Getting up steam

A turbine cooling system could dramatically improve the efficiency of gas and coal-fired power plants, according to Siemens engineer Dr. Detlef Haje.

The patent-pending system has been designed to allow steam turbines to operate at higher temperatures and pressures than was previously possible.

Haje said that while the efficiency of steam turbines can be improved by increasing pressure and temperature, the materials used within them (such as 10 per cent steel chromium alloy) are typically unable to operate at more than 600°C and pressures of 300 bar. Beyond this, he said, the strength and oxidation resistance of the material are severely compromised.

One way round the problem is to use materials such as nickel alloy that operate effectively at extreme temperatures. But compared to the traditional choices these newer materials are expensive.

Thus Haje has developed a concept for a cooling system that cools areas of the rotor and the blades that are directly affected by the steam. Owing to the system’s patent status, he was unable to reveal the complex workings of his system, but did explain that it provides ‘active cooling that can be concentrated precisely on highly stressed areas’.

He added that while costing little to implement, the technology will allow power plant operators to generate the same amount of electricity with less fuel, enhancing their competitiveness.

‘It’s difficult to quantify efficiency improvements but increasing the operating temperature from 600 degrees C to 700 degrees C would bring you up to overall plant efficiencies of 50 per cent from 46 per cent now,’ claimed Haje.

He said that the relatively slow innovation cycle and long lead times involved in the steam turbine industry make it unlikely that the technology will be commercialised soon, but added that he has no doubt that it will eventually be embraced by the industry.

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