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alternative fuel or what?

#1 User is offline   onoway 

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Posted 2008-October-22, 21:32

I keep running across this stuff. It would seem from these clips that there is something to it, but would like somebody with more expertise in these areas (doesn't take much!) to give their opinion.
http://www.youtube.c...svw_zX8ogM&NR=1
and
http://www.youtube.c...feature=related
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#2 User is offline   effervesce 

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Posted 2008-October-23, 03:21

In essence, they're talking about using hydrogen as fuel, by using electrolysis to convert water into hydrogen gas and oxygen gas.

However- water is not a fuel. Hydrogen and oxygen are the fuel. Water is merely the source for producing the hydrogen and oxygen when supplied with electricity.

There are many major obstacles with implementation of such a so-called hydrogen economy. First of all-we still need fossil fuels. Most electricity is still produced from coal and oil power plants-if we're using electricity for electrolysis, it means that instead of burning the fossil fuel at your car, you're burning it at the power plant. Admittedly, this is beneficial as burning fossil fuels to produce electricity would be more efficient at a power station than your car.

The other main problems- energy density. The problem with hydrogen gas is how to store it-there have been many materials used to adsorb and store hydrogen, but their capacity is so limited that such cars would not be able to travel very far at all.

The energy contained in 1L of gasoline (density 0.75g/ml) is about 60 000 kJ. 1L of hydrogen gas (1g fills 11L) is 10kJ per mol. Therefore to store energy in hydrogen as the same density, you'd have to have the hydrogen at a pressure of 600 atmospheres! Difficult enough to pressurise gas that high in a laboratory, but for a car? Too dangerous. The alternative at the moment is to adsorb hydrogen for storage-but currently only a few (~5%) by weight. So a 'hydrogen battery' weighing 1 tonne would store only about 50kg of hydrogen.

Another problem - ensuring the gas does not escape. You've played with balloons. Hydrogen is extremely difficult to store, as it is very difficult to make a storage container with absolutely no leaks-and very impractical in any case to do so.
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#3 User is offline   matmat 

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Posted 2008-October-23, 10:06

effervesce, on Oct 23 2008, 04:21 AM, said:

The other main problems- energy density. The problem with hydrogen gas is how to store

when you burn hydrogen, you get water back, so presumably these cells could "recycle" the water that is put in.
Problem is, of course, as you point out, that there needs to be an independent power source to dissociate the water, note that the video doesn't tell you how that energy is stored, replenished or how much is needed.
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#4 User is offline   Al_U_Card 

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Posted 2008-October-23, 10:23

There is also the option to mix water with fuel in a still-combustible admixture....but that is specific to certain types of burners for certain types of applications (heating furnaces). H2 is not burned but water is used to increase the heat content of the resultant exhaust gases.
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#5 User is offline   matmat 

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Posted 2008-October-23, 10:26

Al_U_Card, on Oct 23 2008, 11:23 AM, said:

There is also the option to mix water with fuel in a still-combustible admixture....but that is specific to certain types of burners for certain types of applications (heating furnaces). H2 is not burned but water is used to increase the heat content of the resultant exhaust gases.

why would you want to do that for a car? ideally you'd want completely cold exhaust with most of the free energy going into propelling the vehicle...
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#6 User is offline   Al_U_Card 

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Posted 2008-October-23, 14:12

That would be right, as I indicated with

"specific to certain types of burners for certain types of applications (heating furnaces)"
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#7 User is offline   Al_U_Card 

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Posted 2008-October-23, 14:14

matmat, on Oct 23 2008, 11:26 AM, said:

ideally you'd want completely cold exhaust with most of the free energy going into propelling the vehicle...

So we should all be riding "Carnot cycles"? :P
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#8 User is offline   matmat 

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Posted 2008-October-23, 14:19

Al_U_Card, on Oct 23 2008, 03:14 PM, said:

matmat, on Oct 23 2008, 11:26 AM, said:

ideally you'd want completely cold exhaust with most of the free energy going into propelling the vehicle...

So we should all be riding "Carnot cycles"? :P

yes :)
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#9 User is offline   Al_U_Card 

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Posted 2008-October-23, 14:28

I wonder if Carnot was against automobiles.... :P
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#10 User is offline   kenberg 

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Posted 2008-October-23, 19:00

onoway, on Oct 22 2008, 10:32 PM, said:

I keep running across this stuff. It would seem from these clips that there is something to it, but would like somebody with more expertise in these areas (doesn't take much!) to give their opinion.
http://www.youtube.c...svw_zX8ogM&NR=1
and
http://www.youtube.c...feature=related

Pam, you need no special training here. The links you provide tell the following story:

A man with no scientific training has figured out how to run a car on water.
He was offered a billion dollars for his patent but turned it down.
He is now dead, mysteriously poisoned.
The website instructs you to download some stuff for free so that you can learn this billion dollar secret.

Yes, and then there is this bloke in Nigeria with millions salted away in the bank...


I can't tell you about the possibilities for a hydrogen powered car although the name Hindenburg comes to mind. But I can strongly suggest you don't download anything from the suggested source.
Ken
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#11 User is offline   kenberg 

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Posted 2008-November-24, 13:48

A different, but perhaps more credible, discussion of possibilities:


http://www.technolog...m/energy/21536/
Ken
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#12 User is offline   brianshark 

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Posted 2008-November-24, 15:49

Perhaps someone with a greater knowledge of Physics can explain what I'm missing, but surely the energy needed to split water into Hydrogen and Oxygen is identical to the energy released when Hydrogen and Oxygen are combined into water, so noting that every process involves some % of wastage means that you would be better off using the electricty to directly rather than to split water and re-burning the Hydrogen?
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#13 User is offline   awm 

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Posted 2008-November-24, 15:57

brianshark, on Nov 24 2008, 04:49 PM, said:

Perhaps someone with a greater knowledge of Physics can explain what I'm missing, but surely the energy needed to split water into Hydrogen and Oxygen is identical to the energy released when Hydrogen and Oxygen are combined into water, so noting that every process involves some % of wastage means that you would be better off using the electricty to directly rather than to split water and re-burning the Hydrogen?

The main point is that solar power doesn't provide a constant flow of electricity. Sometimes it's cloudy. Sometimes it's dark outside. At these times the solar cells do not produce electricity.

The power grid is very dependent on being able to match the electricity provided to the demand. As long as solar is a very small percentage of our power supply this is not a problem. But imagine if we got a very significant percentage of our energy from solar. We'd need a way to store excess electricity from the times when the solar cells are producing and then rely on this energy when the solar cells are not producing.

So how do we store electricity? There are batteries of course, but these are expensive and not particularly efficient. An alternative approach is to use the electricity to synthesize some kind of chemical fuel which we could then burn for power at the times when solar power is unavailable. Of course, we would want this fuel to be non-polluting, easily stored, and so forth. The suggestion is to use hydrogen as such a fuel, using the electricity from solar cells to divide water into oxygen and hydrogen, then store these substances and recombine them (producing energy) later.

This is not without its problems since, as you say, there is a % wastage at each step of the process. Hydrogen is also not the easiest substance to store in large quantities. And electrolysis is currently not very energy-efficient. But perhaps these things will improve.
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#14 User is online   TylerE 

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Posted 2008-November-24, 15:57

One intriguing idea I've come across is the six cycle engine. Basically a combination of a normal ICE and an expansion steam engine... at the end of the exhaust (4th) stroke, a small amount of exhaust is retained, and a drop of water injected, which instantly flashes to steam, and powers another expansion stroke. Hasn't really been tried on a large scale, but there's no theoretical reason why it shouldn't work, just technical details (changing cam designs, dealing with water in the cylinder, etc).
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#15 User is offline   Gerben42 

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Posted 2008-November-25, 03:29

If you use solar cells for getting your hydrogen, you're not that green as you might think you are. These solar cells need a heck of a lot of energy to produce, and they are mostly not produced in France, where electricity is connected to very low CO2 emissions, but in China, where the opposite is true. If you look at the environmental impact of the different ways to generate electricity, there is a clear division in the total cost for the environment (construction of the plant, running it and long-term effects):

Coal well above 500 g CO2 / kWh
Natural gas about 400 g CO2 / kWh
Solar about 150 g CO2 / kWh
Wood not a lot of CO2 but a lot of NOx.
Wind, Hydro, Nuclear < 25 g CO2 / kWh.

(data provided by the IER, Stuttgart)
http://www.ier.uni-s..._Aalen_2008.pdf, slide 40.
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#16 User is offline   helene_t 

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Posted 2008-November-25, 04:52

brianshark, on Nov 24 2008, 10:49 PM, said:

so noting that every process involves some % of wastage means that you would be better off using the electricty to directly rather than to split water and re-burning the Hydrogen?

You understood it perfectly.

Hydrogen as a fuel is nothing more and nothing less than an alternative electricity storage technology, i.e. an alternative to the batteries used in current electrical and hybrid cars.
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#17 User is offline   Wackojack 

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Posted 2008-November-25, 05:45

An alternative to producing hydrogen from solar is to producing it from wind which as Gerben noted has the lowest CO2 impact. Wind is particularly more attractive in the higher latitudes such as UK and Northern Europe. Build more wind farm and at non peak times in the demand curve for electricity the excess can be used to electrolyse water to produce hydrogen. If a viable hydrogen infrastructure could be introduced it should be environmentally better than a battery infrastrucure.
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#18 User is offline   Gerben42 

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Posted 2008-November-25, 09:24

Wind has the problem that you cannot decide when the energy is produced, it depends on weather. There is no rule that there is wind exactly when the electricity is most needed. For this reason, having more than 10% wind energy is not useful.
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#19 User is offline   onoway 

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Posted 2008-November-25, 09:51

All sorts of stuff being done re housing materials now. I found this site to be interesting. Following some of the associated articles suggests a fair amount of new/pending developments for buildings, the first relating to kenberg's link but from another part of the world.
http://www.inhabitat...-solar-windows/
Windmill farms are not without their own ecological problems, noise being one. The development of better batteries would be very helpful as well, to address the problems with the ones we presently have. I have been trying to follow small developments and found that there are some funky things being done with savonius rotor type and homescale diy projects using recycled plastic barrels for the one and cut pvc pipe for the other. Not sure how much energy either of these will provide..they certainly provide some. We need fridges and stoves that use much less power instead of trying to find ways to feed the suckers. There are some serious questions being raised about the socalled energy efficiency of new appliances.
Still looking for help with the transportation question though..read years ago about a guy in England running his car on the methane from the manure from his flock of chickens, and recently I've seen photos of people supposedly with balloons of methane on motorized bicycles..do people really DO that? Isn't methane apt to explode if it has access to air and there is any sort of spark?
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#20 User is offline   Wackojack 

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Posted 2008-November-25, 10:22

Gerben42, on Nov 25 2008, 10:24 AM, said:

Wind has the problem that you cannot decide when the energy is produced, it depends on weather. There is no rule that there is wind exactly when the electricity is most needed. For this reason, having more than 10% wind energy is not useful.

Yes, there is some truth in what you say. However,
1. If you have your wind generators scattered over a sufficient geographical area, and all feeding into a common electricity grid, then there will always be at least some wind generators providing power. Thus even if we ignore hydrogen produced by surplus wind generation, we should be able to safely have more than 10% of our electricity produced by this means.

2. If we can build more wind generators and get into a hydrogen economy, we have a bonus. At off peak times, which incidentally can be as little as a third of peak demand, we have a huge potentioal to increase the utilisation of the installed windpower, by electrolysing water to produce hydrogen.

Ok you might give me a scenario of a large anticyclone over Northern Europe where UK, Ireland, Holland, Denmark, Germany, Skandinavia are all becalmed. However, the European electricity grid is interconnected to the whole of Southern and Eastern Europe. Thus we should argue for a greater rather than a lesser proportion of wind power. We also might put in solar generation in to North Africa and connect it to the European grid by dc cables. Iceland too with its abundance of thermal energy could be likewise connected. (and thus helping its broken economy)
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