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FUTURE COMBINED CYCLE CONFIGURATIONS AND MORE FLEXIBLE TURBINE DESIGNS FEATURED DURING THE CONFERENCE
The Annual PowerGen conference drew a highest ever attendance of over 20,000 attendees to Las Vegas in December—a sign that a market recovery is becoming a reality. Those in attendance were served up 40 sessions, 200 speakers and 12 separate tracks. A seemingly never ending exhibit hall consisted of 1,200 exhibitors from all corners of the globe.
Among the highlights were: a keynote by Mitsubishi Power Systems covering the changing energy mix and the rising importance of combined cycle plants; electric vehicles and how they will influence electricity load; how modern turbines are being modified to deliver more flexible generation; a newly introduced combined cycle configuration; modifications to a Heat Recovery Steam Generator (HRSG) to overcome steam cycle limitations; and aggressive plans to introduce more competition into the spare parts business.
The morning keynote featured David Walsh, Senior Vice President, Service & Manufacturing, at Mitsubishi Power Systems, America. In his analysis of the market, he highlighted the fact that as much as 25% of the U.S. coal-fired fleet is in jeopardy due to environmental regulations. That was good news, he said, for the gas turbine (GT) industry which was destined to expand more than any other sector of the power industry in the coming decade. “With the EPA moving forward steadily, it’s going to mean a lot of gas,” said Walsh.
He noted that surveys of the top five U.S. utilities demonstrated that renewable assets will generate 7% of their total portfolio in ten years compared to 5% today. What is the reason for such a modest jump for renewables in the face of overwhelming regulatory favor?
“Rate payers will force us to find the most cost effective solutions we can,” said Walsh.
He showed himself to be an enthusiastic promoter, not just of his own company, but of the GT in general. He laid out the build out of Mitsubishi manufacturing plants in the USA and pointed out that there are now four OEMs serving the large scale gas turbine market in North America compared to two in the nineties. That showed a healthier side to the industry as companies such as Mitsubishi have come to the USA and set up shop.
Walsh informed the audience that manufacturing of the company’s G class turbine would begin on U.S. soil during the early part of 2012. Eventually, that will be followed by J frame turbine manufacturing in the USA.
Another theme was how far the industry had come in a decade or so. The largest turbine available has shifted from around 100 MW up to over 300 MW. Mitsubishi, for example, offers a 327 MW model. The Mitsubishi M501J operates at 61.5% efficiency and has a turbine inlet temperature of 1,600°C.
According to Walsh, the J-class unit operating at the T-point plant in Japan has already exceeded 3,000 actual operating hours (OH) and 58 starts. The first engine for Kansai Electric has been delivered with commercial operation scheduled in 2013, and 12 orders already in hand for sites in Asia. Meanwhile, the company continues to work on achieving a turbine inlet temperature goal of 1,700°C.
Mitsubishi is involved in several large combined cycle plants which will utilize these massive machines – at a scaleWalsh said is necessary to meet future needs. FPL’s 3600 MW West Country Energy Center, as well as Georgia Power’s 2700 McDonough Plant and 2400 MW Mystic/Fore River Generation Stations were examples he cited as being the wave of the future in terms of GT plant potential. The FPL site is the largest combined cycle power plant in the USA and uses Mitsubishi M501G operating at 58.3% efficiency.
“These super large gas turbine plants are a glimpse into the future,” saidWalsh. “A few years ago, plants of this size were only possible for steam and nuclear applications. Our J-class technology will take this trend in plant size even further.”
He ended by challenging the audience to get the word out on the value of the gas turbine in today’s energy landscape. He felt the industry needed to do a better job of informing the public of the efficiency and emissions record of the GT.
Another theme of the conference was flexible gas-fired generation. Speaker after speaker noted that legislative momentum made abundant wind and solar on the grid inevitable. Siemens Energy pushed the value of having plenty of combined cycle gasfired turbines on the grid to ramp up and down as renewable resources ebbed and flowed during the day. Siemens was one of many vendors at PowerGen touting the rapid ramp up and low emission credentials of their latest turbines. Its Flex Plant 30 design can maintain emissions rates below 5 parts per mission while it is ramping down.
“In most areas, renewables have the right of way onto the grid,” said Bonnie Marini, Director of 60 Hz Product Line Marketing at Siemens. “Our biggest challenge is ramping down other power sources to deal with renewables coming onto grid suddenly.”
While Mitsubishi favors high-temperature technology, Siemens has taken a different approach with its SGT-8000H which brings together the best of Siemens and Westinghouse for the first time in one turbine, said Marini.
“The SGT-8000H is not high temperature and is not single crystal,” said Marini. “It has a couple of rows of directional solidified blades but that’s all.”
The company uses single crystal blades in some 50 Hz machines, but not in 60 Hz. Marini cited cost and repair difficulties as two of the reasons behind this decision on 60 Hz. Another factor, she said, was that Siemens prefers to stick with proven technologies and optimize them. The H-class, for example, has the same firing temp as the G-class but is more efficient. At its Irsching 4 plant in Germany an 8000H in combined cycle mode has been tested at 60.75% efficiency and has achieved 11,000 OH.
“We don’t say that this engine will beat 60% efficiency; it already did it,” said Marini.
While the 8000H is new, the SGT6- 5000F has been the workhorse of the Siemens 60 Hz fleet. The latest version of this engine has what the company is calling shaping power. This brings the capability to add another 20MWon a hot day. The term “shaping” is a marketing term which relates to the shape of a graph showing load patterns — whether a rapid ramp-up curve to accommodate wind and solar coming onto/off the grid, or a relatively flat output dealing with small changes in ambient conditions.
“We have made the front stages of the SGT6-5000F compressor larger to gain more mass flow and hence peaking power,” said Marini. “You can use this extra capacity to load follow renewables.”
So far, the company has sold 50 models with shaping power. Great River Energy’s Elk River 11 plant includes a Siemens SSC6-5000F turbine which takes only 12 minutes to start up. It has been operating since 2009. Other plants under construction using this Siemens GT, said Marini, include the GenOn March Landing plant and the City of El Segundo, which is building a Flex Plant 10 that will be online in 2013.
Other turbine manufacturer and utility presenters drew attention to the fact that renewables had completely changed decades-long power patterns. In the past, baseload power was provided by coal and nuclear resources. With these types of plants under fire or being phased out, renewables were now beginning to be counted on for baseload power. That meant that baseload was no longer flat, as it had been traditionally.
Gas turbines, therefore, are now the medium of choice to pick up the slack in the absence of large-scale affordable energy storage technology.
“Renewables are driving the market for flexible gas-fired generation,” said Steve Rose, Vice President of Conceptual Engineering at U.S. independent power producer NRG Energy. “With 90 GW of non-hydro renewables called for by 2025 in existing state Renewable Portfolio Standards (RPS), it requires 45 GW of gas firming. Most of it will be rapid response combined cycle plants as EPA regulations are moving the market away from simple cycle.”
That poses a problem for coastal sites that have traditionally relied on oncethrough cooling, which has fallen afoul of the EPA via section 316 (b) of the Clean Water Act. Similarly, wet cooling via towers can cause emissions challenges. “An air-cooled CCGT is a good option for coastal sites facing 316 (b) restrictions,” said Rose. “For existing plants, however, redoing the cooling is almost impossible.”
He added that the two best available air-cooled rapid response CCGT products are the Siemens Flex-Plant 10 and NRG’s design based on the latest 10-minute start GE 7FA units.
NRG is erecting two Flex- Plant 10s at a coastal site in El Segundo, California. They consist of a 265MW1x1 rapid start SGT6-5000 F(3) turbine with a single-pressure, unfired HRSG, industrial ST and an air cooled condenser. NRG has developed its own solution for this situation, which it is patenting. Called NRG CC-Fast, it is a 275 MW1x1 rapid start CCPP that will use the GE 7FA.04 at an NRG site in Astoria, New York, along with a single-case condensing STG with a 2-pressure duct-fired HRSG. GEA EGI’s Heller System provides a direct contact spray condenser and air cooled tower.According to Rose, this system is capable of a 10-minute start to 75% load and has minimal water consumption compared to the Siemens approach.
“The steam turbine exhaust is mixed with cooled condensate from the dry tower in a direct contact spray condenser,” said Rose. “The condensate is recirculated through the dry tower where heat is rejected via aluminum fin tube panels.”
This Astoria site has been using multiple, smallWestinghouse units as well as Pratt & Whitney TwinPacs. During the first phase, the older Westinghouse peakers are being removed. The second phase will eliminate the TwinPacs. The result will be replacing 425 MW of simple cycle power with 1.1 GW of CCPP with a much better heat rate and much lower levels of emissions.
Gordon Smith, chief consulting engineer at GE Energy Global Projects Operation, explained the firm’s approach to rapid response plants. Conventional Combined Cycle Power Plants (CCPPs) limit load rates on startup, he said, so it is necessary to break the link between the gas turbine and the steam turbine so that the steam cycle is not restricting gas turbine ramp up. “GE has developed proprietary technology with our combined cycle offerings to overcome these startup limitations. This approach accomplishes the rapid start without needing additional steam venting, thereby keeping water consumption down.”
One key, he added, is a rapid response-qualified drum type Heat Recovery Steam Generator (HRSG) which is supplied by several HRSG suppliers. Before acceptance for rapid response use the vender’s design is extensively reviewed and analyzed by GE for this startup duty.
GE also uses terminal attemperators outside the HRSG to manage steam temperature. Past attempts to use this technology have suffered due to wear and tear since the attemperators protruded into the steam path and this led to excessive maintenance and repair. To get around this, the company selected a design with minimal intrusion into the steam path, resulting in better durability. Extensive control logic protection and additional instrumentation insure water overspray is avoided. GE’s rapid response CCPP includes an integrated controls architecture including streamlined plant startup sequencing and one push button start capability.
One of the benefits of this technology is an improvement in startup emissions. “In a conventional CCPP, the gas turbine has a hold on ramp up at low load,” said Smith. “After an eight-hour shutdown, with the GE rapid response power plant, the start-up time is less than 30 minutes compared to a conventional power plant start-up time of 60 to 70 minutes. GE’s rapid response technology allows the gas turbine to quickly get to a lower emissions operating mode resulting in 85% less startup NOX and at 75% less startup CO,” said Smith.
Carlo Luzzatto, the new president of turbine part and repair vendor Chromalloy, chose PowerGen to announce his arrival at the helm and to brief the press on where the company is heading. Its new Tampa facility, for example, is now accomplishing ceramic core production and casting of turbine blades, and it is adding a Palm Beach Gardens, Florida, engineering center of excellence and headquarters which will be ready in Q1 2012.
Viewing the market, he was confident that a recovery had started, although most of the gains he’s noticed were in Asia. He also commented on the changing operating pattern with gas turbines transitioning from relatively few starts per year to many. They are starting and stopping multiple times and running for only a short time as opposed to all day or all week, he said.
“If you look at Spain, renewables supply most of the baseload power and the GT’s there are running only 15% of the time, down from more than 50%,” said Luzzatto.
Specific to the aftermarket, he said that every aspect of the GT service business amounts to somewhere between $16 and 17 billion per year, approximately. He qualified this by saying that this number may not include upgrades to turbines and replacements of the fleet. So the actual total may be as high as $20 billion annually. This figure includes aeroderivatives but not mechanical drives.
Luzzatto highlighted the fact that spare parts comprise the largest slice of the maintenance pie. For the F-class, for instance, spare parts account for 68%, repairs 18% and field service 14%. Chromalloy conducts repairs and offers parts, but rarely gets involved in field service. It owns a turbine services company in Glasgow, Scotland, which includes field services, but Luzzatto said it is a minor part of the business and he has no plans to grow that.
“Less than 20% of our business currently is industrial, and the rest is aerospace,” said Luzzatto. “But we have been involved in the industrial section for 40 years and plan to be far more present in the energy field.”
On the part repair side, Chromalloy has a history of dealing extensively with Siemens and TurboCare, although Ansaldo and GE have agreements, too. He sees major opportunity in the parts business for Chromalloy.
“If OEMS have bottlenecks in their supply chain we have huge opportunities to sell direct to plants,” said Luzzatto.
He’s talking about the non F-class fleet primarily, as OEMs tend to focus on servicing their latest F-class equipment. OEM’s, too, are protected by long-term agreements. But many owners of F-class turbines have either reached or will soon reach the end of their original service a g r e e m e n t s . Chromalloy’s large new casting foundry in Tampa is going to include F-Class casting, added Luzzatto.
“The biggest part of the annual $16 billion in GT services is the F-class,” he said. “One year’s averagemaintenance is four times more for the F-class than the Eclass. That’s a good opportunity.”
Chromalloy is picking its battles and only going into markets where it feels it can succeed. It has a deal in place with GE, for instance, on aerospace and on the aeroderivative side. In these areas, it sells to the OEM rather than going direct to the user. It also is not going to attempt to reengineer all the parts for every GT, only those that the company feels represent the best business opportunity.
Single crystal blades are an example where Luzzatto said there are only a few casting players competing in the industry. Similarly, when it comes to salvage and recovery of existing parts, he added that there are few outfits attempting this.
But a viable parts alternative hits right at the heart of the OEM bottom line. That’s why it has been observed that some OEMs have been cutting the cost of their parts in an effort to retain the market. Luzzatto accepts this as a necessary part of the business even if it means fewer sales for his company. In the end, it’s the users that benefit.
“It is very difficult to raise prices after you drop them,” said Luzzatto. “But when the market recovers, the OEMs will focus on new turbine sales, not spare parts.”
He endedwith a briefing on howthe shifting operational patterns of GTs impacted part design.When turbines were expected to have only 50 starts per year, parts were designed mainlywith creep inmind.Nowthat the number of starts has shifted to 200 or more per year, these same parts are exposed to farmore thermal stress than designers anticipated. In response, OEMs are reducing maintenance intervals. But that isn’t a popular solution among users.
“We are looking at designing coatings and base materials for that specific multiple-start duty,” said Luzzatto. “This could become a game changer. We are already discussing this opportunity with customers.”