Installed vRES capacity is much higher than system minimum load.

Milestones
Large parts of the year (lets say more than 1000 hours), the system is being operated with very high vRES shares (lets say more than 75% SNSP). Regardless these challenging conditions, supply is of uncompromised quality. Also during the periods, where vRES contribution is very low, supply from dispatchable generation is reliably available.
vRES share in annual generation is not restricted by technical limitations. However, because of the fluctuating nature of the resource in combination with definite flexibility of the system, still part of the annual load has to be supplied by dispatchable generation and vRES shares are 70% to 80%. Further sector coupling and economic optimisation of storage and import / exort options is required in order to incrementally increase vRES shares in the annual balance. This is the focus of phase X running in parallel.

Regularly vRES generation results in excess supply which cannot be absorbed by the load. To handle this excess supply, i.e. to maintain system balance, three fundamental options exist:

• vRES curtailment
• export of excess generation (to other regions or other economic sectors)
• storage (also as final energy of the appliances in other economic sectors)

In contrast to previous phases, curtailment as only option is economical infeasible. The share of the annual vRES generation associated with negative residual load is simply too high to dump it.

Deploying the other two flexibility options is a precondition for reliable and cost effective electricity supply. This means phase 4 can only evolve successfully with Phase X running in parallel.