Today, humans get most of their energy from fossil fuels. We know this rate of consumption isn’t sustainable. Will fuel cells be the primary energy source of tomorrow?

Humans have always needed energy. Throughout history, humans have developed various systems to produce this energy. Just as man was created, so, too, were the energy sources we need to survive. We just have to find them. Finding and extracting this energy has been enormously important to human civilizations.

Today, accelerated population growth, technological advancements, and growing industrial sectors have contributed to a rapid increase in our energy demand. The major portion of energy (around 86%) consumed worldwide is generated from fossil fuels (as of 2013). Diminishing fossil fuel reserves underline the significance of new and renewable energy sources. One of the first places scientists are looking is our first source of energy: the sun. Its light has been utilized by societies for power and food throughout history, and today, scientists are searching for new ways to utilize the sun. Another field being researched is electrical energy. From this research, fuel cells have been developed as alternatives to fossil fuels. Are there any differences between battery cells that we use in devices like flashlights, radio, and toys, and these fuel cells?

Classic batteries provide stored energy, but when they run out, they must be discarded. However, fuel cells are designed as systems that do not store energy, but generate it. While classic battery cells are considered major environmental pollutants, even aside from their short life spans, fuel cells are superior sources of energy. They are:

• Environmentally friendly
• Have high energy output
• Operate silently
• Durable
• Highly efficient
• Offer alternative fuel diversity
• And can be remotely operated

Why is a system with so many advantages not widely used in our daily lives? Fuel cells have not found the common use they deserve because of many reasons: they are difficult to install, the need for high level information and technology to use them, and higher expenses during installation. And then, of course, there are the petroleum companies – cartels, really – that have done everything in their power to block the spread of alternative energies.

The first fuel cell was developed by Sir William Grove in 1839. NASA first used fuel cells in 1952 to supply electric energy to a space craft. In the 1960s, these cells were proven to be valuable for transportation after the production of the first fuel cell powered tractor. In 1966, a vehicle called the Electrovan was designed by General Motors; it worked with a fuel cell (Figure 1). These advances were followed by a fuel cell powered train in the 1980s, a submarine in the 1990s, and eventually planes. In addition to all these applications, recently, fuel cells have been widely used in power plants.

A fuel cell system is made up of an anode, cathode and electrolyte material. As seen in Figure 2, while the separated electrons of fuel (hydrogen) are sent to the anode, they continue their way to the cathode on the circuit; then, the hydrogen ions, with their lost electrons, move on to cathode over the electrolyte and here the circuit is completed by the reaction of air with electrons arriving from the anode. This generates an electric current at the arm where the electrons are routed towards the outer circuit.

Today, fuel cells are manufactured for various goals. It is possible to classify fuel cells according to fuel consumed, the type of oxidizing compound used, or the conversion of consumed fuel to “usable fuel” inside or outside the fuel cell. Aside from these, some fuel cells are also classified by operation temperatures or electrolyte differences. The most common designation is based on the electrolyte type.

Solid oxide fuel cells

Solid oxide fuel cells are the most efficient in terms of converting chemical fuel directly into electrical energy. The basic ideas regarding these cells were presented towards the end of the 19^th century by Nernst and his friends. Furthermore, new theories are still being proposed and experiments carried out, even a century after their discovery.

Solid oxide fuel cells are usually designed to generate power in the range of 1 kW and 2 MW. If we think about a 20 Watt energy saving light bulb that is used to illuminate our room, a solid oxide fuel cell can illuminate in between 50 and 100,000 rooms. These fuel cells are operated between 600 °C – 1,000 °C. Emitted exhaust fumes can be used to enhance the yield by utilizing them in another gas turbine.

The efficiency in this type of hybrid system can reach up to 70%. The oxygen ions in these cells are carried over a solid oxide electrolyte material to react with the hydrogen in the anode at high temperatures. The reaction taking place in the anode and cathode in a solid oxide fuel cell is as follows:

-Anode: 2H₂+2O^2–→2H₂O+4e^–

-Cathode: O₂ + 4e^–→ 2O_2–

-Main reaction in the cell: 2H₂+O₂→2H₂O

Solid oxide fuel cells have many advantages over other fuel cells:

• They have high efficiency compared to all other fuel cells (50–70%).
• Long life span (40,000–80,000 hours).
• Produced from easily accessible materials like ceramics rather than precious metals like platinum and gold
• Fewer problems are encountered during the operation of electrolytes.
• Can produce recyclable waste.

Even though fuel cells are not widely used, they are employed in space works, military projects, uninterrupted power supply systems, mobile power sources, waste water treatment, and vehicles. The power generation and use of solid oxide fuel cell systems in developed countries increases every day. For example, a 40,000 kW’ (40 MW) section of the electric demand in Tokyo, and an 11,000 kW (11 MW) portion of the demand in Rokko Island, are covered by solid oxide fuel cells. The electricity consumption of some malls, homes, and apartment complexes in America, Japan, and Germany are also covered via solid oxide fuel cells.

In 2009, Nissan started using solid oxide fuel cells in its model Nissan X-trail FCV (Fuel Cell Vehicle) and managed to achieve around 40% efficiency. It has been reported that this fuel cell, with a 1 cm³ volume, has a capacity of 2 kW at an operating temperature of 550 °C using hydrogen fuel. The solid oxide fuel cells manufactured by the DELPHI company for commercial and military fields are at 5 kW capacity, with a near 40-50% efficiency. Another major advantage of these fuel cells is that they operate both noise and emission free. With the solid oxide fuel cells that Sweden started using on a ferry called UNDINE, in 2010, a power of 20 kW is generated, and this runs the navigational and radio devices at the harbor.

There are many ongoing studies regarding the use of fuel cells in mobile devices. The fuel cells designed for laptop computers and mobile phones are still in their prototype phases, but are expected to be marketed within a couple of years. Today’s mobile phones, with regular batteries, can only operate for a few days before they need to be recharged. Tomorrow’s phones will be able to function nonstop for a month with fuel cell technology. In addition, laptop computers, which now only last for 3 or 4 hours, will work for 2 or 3 days. These mobile applications are also suitable for military tasks, including land, air, and sea crafts. In terms of stationary applications, giant power plants established outside residential areas will be replaced by more localized power plants, thus shortening power transmission lines and preventing energy loss. This system can even be applied to a domestic scale in our homes.

In fuel cells, electricity is generated when the hydrogen and oxygen supplied in a system reacts with an electrolytic material. Solid oxide fuel cells are predicted to be one of the most common systems to generate electricity in the near future.

To widen the present uses of fuel cells, efforts continue to reduce the cost of its installation expenses and to advance its technology. In conclusion, in a world where our energy dependence increases daily, fuel cells, used as an alternative and renewable energy source, and especially solid oxide fuel cells, are a candidate to be an essential power source in the future. This should be considered as a big opportunity for countries dependent on foreign energy. There are major benefits for researching and investing in fuel cells.
Figure – 1 A minivan powered with fuel cells manufactured by General Motors in 1966.

Figure 2 The schematic outline of the fuel cell

References

• Grove, W.R., (1839), On voltaic series and the combination of gases by platinum. Philosophical Magazine and Journal of Science, 14 (86);127.
• Stone, C., Morrison, A.E., (2002), From criosity to ‘power to change the world’. SolidState Ionics, 152-153:1-13.
• Durmuş S., Bozoklu M., Gökkoyun M., Erat S., Braun A., Metin H., Arı M., (2009). Electrical properties and crystallographic characterization of Gd₂O₃ doped Bi₂O₃ polymorph, San Francisco, CA:Materials Research Scociety. Abstract no:R5.23
• Jung, S., Eric D. Wachsman and Naixiong Jiang,(2002). Structural Stability and Conductivity of Cubic (WO₃)x- (Dy₂O₃)y- (Bi₂O₃)l.x.y, International Jounal of Ionics, Volume 8, Numbers 3-4 , 210- 214.
• Tu, H., Stimming U., (2004). Advances, aging mechanisms and lifetime in solid-oxide fuel cell, Journal of Power Sources, 127 (1-2) :284–293.

Fuel cells are very promising chemical energy conversion devices. Though the first fuel cell was made by William Grove in 1839, they’re just now being explored as a real energy alternative (1). Let’s take a look at how they work: in a fuel cell, electricity is generated by the reaction of hydrogen and oxygen, which forms water. They are similar to batteries and internal combustion engines (ICEs): just as in a combustion engine, where fuel is oxidized, the oxidization of hydrogen generates energy. They’ll work as long as fuel is provided.

Despite these similarities there are some differences that make fuel cells more attractive than batteries and ICEs. A fuel cell works more efficiently and quietly than engines do. When hydrogen is used as fuel, power and drinking water are produced as by-products (2). Having safe by-products answers our concerns regarding older power sources. A battery is dead if it is not re-chargeable; however a fuel cell can be continually reused.

Fuel cells are generally defined by the type of electrolyte used in the cell, and they operate at different temperatures. Alkaline fuel cells (AFCs), proton exchange membrane fuel cells (PEMFCs), and direct methanol fuel cells (DMFCs) are called low-temperature fuel cells. Phosphoric acid fuel cells (PAFCs) are an intermediate-temperature fuel cell. Molten carbonate fuel cells (MCFCs) and solid oxide fuel cells (SOFCs) are called high-temperature fuel cells (3, 4).

They have been mainly used for stationary, transportation, and portable applications. Since the need for electricity in daily life has dramatically increased, reliable and efficient power supplies have become necessary. Over 2,000 stationary fuel cell systems have been built in hotels, schools, and hospitals. Stationary power generation is considered more commercialized among the other fuel cell applications. Today, these systems have reached an efficiency of 40% when a hydrocarbon is used as fuel. Fuel cell systems are also used in telecommunication systems, and these cells provide power between 1 and 5 kW (5).

Fuel cells have been identified as the most probable alternative power source for transportation applications in place of internal combustion engines (ICEs). There are two distinct features of fuel cells that make them a better choice than ICEs. First, their carbon dioxide gas emissions are nearly zero. Second, fuel cells are much more efficient than ICEs – about two to three times (6). Ballard Power Systems have been developing zero-emission-vehicles by using PEMFCs, which have low operating temperatures and a higher power density.

NASA decided to use fuel cells on American spacecrafts in the 1960s. The advantage of using them in spacecraft was that while they were generating electric power, they produced drinkable water for the astronauts. A fuel cell was used as an integral part of the power supply PEMFCs (1kW) in the Gemini crafts and AFCs (1kW) in the Apollo crafts, both of which were a part of NASA’s human spaceflight programs (6).

Portable applications of fuel cells offer electrical power when reaching the electrical grid is not possible. When they are used as power sources outdoors, they help to avoid air and noise pollution (4). Because these portable fuel cells are lighter and more durable than batteries, they have been considered as alternative power sources for mobile phones, laptop computers, and some electronic devices (5). They are also used by the military in battle. A 4 kW PEM generator was built for the U.S. military by Intelligent Energy Ltd., out of Europe (7). Since direct methanol fuel cell systems are much lighter than the indirect systems, they are mostly used as portable power systems.

Although fuel cells have benefits when compared to other power sources, they are not widely used because of their high cost. In 2010, the Energy Information Administration released that the cost of fuel cells is $6.83 per installed watt, which is almost 7 times more expensive than a natural-gas turbine generator plant (8). In 2008, the Honda Clarity produced one of the first hydrogen-powered automobiles; these require very expensive catalysts: platinum (9). A catalyst makes the chemical reactions occur faster. Platinum is still the best catalyst, so this explains the prohibitive cost. A cheaper substitute for platinum is needed for use in automobiles. Another problem is that hydrogen is widely used as fuel for transportation applications. Until there is a sufficient hydrogen infrastructure, car manufacturers will find it hard to mass produce cars that use fuel cells.

Cetin is a freelance science writer.

References

1. Grove, W. R. (1839). On voltaic series and the combination of gases by platinum. Philosophical Magazine and Journal of Science, Series 3,14, 127-130.
2. Hoogers, G. (2003). Fuel Cell Technology Handbook. Boca Raton, FL: CRC Press.
3. Mekhilef, S., Saidur, R., Safari, A. (2012). Comparative study of different fuel cell technologies. Renewable and Sustainable Energy Reviews 16, 981-989.
4. Gencoglu, M. T., Ural, Z. (2009). Design of a PEM fuel cell system for residential application. International Journal of Hydrogen Energy 34, 5242-5248.
5. Andujar, J., Segura, F. (2009). Fuel cells: History and updating. A walk along two centuries. Renewable and Sustainable Energy Reviews 13, 2309-2322.
6. Iovine, John. “Fuel Cells.(composition, energy-generating processes and industry developments and innovations).” Poptronics. Poptronix, Inc. 2001. Retrieved May 17, 2012 from High Beam Research: http://www.highbeam.com/doc/1G1-69015426.html
7. Cowey, K., Green, K., Mepsted, G., Reeve, R. (2004). Portable and military fuel cells. Current Opinion in Solid State and Materials Science 8, 367-371.
8. Administration, U. E. (2010, November). Updated Capital Cost Estimates for Electricity Generation Plants. Retrieved from http://205.254.135.24/oiaf/beck_plantcosts.
9. Muller, R. A. (2012). Energy for Future Presidents: The Science Behind The Headlines. New York: W.W. Norton Company, Inc.