Comments on: Hydrogen On Demand?

By: Blue Crab Boulevard » The Catch

Blue Crab Boulevard » The Catch — Sat, 19 May 2007 20:46:46 +0000

[...] I noted a report yesterday about a researcher at Purdue University who claims to have discovered a way to generate hydrogen on demand. I noted that I had a number of reservations about the practicality of the process. Some astute readers also chimed in with a number of very sharp comments that are worth reading. Well, the researcher is making even more extravagant claims today, including one that the man is keeping him down, man. A Purdue University engineer and National Medal of Technology winner says he's ready and able to start a revolution in clean energy. [...]

By: NortonPete

NortonPete — Sat, 19 May 2007 00:24:11 +0000

WoodSprite,
Thanks for the informative post, your points about the burning of aluminum to produce a fuel, hydrogen , are well taken.
Lets take a quick energy break and remember from Physics 101 that Energy cannot be created or destroyed, it may be transformed from one form to the other.
The sun stored a tremendous amount of energy in what became oil. The sun also stores energy in wood and plants (ethanol) but to a lesser extent.
Unless we look to the nuclear world of stored energy , oil will always be the most highly concentrated energy source . We should just use it wisely.

By: Woodsprite

Woodsprite — Fri, 18 May 2007 23:13:55 +0000

What they are really doing is burning aluminum to produce hydrogen which is then being used to fuel the end device. If that device is a fuel cell, then you have a rather expensive battery powered by aluminum and water. Probably a lighter and more dense storage mechanism than a traditional battery, but given the energy requirements of aluminum production I would be shocked if you could get out anywhere near the amount of energy that went into creating the aluminum in the first place.

There are two things people seem to forget when talking about hydrogen as a fuel.

First is that it is not an energy source. An energy source is some resource which provides energy in it’s natural state. Free hydrogen isn’t found anywhere on earth, it’s always bonded to something else. Hydrogen as described in articles like this is an energy transport and storage mechanism. It’s a way to move the energy stored by breaking the hydrogen free of it’s chemical bonds (via the aluminum in this case) to where it will be used (fuel cell, piston engine, etc).

The second thing people forget is evidenced by this quote: “Hydrogen is seen as the ultimate in clean fuels, especially for powering cars, because it emits only water when burned.” That’s only true if pure hydrogen and oxygen is being burned. Burn it with regular air under any kind of compression (say a car engine) and you’ve introduced lots of nitrogen into the equation. Now you have not just water but lots of NOx compounds, some O3 (ozone), and more than a few COx compounds from burning the stuff which is lubricating the motor.

By: NortonPete

NortonPete — Fri, 18 May 2007 20:06:45 +0000

For years while I was a bad juvenile, my friends and I would get a jug of muriatic acid and a roll of aluminum foil.

You fill a glass bottle with the acid and drop in a rolled up piece of aluminum foil. A fast reaction producing Hydrogen gas would occur. We would capture it with a balloon over the neck of the bottle.

Now we had a balloon that was lighter than air. So you tie a string to the balloon and light the sting and let it go.

Mini-Hindenburgs , great fun until you were hit in the face with acid from a exploding bottle which got extremely hot.

I hope this helps with alternate energy research.

By: Gaius

Gaius — Fri, 18 May 2007 18:34:13 +0000

The aluminum is not acting as a catalyst – it is being consumed in the reaction. But the energy equations for the entire cycle – including producing the feedstock would need to be scrutinized very carefully.

By: BubbaB

BubbaB — Fri, 18 May 2007 18:24:41 +0000

Hmm… I wonder what the energy content of water is? And I wonder what that is compared to the energy content of gasoline. I would venture to guess that gasoline has a much higher energy density than water.

The aluminum is working as a catalyst for the chemical reaction (separating water into its constituent hydrogen and oxygen molecules.) Catalysts are great – they reduce the activation energy required to cause a chemical reaction.

Unfortunately, they don’t reduce the overall amount of energy required to cause a chemical reaction. Breaking apart water is an endothermic reaction – it takes energy to do it. That energy is then stored up in the H-H and O-O bonds (if I remember my chemistry.)

So, where is the energy coming from to break the bonds apart? The environment? Great, we go from car engines that we can’t touch, due to the fact that they will severely burn you, to car engines that we can’t touch, due to the fact that they will cause severe frost-bite.

And how many gallons of water will it take to equal one gallon of gasoline? (Although, car engines are very inefficient – maybe fuel cells would be more efficient.)