Michael Ross via EV wrote:
Electrolysis has thermodynamic limits to efficiency, but making H2 and O2 are a good way to store, large scale, renewable energy for which no other means are as environmentally sound.
I happened to see a news article in the June 2019 issue of Machine Design magazine. Researchers at Standord University built a new kind of battery/fuel cell.
It charges during the day with solar power. It is discharged at night, when the power is needed. The charging process uses electrolysis to break water into H2 and O2; this is recombined in a separate cell to generate electricity.
Since it's using electrolysis, it's not very efficient. But there's a twist: The charging is done with seawater as the electrolyte! When the resulting H2 and O2 are recombined, you get electricity, and fresh water as a byproduct.
The team thinks it can be used for desalination plants onboard ship, or in arid seacoast regions. It could be less expensive, and have less environmental impact that present solutions.
I was struck by their cell technology. It is basically an Edison nickel-iron cell! They naturally tend to gas a lot, and use potassium hydroxide as the electrolyte. Instead of minimizing the gassing, the researchers are maximizing it. The salt in seawater provides chlorine instead of potassium, which still works.
Normally, the chlorine in seawater would corrode the nickel. So they layered nickel-iron hydroxide on top of nickel sulfide, to cover and protect the nickel plate itself. So far, the new cells can convert electricity into H2 and O2 using seawater as efficiently as normal electrolysis cells using pure water. It also handles up to 10 times higher current densities, and last about 1000 hours.
More work is obviously needed. But it's a promising new twist on an old technology.
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