Zachary Trimmer EGEE 101H Semih Eser Hydrogen Production and Future Fuel Possibilities You wake up in the morning, turn on the lights, and make yourself a cup of coffee. The television reports to you the daily news and weather conditions. Your toast is ready, and you eat it quickly; it is time to go to work. You get in your car and drive, noticing that your tank is low. However, yours is not the only low tank. The world’s tank is low, not only on petroleum, but on fossil fuels as a whole. Look back at what you used this morning: lights, coffee maker, television, toaster, and car. Renewable energies such as wind power and solar power can help replace the burning of coal and other fossil fuels for the generation of electricity to power your home appliances. Yet, wind power is not a mobile source of energy that can refuel your car. Neither is tidal, hydro, nor nuclear power. In an age where transportation is so vital that over 89% of Americans own one or more cars, a replacement for gasoline is essential (Pendley 4). Biomass fuels could be used, but how much food can be sacrificed for gas? Batteries could be used, but limited distance and lengthy recharges hinder their practicality. Another replacement could be hydrogen. Unfortunately, hydrogen is not the perfect energy source that the public believes it to be. It actually is not an energy source at all. Hydrogen can not be mined; it must be produced. It is, however, a great energy carrier. According to Smil, author of Energy, “Its key advantages are superior energy density (liquid hydrogen contains 120 MJ/kg compared to 44.5 MJ/kg for gasoline), a combustion that yields only water, and the possibility of using it in fuel cells” (Smil 172). Before discussing the feasibility of Trimmer 2 hydrogen as a fuel for transportation vehicles, it is important to understand the different methods of hydrogen production being researched today. Since the goal is to replace fossil fuels, the generation of hydrogen from natural gas and other fossil fuels will be omitted. To begin, hydrogen can be produced from the photolysis of water in membranes by solar radiation. One of the key benefits of this method is that solar energy is infinite. However, the yield is very small. Only around .2 - .4 m3 of hydrogen per day can be generated at one atmospheric pressure per square meter of surface. At a 30% conversion efficiency of solar energy at all wavelengths, an area of 33,000,000 m2 is required to produce 7,100,000 m3/day of hydrogen which is the equivalent of a 2000 MW electricity generating station (Melvin 223-224). Next, biophotolysis of water by cyanobacteria and microalgae produces hydrogen. Cyanobacteria and microalgae are capable of oxygenic photosynthesis as seen in the reaction CO2 + H2O 6 [CH2O] + O2. According to Kazuhisa Miyamoto, professor at Osaka University, Japan, “Photosynthesis consists of two processes: light energy conversion to biochemical energy by a photochemical reaction, and CO2 reduction to organic compounds” (Miyamoto 2). Instead of decreasing CO2, under certain conditions cyanobacteria and microalgae consume biochemical energy to generate hydrogen. There are two enzymes capable of hydrogen production: hydrogenase and nitrogenase. Hydrogenase hydrogen production was first discovered in 1942 when scientists Gaffron and Rubin observed that a green alga created hydrogen under light conditions after being deprived of light and oxygen. Hydrogenase catalyzes the reaction 2H+ + 2Xreduced 6 H2 + 2Xoxidized (Miyamoto 2-3). Further studies have shown that the Trimmer 3 reducing power of hydrogenase does not have to come from water; it can also be derived from starch. In 1988, a group of scientists led by Eli Greenbaum, a research scientist at Oak Ridge National Laboratory, reported 10 to 20% efficiencies of light conversion to hydrogen. Unfortunately, hydrogenase is very oxygen-labile, so light-dependent hydrogen production can only be sustained for several tens of minutes because of the oxygen produced in photosynthesis. In 1986, a light/dark cycle was proposed. According to Miura and Miyamoto, “CO2 is reduced to starch by photosynthesis in the daytime (under light conditions) and the starch thus formed, is decomposed to hydrogen gas and organic acids and/or alcohols under anaerobic conditions during nighttime (under dark conditions)” (Miyamoto 4). Miyamoto more recently proposed a way to improve the yield of starch degradation by chemical digestion of algal biomass. Nitrogenase-dependent hydrogen production was discovered later than hydrogenase-dependent in 1974. Miyamoto explains how nitrogenase produces hydrogen very well: Molecular nitrogen is reduced to ammonium with consumption of reducing power (e' mediated by ferredoxin) and ATP. The reaction is substantially irreversible and produces ammonia: N2 + 6H1+ + 6e- 2HN3 12ATP 12(ADP+Pi) However, nitrogenase catalyzes proton reduction in the absence of nitrogen gas (i.e. in an argon atmosphere). 2H+ + 2e- H2 4ATP 4(ADP+Pi) (Miyamoto 4-5). Trimmer 4 Unfortunately, the nitrogenase-catalyzed hydrogen production occurs as a side reaction at a rate of around a fourth of nitrogen-fixation. Nitrogenase is also oxygen-labile, but cyanobacteria have developed ways of protecting nitrogenase from oxygen by decreasing power and providing it with ATP. Miami BG-7 is one of the most effective hydrogen- producing cyanobacteria. One of its strains, Synechococcus, has an estimated conversion efficiency of 3.5% using an artificial light source (Miyamoto 5). Another method of hydrogen production is using photosynthetic bacteria. A benefit of this method is that light energy is not required making the efficiency of light energy conversion to hydrogen gas much higher than that from cyanobacteria. Miyamoto states, “Photosynthetic bacteria undergo anoxygenic photosynthesis with organic compounds or reduced sulfur compounds as electron donors” (Miyamoto 6). There are also some non-sulfur photosynthetic bacteria that are powerful hydrogen generators; they utilize organic acids. The maximum energy conversion efficiency obtained from photosynthetic bacteria was demonstrated by Miyake and Kawamura at 6 - 8% efficiency using Rhodobacter. Finally, nuclear power can be used to generate hydrogen. Hydrogen can be produced from nuclear energy by way of electrolysis, high-temperature steam electrolysis (HTSE), and thermochemical water splitting cycles (TWSC). Current day nuclear reactors are only capable of producing hydrogen via electrolysis. This approach would be employed during off-peak hours and utilize existing water electrolysis production technologies. With the production of Generation IV nuclear reactors, temperatures in the range of 700-1000ºC would be attainable, making HTSE and TWSC possible (Hydrogen 2). HTSE is more efficient than normal electrolysis because it “uses heat, instead of Trimmer 5 electricity, to provide some of the energy needed to split water” (Hydrogen 1). TWSC also uses heat; around 1000ºC is used to split water into its component parts. In each case, the high temperatures come from nuclear waste heat. So, is hydrogen the answer to our fuel-related needs? It has the potential to be. However, not one production method will be omnipotent. Each method should be employed. Photolysis on a mass production scale is infeasible. Not only will the facilities be too large, but the vast amount of equipment is very capital intensive (Melvin 224). What about on a smaller scale? Scientists in Melbourne, Australia, have made an incredible breakthrough. They have developed a solar-powered hydrogen fueling station that fits in anyone’s garage. Todd Woody interviewed the scientists who said at “the heart of the fuel station is an electrolyzer – essentially a fuel cell run in reverse” (Datta 1). Photovoltaic solar panels or wind turbines, depending on which suits the owner more, will send electric currents to separate water into hydrogen and oxygen. The hydrogen is then compressed and stored in the station (about the size of a file cabinet) ready to be used in a fuel-cell car. The fueling station is expected to generate enough hydrogen in one day to power a car around 100 miles (Datta 1). At only $500, it will pay for itself in less than a year. The station is perfect for public transportation vehicles and people who do not have a long commute to work. However, what if people need to drive greater distances? In order for hydrogen to dominate the transportation fuel market, people will need to be able to refuel on the road at stations. One of the main concerns associated with the switch to hydrogen is the need of an infrastructure. The home fueling station alleviates much of that problem, but there still will have to be filling stations on major high ways. Trimmer 6 Can enough hydrogen be produced to meet American needs? Currently, photosynthetic, anaerobic, and bacterial hydrogen productions have low conversion efficiencies alone. However, you can combine these methods to generate more hydrogen. Miyamoto explains how the combination of anaerobic and photosynthetic bacteria could increase the potential of their application in hydrogen production: Anaerobic bacteria metabolize sugars to produce hydrogen gas and organic acids, but are incapable of further breaking down the organic acids formed…theoretically, one mole of glucose can be converted to 12 moles of hydrogen through the use of photosynthetic bacteria capable of capturing light energy in such a combined system. From a practical point of view, organic wastes frequently contain sugar or sugar polymers. It is not however easy to obtain organic wastes containing organic acids as the main components (Miyamoto 6-7). Greenbaum, with other Oak Ridge scientists, succeeded in the combination. They produced 11.6 hydrogen molecules for every glucose molecule used (Producing 3). Genetic engineering is also trying to increase the amounts of hydrogen achieved by altering antennae in certain algae. Greenbaum hopes to have “mutant algae that will produce 10 times more hydrogen if we increase the light intensity 10 times” (Producing 2). Still, photobiological hydrogen production will not be the end all method of production. It will not be able to create enough hydrogen to fit the needs of the American public who, according to the Energy Information Administration, consume around 103.6 billion gallons of gasoline a year. Therefore, nuclear hydrogen production should be Trimmer 7 incorporated. In order to achieve optimum hydrogen production from nuclear power, Generation IV plants must be produced. Public opinion needs to grow for nuclear energy in order for the Generation IV plants to be built. Luckily, the public is beginning to view nuclear energy in a positive light again in the United States; environmentalists are beginning to support nuclear energy as seen in the Environmentalists for Nuclear Energy organization. In 2004, James Lovelock, most known for his concept of Gaia, called for an increase in nuclear power (Morris 91). Unfortunately, nuclear energy is not viewed the same way in Europe. Many countries within the European Union are planning to decommission their sites prematurely. Germany, for instance, plans to shut down its nuclear power plants only after 32 years rather than the 40 planned years (Morris 77). Nuclear energy will work in the U.S., but if Europe maintains its decommission trend, do they have alternatives for more hydrogen production? Using Germany as an example again, the answer is yes. The same principle that is applied to modern nuclear hydrogen production can be used with Germany’s windmills. During off-peak hours, the windmills can be used to create hydrogen. Other countries that have an abundance of renewable energies can follow suit. Iceland is planning on using geothermal energy to produce hydrogen via electrolysis and thermochemical methods (Arnason 3). It is probable that other nations along the Ring of Fire could utilize Iceland’s geothermal hydrogen production. An additional concern affecting hydrogen’s progress is the public disposition that hydrogen is dangerous. In many ways, hydrogen is safer than gasoline. Hydrogen spills won’t pollute the earth like petroleum spills do. But, if the tank does leak, how much damage would it do if ignited? The College of Engineering at Miami University Trimmer 8 performed tests and concluded that temperatures inside a car that had an ignited hydrogen leak only rose 1 – 2 degrees centigrade. The outside of the car did not get any hotter than it would on a sunny day. Lastly, pressurized hydrogen tanks are made to endure tremendous impacts. Simulated crashes at 55 mph have left the hydrogen tanks intact while the cars are totaled. BMW has tested its hydrogen-fueled vehicles in accident simulations that include collision, fire, and tank ruptures. In each case, the hydrogen cars performed as well as conventional cars (Is 1-2). In conclusion, the age of fossil fuels is coming to an end. Preemptive efforts must be taken to decrease the negative effects of a switch to new energy sources and carriers. Europe has become the leader in renewable energy advances. The United States has the potential to become the forefront for hydrogen advancement. The U.S. has 103 light water nuclear reactors at 64 sites to use for nuclear hydrogen production (Hydrogen 3). Oak Ridge National Laboratory is making advances in genetic engineering to increase the potential of photobiological hydrogen production. However, not only do the scientists need to help, but so do the American people. They must embrace hydrogen and call for more hydrogen cars and infrastructure. They need to show their commitment by purchasing the Australian home fueling station. Once the consumer demands hydrogen- fueled cars, the industry will respond. Works Cited Arnason, Bragi, and Thorsteinn I. Sigfusson. "Application of Geothermal Energy to Hydrogen Production and Storage." University of Iceland. 25 Mar. 2007 <http://theochem.org/bragastofa/CD/essen.pdf> Trimmer 9 Datta, Saheli, and Todd Woody. "8 Technologies for a Green Future." CNNMoney. 7 Mar. 2007. 20 Mar. 2007 <http://money.cnn.com/magazines/business2/business2_archive/2007/02/01/8398 988/index.htm>. "Hydrogen Production - Nuclear." 2007. New York State Energy Research and Development Authority. 20 Mar. 2007 <http://www.getenergysmart.org/Files/HydrogenEducation/7HydrogenProduction Nuclear.pdf>. "Is Hydrogen Dangerous?" Rocky Mountain Institute. 2006. 25 Mar. 2007 <http://www.rmi.org/sitepages/pid536.php>. Melvin, A. “The Impracticality of Large-Scale Generation of Hydrogen From Water Photolysis By Utilization of Solar Radiation.” Int. J. Hydrogen Energy. Vol. 4. Great Britain: Pergamon Press Ltd. 1979. 223-224. Miyamoto, Kazuhisa, ed. Renewable biological systems for alternative sustainable energy production. FAO, 1997. Morris, Craig. Energy Switch. Canada: New Society Publishers, 2006. "New Hydrogen-Producing Reaction Could Lead to Micropower Sources." ORNL.Gov. 2000. U.S. Dept. of Energy. 24 Mar. 2007 <http://www.ornl.gov/info/ornlreview/v33_2_00/micropower.htm>. Pendley, Wayne L. "All-Consuming Passion: Waking Up for the American Dream." EcoFuture. 17 Jan. 2002. New Road Map Foundation. 24 Mar. 2007 <http://www.ecofuture.org/pk/pkar9506.html>. Trimmer 10 "Producing and Detecting Hydrogen." ORNL.Gov. 2000. U.S. Dept. of Energy. 20 Mar. 2007 <http://www.ornl.gov/info/ornlreview/v33_2_00/hydrogen.htm>. Smil, Vaclav. Energy. Oxford: Oneworld Publications, 2006.