What are the drawbacks of incorporating hydrogen into electric powertrains?

[Angry Citizen]

I'm afraid this is bare of proper engineering, but I have a question as a temporary layman (I'm in engineering school now, but still pretty much a freshman). In the Chevy Volt, the powertrain is electric, with a gasoline motor that charges the battery in order to provide an order of magnitude greater range. My question is, why can't this be extended to hydrogen?

I'm thinking about an on-board electrolysis unit that could convert water (with added electrolytes) into hydrogen and oxygen while the battery was being charged, and storing the constituents as a backup fuel similar to the Volt. What are the disadvantages of a hydrogen-augmented electric powertrain? I don't think the electrolysis unit itself would be very heavy or costly. Could it be the necessary current? Water with an electrolytic substance (such as an acid or the addition of a salt) can be electrolyzed fairly easily, but I'm not sure at what rate it can be electrolyzed by a typical household current. Is it the storage of gaseous hydrogen? I'm curious about any research on this subject.

 

[OmCheeto]

I'm afraid this is bare of proper engineering, but I have a question as a temporary layman (I'm in engineering school now, but still pretty much a freshman). In the Chevy Volt, the powertrain is electric, with a gasoline motor that charges the battery in order to provide an order of magnitude greater range. My question is, why can't this be extended to hydrogen?

I'm thinking about an on-board electrolysis unit that could convert water (with added electrolytes) into hydrogen and oxygen while the battery was being charged, and storing the constituents as a backup fuel similar to the Volt. What are the disadvantages of a hydrogen-augmented electric powertrain? I don't think the electrolysis unit itself would be very heavy or costly. Could it be the necessary current? Water with an electrolytic substance (such as an acid or the addition of a salt) can be electrolyzed fairly easily, but I'm not sure at what rate it can be electrolyzed by a typical household current. Is it the storage of gaseous hydrogen? I'm curious about any research on this subject.

I like this idea. Consider your idea stolen.

The wiki article is a pretty good synopsis of the pros and cons; http://en.wikipedia.org/wiki/Hydrogen_vehicle"

But as always, be wary of detractors. They are usually heavily invested in companies that would not benefit from such a wonderful new idea.

I suppose I should give you my thoughts regarding your system.

I would collect the oxygen as well as the hydrogen. It is my understanding that hydrogen burns much hotter than most other fuels, and the nitrogen in air would form pollutants at an alarming rate. Burning pure hydrogen and oxygen would produce no NOx pollutants.

There's a graph on the following page: http://www.alentecinc.com/papers/NOx/The formation of NOx_files/The formation of NOx.htm

that shows NOx production rising rapidly after the temperature reaches 2800°F.

http://en.wikipedia.org/wiki/Adiabatic_flame_temperature" states that hydrogen burns with a flame temperature of 4000°F and 5800°F for air and hydrogen, respectively.

Aha! And from my very first thread:

He did in the paper provide one number I was looking for; the temperature of combustion: 4000'F

Which was for a gasoline engine.

hmmm... Maybe collecting the oxygen isn't that important.

But then again, with a 5800°F flame temperature, the carnot efficiency of the pure H2 O2 engine would be higher. But we'd probably opt for a ceramic turbine. I don't know that a conventional reciprocating metal engine could withstand such temperatures.

And my apologies for overloading on the http://en.wikipedia.org/wiki/Ceramic" quotes;

In the early 1980s, Toyota researched production of an adiabatic ceramic engine which can run at a temperature of over 6000 °F

I'm very lazy.

 

[AlephZero]

What are the disadvantages of a hydrogen-augmented electric powertrain? I don't think the electrolysis unit itself would be very heavy or costly.

Safe storage of a useful amount of hydrogen (or even worse, a 2:1 mixture of H2 and O2) at high pressure would be costly.

Could it be the necessary current? Water with an electrolytic substance (such as an acid or the addition of a salt) can be electrolyzed fairly easily, but I'm not sure at what rate it can be electrolyzed by a typical household current.

From conservation of energy, something that plugs into the normal household supply in the UK is limited to a power of 3kW. So if you wanted a 30kW (40HP) power boost available for 1 hour, ignoring energy losses in the complete system you would need 10 hours charging time. Realistically, probably 50% or 100% longer than that.

That could be changed by developing a new standard for high power electrical connections (and modifying existing house wiring to use it) but that wouldn't be a cheap option, either.