Renewable Energy and its Innovative Technologies pp 139-153 | Cite as

# Energy and Exergy Analysis of Solid Oxide Fuel Cell Integrated with Gas Turbine Cycle—“A Hybrid Cycle”

## Abstract

The available waste heat at the gas turbine exhaust has enough potential which can be utilized by integration other thermal systems with the gas turbine cycle. Solid oxide fuel cell (SOFC) is one such promising system that can perfectly been integrated with gas turbine power cycles. In this work, a hybrid power cycle has been developed by integrating recuperative gas turbine cycle with the fuel cell, i.e., SOFC. Through successful thermal integration, the thermal efficiency of conventional gas turbine cycle has enhanced by around 70–80%. This can only be achieved by effective utilization of available waste heat at gas turbine exhaust. The performance of hybrid cycle has been examined from the thermodynamic analysis, i.e., energy analysis and exergy analysis. From the detailed parametric analysis, the influence of turbine inlet temperature, air flow rate, compression ratio, etc. are seen. The thermodynamic performance characteristics of a developed hybrid cycle are compared with the available literature, which shows good agreement. The results obtained from energy and exergy analysis are employed to evaluate the thermodynamic losses in each cycle component and to estimate the work potentials of the fluid streams as well as heat interactions. It has been observed that by increasing turbine inlet temperature (TIT), the performance of hybrid cycle can be increased significantly. In addition to this, the exergy destruction within SOFC decreases as air flow rate increases, whereas in combustion chamber the exergy destruction tends to increase.

## Keywords

SOFC-GT Energy Exergy Hybrid cycle## Nomenclature

## .

*A*Active surface area (cm

^{2})*E*Voltage (V)

*E*_{o}Ideal cell voltage at standard conditions (Volts)

*ex*_{chemical}Exergy of fuel (chemical) (kJ/kg)

*ex*_{physical}Exergy of fuel (physical) (kJ/kg)

*ex*Specific exergy (kJ/kg)

*Ex*Exergy destruction rate (kW)

*F*Faraday constant (C)

*h*Enthalpy (kJ/kg)

*j*Current density (A/cm

^{2})*j*_{o}Exchange current density (mA/cm

^{2})*S*_{gen}Entropy generation rate (W/K)

- LHV
Lower heating value (J/mol)

- \(\dot{m}\)
Mass flow rate (kg/s)

*P*Pressure (bar)

- \(\dot{Q}\)
Heat transfer rate (kW)

*R*Universal gas constant (J/mol K)

*T*Temperature (K)

- TIT
Turbine inlet temperature (K)

*U*_{F}Fuel utilization ratio

*W*_{cell}Power output of cell (W)

- \(\dot{W}\)
Power (kW)

## Greek Letter

*η*Efficiency

*ε*Effectiveness

## Subscripts

*c*Compressor

- dest
Destruction

- f
Fuel

- gen
Generator

- cell, fc
Fuel cell

- rc
Recuperator

- GT
Gas turbine

- PT
Power turbine

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