Comprehensive Evaluation of Manufacturing Costs and Environmental Impacts for Solid Oxide Electrolyzer Cell Systems
Authors: Yamate Shun , Oishi Junya , Kayamori Taro , Otomo Junichiro 
Published: December 2020

Fuel cells are attracting attention as a new energy device for the eco-friendly society. Solid oxide fuel cells (SOFCs) have high power generation efficiency and are developed for various fields (e.g. residential, commercial, distributed generation etc.). Recently, SOFCs are considered not only for power generation but also for electrolyzer cell (SOEC) systems. From the viewpoints of further development of fuel cells, a sustainable development is important perspective as well as their widespread use. Because SOFCs (or SOECs) must not only meet the required performance but also be viable in terms of cost and environment, we have conducted the cost evaluation for SOFCs [1, 2]. In this study, the comprehensive evaluation of SOECs was carried out with the method.

An evaluation target is SOEC modules with various designs (i.e., planar type, flat-tubular type, tubular type, and metal-supported planar type). The manufacturing cost structure of these modules was estimated and compared with each other. In addition, hydrogen production cost by each module was calculated, and then the potential of the widespread use of SOFCs and SOECs was also discussed.

The framework of this work is shown in Fig. 1. The feature of our method is that the database for each production process is built in. To change and/or add cell design and production process, this method provides flexibility and versatility. The result of the comprehensive evaluation for costs and environmental impacts was visualized by a cost structure (i.e., raw material, equipment, utility, labor, building etc.).

In this method, the following steps were taken for each SOEC cell design. Firstly, the required specifications of the system were decided. The performance of SOEC and the required specifications for the cell were determined. Based on the results, the annual production of the module and components were determined. Secondly, for the production of SOEC modules with various designs, each production processes were designed by mass and energy balances. The facility cost and the footprint were also calculated. Finally, the manufacturing cost was calculated as the sum of fixed costs (construction cost, equipment cost) and variable costs (raw material cost, utility cost, labor cost). As the assessment of environmental impacts, CO2, NOx, SOx emitted during manufacturing, and materials, and industrial wastewater estimated from the production yield were evaluated.

The evaluation of module manufacturing costs is described below. Under the conditions of annual production of 1000 units and the rated AC output power of 220 kW, the module manufacturing costs were calculated. Production costs for planar type, flat-tubular type, tubular type, and metal-supported planar type were 48.3, 51.8, 99.7, 38.8 JPY/W, respectively. It was found that the production cost of the metal-supported planar type was the lowest value due to the advantage of raw material costs. Thus, the comprehensive evaluation of SOECs is enabled with the method. Based on those results, we will discuss hydrogen production cost by SOECs as well as the environmental impacts via a module manufacturing.

[1] J. Otomo, J. Oishi, T. Mitsumori, H. Iwasaki and K. Yamada, “Evaluation of Cost Reduction Potential for 1kW Class SOFC stack production: Implications for SOFC Technology Scenario” Int. J. Hydrogen Energy, 38 (33), 14337-14347, 2013.

[2] J. Otomo, J. Oishi, K. Miyazaki, S. Okamura and K. Yamada, “Coupled Analysis of Performance and Costs of Segmented-In-Series Tubular Solid Oxide Fuel Cell for Combined Cycle System” Int. J. Hydrogen Energy, 42 (30), 19190-19203, 2017.

Figure 1