Introduction

The economic and political landscapes of the United States are shaped by the country’s heavy dependence on oil as an energy source. Dependence on oil from foreign countries has resulted in fuel crises, rising gas prices, and U.S. involvement in wars. Looking to oil resources at home as a way to alleviate the county’s dependence on foreign oil has lead to heated debates over opening up the Arctic National Wildlife Refuge to oil drilling. However, regardless of where the oil comes from or how long we are able to make it last, there is a time when the world’s oil reserves will run dry. As this time inevitably approaches, politicians, scientists, and engineers are looking to alternative energy forms.

During the 1970s, it seemed clear to many scientists that the United States would soon be using nuclear power as its primary energy source (Jones, 1971; Winsche, 1973). Heightened concern over nuclear power plant safety and an unresolved debate over how to dispose of the radioactive waste the plants produce have brought the expansion of nuclear power to a stand-still. Many other alternatives to fossil fuels have emerged as possible primary energy sources: hydrological power, solar power, geothermal power, and wind power. However, none of these energy sources have provided a viable option for powering today’s many transportation vehicles.

Hydrogen, a secondary energy source that can be produced from water or hydrocarbons using any primary source, is one of the current leaders in the race to develop the next generation of vehicles. Among its competitors are electric vehicles (EV), which use rechargeable electric batteries as power, and hybrid electric vehicles (HEV), which switch between using an electric motor and a conventional gasoline-powered motor depending on driving conditions. Hydrogen-powered vehicles are favored by many because of their convenience and lack of toxic emissions. The question of which form of technology will dominate in the future does not have an easy answer but it is clear that many alternatives are eager and ready to take over from gasoline when the time is right.

Hydrogen as a Fuel

Hydrogen is the lightest and most abundant element in the universe. One atom of hydrogen consists of one proton and one electron. However, hydrogen does not occur naturally as a gas. Some algae and bacteria give off hydrogen but the gas dissipates and reacts with other elements too quickly to be captured from this natural production. Pure hydrogen gas can be extracted from a number of sources, most notably water and hydrocarbons. Electrolysis is the process of applying an electrical current to water, which separates the oxygen from the hydrogen. Reforming is a heating process that separates hydrogen from hydrocarbons, usually natural gas. The challenges of these to processes will be discussed in a later section. (Wikipedia, 1; Boyle et al., 2003)

The hydrogen fuel that results from electrolysis or reforming is a secondary energy source, analogous to electricity, that can be stored, transported, or used immediately to produce electric and thermal energy. Hydrogen has a high energy per unit weight, allowing for high fuel efficiency ratings, but low energy per unit volume, making finding the space to store hydrogen difficult (Boyle et al., 2003, p.590).

Hydrogen can be used in two different ways: directly as a liquid, or as a gas to power fuel cells. Liquid hydrogen can be used in conventional internal combustion engines (ICE) but rather than producing green house gases (GHG) and other pollutants, the hydrogen-fueled car emits only water. Among the first demonstrations of this possibility were two winning entries in the 1972 National Urban Vehicle Design Competition (Winsche et al., 1973, p.1375). While it may have seemed that the universal use of hydrogen in cars was just around the corner in the 1970s, the technology has not yet been widely implemented. Research and development does continue however. Mazda introduced its latest hydrogen vehicle, the RX-8 hydrogen in 2003. The rotary-powered sports car has the capacity to switch from running on gasoline to liquid hydrogen and back at the flip of a switch (Mazda). For a variety of reasons, primary interest in hydrogen fuel has turned away from liquid hydrogen and towards hydrogen gas.

Hydrogen gas can be used to power fuel cells. Sir William Grove, a Welsh lawyer and physicist, invented the first fuel cell in 1839 (Service, 1999) or in 1850 (Boyle et al., 2003). Grove’s fuel cell ran an electric current through water. This current split the water into molecules of oxygen and hydrogen gas. When the gasses recombined, a current was produced. This technology remained a curiosity until the 1950s when General Electric developed the proton exchange membrane (PEM). The PEM increased the efficiency and practicality of fuel cells enough that they were used to provide electricity, heat, and drinking water onboard the Gemini and Apollo spacecraft (Service, 1999).

How a Fuel Cell Works

Today there is a large variety of fuel cell types; for a description of these, see Boyle et al. (2003, page 586). I will discuss here the most prevalent fuel cell in today’s industry, research and development, the proton exchange (or polymer electrolyte) membrane fuel cell (PEMFC) (Figure 1). The PEMFC is an elegant technology that can, in theory, turn water into heat, electricity, and more water. A PEMFC consists of a proton exchange membrane (PEM) sandwiched between an anode (negative electrode) and a cathode (positive electrode). The PEM is a solid, organic compound that has a consistency similar to plastic wrap and is about as thick as two to seven sheets of paper (NREL). The PEM acts as an electrolyte. An electrolyte is a substance that dissociates free ions when dissolved to produce an electrically conductive medium (Wikipedia, 3). In the fuel cell, the PEM acts as a proton conductor while keeping hydrogen and oxygen separate.

Hydrogen enters the fuel cell and comes into contact with the anode (Figure 2). The anode is made of platinum and carbon and acts as a catalyst for oxidation (the separation of hydrogen’s proton and electron). The protons are conducted by the PEM while the electrons are forced to flow through an external circuit. This flow of electrons produces an electrical current. The electrons then flow back into the fuel cell and reconnect with the protons, which have passed through the PEM, at the cathode. The cathode, like the anode, is made of platinum and carbon but acts as a catalyst for reduction, not oxidation. The protons and electrons combine with oxygen at the cathode to form water and thermal energy. For a good graphic representation of a fuel cell in action, see National Renewable Energy Laboratory’s hydrogen, fuel cells, and infrastructure website. (NREL)

The amount of power that a fuel cell produces depends on its size, operating temperature, and the pressure at which the gases are supplied to the cell. On average, a single cell produces less than 1.16 Volts (NREL). In order to produce enough power to complete the task intended for a particular device, any number of fuel cells can be combined into a stack. A car uses a stack of around 45 cells, depending on how powerful the car is designed to be (Ballard, 2).

Fuel cells can be used as a stationary or portable power sources and in the transportation sector. In stationary applications, fuel cells can provide backup power, deliver power to remote locations, and fuel city or town power plants. Fuel cells can also be portable like batteries because of their small size. They can be used in hand-held electronics, portable generators, and anything a battery is used in except that it will last three times longer between fuelings. In the transportation sector, hydrogen-power fuel cells are already being used in spacecraft and are being developed for cars, trucks, buses, ships, trains, and airplanes. (NREL) There are virtually endless possible applications of fuel cells.

Advancing Fuel Cell Technology

The key to the PEMFC is the membrane. It must be as thin as possible in order to minimize the resistance that protons experience while passing through it, but it must also be impermeable to electrons and oxygen and be as durable as possible. A number of companies are doing research to advance the PEMFC technology, including Dupont, 3M Corporation, Gore, and Ballard Power Systems (Wikipedia, 2). Gore has made a development that adds to the durability and conductivity of PEMs. They have combined their Gore-Tex material with proton-conducting material to make a new kind of PEM. Gore-Tex is a water-repelling mesh that is permeable to gases and is widely used in products from mountaineering parkas to synthetic arteries. The holes in the mesh are filled with materials like those found in traditional PEMs and the result is a thin, strong membrane with increased conductivity. (Voss, 1999)

Ballard Power System, a Canadian company, has made a number of advances that bring fuel cell technology closer to viable utilization in the transport sector. First, they have lowered the cost of their fuel cells by reducing the amount of platinum that is used in the electrodes by 30 percent. Second, they have increased the durability of their fuel cells, showing that they can be operated for more than 2,000 hours of every-day use (equivalent to 100,000 km) before a five percent reduction in performance is observed. The U.S. DOE goal for durability is 5,000 hours. Third, they have produced fuel cells that reliably start in cold weather (-20˚C). (Ballard, 1) Continuing with the advances that have been made in fuel cell technology has the potential to produce a new reliable and affordable energy system.

Challenges

The technology exists to operate today’s cars on hydrogen, either as a liquid in ICEs or as a gas in fuel cells. Why, then, haven’t we made the switch form gasoline? There are many factors that play into the answer to this question but in the end it is a simple matter of economics. For a number of reasons, hydrogen is not yet economically competitive with petroleum-based fuels in the transportation sector. The challenges facing wide implementation of hydrogen fuel fall into three categories: hydrogen production, hydrogen accommodation, and hydrogen delivery and storage.

The technology needed to accommodate hydrogen fuel in cars has already been discussed but having the technology to use hydrogen fuel is inconsequential if hydrogen cannot be supplied to that system. Where does the hydrogen come from? As explained above, the primary sources of hydrogen fuel are the electrolysis of water and the reforming of hydrocarbons. Both of these processes cost money and require energy input. At present, producing hydrogen is too inefficient and costly to be competitive with fossil fuels. Reducing the cost of hydrogen fuel production is a major goal of researchers. However, if oil prices continue to rise, as they are likely to do over the long run, the price of hydrogen will have to come down less and less in order to be competitive.

Hydrogen is produced worldwide, mainly through the reforming of natural gas. It is primarily used to produce ammonia for fertilizers, in oil refining and in various chemical processes (Boyle et al., 2003, p.589). There are several factors to be aware of when considering the use of hydrogen from reforming as an energy source. First, reforming any hydrocarbon to produce hydrogen does produce CO₂. However, it is easier to separate CO₂ form fossil fuels during the centralized production of hydrogen than it is to capture CO₂ as it is emitted from a car’s tailpipe. This captured CO₂ can then be sequestered in the earth’s crust where it does not contribute to global climate change. Second, using natural gas to make hydrogen fuel requires more energy than the consumer gets out of it. Finally, fossil fuels, including natural gas, are limited resources and will run out some day. (Earth & Sky, 2005)

If a switch is made to a hydrogen economy, it is likely that much of the hydrogen will be produced from fossil fuels, at least as in intermediate phase. The goal, however would be to progress to a system that uses water to produce hydrogen fuel. The primary hurdle to overcome in moving towards this goal is reducing the energy input necessary to split water into molecules of hydrogen and oxygen gas. Karen Brewer at Virginia Tech is working to develop a hydrogen generation system that produces hydrogen from water through a chemical process that mimics photosynthesis (Earth & Sky, 2005).

Research is also being done at a number of private companies. Bar-Gadda LLC announced in January 2005 that a prototype of a device that produces hydrogen from water vapor or steam. This device is reported to operate at 90 percent efficiency and produce 80 percent hydrogen (PESWiki). Similarly, Genesis World Energy claims to have developed an efficient and economically practical way to produce hydrogen from water (Genesis, 1). Genesis claims that its device needs just 30 gallons of water and it will power a home for 20 years (Genesis, 2). The specifics of how these devices work are closely guarded and because of their proprietary nature cannot be tested by the scientific community. We can be hopeful that these companies have developed valid devices but one has to wonder why we have not heard more about the Genesis device since its release in 2002 if it is as successful as the company claims it to be.

Where to produce the hydrogen is also in question. This challenge is inextricably linked with issues of hydrogen storage and transportation. Because of hydrogen’s low density, large amounts of space are needed to store it. If hydrogen gas is cooled enough to change to a liquid, less space is needed to contain the same amount of energy. The boiling point of hydrogen is 20.4K or -253˚C (Jones, 1971). This means that liquid hydrogen must be kept at 20K or it will convert to a gas and could be lost. Keeping a storage container at this temperature requires large amounts of energy and thus decreases the net efficiency of the fuel being stored, costing the consumer more money in the end (Service, 1999; Hammerschlag & Mazza, 2005). Hydrogen can also be stored in metal hydrides, the result of a reaction between hydrogen and certain metal alloys (Jones, 1971; Boyle et al., 2003). Small pellets of the metal hydrides could fill a cars fuel tank and when heated, would release the hydrogen. So far this method involves too much weight and cost to be practical.

It has been suggested that hydrogen gas could be transported via pipelines just as natural gas is today (Service, 1999). Using this system, consumers would be able to go to a fueling station and fill up the fuel tanks in their cars with hydrogen just as we do now at gas stations. Deciding to go in this direction would require an enormous investment to rebuild the energy infrastructure of the United States. Estimates of the price of a transition to a hydrogen infrastructure range from $200 billion (King, 2003 fide. Hammerschlag & Mazza, 2005) to $500 billion (Mintz et al., 2002 fide. Hammerschlag & Mazza, 2005). The companies that own today’s fueling stations are not likely to make this investment if there is not a guaranteed consumer base. Likewise, consumers are not likely to invest in hydrogen-powered vehicles if there is not a wide network of stations to fuel those vehicles. Which will come first, the station or the car?

An intermediate solution may be to have individual stations produce hydrogen fuel for sale on sight rather than deliver the fuel from a centralized production facility (Service, 1999). This would be a much smaller investment for fuel companies to make and would eliminate the problems connected with transporting the fuel. This solution does come with some drawbacks, however. Storing the hydrogen would still be an issue but less of one since an individual station would be dealing in smaller volumes than a large production plant. Small productions would be less efficient than large plants. They would also not likely be equipped with the technology to sequester CO₂ from hydrogen production’s emissions. As stated above, this is seen primarily as an intermediate phase in the development of a full-fledged hydrogen economy.

Yet another possibility for hydrogen’s production site is in the cars themselves (Hammerschlag & Mazza, 2005). Cars could be equipped with small reformers that could take fuel, either a hydrocarbon or water, from the car’s tank and feed hydrogen directly to the engine or fuel cells. Since production volume could be varied depending on the demands placed on the car, hydrogen storage would not be an issue. This technology would, however, add to the price and weight of the vehicle and would not be able to sequester CO₂ produced in the reforming of fossil fuels. No clear answers have emerged to questions of how and where to produce hydrogen or how to store and transport it. Each method has its proponents and opponents and the debate is likely to continue for some time to come.

Looking to the Future

Despite all the challenges facing researchers and developers in the hydrogen field, many people remain committed to the idea of a future hydrogen economy. These people include government officials, leaders in the energy and automotive industries, and researchers. In 2001 the National Energy Policy Development Group (NEPD) advised President Bush to develop next-generation technology—including hydrogen. The NEPD sited hydrogen as “showing great promise” as an alternative energy technology (NEPD, 2001, p. 100). In January 2002, the Bush administration acted on the recommendations of the NEPD by initiating the FreedomCAR Partnership between the U.S. Department of Energy (DOE) and the U.S. Commission on Automotive Research (USCAR), a partnership between DaimlerChrysler, Ford, and General Motors (USCAR, 2). The goal of FreedomCAR is to “develop the component technologies necessary to provide a full range of affordable cars and light trucks, and the fuel infrastructure to support them, that will free the nation’s personal transportation system from petroleum dependence and from harmful vehicle emission, without sacrificing freedom of mobility and freedom of vehicle choice.” (USCAR, 1).

A similar partnership was formed in California in January 1999. The California Fuel Cell Partnership (CaFCP) “is committed to promoting fuel cell commercialization as a means to move towards a sustainable energy future, increasing energy efficiency and reducing or eliminating air pollution and GHG emissions.” (CaFCP, 1). Members of CaFCP come from a broader range of fields than FreedomCAR, including auto manufacturers, energy companies, fuel cell technology companies, and state and federal level government agencies (CaFCP, 2). The goals of the CaFCP demonstrate the comprehensive approach the partnership is trying to take in the implementation of fuel cell technology. They are working to put fuel cell vehicles (FCV) on the road, promote fuel stations, insure standardization, and enhance public awareness (CaFCP, 3). So far 15 fueling stations have been built, mostly in the San Francisco and Los Angeles areas, and nine more have been planned. These stations support the 65 FCVs (including buses and cars) currently in California (CaFCP, 4).

Conclusions

Hydrogen as a fuel source has come a long way since the first fuel cell was invented by Sir William Grove, but is it far enough? It would be wise of us to take a step back for a moment and consider whether of not further advancements in fuel cell technology is the best investment of out time and money. Many organizations and companies have powered ahead with research and development of fuel cells despite all the challenges the technology contains. The rebuilding of the U.S.’s fuel supply infrastructure will be costly enough that it should only be done once; we wouldn’t want to spend $400 billion dollars to install a new system and then have to install another system in 50 years when a new technology has been developed.

Before making the investment necessary to convert to a hydrogen economy, we must be sure that it is the best option. Hammerschlag and Mazza (2005) argue that hydrogen is not the best alternative energy source for the transportation of the future. Instead, they believe that electric vehicles have the potential to be more efficient, powerful, and convenient, cost less money, and produce a lower volume of green house gases (GHG) than fuel cell vehicles. The British Department of Transportation agrees with them on this last point, concluding that developing hybrid electric vehicles is the most effective way to reduce GHG emissions (Hammerschlag & Mazza, 2005). There is great power in hydrogen fuel to change the way we think about transportation but as long as we remain dependent on fossil fuels to produce it, it cannot be considered a renewable resource.

Figure 1. Diagram of an expanded fuel cell. A single fuel cell consists of the membrane electrode assembly (inner three layers) and two flow-field plates (outside two layers). The membrane electrode assembly consists of an anode and a cathode on either side of the proton exchange membrane (PEM). Varying numbers of these individual fuel cells can be connected to produce a fuel stack that will produce the required amount of energy. Produced by Ballard Power Systems. (Ballard, 2)

Figure 2. Diagram of a fuel cell using Hydrogen. Hydrogen flows into the cell and is separated into protons and electrons at the anode. Protons flow through the PEM while the electrons move through an outside circuit, producing electricity. The electrons flow back into the fuel cell and meet up with the protons on the other side of the PEM. At the cathode, the electrons, neutrons, and oxygen from the air combine to form water, the system’s only waste product. Produced by Ballard Power Systems (Ballard, 2)
Resources

Ballard: http://www.ballard.com/be_informed/fuel_cell_technology last accessed 4/4/2005.

(1) Technology Hat Trick: (/hat_trick#)

(2) Fuel Cell Technology: (/how_the_technology_works#)

Boyle, G. et al. Ed., 2003, Energy Systems and Sustainability: power for a sustainable future: Oxford, Oxford University Press, 584-595.

CaFCP, California Fuel Cell Partnership: http://www.fuelcellpartnership.org last accessed 4/3/2005

(1) Mission: (/aboutus.html)

(2) Members: (/about_members.html)

(3) Goals: (/about_goals.html)

(4) Fueling Stations: (/fuel-vehl_map.html)

DOE, Spotlight on FreedonCAR and Fuel Partnership: http://www.energy.gov.engine/content.do?PUBLIC_ID=11548&BT_CODE=ES_HYDROGEN&TT_CODE=SPOTLIGHTDOCUMENT last accessed 4/2/2005

Earth & Sky, 2005, Making Hydrogen Fuel, transcript from Edge of Discovery radio series: http://www.earth&sky.com/shows/edgeshow.php?t=20050209 last accessed 3/24/05.

Genesis World Energy, last accessed 3/28/2005

(1), Homepage: http://genesis-scientific.org/genesis_world_energy.htm

(2), Questions and Answers about technology: (/questions-technology.htm)

Hammerschlag, R. and Mazza, P., 2005, Questioning Hydrogen: Energy Policy, 33, 2039-2043.

Jones, L.W., 1971, Liquid Hydrogen as a Fuel for the Future: Science, v. 174, no. 4007, 367-370.

Mazda, An Environmentally friendly brand message: the hydrogen rotary engine vehicle ‘RX-8 Hydrogen RE’ (pdf): http://www.mazda.com/environment/ last accessed

NEDP, 2001, National Energy Policy: Washington, DC, U.S. Government Printing Office, p100-102.

NREL, National Renewable Energy Laboratory’s Hydrogen, Fuel Cells, & Infrastructure Technologies Program: http://www.eere.energy.gov/hydrogenand fuelcells/ last accessed 3/18/2005.

PESWiki, Bar-Gadda LLC: http://peswiki.com/index.php/Directory%3Bar-Gadda_LLC last accessed 3/24/05

Service, R.F., 1999, Binging Fuel Cells Down to Earth: Science, v.285, no.5428, 682&684-685.

USCAR: <http://www.uscar.org> last accessed 4/2/2005

(1), FreedomCAR Partnership homepage: (/freedomcar/)

(2), FreedomCAR media release: (/media/releases/freedomcar.html)

Voss, D., 1999, Company Aims to give Fuel Cells a Little Backbone: Science, v.285, no.5428, 683.

Wikipedia, online elcyclopedia http://en.wikipedia.org/wiki last accessed 3/18/2005.

(1) Hydrogen Fuel: (/Hydrogen_fuel).

(2) Polymer Electrolyte Membrane Fuel Cells: (/PEMFC).

(3) Electrolyte: (/electrolyte).

Winsche, W.E. et al., 1973, Hydrogen: Its Future Role in the Nation’s Energy Economy: Science, v. 180, no. 4093, 1325-1332.