An Integrated High Pressure SOFC and Premixed Compression Ignition Engine System

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Project Term:
08/06/2018 - 02/05/2021

Critical Need:

In 2015, two-thirds of U.S. electricity was derived from fossil fuels. This electricity was then distributed through the electrical grid, ultimately netting a delivered efficiency of 34%. Ultra-high electrical efficiency (>70%) distributed generation systems, such as those that combine fuel cells and engines, can lower the cost and environmental burdens of providing this electricity. These hybrid systems convert natural gas or renewable fuels into electricity at substantially higher efficiencies and lower emissions than traditional systems. At the component and system levels, however, these hybrid technologies face challenges including the low-loss integration of fuel cells with engine-based waste recovery cycles, capital cost, and fuel cell stack durability.

Project Innovation + Advantages:

The University of Wisconsin - Madison will develop components for a hybrid distributed energy generation system that couples a pressurized solid oxide fuel cell (SOFC) with a premixed compression ignition (PCI) engine system. In the resulting system, gases that leave the fuel cell, which consumes about 75% of the fuel, are directed into the engine to be ignited by compression of the pistons. To achieve a targeted 70% electric efficiency, the SOFC system must operate near 75% fuel utilization. When operating at this high level of fuel utilization, however, the flame speed of the leftover fuel in the cell’s “tailgas” is too low to be used effectively in a conventional spark-ignited engine. The team will address this challenge by using a novel, PCI engine concept that adds an extra burst of spark-ignited natural gas, improving engine efficiency. The system will be analyzed in conjunction with a next generation, intermediate temperature (600°C to 800°C), metal-supported SOFC, but the final engine system will be designed to be suitable with any pressurized, intermediate temperature SOFC. With this universal capability, the final product will be an engine system that can “plug into” any intermediate temperature SOFC system. The team's design targets larger industrial applications, aiming for systems as large as 1MW.

Potential Impact:

 The INTEGRATE program is developing a new class of distributed and ultra-efficient (>70%) fuel to electric power conversion systems for commercial and industrial customers.


Distributed electrical generation systems can produce highly reliable electric power supplies.


High electric efficiency and decreased reliance on combustion would result in lower greenhouse gas and air pollutant emissions.


These systems’ high efficiency and avoidance of electric grid transmission and distribution costs offer the potential for lower cost electric power.


ARPA-E Program Director:
Dr. David Tew
Project Contact:
Prof. Sage Kokjohn
Press and General Inquiries Email:
Project Contact Email:


Caterpillar, Inc.
United Technologies Research Center

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