Development of a novel hybrid SOFC/GT system and transcritical CO 2 cycle for CCHP purpose in the district scale
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Development of a novel hybrid SOFC/GT system and transcritical CO2 cycle for CCHP purpose in the district scale Hoofar Hemmatabady1 · Mehdi Mehrpooya2,3 · Seyed Ali Mousavi2,3 Received: 6 May 2020 / Accepted: 24 September 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The main target of this work is to optimize a novel hybrid system which includes solid oxide fuel cell, gas turbine, and transcritical CO2 power cycle. The system is driven by the biomass gasification process and is supposed to supply thermal and electrical load of a residential subsector in Tehran (the capital of Iran). Furthermore, in order to maximize the waste heat utilization, a novel adaption of active thermal storage units and cooler of the transcritical cycle is proposed. The Aspen Plus V9 and Aspen HYSYS V9 software are utilized to simulate the proposed hybrid system. Also, the calculations of the loads are implemented by the TRNSYS software. In the final optimum model, about 10% of the total electrical load is generated by transcritical cycle and the rest of 90% is produced by SOFC/GT combination with the optimum ratio of power produced by fuel cell to gas turbine considered to be 50%. The results illustrated that by applying the transcritical CO2 cycle, the exergy and energy efficiency increase up to 4.7% and 1.3%, respectively. Also, the total cost reduces by 2.7%. Moreover, it was found that by using the 27.5% of anode and 50% of cathode of gas recirculation, the efficiency of fuel cell subunit is maximized. Finally, the optimum model is compared to the ones having the same configuration of fuel cell/gas turbine with different downstream models including the heat recovery steam generator unit and steam turbine (with and without transcritical cycle). Keywords SOFC · GT · Biomass gasification · Transcritical cycle · Aspen · TRNSYS · Exergetic efficiency List of symbols A m2 As Active surface area to volume ratio, m−1 Ai Pre-exponential factor, s−1 COP Coefficient of performance Cp Volumetric heat capacity, kJ kg−1 K−1 m−3 E Activation energy, kJ mol−1 Ė Exergy, kW ECOP Exergetic coefficient of performance of absorption chiller Est Sensible thermal energy storage, kJ h−1 F Faraday constant, C mol−1 G Gibbs free energy, kJ mol−1 * Mehdi Mehrpooya [email protected] 1
Darmstadt Graduate School of Excellence Energy Science and Engineering, Technische Universität Darmstadt, Jovanka‑Bontschits‑Straße 2, 64287 Darmstadt, Germany
2
Hydrogen and Fuel Cell Laboratory, Faculty of New Sciences and Technologies, University of Tehran, Tehran, Iran
3
Department of Renewable Energies and Environment, Faculty of New Sciences and Technologies, University of Tehran, Tehran, Iran
H Reaction anthalpy, kJ i Current density, A cm-2 I Current, A k Reaction rate constant, kmole kg−1 cat s, kPa K Absorption coefficient, kPa−1 ni Molar flow rate of species i, mol s−1 PDC Fuel cell power output, kW Pi Partial pressure of the components, kPa Q̇ Capacity, kW rs Total heat transfer surface area R Gas constant, 8.31
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