4 ms·
What makes electrolysis expensive is a whole bunch of secondary details. Impurities in the water foul the catalyst, or steal power for side reactions that may c
by pencilguin 4y ago
What makes electrolysis expensive is a whole bunch of secondary details. Impurities in the water foul the catalyst, or steal power for side reactions that may contaminate the product or the water. The best catalysts are expensive metals that you would like not to erode and be carried away.
After you get the hydrogen atoms separated from the oxygen, the oxygen atoms bond to become O2 molecules, releasing heat uselessly, and will later need to separated again (other oxygen, of course) when you burn the hydrogen, consuming much of the released energy; and likewise for hydrogen molecules.
The recent story about using water vapor as the feedstock might signal a solution to the impurities and erosion problems that introduces new problems to solve before it can be used.
Efficiency of the process is becoming unimportant as the cost of solar and wind-generated energy continues rapidly down, making other things like the cost of equipment and the volume of production more important.
The frequent reports on improvements to electrolysis indicate not hype, but research cumulatively improving an important process, just as improvements in production techniques drove and still drive down the cost of solar panels.
- PaulHoule 4y agoAccording to Wikipedia existing electrolysis systems are between 70-100% efficient. It's not fundamentally difficult to do (when I was a kid I made a "rechargable bomb" that would fill a balloon with hydrogen+oxygen and blow it up) but if you are doing it at scale you are going to be very concerned about capital cost and energy efficiency so there is room for improvement.
- pencilguin 4y agoThe important number when using hydrogen to carry energy is the round-trip efficiency. It has been hard to improve the efficiency of the energy-releasing side. We are fortunate that the number's importance is declining.
- PaulHoule 4y agoI don’t think the main interest is energy storage today, I think it is to replace other sources of hydrogen in industrial processes. Hydrogen as a fuel to say cook food or run a power producing turbine competes with many other energy sources and carriers but for industrial purposes there is often no alternative or the alternative is carbon heavy. (E.g. carbon monoxide is used to reduce iron in a blast furnace, hydrogen is substitutable for CO for many metallurgical functions.)
- pencilguin 4y agoAs cost to produce falls, it will be used in more places. Ways to store and transport energy will be among those. LH2 is very attractive as aircraft fuel. But I take your point: for other uses, the production efficiency counts more. Conversion to raw heat is pretty good, losing only what it takes to split the H2 and the O2, and then whatever of that heat you fail to direct to the end use, e.g. the steam that rises past the sides of your saucepan.
- PaulHoule 4y agoIt competes with heat pumps for space heat, particularly given that air source heat pumps have gotten a lot better in 20 years. 20 years ago the word was that you needed a ground source heat pump in upstate NY but today air source heat pumps are completely practical.
- pencilguin 4y agoMine works down to a remarkably low temperature, but at that temperature is able to extract much less heat than the house needs to stay warm at that outside temperature. So I still burn a noticeable amount of propane, in bursts. A fuel cell driving a heat pump is an interesting notion. The "waste heat" from the fuel cell is not wasted, here. If half the contained energy drives the heat pump at, say, 3x, you get 1.5x vs just burning it. The extra expense of the fuel cell and heat pump seem hard to justify unless you have other uses for them. This is to say that hydrogen for home heating is unlikely to be important.