Diesel from Water?

alfadriver wrote:

curtis73 wrote:

codrus wrote:

alfadriver wrote: Even liquified, H2 does not store that much potential energy.

By weight liquid H2 is the most energy-dense fuel there is, that's why high performance rockets use it. The problem is the volume and the infrastructure to handle cryogenic fuels, so it really doesn't scale down to cars very well.

The other problem (other than the insanely explosive nature of hydrogen) is finding a source. You either spend as much energy getting it from water as you get when you re-combine it, or get it from fossil fuels.

For THIS particular example, the H2 is coming from water. As pointed out in the article. Using renewable sources, or course.

Water is not a source for H as fuel. It can't be. It takes as much (or more) energy to separate it as you get back when burning it. Hydrogen fuel from water is equivalent to taking car exhaust and turning it back into gasoline.

If you think about it, water is the exhaust. It is the result of hydrogen burning (combining with oxygen). Converting it back into fuel requires adding back into it all of the energy you just got out of it.

My point is... even though they used renewable energy to split the hydrogen off the water, all they've done is store that potential energy in the hydrogen's volatility. Why not use that renewable energy directly and not waste it making complex HCs?

Its like a slinky on the steps. Water is like a slinky at the bottom. They are adding all kinds of energy to get it to the top of the steps just to let it fall back down. Why not use the energy that you would waste transporting a slinky and just put it in storage?

Because then they couldn't get the government research grants to play with cool toys.

It's also a storage issue. It's always a storage issue. Energy density and ease of transport. Liquid = easy, $. Gas = not as easy as liquid, $$. Electrical = hard, $$$.

As is often the case in this sort of discussion, it seems that people are talking at cross-purposes.

Hydrogen is a fuel, because you can operate a vehicle by burning it. It is not, however, a practical chemical energy source, because you can't go dig it out of the ground in elemental form (i.e., H2). Hydrogen that's in water is H2O -- it's already "burned", and you won't net more energy out of it by taking H2O apart and putting it back together again, that's basic thermodynamics.

(I say "practical" because something like 80% of the matter in the universe is elemental hydrogen, it's just that it's out there, not down here. I say "chemical" because nuclear fusion of some forms of hydrogen is certainly an energy source, we just haven't got the bugs worked out of that yet).

If you want to power an infrastructure, you need energy sources. There's basically three ways of producing the large "base load" given our current tech -- burning fossil fuels, hydro power from dams, and nuclear fission. Solar, wind, wave, geothermal, etc are niche technologies that can't (at present) scale up to base load levels. Hydro is nice, but largely speaking we've built dams on all the good sites already, so there's not much room for growth there.

So if you want to power a transportation infrastructure without using fossil fuels, you pretty much have to generate that energy using nuclear power. Since it's not really practical to swap a nuclear power plant under the hood of a Miata, you need to use the stationary plant to make something energy-intensive that you can use to power it. You can do this with electricity and batteries (with their associated cost and weight), or you can use that electricity to make a chemical fuel. H2 is easy to make with nuclear power, but it sucks to transport and store it. Hydrocarbons are harder make, but easier to transport.

codrus wrote: As is often the case in this sort of discussion, it seems that people are talking at cross-purposes. Hydrogen is a fuel, because you can operate a vehicle by burning it. It is not, however, a practical chemical energy source, because you can't go dig it out of the ground in elemental form (i.e., H2). Hydrogen that's in water is H2O -- it's already "burned", and you won't net more energy out of it by taking H2O apart and putting it back together again, that's basic thermodynamics. (I say "practical" because something like 80% of the matter in the universe is elemental hydrogen, it's just that it's out there, not down here. I say "chemical" because nuclear fusion of some forms of hydrogen is certainly an energy source, we just haven't got the bugs worked out of that yet). If you want to power an infrastructure, you need energy sources. There's basically three ways of producing the large "base load" given our current tech -- burning fossil fuels, hydro power from dams, and nuclear fission. Solar, wind, wave, geothermal, etc are niche technologies that can't (at present) scale up to base load levels. Hydro is nice, but largely speaking we've built dams on all the good sites already, so there's not much room for growth there. So if you want to power a transportation infrastructure without using fossil fuels, you pretty much have to generate that energy using nuclear power. Since it's not really practical to swap a nuclear power plant under the hood of a Miata, you need to use the stationary plant to make something energy-intensive that you can use to power it. You can do this with electricity and batteries (with their associated cost and weight), or you can use that electricity to make a chemical fuel. H2 is easy to make with nuclear power, but it sucks to transport and store it. Hydrocarbons are harder make, but easier to transport.

^^ This.

And I will support the "playing with government money and research grants" for a while, but its getting old for me. I like that scientists are experimenting and (in the process) might come up with the next big technology, but it seems like its getting a little more in the fluffy realm and less in the real direction of scientific progress. Don't get me wrong... I applaud the intellectual benefits of experimentation strictly for the practice; like playing chess or performing art to sharpen your mind, but it does reach a point of excess

In this case, its nice that they have found a way to make diesel out of halitosis and a beverage, but unless it actually points toward or leads to a viable solution, I can't really get behind it. I would rather they put research into more plausible renewable energy infrastructures or developing a better mosquito repellant. Making diesel from water doesn't seem like a worthwhile endeavor unless there is a greater purpose that I'm not seeing. If the byproduct of their efforts finds a cure for cancer, then great. But making a teaspoon of diesel with 1.21 jiggawats of energy and seltzer water doesn't seem like a great plan.

curtis73 wrote: In this case, its nice that they have found a way to make diesel out of halitosis and a beverage, but unless it actually points toward or leads to a viable solution, I can't really get behind it. I would rather they put research into more plausible renewable energy infrastructures or developing a better mosquito repellant. Making diesel from water doesn't seem like a worthwhile endeavor unless there is a greater purpose that I'm not seeing. If the byproduct of their efforts finds a cure for cancer, then great. But making a teaspoon of diesel with 1.21 jiggawats of energy and seltzer water doesn't seem like a great plan.

Don't think of it as "making diesel from water", think of it as a way to run your existing car using a nuclear power plant. THAT is useful.

The volume of the output of today's plant is irrelevant -- it's a research project right now, it's not intended to produce massive quantities. According to the article, Audi says that once they build a production-scale plant they can do it for about the same as a cost of traditional diesel. They don't say whether that's including taxes or not, but...

codrus wrote: Audi says that once they build a production-scale plant they can do it for about the same as a cost of traditional diesel.

This is Audi we're talking about, right?

How 'bout just getting the CAR right and move on from there.

Make water into fuel, heat up the planet, melt icebergs. More water! Renewable resource.

curtis73 wrote:

alfadriver wrote:

curtis73 wrote:

codrus wrote:

alfadriver wrote: Even liquified, H2 does not store that much potential energy.

By weight liquid H2 is the most energy-dense fuel there is, that's why high performance rockets use it. The problem is the volume and the infrastructure to handle cryogenic fuels, so it really doesn't scale down to cars very well.

The other problem (other than the insanely explosive nature of hydrogen) is finding a source. You either spend as much energy getting it from water as you get when you re-combine it, or get it from fossil fuels.

For THIS particular example, the H2 is coming from water. As pointed out in the article. Using renewable sources, or course.

Water is not a source for H as fuel. It can't be. It takes as much (or more) energy to separate it as you get back when burning it. Hydrogen fuel from water is equivalent to taking car exhaust and turning it back into gasoline. If you think about it, water is the exhaust. It is the result of hydrogen burning (combining with oxygen). Converting it back into fuel requires adding back into it all of the energy you just got out of it. My point is... even though they used renewable energy to split the hydrogen off the water, all they've done is store that potential energy in the hydrogen's volatility. Why not use that renewable energy directly and not waste it making complex HCs? Its like a slinky on the steps. Water is like a slinky at the bottom. They are adding all kinds of energy to get it to the top of the steps just to let it fall back down. Why not use the energy that you would waste transporting a slinky and just put it in storage?

I do know that, BUT this example is separating water to produce H2, and then going onto taking air, removing the CO2- and using a combinaiton of that and CO to produce a liquid fuel.

CO2 is as stable as water is, and like water, is the end of the equation. So you could have easily gone off on that part of the fuel source, too.

I know the physics are very wrong, too, as well as the second law of thermo that you point out that energy will always be lost- so making this fuel will always take more energy than it can possibly make.

There are more effective ways to make liquid fuels- which, at the moment, are the leaders in portable and usable energy.

It's just a different form of a battery, like Cordus points out.

(my personal curiosity- why don't we make fuel from sugar beets? Seems like a pretty good source- easy to grow, dense in sugar, etc)

I see chemical energy as just another battery. If you created a new chemical with a lot of energy from two or more low energy chemicals, you had to have put energy in. And the rules are that you must put in more than you will get back; just like a battery. There is no free lunch.