Fuel cells internal combustion

The fuel used to make solar-hydrogen is free (sunshine) and unlimited, the raw material for H2 is water, and the emission when burning the H2 in fuel cells, internal combustion engines, or in power plants is distilled water. The cost of building the solar-hydrogen plants will be known once the demonstration power plant described in this book is built. It might turn out that this cost is already competitive but whatever it is, we know that it will drop by an order of magnitude when the mass production of ultrathin-film solar collectors and reversible fuel cells is started. 

Development of scaled-down versions of H2 PSA processes producing 0.05 - 1.0 MMSCFD H2 will be necessary for supporting the forth coming hydrogen economy . They will serve numerous Ha based applications like H2 fuel-cells, internal combustion vehicles, stationary or portable power generators, power generators for remote locations, etc [16]. 

The competition—more fuel-efficient internal combustion engine vehicles—is getting tougher, so the incremental benefits of using fuel cell vehicles will be smaller than if they were replacing existing vehicles. 

In this section, details of an easily controllable, safe method for producing high-purity H2 gas are described. This method of generating H2 gas is particularly suitable for providing a clean source of H2 gas for use as an anodic fuel in fuel cells or as a fuel for internal combustion engines in transportation applications. This compact, portable H2 generator is based on a non-pressurized, aqueous solution of alkaline sodium borohydride (NaBH, tetrahydroborate). As found by Schlesinger et al.,1 when aqueous NaBH... 

One problem is cost-effectiveness, hydrogen must be able to compete with alternative strategies including more fuel-efficient internal combustion engine vehicles. In the near term, hydrogen is likely to be made from fossil fuel sources. The annual operating costs of fuel cell power are likely to be higher than those of the competition in the foreseeable future. 

A further factor has to be considered, namely, the purity of the hydrogen. As a fuel for internal combustion engines, purity is not a prime consideration and hydrogen from almost any source will be suitable, provided that sulfur is removed. With low-temperature types of fuel cell, however, purity is a critical parameter since the electrocatalysts are subject to poisoning by many contaminants, several of which are found in fossil fuels see Section 6.3, Chapter 6. In this regard, hydrogen produced by the electrolysis of water is much purer and may prove to be the preferred source for this application, despite its higher cost. 

Hydrogen-storage alloys (18,19) are commercially available from several companies in the United States, Japan, and Europe. A commercial use has been developed in rechargeable nickel—metal hydride batteries which are superior to nickel—cadmium batteries by virtue of improved capacity and elimination of the toxic metal cadmium (see BATTERIES, SECONDARYCELLS-ALKALINe). Other uses are expected to develop in nonpolluting internal combustion engines and fuel cells (qv), heat pumps and refrigerators, and electric utility peak-load shaving. 

In internal combustion engine, unless otherwise noted. Fuel cells. 

In the fuel cell hydrogen is used two to three times as efficiendy as in an internal combustion engine. Hence, when utilized in a fuel cell, hydrogen can cost two to three times that of more conventional fossil fuels and stiU be competitively priced, ie, as of this writing the market price for hydrogen when used in a fuel cell and produced by electrolysis is competitively priced with gasoline. 

Fuel cells, which rely on electrochemical generation of electric power, could be used for nonpolluting sources of power for motor vehicles. Since fuel cells are not heat engines, they offer the potential for extremely low emissions with a higher thermal effidency than internal combustion engines. Their lack of adoption by mobile systems has been due to their cost, large size, weight, lack of operational flexibility, and poor transient response. It has been stated that these problems could keep fuel cells from the mass-produced automobile market until after the year 2010 (5). 

Cogeneration encompasses several distinct thermodynamic processes of simultaneous heat and power production. One utilizes air as a medium, another steam, a third employs heat rejected from a separate combustion process, such as an internal-combustion engine, and a fourth utilizes a thermochemical process such as found in a fuel cell. Although each process is distinct, they are often combined together to inaxiniize the energy production in a single thermodynamic system. 

Transportation accounts for about one-fourth of the primary energy consumption in the United States. And unlike other sectors of the economy that can easily switch to cleaner natural gas or electricity, automobiles, trucks, nonroad vehicles, and buses are powered by internal-combustion engines burning petroleum products that produce carbon dioxide, carbon monoxide, nitrogen oxides, and hydrocarbons. Efforts are under way to accelerate the introduction of electric, fuel-cell, and hybrid (electric and fuel) vehicles to replace sonic of these vehicles in both the retail marketplace and in commercial, government, public transit, and private fleets. These vehicles dramatically reduce harmful pollutants and reduce carbon dioxide emissions by as much as 50 percent or more compared to gasoline-powered vehicles. 

Current research on fuel cells is directed toward the replacement of the internal combustion engine. To do this, hydrogen must be stored in the vehicle and replenished from time to time at filling stations. Three kilograms of hydrogen should be enough to drive a small car 500 km (300 miles) between fill-ups. 

Fuel cells such as the one shown on Fig. 3.4a convert H2 to H20 and produce electrical power with no intermediate combustion cycle. Thus their thermodynamic efficiency compares favorably with thermal power generation which is limited by Carnot-type constraints. One important advantage of solid electrolyte fuel cells is that, due to their high operating temperature (typically 700° to 1100°C), they offer the possibility of "internal reforming" which permits the use of fuels such as methane without a separate external reformer.33 36... 

As the reaction shows, a hydrocarbon fiiel cell produces carbon dioxide, a greenhouse gas. These fiiel cells would nevertheless be less polluting than internal-combustion engines, because fuel cells are more efficient and do not generate polluting b q)roducts such as CO and NO . ... 

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