Available technical flexibility for balancing variable renewable energy sources: case study in Belgium

The recent evolution in power systems, including increased share of renewables and a modification of the power plant fleets entail new constraints, e.g. on the peak capacity or on the technical flexibility required on the grid. This study simulates the Belgian power system using Dispa-SET, a unit commitment and optimal dispatch model developed within the Joint Research Centre. Different “what-if” scenarios are defined and evaluated by varying the availability of major nuclear and CCGT power plants, or the share of renewable capacity in the system. Key findings include:
If the nuclear power plants of Doel 1, 2 and 4 had not been available in 2012-2013, 76 hours of capacity deficit would have been stated.
If, in addition, the two CCGT power plants of Vilvoorde and Seraing had been disconnected, the number of deficit hours would have risen to 450.
There is enough technical flexibility on the system to accommodate significant shares of renewable energy (up to 8 GW additional capacity, corresponding to 17% of the yearly generation).
CCGT power plants are submitted to more on/off cycles as the share of renewable energy increases.
In high renewable penetration scenarios, CCGT power plant are committed preferably over less flexible nuclear or coal power plants. It is therefore necessary to set up proper markets mechanisms to maintain these plants on the grid.