Gas engine sets new benchmarks for efficiency and size

GE's Jenbacher has unveiled a new 20 cylinder 9.5MW gas engine generator set that boasts 48.7% efficiency, a world record as far as we know, with plans to raise this by a further 5% or so in future by incorporating a US technology that has just been purchased

According to Dr Volke Schulte, general manager engineering, the high efficiency arises from using a two stage turbocharger with an intercooler to raise the gas air mixture to a particularly high charge pressure for a gas engine, plus what he described as, "A lot of electronic control optimizing the combustion and ignition." This includes sensing and controlling the ignition timing in each individual cylinder. Despite its size – the con rods need the use of a crane to lift them – the engine is designed to run at 1,000 rpm in 50Hz countries.

Looking to the future, GE has recently acquired the Florida based company, Calnetix Power Solutions, which specializes in converting waste heat to electric power using a closed organic fluid Rankine cycle. This generates power by warming an HFC fluid so that it boils and drives a turbo expander. Karl Wetzlmayer, product line management leader for Jenbacher gas engines told us that the plan is to scale up the Calnetix machine and utilize some of the waste heat from Jenbacher gas engines with a view to increasing the overall efficiency of their generator sets by a further 5%.

We were further told that the prototype J920 engine that we saw is to be supplied to a customer, the Stadtwerke or municipal utility company in Rosenheim, just across the border from the Jenbacher plant in Jenbach, Austria. The Stadtwerke will additionally be recovering waste heat from the engine for a district heating scheme. The J920 will be their fifth Jenbacher engine, and it is expected that they will use the engine to heat water to 100°C and take it back from the heating system at 70°C. Used in such a manner, the overall thermal efficiency of the system is said to be around 90%.

Tom Shelley

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