NRG Energy Inc. and Siemens En-ergy Inc. have completed a repow-ering and modernization project at the 13-hectare El Segundo Energy Center located on the Pacific Coast near Los Angeles, California, U.S.A. The natural gas-fueled, combined-cycle Siemens Flex-Plant 10 power islands have entered commercial operation and added an installed capacity of 550 MW — enough to supply electricity to approximately 450 000 California homes — to bring the facility’s total output to just under 1000 MW.

NRG’s El Segundo Energy Cen-ter is the second Siemens Flex-Plant combined-cycle power plant to open in California — after the Lodi Flex-

“We support the state’s renewable portfolio standard and maintain our tradition of being a good neighbor to the surrounding coastal communi-ties,” said John Chillemi, president of NRG Energy’s West Region. “We have worked with the community to im-prove the visual aesthetics of the site by incorporating native landscaping, installing a new sea wall, improving the bike path along the pristine beach strand, maintaining coastal views with a lower plant profile, and the re-moval of two large oil tanks.”

The most significant environmental benefit was the removal of two 175 MW steam boilers — constructed in 1953 — and the shutdown of one of the 335 MW steam boiler units —

Plant 30 Energy Center in northern California that went into commercial operation last year. Siemens said that both plants are designed for interme-diate to continuous duty and capable of daily cycling.

In 2011 and 2012, more than 1.8 GW of renewable energy was added to the California grid, three times as much as the state’s added fossil power. Complementing California’s growth of intermittent renewable energy sources and contributing sig-nificant environmental benefits to the existing site — improving air quality, reducing noise emissions, and lower-ing the impact on marine life and lo-cal communities — were a major part of NRG’s modernization efforts.

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Emissions REduction tEchnologiEs by mike rhodes

Flexing By The SeaSiemens Flex-Plant 10 provides power for NRG plant upgrade; emissions control, efficiency, lowered environmental impact key aspects

NRG Energy’s El Segundo Energy Center, designed for intermediate to continuous

duty and capable of daily cycling, is the second Siemens Flex-Plant combined-

cycle power plant to open in California, U.S.A.

constructed in 1964 — that relied on ocean water for cooling.

“One of the key benefits of this project is that it retired approxi-mately 1.5 billion L/day of once-through cooling,” said George Piantka, director of Environmental Business at NRG Energy Inc.

Piantka said the new Energy Cen-ter now uses first pass reverse osmosis (RO) reclaimed water from the West Basin Municipal Water District in its operations, requiring 90% less water than traditional ramping solutions and meeting the standards of the once-through cooling initiative in California.

“The facility’s emissions meet or are below federal, state and the South Coast Air Quality Management Dis-trict’s (AQMD) air quality standards, and will use 30% less natural gas per MW than the original steam boilers,” Piantka said.

“The El Segundo upgrade became essential because the available region-al electrical resources have proved to be insufficient to meet the current

and expected growth in the region,” Chillemi said.

“With the recent closure of the San Onofre Nuclear Generating Station (SONGS) and the need to integrate the grid’s rapid increase of renew-ables and replace aging steam boiler generation — consistent with Califor-nia’s 316(b) policy — the El Segundo project adds critically needed genera-tion and reliability for the region.”

For the El Segundo Energy Center, Siemens delivered the first two Sie-mens SCC6-5000F 1x1 Flex-Plant 10 combined-cycle power plants in com-mercial operation in the U.S.A. The main components feature an SGT6-5000F gas turbine; an SST-800 steam turbine; an SGen6-1000A generator; an SGen6-100A-2P generator; a small-footprint, air-cooled heat exchanger; and two NEM DrumPlus heat recovery steam generators (HRSGs).

Siemens also supplied the complete electrical equipment, engineering serv- ices and commissioning of the plant, and its SPPA-T3000 power plant in-

strumentation and control system. From first concept through construc-tion, effective system integration is a big part of every project, and Siemens said the SPPA-T3000 provides an easy-to-use control platform for the entire combined-cycle plant, includ-ing grid connection, water plant and gas compression.

The main drivers of the two Flex-Plant 10 plants are the SGT6-5000F gas turbines, which are integrated with a single-pressure, non-reheat bottoming cycle. Siemens said the new plants will provide high power density while requiring a relatively small plant footprint of 2 hectares each, an especially important feature for NRG because the El Segundo site is nestled between a cliff and the Pa-cific Ocean and the new plants were erected while the existing facility was being operated.

Together, the two units can gener-ate 300 MW — more than half their combined output — in less than 10 minutes and the balance in less than

November 2013 Diesel & Gas Turbine Worldwide

emissions reduction technologies

Siemens delivered two Siemens SCC6-5000F 1x1 Flex-Plant 10 combined-cycle power plants. The main components are an SGT6-5000F gas tur-

bine; an SST-800 steam turbine; an SGen6-1000A generator; an SGen6-100A-2P generator; a small-footprint, air-cooled heat exchanger; and two

NEM DrumPlus heat recovery steam generators (HRSGs).

an hour. Waste heat from each com-bustion turbine will be used to pro-duce steam, which will generate an additional 70 MWs of energy per train.

The small-footprint, air-cooled heat exchanger condenses the steam com-ing out of the cycle back into the liq-uid water so it can be recycled and used again to power the steam tur-bine. Hot steam travels through finned tubes while the cooling air flows across the outer surface to remove the heat, Siemens said. The Flex-Plant 10 pro-vides a net efficiency of nearly 49%, making it much higher in efficiency than conventional peaking solutions, the company said.

This allows the plant to balance fluctuating renewable power genera-tion such as wind and solar power and maintain a consistent and reliable sup-ply of power to the grid, Siemens said.

The site is one of the first to in-corporate the Siemens’ Clean-Ramp Technology, reducing transient emis-

sions as the gas turbines ramp up and down to meet electricity demands.

“We have advantages as an OEM,” said Richard Loose, director of Mar-keting, Energy Solutions, Americas, Siemens Energy Inc. “We can in-tegrate the start-up sequence at a whole new level. We began by plot-ting the events and critical paths that make up a start-up — how can we eliminate this one? How can we overcome that one with an integrated solution?

“We started putting in things like final-stage attemperators, steam pipe warming approaches, steam tur-bine stress controllers, and the NEM DrumPlus heat HRSGs. All of these are integrated through the SPPA-T3000 DCS and have reduced start-up times and emissions.”

NEM said the design of its Drum-Plus boilers ensures that no hold points are imposed on the gas tur-bine during start-up. Whereas con-

ventional drum-type HRSGs run a high risk of severely reduced lifetime due to cycling stresses, NEM said its DrumPlus technology experiences significantly less peak stress because of its smaller drum wall thickness, which is allowed by the external lo-cation of the water/steam separators and other mechanical features.

The company said that fast start-ing power plants have two significant advantages compared to cycling base-load plants — NOx emissions during start-ups are reduced because the gas turbine is able to reach low NOx op-erating loads more quickly; and the plants are able to respond rapidly to fluctuating power demand and mar-ket pricing conditions. These benefits lead to higher efficiencies and in-creased kWh for commercial use dur-ing the first hour, NEM said.

The company said this can result in 89% less CO emissions per start — more than 181 tonnes/yr when com-

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emissions reduction technologies

Siemens’ SGT6-5000F gas turbines, which are integrated with a single-pressure, non-reheat bottoming cycle, are the main drivers of the two

Flex-Plant 10 plants.

REPRINTED FROM NOVEMBER 2013 DIESEL & GAS TURBINE WORLDWIDE Copyright Diesel & Gas Turbine Publications Printed in U.S.A.

emissions reduction technologies

pared to traditional F-class combined-cycle plants — and 95% less NOx.

DrumPlus technology is available for single-, two- and three-pressure HRSGs. Like any HRSG boiler, NEM said the DrumPlus needs no special feedwater equipment, such as a con-densate polishing plant, and can use water that meets ASME requirements. The output of NEM’s HRSGs is 78 kg/s with a temperature of 502°C at a pressure level of 99.5 bar.

“California has some of the most strin-gent environmental requirements in the world, so it’s a good thing the HRSGs and Siemens’ Flex-Plant 10 are capable of controlling the emissions,” said Hans Vanderweiden, manager of Operations, NEM USA Corp. “The communities de-mand it, and they deserve it. The tech-nology is there, and so load changes can be anticipated proactively instead of followed, which allows us even more emissions control.

“The partnerships developed dur-

ing this project have been vital to its success. If our technology helps NEM succeed, then sharing it with Siemens and NRG increases the effectiveness of our collective efforts, especially with these high-demand applications.”

For the repowering project, NRG delivered the engineering, procure-ment and construction (EPC), while Orange County, California, U.S.A.-based ARB carried out the building of the facility. The modules that make up the facility — gas and steam turbines, HRGSs, and components of the air-cooled heat exchanger — were built off-site and brought through the Port of Long Beach and by rail, the com-pany said. Approximately 20 heavy-haul loads were brought through the city on designated routes, NRG said.

“We certainly could not have achieved this without close support and coordination with the cities of Manhattan Beach, El Segundo and Los Angeles,” Piantka said.

Through a 10-year power purchase agreement, Southern California Edi-son will obtain the entire output of the facility, which now produces al-most 1000 MW.

“The El Segundo Energy Center and our Flex-Plant 10 power plants are a collection of different technolo-gies that have been tested and prov-en, but may not have been grouped quite like this,” said Martin Tartibi, head of Gas Turbine Power Plant So-lutions Americas – Power Generation Division, Siemens Energy.

“Techniques are constantly evolv-ing and there are always lessons learned as we look ahead to the next phase. We’re adaptable to the needs of California and as a company we’re looking at the dynamic future of en-ergy in a different way. We’d like to see even more efficient, cleaner, en-vironmentally friendly and cost effec-tive technology that can serve as the backbone to support renewables.” A