Solid Oxide Fuel Cells Thermo-Chemical Conversion HOME 8 8 Centre for Sustainable Technologies Indian Institute of Science, Bangalore ; http://www.cst.iisc.ernet.in/ Supported by DBT, New Delhi. This is a Beta Version HOME 8

Global greenhouse gas emissions by sector from 1990 to 2010 Thermo-Chemical Conversion Introduction Global greenhouse gas emissions by sector from 1990 to 2010 Reference : www.epa.gov Energy sector responsible for a large chunk of the GHG emissions A renewable energy source and a highly efficient power generation technology is the need of the hour 8 Centre for Sustainable Technologies Indian Institute of Science, Bangalore ; http://www.cst.iisc.ernet.in/ Supported by DBT, New Delhi. This is a Beta Version HOME 8

Thermo-Chemical Conversion Why fuel cells? 8 Centre for Sustainable Technologies Indian Institute of Science, Bangalore ; http://www.cst.iisc.ernet.in/ Supported by DBT, New Delhi. This is a Beta Version HOME 8

Efficiency potential of various power generation technologies Thermo-Chemical Conversion Why fuel cells? Efficiency potential of various power generation technologies Redrawn from: A. Boudghene Stambouli, Fuel cells: The expectations for an environmental-friendly and sustainable source of energy, Renewable and Sustainable Energy Reviews 15 (2011) 4507–4520 8 Centre for Sustainable Technologies Indian Institute of Science, Bangalore ; http://www.cst.iisc.ernet.in/ Supported by DBT, New Delhi. This is a Beta Version HOME 8

Thermo-Chemical Conversion Why fuel cells? Fuel Cell (FC) – An electrochemical device which converts chemical energy to electrical energy utilising a continuous flow of reactants stored outside the device More efficient than the conventional power generation systems High efficiency coupled with low environmental impact Fuel cells - energy efficient – possibility of clean energy and pure water. Pure hydrogen, natural gas are mainly used as fuel now Here, we want to make use of a fuel derived from a renewable energy source in a FC Main types: Polymer Electrolyte Membrane Fuel Cell and Solid Oxide Fuel Cell 8 Centre for Sustainable Technologies Indian Institute of Science, Bangalore ; http://www.cst.iisc.ernet.in/ Supported by DBT, New Delhi. This is a Beta Version HOME 8

Thermo-Chemical Conversion Biomass – FC systems 8 Centre for Sustainable Technologies Indian Institute of Science, Bangalore ; http://www.cst.iisc.ernet.in/ Supported by DBT, New Delhi. This is a Beta Version HOME 8

Thermo-Chemical Conversion Advantages of fuel cells High efficiency Good part load performance Constant efficiency over a wide range of operating conditions compared to other energy conversion systems Low levels of air, noise and thermal pollution Visual aesthetics Safety Easy maintenance and low manpower requirements Material requirements less than in nuclear and MHD systems Multi-fuel ability Siting flexibility – reduces T&D losses, helps in distributed power generation, large water bodies are not required for the powerplant Modularity – makes maintenance and training easier Economic benefits Possible Challenges Cost, technical and infrastructural development 8 Centre for Sustainable Technologies Indian Institute of Science, Bangalore ; http://www.cst.iisc.ernet.in/ Supported by DBT, New Delhi. This is a Beta Version HOME 8

Thermo-Chemical Conversion Working of PEMFC and SOFC SOFC can accommodate different fuels, PEMFC cannot Operation of SOFC Ref: www.montana.edu Fuel flexible, tolerant to impurities compared to the other types and internal reforming may be possible Feasibility of operation at higher temperatures provides the option of using it for CHP Simpler design (solid) The high temperature operation reduces activation losses drastically – larger ohmic region 8 Centre for Sustainable Technologies Indian Institute of Science, Bangalore ; http://www.cst.iisc.ernet.in/ Supported by DBT, New Delhi. This is a Beta Version HOME 8

Thermo-Chemical Conversion Features of SOFC FC can produce power with reduced emissions FC utilizes electrochemical reactions to generate electric power Cathode side: O2 + 4e-→ 2O2- Anode side: 2H2 + 2O2-→ 2H2O + 4e- CO + O2- → CO2+ 2e- CH4 + 4O2- → 2H2O + CO2 + 8e- Higher temperature & Ni catalyst helps in internal reforming Typically used materials for SOFC: Electrolyte: Yttria stabilized zirconia (YSZ): ZrO2/Y2O3 (Yttria replaces Zr4+ with Y3+ creates oxygen vacancies) Anode: Ni/YSZ, Ni/GDC, Cu/YSZ (GDC: Gadolinium Doped Ceria) Cathode: Strontium doped Lanthanum Manganate (La1-xSrx)MnO3, (LSM) Interconnect: Metal / Glasses and glass ceramics Sealants: metal or ceramic as required Two major configurations – planar and tubular (here – planar button cell) Classification based on support – anode, cathode or electrolyte Based on temperature of operation – High, intermediate and low temperature 8 Centre for Sustainable Technologies Indian Institute of Science, Bangalore ; http://www.cst.iisc.ernet.in/ Supported by DBT, New Delhi. This is a Beta Version HOME 8

Thermo-Chemical Conversion Planar and tubular arrangement of FC Comparison of planar and tubular arrangement of FC Planar Tubular Power per unit area Higher Lower Power per unit volume Fabrication method Easier Difficult Ease of sealing Long-term stability Fair Excellent Thermo-cycling stability Good Efficiency Ohmic losses Smaller Larger 8 Centre for Sustainable Technologies Indian Institute of Science, Bangalore ; http://www.cst.iisc.ernet.in/ Supported by DBT, New Delhi. This is a Beta Version HOME 8

Thermo-Chemical Conversion Major processes taking place in FC Unlike in combustion, half reactions are separated, permitting electron flow and work production. The major processes taking place in the fuel cell are: Convective transport of gases in the gas flow channels Diffusive transport of gases through the electrode, reforming reactions at anode Ion formation and electron transport through the external circuit Oxygen ion transport through the electrolyte Combination of the oxygen ion with the ionised fuel molecules at the anode triple phase interface Removal of the products by diffusive and convective transport 8 Centre for Sustainable Technologies Indian Institute of Science, Bangalore ; http://www.cst.iisc.ernet.in/ Supported by DBT, New Delhi. This is a Beta Version HOME 8

Thermo-Chemical Conversion Operation of SOFC with Producer Gas When the operation of an SOFC with producer gas is used, it has been reported that contaminants like tar present in the gas could potentially pose problems. Tar is a mixture of condensable hydrocarbons present in the producer gas. So, the quantitative and qualitative analysis of tar present in the producer gas becomes significant. In this context, the open top downdraft twin air entry reburn gasification technology which has tar levels < 10 ppm becomes suitable for producer gas fuelled SOFC operation. Ref: Monikankana Sharma, Rakesh N, S. Dasappa, Solid oxide fuel cell operating with biomass derived producer gas: Status and challenges, Renewable and Sustainable Energy Reviews 60 (2016) 450 – 463 8 Centre for Sustainable Technologies Indian Institute of Science, Bangalore ; http://www.cst.iisc.ernet.in/ Supported by DBT, New Delhi. This is a Beta Version HOME 8

Thermo-Chemical Conversion Operation of SOFC with Producer Gas Some of the compounds found during GC-MS analysis of PG obtained from an open top downdraft twin air entry reburn gasification system, before cleaning and cooling Ref: D. Prando, S. Shivananda, D. Chiaramonti, M. Baratieri, S. Dasappa, Tar analysis: quantitative and qualitative assessment, SAHYOG report 2014 8 Centre for Sustainable Technologies Indian Institute of Science, Bangalore ; http://www.cst.iisc.ernet.in/ Supported by DBT, New Delhi. This is a Beta Version HOME 8

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