Monday, September 24, 2007

More on Hydrogen

I could not help but note that at the awards on Friday (love saying that) one of the co-winners was Citroen, in a category with a few other big names doing all sorts of eco stuff.

Thing is, I don't think they do much involving anything other than small cars going a long way on existing fuels. Interesting.

Anyways, last week Jeremy Clarkson was waxing lyrical about hydrogen. This week there are some replies. I was surprised, but as one come from a Professor of Engineering, it is worth keeping one's mind open. Especially this:

It takes slightly more energy to produce hydrogen by splitting water (the only means we have of obtaining it), than is produced when the hydrogen is recombined by burning it in an engine.

I wonder if we'll hear more on this. Doubt we'll see Stuart Rose going to Plan C5 too soon, though.

ADDENDUM -

As it is provoking a worthy and fascinating discussion, here's a new one for fun:

BBC - Hydrogen powered bus is showcased

'Depending on how it is produced, hydrogen fuel is a clean, green source of power that can be easily stored.

The bus is powered by a cell which uses hydrogen as it fuel, cutting out the need for non-environmentally friendly fuels, the university said.'

... depending on how it is produced, then? Which means it is...?

This is all valuable research, to be sure, but the fudge on its current eco-friendliness is a thorn in my view that mars the narrative.

5 comments:

Anonymous said...

Yes, the Professor of Engineering is right. Hydrogen is best thought of as a means of carrying energy, like a battery, rather than as a fuel in its own right.

If we start running cars on hydrogen, we'll need much bigger supplies of electricity to generate the hydrogen........

It's all basic thermodynamics, or you can't have something for nothing!!

Lawrence

Dave said...

Quite correct, the professor and Lawrence are both right.

The hydrogen fuel cell (the storage of hydrogen in a battery type method) is still the equivalent of the philosophers stone though there do appear to be some possible technology breakthroughs on the horizon.

I wonder if the hybrid add-on water splitters that are starting to be sold in the US as diesel (and engine) savers are perhaps a better option. These use the spare power from a vehicles alternator (when the battery is fully charged) to electrolyse water into hydrogen and oxygen which is then squirted in with the fuel mixture. They allegedly give a much cleaner and efficient fuel burn.

I'll sort out a couple of examples and post them on the blog when I get the time.

Anonymous said...

Dave, it will be interesting to see what you find....

There is no 'spare' power from a vehicle alternator. If it is supplying electrical energy, it will burn more petrol or diesel. If you remember the days before cars had electronically-controlled fuel injection, an idling engine slowed down when you turned on the headlights and the rear de-mister.

Some BMWs (e.g. 1 series) now have alternators that are switched off as much as possible to stop wasting this energy. They also switch on when slowing down, so that the car's kinetic energy is converted to electrical energy.

The hydrogen fuel cell is a device which takes hydrogen and oxygen and converts them to electrical energy and water. This is a reverse of the electrolysis of water, where electricity is used to split water to hydrogen and oxygen. The fuel cell is well-established for specialist applications (e.g. spacecraft).

The problem with hydrogen is that you need energy to make it from water in the first place, which is what the professor was reminding us of.

Lawrence

Dave said...

Most vehicle alternators are driven by belts and are therefore consuming energy whether they are charging the battery or not. For 95%+ of the time they are turning (using energy) and producing electrical output that is effectively wasted. The hydrogen splitters I mentioned are now becoming commercially available, at least for commercial trucks.

The Hydrogen Mileage Booster from Energistx is an example of the add-on water splitters that put Hydrogen and Oxygen directly into the diesel injector system.

They claim a 10% to 30% increase in fuel economy, a big reduction in NOX and particulate emissions, and savings on oil changes etc. through reduced oil degradation.

There's also a commercialised system from Globaltech of Canada. Their HFi system claims a guaranteed 10% fuel saving, with improved torque and horsepower and savings on oil degradation.

And this is an article on the use of Aluminium/Gallium alloys that may eventually be used as a Hydrogen on demand generator, thus making fuel cell technology achievable in a practical way - the only fuel that you would have to carry would be water and some metal alloy lumps!

Anonymous said...

Dave,

I was interested to read about the hydrogen generators: I wasn't aware of that technology. With all these claims, it's important to remember that energy can't be created, only converted from one form to another. This is why the power sapped from an engine by an alternator does depend on how much electricity it is generating, not just the fact that it is spinning. Traditionally, an alternator generates at least a small amount of electricity whether it is needed or not, so it's true that this is wasted. However, if the alternator is driving a water splitter to generate hydrogen, it will impose a load on the engine which will increase fuel consumption. However, from what I've seen of those links, this increase in fuel consumption is outweighed by two factors:

One is the burning of the hydrogen, which by the laws of thermodynamics cannot give back all the power that was taken from the engine to generate the hydrogen in the first place. The other factor is that the injection of hydrogen and oxygen is claimed to make the diesel burn more efficiently. It's this effect that enables the whole system to lead to increases in fuel economy.

BMW are now using intelligent alternator control so that once the battery is 80% charged, the alternator is not activated, so there is no electrical load on the engine. When you brake, the alternator is activated and generates electricity, so this electrical load helps to slow the car and charge the battery. In other words the kinetic energy of the car is converted into electrical energy and stored in the battery. I've not been able to find out whether the alternator is physically disconnected with a clutch or whether this control is an electronic effect on the alternator's electro-magnet.

The article about the on-demand hydrogen generator was also interesting, but again emphasises that hydrogen is just a way of storing energy that was generated elsewhere. In that system, the energy input comes from turning the spent aluminium (which has turned into aluminium oxide) back into aluminium. This is not like recycling aluminium cans, but more like smelting aluminium from its ore. Again, this energy will be slightly greater than the energy that the car got from the hydrogen in the first place. The challenge with all of this talk of the "hydrogen economy" is how to generate the extra renewable electricity.

This is perhaps an expanded version of my first post, but an understanding of thermodynamics ie you can't have something for nothing, enables an analysis of all kinds of things.........

Lawrence