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Take this story in today's NZ Herald for example.

Wow -- high-speed internet over the power grid -- where have I heard that before?

There have been numerous trials of such technology but, for some strange reason, nobody is rolling it out on a nation-wide basis anywhere in the world as far as I can tell.

From what I've been able to gather, it's always the same old story. Power lines are a very noisy environment and the need to jump across transformers at regular intervals makes the whole thing impractical.

Yet every few months we read that someone else is going to spend a small fortune to find this out for themselves and that they're suggesting it will be a technology we'll all be enjoying within a few short years.

Readers Say (updated irregularly) From yesterday... Good use of... - Dennis Learning online... - Simon Previously... Mystery providers join... - Peter usenet blocking... - Max Internet filtering... - Matt R18 content... - Kevin depleted means... - Dwayne News article blocking... - Bob Depleted... - Bill Have Your Say

Then there are OLEDs (organic light emitting devices) which have for nearly two decades promised us bright, colourfull, flexible, efficient displays that will make LCDs and regular CRT-based monitors obsolete.

In this case however, I see that Kodak has released a digital camera with an OLED display -- but everyone else tells us that the technology is still a few years away (as it has been for many years now).

Need another example?

How about electric cars...

Even though I have a 1960's edition of Popular Mechanics which contains a story about the "new" Corvair electric car that will be in production within a decade -- we're still waiting.

What's worse, I see that GE have actually withdrawn what was probably the world's only truly viable electric car made by a major auto manufacturer.

And now Wired magazine expects us to believe that hydrogen will save us from a world where dependency on oil has us handcuffed.

I'm sorry but I don't believe it.

Just in case you aren't aware, hydrogen is a real sod of a gas from several perspectives and isn't actually an energy source at all.

Firstly, although there may be an awful lot of it around (just look at all that water our oceans hold) -- it's very expensive to separate into gaseous form. Liberating hydrogen from water through electrolysis actually involves using more energy than you get back by burning that gas. And you have to ask "where will the energy for the electrolysis come from in the first place?"

The most practical method of producing hydrogen gas is to "crack" a hydrocarbon such as methane or something a little heavier. I believe that much of the hydrogen gas currently supplied is actually a by-product of the refining of crude oil into lighter distillates -- so this won't reduce our dependence on oil very much at all.

Then there's the problem of storing gaseous hydrogen.

Unfortunately the hydrogen molecule is a very small beast -- so small in fact that it has little trouble in slipping between the molecules of other materials. This problem is exacerbated by the fact that in order to store any reasonable amount in a practical space (such as a car's fuel tank) you need to subject it to enormous amounts of pressure. If you've ever noticed how quickly a helium filled balloon deflates overnight you'll understand the effect of tiny moleclues stored under pressure in leaky containers.

And of course -- pressurizing the gas requires the input of more energy.

What's worse -- hydrogen gas has the undesirable effect of making some metals such as steel very brittle and subject to fracture. It's called hydrogen embrittlement and is a real problem in some areas of the engineering industry.

Another storage method showing promise is the use of metallic hydrides - but these are not without their own problems, usually requiring the addition of considerable heat to liberate the hydrogen into a gaseous form, and being very expensive to manufacture.

No, hydrogen is unlikely to become a practical fuel until such time as we manage to come up with a method of producing true fusion.

In the meantime, hydrogen can only really be considered a medium for storing energy we're getting from elsewhere -- and it's not even very good at that.

Despite the promises -- don't expect to see any number of hydrogen-powered vehicles on our roads for many decades to come and don't expect hydrogen to become a real "fuel" at all.

Just more water-vaporware I'm afraid.

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