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A transient analysis of a hybrid SOFC-GT system for isolated islands

P. Boutikos, P. Iliadis, K. Atsonios, P. Grammelis Centre for Research and Technology Hellas, Chemical Process Engineering Research Institute

9th Global Conference on Global Warming  Virtual conference

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Population growth Rapid industrial and technological advancement  Improvement of living  standards

Energy consumption   (↑2.9% in 2019) . Greenhouse gas emissions Global warming, climate change Health issues

Carbon-free & environmental friendly economy

Energy  Sources Sustainable,  efficient  and cleaner Intermittent and fluctuate with production not in sync with  demand The lack of access to electricity especially in non-interconnected islands

Electrocatalytic technologies Fuel Cell technology leads to the production of  H 2 .

Clean energy carrier Abundant (water) Fuel in fuel cell & ICE

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High  efficienc y   (up to 70%) Low CO 2   emissions Fuel flexibility :  NG, LNG,  H 2 , biogas Assembly  in existing power plants (1kW – 10 MW) Cogeneration   possibility (domestic hot water, district heating,  desalination,  etc ). Exhaust gas utilization  at a   bottomed thermodynamic cycle (e.g. Rankine, Brayton).

Overall hybrid cycle  efficiency  can be  >70%.

Anode
Cathode
Air (1/2 0,)
Fuel
Water and
Electrolyte

A.G.  Olabi, T. Wilberforce, M.A. Abdelkareem,  Energy 214  (2021) 118955.  F. Calice, M. Dentice d’Accadia, A. Palombo, L. Vanoli, Energy 31 (2006) 3278.

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Αποτέλεσμα εικόνας για coal power plant clipart

Dependence on oil fuel High electricity cost High CO 2  emissions Technical difficulties for RES development

Dependence on NG High efficient electricity production Low CO 2  emissions

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Solid Oxide Fuel Cell  - Gas Turbine Model

Assumptions The reformer and the SOFC are treated as a zero dimensional (0D).  Uniform distribution of gas concentration, temperature and current density in the fuel cell. Only H 2  is electrochemically oxidized. All gases are assumed to be ideal.

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J. Xu and G.F. Froment,    AIChE J. 35  (1989) 88 – 96.  K ang , Y.-W., Li, J., Cao, G.-Y., Tu, H.-Y., Li. J., Yang,  J., J.  Power  Sources 188 (2009),  380 – 392.

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Akkaya, A.V ., J. Energy Research 31 (2007), 79 – 98 .  Zhao, Y., Sadhukhan, J., Lanzini, A., Brandon, N., Shah, N .,  J.  of Power  Sources 196 (2011), 9516  –  9567.

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The design parameters of the reformer and fuel cell were obtained by literature 1,2,3 .   The model was implemented in  Matlab  version 8.2.0 (R2013b).

Operational Parameters Fuel flow  rate  (kmol/h) 7 Air flow rate  (kmol/h) 240 Pressure (bar) 3 Fuel Composition (%) 93% CH 4 , 3% C 2 H 6 ,       1% CO 2 ,  3% N 2 Compressor  efficiency (%) 89 Gas Turbine  efficiency (%) 91 Reformer  temperature ( 0 C ) 650 SOFC temperature ( 0 C) 910 Current density (A/m 2 ) 1.000 – 3.000

Campanari S., Iora P., J. Power Sources 132 (2004), 113 – 126.   Costamagna P., Magistri L., Massardo A.F.,  J.  Power  Sources 96 (2001), 352  –  368.  Georgis D., Jogwar S.S., Almansoori A.S., Daoutidis P., Computers and Chem. Eng. 35 (2011), 1691 – 1704.

Design Parameters m cat  (g) 0.6 ρ cat   (kg/m 3 ) 2335 Cp cat   (J.kg -1 .K -1 ) 444 Bed voidage 0.4 Reactor Volume (m 3 ) 3.10 -3 ρ SOFC   (kg/m 3 ) 4200 Cp SOFC   (J.kg -1 .K -1 ) 640

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Atsonios   et  al.  model 1 This work   Voltage (V) 0.68 0.692 Current density (mA/cm 2 ) 183 170 SOFC Stack power output (MW)  1 1 Fuel Utilization factor (%) 85 63 Anode outlet composition  50.9% H 2 O, 24.9% CO 2  , 11.6% H 2 , 7.4% CO 46.68% H 2 O, 35.43% CO 2  , 9.75% H 2 , 8.04% CO Pre-reformer  outlet temp. (°C) 536 534 Stack exhaust temperature (°C)  838 816

Atsonios, K., Samlis, C., Manou, K., Nikolopoulos, A., Sfetsioris, K., Mitsotakis, A., Grammelis, P.,  J. Hydr. Energy 46 (2021), 4827 .

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Effect of current density (T SOFC  = 910  0 C)

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Effect of Cell temperature (current density = 1700 A/m 2 )

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Effect of molar flow rate ( T SOFC  = 910  0 C, current density = 1700 A/m 2 )

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Operation  load of the hybrid SOFC-GT system in an isolated island during a year and during a whole  day.   The island includes 8.85 MW wind turbines and 5.17 MW photovoltaics.

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A zero-dimensional  model was developed in Matlab in order to investigate the full-load and partial-load operation performance of a hybrid SOFC-GT system.  The  dynamic model predicts very well the numerical results of a literature model under steady-state operation.   The cell voltage decreases with the current density increasing, whereas the power of the system increases until it reaches a maximum and then it starts decreasing.    The system power increases until the cell temperature reaches at 850  o C after which it decreases slowly. The efficiency of the system  presents a similar behavior. The fuel flow rate has a negative effect on the efficiency of the system. The  hybrid system presents medium fluctuations in power demand with the penetration of wind turbines and photovoltaic cells .

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Acknowledgements This work has been carried out in the framework of the Greek-German Research Project “SUstainable and Novel fuel cell applications for Island Energy - SUNIES”.

A transient analysis of a hybrid SOFC-GT system for isolated islands

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