1. www.kostic.niu.edu © MMIV* Prof. M. Kostic FUEL-CELL AND HEAT-ENGINE ENERGY-CONVERSION COMPARATIVE ANALYSIS FUEL-CELL AND HEAT-ENGINE ENERGY-CONVERSION COMPARATIVE ANALYSIS “ An Actual Engineering Topic! " Prof. M. Kostic Mechanical Engineering Mechanical Engineering NORTHERN ILLINOIS UNIVERSITY

2. www.kostic.niu.edu © MMIV* Prof. M. Kostic Hydrogen Fuel Cell…

3. www.kostic.niu.edu © MMIV* Prof. M. Kostic TABLE I: Energy-to-work conversion efficiencies Engine/ProcessEfficiency % Otto (gasoline) engine25-35 Diesel engine30-40 Gas turbine30-40 Steam turbine30-40 Nuclear, steam turbine30-35 Combined gas/steam turbines40-55+ Fuel cell (hydrogen, etc.)40-60+ Photovoltaic cell10-20 Windmill30-40 (59% limit) Hydro turbine80-85 Electro-mechanical motor/generator80-95

4. www.kostic.niu.edu © MMIV* Prof. M. Kostic Chemical reaction

5. www.kostic.niu.edu © MMIV* Prof. M. Kostic Maximum possible reversible work

6. www.kostic.niu.edu © MMIV* Prof. M. Kostic Enthalpy of hydrogen formation or combustion

7. www.kostic.niu.edu © MMIV* Prof. M. Kostic Efficiency of a hydrogen fuel-cell

8. www.kostic.niu.edu © MMIV* Prof. M. Kostic Efficiency of a hydrogen fuel-cell (2)

9. www.kostic.niu.edu © MMIV* Prof. M. Kostic Standard Formation Enthalpy (h f ) and Gibbs Free Energy (g f ) for Water-Vapor(g) and Water-Liquid(l) [in scale]. 95% 100% 83%

10. www.kostic.niu.edu © MMIV* Prof. M. Kostic Maximum adiabatic combustion temperature

11. www.kostic.niu.edu © MMIV* Prof. M. Kostic Combustion entropy generation and work lost due to entropy generation (combustion irreversibility)

12. www.kostic.niu.edu © MMIV* Prof. M. Kostic Combustion Second Law efficiency (i.e., work availability, or exergy efficiency)

13. www.kostic.niu.edu © MMIV* Prof. M. Kostic Heat engine, constant T ad temperature, ideal Carnot cycle

14. www.kostic.niu.edu © MMIV* Prof. M. Kostic Heat engine, constant and variable temperature, ideal Carnot cycle

15. www.kostic.niu.edu © MMIV* Prof. M. Kostic Heat engine, constant temperature Carnot cycle

16. www.kostic.niu.edu © MMIV* Prof. M. Kostic Heat engine, variable temperature, ideal Carnot cycle

17. www.kostic.niu.edu © MMIV* Prof. M. Kostic Conclusion

18. www.kostic.niu.edu © MMIV* Prof. M. Kostic Conclusion…... the practical efficiencies are usually half of their theoretical limits, about 35% and 50% for heat engines and fuel cells, respectively. Still, further developments are needed to overcome fuel-cell limitations in low power density and competitive cost.

19. www.kostic.niu.edu © MMIV* Prof. M. Kostic No Limits … No Limits … The Future Belongs To… … Whoever Gets There First NO SPEED LIMIT

20. www.kostic.niu.edu © MMIV* Prof. M. Kostic You may contact Prof. Kostic at: mailto: kostic@niu.edu mailto: kostic@niu.edu or on the Web: www.kostic.niu.edu www.kostic.niu.edu http:// prof.mkostic.com http:// prof.mkostic.com Prof. M. Kostic Mechanical Engineering Mechanical Engineering NORTHERN ILLINOIS UNIVERSITY