Evolution To The Fuel Cell

The hydrogen air fuel cell is a type of battery that uses the reaction of hydrogen and oxygen to produce electric power without the intervening production of heat. The fuel cell is extremely efficient when compared with devices using heat to produce electric power. The most efficient coal or nuclear plants convert, at the very most, 40% of the heat energy, to electricity. Fuel cells easily convert 60% of the potential energy of hydrogen to electricity. At low load conditions, they can operate at efficiencies higher than 85%. The hydrogen air fuel cell will become extremely important in the mature phases of the Fusion-Hydrogen energy system.

The fuel cell consists of two porous metal plates separated by a layer of a material that conducts hydrogen ions, hydroxyl ions and water. The conductive material is termed an electrolyte. It can be either a solid or a liquid. In its general form, the fuel cell appears to be constructed in the same manner as an electrolyzer. In fact single units have been constructed that can operate as either electrolyzer of fuel cell. Like many dual purpose mechanisms it does not do either job as well as a single purpose device.

One metal plate is optimized for the hydrogen and the other for oxygen reactions. Both plates have a tree shaped set of channels in the side opposite the electrolyte for the transport of the gas. At the plate optimized for hydrogen reactions, the hydrogen gas reacts to give up an electron and becomes a positively charged hydrogen ion. The hydrogen ion drifts into the electrolyte and the electron passes through the metal as a current flow. At the plate optimized for oxygen reactions, oxygen from the air reacts with the water in the electrolyte and two electrons produce two negatively charged hydroxyl ions. In the electrolyte, the negatively charged hydroxyl ions react with the positively charged hydrogen to produce uncharged water. The electrons produced by the hydrogen reaction are driven through the external circuit to the oxygen electrode to replace those consumed in making the hydroxyl ions. The electrons flowing in the external circuit constitute the power output of the fuel cell. This electron flow can be used for the same purposes as any other electron flow.

There are several types of fuel cells. They differ in the electrolyte used. This solid polymer fuel cell is used for an example because it is the type of fuel cell under the most intense development. It is likely

191 Editors, "Bare Mountains, Poor people", The Economist, Vol. 361, No. 8246, November 3, 2001, Page 24

192 Abelson, Philip H., "Applications of Fuel Cells", Science, Vol. 248, No. 4962, June 22, 1990, Page 1469

to be the fuel cell that will be used in transportation. Other types of fuel cell may be used in stationary applications.

There are four types of fuel cells in development. They differ in the electrolyte they use, but the mechanical and chemical fundamentals are similar. The electrolytes under investigation are Phosphoric Acid, Molten Carbonate, Solid Oxide and Solid Polymer. The Phosphoric acid cells operate at temperatures of 180 to 210 degrees Celsius. Molten carbonate cells operate at 600 to 700 degrees Celsius. Solid oxide Cells operate at 650 to 1000 degrees Celsius. These temperatures are uncomfortably high for home use and impractically high for automotive use. Only the Solid Polymer cells operate at a temperature range, 80 to 100 Celsius, a suitable for use in the home or automobile.

ELECTRIC POWER OUTPUT LEADS

ELECTRIC POWER OUTPUT LEADS

Figure 6.7 Schematic Diagram Solid Polymer Fuel Cell.

The other fuel cells can use hydrogen as the fuel without a problem, but they were primarily developed to function on hydrocarbon fuels. 193 Their use will continue for industrial applications but in this book only the solid polymer fuel cells will be considered.

The fuel cell offers many advantages as a source of electric power. It is efficient, quiet, and produces no polluting substances. Fuel cells are entering the market today for everything from military

193 Loyd, Alan C., "The Power Plant in Your Basement", Scientific American, Vol. 281, No. 1, July 1999, Page 72

Figure 6.8 The Ballard Line of Fuel Cells

Picture supplied by Ballard Power Systems Inc.

Figure 6.8 The Ballard Line of Fuel Cells

Picture supplied by Ballard Power Systems Inc.

Ballard® automotive fuel cell stacks require a high power density. Ballard® has continually increased the power density of its fuel cells, from 3kW/ft3 (100 Watts/liter_ in 1989 (far right) to over 37.1kW/ft3 (1310Watts/liter) in 1999, (far left) The words in italics were supplied by Ballard Power Systems Inc.

applications to long live power supplies for lap top computers. 194 As the hydrogen energy system matures, almost all new sources of electricity will be fuel cells. Fuel cells are only slightly affected by scale. At similar levels of development the cost per unit of generating capacity is only slightly higher for small cells than for large cells. The efficiency is about the same for large or small cells. Since large size probably offers negligible cost advantage, the fuel cells will be made in sizes appropriate for single specific users. These cells will be placed at the point of use of the electric power. There will be no need for the transmission of electric power over long distances. As existing electric power plants wear out, they will be deactivated. Their previous customers will install on-site hydrogen fuel cells. The on-site fuel cells, and a modest amount of local storage, will be connected to the pipeline supply network. Ultimately, this will eliminate all the central power plants and the need for transmission lines. Elimination of power lines will be another way in which the adoption of the fusion energy system will improve the environment.

194 Editors, "Batteries not Included", The Economist, Vol. 359, No. 8227, Page 28

Today Ballard Power Systems Inc. 9000 Glenlyon Parkway, Burnaby BC, Canada V5J5J9 195 is a major developer and producer of fuel cells. They produce a variety of cells with Power ratings from 1 Kilowatt to as large as 250 Kilowatts. Figures 6.8 through Figure 6.12 show some Ballard's capabilities and products. The wording in itallic type was supplied by Ballard Power Systems Inc.

In addition to the elimination of power-lines, there are several other advantages for full implementation of on-site fuel cells. Massive power outages such as occurred in the northeast portion of the United States in the late sixties will be impossible. All the electric power will be generated from hydrogen at or near the end use site. The hydrogen supply used for the generation will be protected from interruption by local storage and the massive storage capacity of the distribution pipeline system. Should a serious failure occur in the system, automatic isolation valves would close to prevent leakage of the pipeline gas. If the break is far from the user, hydrogen will be available for days from the high-pressure gas remaining in the pipes. If the break is quite close to the user, local storage at the user site (in relatively low cost high pressure gas bottles) will provide a supply until the main supply line is repaired.

Figure 6.9 Ballard Mark 9000 Automotive Fuel Cell

Picture supplied by Ballard Power Systems Inc.

Ballard® unveiled its next generation fuel cell stack, the Mark 9000, in January 2000. The fuel cell stack is incorporated in the Rallarct' Mark 900 Series Fuel Cell Power Module. It incorporates low-cost materials and is designed for manufacturing in automotive volumes. The words in italics were supplied by Ballard Power Systems Inc.

195 http://www.ballard.com/

The fuel cell generator produces only direct current as compared to the 60 Hz (United States) and 50 Hz (Europe) alternating current used in most distribution systems. Only devices using electric energy for the production of heat (electric lights, stoves and furnaces) can operate on direct current without modification. All appliances with electric motors, or multi-voltage electronic power supplies (radios, television, computers etc.), require appropriate alternating current. Fluorescent lights require alternating current. For the devices that require alternating current, two solutions are possible: build solid state converters to change the direct current output of the fuel cell to alternating current, or introduce a new generation of appliances that can function on direct current.

The adoption of converters to produce alternating current will likely be the better of these two options. The cost of converting direct current to alternating current is low. The low cost will override other considerations. A television set provides a good example of the advantages of alternating current. In a current television set, the input power goes directly to a transformer. The transformer has several taps at different voltages. A low voltage tap is rectified to direct current to provide the power for the transistorized signal processing section. A second tap produces a modest voltage alternating-source for the heater of the picture tube filaments. Another transformer produces a 20,000-volt output to accelerate the electron beam. To build a direct current television set the first thing required is a converter producing alternating current to provide the necessary differing voltages. This will be required because it is nearly impossible to convert one direct current voltage to another.

Figure 6.10 Ballard One Kilowatt Portable Fuel Cell

Picture supplied by Ballard Power Systems Inc.

Figure 6.10 Ballard One Kilowatt Portable Fuel Cell

Picture supplied by Ballard Power Systems Inc.

The 1 kW Portable fuel cell generator is a fully automated power system that converts hydrogen fuel and oxygen from the air directly into D. C. electricity. Water is the only by-product of the reaction. This fuel cell generator that operates at low pressures provides reliable, clean, quiet and efficient power. It is small enough to be carried to where ever power is needed. The BallardF 1 kWfuel cell generator provides DC electricity when used directly and AC electricity when used in conjunction with an off-the-shelf inverter. The words in italics were supplied by Ballard Power Systems Inc.

Most electronic equipment shares the television set's need for a number of differing voltages for the operation of individual components. This alone may be sufficient justification for the inclusion of a direct current to alternating current converter in fuel cell power systems. In addition, alternating current electric motors are more suitable in most applications. They tend to operate at a rotational speed controlled by the frequency of the current. If completely unloaded they speed up to this fixed velocity and accelerate no further. Many types of direct current motors, if operated unloaded, will continue to accelerate until they fail. A belt driven fan operated by an alternating current motor is undamaged by the failure of the belt. A direct current motor will require a special safety circuit to shut it down in case of belt failure. If the belt and the safety circuit both fail, the motor will speed up until it destroys itself.

The high reliability of the hydrogen fuel cell electrical supply system will be of value to all, but will be of critical importance for defense, hospital, police, fire and similar emergency facilities. Currently, all of these facilities must add extra cost emergency power systems to back-up the unreliable grid supply electric power system. If not properly maintained they can fail when needed. This would leave the emergency facility without power. Today these emergency systems present difficult maintenance problems because they are used sporadically. With the hydrogen fuel cell electrical energy system, there is no need for extra emergency power.

Figure 6.11 Ballard 100-Watt Fuel Cell

Picture supplied by Ballard Power Systems Inc.

Figure 6.11 Ballard 100-Watt Fuel Cell

Picture supplied by Ballard Power Systems Inc.

This picture shows the Ballarcf 100-Watt portable fuel cell system. The "ambient" fuel cells systems that operate at low pressures provide reliable, clean, quiet, and efficient power. They are small and rugged enough to be carried or transported to wherever power is needed The words in italics were supplied by Ballard Power Systems Inc.

In any system, the user will have several fuel cells to supply the necessary power. If any of these should fail, the others can take up the added load. Local hydrogen storage will ensure hydrogen is available when the main pipeline system is out. The only concession the emergency facility must make will be the addition of extra hydrogen storage tanks to extend the time it can survive interruption of the main supply.

Figure 6.12 Ballard Home Size Fuel Cell

Picture supplied by Ballard Power Systems Inc.

Figure 6.12 Ballard Home Size Fuel Cell

Picture supplied by Ballard Power Systems Inc.

Ballard Generating System's first field trial 250 KW Natural gas Polymer, Electrolyte Membrane (PEM) Fuel Cell Power Generator is sited at the Crane Naval Surface Warfare Center, in Indiana, for a two-year demonstration and testing program. This system would be smaller and simpler if it were using hydrogen as the fuel. The words in italics were supplied by Ballard Power Systems Inc.

The fuel cells have extraordinary efficiency. Under very low loads, they are able to operate 85% to 95% efficiency. Under heavy loads, the efficiency may drop below 50%. The remaining waste energy must be rejected as heat at about the boiling point of water. In many situations, it will be possible to recover this energy for space heating or water heating. When the dual use energy recovery system is utilized, it will raise the total combined system energy efficiency to almost 100%.

The fuel cell coupled into the hydrogen energy system will provide a highly desirable source of electric power for virtually all the applications currently using electricity. In most applications, the user will be totally unaware the electric power is made on-site rather than at some remote power plant. The change will be greater reliability of electric supply and less use of electricity for purposes that can be served as well or better by hydrogen gas. In this category are heating, cooking, clothes drying and, possibly, air conditioning.

Guide to Alternative Fuels

Guide to Alternative Fuels

Your Alternative Fuel Solution for Saving Money, Reducing Oil Dependency, and Helping the Planet. Ethanol is an alternative to gasoline. The use of ethanol has been demonstrated to reduce greenhouse emissions slightly as compared to gasoline. Through this ebook, you are going to learn what you will need to know why choosing an alternative fuel may benefit you and your future.

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