The deregulation of the energy market in the EU has paved the way to the birth of local energy exchange marketplaces, where power production and consumption volumes are exchanged on demand basis in a competitive environment, bringing to a floating production demand as a consequence.
Flexible operation, in terms of superior capacity of the power plant to promptly respond to sudden change in demand and supply, is now a common requirement for all power systems. Flexibility is especially prized in twenty-first century power sector, with increasing levels of grid-connected variables due to the renewable energy (primarily, wind and solar).
In this new frame, all Customers need to match the up-to-date requirements of the power market with the capability of the combined cycle to switch from the traditional base load operation to the challenging peaking profile, or intermediate, where 50 to 250 start-ups per year can be common.
In particular critical situations for a steam turbine in power plant are:
- short start-up time,
- variable start-up mode
- operation at the minimum environmental load, preserving the plant from frequent heavy - transients
- frequency control implementation in order to allow a better response of the whole combined cycle to fulfil the requirements of the national grid codes
- shut-down modes to limit the cooling of the steam turbine during overnight shutdown
The paper summarizes Ansaldo Energia experience in steam turbine improvement of flexible operation in highly competitive energy markets.