Electricity Transport and Storage

This chapter focuses first on electricity transport and the corresponding grids. The basics on electricity networks include a discussion why alternating current (AC) prevails in today’s electricity grids and what the structure and the layers of current electricity networks are. Then the physical concepts describing electricity flows are introduced, notably the laws of Kirchhoff and Ohm. For the analysis of AC power flows, equivalent circuits with their combination of resistors, condensers and inductors are introduced as well as phasors which enable power flow computations using complex numbers and a graphical interpretation of active and reactive power. The full AC power flow equations are presented as well as the linear approximation as so-called DC power flow. Furthermore, key components of electric networks including high-voltage lines (HVAC and HVDC) and flexible AC transmission systems (FACTS) are characterised. Also, the principles of system operation including N-1 security and ancillary services like frequency control with operating reserves are discussed. The second part of the chapter deals with storage, starting with a brief discussion of the basics of operation. Then the main technologies including hydro pump storage plants and batteries are characterised alongside with other potential technologies in future systems such as flywheels, supercapacitors, compressed air energy storage or power-to-gas (PtG) technologies.