Siemens H achieves full power

A piece of gas turbine history was made towards the end of April at E.ON's Irsching 4 site when the world's most powerful air cooled gas turbine (and probably the largest gas turbine of any type yet built) – the Siemens SGT5-8000H – achieved "baseload" operation (ie its 100% power level of around 340 MW) for the first time. This was part of a major programme of product validation testing currently underway. Another important milestone had been reached on 7 March, with first grid synchronisation of the new machine.

The basic product strategy for the Siemens H class turbine, established seven or eight years ago, as well as requiring a combined cycle net efficiency of over 60%, emphasised the need for fast start capability and high operational flexibility – leading to the choice of a fully air-cooled machine, and the eschewing of any kind of steam cooling. This strategy has proved remarkably robust. Indeed, the value the market attaches to these characteristics seems to have increased markedly recently, not least because of greater amounts of wind power on the grid.

Siemens also hasn't done too badly in terms of hitting key dates in the development programme. First firing on 20 December last year was "non-negotiable" says Willibald Fischer, Siemens' SGT5-8000H programme manager. For one thing "we had invited a lot of people" he jokes.

But bearing in mind the very expensive and traumatic problems that gas turbine manufacturers have had with the commercial introduction of new large machines in recent times, Siemens is taking no chances on the product validation front. Its still a "green banana," says Willibald Fischer, in need of ripening, and a lot "more work needs to be done before we sell it."

Siemens test centre at Irsching. Note the curved corners, which E.On plans to adopt on future power plants (see visualisation of Irsching 4 CCGT, below)

Visualisation of the Irsching 4 combined cycle power plant, which will use the SGT5-8000H

The "commercial release" date is currently scheduled for August this year. This will be "Gate 4" in the Siemens terminology, allowing marketing to start. Gate 1 was formulation of product strategy (21 March 2001), Gate 2, start of basic design (5 Nov 2001) and Gate 3, product release (17 Aug 2004).

The prototype testing is being done with the gas turbine under Siemens ownership. There are over 2838 test sensors on the machine, 597 of them for rotating parts, with information transmitted to Muelheim, Orlando and Jupiter as well as within the Irsching test centre itself.

Once the testing has been successfully completed the heavily instrumented simple cycle plant will be converted to a single shaft combined cycle unit, with the addition of a Benson HRSG and steam turbine, and ownership transferred to E.ON.

Willibald Fischer, Siemens' SGT5-8000H programme manager

The new H gas turbine will enable combined cycle steam conditions of 170 bar and 600°C to be achieved.

Siemens hope to be able to offer a 60Hz version in 2010. The scaling is considered to be relatively straightforward process, with the number of burners reduced from 16 to 12. Discussions are underway with contenders for the 60 Hz lead project.