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NOVA ScienceNOW

Fuel Cells: Expert Q&A

  • Posted 07.29.05
  • NOVA scienceNOW

On July 29, 2005, Dr. Eric Miller, an alternative-energy expert at the Hawaii Natural Energy Institute, answered questions about hydrogen fuel cells, their promise and danger for use in cars, and more.

Eric Miller

Eric Miller

Dr. Eric Miller has worked for over 20 years on alternative energy research. His research on fuel cells, solar hydrogen production, stirling engines, and solar cells has included work at Bell Laboratories, Oak Ridge National Laboratory, and the NASA Lewis Research Center. Full Bio

Photo credit: Courtesy Eric Miller

Eric Miller

Dr. Eric Miller has worked for over 20 years on alternative energy research. His research on fuel cells, solar hydrogen production, stirling engines, and solar cells has included work at Bell Laboratories, Oak Ridge National Laboratory, and the NASA Lewis Research Center. Since 1996, he has been a part of the Hawaii Natural Energy Institute at the University of Hawaii at Manoa, where he runs the Thin Films Laboratory, developing energy-conversion materials and devices. Recently he helped establish the Hawaii Fuel Cell Test Facility, a world-class laboratory for evaluating industrial fuel cells and components. He earned his Ph.D. in electrical engineering from the University of Hawaii at Manoa.

Q: If fuel cells are eventually made that give off water as a by-product, would that create a problem of excess water? (I have always understood that there is a fixed number of water molecules within our atmosphere.) Or, if fuel cells eventually use water as fuel from which to extract the hydrogen, will there be a supply problem as water is a scarce commodity in many parts of the world? Melissa Johnson, Rochester, New York

Eric Miller: Aloha Melissa! One of the best ways to get hydrogen for fuel cells (but not necessarily the easiest or cheapest!) is to split water using "renewable" resources such as solar or wind energy. Water is used up in the process, but this water is later recovered in the fuel cells, which recombine the hydrogen with oxygen atoms. In other words, it's a "water cycle," and there's no net excess or loss.

In this picture, the hydrogen would be produced in areas rich in water and energy resources, then stored and transported to other areas for use in fuel cells. It's similar to what we do now by importing oil, refining it into gasoline, and trucking it to gas stations all over the place. The good thing about hydrogen is that it's not confined to just a few countries. It can be found almost anywhere, not only in water, but also in a wide range of other chemical compounds. It still needs to be "refined" into pure form for fuel cell use, which takes some work.

Q: I am interested in a career in your field and wish to know which classes I should take in high school and college to qualify to work on fuel cell technology. Thank you for listening to my request. Greg Towle, Colfax High School, 9th Grade, Alta, California

Miller: Hey Greg! Thanks for the note! Definitely work hard in your math and science classes, particularly physics and chemistry. In college, try and find a class that teaches something called "electro-chemistry," which is an interesting and challenging mix of physics and chemistry. It's a personal bias on my part, but you might consider pursuing a college degree in an engineering field, such as electrical or chemical engineering. There are a lot of practical issues in fuel cell technology begging to be solved by young talent such as yourself! GOOD LUCK... Hope to see you in the labs soon!

Q: Does anyone have an idea how much it will cost to either revamp or establish from the start the new infrastructure for refueling hydrogen cells? One of the obvious reasons we're still fossil fuel dependent is that the enormous cost of the supply infrastructure has already been borne out and the infrastructure is already in place. How much would it cost to put a hydrogen refueling station on every other street corner? Bill Havrilla, Pittsburgh, Pennsylvania

Miller: Hi Bill. You've really hit the nail on the head—installing a brand new infrastructure for the production, storage, and delivery of hydrogen will be HUGE! You should check out the U.S. Department of Energy's "Hydrogen, Fuel Cells & Infrastructure Technologies Program" Web site:

http://www.eere.energy.gov/hydrogenandfuelcells/

There is a lot of government-sponsored research going on now, not only in developing the various hydrogen technologies, but also in developing infrastructure and doing cost estimates. It's a little tricky, especially when some of the cost estimates involve technologies that are not yet developed. It becomes even trickier when trying to take into account the economics of a dramatically changing world energy picture.

As world demand for oil escalates while supply plateaus (and eventually drops off), and as environmental impacts of burning carbon-based fuels become more severe, a new "energy revolution" will inevitably take place—maybe not in this generation but certainly in the foreseeable future. Absurdly expensive energy alternatives by today's standards will suddenly become less absurd and less expensive. The new "hydrogen economy" with its massive infrastructure requirements may fall into this category. Let's remember that the "petroleum/gasoline economy" was able to build up its infrastructure over the last 100 years, so it can be done if needed.

I know I haven't answered your question regarding "every other street corner." Honestly, I can't right now. Know that there is progress being made in trying to understand the scope of the undertaking. For example, several "hydrogen corridors" are being planned, on both West and East coasts, where prototype hydrogen infrastructures will be deployed for evaluation.

Q: Will this hydrogen fuel be dangerous? Diane Stiles, Anaheim, California

Miller: Aloha Diane! Certainly there are safety issues involved in handling hydrogen, just as there are safety issues in handling any "fuel," including gasoline. Both hydrogen and gasoline are extremely flammable and need to be carefully contained away from ignition sources. Hydrogen differs from gasoline since it's normally a gas (here, "gas" is NOT short for "gasoline"!). Hydrogen gas is much lighter than air and is fortunately nontoxic. If a hydrogen tank is stored outside and leaks, the hydrogen will quickly float away (like a helium- or hydrogen-filled balloon), and not hurt anyone. If the leaky tank is inside a room with inadequate ventilation, the room could fill up with hydrogen and become a fire or explosion risk. One more thing: since hydrogen gas is so light, a small amount will normally fill up a very large volume. To save space, people like to pack the hydrogen atoms into containment cylinders under very high pressures (hundreds of times the normal pressure outside). If these cylinders are ruptured, there can be a dangerous explosion.

Scared yet?! Not to worry. The safety aspects of handling hydrogen are being taken very seriously. If and when hydrogen takes the place of gasoline in our cars, rigorous safety codes and standards will ensure that the proper hydrogen-handling equipment and procedures are in place to keep the public out of harm's way. You've asked a very important question. Thanks!

Q: What do you think the chances are of getting the cost of hydrogen production and distribution down to an affordable level? Bob James, Loganville, Georgia

Miller: Good question Bob! The chances, I believe, are pretty good. There's a lot of research and development going on to bring down costs of hydrogen production, storage, and distribution. In some cases, relevant technologies which already "work" just need to be made better. Performance and cost improvements, for example, in solar cells and water electrolyzers (which can be used in tandem to generate hydrogen) are being explored. For hydrogen storage, high-pressure cylinders made of new composite materials are being developed that are more crash-resistant and potentially less expensive. In other cases, completely new technologies are being developed that could potentially revolutionize performance and price. Remember, for example, the direct solar-to-hydrogen conversion process discussed in the TV program (it was compared to photosynthesis in the leaf)?

As of today, natural gas reforming and maybe wind-turbine/electrolyis are close to being economical for hydrogen production. (As drawbacks, the reforming process suffers from CO2 emissions, and the pollution-free wind/electrolysis process is only viable in certain high-wind areas.) Most other processes are still "off the radar" in terms of cost. This will change with the continued research and development. Also, as oil becomes more and more expensive, resulting from escalating world demand and (ultimately) diminishing supply, alternative energy systems will become more attractive and relatively more affordable. If we choose the "hydrogen economy" as a primary alternative for managing our energy needs, I'm confident components of the production and delivery systems will reach affordable levels.

Q: When will hydrogen fuel cell cars be available to the public? Christy Woodward, Middletown, New Jersey

Miller: Hey, Christy! Actually, there are a few fuel cell cars, buses, and SUVs on the road already, as seen in the TV program. These are mainly demonstration prototypes (but if you offer enough money, you might be able to buy one!). There's the rub: having them "available" is different from having them "affordable." On top of this, right now, without any hydrogen production, storage, and delivery infrastructure available (such as local hydrogen "gas" stations), your fuel cell car would mostly be a very expensive lawn ornament!

Much has to happen before the full emergence of the fuel cell car onto our public roads, including: (1) development of improved fuel cell technologies up to mass-production levels; (2) development of viable hydrogen production, storage, and delivery technologies; and (3) installation of an integrated hydrogen infrastructure. I wish I could give you a date! The U.S. government's Department of Energy has set some aggressive targets for affordable fuel cell transportation systems by 2015. And remember what President Bush told us: "The first car driven by a child born today could be powered by hydrogen—and pollution-free." I hope so (but check with me again in 2014!). In the meantime, please keep checking for updated information at:

http://www.eere.energy.gov/hydrogenandfuelcells/

and similar Web sites.

Q: Where in the heck are you going to get the hydrogen to fuel these cars? It's not like we have tanks of it just waiting to be used. Yeah, you can get it from natural gas or oil, but then what is the advantage over other current engine/motor technologies? You'll still have CO2 emissions and we'll still be a fossil fuel economy. Seems to me fuel cells are just a bunch of hype. Tell me why I'm wrong! Anonymous, Old Lyme, Connecticut

Miller: As discussed in the TV program, hydrogen is everywhere in a wide variety of chemical compounds, including water, but it's usually comfortably attached to other atoms. It takes a lot of energy to "pull" it off and isolate it in "pure" form, but it's the same energy you get back when the fuel cell generates electricity. In this sense, hydrogen is usually considered an energy "carrier" and not a fuel.

Still, semantics aside, you're absolutely right, the pure hydrogen does have to be produced somehow! In the near term, the only practical processes, such as natural-gas reforming, involve CO2 emissions. The "fossil fuel economy" issue is not solved, but at least the "foreign oil dependence" issue is addressed. To solve both issues in the longer term, there is a concerted research effort to develop processes for splitting water using renewable energy resources, such as solar, wind, and others. Such processes already work, but getting them to work practically or affordably will take a lot more work.

In the meantime, the concept of a hydrogen economy, with all its production, storage, and utilization issues, remains a tantalizing mix of genuine vision, hope, and, yes, hype. Still, in our world's next energy revolution, which will probably get here sooner than we expect (definitely sooner than we'd like!), hydrogen is a legitimate contender. When you get a chance, check out the U.S. Department of Energy's Web site on hydrogen technologies development programs:

http://www.eere.energy.gov/hydrogenandfuelcells/

There's a lot of government support for this research right now; and even more interesting, there's quite a bit of hydrogen research brewing at the major automotive and petroleum companies.

Q: My question concerns hydrogen on demand. Why can't a hydrogen internal combustion engine be manufactured where electrolysis is used from the electricity produced from the alternator to separate hydrogen from water as needed? I believe a "water-powered" car with dual alternators to provide electrolysis would work. I even found a patent on an "ELECTROLYTIC CARBURETOR" designed by a Charles Garrett in 1935. He was said to have had a working vehicle that he demonstrated, where the electrolysis took place between plates in the carburetor. It is on a Web site:

http://www.keelynet.com/energy/garrett.htm

Couldn't this be a solution? Earl Wagoner, Fort Walton Beach, Florida

Miller: Thanks, Earl, for the Web site! I found a lot of interesting hydrogen-related information there. I also found something a little confusing that I'd like to warn you about, namely, the possible suggestion of a "perpetual motion machine" (which is definitely NOT possible). Let me explain:

First, internal combustion engines that burn hydrogen instead of gasoline have in fact been demonstrated—no argument there. Second, electricity from an alternator can be used to split water and generate hydrogen—again, no problem. Here's the catch: the energy you put into separating the hydrogen and oxygen is (in the very best case) the energy you get back in combusting them together in the engine; it's like pulling a bowstring then letting it snap! After combustion, you still need to convert the heat energy into mechanical energy for running the car, the alternator, etc., and you lose quite a bit in this process. After all is said and done, an engine running on hydrogen can't generate enough hydrogen (through, for example, pure alternator-driven electrolysis) to sustain itself. Some additional energy is needed, such as an additional chemical or fuel supply, a battery, solar cells, wind generators, something. It's fun to think about, though! Keep up the diligent research, and keep the creative ideas flowing.

Q: Living in North Dakota, what happens when you have thousands of hydrogen cars releasing water over frozen streets in the winter time? Dennis Hartwig, Grand Forks, North Dakota

Miller: Greetings Dennis! To address your concern, the fuel cell cars would be designed to release water in vapor form (a.k.a. steam), which would be readily absorbed into the dry winter air. That being said, however, one of the real and most significant concerns for today's membrane fuel cells does relate to those cold North Dakota winters—namely membrane "freeze-up." If small amounts of water left behind within the membrane freeze up after the car stops running, there could be significant damage to the fuel cell. There's a lot of research going on to figure this one out. I expect fuel cell cars during winter will be seen on the roads here in Hawaii long before North Dakota!

Q: A significant amount of the hydrogen produced today is used in the refining process of gasoline. Additionally, a significant amount the hydrogen produced today is used to produce fertilizer that gets used to produced ethanol. If we just used hydrogen we are already using in the process of refining fuels to instead directly power fuel cell vehicles, how many fuel cell cars would you anticipate that existing production could support? I've seen it posted on a BMW World Web site that all the existing hydrogen produced today could power 250 million fuel cell vehicles. I'm wondering how many could be fueled if we just used the portion of hydrogen that is already used to make fuels today. Joel

Miller: Hi Joel. I'm impressed with your research! Not many people are aware that hydrogen is routinely being thrown away or flamed-out as a result of many of our industrial processes. The BMW statistic you mentioned was particularly interesting. There's a little bit of a catch-22 in your question, at least in regards to the waste hydrogen from the oil refining process. In the near term, this is a GREAT supply to get the hydrogen economy up on it's feet. However, in the long term, the same hydrogen economy would like to eliminate oil refining altogether! Still, by-product hydrogen from other non-oil industrial processes should be utilized. At the same time, any carbon-emission issues associated with these processes will need to be addressed for environmental protection. There's a lot of work ahead (but it's what keeps us scientists employed!).

Q: Do you think that cars that use fuel cells will soon replace the use of hybrid-powered vehicles altogether? Anonymous, Glendale, Arizona

Miller: Will fuel cell cars replace all the hybrid vehicles...

...soon? NO;

...eventually? MAYBE;

...if we ultimately decide to embrace the "hydrogen economy" for managing our future energy needs? DEFINITELY!

Fortunately, many of the electric-based car components needed in a fuel cell vehicle have already been established through the development of the "hybrid" technology. If and when durable and efficient fuel cells are being mass-produced, and an infrastructure for hydrogen production, storage, and delivery has been set up, the transition from hybrid to fuel cell cars should go smoothly. Before that time, I suspect we will be seeing other alternative fuels, such as bio-diesel, entering the mix, in both conventional and hybrid vehicles. These will not be clean-burning (like fuel cell cars), but they will reduce our dependence on foreign oil.

Q: Why can't electricity made by photovoltaic cells or solar collectors electrolyze water, splitting hydrogen and oxygen, and later be used by a fuel cell for power or used as an auto fuel? The electricity generated by solar power is used to electrolyze water, then the hydrogen is stored in a battery tank of potential energy until it is needed by a fuel cell to generate current or pumped into a hybrid gasoline/fuel cell electric vehicle. The by-product of the fuel cell could be recycled back to the hydrolysis stage. The heat created by the fuel cell could also be harnessed to heat water for residential use. Thank you for the opportunity to participate. Christian Manasse, Phoenix, Arizona

Miller: Impressive, Christian! You've really thought this through—and everything you say is absolutely correct. What you describe is definitely a part of the big "hydrogen economy" puzzle. It's certainly important in geographical areas basking in sunlight, where solar energy is an invaluable asset. Current state-of-the-art solar cells and water electrolyzers will need to be improved significantly (in terms of performance and cost) for the large-scale deployment we're envisioning. As described in the NOVA program, new technologies are emerging for the direct conversion of sunlight to hydrogen (without having to produce electricity as an intermediate step), which could also play an important role.

This brings up a subtle, but important point: if you're living in a sunny area and have lots of solar cells producing electricity, use as much of the electricity as you need FIRST (for lighting, heating, appliances, etc.), and use what's left over to generate the hydrogen. If you convert all your solar electricity to hydrogen, then later use hydrogen conversion in fuel cells to supply your electricity needs, the extra conversion step wastes a lot of energy. Another important point I'd like you to consider: the picture you painted is readily adaptable to windy areas—substituting wind generators for solar cells; and to areas with abundant water resources—using hydro-powered generators, etc. It's really very exciting!

Q: Who still alive could be considered the father of the fuel cell? Emma Tevaarwerk, Evanston, Illinois

Miller: Let's see, Emma. The original "father of the fuel cell," who discovered the technology, was Sir William Robert Grove, who lived until 1896. As for counterparts today, one of the "fathers of the modern fuel cell" would definitely be Dr. Geoffrey Ballard. This isn't to diminish the significant contributions of many other great scientists in the field!

Q: What size fuel cell generator would be needed to supply a residence that uses 3000KW per month? How soon will this be available and how much will it cost initially? Roy Wileman, Houston, Texas

Miller: Aloha Roy! Let me keep you down to Earth for a moment: First, there are actually commercial fuel cell generator sets on the market today; however, an example of a "good" price right now would be $15,000 for a 5kW generator (that is $3000 per kW) running off of pure hydrogen, or $40,000 for the same 5kW unit with an on-board re-former (which takes natural gas as the feedstock, converting it to hydrogen). Needless to say, prices need to come down considerably for average residential use. This will happen as fuel cell technology matures and large-scale manufacturing processes are put into place. As Professor Lewis suggested in the NOVA program, stationary power systems are likely to be the first viable venues for hydrogen fuel cells.

Interestingly, some applications can already afford to use fuel cells, even at today's high prices. NASA can afford to use types of fuel cell power supplies on their space missions, primarily because they are ultra-reliable. Some police stations, banks, and corporations that cannot tolerate even momentary down-time on their computer systems have installed fuel cell-based power backup units in their buildings. People won't start installing fuel cell generators at home until the hardware price comes down, and the hydrogen becomes more readily available.

Q: I learned on this episode of NOVA that fuel cells get their energy from filtering or removing the electron from hydrogen, etc. The analogy was of the hydrogen molecule crawling under the net on a tennis court. My question is: Is there a way to get the oxygen to "crawl under the net" toward the hydrogen? I ask because it seems that there are more electrons attached to the oxygen and when those electrons go around the "net" it seems that there would be more electric energy created or released. I am not a chemist so please forgive me if the answer to this question is obvious. Anonymous, Springfield, Massachusetts

Miller: You've made an interesting observation from the NOVA show! Well, one thing to consider is that it would be really hard to strip a bunch of electrons from a single oxygen atom. Relatively speaking, it's a piece of cake to snag a hydrogen atom's single electron. (You know how the joke goes—one hydrogen atom says to another "Hey, I think someone just snagged my electron," and the second replies "Are you POSITIVE?!") Anyway, the second thing you should know is that today's fuel cell membranes (that is, the "tennis net") have a chemical makeup that specifically allows hydrogen ions to move around and "wiggle" through. This is why the program's analogy showed the "hydrogen guys" slithering under that net!

Q: Why not use compressed-air-powered engines like the French Midi? The advantages are so numerous, it has to be the best possible approach. No infrastructure required. No tankage in ground, no fuel deliveries to fuel stations. The air that comes out is cleaner than what goes in, so there's a reduction of pollution. No refineries needed, no pipelines needed, no tanker ships, no tank farms, no ground pollution. Just place compressors at various locations and let people refuel. No fires in the event of an accident, no fuel spills requiring Hazmat teams. Little or no oil changes required. This seems to be the perfect solution for now. Do you agree? John Malinoski, Wilton, New York

Miller: Mahalo John. Admittedly, I didn't know much about the MDI compressed-air car until you brought it to my attention. It's very interesting and certainly merits further investigation on my part. From the information I was able to dig up so far, current models of this car use an electric compressor that is plugged in to pressurize the storage tanks. Using refilling stations with ready supplies of compressed air would be one obvious alternative. In the MDI car, there may be some issues regarding range and top speed, but these could probably be improved. I think the main issues are 1) the safety and reliability of the high-pressure storage cylinders; and 2) the energy source—the electricity has to come from somewhere—and the conversion process from electricity to compressed-air may not be very efficient. Anyway, I'll keep reading up. Thanks for the tip!

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