Is Hydrogen Really Safer?
Although its hard to argue with the concept of clean energy, and although, as a control systems or instrument engineer, I have a great deal of respect for Béla Lipták and his contributions to control systems engineering, I find some of his statements in his article on clean energy disturbing.
Whenever someone, and especially an engineer, uses the word obvious, I immediately become suspicious. In my opinion, nothing involving technology should be considered obvious. I believe some of the greatest engineering disasters have been the result of using this concept. All facts and scenarios should be checked and rechecked before theyre presented.
Lipták states that hydrogen is safer than gasoline. The system and its implications have, in my opinion, been ignored. I would refer anyone who thinks that hydrogen is safe to the North American and European safety standards and ratings. Furthermore, hydrogen, being the simplest and smallest molecule, is the most difficult to contain, not to mention the negative effect it has on metals.
Lipták also says that, For the last million years, the carbon dioxide concentration of the atmosphere stood at 280 ppm. Who was measuring the carbon dioxide content in the atmosphere 1 million or even 500,000 years ago? And, if no one was able to or interested in measuring CO2 in those ancient times, how was this conclusion reached?
Finally, we as engineers should not be jumping on bandwagons. What, we should be doing is examining all of the implications of the solutions proposed for problems and the systems, which will be affected by the solutions. Solving problems willy-nilly is the provence of technicians, not engineers.
Béla Lipták Responds:
I deal with both these topics in depth in my book, and, unfortunately, had no space for in-depth coverage of them in this brief article.
On the subject of hydrogen safety, I suggest reviewing its industrial safety record over the last 50 years compared to hydrocarbons. You will find that hydrogen is no more or less dangerous than other flammable fuels, including gasoline and natural gas. It has a rapid diffusivity (3.8 times faster than natural gas). meaning that when released, it dilutes quickly into a non-flammable concentration. Hydrogen rises six times faster than natural gas at a speed of almost 45 mph (20m/s). Because of the absence of carbon and the presence of heat-absorbing water vapor created when hydrogen burns, a hydrogen fire has significantly less radiant heat compared to a hydrocarbon fire. Since the flame emits low levels of heat near the flame, the risk of secondary fires is lower.
An explosion cant occur in a tank or any contained location that contains only hydrogen. An oxidizer, such as oxygen must be present in a concentration of at least 10% pure oxygen or 41% air. Hydrogen can be explosive at concentrations of 18.3% to 59% and, although the range is wide, its important to remember that gasoline can present a more dangerous potential than hydrogen, since the potential for explosion occurs with gasoline at much lower concentrations, 1.1% to 3.3%.
For more information on hydrogen safety, codes and standards, please visit the following websites:
As far as ancient CO2 concentrations go, you can review the measurement method and the views of over 1,000 scientists in the U.N. Intergovernmental Panel on Climate Change report of 2007 or see the Wikipedia entry at http://en.wikipedia.org/wiki/Carbon_dioxide_in_the_Earths_atmosphere.