The values of absolute exergy and exergetic efficiency depend on the assumed values of the “reference states,” which are essentially a model of the environment of the processes and components considered. The environmental model plays an important role in any optimization process that uses any form of exergy-based analysis. This paper examines the influence of eleven previously proposed models for the environment on the absolute values of the exergy and on the exergetic efficiencies, associated with the operation of three different power plants: a methane cogeneration plant, a coal-fired plant, and a dual-flash geothermal power plant. It is observed that although there are some common characteristics in most of the values obtained from all the models, the absolute exergies and exergetic efficiencies calculated using some of these models deviate substantially from those obtained with the others. The reasons for these deviations are also examined here.

1.
Ahrendts
,
1980
, “
Reference States
,”
Energy—The International Journal
, Vol.
5
, pp.
667
677
.
2.
Ahrendts, I., 1977, Die Exergie chemisch reaktionsfahiger System, VDI-Verlag, Dusseldorf, Germany.
3.
AIP, 1975, Efficient Use of Energy, AIP Conference, American Institute of Physics.
4.
Alvarado
S.
, and
Gherardelli
C.
,
1994
, “
Input-Output Exergoeconomic Optimization of Multicomponent-Multiproduct Systems Methodology
,”
Energy—The International Journal
, Vol.
19
, No.
2
, pp.
251
258
.
5.
Arena, A. P., 1997, Analisi Termoeconomica di Cintrali di Cogenerazione, Ph.D. dissertation, Departimento di Energeticam, Politecnico di Torino, Italy.
6.
Arena, A. P., Borchiellini, R., and Cali, M., 1996, “Studio di Sensibilita dell’effetto del Sistema Termodinamico di Referimento sulla Analisi Termoeconomica,” Associazioni Termotecnica Italiana-51st Congress, Udine, Italy.
7.
Babcock and Wilcox Company, 1978, Steam, Third Edition, New York, NY.
8.
Baelir
H. D.
, and
Schmidt
E. F.
,
1963
, “
Definition and Calculation of Fuel Exergy (in German)
,”
Brennstoff-Warme-Kraft
, Vol.
16
, No.
12
, pp.
589
596
.
9.
Bejan, A., Tsatsaronis, G., and Moran, M., 1996, Thermal Design and Optimization, John Wiley and Sons, New York, NY.
10.
Bosnsjakovic
F.
,
1963
, “
Reference State for a Exergy of a Reacting System (in German)
,”
Forsh. Ing.-We.
, Vol.
29
, No.
5
, pp.
151
152
.
11.
Brodyansky, V. M., Sorin, M., and LeGoff, P., 1994, The Efficiency of Industrial Processes: Exergy Analysis and Optimization, Elsevier Science, Amsterdam, Holland.
12.
Brzustowski
T. A.
,
1980
, “
Toward a Second-Law Taxonomy of Combustion Processes
,”
Energy—The International Journal
, Vol.
5
, No. pp.
743
755
.
13.
Eisermann
W.
,
Johnson
P.
, and
Conger
W. L.
,
1980
, “
Estimating Thermodynamic Properties of Coal, Char, Tar and Ash
,”
Fuel Processing Technology
, Vol.
3
, pp.
39
53
.
14.
Frangopoulos
C. A.
,
1994
, “
Application of the Thermoeconomic Functional Approach to the CGAM Problem
,”
Energy—The International Journal
, Vol.
19
, No.
3
, pp.
323
342
.
15.
Fratzcher
W.
, and
Gruhn
G.
,
1965
, “
The Meaning and Definition of A Environment State for Exergetic Investigations (in German)
,”
Brennstoff-Warme-Kraft
, Vol.
17
, No.
7
, pp.
337
341
.
16.
Gaggioli, R. A., and Petit, P. J., 1976, “Second Law Analysis for Pinpointing the True Inefficiencies in Fuel Conversion Systems,” Symposium of Integrated Synfuel Systems, American Chemical Society.
17.
Gallo
W. L. R.
, and
Malanez
L. F.
,
1990
, “
Choice of A Reference State for Exergetic Analysis
,”
Energy—The International Journal
, Vol.
15
, pp.
113
121
.
18.
Kameyama
H.
,
Yoshida
K.
,
Yamauchi
S.
, and
Fueki
K.
,
1982
, “
Evaluation of Reference Exergies for the Elements
,”
Applied Energy
, Vol.
11
, pp.
69
83
.
19.
Kestin
J.
,
1980
, “
Availability: The Concept and Associated Terminology
,”
Energy
, Vol.
5
, pp.
679
692
.
20.
Khalifa, H. E., and Michaelides, E. E., 1978, “The Effect of Noncondensable Gases on the Performance of Geothermal Steam Power Systems,” Brown University Report No. CATMEC/28, Providence, RI.
21.
Knacke, O., Kubaschewski, O., and Hesselman, K., 1991, Thermochemical Properties of Inorganic Substances, 2nd Edition, Springer-Verlag.
22.
Kreith, F., and Kreider, J. F., 1978, Principles of Solar Engineering, McGraw-Hill, New York, NY.
23.
Michaelides
E. E.
,
1980
, “
Separation of Noncondensables in Geothermal Installations by Means of Primary Flashing
,”
Transactions of the Geothermal Resources, Council
, Vol.
4
, pp.
515
518
.
24.
Moran, M. J., 1982, Availability Analysis: A Guide to Efficient Energy Use, Prentice Hall, Englewood Cliffs, NJ.
25.
Morris
D.
, and
Szargut
J.
,
1986
, “
Standard Chemical Exergy of Some Elements and Compounds on the Planet Earth
,”
Energy—The International Journal
, Vol.
11
, No.
8
, pp.
733
755
.
26.
Pruschck
R.
,
Oeljeklaus
G.
,
Brand
V.
,
Haupt
G.
,
Zimmermann
G.
, and
Ribberink
J.
,
1995
, “
Combined Cycle Power Plant with Integrated Coal Gasification, Co Shifting and CO2 Washing
,”
Energy Conversion and Management
, Vol.
36
, No.
6–9
, pp.
797
800
.
27.
Reistad, G. M., 1975, Journal of Engineering for Power, p. 439.
28.
Riekert
L.
,
1974
, “
The Efficiency of Energy Utilization in Chemical Processes
,”
Chemical Engineering Science
, Vol.
29
, pp.
1613
1620
.
29.
Rodri´guez, L., 1978, “Thermodynamics: Second Law Analysis,” ACS Symposium Series 122, American Chemical Society, Washington, DC.
30.
Stepanov, C. S., 1990, Chemical Energy and Exergy of Substances (in Russian), Nauka, Novosibirsk, Russia.
31.
Stepanov
V. S.
,
1995
, “
Chemical Energies and Exergies of Fuels
,”
Energy—The International Journal
, Vol.
20
, No.
3
, pp.
235
242
.
32.
Sussman
V. M.
,
1980
, “
Steady-Flow Availability and the Standard Chemical Availability
,”
Energy—The International Journal
, Vol.
5
, pp.
793
802
.
33.
Szargut, J., Morris, D. R., and Steward, F., 1988, Exergy Analysis of Thermal, Chemical, and Metallurgical Processes, Hemisphere Publishing Company, New York, NY.
34.
Szargut, J., and Petela, R., 1965, Exergy (in Polish), Warsaw, Poland.
35.
Tsatsaronis
G.
, and
Pisa
J.
,
1994
, “
Exergoeconomic Evaluation and Optimization of Energy Systems—Application to the CGAM Problem
,”
Energy—The International Journal
, Vol.
19
, No.
3
, pp.
287
321
.
36.
Tsatsaronis, G., Pisa, J., and Gallego, J., 1989, Thermodynamic Analysis and Improvement of Energy Systems, Proceedings of the International Symposium, Beijing, China, Pergamon Press, pp. 195–200.
37.
Valero
A.
,
Lozano
M.
,
Serra
L.
,
Tsatsaronis
G.
,
Pisa
J.
,
Frangopoulos
C.
, and
von
Spakovsky
,
1994
, “
CGAM Problem: Definition and Conventional Solution
,”
Energy—The International Journal
, Vol.
19
, No.
3
, pp.
279
286
.
38.
Valero
A.
,
Lozano
M.
, and
Torres
C.
,
1994
, “
Application of the Exergetic Cost Theory to the CGAM Problem
,”
Energy—The International Journal
, Vol.
19
, No.
3
, pp.
365
381
.
39.
Van Gool
W.
,
1992
, “
Exergy Analysis of Industrial Processes
,”
Energy—The International Journal
, Vol.
17
, No.
8
, pp.
791
803
.
40.
Van Gool, W., 1997, “Thermodynamics and Chemical References for Exergy Analysis,” Florence World Energy Research Symposium, Florence, Italy, SGE Editoriali, pp. 949–957.
41.
Von Spakovsky
M.
,
1994
, “
Application of the Functional Analysis to the Analysis and Optimization of the CGAM Problem
,”
Energy—The International Journal
, Vol.
19
, No.
3
, pp.
343
364
.
42.
Wepfer, W., and Gaggioli, R., 1978, “Reference Datums for Available Energy,” ACS Symposium Series 122, American Chemical Society, Washington, DC.
43.
Yantovkskii
E. Y.
,
Wall
G.
,
Lindquist
L.
, and
Tryggstad
J.
,
1994
, “
Exergoeconomics of an EOR (OCDOPUS) Project
,”
Energy—The International Journal
, Vol.
19
, No.
12
, pp.
1275
1278
.
This content is only available via PDF.
You do not currently have access to this content.