Life Cycle and Techno-Economic Analysis of State-of-the-Art Solid Oxide Electrolyzer Systems

Abstract

Gaia Energy Research Institute (Gaia) presents results for (1) a life cycle analysis (LCA) and (2) a technoeconomic analysis (TEA) of a state-of-the-art solid oxide electrolyzer (SOE). Gaia analyzes a state-of-the-art SOE for making hydrogen, based on an SOE design by Ceramatec Inc. The significance of this work is that it quantifies potential reductions in greenhouse gas emissions (GHGs) and other environmental impacts with the use of SOEs. The significance of this work is that it also quantifies the potential future cost of producing extremely pure hydrogen using SOEs in dollars per kilogram of hydrogen ($/kg H2). 1: Life cycle analysis LCA results indicate that GHGs from the SOE can be at least ten percent (10%) lower than GHGs from steam methane reforming (SMR) of natural gas (the most prevalent technology for making hydrogen). To obtain this result, Gaia builds on the existing DOE models, including, but not limited to, the Argonne National Laboratory full life-cycle model, GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation.) SOE GHG emissions are also evaluated through single-variable sensitivity studies and Tornado charts. Model results indicate that some of the input variables that are most impactful to GHGs include, but are not limited to, (1) the SOE stack and system electricity usages (kWh_electric/kg H2), (2) the SOE stack and system heat usages (kWh_thermal /kg H2), (3) the carbon footprint of the electricity input source to the SOE (kg carbon /kWh_electric), and (4) the carbon footprint of the thermal input source to the SOE (kg carbon /kWh_thermal). Also quantified are potential future changes in GHG emissions that result from further SOE technology advancements. These results are plotted in Waterfall Charts. Consideration also is given to scenarios in which H2 is delivered above ambient pressure, and where the energy input to the SOE includes intermittent renewable energy sources. In addition to GHGs, this analysis also considers life cycle air pollution emissions and solid waste streams. 2: Technoeconomic analysis TEA results indicate that the SOE is estimated to produce hydrogen at less than $2/kg H2, which is the DOE Fuel Cell Technologies Office’s (FCTO) H2 production cost target. To obtain this result, Gaia builds on existing DOE FCTO H2 production analysis modelling tools, including the H2A tools, and the existing FCTO SOE case studies and Excel-based models. Gaia deploys the FCTO's Hydrogen Analysis tools, including the H2A Production and H2A Delivery Scenario Analysis Model (HDSAM) models, to estimate the levelized cost of (1) producing, (2) delivering, (3) compressing, (4) storing and (5) dispensing H2 ($/kg H2). The levelized cost of producing H2 from SOEs is also analyzed using single-variable sensitivity studies and Tornado charts. Model results indicate that some of the input variables that are most impactful to the levelized cost of producing H2 from SOEs include, but are not limited to, (1) the electricity price (¢/kWh_electric), (2) the purchase price for external heat going into the SOE stack (¢/kWh_thermal), (3) the SOE stack and system capital costs ($/kW), (4) the SOE stack and system electricity usages (kWh_electric/kg H2), (5) the SOE stack and system heat usages (kWh_thermal/kg H2), (6) SOE stack and system lifetimes (years), and (7) the operating capacity factor (percent). System costs include both stack and balance of plant (BOP) costs. Also quantified are potential improvements in the levelized H2 production that result from further SOE technology advancements. These results are plotted in Waterfall Charts. Consideration also is given to scenarios in which H2 is delivered above ambient pressure, and where the energy input to the SOE includes intermittent renewable energy sources.