shallowdeep
Posts: 343
Joined: 9/1/2006
From: California
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quote:
Does anyone know what the hold up is? This guy claims 4 ounces of water to drive 100 miles. If that is true then why are we not seeing "on demand" hydrogen generators for our cars?
The holdup is that hydrogen is not a (terrestrial) fuel source and never will be. The reason is that hydrogen does not exist in substantial quantities in a pure form on this planet. As a result, the only way to get it is to break the chemical bonds of some hydrogen containing compound. The two major types of hydrogen containing compounds available are fossil fuels and water.
Fossil fuels have the advantage that it's relative easy (i.e. doesn't require much energy) to break the hydrocarbon bonds. The downside it that you have leftover carbon. In the most common method of getting energy from fossil fuels, combustion, the carbon is released primarily as carbon dioxide and the hydrogen is immediately combined with oxygen to form water, releasing heat in the process. Other, more controlled, reactions are possible, as luckydog1 pointed out, that leave you with hydrogen. However, these still have the problems with carbon emissions (although it may be easier to sequester the carbon) and aren't much (if any) more efficient than a well engineered (and typically much cheaper) natural gas generator that puts waste heat to work. For an example of such convential fuel co-generation (heat/electricity) devices, see this article.
Water has the advantage that there is no carbon to deal with, but the major disadvantage that the element that you want to combine the hydrogen with (either by burning it or putting it through a fuel cell) is oxygen, the very same element that the hydrogen was initially bound to in the water. Conservation of energy and the universe's always increasing entropy, extremely fundamental principles of our scientific understanding (the First and Second Laws of thermodynamics), tell us that there is no way to take water, break it into hydrogen and oxygen, recombine the hydrogen and oxygen back into water and get out any useable net energy. Hopefully, that isn't too surprising. Basically, you can think of water as having a low potential (chemical) energy. You can separate it into hydrogen and oxygen, but doing so requires an energy input to raise it to this higher potential, usually in the form of the electricity used for electrolysis. Recombining to form water again lowers the potential back to the initial level and allows for the recovery of energy, but the energy recovered can be no greater than the energy put in (and, due to inefficiencies, is always at least somewhat less). As a result, there is no way to get "clean" energy from water. As other posters have pointed out it is more appropriate to think of the combination of electrolysis and fuel cells as a sort of "battery" or energy storage system, not a source of energy production.
As to the three linked videos/articles, my analysis of each:
1. 4 oz. of water to go 100 miles.
http://www.youtube.com/watch?v=GfXNtIv5HyA
The video is rather misleading. If you actually look into what Klein did, he used a limited amount of electrolysis produced hydrogen as an additive to a standard, gasoline powered engine. So, the "4 oz. of water" was in addition to the gasoline used for the trip. From his website: http://hytechapps.com/aquygen, we see the more plausible claim that his system can enhance "the fuel-efficiency of a traditional gasoline or diesel engine 25-30%". Using the idling engine power when stopped and/or regenerative braking to drive electrolysis and then injecting the produced hydrogen gas into the fuel could improve efficiency in much the same way that standard battery hybrids, like the Prius, do. However, burning the hydrogen in an internal combustion engine (as he appears to do) isn't terribly efficient and might cause problems for an engine designed to run on gas if used long-term. The basic idea isn't bad, since the added weight and toxic materials of large battery packs are the major downsides of current hybrids, but there is nothing revolutionary here. Unfortunately, based on the website, Klein doesn't really seem to understand chemistry... and probably thinks he has something of a larger breakthrough than he does, hence the hype. I'm more than willing to give him the benefit of the doubt as a well-intentioned guy with insufficient educational background... but there is also the possibility he's just trying to sucker in dumb investors.
2. "Fuel Cell Dune Buggy"
http://video.google.com/videoplay?docid=-813727532577660991&q=hydrogen+power
Taken from the 1980s, I'm assuming (from the hair and references to Reagan's "Star Wars" system and oil embargoes), this is little more than a demo of hydrolysis and isn't even a fuel cell (in the sense the term is currently used). The guy is using electrolysis (which consumes a bunch of electrical energy) to produce some hydrogen which he then burns as fuel in his dune buggy. Again, it would require more energy to generate the hydrogen than you would get back from burning it.
3. "A simple Fuel Cell"
http://video.google.com/videoplay?docid=5502240084388841554&q=hydrogen+power
Again, this is not a fuel cell, but an electrolysis device. The technique is no different than that practiced since the pioneers of electrochemistry in the first half of the 19th century, making the overly theatrical sound track... well, a little overly theatrical. This device is actually consuming electrical energy to split water into hydrogen and oxygen. Later the hydrogen can be recombined with oxygen either by burning it or using a fuel cell, but even with no inefficiencies the energy regained will not exceed what went into it.
4. Increasing the Efficiency of the Water Electrolysis Cell
http://www.hydrogen.energy.gov/pdfs/progress05/iv_h_6_pile.pdf
A 2004 paper discussing some research into water electrolysis for hydrogen production. It's interesting to note that target efficiency for 2010, not yet obtained, is only 76%. So, in the real world we can see that significant inefficiencies exist in electrolysis.
Conclusions
So, with all that said... why is there all this the hype about a future "hydrogen economy"? Is hydrogen as part of an energy infrastructure useful at all?
First, I need to reiterate that hydrogen is not a solution to energy problems because it is not a source of energy. However, if used properly, it could reduce our energy inefficiencies and eliminate much reliance on oil as an energy source.
Hydrogen usually comes up in the context of cars. The internal combustion engine is simple, but remarkably inefficient. Only about 20% of the fuel energy is converted into useful energy, the rest goes to waste as heat. A hydrogen infrastructure would allow for these many, inefficient engines to be replaced by fewer, more efficient power stations. A combined cycle power plant can be close to 60% efficient. A fuel cell that recombines oxygen and hydrogen can be 80-90% efficient. Electric motors, which a fuel cell would power can be over 90% efficient. Assuming a 60% efficient power plant, 5% transmission losses in power lines, 70% efficient hydrolysis, 80% efficient fuel cell, and 90% efficient motor, such a system could be close to 30% efficient, a 50% increase in efficiency that could reduce energy consumption for cars by a third. It might actually be better as the heavy engine in a car could be replaced by a lighter fuel cell, saving energy due to weight reduction and possibly making cars safer for the same reason. Additionally, with electric motors and fuel cells there is no need to idle the engine when stopped, which gives some of the savings that hybrids experience in city driving.
Furthermore, once freed of the internal combustion engine, there is no need to rely on petroleum as the fuel source. For political and economic reasons there are obvious advantages to this. From an environmental standpoint the ability to use more nuclear, solar, wind, etc. is also a major advantage. However, this brings up the problem that, currently, power for electrolysis would come from the current power grid... which is has far too many inefficient and dirty old plants and far too few clean ones. At present, a full switch to hydrogen might actually make things worse environmentally. A switch to hydrogen might still make some sense, but water hydrolysis for hydrogen production would have to be extensively supplemented by chemical cracking of hydrocarbons, which leaves all the carbon emission problems to deal with.
In a future where the power grid has a higher composition of clean generation facilities (or we finally develop a practical fusion reactor -- one can dream), hydrogen will make a lot of sense as it will let our transportation energy requirements tap into a clean source of power. Until that time approaches, I think that we would be better served by implementing existing technologies to improve efficiency, like hybrid gas/electircs, much more extensively and advocating for the construction of such clean power generation facilities. I see this as a much better use of resources over at least the next decade than extensively developing a hydrogen infrastructure.
The other reason why hydrogen hasn't caught on yet is that, after many years of research, there still isn't a great way to store it for use in a vehicle. As a gas it occupies much more space than liquid gasoline, so something has to be done or cars won't be going very far on a tank. Compressing it is the obvious solution, but brings some safety issues... fuel/air explosives can be nasty =). A promising solution may be metal hydrides, but so far I'm not aware of any commercial quality solution. Of course, there is also the need to build up an entire hydrogen infrastructure: production, distribution, transportation, and storage. Those perhaps best suited for undertaking the task, gas station owners and oil companies, don't yet have sufficient economic incentive.
Another way that hydrogen could help improve efficiency is in the power grid itself. Currently, to ensure there are no blackouts/brownouts, power is consistently overproduced and wasted. The reason is that it takes time to bring a conventional power plant on or offline so, there is always a bit extra production online above peak expectations so that a sudden spike in demand won't degrade or bring down the system. With a hydrolysis/fuel cell system hooked up to the grid and carefully monitored some of this wasted excess could be shifted to hydrogen for storage and, during demand spikes or when reservoirs were full, the hydrogen could be used to generate power. Such a system could be switched between generation and storage very quickly (since there are no turbines to fire up, etc.) and could potentially improve the grid's efficiency and also reliability.
The world's current energy policy is unsustainable both from an economic and environmental standpoint and the sooner we start to fix things the better. However, those concerned need to know enough to support the right technologies and to make a strong argument for the necessity of alternatives to the current system... hopefully this helps a little on that front.
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"I don't worry about conserving energy, the First Law's got me covered."
- Engineers for conservation of energy quality
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Hydrogen as Fossil Fuel Clean Replacement - 
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