Flow scaling key tohigher power output page 14

10% more power at high ambient tempspage 20

Flying high with newFT4000 gas turbine page 30

September – October 2014 www.gasturbineworld.com

20 GAS TURBINE WORLD September – October 2014

US independent power producer Panda Power Funds recently

started up its Temple I combined cy-cle power plant near Austin, Texas. The 758 MW combined cycle gas tur-bine (CCGT) power plant is:

oThe first Flex-Plant in Texas, ad-dressing the need for fast start and ramping.

oFirst use of ‘Shaping Power’ in the US, allowing 10 per cent more power at high ambient temperature.

oCapable of delivering 60 percent of full load in less than 25 minutes.

Texas is one of the fastest growing states in the US, with four of the fastest growing cities in the country. With a population that is expanding at more than 1,000 people per day, de-mand growth is projected to outpace growth in supply. The target reserve margin in the ERCOT transmission system region serving Texas is 13.75 per cent. How-ever, at a load growth rate of 2-3 per cent, Panda predicts that margins will fall to about 5 per cent by 2023. At the same time, the state has a considerable amount of wind power, which calls for flexible conventional power generation to provide support when the wind is not blowing. The scenario creates a perfect op-portunity for investing in gas fired

generation in the Lone Star state. “There’s a big need for power. With reserve margins declining and coal challenged as a generating fuel, we see a great opportunity to capture a first-mover advantage in Texas,” says Bill Pentak, Vice President of Investor Relations and Public Affairs, Panda Power Funds. With ERCOT essentially being an island, unable to import power, Pen-tak believes that its high efficiency CCGT units are the “perfect solu-tion”. Not only will they be high up the dispatch merit order, due to their high efficiency, they will also be able to dispatch power at short notice and ramp up and down. Satisfying the market conditions dictated the choice of technology for Temple I. The plant, being built by a consortium of Siemens and Bechtel, uses Siemens’ Flex-Plant technology. It is the first time the technology is being deployed in Texas and only the third time in the US. Siemens provided the thermody-namic cycle design and power island engineering, delivered the main plant equipment and also has a long-term service agreement for the main gen-eration components.

Plant configurationThe power island includes two SGT6-5000F gas turbines, one SST6-5000 steam turbine, two SGen6-1000A generators, one SGen6-2000H gen-

erator and an SPPA-T3000 instrumen-tation and control system. Siemens also supplied two Ben-son duct-fired heat recovery steam generators (HRSGs) manufactured by NEM USA Corp. The steam turbine produces about a third of the power of the facility with two-thirds from the gas turbines. Each gas turbine has a 13-stage ax-ial flow compressor with can-annular combustors and a 4-stage turbine. The plant has a multi-shaft 2-on-1 con-figuration, where exhaust gas from the turbines enters the HRSGs to gen-erate steam that is then fed to a single steam turbine. The steam turbine, which has a combined HP/IP section with a dou-ble-flow LP section, is designed to use steam at temperatures of approxi-mately 1050°F (565.5°C) and pres-sures of approximately 2400 psi (165 bar). Like each of the gas turbines, the steam turbine, has its own genera-tor. This configuration has the flex-ibility to run the gas turbines without powering the steam turbine (if less power is needed), run only one gas turbine, or run both gas turbines and the steam turbine for full plant output.

Highly flexibleThe Temple I power station is capa-ble of being synchronised to the grid in 10 minutes, making it suitable for complementing Texas’ considerable

Temple I power plant has now started commercial operation By Junior Isles

In addition to being the first Siemens Flex-Plant in Texas, it is the first in the USA to feature Shaping Power for increased power production on hot days.

www.gasturbineworld.com GAS TURBINE WORLD September – October 2014 21

wind power generation. Baseload is reached in less than 60 minutes. Jacki Engel, Product Line Manag-er, Siemens Energy Solutions Ameri-cas comments: “The plant is really designed with the end user in mind. It will allow Panda to optimize profit-ability and provide reliable, flexible, clean generation for the Texas mar-ket.” The HRSGs are an integral part of the Flex-Plant as they allow un-restricted gas turbine ramping. They are horizontal, three- pressure natural circulation once-through boilers with reheat. Each of the HRSGs is capable of delivering 99.5 kg/s of high-pressure steam at 159 bar and 567°C. The boil-ers are also equipped with supple-mentary firing to help optimize plant performance. The Benson boiler technology es-sentially replaces the thick-walled drum in the HP section of a conven-tional boiler. Eliminating thick-walled components enables the boiler to warm faster, allowing it to receive en-ergy faster from the gas turbine. “We talk a lot about integration and the major components are critical, but maximizing the value of these compo-nents through the bottoming cycle de-sign is what sets the Flex-Plant apart,” says Engel. “Some of the key features of this

integration include a two-stage attem-peration scheme, steam turbine piping warm-up strategy, and an auxiliary boiler that allows the plant to main-tain high metal temperatures over a longer shutdown period so the plant can be started quickly. These are all brought together and controlled by the SPPA-T3000 control system.” Such integration enables Temple I to achieve 60 per cent of its 758 MW baseload power output in less than 25 minutes. In addition to allowing Panda to deliver power to the grid faster, the shorter start time helps to reduce the plant’s emissions footprint. Temple I is able to maintain air compliance standards i.e. carbon monoxide (CO) emissions less than 10 ppm and nitro-gen oxide (NOx) emissions less than 2 ppm. Engel explains: “In a conventional [CCGT] plant, from the start of the gas turbine, you will come up to, say, 25 per cent [of full load] and hold, so you can bring some of your big met-als up to temperature. “But that is not the most efficient place for a gas turbine to hold – not only are you burning fuel but you are also loading up on your start-up emis-sions. The fast start capability brings about an 85% reduction in CO and close to 90% on NOx.” Another attribute that makes the

plant so flexible is the inclusion of Shaping Power in the gas turbine. Ac-cording to Siemens, Shaping Power can boost turbine output by 10 per cent on hot days. “You start to see the benefits of Shaping Power above 70°F,” said Engel. It is the first time the technology is being used in the US. Gas turbines suffer significant de-rating at high ambient tempera-tures. Siemens’ Shaping Power tech-nology allows the gas turbine’s inlet guide vanes (IGVs) to be opened on hot days. This increases mass flow through the engine, and also contrib-utes additional exhaust gas flow for the bottoming cycle, resulting in over-all higher plant output. “Historically this was done only with slow-moving duct firing in the HRSGs, says Engel. “With Shaping Power, the fast-moving gas turbine is filled up first so the topping cycle generates power more efficiently and exhaust energy is also increased since you have more mass flow through the turbine. “On top of that you still have the ability to duct fire, as needed. The result is a lower heat rate for a given megawatt level, with the ability to generate more power output.” Station Site Manager Sean Haus-man points out that “we can gain 1.5-2% of efficiency by sliding in to this

Figure 1. Temple I is online and ready to feed power into the ERCOT grid on demand.

22 GAS TURBINE WORLD September – October 2014

power shaping mode. It leans-out the engine a bit and sure, it shaves [off] a few megawatts of our net capability, but there is an overall improvement in efficiency. “And as demand grows we can eas-ily transition out of this mode within minutes into a typical combined cycle mode and fire our duct burners.”

Steam water cycleCooling for the plant is provided by cooling towers supplied by Interna-tional Cooling Tower Inc. These re-move heat from the cycle through wa-ter vaporization and air circulation. Hotter water from the steam tur-bine condenser is pumped to the top of the cooling tower where it then runs down the ‘fill material’ (essen-tially corrugated plastic). Air in turn is pulled up through the fill material by the large fans and cools the water. The water collects in the cooling tow-er basin where it is then pumped back to the condenser to repeat the process. These cooling towers have twelve (12) individual cells with fans each measuring more than 30 ft. in diam-eter. A Steam and Water Analysis Sys-tem (SWAS) helps control the puri-ty of water and steam in the HRSGs and steam turbine, which is required to be ultra-pure. The plant operators and chemists use the SWAS to verify proper operation of the condensate polisher system and chemical injec-tion systems. There are two main SWAS shel-ters at the facility with a total of 27 sample streams from both HRSGs and the steam turbine. Some 51 analyz-ers measure the chemical properties of the steam and water. For example, they measure pH, conductivity, dis-solved oxygen, sodium, and silica. These elements prevent rust, oxida-tion and/or fouling, or the unwanted material on solid surfaces. The analyzers are extremely ac-curate. For example, the dissolved oxygen analyzer can measure 1 part of oxygen per 1 billion parts of water.

The Temple Plant is permitted as a Zero Liquid Discharge (ZLD) facility, which means no process or wastewa-ter is permitted to leave the site. Most of the water for this plant

is supplied from the City of Temple Waste Water Treatment Plant Facility. It is reclaimed water that would oth-erwise be lost and discharged into the local water streams. This water con-

Figure 2. The once-through HRSGs are central to the plant’s flexible performance.

Figure 3. The SPPA-T3000 control system manages the integrated operation of all of the major equipment in the plant.

24 GAS TURBINE WORLD September – October 2014

servation measure helps to conserve a valuable natural resource. The high water quality required to run the plant is met by further treating the reclaimed water through the onsite clarifiers, purification filters and re-verse osmosis units. All process wastewater streams are treated through the ZLD wastewater treatment equipment. Here the waste-water is treated and separated into two process streams. Clean water is recycled back into the process systems for further reuse and the reject water is discharged to the site evaporation pond.

Plant controlThe SPPA-T3000 control system manages the integrated operation of all of the major equipment in the plant to enable fast, flexible operation while assuring all components are operating within their individual design enve-lopes. The control system monitors and processes approximately 9000 data points for the core power island and approximately 2500 more for the rest of the plant. According to Siemens, the control system is designed with a database set up like the worldwide web, which enables the hardware to be easily up-graded as technology changes without needing to change out the whole con-trol system. The logic programmed into this integrated system monitors conditions throughout the plant and provides op-erators with real-time information on equipment status. This information from the control system is remotely monitored at the Siemens Power Diagnostic Center in Orlando, where experts track trends throughout the fleet. A dedicated en-gineer tracks the behaviour of this particular plant and looks for changes over time, which enables early warn-ing of potential problems before they happen. The control room is manned 24/7. Temple 2 will also be controlled from

this same control room. Should there be a need, this plant can be started and stopped from the Power Diagnos-tics Center in Orlando.

Safe constructionBechtel was responsible for the bal-ance-of-plant engineering, overall plant construction, procurement, and led the commissioning of the facility. The plant, which was completed two weeks ahead of schedule, was built on a short time schedule – just two years from ground-breaking in September 2012. Describing the early work, Mike Robinson, Project Manager for Bechtel recalls that “we had about 80,000 cubic yards of excavation. There were about 24,000 cubic yards of concrete and over 1,000 tons of steel that went in across the plant. Construction, basically took place al-most around the clock. We were lit-erally making concrete pours in the middle of the night.” Notably, all the work including some complex heavy lifts of the gas turbine was performed without inci-dent. “For the entire duration of the project [more than 2 million man-hours] there was not a single lost-time accident… There were no injuries and

no incidents around the heavy lifts – and there were some significant lifts. A jack and slide system was used to lift and position the gas turbines. The heaviest lift performed onsite was the steam turbine-generator weighing 375 tons.” In addition to completing the proj-ect without incident and two weeks ahead of guaranteed schedule, Robin-son noted that the plant performance was also better than its guarantees. “We got through performance test-ing in one shot and the reliability and availability were close to 100% dur-ing testing.”

More flexible plantsJust two weeks after the start-up of Temple I, Panda Power also fired up what is essentially a sister project in Sherman, Texas. With Temple I and Sherman up and running, work is now firmly focused on Temple II. This plant is expected to start commercial operation next summer, to add another 758 MW to the site. The projects are part of a growing Panda portfolio of combined cycle projects that demonstrate the impor-tance of flexibility in many parts of the US. n

Figure 4. Steam and Water Analysis System (SWAS) helps control the purity of water.