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Research Papers

Diurnal Temperature and Pressure Effects on Axial Turbomachinery Stability in Solid Oxide Fuel Cell-Gas Turbine Hybrid Systems

[+] Author and Article Information
James D. Maclay, G. Scott Samuelsen

Advanced Power and Energy Program, University of California, Irvine, Irvine, CA 92697

Jacob Brouwer1

Advanced Power and Energy Program, University of California, Irvine, Irvine, CA 92697jb@nfcrc.uci.edu

1

Corresponding author.

J. Fuel Cell Sci. Technol 8(3), 031012 (Mar 01, 2011) (6 pages) doi:10.1115/1.4003163 History: Received September 27, 2010; Revised November 09, 2010; Published March 01, 2011; Online March 01, 2011

Abstract

A dynamic model of a 100 MW solid oxide fuel cell-gas turbine hybrid system has been developed and subjected to perturbations in diurnal ambient temperature and pressure as well as load sheds. The dynamic system responses monitored were the fuel cell electrolyte temperature, gas turbine shaft speed, turbine inlet temperature, and compressor surge. Using a control strategy that primarily focuses on holding fuel cell electrolyte temperature constant and secondarily on maintaining gas turbine shaft speed, safe operation was found to occur for expected ambient pressure variation ranges and for ambient temperature variations up to 28 K when tested nonsimultaneously. When ambient temperature and pressure were varied simultaneously, stable operation was found to occur when the two are in phase but not when the two are out of phase. The latter case leads to shaft overspeed. Compressor surge was found to be more likely when the system is subjected to a load shed initiated at minimum ambient temperature rather than at maximum ambient temperature. Fuel cell electrolyte temperature was found to be well-controlled except in the case of shaft overspeeds. Turbine inlet temperature remained in safe bounds for all cases.

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Figures

Figure 1

SOFC-GT hybrid system utilizing a blower for cathode recirculation

Figure 2

Cascade controller used to control SOFC temperature with a variable speed gas turbine

Figure 3

Compressor response to a diurnal temperature fluctuation of 28 K

Figure 4

Ambient temperature and gas turbine shaft speed versus time for a diurnal temperature fluctuation of 28 K

Figure 5

Ambient temperature, turbine inlet temperature, and fuel cell electrolyte temperature versus time for a diurnal temperature fluctuation of 28 K

Figure 6

Compressor response to a diurnal temperature fluctuation of 32 K

Figure 7

Compressor response to a 25% reduction in fuel cell current demand

Figure 8

Compressor response to a diurnal temperature fluctuation of 28 K and a 25% reduction in fuel cell current demand initiated at minimum ambient temperature

Figure 9

Compressor response to a diurnal temperature fluctuation of 28 K and a 25% reduction in fuel cell current demand initiated at maximum ambient temperature

Figure 10

Compressor response to a diurnal pressure fluctuation of 4 kPa

Figure 11

Ambient pressure and gas turbine shaft speed versus time for a diurnal pressure fluctuation of 4 kPa

Figure 12

Ambient pressure, turbine inlet temperature, and fuel cell electrolyte temperature versus time for a diurnal pressure fluctuation of 4 kPa

Figure 13

Compressor response to a diurnal temperature fluctuation of 28 K and pressure fluctuation of 4 kPa in phase with each other

Figure 14

Ambient temperature, ambient pressure, and gas turbine shaft speed versus time for a diurnal temperature fluctuation of 28 K and pressure fluctuation of 4 kPa in phase with each other

Figure 15

Ambient pressure, turbine inlet temperature, and fuel cell electrolyte temperature versus time for a diurnal temperature fluctuation of 28 K and pressure fluctuation of 4 kPa in phase with each other

Figure 16

Compressor response to a diurnal temperature fluctuation of 28 K and pressure fluctuation of 4 kPa out of phase with each other

Figure 17

Hourly ambient temperature and ambient pressure versus time for September 1, 2005. Source: Argonne National Laboratory.

Figure 18

Hourly ambient temperature and ambient pressure versus time for December 1, 2005. Source: Argonne National Laboratory.

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