Proton-conducting Ceramic Fuel Cells for Co-Producing Electricity and Fuel – A Design for Manufacture and Assembly (DFMA) Analysis

Abstract

This work develops preliminary design for manufacture and assembly (DFMA) models of a novel, proton-conducting, anode-supported ceramic electrochemical cell for co-producing electricity and fuels simultaneously. These DFMA models can then be used to estimated future, expected costs incorporating the novel cell design under various manufacturing production scenarios. The cell electrochemically coverts oxygen (O2) in air and methane (CH4) fuel (the primary constituent of natural gas) into electricity, water, and higher-order hydrocarbons, such as ethane (C2H6). To do this, the cell integrates a methane coupling catalyst into the anode and thereby co-produces ethane (C2H6) and hydrogen (H2) at the anode. The ethane can then be converted into other fuels. The cell is part of a joint R&D effort by Argonne National Laboratory (ANL) and the Illinois Institute of Technology (IIT). The cell’s current technology readiness level (TRL) is about a one (1), i.e. laboratory-scale demonstration of the fundamental concept.Approach:Gaia Energy Research Institute (Gaia) collaborates closely with ANL and IIT to develop the DFMA models for this novel cell design. Gaia works closely with ANL and IIT to identify and analyze key electrochemical cell engineering performance data. Gaia then develops and deploys custom DFMA computer models and data sets. DFMA models center around the electrolyte-electrode assembly (EEA), or the ‘heart’ of the electrochemical cell, where the anode and cathode half-reactions occur. Gaia first develops a specific physical embodiment of the novel cell, then the cell’s bill of materials (BOM), and finally cost estimates for the electrochemical cell, fuel cell stack, and full-scale stationary fuel cell system. Gaia follows this methodology:1. Develop a specific design that physically embodies the EEA concept;2. Develop the EEA’s BOM to specify quantities of components and materials used;3. Identify, for all key materials, price quotes from one or more manufacturers;4. Calculate the minimum costs for the EEA based on materials costs alone;5. Ascertain the EEA’s primary cost drivers;6. Quantify the uninstalled capital costs for a full-size fuel cell stack and stationary fuel cell system incorporating the novel cell design.With the exception of the EEA, other parts of the fuel cell, stack, and system were assumed to be somewhat similar in design to more traditional stationary solid oxide fuel cell (SOFC) systems. Capital costs for the novel stack design were scaled linearly with stack power density. This work estimates stack and system costs for a 100 kWe net electric stack mass-produced at a rate of 50,000 systems per year.Results:Model results indicate that the fuel cell stack subsystem will cost about $478/kW and the entire fuel cell system will cost about $597/kW, including all BOP components. These stack costs are roughly 74% higher than a ‘plain vanilla’ SOFC subsystem, analyzed by the author for DOE in a prior analysis. These system costs are roughly 48% higher than the same ‘plain vanilla’ SOFC system previously analyzed. At the same time, these cost estimates are well below the DOE ARPA-E program goal of < $2,000/kW.Gaia observed an order of magnitude difference in price quotes for several of the specialty ceramic materials investigated. Price quotes from Praxair Specialty Ceramics were approximately double those of Trans-Tech Inc. The reasons cited for the extreme price differential were different manufacturing methods, specifically a chemical co-processing approach for Praxair and a solid-state material manufacturing process (SSMP) for Trans-Tech Inc. The pros and cons of each manufacturing approach are discussed in greater detail in this talk. This analysis assumes that SSMP is used with no degradation in cell performance and bases subsequent cost estimates solely on prices from Trans-Tech Inc., and not Praxair, at ANL’s request.The primary cost driver for the EEA appears to be the BZY-NiO anode substrate. The BZY and NiO anode substrate material is estimated to cost either 2.88 cents/cm2 [based on price quotes for BZY from TransTech Inc.] or 16.40 cents/cm2 [based on price quotes from Praxair Specialty Ceramics]. If the lower BZY cost estimate is taken based on price quotes from Trans-Tech Inc., 52% of the cost derives from the BZY. If the higher BZY cost estimate is taken based on price quotes from Praxair Specialty Ceramics Inc., 92% of the cost derives from the BZY. The secondary cost driver for the EEA appears to be the anode catalyst. The catalyst material is estimated to cost 2.45 cents/cm2. 94% of its cost is due to the material cost of the platinum. The EEA is estimated to cost 5.56 cents/cm2 or $278/kW of gross electric power from the cell or stack.