Green Technology and Energy Conversion Efficiency

Movement of H from anode to cathode through cation-permeable membrane Net reaction 2H2 + O2 - 2H2O 

FIGURE 17.7 Cross-sectional diagram of a fuel cell in which elemental hydrogen can be reacted with elemental oxygen to produce electricity directly with water as the only chemical product. 

As an inevitable consequence of the thermodynamics described by the Carnot equation, engines that convert heat to mechanical energy cannot utilize much of the heat, and the waste heat is carried away by an engine cooling system. Typically, a small portion of this heat is used in automotive heaters on cold days. On a broader scale, such as municipal electrical systems, this heat can be used for heating buildings. Such efficiencies are discussed in Section 17.19. 

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