59457 - Turn-Down Capability of Ansaldo Energia’s Gt26 

The operational flexibility of heavy-duty gas turbines is of increasing importance in today’s power generation market. Fast start-up, fast loading, grid frequency support, fuel flexibility and turn-down capability are only some of the keywords that describe the challenges for GT manufacturers.

This paper reports Ansaldo Energia’s activities to further reduce the Minimum Environmental Load (MEL) of the GT26. The difficulties related to operation at very low loads and the solutions that were developed are explained. Furthermore, the results of engine validation tests of the new extended Low Load Operation (eLLO) and extended Low Part Load (eLPL) operation concepts are presented.

The enhancement of the operational flexibility of the GT26 is in the focus of Ansaldo’s development activities since many years. Its sequential combustion system is a very good basis for flexible and emission compliant operation down to very low loads. Ansaldo Energia’s Low Part Load (LPL) and Low Load Operation (LLO) concepts are standard products in the GT26 flexibility portfolio and established in the market since many years.

Low Part Load (LPL) operation extends the standard operating range down to low loads by switching off individual burners in the second combustor (SEV combustor). The compressor mass flow can be varied between idle and base load levels.

Low Load Operation is characterised by a combination of idle compressor mass flow and base load temperatures in the first Combustor (EV combustor). The SEV combustor is switched off. LLO is intended to be a “parking point”, where the plant can operate in combined cycle mode during times of low electricity demand. 

Ansaldo Energia has conducted a development project in the past two years in order to further reduce the minimum simple cycle and combined cycle loads. The extension of the LLO and LPL operating ranges and their combination into one single feature are the main targets of the project.