GE has launched a major upgrade – called the GT26 HE – for the GT26 gas turbine, and announced that the lead/validation project will be carried out in partnership with Uniper at its Enfield combined cycle plant in the UK, with installation scheduled to take place during a 4 month outage at the plant in 2020.
The HE (high efficiency) upgrade will “unleash the full performance of the GT26 platform”, says the company, promising combined cycle efficiencies in the range 60-61% – unprecedented for an F class machine – building on inherent benefits of the GT26 (originally developed by Alstom), such as sequential combustion, with two sets of burners, a single-stage HP turbine and a four-stage LP turbine.
As well as the increase in efficiency (2 percentage points at baseload), other performance benefits include: up to 1 percentage point increase in efficiency at part load; 15-55 MW more output; and extended inspection interval, from 24 000 to 32000 hours.
Introducing the GT26 HE at an event in London on 22 March, Michael Rechsteiner, GE’s VP, power services, Europe, said it reflected GE’s continuing investment in keeping the mature fleet competitive. “That’s really what it’s all about. We listened to the market and more importantly we listened to our customers, how they are operating in the market and what their pain points and what they need to be more successful.” The key requirements were high efficiency, flexibility and reliability.
The GT26 operating fleet, numbering about 90 machines, may be relatively small compared with, say, the GE F fleet, with around 1400 turbines, but they are “critical units in the grid and for our customers, and we have got to figure out how do we upgrade them to make the units competitive in the market”, said Amit Kulkarni, general manager, F/H class product line, GE power services. While there have been modifications over the years, the GT26 HE is a “step-change” and represents “the biggest upgrade the GT26 has seen in its 20 year history”, with new technologies introduced across the entirety of the gas turbine, including compressor, combustion systems and hot gas path.
The upgrade includes technologies developed for GE’s H class gas turbine (eg intricate blade cooling schemes and advanced coatings), improved combustor design incorporating additively manufactured parts (with better air-fuel mixing enabling NOx compliance to be achieved despite increased firing temperatures) and introduction of new 3D aero-profile compressor components with reduced surface roughness (greatly improving compressor performance while retaining the same basic architecture, with the number of stages remaining at 22, for example). A significant contributor to the greatly increased inspection interval has been a major focus on creep failure and low cycle fatigue, said Amit Kulkarni, and the avoidance of zones where they can interact.
The GT26 HE upgrade is expected to enable Enfield to consistently elevate its position on the dispatch curve in the competitive UK power market and significantly increase its annual operating hours. “It has the potential to be a game-changer for us”, said Pedro Lopez Estebaranz, director, Uniper CCGT asset operations, “putting Enfield ahead of the competition.”
Ansaldo Energia took on the OEM role for GT26 and GT36 turbine technology under a European Commission competition ruling setting out conditions for GE’s 2015 purchase of the Alstom power businesses.