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Combined-cycle plants are arguably the least well-known electrical plants, but in Spain they account for 25% of the country’s installed capacity. There are ten units based on this technology, manufactured by Siemens: two in Campo de Gibraltar (Cádiz), three in Palos de la Frontera (Huelva), two in Arrúbal (La Rioja) and three more in Sagunto (Valencia). Today, these plants continue to work as the most useful safeguard to guarantee Europe’s energy generation system, counted among the least contaminant fossil fuel combustion plants in the world. Their thermodynamic efficiency, in other words, the percentage of energy that can be obtained from the fuel, is around 60% (much higher than that generated by a coal-fired plant).

The key lies in its operation. This technology generates electricity from the rotation of a turbine propelled by the combustion of natural gas. Apart from the electrical energy generated by the gas turbine itself, the resultant heat from this combustion is used to heat water, converting it into steam
to be used in a second turbine that also produces electricity. Moreover, the application of Siemens technology improves these ratios, by reducing CO2 emissions by one third. Siemens’ SGT5-8000H gas turbine has broken a world record by exceeding 60.75% efficiency at the Irsching plant in Germany.

Despite the advantages of combined-cycle plants, they only covered 8.5% of electricity demand in 2015, at the same time as playing a leading role in complementing renewable energy sources; as clean and they are unpredictable as they only produce where there is sun and wind. As such, combined-cycle plants, that were originally designed to mainly operate at full load, are able to handle difficult market conditions: fewer operating hours, a reduction in megawatts generated, a higher number of start-ups and greater market control as regards gas reserves. And they are achieving this in a scenario in which energy demand is once again on the up, at the same time as the ageing of the plants is becoming more pronounced. Read more…

Laurent Dendrael
Head of Service for Combined Cycle Power Plants, Siemens Spain

Article published in: FuturENERGY January-February 2016