Renewable sources are on the brink of a boom, with the majority of new installations being solar and wind non-dispatchable plants. This increases the need for flexibility and back-up resources in other parts of the power system. Although several ways of enhancing flexibility exist, flexible power plants, in particular plants that are already operational, must provide the needed flexible back-up in the short term, with other measures, such as demand-side participation, coming into play at a later stage.
Additionally, high operational flexibility – the ability of power plant for fast start-up and to adjust load output fast and predictable to changing market requirements – is an essential prerequisite to ensure economic success in a liberalized market. Coping with power ramps – sudden and massive requests of active power – will become increasingly relevant. Demand has always been variable and flexibility requirements have thus always existed, now however power ramps are adding a new dimension on top of the traditionally variable electricity demand, thereby introducing a step-change in the way the electrical systems are operated.
In the last 10 years, the main focus area for power generation companies – triggered by the deregulation of electricity market – has been the switch from baseload to intermediate load, and thus the need for fast load ramps, shorter low-load and start-up times, and grid stabilization.
By the year 2020, supposing that the development of renewables such as wind and solar energy takes place as planned, we will be faced, in rapid succession, with periods in which there is going to be an over- or under-capacity of several gigawatts, which the system will have to accommodate. Country and power grid specific capabilities are necessary to guarantee security of supply, such as primary control, secondary control, capability for island operation, load rejection, black start capacity, grid restoration following blackouts.