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I am (was) a chemist but I find this research area somewhat puzzling. Electrolytic hydrogen production has been industrialized for more than a century. Put nick

I am (was) a chemist but I find this research area somewhat puzzling. Electrolytic hydrogen production has been industrialized for more than a century. Put nickel electrodes in an aqueous solution of potassium hydroxide. Separate anode and cathode with a porous diaphragm. Run direct current through it. Get pure hydrogen. "Simple" alkaline electrolysis is only ~50% efficient, but that means there's only a factor of two efficiency gain possible no matter how good your catalyst. Large commercial electrolyzers from a decade ago reached ~70%. Why so much research on further marginal efficiency gains from new catalysts? Are there other costs that fall faster-than-linearly with improved efficiency?

epistasis 9y ago
>“Cost-wise, it is much lower and performance-wise, much better,” Having lower catalyst costs may allow for more installations that are used only intermittently. I know very little about the research in this particular field, but am not surprised that it's seeing more attention. As intermittent renewable electricity generation continues to get cheaper and replace fossil fuel sources, there's going to be a massive interest in using the large amounts of curtailed energy in someway. California is currently curtailing GWh per day of solar, and there's still a fairly low amount of renewable penetration. The question isn't necessarily about storing hours of energy, but perhaps weeks or maybe even months. Power to gas to electricity is currently only about 1/3 efficient, but depending on the cost curve of various battery technologies, there could be a big case for generating and storing a few months worth of methane mixed with hydrogen for winter months in the northern hemisphere. I bet there are likely to be far more research into combining electrolysis with methanation (perhaps with CO2 that's already dissolved in the water) or even chains of carbon. CNG automobiles, fueled with methane made from surplus renewable energy, might be a way for natural gas to be used in the future. We'll see if its ever economical, but there may be some great use cases for it.
- philipkglass 9y ago
  I agree that cheap-but-intermittent renewable electricity calls for differently optimized electrolyzer designs. Optimize for "cheap to manufacture and maintain" so you can afford to use them at a low duty cycle. If that is the underlying objective for this research, it's great, but doesn't come through clearly in the linked report. They mention efficiency in the headline, efficiency 7 times more in the body, and cost only twice, only in the body.
trelliscoded 9y ago
The general goal of the research grants is to create a technology stack that takes sunlight as input and provides hydrogen as output. Such a thing would allow production of storable energy in the open ocean, immediately making the rest of the planet inhabitable by people.
derefr 9y ago
Does the electrolysis of water in the presence of the currently-used catalysts gradually corrode the anode/cathode, reducing efficiency and requiring eventual maintenance? If so, this could simply be a Total-Cost-of-Ownership thing: reducing maintenance costs or extending cycle time by decreasing corrosion.
Animats 9y ago
Large commercial electrolyzers from a decade ago reached ~70% (efficiency)." That's good to know. No "breakthrough" can improve the process by more than another 30%. NREL says the best commercial systems are at 73% today.[1] There's also an additional energy cost for compressing the hydrogen. That's pretty good. Getting any chemical or electrochemical process up to 73% efficiency is a good result. [1] http://www.nrel.gov/docs/fy04osti/36705.pdf http://www.nrel.gov/docs/fy04osti/36705.pdf
- philipkglass 9y ago
  That was actually the data source I was thinking of. It's reviewing units commercially available by the end of 2003. More time had passed than I thought. I agree that the efficiency is already pretty good and even a "perfect" system would not drastically lower energy inputs further.

epistasis 9y ago

>“Cost-wise, it is much lower and performance-wise, much better,” Having lower catalyst costs may allow for more installations that are used only intermittently. I know very little about the research in this particular field, but am not surprised that it's seeing more attention. As intermittent renewable electricity generation continues to get cheaper and replace fossil fuel sources, there's going to be a massive interest in using the large amounts of curtailed energy in someway. California is currently curtailing GWh per day of solar, and there's still a fairly low amount of renewable penetration. The question isn't necessarily about storing hours of energy, but perhaps weeks or maybe even months. Power to gas to electricity is currently only about 1/3 efficient, but depending on the cost curve of various battery technologies, there could be a big case for generating and storing a few months worth of methane mixed with hydrogen for winter months in the northern hemisphere. I bet there are likely to be far more research into combining electrolysis with methanation (perhaps with CO2 that's already dissolved in the water) or even chains of carbon. CNG automobiles, fueled with methane made from surplus renewable energy, might be a way for natural gas to be used in the future. We'll see if its ever economical, but there may be some great use cases for it.

philipkglass 9y ago
I agree that cheap-but-intermittent renewable electricity calls for differently optimized electrolyzer designs. Optimize for "cheap to manufacture and maintain" so you can afford to use them at a low duty cycle. If that is the underlying objective for this research, it's great, but doesn't come through clearly in the linked report. They mention efficiency in the headline, efficiency 7 times more in the body, and cost only twice, only in the body.

trelliscoded 9y ago

The general goal of the research grants is to create a technology stack that takes sunlight as input and provides hydrogen as output. Such a thing would allow production of storable energy in the open ocean, immediately making the rest of the planet inhabitable by people.

derefr 9y ago

Does the electrolysis of water in the presence of the currently-used catalysts gradually corrode the anode/cathode, reducing efficiency and requiring eventual maintenance? If so, this could simply be a Total-Cost-of-Ownership thing: reducing maintenance costs or extending cycle time by decreasing corrosion.

Animats 9y ago

Large commercial electrolyzers from a decade ago reached ~70% (efficiency)." That's good to know. No "breakthrough" can improve the process by more than another 30%. NREL says the best commercial systems are at 73% today.[1] There's also an additional energy cost for compressing the hydrogen. That's pretty good. Getting any chemical or electrochemical process up to 73% efficiency is a good result. [1] http://www.nrel.gov/docs/fy04osti/36705.pdf http://www.nrel.gov/docs/fy04osti/36705.pdf

philipkglass 9y ago
That was actually the data source I was thinking of. It's reviewing units commercially available by the end of 2003. More time had passed than I thought. I agree that the efficiency is already pretty good and even a "perfect" system would not drastically lower energy inputs further.