelling stations. In comparison, almost every house in the country has electricity, most supplied through the national grid.
Hold that down-payment on a hydrogen car
Unless hydrogen gas is made on site, delivery is a big challenge. Currently, hydrogen vehicles – such as the Ports of Auckland bus – rely on fossil-fuelled trucks to transport their fuel.
The North Island has an underground system of gas-delivery pipes, which is currently transporting natural gas from Taranaki north to Whangarei, east to Gisborne and south to Wellington. The pipeline owner plans to blend in green hydrogen with natural gas, aiming to eventually replace the fossil fuel entirely.
But if you put anything but pure hydrogen into a hydrogen car, it’ll break down. At the same time, it’s unsafe to feed 100 per cent hydrogen into the appliances in today’s homes, as the devices were built to handle natural gas. The network is caught between moving too slowly for vehicles and too fast for homeowners, who will eventually have to buy hydrogen-compatible appliances.
There’s also a question of how many hydrogen cars the world can produce. The tech relies on rare metals including platinum – which is in even shorter supply than the lithium in EV batteries.
Hydrogen also struggles to beat the electric car on fuel prices. Hiringa Energy chief executive Andrew Clennett says a hydrogen car costs roughly the same as petrol – about $16 to travel 100 kilometres in a small vehicle. A similar-sized electric car is just over $5.
It takes two steps to create green hydrogen, and just one for electricity. Therefore, an electric car may always have a price advantage.
But since electric tech struggles with longer distances and heavier loads, hydrogen could make in-roads with trucks. That’s why Hiringa Energy is targeting freight, not private travel.
In 2022, it plans to open the first four truck refuelling stations across the country, with hydrogen gas manufactured in nearby electrolysers. A Taranaki wind farm and electrolyser will generate a back-up supply.
Hydrogen on the factory floor
Hiringa’s choice of Taranaki for a back-up plant isn’t random. It’s on the grounds of one of the biggest hydrogen gas producers in the country: Ballance, a fertiliser company.
Ballance takes natural gas from local gas fields and, first, transforms it into hydrogen. This (grey) hydrogen is further mixed with air and water to create a nitrogen-rich synthetic fertiliser. In this way, the company makes 280,000 tonnes of the stuff each year to boost plant growth.
When the green hydrogen starts flowing, Ballance wants to make up to 7000 tonnes of fossil fuel-free fertiliser (though this unfortunately won’t be zero-emission, because nitrogen is transformed into the greenhouse gas nitrous oxide in paddocks).
By taking advantage of hydrogen’s determination to partner up with oxygen, metal-makers could also dramatically cut their carbon footprint.
Metals such as impure iron have oxygen attached. To purify the metal, coal is often burned to create carbon monoxide – which nabs an extra oxygen atom to become carbon dioxide. By replacing fossil fuels with hydrogen gas, this process would create water vapour instead.
The chemistry works in theory. Steel companies are now trying to crack the process at scale, according to NZ Steel’s Robert Bebelman. “It’s still very early days, but it’s pretty exciting.”
The opportunity and the elephant
Between the desire for hydrogen in factories, boilers and vehicles, the Government is hoping green hydrogen could become a new export industry for Aotearoa, to countries such as Japan and Singapore.
But Huntly is the elephant in the room. The power plant is burning record amounts of coal this year, because our hydro lakes are low and natural gas is in short supply.
For each new green hydrogen factory, we’ll need to build the equivalent supply from geothermal, wind and solar – or we’ll blow our credibility and emissions. This will be a case of running just to stand still.
The country could cut far more emissions by electrifying something at home rather than sending a fraction of that energy in the form of hydrogen overseas.
In particular, international shipments of hydrogen are problematic: long-term storage and long-distance transport of the gas isn’t cheap. We may have to convert it into a more stable chemical (one suggestion is ammonia) to affordably deliver it to export markets.
Clennett says the world will need green hydrogen. “There’s so much opportunity for New Zealand in this space to be a leader.”