Life cycle analyses of SOFC/gas turbine hybrid power plants accounting for long-term degradation effects

Abstract

In this study, cradle-to-product life cycle analyses were conducted for a variety of natural-gas-based and coal-based SOFC power plant conceptual designs, while also accounting for long-term SOFC degradation. For each type of plant, four base case designs were considered: a standalone SOFC plant, a standalone SOFC plant with a steam cycle, an SOFC/GT hybrid plant, and an SOFC/GT hybrid plant with a steam cycle. The boundary of each base case was subsequently expanded to include either wet cooling or dry cooling options and DC to AC conversion, and was subjected to additional cradle-to-product life cycle analyses. The environmental impact results were computed using ReCiPe 2016 (H) and TRACI 2.1 V1.05 in SimaPro. The main factors affecting the midpoint impacts between cases were the plant efficiency and total SOFC manufacturing required over the plant's lifetime, which were both strongly connected to long-term degradation effects. The findings also showed that the standalone SOFC plant with a steam cycle (which featured higher plant efficiency) had lower midpoint impacts with respect to global warming potential and fossil resource scarcity, which were largely the product of plant operation. The case with the longer SOFC stack lifetime (e.g., a SOFC/GT hybrid power plant with a steam cycle) had lower midpoint impacts with respect to fine particulate matter formation, terrestrial acidification, terrestrial ecotoxicity, and mineral resource scarcity due to the large proportion of midpoint contributed by SOFC manufacturing. Ultimately, the SOFC/GT hybrid plant with a steam cycle was found to be the best option, as it had the lowest ReCiPe endpoint impact (4.5%–42% lower than the other cases)among both the natural gas-based and coal-based cases.