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ABSTRACT
The performance of an intermediate-temperature proton-conducting solid oxide fuel cell (pSOFC) hybrid system is investigated in this work. The hybrid system consists of a 20-kW pSOFC, a micro gas turbine (MGT), and heat exchangers. Heat exchangers are used to recover waste heat from pSOFC and MGT. The performance of the system is analyzed by using Matlab/Simulink/Thermolib. Flow rates of air and hydrogen are controlled by assigning different stoichiometric ratio (St). St considered in this study is between 2 and 3.5 for air, and between 1.25 and 1.45 for hydrogen. Results show that the combined heat and power (CHP) efficiency increases as the fuel St decreases or air St increases. This is because lowering fuel St means fewer fuel will be wasted from the fuel cell stack, so the CHP efficiency increases. On the other hand, as air St increases, the amount of recovered waste heat increases, so does the CHP efficiency.
Acknowledgment
This work is partially supported by the Ministry of Science and Technology of Taiwan under grants MOST 104-3113-F-008-001, MOST 104-3113-E-008-003, and NSC 102-2923-E-008-002-MY3.
Nomenclature
Roman letters
| D | = | Diffusion coefficient |
| E | = | Energy |
| F | = | Faraday constant |
| g | = | Gibbs free energy |
| h | = | Enthalpy |
| j | = | Current density |
| LHV | = | Lower heating value |
| N | = | Number of moles |
| n | = | number of moles of electrons transferred |
| p | = | Pressure |
| Q | = | Heat |
| R | = | Gas constant |
| s | = | Entropy |
| St | = | Stoichiometric ratio |
| T | = | Temperature |
| V | = | Voltage |
Greek letters
| = | Charge transfer coefficient | |
| = | Thickness | |
| = | Efficiency | |
| = | Conductivity | |
| = | Gradient |
Superscript and subscripts
| a | = | Anode |
| AC | = | Alternating current |
| act | = | Activity loss |
| c | = | Cathode |
| CHP | = | Combined heat and power |
| cell | = | Fuel cell |
| conc | = | Concentration loss |
| DC | = | Direct current |
| eff | = | Effective |
| MGT | = | Micro gas turbine |
| ohm | = | Ohmic loss |
| r | = | Reversible reaction |
| rec | = | Recover |
| 0 | = | Reference Status |
| = | Catalyst layer |
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