A project in China is set to be the first commercial application of Ansaldo Energia’s new GT36 H-class gas turbine.
Under the terms of the €60 million contract signed in November, Ansaldo is to supply this first GT36 for the Minhang combined cycle power plant in China on behalf of Shanghai Electric Power Co., Ltd. (SEP). Controlled by the State Power Investment Company (SPIC), SPIC is one of the largest power companies in China and SEP is a major utility operating in the megacity. The contract for the Minhang Power Plant project represents a key milestone in the market introduction of the H-class GT36 in combined cycle plants.
Boasting high power output and efficiency together with flexibility, GT36 technology originated within Alstom. As part of Alstom’s acquisition by General Electric, which was completed in November 2015, European and US competition authorities mandated that GE divest some of Alstom’s power technology and assets. In particular, the European Commission approved the acquisition conditional upon the divestiture of the most technologically advanced parts of Alstom’s heavy-duty gas turbine business, as well as key personnel for its further development.
Dr. Thorsten Osterhage, New Unit Product Manager for the GT36 at Ansaldo and based at Ansaldo Energia Switzerland, explained: “Based on this decision, GE had to divest the GT26 technology and new GT36 technology which was developed with Alstom.”
In late 2015 it was announced that Ansaldo Energia was to acquire intellectual property rights for the latest ratings of the GT26 and GT36 turbines, existing upgrades and pipeline technology for future upgrades. In addition, the deal included servicing agreements for 34 GT26 turbines already sold in recent years by Alstom. Furthermore, the related subsidiary company Power System Manufacturing (PSM) was included in the transaction. PSM is based in Florida and is mainly focused on other OEM aftermarket service businesses as an F-class turbine technology provider.
More than 400 Alstom employees based in Baden and Birr, Switzerland, are continuing to develop the Alstom heavy-duty gas turbine technology and support the service and turbines business under the Ansaldo banner.
This transaction was concluded in February 2016, extending Ansaldo Energia’s footprint in Europe, the Middle East and the United States and broadening its portfolio of products and services in the gas turbine sector.
“This agreement lays the foundations for Ansaldo Energia to enhance a sustainable growth in power generation industry by extending technological capability and product portfolio in the advanced heavyduty gas turbine business,” said Giuseppe Zampini, CEO of Ansaldo Energia when commenting on the deal.
However, with all Alstom manufacturing capabilities set to remain as GE assets under the deal, following on from the acquisition Ansaldo Energia ramped up production capability at its Cornigliano production facility in Genoa. A €65 million investment in a new factory and upgrading existing facilities means final assembly work is now performed on the so-called maxi gas turbines in Italy.
Dr. Osterhage said: “All the production for the GT26 and GT36 turbines had to be established in Italy during this transition time of three years. This is ending next year and meanwhile we have managed to ramp up production facilities.” For example, the rotor welding capability had to be expanded to manage welding for the much bigger H-class machines.
In addition, new quayside assembly facilities were needed for the bigger GT36 machine. The fully assembled turbine weighs in at some 525-tonnes in all. “What we have also done is a new assembly area in the harbour in Genoa where we can transport parts separately from the factory. Beforehand we had to transport the full gas turbines a few kilometres from the factory,” explained Dr. Osterhage. “Because the GT36 is too large for all for the tunnels and bridges and its weight is too high when it is assembled, this earlier approach wasn’t suitable anymore.”
As a major European port, the assembly facilities at Genoa will allow Ansaldo Energia to ship its machines anywhere in the world. Officially opened in June 2017, in February 2018 the first GT36-S5 50 Hz model produced in Genoa was unveiled. This machine is destined for Minhang.
“We’ve used the time to build up the supply chain and enter manufacturing and we are now producing this gas turbine in Genoa for the first project in China,” noted Dr. Osterhage.
Nicknamed “Mont Blanc”, because it is the top machine in Europe by power, the GT36 turbine generates 538 MW in the 50 Hz version and 760 MW in combined cycle with a claimed peak efficiency of 62.6%. In the 60 Hz configuration the rated output in simple cycle is 369 MW and 520 MW in combined cycle with an exhaust temperature of 630°C, NOx emissions of ≤ 50/30 mg/Nm3 and CO emissions ≤ 10mg/Nm3, according to Ansaldo Energia figures.
GT36 development
Built as an evolution of several generations of proven technology and the GT26, the GT36 gas turbine offers high efficiency at full and part-load, low emissions, a high turn-down capability as part of its mission target to compensate for and support intermittent electricity generation from renewable sources. As Dr. Osterhage noted: “There is an industry trend towards higher efficiency in combination with higher flexibility”.
Both 50 and 60 Hz models of the GT36 feature a 15-stage compressor together with a four-stage air-cooled turbine. “We have 16 combustion cans for the 50 Hz and 12 for the 60 Hz machines,” Osterhage explained, adding, “We have a four-stage air-cooled turbine because it’s very good for robustness and also for flexibility of the engine, you don’t want to have to steam-cool parts anymore. Then we have a welded rotor design which is also very robust.”
As with the F-class GT26, the GT36 also features sequential combustion technology. Robust, flexible and reliable, sequential combustors allow lower NOx emissions over a wider operation range.
“If you go to H-class you want to have higher efficiency so you have to increase the firing temperature. The higher the firing temperatures the more problems you have with emissions. Sequential combustion gives us lower emissions over the whole operation range. NOx at a high load when NOx are dominant but also CO, which is dominant at low-load or part-load. They usually define the minimum environmental load point. For the GT26 and now the GT36, due to sequential combustion we have the broadest load range of emissions compliant operation,” said Osterhage.
He adds that the sequential combustor arrangement also gives high efficiency during part-load operations.
In addition to the 30% load turndown capability the engine also has a parking mode, again emissions compliant, allowing operations to continue at about 10% load.
“Where the second combustor stage is completely switched off this allows emissions compliant operation at about 10% plant load. It’s not a good efficiency but the overall fuel consumption is much lower than operating at 30%. This makes sense for short periods because you can ramp up again to full load in about 10 minutes because the whole engine is hot and the combined cycle system is still hot,” said Osterhage. “You can ramp up without lifetime penalty compared against a full start/stop cycle where you get the counting of a cycling event.”
This offers commercial advantages when even a hot start typically takes at least half an hour. “Here you are at full load in 15 minutes without a cycling event, so for generators which envisage a fluctuating cycling duty this is an ideal machine,” noted Osterhage.
With fast start and rapid ramp rates coupled with high part-load efficiency, turn-down capability and optimized parking load mode the GT36 has been designed to serve the evolving market requirements.
Other key design characteristics are its fuel flexibility and serviceability, for example the welded rotor means no destacking or disk replacement is required, benefiting customers with optimised maintenance costs.
In addition, the GT36 gas turbine can switch between Performance Optimized Mode and XL (eXtended Lifetime) Operation Mode. The first produces maximum performance and output, while the second allows for longer service intervals reducing maintenance costs. Operators can switch between the two modes online during operation. By either optimizing power and efficiency or improving availability and lowering maintenance costs, the choice of mode offers power providers an unmatched opportunity to balance power needs with cost savings.
Dr. Osterhage said: “With 8000 hours [of operation] a year you will have a hot gas path inspection after three to four years, depending on your operation schedule. If you are always running at the highest temperature it will be after three years but you usually don’t do that. In our operation concept, e.g. in partload we avoid a lot of the higher temperatures and then you get the scheduled inspection after 32,000 hours.”
The control system has been developed by Emerson working with Ansaldo Energia and is designed to meet the stringent requirements demanded by advanced gas turbines.
Ansaldo Energia also offers a range of service solutions. Dr. Osterhage explained: “Our service has typical possibilities of remote monitoring 24/7 capability then we can have the operation and control of the units and in terms of service you can choose several models.”
Proving GT36 performance
With the first validation unit under testing since 2016, the GT36 successfully completed the first phase of a comprehensive validation program in May 2017. Located at the Birr Test Power Plant in Switzerland, the 60 Hz unit is a full-scale simple cycle power station and is connected to the Swiss transmission grid. Results reported for the test bed 60 Hz GT36, the S6 version, reveal an efficiency of 42.31% in simple cycle and 369 MW, and yielding some 520 MW at 62.3% net efficiency in combined cycle configuration.
Equipped with more than 3000 measurement points, including a telemetry system which transfers more than 500 measurements from the rotating parts, Ansaldo Energia says the validation tests fully confirmed the high performance and low emissions over the load range, and the resulting wide operational window of this engine. The test programme included stress testing of both stages of the sequential combustion system, part and full load mapping, transient operation and performance testing.
Validation includes design validation with engineering tools, component validation, full engine validation and, finally, field monitoring. The combustion system had already been tested as a single component in a dedicated combustor test rig. The full-sized combustor test rig, located at the German Aerospace Center (DLR) in Cologne, has been testing the combustor system at full mass flow rates since 2013.
“Actually we have two validation units in Birr as we have the GT26 which was kept and the new one for the GT36 which was built in 2015,” Dr. Osterhage said. “We started validation in 2016, exactly at the time of the takeover. The validation units were handed over because Ansaldo Energia is the technology owner and in order to develop these engines further we needed the two validation units.”
With production in Genoa now ramping up, the first commercial GT36 is due for completion and shipping next year with commercial operations at Minhang anticipated in 2020. For this project the steam turbine, the generator and balance of plant are all being supplied by Ansaldo partner Shanghai Electric Group (SEC), which holds a 40% stake in Ansaldo.
As Dr. Osterhage said: “The GT36 is fully in our hands and we are very interested in now executing the first project and of course fitting it for some projects in Europe and also elsewhere in Asia outside China.”
With contracts signed to supply a total of about 30 gas turbines in China, Ansaldo Energia has an Italian order book corresponding to a value of over €400 million. Indeed, Shanghai Electric representative and Ansaldo Energia board member Chen Xuewen has previously emphasised how the partnership between the two companies has given the group access to the Chinese market.
Key to this growth are the primary characteristics of the GT36 that are closely aligned with today’s power market requirements. With more fluctuating, renewable energy connecting to the world’s grids, larger combined cycle plants are needed that are able to offer high efficiency and operational flexibility.
“In combined cycle you have a lot of engines which run between 4000 and 6000 hours per year, they are started quite often and they are following the grid. They are not just running between a standstill and full load they’re running always in a fluctuating mode with varying power,” explained Dr. Osterhage.
He concluded: “This is the user profile which this engine is made for and the expectation is this behaviour or this running profile which we have in Europe already and that we see for the GT26 will get more important for the H-class too, because gas turbines are meeting this fluctuating load schedule.”
By David Appleyard