Written 2005-12-07
Listeners to Paul Harvey will have heard on November 16, 2005, the following:
“… And here comes tomorrow – an exciting tomorrow! Hundreds of semi-trailer trucks are at this moment zipping along American highways with hydrogen in the gas tank. These are 18-wheelers where they make the hydrogen as they go. One big rig can thus save $700 a month making fuel on the go. It uses electricity from the engine’s alternator to power the electrolysis of water to produce the hydrogen.”
Now, I’ve been a fan of hydrogen as a fuel since the 70’s, calling it ‘the fuel of the future’. I said, “… of the future” because of various economic and practical considerations.
Hydrogen (H2) has a very low energy density, that is, a given volume of H2 has much less energy than the same volume of gasoline. To compete with gasoline, energy density-wise, H2 needs to be compressed and liquefied, itself requiring heavy tanks and compressors and such to keep it supercooled. Gasses kept under pressure tend to leak and in the case of H2, this introduces safety concerns.
But Mr. Harvey said the H2 consumed by the ‘big rigs’ is produced on the go, so I was intrigued. Hydrogen is typically extracted as a byproduct of natural gas production or extracted from water via electrolysis.
The problem with electrolysis is that the amount of energy required to extract H2 from water is more than the amount of energy available from burning the extracted H2. For example, the energy required to produce enough H2 via electrolysis to generate 1000 BTUs of energy would itself exceed 1000 BTUs. It’s a net loss.
Think about that. If it required less than 1000 BTUs of energy to extract 1000 BTUs worth of hydrogen by electrolysis, it would have been the fuel of today in the last century. We’d have had unlimited, cheap power years ago. The oceans are just brimming with H2O. All we need is an economical way to extract the H2 from the H2O. We have not, to my knowledge, achieved that goal yet.
So I was moved to investigate Mr. Harvey’s statements. I searched the web and found:
<http://www.wired.com/news/autotech/0,2554,69529,00.html>
This page has links to the company whose gizmo has been fitted to the trucks in question.
Points of note:
H2 is used only to supplement the fossil fuel being burned. H2 is injected into the incoming air going to the engine. It is said to reduce emissions and increase fuel economy by 10%. Energy-wise, production of the H2 is doubtless a net energy loss. Perhaps the H2 results in more thorough burning of the fossil fuel to achieve these effects. Or perhaps is just hype and snake oil.
Like much of what goes out as ‘news’, this item probably originated as a press release issued by the company manufacturing the H2 extracting gizmo. The reality did not live up to the images created by Mr. Harvey. Hydrogen is still just the fuel of the future.