GE Jenbacher’s latest gas engine

The new J920 – described by GE Jenbacher as its most powerful and most efficient engine so far – is being targeted at CHP applications, independent power production and peak shaving/grid balancing for renewables, writes Tim Probert.

Eighty per cent of the operating costs for gas-fired power plants comprises fuel. With this in mind, GE Jenbacher has launched the J920 gas engine, a 9.5 MW unit with an electrical efficiency of 48.7%, which the Austrian-based firm claims is the most efficient in its class.

The new engine employs a three-module concept, which results in a standardized generator set that consists of the engine itself, a generator and an auxiliary module, all produced at GE’s Jenbacher plant. GE Jenbacher claims the electrical efficiency of the 20-cylinder J920 engine has been raised by 1.5 percentage points on the ‘industry standard’ to 48.7% largely due to the combination of an advanced, electronically controlled combustion system plus a two-stage turbocharging system.

While two-stage turbo-charging is common for diesel engines, this is first application for a large-scale gas engine, says GE Jenbacher. This technology was first used to raise the output of the J624 – previously the largest Jenbacher gas engine – up from 4 MW to 4.4 MW and to increase its electrical efficiency to 46.5% (see box on page 40).


The two-stage system employs intercoolers at every stage of turbocharging, giving a very high efficiency by producing more usable heat and reducing gas exchange losses. By having two turbochargers as opposed to one, there is around a third more boost pressure of fuel to the combustion chamber. This also gives the advantage of increasing the temperature of the air-fuel mixture to around 70°C.

Karl Wetzlmayer, product management leader for GE Jenbacher gas engines, says the J920 has a unique combustion concept, unlike that in all other gas engines in the Jenbacher range. ‘All other gas engines feature a gas mixture and the gas is mixed before entering the turbocharger,’ he said. ‘With the J920 air is first compressed and the natural gas is then injected before the cylinder head. The gas mixture is then fed into the combustion.’

The J920 could be particularly attractive for operation in warmer climates where the high humidity of ambient conditions can result in condensation, says Wetzlmayer. ‘With the J920, the mixture temperature can go up to 70°C as opposed to 40-45°C,’ he said.

‘This is only possible with the higher boost pressure inherent with a two-stage turbocharger, as it allows a greater amount of fuel into the combustion chamber.’

GE Jenbacher admits that the two-stage turbocharger system has a cost impact on the J920, but says the engine concept is designed to be cost-effective. ‘I believe we have the best cost position in the 9-10 MW market with this J920 engine,’ says Wetzlmayer.

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GE Jenbacher’s J920 operates with an electrical efficiency 1.4 percentage points above the ‘industry standard’ and features a distinctive two-stage turbocharger, according to its makers.

The two-stage system should have little impact on maintenance scheduling. ‘The serviceability of this engine compares to others on the market. The J920 is very easy to assemble and disassemble. There is no defined service regime for the J920. It’s variable. We inspect the engine first and then we decide what needs to be changed.’

So why choose a potentially more expensive, two-stage turbocharged engine over a single-stage system? Mainly because of the high electrical efficiency, says the Austrian, who holds a bachelor’s degree in business and engineering from the University of Applied Sciences in Linz.

‘If you are 1.5% or 2% above the average industry standard, it gives the customer a huge benefit. A customer who buys the engine saves roughly €200 000 [$260 000] on fuel costs every year. If you have a CHP application with 90% efficiency, the benefits are even higher. Other manufacturers provide only around 87%, maximum 88%.

‘In Europe, CHP is a very hot topic. For power generation alone, the J920 would be a good solution for peaking power in conjunction with wind power. For developing countries the J920 is being targeted as a solution for independent power projects [IPP] for baseload power generation up to 200 MW, particularly in combined-cycle operation at over 50% efficiency.’


Wetzlmayer says the structure of the J920 is actually designed to go beyond 49% efficiency. The two-stage turbocharger facilitates this, but some components of the combustion system will have to be developed further before this level of efficiency can be reached. Developing the combustion system would be done in-house by Jenbacher engineers, and 49% efficiency should be attainable with ease in due course, he said.

‘The whole concept of the J920 is not to just deliver an engine, but a solution,’ he said. ‘Combined with the modular powerhouse, the J920 offers customers a compact solution.’ The compactness of the J920 is down to the power density of the six-litre, 20-cyclinder engine, which is designed to run at 1000 rpm, compared with similar, slower engines that run at 500-750 rpm.

‘Power density is mainly driven by the speed of the engine. Take a Series 6 engine, a six-litre, 20-cylinder engine operating at around 1500 rpm. Other engine manufacturers may use a nine-litre, 20-cylinder engine running at 1000 rpm. They have the same power output, but the six-litre engine has a much smaller footprint.’


Prady Iyyanki, CEO of GE Jenbacher gas engines, says that he has entered a ‘$1 billion space’ with the J920 engine. Quite what this exactly means is unclear; it could loosely be described as total annual sales for ‘large’ gas engines worldwide, but GE Jenbacher has high hopes for its new engine, particularly in developing countries in urgent need of baseload power.

GE Jenbacher is targeting three main applications for the J920: independent power production; peak shaving/grid balancing for renewables due to its ability to reach full output in only five minutes; and CHP, for which it claims the J920 could achieve efficiency of around 90%.

As ever with gas engine manu-facturers, GE Jenbacher keeps quiet over the cost of the J920, but GE Power and Water CEO Steve Bolze said that GE Jenbacher had invested a large amount in its development. ‘We have invested more than $100 million over the past three to four years,’ he said. ‘That’s not just on the technology, but also on test facilities, getting the supply chain together to build the engines and the support of the launch of those engines.

‘So we have invested more than $100 million on a new, large gas engine with no return on investment for at least five years in testing market conditions and four years later here it is. We see great potential for the J920, particularly for distributed generation in emerging markets like Brazil, India and Indonesia.’

The J920 engine is not replacing an existing engine, added Bolze. Rather, as it is the largest engine in the GE Jenbacher range, it is viewed as an expansionary product. While the J920 is primarily to designed to run on natural gas, like all GE Jenbacher engines, it will be fuel flexible with the ability to run on syngas, flare gas, coal bed methane and so on.

The J920 will be built and shipped from the Jenbach factory, where the 1200 GE Jenbacher employees finish around 1000 gas engine units a year. The J920 could take around 300 to 500 hours to assemble, versus around 200 hours, not including machining hours, for the smaller 4.4 MW two-stage turbocharged engine.

The engine will undergo testing with seven steps – four mechanical and three electrical – before shipping. The J920’s size obliges GE Jenbacher to use a special wide-load truck and to seek local authorities’ permission before transporting it.


A prototype of the J920 has been undergoing successful testing on a purpose-built test bench at GE’s Jenbacher manufacturing facilities in Austria since the late summer of 2010.

A large-scale pilot prog-ramme will put the new engine into operation for the first time at the ‘Stadtwerke’ (municipal utility company) of the town of Rosenheim, Germany, during the first quarter of 2011. Volker Schulte, GE Jenbacher’s general manager for eng-ineering, says he is in the middle of a validation process for the J920.

‘This is one of the most extensive programmes that we have ever done worldwide. It’s a short time cycle for commercialization, but there is a lot of parallel testing being conducted on different levels of test facilities,’ he said

‘The engine that will be installed at Rosenheim in early 2011 is part of that programme. We are working closely with Rosenheim Stadtwerke in order to gain real field experience with the engine and to make sure that it achieves the targets that we have set in terms of performance, durability, lifecycle suitability and costing.’

Following this test phase, set to last all year, serial production is scheduled to begin, and the new engine should be available for use in applications in 50 Hz and 60 Hz countries in 2012.

Source: GE Jenbacher



First two-stage turbocharged gas engine

GE announced that it had achieved a one percentage point improvement to the efficiency of its flagship, 24-cylinder Jenbacher J624 gas engine by the development and application of two-stage turbocharged gas engine technology last summer. The new engine also provides a 10% output increase, compared to the single turbocharged version, and is particularly well-suited for operation in hot environments and CHP applications.

The engine was introduced at a launch event held at GE Jenbacher’s headquarters in Jenbach, Austria, at which representatives from the pilot customer for the first new engine, Red Harvest, a large Dutch greenhouse plant operator, were also present.

Introduced in 2007, the J624 was the world’s first 24-cylinder gas engine for commercial power generation. With the new system, which GE developed with specialists from ABB Turbo Systems, the J624 achieves an increase from 4 MW to 4.4 MW and offers an electrical efficiency of 46.5%, an increase of about one percentage point, although this increases towards a 2.5 percentage point increment when engines operate in hot and humid environments. Improved efficiency is, of course, critical for the competitive cost of electricity and for the reduction of carbon dioxide emissions.

The two-stage turbocharging offers a much higher charging efficiency, which significantly contributes to the engine’s overall increased efficiency. In addition to the higher charging pressure, the technology also improves the power density of the engine, says the company. The new engine will be available to customers worldwide by the summer of 2011.

‘The advanced boost pressure allows us to significantly push the gas engine operating range and maintain full output and efficiency at high ambient temperatures and high elevations,’ said Prady Iyyanki, CEO, gas engines for GE Power & Water at the time.

Prady Iyyanki talked to COSPP after the launch about the very important part of Jenbacher’s business made up of CHP installations. In the developed countries of the EU about 11% of total power used is currently generated from CHP. Yet Denmark has achieved about 60%. The difference defines Jenbacher’s potential market for the continent, he said.

Highlighting some existing areas where Jenbacher engines are installed in numbers, Iyyanki pointed to the vast glasshouses of the Netherlands, where CHP supplies power for lighting, with excess power exported to the grid, along with thermal energy for round-the-clock space heating, and carbon dioxide to stimulate plant growth. In Asia, several textile factories in Pakistan use Jenbacher engines in CHP mode to supply their energy-hungry processes in a country where the local electricity grid cannot always be relied upon and heat requirements are typically very high. Third, steel plants in Spain, South Africa and France burn locally available coke oven gas and blast furnace gas in engines from Jenbacher to make power for use on-site.


Table 1. Key performance data of J920 Source: GE Jenbacher

Performance data

J920 (50 Hz, 1000 rpm)

J920 (60 Hz, 900 rpm)

Electrical output

9500 kW

8550 kW

Electrical efficiency



Heat rate

7392 kJ/kWh

7392 kJ/kWh

Thermal output

8100 kWth

7300 kWth

Total efficiency



Output and efficiency at generator terminals, ISO 3046; natural gas MN>80; power factor 1.0; 500 mg/Nm3 (at 5% O2) NOx; efficiency at LHV

Table 2. The J920’s installed dimensions Source: GE Jenbacher







8.4 metres

2.9 metres

3.3 metres

87 tonnes


5.2 metres

2.5 metres

2.9 metres

54 tonnes

TCA Module

3 metres

6.4 metres

3.4 metres

36 tonnes


Tim Probert is deputy editor of Power Engineering International

This article is based on a report published in the December 2010 issue of Power Engineering International.


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