When it comes to elements, they don’t come any less complex than hydrogen. And as far as dealing with carbon dioxide emissions is concerned, at first glance it offers a very simple solution. Hydrogen + Oxygen -> Water + Energy. No carbon dioxide!
No wonder it has been receiving so much attention lately. And it certainly got plenty of airtime at Chemeca 2019 in Sydney at the start of October. Australia’s Chief Scientist and Engineer, Dr Alan Finkel gave an inspiring talk, in which he laid out a grand vision of how Australia could, and should, become a global scale producer and exporter of hydrogen. But unlike many others proclaiming the marvels of hydrogen in the news lately, Dr Finkel was very up front about the challenges involved in making a hydrogen economy a reality, and of the progress being made to address those complex challenges one bite at a time. For example…
Challenge 1: Hydrogen is a very low density gas so takes up too much space in vehicles to be a viable fuel for long distance travel.
Solution: Polyethylene lined carbon fibre tanks can hold hydrogen at pressures of up to 700 bar, which gets the density up to about half that of liquid hydrogen. If you live in California you can now buy a Hyundai Nexo SUV, which uses a couple of these carbon fibre tanks to obtain an estimated driving range of over 600 km. And if you were wondering how risky it is to drive around with a couple of high pressure hydrogen cylinders in your car with you, you may be pleased to hear it was recently crash tested by the US Insurance Institute for Highway Safety (IIHS) who awarded it the best-available Top Safety Pick+ rating. Presumably that means they couldn’t get it to explode… The wonders of carbon fibre!
Oh, and if you’re in the market for something a little bigger than an SUV you could consider a Nikola One Truck.
To be fair though, as Ken Rivers pointed out during his talk, the inherent low density of hydrogen compared to jet fuel does present a significant challenge in some applications, such as long-haul air travel, where it has long been recognised that the huge cryogenic fuel tanks required would make a typical passenger jet look more like the Airbus BelugaXL. Which some of us think might not be so bad…
Challenge 2: Hydrogen is expensive to ship on a large scale.
Solution: Apparently you can ship hydrogen quite cheaply in the form of ammonia and separate it out at the other end using vanadium palladium membranes (hmm they don’t sound super cheap…), or of course you could just use the ammonia as a fuel directly.
Heck, if you wanted to you could even ship your ammonia in an ammonia powered ship!
Challenge 3 (this one is a biggie): It takes way too much renewable electricity to produce green hydrogen and supply it at high pressures.
Solution: Engineers. Dr Finkel left this challenge with the engineers to resolve. No pressure!
However, he did suggest as a bit of a workaround in the meantime, it may soon be cost-effective to produce so-called “blue hydrogen”, using methane reforming with carbon capture and storage on the back end. Apparently in the methane reforming process the carbon dioxide byproduct is produced at fairly high concentration (~30%) and reasonably high pressure (~40 bar), which should make it far more cost-effective to capture and store it than it typically would be on most other carbon capture and storage (CCS) systems.