Life Cycle, Thermodynamic, & Techno-Economic Analysis of Next Generation Solid Oxide Electrolyzers

Abstract

A life cycle analysis (LCA) and technoeconomic analysis (TEA) are developed for a next generation solid oxide electrolyzer (SOE) converting water into hydrogen (H2) and oxygen (O2). The LCA quantifies the expected change in environmental impacts with the displacement of current technologies competing with SOEs. The TEA calculates the expected future life cycle cost of producing extremely pure H2 and O2.Approach:To develop these analyses, Gaia collaborates closely with a world-leading developer of SOE technology, OxEon Inc (formerly Ceramatec Inc.). To execute this research, Gaia works closely with the SOE developer to identify and analyze SOE cell, stack, and system engineering performance data. Gaia then develops and deploys custom computer models and data sets that include, but are not limited to, chemical engineering process plant designs of SOEs and detailed LCA and TEA models. Gaia also builds on existing U.S. DOE modelling tools, such as the Argonne National Laboratory full life-cycle model, the Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model; the H2A H2 production analysis model; and existing DOE high temperature electrolysis case studies.1: Life cycle analysis (LCA)Modelling results indicate that the environmental impacts of SOEs can be substantially lower than competing technologies generating H2 and O2. For example, greenhouse gas (GHG) emissions are calculated to be significantly lower for H2 generated via SOEs, compared with H2 generated via steam methane reforming (SMR) of natural gas. (SMR of natural gas produces ~95% of H2 generated in the U.S. today, and is by far the most commercially prevalent process for generating H2.) Modelling results indicate an ~80% or greater decline in GHGs with a switch from natural gas SMR to SOE for H2 production. Results indicate that the primary factors influencing this comparison of GHG emissions from SOE vs. natural gas SMR 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).In addition to GHGs, this analysis also considers life cycle air pollution emissions and solid waste streams.2: Technoeconomic analysis (TEA)Modelling results indicate that the life cycle economics of SOEs can be substantially lower than competing technologies generating H2 and O2. For example, results indicate that, under certain conditions, SOEs can be expected to produce H2 at < $2/kg H2. $2/kg H2 is the DOE Hydrogen and Fuel Cell Technologies Office’s (HFTO) H2 production cost target. Results indicate that the primary cost drivers influencing the levelized cost of H2 from SOEs include, but are not limited to,(1) the sales price attained for the high-purity O2 generated by the SOE system;(2) the efficiency with which the system coverts input electricity into H2 and O2 (i.e. SOE system electricity usage rates, and including stack and balance of plant (BOP) efficiencies);(3) the efficiency with which the system coverts input heat into H2 and O2 (i.e. SOE system heat usage rates, and including stack and BOP efficiencies);(4) the price of the electricity purchased as an input to the SOE;(5) the price of the external heating purchased as an input to the SOE stack;(6) the SOE stack power density;(7) the SOE stack, balance of plant (BOP) and system capital costs;(8) SOE stack and system lifetimes;(9) the operating capacity factor; and(10) operations and maintenance costs.This work also quantifies the impact of R&D improvements to the SOE on reducing levelized costs. This work evaluates both near-term and far-term advanced SOE cases. R&D and higher manufacturing production rates are estimated to reduce the uninstalled SOE system capital costs from about $840/kWe in the near-term to about $640/kW in the far-term. Between near and far-term cases, the efficiency with which the system coverts input electricity into H2 and O2 is estimated to increase from about 37.61 kWh_e/kg H2 in the near-term to 35.1 kWh_e/kg H2 in the far-term. Consequently, the levelized cost of H2 is estimated to be ~$3 /kg H2 in the near-term, based on a 2.5¢/kWh electricity price, and < $2 /kg H2 in the far-term, based on 2¢/kWh electricity.This work was supported in part by the U.S. Department of Energy (DOE) prime contract number DE-EE0007645 via a subcontract.