Consulting-Specifying Engineer - December 2008 - (Page A6)

Engine Efﬁciency on A “Mature Technology” Gets a Shot of Innovation Devine, Gas Products Marketing Manager from Caterpillar explains that with larger engines, controls, emissions and fuel efﬁciency all tend to improve. He says, “The challenge with smaller engines is that control technology costs about the same whether it is a large or a small engine.” According to Palmer at Waukesha, the relative thermodynamic advantages of larger engines with slower speeds are decreasing. He stresses, “It is more important to select an engine that is right-sized for the application. Large engines incorrectly applied have disadvantages both technical and commercial.” His point is that most engines are at peak efﬁciency at the upper end of their operating range. Joe Lange from Waukesha was recently a presenter at a Technology and Market Assessment Forum sponsored by the Energy Solutions Center. He described Waukesha’s APG 1000 Enginator™ genset. The APG1000 was developed in cooperation with the U.S. Department of Energy (DOE) as part of DOE’s Advanced Reciprocating Engine Systems (ARES) program. The ARES program was created to accelerate the development of large natural gas engines that operate with increased efﬁciency while meeting tight emissions requirements, maintaining current levels of reliability and durability, and reducing ownership costs. Cummins also manufactures enginegenerator sets for industrial and commercial applications. According to John Shields, Contracts Manager for Power Generation, Cummins has speciﬁcally targeted the engines sized 1 MW and larger for product improvements, which include increased efﬁciency. Engine generator sets, like this Cummins unit, are designed for continuous duty, and can provide heat for a wide range of heating or even absorption cooling applications. NATURAL GAS-FIRED RECIPROCATING ENGINES have been around for over a century. But that doesn’t mean they aren’t being improved. Manufacturers of stationary engine generator sets today offer new products that have improved in efﬁciency, reliability and in extension of their service cycles. Improvements from Multiple Sources According to Lynn Palmer, Vice President – Engineering for Dresser Waukesha, efﬁciency improvements in Waukesha engines are due to several technological advances. Palmer says, “These include combustion system reﬁnements, advanced air handling with improved turbocharger efﬁciency, advanced digital controls, incorporation of Miller Cycle technology, and structural designs that are better able to withstand higher ﬁring loads.” The key concept of the Miller Cycle is to delay closing intake valves until partway through the compression stroke. This reduces internal engine energy use and is offset by a positive displacement supercharger or turbocharger system that inserts a larger mixed charge. Even the Experts are Surprised A 2006 paper presented at a European technical conference by Jacob Klimstra and Christer Hattar, engineers with Wartsila, documents these recent developments. They note that as recently as 1985, most textbooks referenced maximum shaft efﬁciencies of 35%. One of the authors admitted that as recently as 1990 he had forecast maximum achievable shaft efﬁciencies of 40%. Yet, he said, larger engine designs now produce maximum efﬁciencies approaching 47% with efﬁciencies as high as 49% in the future. Size Matters, But So Does Selection In general, larger engines with lower operating speeds offer higher efﬁciencies. Mike Controls an Important Factor Shields points out, “The trade-offs between efﬁciency, low emissions, and system stability A6 gastechnology / WINTER 08 WWW.ENERGYSOLUTIONSCENTER.ORG http://WWW.ENERGYSOLUTIONSCENTER.ORG

Table of Contents Feed for the Digital Edition of Consulting-Specifying Engineer - December 2008

Consulting-Specifying Engineer - December 2008 Contents Viewpoint News M/E Roundtable ARC Awards New Construction Gold New Construction Silver New Construction Bronze Renovation Gold Renovation Silver A Green Approach to Air Conditioning Systems Turning Down the Lights Case Study New Products Equipment Lifecycles Advertiser Index Green Space Gas Technology Pure Power Supplement

Consulting-Specifying Engineer - December 2008

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