Some of the flexibility required to meet the daily variability is provided by hydro pumped storage, reducing the flexibility required from thermal sources. The hydro pumped storage installed generation capacities will increase the flexibility provided by this source by 54% in Vision 1 and by 82% in Vision 3 by 2035. The following figure shows the split of the daily variability between sources.
Figure 4.39: Split of the daily variability between hydro pumped storage and thermal sources 1)
Depending on fuel prices and generators’ strategies, the required thermal flexibility could be provided by either coal or gas. The following figure shows the evolution of the daily variability of gas demand in electrical and real quantities associated with variable generation, based on the assumption of a balanced thermal flexibility split between coal and gas. The flexibility provided by gas is likely to be even greater as gas fired (CCGT) power stations are inherently more flexible than coal fired ones.
Figure 4.40: Potential variability for Visions 1 and 3 in the daily gas demand (left) and electricity generation from gas (right) as a consequence of RES variability 2)
To cope with the expected high gas demand variability, and to compensate for the unpredictability of variable RES, the gas system will have to have sufficient flexibili- ty to provide quick and flexible sources of gas. This increased requirement for system and supply flexibility should drive an increase in both flexible supply sourc- es and interconnection of markets to ensure the availability of flexibility in the areas where it is required.
1) As the graph reflects power generation, it is expressed in electrical units. 2) For the conversion to gas demand 50% efficiency has been used.