The Mexican Comision Federal de Electricidad has signed a contract with Alstom for the repowering of unit 4 at its Valle de Mexico thermal power station, which supplies Mexico City. The contract is worth $180 million.

The project involves the installation of three 115 MW GT11N2 gas turbine generator units, three heat recovery steam generators associated auxiliary equipment, the electrical and control system and a high voltage switchyard. The gas turbines and steam generators will be integrated with the existing boiler and steam turbine of unit 4 at the plant to create a combined cycle generating system.

Output from the unit will be increased from 300 MW to around 550 MW during hybrid operation. This will involve running the gas turbines and heat recovery steam generators as base load while the existing boiler runs at part load to ensure full load for the steam turbine. The latter was also supplied by Alstom at an earlier date.

The repowered unit is expected to be fully operational by the middle of 2002 and will be the first combined cycle plant in Mexico whose design allows operation in pure combined cycle or hybrid mode.