Making hydrogen electrolysers super efficient

The traditional electrolysis process is relatively inefficient.   If you use surplus green electricity to produce hydrogen and then burn the hydrogen to make electricity, its round-trip efficiency is low, much lower than alternative energy storage techniques:

 

Flora noted that converting power to hydrogen and then using the fuel to generate power has a relatively low round-trip efficiency. Round-trip efficiency is the percentage of electricity retrieved after being stored.

The technology to convert power to hydrogen and back to power has a round-trip efficiency of 18%-46%, according to data that Flora presented from the Massachusetts Institute of Technology and scientific journal Nature Energy. In comparison, two mature long-duration technologies, pumped-storage hydropower and compressed air energy storage, boast round-trip efficiencies of 70%-85% and 42%-67%, respectively. Flow batteries, a rechargeable fuel cell technology that is less mature, have a round-trip efficiency of 60%-80%. 

(Source: S&P Global --- Hydrogen technology faces efficiency disadvantage in power storage race
)

[Incidentally, Elon Musk claims that's Tesla's lithium-ion batteries have a round-trip efficiency of 93%]

But an Australian start-up, Hysata, is developing a process which enormously increases the efficiency of electrolysis.    I've already talked about this company and their super efficient hydrogen electrolyser, here.  

This update is from ARENA (Australian Renewable Energy Agency)

A pioneering, all-Australian hydrogen electrolyser technology is getting the chance to prove itself at a commercial scale.

If it works, the project has the potential to transform the economics of renewable hydrogen production.

ARENA’s support has helped develop this new technology since it was a concept in a University of Wollongong laboratory. That work saw a spin-off company, Hysata, established to commercialise the development.

Now, Hysata will receive $20.9 million ARENA funding as part of a $47.5 million project. Hysata will build and test a 5 MW system at its new Port Kembla manufacturing facility.

The plan then is to move the entire system to Rockhampton in Queensland, for installation and trials next to the Stanwell Power Station.

Queensland government-owned power company Stanwell Corporation is providing the site and facilities, and also backing the project with $3 million.

ARENA CEO Darren Miller says the project is a crucial step to enabling purchase orders for the technology.

“Hysata’s electrolyser technology could be a game-changer for renewable hydrogen,” Mr Miller said.

“The demonstration at Stanwell’s site will be key to unlocking commercial demand for Hysata’s product by proving the technology works at scale.

Currently, the production cost of renewable hydrogen (using renewable energy) is at least twice that of hydrogen produced from fossil fuels. Hysata says its technology will slash costs and produce hydrogen “well below” a competitive target price of $2 per kilogram (approx. US$1.50/kg).

FYI, if there’s one number you should remember, it is that price of $2 per kilogram. That’s the key to competing with fossil fuel-derived hydrogen and fully unlocking renewable hydrogen’s industrial and energy future.

It’s all in the bubbles.   All electrolysers work by passing an electric current from electrodes through H2O – water. The current splits the water into its two parts, hydrogen and oxygen. That process takes energy.

Now, if the entire process were 100 per cent efficient, all that energy would go into splitting the water. Nothing else.

But, until now, electrolysers have also produced a lot of heat. That’s because, just like an electric heater at home, they have electrical resistance.

The heat generated is not only wasted energy, but it must also be removed. Electrolysers need a lot of cooling and that uses even more energy.

So, if you can reduce resistance, a greater proportion of energy is available to split the water. Also, the system generates far less far less heat, which in turn requires less cooling.

Hysata has tackled the problem by completely redesigning their electrolyser to remove all the main sources of electrical resistance.

It turns out, that means eliminating hydrogen and oxygen bubbles. When bubbles form on the electrolyser’s electrodes, they reduce the surface area available for electrolysis and increase resistance.

In fact, Hysata says it has completely eliminated bubbles from its system and cut electrical resistance to virtually zero. As a result, Hysata says it expects a fully operational electrolyser will stay cool through good air ventilation alone.

The combined effect is what has raised the overall efficiency of a Hysata electrolyser to around 95 per cent. That’s a huge jump on current technologies, which operate with efficiencies closer to 75 per cent.

To put that in context, to make renewable hydrogen competitive with its fossil-fuel derived alternative, the International Renewable Energy Agency (IRENA) in 2020 set an electrolyser efficiency target of up to 85 per cent … by 2050.

I'm not sure that hydrogen by itself is in fact the future.   To transport it, you need to compress it and refrigerate it, which takes additional energy, further reducing its round-trip efficiency.  Also, it makes gas pipes brittle, and, because its molecules are so small, it easily escapes through the gaps in the molecular lattices of gas pipes or storage tanks.   But if you convert it to methane, using the Sabatier process, it's the equivalent of natural gas, and in fact is called synthetic natural gas (SNG, which is a bit of an oxymoron, no?)  And then you can use the existing gas distribution system and gas storage system, as well as existing gas turbine electricity generators.  On the other hand, to make SNG, you need a source of CO2, and unless you use the escape gases from a gas-turbine power plant flue, you have to produce CO2 using direct air capture, which is still very expensive.

We will need seasonal (or long-term storage)  to reach 100% renewables, and hydrogen, or more probably, SNG, will be how we fill that gap.  So, if this can be commercialised, it will be a huge step forwards towards a 100% green energy system.