The USA’s ATS programme is now entering its final few months with participants demonstrating and evaluating advanced technologies. PEi examines the programme’s achievements, and finds out what’s next for gas turbine technology development.
In 1992 the US Department of Energy (DOE), together with equipment manufacturers and research organizations, embarked on the Advanced Turbine Systems (ATS) programme. Eight years on, the programme is approaching completion as manufacturers move closer to reaching ATS goals.
The overall objective of the ATS programme was to enable gas turbine manufacturers to capture the bulk of the power generation equipment market of the new millennium with advanced, high efficiency machines. The DOE had forecast that the demand for natural gas in power generation in the USA would triple from the early 1990s through to 2015. The Energy Information Administration estimated that gas turbines could satisfy up to 81 per cent of generation in the US by 2010.
In addition to this potential, the importance of cost of power, environmental emissions and reliability to utilities, industrial users and independent power producers was also recognised. The ATS programme was therefore developed to:
- Boost system efficiency to 60 per cent or more (LHV) for utility-scale combined cycle systems, or a 15 per cent improvement in efficiency for small-scale industrial turbine systems.
- Reduce the cost of electricity by ten per cent compared with advanced (1992 vintage) turbine systems.
- Achieve fuel flexibility.
- Achieve NOx emissions of less than 9 ppm without post-combustion emission controls.
- Offer reliability, availability and maintainability (RAM).
The ATS programme is due to be completed by 2001. Two classes of gas turbine systems have been developed: simple cycle industrial gas turbines of less than 20 MW for the distributed, industrial and cogeneration markets; and large, utility-scale combined cycle gas turbine systems.
Central to the success of the ATS programme has been the availability of funding from the DOE, enabling participants to manage the risks associated with the commercialization of advanced technology. According to the DOE, the total cost of the ATS programme is $700 million, of which around $450 million has been contributed by programme participants.
Road to commercialization
The achievements of the current ATS programme have been significant: the participants have carried out manufacturing and design validation testing of key components and concepts including steam cooling techniques, high turbine inlet temperatures, thermal barrier coatings (TBC), single crystal blades, ceramic blades and recuperator technology.
GE Power Systems: Under the ATS programme, GE Power Systems has developed a 400 MW-class combined cycle system based around an H technology gas turbine. Two configurations have been developed: 60 Hz (7H) and 50 Hz (9H). The ATS machine consists of an 18-stage compressor, a can-annular dry low NOx (DLN) combustion system and a four-stage turbine. The turbine incorporates closed-loop steam cooling and has a firing temperature of 2600°F .
GE announced in April 1999 plans to construct the first 9H power plant at the Baglan Bay energy park near Swansea in the UK. The plant has received all necessary approvals and is scheduled to enter service in 2002. A site for the first 7H machine was announced in September 1999. GE and Sithe Energies will construct an 800 MW plant at Scriba, NY, USA. This plant is scheduled to begin operation and testing towards the end of 2002.
Since mid-1998, GE has completed the 7H compressor rig test, the materials development for the 9H and 7H, the 9H and 7H combustor development tests and the 7H gas turbine development test. It carried out full speed no load (FSNL) testing of the 9H Baglan Bay unit in May 1999 and completed the pre-shipment test of the same unit in the fourth quarter of 1999.
During the pre-shipment tests, the 9H unit underwent five fired starts to FSNL and 18 fired hours. The tests, says GE, gave excellent validation of analytical models, including parameters such as:
- The rotating air/steam cooling system operational with leakage within spec
- The compressor and turbine aerodynamics data up to 108 per cent speed
- The integrity of the rotor structure and the improved marriage joint
- Successful operation of the Mark VI control system with the H system.
GE also completed the first FSNL testing of the 7H ATS unit during the fourt h quarter of 1999. The unit was fired for 18 hours and underwent six fired starts. The test validated rotor dynamics and vibration levels, the scale-up effects from the compressor rig test, the turbine and compressor turbine running clearances and the use of the Mark VI control system. The pre-shipment test is slated for early 2001 before shipping to Scriba in mid-2001.
Siemens Westinghouse: Siemens Westinghouse is also developing a 400 MW-class utility scale combined cycle system under the ATS programme. Its ATS plant incorporates an advanced gas turbine design, a new three-pressure, two-casing steam turbine design and a high efficiency generator.
Its programme will culminate in the introduction of an engine – the W501ATS – that will meet or exceed all ATS programme aims. The company believes that its evolutionary approach mitigates risks associated with the commercialization of advanced technologies and also allows early commercial introduction of ATS technology.
The W501G unit is the first major introduction of Siemens Westinghouse’s ATS technology. Firing of the first W501G at the City of Lakeland, Macintosh unit 5, USA took place on 19 April 1999. The unit has since undergone extensive testing and verification of combustion system variables, engine performance, emissions and thermal paint testing. Conversion of the unit to combined cycle is scheduled for 2001.
Based on the W501 series of heavy duty gas turbines, the W501G incorporates several ATS technologies:
- Advanced 3D compressor
- Advanced brush seals and abradable coatings
- Closed loop steam cooling
- High temperature bond and thermal barrier coatings
- ATS Row 4 turbine blade.
Development activities for the W501G are now focussed on the addition of further ATS technologies to the frame, including the addition of a thin-walled, closed loop steam-cooled Row 1 turbine vane .
Siemens Westinghouse is already offering ATS technologies on its mature product lines for both new units and as a retrofit option. For example, the latest W501F incorporates ATS brush seals, coatings and compressor technology.
Solar Turbines: The first sale of Solar’s ATS unit – the Mercury 50 – was announced in December 1997. The unit is a single shaft, optimized 4.3 MWe machine with better than 40 per cent efficiency at the busbar. It has a highly fle xible combustion system that can be configured for either ultra-lean premixed or catalytic combustion, and features a ten-stage axial compressor and a two-stage axial turbine. Solar expects that the unit will meet the growing demand for highly efficient, environmentally superior power systems in the industrial and distributed power generation markets.
Solar has now entered a comprehensive and ambitious field evaluation programme for the Mercury 50. It already has one machine in operation in the field and another five undergoing installation at various customer sites across the USA. It will use data gathered from these commercial installations to supplement and validate data obtained during development testing of the Mercury 50, and to test its durability.
Solar’s engineering design activities for the Mercury 50 were concluded in mid-1998. Testing of the Mercury 50 indicates that the unit meets all of the original ATS aims of cost, efficiency, emissions, fuel flexibility and RAM. For power generation (non-heat recovery) applications, the Mercury 50’s installed cost is $425-500/kW.
In September 1999, the first Mercury 50 generator set unit was installed at a remote phosphate mining site in Queensland, Australia. This unit now has over 1200 hours of operation in a standby/peaking application. Ano ther field evaluation unit is operating at Solar’s San Diego Harbor Drive Test Facility. The principal DOE host site demonstration machine is at Rochelle Municipal Utilities, Illinois. This machine is scheduled to run for 8000 hours in an economic dispatch application.
Rolls-Royce Allison: Allison’s original objective was to develop a 13.5 MW ATS gas turbine unit with a 40 per cent thermal efficiency, marketed as the Allison 701-K and with an initial field demonstration scheduled for 2000. However, the company’s focus and approach has changed to be more evolutionary to reduce risk and cost.
Allison is therefore no longer pursuing the 701-K engine core, but instead is aiming to address the market with a unit based on the mature and proven 601-K engine core incorporating ATS technologies. This ‘building block’ approach will include the development of advances in combustion technology, ceramic structural components and advanced coating technology. The compan y plans to demonstrate these technologies both internally and at field test sites.
A ceramic first stage turbine vane is under development which will increase efficiency and reduce turbine module cooling flows. A ceramic vane and mount has already been successfully designed and fabricated. Initial tests indicated the need for improved environmental barrier coating technology.
In developing ATS combustion technology, Allison is focussing in two areas: lean premix technology and catalytic combustion technology. The company is aiming to carry out a full scale sector rig test in 2000, followed by an ATS engine demonstration.
The next generation
But advanced gas turbine and power system development will not cease with the ATS programme. The DOE believes that the growing world-wide demand for electricity and tightening environmental requirements will mean that high efficiency gas turbine-based generation systems are set to play a major part in new capacity additions over the next 20 years. Economics currently favour natural gas, particularly in north America, Latin America and Europe.
However, research and development budgets are tightening in competitive power markets such as the US, driving the need for continuing public-private partnerships. DOE and FETC have therefore proposed the Advanced Turbine and Engine Systems Programme to meet the needs of future distributed and central power generating applications. It will consist of Next Generation Gas Turbines (NGGT) and Advanced Engine Systems.
The DOE Energy Information Administration has predicted that 124 GW of new capacity will be required in the USA by 2020. NGGT is designed to help ensure that this demand is met with clean and cost-effective options. Energy security is also a concern, and the DOE has highlighted the need for fuel flexibility and high efficiency.
The NGGT Programme will be divided into three main elements: systems development, research and development, Vision 21 integration and power plant technology. The programme goal is to develop the next generation of turbine-based power systems and to ensure that these systems comply with future environmental regulations, have acceptable life-cycle costs and serve emerging deregulated power markets.
A large part of NGGT will be systems development. This element will focus on the development of flexible turbine systems, turbine-fuel cell hybrids and new, revolutionary concepts, and will be underpinned by supporting research and development. Flexible Gas Turbine Systems (FGTS) will be the main thrust of this element and will fill in the gaps left by the ATS programme. It will include the d evelopment of high efficiency cycling combined cycle systems, cascaded humidified advanced turbines, intercooled aeroderivatives and the integration of ATS technologies with advanced coal-fired plants.
Advanced turbine-fuel cell hybrid plants will also be developed under NGGT to meet the need for high efficiency distributed generation systems. Electric efficiencies of over 70 per cent are envisioned and initial systems will be less than 30 MW in size.
An important part of NGGT and its systems development will be integration with Vision 21, a long-term vision of the development of high efficiency, highly integrated advanced cycles for central power plants. Several agencies, including the FETC, DOE’s Office of Energy Efficiency and Renewable Energy (EE) and the Office of Fossil Energy (FE), will collaborate in several main areas:
- DOE/EE Industrial Power: The development of microturbines for turbine-fuel cell hybrids for distributed and industrial power applications.
- DOE/FE Fuel Cell Programme: Fuel cell stacks for hybrid systems and balance of plant.
- DOE/FE NGGT: Scale up of hybrid systems for Vision 21-scale power plants and adaptation of hybrid systems to use non-traditional fuels. Integration of fuel cells with industrial turbines and balance of plant equipment.
- DOE/FE Vision 21: Integration of hybrids into overall Vision 21 plants producing power and/or fuels.
The goal of Vision 21 is to achieve 75 per cent (high heating value, HHV) efficiencies for gas fuelled systems and 60 per cent (HHV) efficiencies for coal-fuelled systems.
The programme is scheduled to begin this year and will end in 2015. During the first year, NGGT will build on the technology developed under ATS, and the ATS Technology Base programme (R&D) will be transitioned into the NGGT R&D element. R&D activities will be initiated to address ATS applications for coal power plants such as integrated gasification combined cycle and pressurized fluidized bed combustion, an initial step to Vision 21.
During the first ten years of the programme, development issues will be resolved for first market introduction of fuel cell-turbine hybrid systems for distributed power applications, ATS will be enhanced for integration into clean coal technologies and technologies will be developed and tested at full scale for FGTS and other Vision 21 power modules.
The first year of the programme will cost $36 million, including $10 million to complete the ATS programme. Funding needs of the first eight years of the programme are estimated to be $298 million.