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Reciprocating engines are piston-driven electrical power generation systems ranging from a few kilowatts to more than 5 MW. The program focus is on engines in the 0.5–5 MW range.
Reciprocating engine technology has improved dramatically over the past three decades because of economic and environmental pressures for power density improvements (more output per unit of engine displacement), increased fuel efficiency, and reduced emissions. Computer systems have accelerated advanced engine designs and made more precise control and diagnostic monitoring of the engine process possible. Stationary engine manufacturers and worldwide engine R&D firms continue to drive advanced engine technology and accelerate the diffusion of technology and concepts from the automotive market to the stationary market.
The emissions signature of natural gas SI engines in particular has improved significantly over the past decade through better design and control of the combustion process and through catalytic treatment of exhaust. Advanced lean-burn natural gas engines can produce NOx levels as low as 50 ppmv at 15% oxygen (dry basis).
In September 2001, the U.S. Department of Energy (DOE) announced that six universities had been selected for cost-shared grants covering seven reciprocating engine projects. The projects focus on improving medium-speed (1,200-1,800 revolutions per minute) natural gas engines for distributed energy applications. DOE is investing $3.6 million of the projects' combined value of $4.6 million. University researchers will test engines and produce analytical computer models to upgrade engines, pistons, piston rings, and cylinder liners and to improve ignition systems and reduce friction. Researchers will also seek a more comprehensive understanding of ignition systems, especially at the point of ignition and the beginning of the power cycle.
The goals of the Advanced Reciprocating Engines Project are to increase the energy efficiency of medium-size natural gas engines from 34%-38% to 50%, reduce nitrogen oxides emissions from 1 gram per horsepower-hour to 0.1 gram per horsepower-hour, and reduce operating and maintenance costs by 10%.
For an example of a DOE-supported installation incorporating a reciprocating engine, see the Verizon project profile (PDF 385 KB).
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