Case Study: Advanced Diesel Engines

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By Jeffrey Rissman and Hallie Kennan

Modern diesel engines are hugely important to the U.S. economy, especially in the transportation industry, where they are widely used in trucks and other heavy-duty vehicles. Truck transportation, which is dominated by diesel engines, directly employed over 1.3 million people and contributed $252 billion to national GDP in 2010. The widespread adoption of cleaner, more efficient diesel engines, and the associated energy security benefits, was accelerated by tremendous technological advances made through research at national labs and by government-led coalitions.

The diesel engine was invented in the 1890s, but it only began to play a major role in the U.S. economy during and after construction of the Interstate Highway System in the 1950s. Following the 1973 oil embargo, the government placed a new emphasis on technological development to improve fuel efficiency and reduce dependence on foreign oil. Over the following decades, there were three main mechanisms by which the government supported the improvement of diesel engines: performing basic combustion research, creating engine simulation tools, and establishing research partnerships.

Basic Combustion Research: In the 1970s and 1980s, the extent to which engine manufacturers could refine their products was limited by a lack of fundamental knowledge about the combustion process. Basic research is risky and long-term, so it is difficult for private companies to justify to their shareholders. To address this need, the government founded the Combustion Research Facility (CRF), which began operations in 1981, and the Advanced Combustion Engine R&D program (ACE R&D), which started in 1986. These programs brought together researchers from national labs, universities, and the private sector to achieve advances in fundamental understanding of combustion.

Simulation Tools: The CRF and ACE R&D programs also developed computer software capable of simulating the combustion process, such as KIVA codes and the Cross-Cut Lean Exhaust Emissions Reduction Simulation (CLEERS). These tools were used by engine manufacturers such as Caterpillar, Cummins, General Motors, Ford, and Chrysler to develop cleaner and more efficient engines.

Research Partnerships: In addition to the efforts above, the DOE played a critical role in bringing together private companies, government labs and agencies, and academia through partnerships that continued to refine engines through the 1990s and 2000s. These include the Partnership for a New Generation of Vehicles (PNGV) in 1993, the 21st Century Truck Partnership in 2000, the FreedomCAR and Fuel Partnership in 2002, and U.S. Drive in 2011. Additionally, DOE has convened smaller partnerships, such as the Cooperative Research and Development Agreement between Cummins, catalyst maker Johnson Matthey, and Pacific Northwest National Laboratory, to achieve rapid technical progress. These partnerships achieved advances that improved vehicle efficiency, reduced harmful emissions, and reduced dependence on foreign oil.

As a result of government-supported research, heavy-duty diesel trucks went from 37% efficiency in 1981 to 42% efficiency in 2007. Truck fuel economy increased almost 20%, from a low of 5.4 miles per gallon in 1981 to 6.4 miles per gallon in 2010. From 1990 to 2009, per-mile emissions of harmful nitrogen oxides (NOx), carbon monoxide, and particulate matter from the U.S. heavy truck fleet declined 67-81%, dramatically reducing adverse health impacts from diesel engines.

Today, diesel engines use an array of technologies developed through the CRF and ACE R&D programs. Government-led diesel research is ongoing; the ACE R&D program’s 2015 goals include improving overall efficiency of diesel passenger vehicles to 45% and commercial vehicles to 50%.

From 1986 through 2007, the CRF and ACE R&D programs generated over $70 billion in economic benefits to the United States while improving fuel efficiency, reducing emissions, and reducing U.S. reliance on foreign oil. The history of advanced diesel engines shows that government support of energy R&D is not wasteful and can generate a positive return on investment for the country while simultaneously achieving important health, environmental, and national security benefits.

The views expressed in this case are those of the AEIC staff and do not necessarily reflect the views of the AEIC principals.