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Author Topic: Hydrogen cars with built in water splitters?  (Read 5073 times)

Offline McKay

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Hydrogen cars with built in water splitters?
« on: 21/01/2015 02:16:13 »
With the recent announcement of a new hydrogen car, that seems to be getting pretty popular, I am wondering - couldnt they have built in water slitter tech so the cars can be charged up BOTH from the specialized stations that are yet to be built (faster) and/ or any electric power outlet (charging at home overnight and using the infrastructure we already have)?
Would it be terribly impractical somehow? Or expensive? Or they already work that way and I just missed that?


 

Offline CliffordK

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Re: Hydrogen cars with built in water splitters?
« Reply #1 on: 21/01/2015 04:19:12 »
One could potentially have a hydrogen generator at home.  Perhaps separate from the car.  However, one of the issues with hydrogen is storage. 

Currently hydrogen is stored in one of two manners (or perhaps a hybrid between the two). 

Liquid Hydrogen, -253C at low pressure
High pressure cylinders, perhaps 3000 PSI at room temperature.

Acetylene, on the other hand readily dissolves in acetone, and is a gas that is typically stored at low pressures at room temperature. 

I think the Holy Grail of Hydrogen storage would be to dissolve it in something like is done with acetylene/acetone, and have high capacity, low pressure storage. 

Anyway, until the hydrogen transport/storage issues are resolved, I doubt we'll see widespread adoption of hydrogen as a fuel. 

What this means for home generation is that it would not be a simple machine to generate and liquefy hydrogen at -253C, or to pressurize it to thousands of PSI.

The cost of hydrogen would also have to include the energy cost of pressurizing/liquefying it.

In a region with excess free energy (solar, wind, hydroelectric), it would make sense to dump excess power into producing hydrogen.  In regions with a power deficit, and generate their power using petroleum, it would be inefficient to use coal to make electricity, then electricity to make hydrogen.
 

Offline evan_au

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Re: Hydrogen cars with built in water splitters?
« Reply #2 on: 21/01/2015 09:49:34 »
Researchers have studied one intermediate option for some years: absorb the hydrogen gas into a metal sponge, where it binds to the metal at a much lower pressure than would be required to store the same amount of hydrogen as a gas.

More options at: http://en.wikipedia.org/wiki/Hydrogen_storage#Metal_hydrides
...but despite its advantages, Hydrogen still struggles to match teh convenience of hydrocarbon fuels.
 

Offline alancalverd

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Re: Hydrogen cars with built in water splitters?
« Reply #3 on: 21/01/2015 12:57:25 »
Easy. Attach the hydrogen to some carbon atoms, burn the whole lot, and plant trees to recycle the resulting CO2 and H2O into more hydrocarbon fuel, using free solar energy.
 

Offline chiralSPO

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Re: Hydrogen cars with built in water splitters?
« Reply #4 on: 21/01/2015 15:33:09 »
Easy. Attach the hydrogen to some carbon atoms, burn the whole lot, and plant trees to recycle the resulting CO2 and H2O into more hydrocarbon fuel, using free solar energy.

I agree that it seems the simplest way to store hydrogen is in compounds such as hydrocarbons. It wouldn't make sense to do it in a car, but we have the technology to react hydrogen directly with CO2 to make hydrocarbons (no trees needed--at least as far as C management goes, if all our fuel is made from CO2--of course there are other reasons we need trees). Currently this method is far more expensive than refining what we can dig out of the ground, but I think (hope) this will change in the next 10 years or so as it becomes more expensive to extract fossil fuels (especially if there is an economic mechanism to account for environmental harm) and cheaper to make our own fuels as technology advances and when economies of scale manifest.

A point on HHO generators. These devices are very cheap, but typically convert only 5065 % of the electrical energy into chemical fuel (the rest is heat waste, and not very useful at that). Additionally, HHO gas (Brown's gas) must be used as it is produced, it's a bad idea to build up any significant quantity of this stoichiometric mixture of hydrogen and oxygen, and store it for any period of time (don't even think of compressing or liquifying it!) If storage is what you're after, an electrolyzer that separates the hydrogen and oxygen is required, and these are significantly pricier.

Zinc-air fuel cells are another option: Have a factory somewhere converting zinc oxide to zinc powder using some source of renewable energy. Fill up your tank with a slurry of said zinc pellets, and convert them into zinc oxide as you drive, then at the fill station the zinc oxide is drained while the zinc is added.

This might not be that feasible, but there are people working on it now. Zinc is fairly heavy, only storing 5.3 MJ/kg (compared to 142 MJ/kg for H2, or 46.4 MJ/kg for gasoline), but it is also very dense so it stores 38 MJ/L (vs 8.5 MJ/L for liquified H2, or 34.2 MJ/L for gasoline). Also if we account for the mass of whatever system is used for storing hydrogen, and the mass difference between combustion engine and fuel cell/electric motor I think the numbers work out even better for zinc.
 

Offline CliffordK

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Re: Hydrogen cars with built in water splitters?
« Reply #5 on: 21/01/2015 16:58:01 »
One of the things that has come up is that electricity usage tends to be cyclical.  Yet power generation is often more steady state, without necessarily any good method for energy storage. 

So, for example, wind power generates energy when the wind is blowing, no matter whether it is day or night.  Hydroelectric power generation could be varied by the time of day (and makes a natural storage medium), but in many cases the river flow must be maintained throughout the day and night.  Especially during flood stages, downstream river capacity may not allow cyclical flows.  Nuclear plants also function at a steady state. 

So, hydrogen generation would be natural for off-peak energy usage.

Yes, mixed gases (HHO) or the actual chemicals, (2H2 + O2)  would be extremely dangerous to pressurize.  However, in electrolysis, the hydrogen and oxygen can be separated at the anode & cathode to provide fairly pure gases which can be purified and stored.
 

Offline CliffordK

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Re: Hydrogen cars with built in water splitters?
« Reply #6 on: 21/01/2015 17:29:14 »
Currently this method is far more expensive than refining what we can dig out of the ground, but I think (hope) this will change in the next 10 years or so as it becomes more expensive to extract fossil fuels (especially if there is an economic mechanism to account for environmental harm) and cheaper to make our own fuels as technology advances and when economies of scale manifest.
The USA (and presumably the world) is currently experiencing an oil boom/glut, and thus the lowest oil prices in a decade, or since about the time of the Katrina Hurricane. 

This would be a good time for the USA to start tinkering with the fuel taxes to encourage conservation.  However, new taxes are unpopular, and we're heading into a major new election cycle (yes...  we just had the last ones).  I doubt the political climate in Washington DC will allow for adjusting the fuel taxes to compensate for the increased production and conservation goals.

"Peak Oil Production" has been an elusive figure, and may well be decades out, but it may depend on whether the current flat trend of oil consumption continues, or if there is a spike in consumption just before the peak.

Anyway, I don't see a rapid drop in oil production within the next decade.  Perhaps by the half century mark (2050).
 

Offline David Cooper

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Re: Hydrogen cars with built in water splitters?
« Reply #7 on: 21/01/2015 18:08:51 »
I'd rather see hydrogen used as an industrial energy storage system. It looks as if new battery technologies will soon allow rapid charging which will enable electric cars to stop periodically for a rapid recharge or even to pick up a charge from the road while driving at full speed on special recharging stretches, and that will wipe out all rival technologies.
 

Offline wolfekeeper

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Re: Hydrogen cars with built in water splitters?
« Reply #8 on: 25/01/2015 00:25:09 »
My current view is that there's nothing particularly special about hydrogen, it's pretty much just a battery-type storage system (technically a fuel cell, which is pretty much the same thing), and mostly a very inefficient and rather awkward one.
 

Offline chiralSPO

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Re: Hydrogen cars with built in water splitters?
« Reply #9 on: 25/01/2015 01:22:15 »
There are three special things about hydrogen that make it attractive as a fuel:

1) It is very abundant (~10% of ocean's mass and >70% of matter in universe is H by mass)

2) On a "per mass" basis it has unmatched energy density (142 MJ/kg, that's three times that of gasoline or lithium)

3) the only combustion product is water, which is non-corrosive, non-toxic and environmentally benign

There are plenty of reasons that is not an ideal fuel though, for instance: it is relatively expensive to store and transport, forms explosive mixtures with air across a very wide range (1860% in air can explode, and 494% can burn), and easy to ignite.
 

Offline wolfekeeper

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Re: Hydrogen cars with built in water splitters?
« Reply #10 on: 25/01/2015 12:22:14 »
There are three special things about hydrogen that make it attractive as a fuel:

1) It is very abundant (~10% of ocean's mass and >70% of matter in universe is H by mass)
Abundance is not an advantage. It's not even particularly low cost by kg. Strike 1.
Quote
2) On a "per mass" basis it has unmatched energy density (142 MJ/kg, that's three times that of gasoline or lithium)
But it has one of the lowest volumetric energy densities; and that's if anything, more important, and it sucks. Strike 2
Quote
3) the only combustion product is water, which is non-corrosive, non-toxic and environmentally benign
even water is pretty f'ing corrosive in fact, and hydrogen embrittles metals as well. Strike 2b; I won't give that a whole strike, but it's worth noting.
Quote
There are plenty of reasons that is not an ideal fuel though, for instance: it is relatively expensive to store and transport, forms explosive mixtures with air across a very wide range (1860% in air can explode, and 494% can burn), and easy to ignite.
yeah!

Also the fuel cells that use it are expensive and have a short life. So the battery is expensive and don't last. And... strike 3, we're out.

Elon Musk is a smart guy and actually used to work on this kind of stuff, he thinks it's sh1t. I'm inclined to believe him. It's a multiple breakthroughs away from the prime time. There are several show stopping problems away from it being prime time.
 

Offline alancalverd

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Re: Hydrogen cars with built in water splitters?
« Reply #11 on: 25/01/2015 16:15:11 »
I agree that it seems the simplest way to store hydrogen is in compounds such as hydrocarbons. It wouldn't make sense to do it in a car,

Don't know about you, but I'm currently running a house, two cars, a tractor, an aeroplane and several garden tools on liquid hydrocarbons, and planning a new medical facility with diesel generators too (cheaper and more reliable than mains electricity!) Can't think of a more sensible fuel.
 

Offline chiralSPO

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Re: Hydrogen cars with built in water splitters?
« Reply #12 on: 25/01/2015 16:17:43 »
Context and parsing, alancalvard. Context and parsing.

I agree that it seems the simplest way to store hydrogen is in compounds such as hydrocarbons. It wouldn't make sense to do it in a car, but we have the technology to react hydrogen directly with CO2 to make hydrocarbons...

EDIT: in case it wasn't clear--I was saying that it does make sense to use hydrocarbon fuels in a vehicle, but not to make hydrocarbon fuels in a vehicle.
« Last Edit: 25/01/2015 17:25:49 by chiralSPO »
 

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Re: Hydrogen cars with built in water splitters?
« Reply #12 on: 25/01/2015 16:17:43 »

 

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