But sooner or later we’ve just got to get over our dependence on the burning of hydrocarbons in general and foreign oil in particular. Bombers and tanks and the crews to operate them are expensive and messy and they don’t stop global warming anyway. The so-called hydrogen economy is an oft-opined alternative. But how to obtain the hydrogen required is an open question. There’s three main ways to do it: electrolysis, thermolysis, and thermochemical cycles. The efficiency of using electricity to split water into hydrogen and oxygen via electrolysis is typically about 75-80%. Sounds good, until you remember that electric power generation efficiencies (steam from whatever heat source into electrical energy) is typically 30-35%. This makes the true overall conversion efficiency of water to hydrogen via commercial electrolysis only 20-25%. Thermolysis, a process in which steam is heated sufficiently to dissociate it into hydrogen and oxygen without a catalyst, requires very high temperatures that just aren’t economical.
That leaves thermochemical hydrogen production – the use of chemical reactions that free hydrogen at lower temperatures than are required by pure thermolysis. The two most highly developed thermochemical cycles are the sulfur-iodine and the calcium-bromine cycles. Both contain at least one reaction that requires temperatures greater than 750C, higher than is achieved by current electrical powerplants in normal operations. Argonne National Laboratory anounced research results this week on a new copper-chlorine thermochemical cycle in which the chemicals used are not consumed and are recycled. The reaction proceeds at 40% efficiency at only 500 degrees C. Thus a hydrogen production facility could be piggybacked on existing electrical powerplants at a higher overall efficiency than electrolysis. This research – or something it leads to – may well allow gasoline powered cars to be one day be replaced with fuel cell versions.
Your link to Saudi Arabia analogy is noted but thrown out for lack of logic and the fact that I come here for Science, not Politics.
…I’ll try to stick to science, which is what I’m more interested in, too.
On the topic of science, I enjoyed the rest of your write up. Thank you again for understanding. :)
You forgot that wind, wave, or ocean current power created electricity turns out practically to be 75% efficient, since the power to create the electricity didn’t involve combustion. Another method to produce hydrogen is with algae grown in the ansence of sulfur. It gives off hydrogen. Also by digesting the algae and producing methane and using the heating effect of the solar algae growth system, two extra sources of cogeneration besides the hydrogen are created.
The big chance for electric cars is rechargable zinc/air batteries that use granulated zinc that can be exchanged at “gas” stations for the used zinc oxide granuals in the car’s fuel tank. Zinc is plentiful and easily recharged at near 98% efficiency. Zinc/air cars and buses have the range, power, weight, and speed already to compete with gas cars. Given mass production and refueling stations coupled with solar, wind, wave power electricity, the technology now exists to make this non polluting system cost effective and workable.
The hydrogen idea is a political red herring to delay alternatives to infernal combustion, it is comfortable to the status quo because it’s impractical. The fuel cells, hi pressure tanks, and refueling systems are too expensive and the whole system is uninsurable because of explosive potential. Zinc/air won’t ever explode.
Now THAT is the kind of commentary I wish would be generated by every SFT article – thanks! Expect a zinc-air article in the near future – you’ve got me intrigued…or better yet, find some good links and submit one yourself!!!
Here’s some quantitative information about zinc, and a link, in the context of a comparison to my favorite, boron.
— Graham Cowan
100 internal combustion watt-hours in a baby’s fist
Um.. No, let’s come here for Science Fiction, not Science.
Like the SF that “warmer in the past 1,000 years” is a sign that humans are causing it. Yeah, it is warmer now… because it was warmer in 1003, and the Little Ice Age ended around 1900. Of course we’ve warmed up since being colder. (Try it yourself — some of those temp indicator datasets are on the net)
Or, of course, the myth that petroleum is from dead plants. Messes up a lot of politics if it is not true. Track that back and you’ll find it was a suggestion which wasn’t thought likely by its creator. Some people have trouble accepting a different idea, but I’ll invite you to find an explanation for helium deposits in oil fields and see what you figure out. Let’s start from: Helium is a noble gas that doesn’t react with plant material so dead plants do not have helium in them.