The development of hydro, wind and solar power is growing strongly with as one objective to limit and reduce greenhouse gas emissions. All these renewable energies are intermittent with more or less strong variability. This course provides the basis for estimating the resource of these different modes of production and understanding the physical causes of intermittency and seasonal variability. The different modes of electricity production are detailed as well as the sensitivity induced by meteorological variations. Short and medium term forecast becomes a fundamental issue in the development of these renewable energies and in their integration to the electricity network. We therefore present the methods and tools used for a reliable forecast of the electricity production of hydro, wind and solar power plants. This MOOC has been supported by Ecole Polytechnique and was developed in the frame of the Energy4Climate Interdisciplinary Center of Institut Polytechnique de Paris in collaboration with Ecole des Ponts