Network constraints in techno-economic energy system models: towards more accurate modeling of power flows in long-term energy system models

Power systems are subject to extensive structural changes as a result of the fact that the share of renewable energies in power supply will increase significantly within the next decades. This requires the transport of large amounts of electricity, e.g. from the North Sea to the large load centres. Moreover, the decentralized installations for the generation of electricity (e.g. PV) need to be integrated in the lower voltage power grids without violating net-safety constraints. As a consequence, the grid load in the system will rise to an extent that is hardly manageable with existing power grid capacities. Therefore, while mostly neglected to date, the importance of considering the power grid in energy system models increases significantly. Within this paper, different examples will be given how network constraints can be considered in techno-economic energy system models with a focus on capacity expansion planning and a long-term time horizon. Firstly, a multi-period linear optimization model will be presented, which comprises the system equations for power generation and transmission. The latter is analyzed with the help of a DC power flow model. Secondly, the usage of an AC power flow modeling tool for a detailed representation of the medium and low voltage power grid will be described. Finally, we will present an illustrative example application of a new mathematical approach for grid modeling in techno-economic energy system models.