Introduction

Two main parts of an energy system are the supply side and the demand side which are connected by the transmission and distribution lines. Historically, the supply side is equipped with thermal power plants consuming fossil fuel to generate electricity. However, the environmental impact of these power plants is considerable which is one of the main reasons behind the integration of renewable energies in the power system. Considering the demand side, energy consumption is rapidly increasing due to various factors such as population growth, economic development, and climate change. It is important to know the energy system’s historical trends as well as its potential future direction. Therefore, this chapter aims to provide necessary background information on the current situation and future predictions of the energy system.