hydrogen hot air?
- Thread starter loublou
- Start date
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2scoops0406
Yes it does
However, there are advantages:
1) A petrol engine is something like 20% efficient, 20% of the energy in the fuel is converted into forward motion. Diesel is slightly more efficient. However, a power station can be considerably MORE efficient than either. Producing hydrogen is a 90+% efficient process, and fuel cell cars have been demonstrated that offer 95% efficiency. So, overall, a power station producing hydrogen that then goes in a car, will be more efficient than just burning the petrol in the car. Therefore "using the energy direct" might be less efficient overall.
2) Renewable energy. If you produce your hydrogen with a renewable energy source then you aren't burning fossil fuels at all. Nuclear power will work too, but isn't as nice as a dam or a windmill.
3) Versatility. A petrol engine works on petrol, a diesel engine works on heavy oil. But, you can use pretty much anything to provide electricity for producing hydrogen.
1) A petrol engine is something like 20% efficient, 20% of the energy in the fuel is converted into forward motion. Diesel is slightly more efficient. However, a power station can be considerably MORE efficient than either. Producing hydrogen is a 90+% efficient process, and fuel cell cars have been demonstrated that offer 95% efficiency. So, overall, a power station producing hydrogen that then goes in a car, will be more efficient than just burning the petrol in the car. Therefore "using the energy direct" might be less efficient overall.
2) Renewable energy. If you produce your hydrogen with a renewable energy source then you aren't burning fossil fuels at all. Nuclear power will work too, but isn't as nice as a dam or a windmill.
3) Versatility. A petrol engine works on petrol, a diesel engine works on heavy oil. But, you can use pretty much anything to provide electricity for producing hydrogen.
B
B.O.B DOLE
loublou said:
your not after making a bomb are you?
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First law of thermodynamics: you will get as much energy out as you put in.
Second law of thermodynamics: you will always get less USEFUL energy out than you put in.
That second law is the important one where engines are concerned. Fuel is chemical energy stored in a useful form but if you burn it you end up with the lowest grade of energy which is heat. There is no way to turn it all back into the high grade kinetic energy you want and so you throw most of it away. AdamW says you throw away 80% and I can believe it.
The fuel cell is a great improvement on the heat engine because it turns chemical energy directly into high grade electrical energy. Moreover, hydrogen is a very clean fuel - the exhaust is pure water - but the question remains, where do you get it. On this planet you are most likely to get it from water. Environmentalists should approve of that bit. You start with water and you finish with water. The problem lies with that other ingredient you have to put in, namely energy.
A good old fashioned way of splitting water is to pass it over hot carbon. The result, a mixture of hydrogen and carbon monoxide, was known as water gas but here we have a double whammy: where do you get the carbon and what do you do with all that nasty CO? As if that isn't enough, the reaction is endothermic; you have to put heat in as well. The old solution to this was to alternate the water with air. This exothermic reaction made producer gas (mostly CO) and bumped up the temperature ready for the next batch of water. Look carefully at this process and you'll see that all you're really doing is burning carbon!
So what happens if we simply heat up water vapour until the molecules split? That's OK in theory. It happens at about 6000 degrees!! Centigrade or Kelvin? - who cares. I can imagine waste heat from a fusion ring being used for this purpose but that isn't going to happen anytime soon. Neither is it practical to import hydrogen from Jupiter.
The real answer is of course electrolysis and so we come to the real question. How do we generate the electricity to make the hydrogen to put in the fuel cells that will power our electric cars? Conventional power stations burn fuel to make heat to drive heat engines - and most of the energy gets thrown away. You might as well burn the fuel in the car but how do you make the fuel in the first place?
I know I've said this before but I'll repeat it anyway. There are only three sources of energy available to us: solar power, geothermal power and tidal power. In the far distant future we might figure out how to tap the ultimate power source which is gravity. As every Trekky knows, Romulan engines are powered by an artificial quantum singularity. In simple terms you make a diddy little black hole and drop stuff in. It's a great way to get rid of rubbish but there is a problem and it's not just that we don't know how to make one. As every Trekky also knows, those things can never be shut down. Would you want one in your town?
Getting back to life as we know it ---
As AdamW points out, there are many ways, mostly solar in origin, to generate 'clean' electricity which could be used to make hydrogen. Unfortunately they're not exactly compact. One way of generating huge amounts of electricity is to cover huge areas of the Earth's surface with solar cells. But this is looking at the problem the wrong way. Why not split OXYGEN from water and see what's left? The advantage to this method is that everything we need to do it is already out there - and has been for 600 million years!
Instead of hydrogen powered cars we should be looking at alcohol powered cars. Plants make sugars from water, CO2 and light. Fungi turn sugar into alcohol. OK so they both take a little of the energy for themselves but that's the way it goes. Remember the second law?
Alcohol is a very clean fuel. The exhaust is water and CO2 but no more than the plants took in the first place. As with hydrogen you can drink the exhaust and what's more, unlike hydrogen, you can also drink the fuel!
PS: The day may come when we have to import hydrogen from Jupiter. If the human population continues to grow we will run out of the stuff. We will end up with a monolithic city many miles thick covering the entire planet's surface. What do we do when the oceans have run dry? We could try splitting silicon and oxygen atoms but we'll need that Romulan technology to do it because nuclear fusion won't work.
PPS: What do we do when we've cleaned out Jupiter - and all the other gas planets? Time for a rethink on birth control perhaps!
Second law of thermodynamics: you will always get less USEFUL energy out than you put in.
That second law is the important one where engines are concerned. Fuel is chemical energy stored in a useful form but if you burn it you end up with the lowest grade of energy which is heat. There is no way to turn it all back into the high grade kinetic energy you want and so you throw most of it away. AdamW says you throw away 80% and I can believe it.
The fuel cell is a great improvement on the heat engine because it turns chemical energy directly into high grade electrical energy. Moreover, hydrogen is a very clean fuel - the exhaust is pure water - but the question remains, where do you get it. On this planet you are most likely to get it from water. Environmentalists should approve of that bit. You start with water and you finish with water. The problem lies with that other ingredient you have to put in, namely energy.
A good old fashioned way of splitting water is to pass it over hot carbon. The result, a mixture of hydrogen and carbon monoxide, was known as water gas but here we have a double whammy: where do you get the carbon and what do you do with all that nasty CO? As if that isn't enough, the reaction is endothermic; you have to put heat in as well. The old solution to this was to alternate the water with air. This exothermic reaction made producer gas (mostly CO) and bumped up the temperature ready for the next batch of water. Look carefully at this process and you'll see that all you're really doing is burning carbon!
So what happens if we simply heat up water vapour until the molecules split? That's OK in theory. It happens at about 6000 degrees!! Centigrade or Kelvin? - who cares. I can imagine waste heat from a fusion ring being used for this purpose but that isn't going to happen anytime soon. Neither is it practical to import hydrogen from Jupiter.
The real answer is of course electrolysis and so we come to the real question. How do we generate the electricity to make the hydrogen to put in the fuel cells that will power our electric cars? Conventional power stations burn fuel to make heat to drive heat engines - and most of the energy gets thrown away. You might as well burn the fuel in the car but how do you make the fuel in the first place?
I know I've said this before but I'll repeat it anyway. There are only three sources of energy available to us: solar power, geothermal power and tidal power. In the far distant future we might figure out how to tap the ultimate power source which is gravity. As every Trekky knows, Romulan engines are powered by an artificial quantum singularity. In simple terms you make a diddy little black hole and drop stuff in. It's a great way to get rid of rubbish but there is a problem and it's not just that we don't know how to make one. As every Trekky also knows, those things can never be shut down. Would you want one in your town?
Getting back to life as we know it ---
As AdamW points out, there are many ways, mostly solar in origin, to generate 'clean' electricity which could be used to make hydrogen. Unfortunately they're not exactly compact. One way of generating huge amounts of electricity is to cover huge areas of the Earth's surface with solar cells. But this is looking at the problem the wrong way. Why not split OXYGEN from water and see what's left? The advantage to this method is that everything we need to do it is already out there - and has been for 600 million years!
Instead of hydrogen powered cars we should be looking at alcohol powered cars. Plants make sugars from water, CO2 and light. Fungi turn sugar into alcohol. OK so they both take a little of the energy for themselves but that's the way it goes. Remember the second law?
Alcohol is a very clean fuel. The exhaust is water and CO2 but no more than the plants took in the first place. As with hydrogen you can drink the exhaust and what's more, unlike hydrogen, you can also drink the fuel!
PS: The day may come when we have to import hydrogen from Jupiter. If the human population continues to grow we will run out of the stuff. We will end up with a monolithic city many miles thick covering the entire planet's surface. What do we do when the oceans have run dry? We could try splitting silicon and oxygen atoms but we'll need that Romulan technology to do it because nuclear fusion won't work.
PPS: What do we do when we've cleaned out Jupiter - and all the other gas planets? Time for a rethink on birth control perhaps!
Brazil have had alcohol-fuelled cars for decades. It started as a drive for energy independence, reducing their need to trade with oil-producing countries. They grow sugar cane, ferment the sugar, and then distill it (using, amongst other things, the remnants of the canes to provide heat for the fractioning process).
Now they are using more fossil fuels, but it looks like they will be moving back to alcohol.
The great thing is, a petrol-engined car can run on ethanol pretty easily. In Brazil you can buy dual-fuel cars that run on petrol, ethanol, or a mixture of the two.
There was work on fuel cells that passed methanol over a catalyst to form hydrogen and CO2, but they are working on ones that can use methanol directly now. I think they are still at the lab stage though, but then aren't all fuel cells that are destined for consumer use!
Now they are using more fossil fuels, but it looks like they will be moving back to alcohol.
The great thing is, a petrol-engined car can run on ethanol pretty easily. In Brazil you can buy dual-fuel cars that run on petrol, ethanol, or a mixture of the two.
There was work on fuel cells that passed methanol over a catalyst to form hydrogen and CO2, but they are working on ones that can use methanol directly now. I think they are still at the lab stage though, but then aren't all fuel cells that are destined for consumer use!
About 30 years ago I read something about a carbonate fuel cell. It used carbon electrodes in molten sodium carbonate electrolyte. The drawback was that you had to get it up to about 700 deg C before it would work. The advantage was that thanks to the elevated temperature you didn't need any expensive catalysts. It was claimed to run on any hydrocarbon fuel in addition to hydrogen so I don't see why it shouldn't take alcohol. I wonder what happened to it?
That mention of catalysts reminds me of something else. It's usually platinum. If this is so and we're going to be turning out fuel cells by the billion I hope there's a plentiful supply of the stuff.
That mention of catalysts reminds me of something else. It's usually platinum. If this is so and we're going to be turning out fuel cells by the billion I hope there's a plentiful supply of the stuff.
Well, catalytic converters in cars use platinum as the catalyst. Also rhodium or palladium work. If we have enough platinum to make cats for cars, then a fuel cell car could put the platinum to use catalysing the fuel. No need to catalyse emissions if it is water and carbon dioxide! 
Not forgetting that you can grow rape oil for use in diesel engines.
Also if you want to get to the nitty gritty of things it would be far better to burn all these fuels in a power station and have all cars powered by electricity supplied by the power stations, thern you would have maximum efficientsy and minimum waste and the fuel saving would be so huge that oil would be basically worthless----trouble is when that happens it defeats the expense to the change over but it will come one day.
Also if you want to get to the nitty gritty of things it would be far better to burn all these fuels in a power station and have all cars powered by electricity supplied by the power stations, thern you would have maximum efficientsy and minimum waste and the fuel saving would be so huge that oil would be basically worthless----trouble is when that happens it defeats the expense to the change over but it will come one day.
When we can fully sustain ourselves with crop oils, rather than just mixing in 5% or so to make "bio-diesel", then petrol and diesel will no doubt be reserved for classic cars. Much like leaded petrol is now.
The quicker we can get such technologies going the better. The developing countries that are looking to spew out as much pollution as they can whilst we try to cut ours might find they can grow and refine biological fuels more cheaply than using crude.
I'm surprised the US with all its land doesn't grow more fuel crops. And what about Oz? Millions of square miles, half a dozen villages, generally held to be very much into environmentalism, yet they haven't planted a few billion acres of oilseed rape.
The quicker we can get such technologies going the better. The developing countries that are looking to spew out as much pollution as they can whilst we try to cut ours might find they can grow and refine biological fuels more cheaply than using crude.
I'm surprised the US with all its land doesn't grow more fuel crops. And what about Oz? Millions of square miles, half a dozen villages, generally held to be very much into environmentalism, yet they haven't planted a few billion acres of oilseed rape.
How's this for a rather different kind of crop oil. Since mineral oil is formed from the decay of marine organisms can we speed the process up. Imagine a fermentation tank full of plankton churning out hydrocarbon oil as good as any that comes out of the ground. Would it work or would the RSPCA object?
It's a difficult one. Some plankton are members of Kingdom Animalia, others are Kingdom Protista (like amoebas). All plankton means is that it is an organism that can't swim horizontally about in the water.
So, provided you stick to the protists you will have no argument.
As to the animal ones, they don't actually have a nervous system. So, they can't feel pain or distress. Therefore, whilst some may have moral objections, it wouldn't technically be cruel (this is why you are allowed to eat live oysters: no central nervous system, just a neural net).
So, provided you stick to the protists you will have no argument.
As to the animal ones, they don't actually have a nervous system. So, they can't feel pain or distress. Therefore, whilst some may have moral objections, it wouldn't technically be cruel (this is why you are allowed to eat live oysters: no central nervous system, just a neural net).
AdamW said:
Adam if America and Canada switched from growing food to producing crop fuel for their cars which they are perfectly entitled to do by the way---half the third world would starve, even your bread is made with grain from the states or Canada as it is far superior to anything we grow---something to do with the weather
Oz is mainly desert or a waste of time regards agriculture and it takes 6 or 12 acres of rape to power a car for the year--sorry cant remember which.
Running a car on any kind of fuel is a pure and inefficient waste of energy and money, electric re-chargable cars are the only answer
I can't argue with that. We should all try to travel fewer car miles. I know that some people have little choice but there are also those who will happily drive round the corner to buy a bottle of gin. For what it's worth I go to work on a bike.
You thought right. Almost everything that lives in the ocean ultimately sinks to the bottom where it joins the detrital ooze. That's a fancy name for a bog. There it is consumed by anaerobic bacteria to form, amongst other things, hydrocarbons. At 4 deg C this is a slow process but maybe we can speed it up - or not!
Fine, but how do you generate the electricity? This just about brings us back to where we started.
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