GE has taken the wraps off an 8.6 MW, J920 FleXtra natural gas engine for North American utilities. The company boasts that the 20-cylinder engine can provide an electrical efficiency of 49%, and because it can speed up and down easily, it will help integrate renewable power onto the grid. GE Power & Water’s Distributed Power business adds that the unit takes only five minute to start-up and it scales for any plant size.
The J920 FleXtra uses a three module concept. From l to r, the 60 Hz, 8.6-MW generator, the 20 cylinder engine (under the green covers), and the two stage turbocharger at the end.
“The Jenbacher J920 FleXtra gas engines offer best-in-class electrical efficiency for 60 Hz,” says Lorraine Bolsinger, president and CEO for GE’s Distributed Power. “That adds up to big savings in fuel over the life cycle of any plant. For example, over 15 years, a conventional U.S. facility could realize fuel savings of as much as $15 million for a 100-MW J920 FleXtra power plant with high simple-cycle efficiency and great flexibility,”
Globally, the installed capacity of non-dispatchable resources such as wind and solar has doubled since 2010 and is expected to increase further in the coming decade. “While wind and solar have clear environmental benefits, they must be supported by complementary generation to maintain a stable grid,” added Bolsinger. “Flexible resources such as the J920 FleXtra can be activated during periods of low renewable power supply or during tariff spikes. Conversely, the J920 can be quickly curtailed during spells of high feed in of renewable energy or low energy prices.”
The plant concept shows several J920s. The units can scale for most any plant size.
Due to the high levels of volatility in modern dispatch profiles, gas engines face additional challenges in regards to transient performance and grid code compliance. Peak demand and ancillary services require power plants with fast-load tracking capabilities without trade-offs in plant efficiency or start-up reliability.
Greater flexibility comes from a 5 min start up and when the engine provides supplemental or spinning reserve, that is, running the engine at part load so that the unused load is the reserve quickly available. “When running at 80%, the spinning reserve is 20%,” says GE engineer Klaus Payrhuber. “In a large coal-fired power plant or a combined-cycle plant, the only reserves are turbines running at partial load. But with the five minutes start-up, even an idle engine kept preheated is quickly brought online.”
One grid requirement is to have 20% reserve available in five minutes, so this engine meets the requirement when either spinning or non-spinning.
Plant managers in Germany inspect a new facility of several J920 FleXtras.
“GE also has heavy-duty gas turbines and aero-derivative gas turbines, which are also flexible because they typically can start in about 10 minutes,” says Payrhuber. “The aero-derivative gas turbine is aimed at outputs about 100 MW. The difference between the gas engine and the turbine is electrical efficiency. The aero-derivative engine has an electrical efficiency of about 40 to 41%, while the J920 with a 60Hz generator can go as high as 49%. What’s more, several J920s can provide the same output power as the aero-derivative engine and provide better load following because we can shut down engines when not needed and bring them up, as many as needed, and then run the engines for base load with high electrical efficiency.
The gas engine provides a capacity of 8.6 MW in the 60-Hz segment, with total efficiency of more than 90% for combined heat and power applications. This is possible with features such as two-stage turbocharging. This lets the J920 attain up to 2% better electrical efficiency when compared to gas engines that only offer single-stage turbocharging, and it offers faster response to peaks in demand with excellent load-following capabilities, says GE.
The company also announced a memorandum of understanding with independent power producer Sky Global Partners of Houston, to support the development of the first North American power project featuring GE’s Jenbacher J920 FleXtra gas engine technology. Under the preliminary power purchase agreement, GE will supply Sky Global with six of these engines in 2015. WPE
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