Grain first fire, and the path to 60%

First firing at the new GT26 based 1275 MW Grain combined cycle CHP plant in the UK was successfully completed on 2 June, with commercial operation expected in the final quarter of 2010. The project was the first turnkey EPC contract signed with E.On for Alstom’s KA26 gas-fired combined cycle plant design. As well as generating electricity, this innovative CHP plant will export waste heat to National Grid’s nearby LNG terminal for converting LNG back to gas ready for use in the UK gas transmission network.

Alstom reports that since the introduction of the GT24/GT26 gas turbines in 1995 – GT24 for the 60 Hz market and the GT26 for the 50 Hz market – more than 100 engines have been ignited in KA24/KA26 combined cycle power plants constructed and built on a turnkey basis. The GT24/GT26 fleet has now accumulated over 3 650 000 fired operating hours with more than 64000 starts under various operating conditions.

The KA24/KA26 plants were launched in time to catch the “dash for gas” boom that was seen in both the 50 Hz and 60 Hz power markets at the end of the 1990s. The first GT24 was fired in 1995 in the Gilbert power station in the US and the first GT26 in EnBW’s RDK4 power plant in Germany in 1997.

The engine design (with sequential combustion) gives it good turn-down capability, which Alstom sees as particularly suitable for today’s market with increasing renewables on the grid. In addition, the KA24/KA26 technology offers what Alstom claims is the lowest minimum-load operating point in the market, with the ability to park the entire CCPP ‘on-line’ at approximately 20% plant load.

With the latest improvements to the gas turbines and the water-steam cycle, the KA26 can achieve 872 MW net combined cycle plant output with 59.1% net plant efficiency at ISO conditions (the Emsland and Langage power plants, in Germany and UK, respectively, being examples). And looking beyond that, Alstom says it is on a ‘path to reach 60% net plant efficiency with the existing engine platform.’ The ‘introductory issues’ encountered with the GT24/GT26 some years ago are now a distant memory.

As well as Grain other KA26 plants due enter commercial service in 2010 include Emsland, Combigolfe in France, Fujairah in the Middle East and Staythorpe, also in the UK.