- In the U.S. there are increasing energy demands that require an ever-increasing need for the large-scale use of new energy resources. Specifically, sporadic renewable energy sources are being incorporated into utility energy portfolios. Thus, supporting stationary energy storage technologies are needed to make these renewable sources reliable and feasible for grid-scale use. Large-scale redox flow battery systems (RFB), such as the vanadium redox flow battery system (VRB), are being investigated to determine if they are capable of meeting these energy storage needs. The U.S. Department of Energy (DOE) released 2015 performance cost targets for grid-scale energy and power needs. Cost models are able to accurately estimate component manufacturing costs, production system costs, and cost targets. There is a need for a new bottom-up cost modeling methodology to assess RFB components produced by continuous web production methods in order to investigate the feasibility of meeting cost targets, as well as to understand the cost drivers and trends that are directing RFB component costs.
An existing bottom-up process-based method for discrete part manufacturing is modified for the development of this new methodology. Cost models are created for three VRB stack components: the bipolar plate, felt electrode, and proton exchange membrane. Key information used to create the cost models was obtained from equipment suppliers, experts, and the research literature. This involved researching manufacturing methods and determining details for 25 state-of-the-art production operations for each of these components. Over 50 equipment and raw material suppliers are also investigated to produce this work. Additionally, over 30 budgetary quotes are obtained, along with over 50 equipment and raw material cost values from literature, and 40 supplemental equipment costs posted on company websites. Results from the cost models show U.S. DOE performance cost targets can be met for the components and VRB network investigated. The primary cost drivers are found to be the raw material and utility costs. The most sensitive cost parameters for the bipolar plates, felt electrode, and proton exchange membrane are the raw graphite flake costs, web width, and Nafion® ionomer costs, respectively. Identified cost reduction opportunities include increasing the web widths, selecting alternative raw materials, and increasing the production rate of each manufacturing line. Alternative thermal processing operations and equipment should be investigated, as these accounted for over 30% of capital costs. These results indicate that Nafion® ionomer cost is the primary cost driver for the cell stack components investigated, even when speculative future high volume prices are used. Finally, the cost model results can be used to determine competitive cost strategies for the production of these components.