Including system integration of variable renewable energies in a constant elasticity of substitution framework: The case of the WITCH model

- The choice of a CES structure for power sector modeling highly impacts results.
- Technical aspects related to VRE penetration require further explicit constraints.
- Ensuring flexibility to meet demand fluctuations may imply lower power production.
- Ensuring capacity to meet peak load leads to installation of backup capacity.
- Storage, if available, can provide significant flexibility and backup capacity.

The penetration of variable renewable energies (VREs) in the electricity mix poses serious challenges in terms of management of the electrical grids, as the associated variability is in contrast with the requirement that the load be instantaneously equalized by the generation. One of the goals of Integrated Assessment Models (IAMs) is to simulate the evolution of electricity demand and generation mix over time, therefore a proper modeling of VRE system integration is crucial.In this paper we discuss how different modeling mechanisms can profoundly impact the evolution of the electricity mix, and specifically renewable penetration. In particular, we focus on the effects of introducing a set of explicit system integration constraints in a model, WITCH, characterized by a Constant Elasticity of Substitution (CES) framework. The role of the implementation of storage is discussed as well.