Humanity is at the beginning of its third energy revolution, after coal and then oil, we are now moving towards the massive use of renewable energies that we knew since the dawn of time. This change will solve several problems, including climate change, as the concentration of greenhouse gases will stabilise. The success of fossil fuels resides in their storability. Indeed, these energies have been stored in the earth for millions of years and can be extracted whenever humans need energy. Their costs of storage are insignificant compared to their costs of extraction. On the contrary, the main renewable energies are intermittent, i.e. wind and solar energy, and thus cannot be stored. However, these energy can be converted into electricity, heat or another form of energy that can be stored. But storing these energy carriers has a significant cost and thus, redefine the design of the energy system. Hence, the shift from fossil fuels to renewable energies - mainly intermittent - requires a complete rethinking of the energy systemsupply chain from resources to demand while including conversion and storage technologies. In particular, to understand what will be the role of storage technologies in this energy system throughout the energy transition period and after. To address this issue, the thesis addresses the following research question: What is the role of energy storage technologies for the energy transition? Focusing on the role of storage requires the inclusion of its environment, i.e. the energy system. Focusing on the energy transition requires a time horizon fromtoday to about 2050. Thus, answering the research question requires a model that represents the energy systemduring the transition. These has motivated the following five contributions of the thesis. First, it is necessary to review the existing energy system models in the literature. Second, one of these models is improved to account for the complexities of energy storage. This involves, among others, to include different time scales (from hour to ...