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Publication Title | Performance Evaluation of Gas Turbine-Fuel Cell Hybrid Micro Generation System

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ABSTRACT

Design-point and part-load characteristics of a gas turbine- solid oxide fuel cell hybrid micro generation system, of which total power output is 30 kW, are investigated for its prospective use in the small distributed energy systems. A cycle analysis of the hybrid system has been performed to obtain general strate- gies of highly efficient operation and control. The method of analy- sis has been compared with previous results, of which power out- put values are set in the range from 287 to 519 kW. Then, the part-load performance of the 30 kW system has been evaluated. Two typical operation modes, i.e., constant and variable rotation speed gas turbine operation are considered. It is found that the variable speed mode is more advantageous to avoid performance degradation under part-load conditions. Operating under this mode, despite of 10 % adiabatic efficiency drop in the gas turbine components, the generation efficiency can be maintained over 60 % (LHV) in the power output range from 50 to 100 %.

Subscripts

cell : SOFC cell

shf : shifting

ca : cathode

net : net value

r : recuperator

t : turbine

gcfc : gas compressor (SOFC) blow : blower

SOFC : solid oxide fuel cell in : inlet

DP : design point

1. INTRODUCTION

ref : reforming or reference an : anode

el : electrode

act : activation polarization c : compressor

DA : inverter

gcgt : gas compressor (μGT) gen : generator

gt : gas turbine

out : outlet

NOMENCLATURE

C : heat-capacity ratio

F : Faraday constant

H : enthalpy flow

K : equilibrium constant

Q : heat flow W T : temperature K

V : voltage V m : mass flow rate kg/s p : pressure atm x : mole fraction

η : efficiency

NTU: number of heat transfer unit

Small distributed generation systems are expected to achieve highly effective energy utilization. Currently, micro gas turbines (μGT) [1] under 100 kW are rapidly spreading in the power gen- eration market. In addition, a concept of much smaller μGT, of which power output is 5 kW, was suggested [2]. Micro gas tur- bines have a perspective to achieve much higher efficiency as 40 % by introducing a higher turbine inlet temperature (TIT) and higher recuperator effectiveness [3]. However, achievement of much higher efficiency than 40 % with traditional μGT is cru- cially difficult, while a μGT combined with a solid oxide fuel cell (SOFC) is expected to attain extremely higher efficiency. It has been indicated that μGT-SOFC hybrid systems offer efficiency over 70 % [4], and it is reported that trial operation of a hybrid system, of which power output is 220 kW, was launched [5, 6]. This study was initiated to establish a strategy to develop much smaller systems to meet increasing energy demands in commer-

Copyright (C) 2002 by ASME

1 Copyright © 2002 by ASME

G : Gibbs energy

J : current density N : rotation speed

R : gas constant

U : utilization factor W : power

n : mole number

u : tip speed

δ : thickness

ρ : resistivity

J/kg

A/ m2 1/s J/mol K

W mol m/s m Ω m

C/mol W

Shinji Kimijima and Nobuhide Kasagi

The University of Tokyo

Department of Mechanical Engineering Hongo 7-3-1, Bunkyo-ku, Tokyo, 113-8656, Japan

1

Proceedings of ASME Turbo Expo 2002

June 3-6, 2002, Amsterdam, The Netherlands

ASME TURBO EXPO 2002 June 3-6, 2002, Amsterdam, The Netherlands

GT-2002-30111

PERFORMANCE EVALUATION OF GAS TURBINE-FUEL CELL HYBRID MICRO GENERATION SYSTEM

Proceedings of

Image | Performance Evaluation of Gas Turbine-Fuel Cell Hybrid Micro Generation System



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