Evaluation of Modular Solid Oxide Fuel Cell Systems for Providing Resiliency to Data Centers and Other Critical Power Users
Authors: Colella Whitney 
Published: July 2021

Aris Energy Solutions, LLC and its project partners, Gaia Energy Research Institute (Gaia), the National Energy Technology Laboratory, the University of West Virginia, Velocity Data Centers, and the National Aeronautics and Space Administration are installing and testing next-generation, modular SOFC systems at data centers, and Gaia is spearheading the effort to independently analyze the engineering and economic performance of these systems, benchmarked against DOE’s performance and price compression goals. This work develops thermodynamic and techno-economic analyses (TEA) for these modular SOFC systems and initially focuses on identifying cost drivers critical to their R&D and commercialization path.

Approach:

Gaia completes a TEA based on experimentally-measured test data from the installed SOFC systems. Gaia collaborates with the project Team to identify and analyze 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, design for manufacture and assembly (DFMA) models of the modular SOFC systems. This TEA includes detailed cell and stack costs, costs of balance of plant (BOP) components, capital costs, operating and maintenance costs (fixed and variable), and sensitivity analyses. Modelling results initially focus on identifying primary cost drivers.

Results:

Modelling results indicate that the primary cost drivers for the lifecycle costs of these modular SOFC systems include, but are not limited to,

(1) the system’s ramp rate (i.e. the system’s ability to change its electric power output up and down per unit time);

(2) the in-use, experimentally-measured electrical efficiencies of the stack, BOP subsystem components, and overall system;

(3) the system’s availability (i.e. the percentage of time that the system is up and running)

(4) the power density of the stack;

(5) the capital costs of the stack;

(6) the capital costs of the surrounding BOP subsystems;

(7) the quantity of effective, in-use heat recovery when operated in combined heat and power (CHP) mode.

Regarding (1), when connected to data centers and to the electricity grid, these SOFC systems need to have the ability to rapidly increase or decrease their electrical power output. The modular SOFC systems tested here have been specifically designed with a high degree of electrical ramping capability over a high turn-down ratio. In a data center, this fast-ramping capability enables the modular SOFC systems to more closely follow the data center’s load, which is the most valuable end-use of the electricity, while limiting electricity exported to the grid, which is typically less lucrative and highly dependent on regional legislation that impacts a distributed generator’s access to sell back electricity to the grid and the ‘sell back price.’

Regarding (2), historically, the actual, measured in-use electrical efficiencies of stationary fuel cell systems installed in the field have strayed substantially from manufacturer specifications. The extent of this discrepancy has varied substantially, depending on the specific manufacturer, the cell technology, operating conditions, the usage profile, the age of the system, and other factors. Yet, the lifecycle costs are heavily influenced by this actual, measured in-use electrical efficiency; this variable encapsulates the quantity of natural gas/ energy consumed vs. the quantity of electricity produced. The value proposition of these systems is heavily determined by this efficiency, combined with the spark spread, or the difference between the natural gas purchase price and the price / value of the otherwise displaced electricity.

Regarding (3), electricity at data centers and other critical power users demands a financial premium, in part due to an expectation of increased uptime (or reduced downtime) of the electricity supplied. To warrant this financial premium, the SOFC systems must demonstrate a high availability, defined as the percentage of time that the system is able to remain up and running at or above its baseline engineering performance standards (including, for example, its electrical efficiency, its electrical power output, etc.)

Regarding (4), (5), and (6), primary cost drivers for the modular SOFC systems also include stack capital costs, stack power density, and system BOP costs. Over time, stack capital costs are estimated to decline more rapidly with more high-volume manufacture, compared with BOP capital costs, because the BOP already incorporates many mass-produced components.

Regarding (7), these modular SOFC systems are also unique in that they can supply their waste heat at high enough temperatures to be useful for space and hot water heating in most U.S. and European buildings. Unlike other modular fuel cell predecessors, these SOFC systems can integrate well with the existing heating systems of most buildings, based on their heat supply temperatures and the heat demand temperatures prevalent in most building types.

Figure 1