Supercritical carbon dioxide (SCO2) Brayton cycles have the potential to offer improved thermal-to-electric conversion efficiency for utility scale electricity production. These cycles have generated considerable interest in recent years because of this potential and are being considered for a range of applications, including nuclear and concentrating solar power (CSP). Two promising SCO2 power cycle variations are the simple Brayton cycle with recuperation and the recompression cycle. The models described in this paper are appropriate for the analysis and optimization of both cycle configurations under a range of design conditions. The recuperators in the cycle are modeled assuming a constant heat exchanger conductance value, which allows for computationally efficient optimization of the cycle's design parameters while accounting for the rapidly varying fluid properties of carbon dioxide near its critical point. Representing the recuperators using conductance, rather than effectiveness, allows for a more appropriate comparison among design-point conditions because a larger conductance typically corresponds more directly to a physically larger and higher capital cost heat exchanger. The model is used to explore the relationship between recuperator size and heat rejection temperature of the cycle, specifically in regard to maximizing thermal efficiency. The results presented in this paper are normalized by net power output and may be applied to cycles of any size. Under the design conditions considered for this analysis, results indicate that increasing the design high-side (compressor outlet) pressure does not always correspond to higher cycle thermal efficiency. Rather, there is an optimal compressor outlet pressure that is dependent on the recuperator size and operating temperatures of the cycle and is typically in the range of 30–35 MPa. Model results also indicate that the efficiency degradation associated with warmer heat rejection temperatures (e.g., in dry-cooled applications) are reduced by increasing the compressor inlet pressure. Because the optimal design of a cycle depends upon a number of application-specific variables, the model presented in this paper is available online and is envisioned as a building block for more complex and specific simulations.

References

References
1.
Ishiyama
,
S.
,
Muto
,
Y.
,
Kato
,
Y.
,
Nishio
,
S.
,
Hayashi
,
T.
, and
Nomoto
,
Y.
,
2008
, “
Study of Steam, Helium and Supercritical CO2 Turbine Power Generations in Prototype Fusion Power Reactor
,”
Prog. Nucl. Energy
,
50
(
2–6
), pp.
325
332
.10.1016/j.pnucene.2007.11.078
2.
Dostal
,
V.
,
2004
, “
A Supercritical Carbon Dioxide Cycle for Next Generation Nuclear Reactors
,” Ph.D. thesis, Massachusetts Institute of Technology, Cambridge, MA.
3.
Dostal
,
V.
,
Hejzlar
,
P.
, and
Driscoll
,
M. J.
,
2006
, “
The Supercritical Carbon Dioxide Power Cycle: Comparison to Other Advanced Power Cycles
,”
Nucl. Technol.
,
154
(
3
), pp.
283
301
.
4.
Feher
,
E. G.
,
1967
, “
The Supercritical Thermodynamic Power Cycle
,”
Energy Conversion
,
8
(2), pp.
85
90
.10.1016/0013-7480(68)90105-8
5.
Conboy
,
T.
,
Wright
,
S.
,
Pasch
,
J.
,
Fleming
,
D.
,
Rochau
,
G.
, and
Fuller
,
R.
,
2012
, “
Performance Characteristics of an Operating Supercritical CO2 Brayton Cycle
,”
ASME J. Eng. Gas Turbines Power
,
134
(
11
), p.
111703
.10.1115/1.4007199
6.
Iverson
,
B. D.
,
Conboy
,
T. M.
,
Pasch
,
J. J.
, and
Kruizenga
,
A. M.
,
2013
, “
Supercritical CO2 Brayton Cycles for Solar-Thermal Energy
,”
Appl. Energy
,
111
, pp.
957
970
.10.1016/j.apenergy.2013.06.020
7.
Sarkar
,
J.
, and
Bhattacharyya
,
S.
,
2009
, “
Optimization of Recompression S-CO2 Power Cycle With Reheating
,”
Energy Convers. Manage.
,
50
(
8
), pp.
1939
1945
.10.1016/j.enconman.2009.04.015
8.
Turchi
,
C. S.
,
Ma
,
Z.
,
Neises
,
T. W.
, and
Wagner
,
M. J.
,
2013
, “
Thermodynamic Study of Advanced Supercritical Carbon Dioxide Power Cycles for Concentrating Solar Power Systems
,”
ASME J. Sol. Energy Eng.
,
135
(
4
), p.
041007
.10.1115/1.4024030
9.
Utamura
,
M.
,
2010
, “
Thermodynamic Analysis of Part-Flow Cycle Supercritical CO2 Gas Turbines
,”
ASME J. Eng. Gas Turbines Power
,
132
(
11
), p.
111701
.10.1115/1.4001052
10.
Bryant
,
J. C.
,
Saari
,
H.
, and
Zanganeh
,
K.
,
2011
, “
An Analysis and Comparison of the Simple and Recompression Supercritical CO2 Cycles
,”
Supercritical CO2 Power Cycle Symposium
, Boulder, CO, May 24–25.
11.
Neises
,
T.
, and
Turchi
,
C.
,
2013
, “
A Comparison of Supercritical Carbon Dioxide Power Cycle Configurations With an Emphasis on CSP Applications
,”
Energy Procedia
,
49
, pp.
1187
1196
.10.1016/j.egypro.2014.03.128
12.
Nellis
,
G.
, and
Klein
,
S.
,
2012
,
Heat Transfer
,
Cambridge University Press, New York
.
13.
Rowan
,
T.
,
1990
, “
Functional Stability Analysis of Numerical Algorithms
,” Ph.D. thesis, University of Texas-Austin, Austin, TX.
14.
Browne
,
S.
,
Dongarra
,
J.
,
Grosse
,
E.
, and
Rowan
,
T.
,
1995
, “
The Netlib Mathematical Software Repository
,” D-Lib Magazine, http://www.dlib.org/dlib/september95/netlib/09browne.html
15.
Northland Numerics,
2013
, “
Fluid Property Interpolation Tables (FIT)
,” http://www.northlandnumerics.com
16.
Span
,
R.
, and
Wagner
,
W.
,
1996
, “
A New Equation of State for Carbon Dioxide Covering the Fluid Region from the Triple-Point Temperature to 1100 K at Pressures Up to 800 MPa
,”
J. Phys. Chem. Ref. Data
,
25
(
6
), pp.
1509
1596
.10.1063/1.555991
17.
Lemmon
,
E. W.
,
Huber
,
M. L.
, and
McLinden
,
M. O.
,
2013
, “
NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-REFPROP
,” http://www.nist.gov/srd/nist23.cfm
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