ps3_economic -...

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10.391J/1.818J/2.65J/3.564J/11.371J/22.811J/ESD166J SUSTAINABLE ENERGY IAP 2007 Homework #3 Due January 23, 2007 Energy Systems Analysis In class example problems 1. Rocky and Rochelle Jones have invented a new energy converter called MEGA (an abbreviation for M illennial E nergy for G reen A pplications ) that is under consideration for acquisition by MITY Industries. The MEGA system supposedly directly converts natural gas to electricity by harnessing the “intrinsic” chemical energy available by reacting natural gas (essentially pure CH 4 ) with O 2 in air in an electrochemical fuel cell. According to the inventors, “this direct conversion avoids the inherent limitations of the 2 nd Law of Thermodynamics imposed on conventional power cycle systems.” Rocky and Rochelle claim that “heat to work” efficiencies of over 90% are achievable with the MEGA . This level of performance seems very high given that currently available, state- of-the-art integrated combined cycles that couple gas and steam turbine technologies to produce electric power at efficiencies approaching 60% with CH 4 feeds. Another claimed advantage of the MEGA system is its scalability to provide high efficiency power over a wide range of capacities (from 1 kW to 10MW) needed for distributed power application in remote regions of the world. Unfortunately, the details of how the MEGA operates are sketchy. We do know that air containing 20% O 2 enters at ambient conditions and only CO 2 , N 2 , and H 2 O vapor exit the MEGA again at ambient conditions. The annual average ambient air temperature on the North Slope is approximately 0 ° C. Selective thermodynamic data are also available (see end of problem statement). (a) What is the maximum possible power that would be produced from a steady state flow rate of 1 mol/s of pure CH 4 at 1 bar, 200C available from a gas processing plant on the North Slope of Alaska? State and justify any assumptions made. A known thermodynamics expert, Speedo Gibbs, was hired by MITY Industries to investigate, as they are skeptical that a direct CH 4 fuel cell has ever been operated successfully. Speedo rapidly dismantles a prototype MEGA device and finds two major components (1) a chemical reactor that catalytically reforms CH 4 into H 2 and (2) a conventional Pt-catalyzed electrochemical H 2 -O 2 fuel cell similar to those found in the NASA space shuttle. Speedo concludes that the overall reaction of CH 4 occurs by a two step process: steam reforming plus water gas shift conversion (Rx (1)), to generate H 2 followed by electrochemical conversion in the fuel cell (Rx (2)). Cite as: Jefferson Tester, Elisabeth Drake, Frank Incropera, Michael Golay, course materials for 10.391J/1.818J/2.65J/
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This note was uploaded on 11/27/2011 for the course CHEMICAL E 10.302 taught by Professor Clarkcolton during the Fall '04 term at MIT.

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ps3_economic -...

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