Power System Transformation for Dummies
Power system transformation
understanding the challenges
The impact of dispatchable renewables
Decarbonising their power sector, countries with large amounts of hydro (for example Sweden) need to deploy less vRES than those without these resources. The same holds for geothermal resources (Island, Kenya) or sustainably produced energy crops (biomass).
Of course, this reduces the challenges associated with vRES.

The capability of dRES to respond to the instantaneous load determines the maximum System Non-Synchronous Penetration (SNSP). The schematic illustration of the load supplied by dRES and vRES indicates - whatever the instantaneous vRES output is, a certain portion of the load can covered by dRES, i.e. synchronous generation. Of course, with low load and high vRES output residual load tends to get negative. In that case, one of both options, vRES or dRES, needs to be limited in order to maintain system balance. This is just an indicator for some operational flexibility.

dRES in Load Duration Curve - principle

Availability and flexibility of dRES differs per country. Let's compare the two illustrative graphs below [1]:

In Sweden, the large hydro capacities are following the demand. dRES dispatch is close to the diagonal line in the graph. This indicates that, whatever the instantaneous load is, a proportional share is provided by dRES.

dRES of load, Sweden
In contrast, in Germany, the available dRES capacity is not only much lower, it also does not respond to actual demand. dRES will not help to limit vRES penetration, certainly not in case of high load.

dRES of load, Germany

These differences characterise the particular conditions of geographic regions and have to be taken into account when reflecting specific challenges of particular countries.

[1] 2018 data. Data source: ENTSO-E transparency platform.

LDC and residual load Overview Phases Load Changes, Flexibility and Storage