Steam Turbines

Suppose the difference between a jet engine bolted to a generator and the whistling kettle on a stove, that is roughly the difference between a gas turbine, covered elsewhere on this site, which burns fuel directly to spin its blades, and a steam turbine, which is spun instead by high-pressure steam produced somewhere else entirely, whether from a coal-fired boiler, a nuclear reactor, or, increasingly relevant to data centres, the leftover heat exhausted by a gas turbine.

That last configuration, capturing a gas turbine's hot exhaust rather than letting it vent uselessly into the atmosphere, using it to boil water into steam, and running that steam through a second, steam turbine to generate additional electricity from the same fuel, is called combined cycle, and it is the reason combined-cycle plants extract meaningfully more electricity per unit of gas burned than a gas turbine running alone, a difference that matters directly to a data centre operator paying for every unit of fuel that goes into its captive power supply.

India's Thermax, better known on this site for its cooling and boiler businesses, has specifically been building out boiler and steam-turbine-based captive power infrastructure aimed at data centres, reflecting how operators chasing reliable, efficient on-site generation increasingly look past a single gas turbine toward the fuller combined-cycle configuration, heat recovery steam generator and steam turbine included, covered elsewhere on this site.

The catch is that a combined-cycle setup is only as fast to build as its slowest component, and because both the upstream gas turbine and the heat recovery steam generator that feeds a combined-cycle steam turbine are themselves sitting in multi-year order queues, covered elsewhere on this site, choosing the more fuel-efficient combined-cycle path over a standalone gas turbine or genset trades a lower running cost for an even longer wait to get the equipment installed in the first place.