• Geoff Russell

Hydrogen ... hype or heaven?

Updated: Sep 24

You can burn hydrogen and it contains more energy per kilogram than petrol. That makes it sound terrific, but a cubic metre of hydrogen at normal atmospheric pressure only weighs 82 grams ... so a kilogram of the stuff occupies some 12 cubic metres!

The other issue with hydrogen is that there isn't any.

As a gas, hydrogen is rare. But, as a part of other molecules, it is common. So if you want it, you have to break up those molecules, which takes energy. And then you have to compress it, which also takes energy. Which means that the usefulness of hydrogen as a source of energy is like anything else; it depends on the efficiency of a variety of processes.

Most people rightly regard it as an energy storage medium, not an actual source of energy. Of course, the same could be said of oil. It's just that we don't have to pay for, and generate, the energy in the oil we pump out of the ground.

Hydrogen for vehicles has to be stored at high pressure ... typically 700 bar (which is about 10 tonnes of force per square metre). Even at that high pressure, it takes considerably more space to store petrol station sized amounts of the stuff; about 7 times more space. So if you've ever seen the petrol tanks under a petrol station, then think about them going 7 times as deep ... or getting much more frequent deliveries. The tanks in a vehicle will also have to hold high pressure hydrogen, and we'll need to get used to that, exactly as we have become used to big tanks of petrol exploding frequently. In the US alone, petrol tank fires kill over 100 people per year in about 156 fires per day. Battery fires and hydrogen fires will occur but they'll have a hard time matching that!

The International Energy Agency did a large report last year called "The Future of Hydrogen". It's pretty much a one stop shop for everything you ever wanted to know about hydrogen. But you need to read it with a critical mind, because it is definitely spruiking for the industry. Which is fine, there will definitely be a role for hydrogen in our energy future, but everybody has to beware of the kind of hype that emerges quickly when people smell a chance for big bucks and Government subsidies.

Generating hydrogen

How do you make hydrogen? Globally, we already make about 70 million tonnes of the stuff per year. Almost all of it is made from natural gas ... which is just methane. The formula is CH4, which is one carbon and four hydrogens. So the process isn't at all climate friendly.

One of the other ways to make hydrogen is to split water ... easier said than done. You can split it with an electric current and the process is called electrolysis. The word "lysis" means to split, and the term is used in biology also ... where it means breaking open a cell.

So if you have a climate friendly form of electricity you can make climate friendly hydrogen.

So how much electricity and water do you need to make a tonne of hydrogen?

You need around 9,000 litres of water to make a tonne of hydrogen using hydrolysis. The IEA report says this is about double the amount used to make hydrogen using natural gas. In both cases we are talking about using water in the sense of totally transforming it. Most current energy systems use water for cooling. In these situations, the water doesn't vanish, it may evaporate, or end up in a cooling pond, but when you make hydrogen by either method, the water is lost during the process. The hydrogen atoms from the water end up in the product.

If you use solar power to make hydrogen, then you need about 51 million watt hours to make a tonne of hydrogen. So a 250 hectare solar plant, like that at Nyngan in NSW, could make about 4,500 tonnes of hydrogen per annum.

If you think about one of Australia's large LNG plants, like Gorgon in WA, which produces 16 million tonnes of LNG annually, you'd need about 1300 Nyngans covering 325,000 hectares with 1.7 billion panels to generate the amount of hydrogen needed to replace that LNG. This may not generate climate damaging pollution, but it will have a huge impact on the animals and plants in that 325,000 hectares; not to mention the mines and factories required to make the materials in the panels.

During Australia's recent summer from hell, there was an estimate that a billion animals had been killed. This was based on population density studies in areas cleared in NSW. The figures were assembled by Prof. Chris Dickman. The number of animals killed per hectare burned was about 160 and this was an estimate that only covered about half of the total area that ended up being burned. It also didn't include bats, frogs or fish or invertebrates. A recent project at a the Chevron LNG plant in WA moved some 30,000 animals over a 1000 hectare area to make way for an LNG plant.

How many animals will be displaced by 325,000 hectares of solar farms? Many solar advocates argue that Australia is a huge continent, so we have plenty of space. But the realities of building things like solar farms is that you need highways or rail links to shift the massive amount of materials required for these plants. That seriously limits where plants get built, as does the transmission grid. So an estimate of the destruction caused by such plants will be difficult; suffice to say that the environmental cost of zero carbon hydrogen is massive.

Nuclear plants and hydrogen

The other way of making hydrogen is to use a high temperature nuclear power plant. As with coal or gas plants, designing a nuclear plant to run at high temperature makes it considerably more efficient and opens up a raft of applications in addition to "merely" generating electricity. Using heat directly rather than electricity is more efficient and has many other industrial uses. A Japanese high temperature testing nuclear reactor operated for 150 hours continuously in 2019 producing hydrogen. It is one of many such projects around the world.

It's hard to envisage 1300 Nyngan solar plants. So here's a map showing the area occupied by just 40 ... so just multiply by 32 and you can get an idea. The map shows the size of the 40 Nyngan plants required to replace a single nuclear plant in Germany; the Leibstadt plant.

Risks and perception

Battery fires are news worthy precisely because they are rare. Ditto hydrogen fires. But cars catching fire is so common that it will rarely get beyond a local news report, unless there are multiple fatalities, in which case the report may go national. Nuclear power accidents are like battery accidents, except even more unusual. Nuclear power is so extraordinarily safe that even the smallest of accidents generates both news and terror out of proportion to the actual body count; which is rarely mentioned because it is typically zero.

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© 2020 Geoff Russell