The impact of electricity network and generator models on the accuracy and computational efficiency of multi-energy system investment and operation planning

As energy sectors become increasingly interconnected, selecting appropriate representations of physical characteristics in energy system optimization models has become challenging. This study evaluates the necessity of transmission and generator models by systematically excluding each one and assessing the impact on objective values, solution time, and feasibility of the resulting system design. We apply this analysis to two contrasting case studies optimizing the design and operation of: the IEEE 118-bus test power system and a zero-emission multi-energy system of the Netherlands. Results show that modeling Kirchhoff's Voltage Law (KVL) and alternating-current (AC) transmission losses is essential for accuracy and feasibility. KVL prevents unrealistic network loops; hence improving network utilization. Additionally, we evaluate two linearization methods for the AC transmission losses. Our findings indicate that tangent-based linear approximations often lead to infeasibility with three or fewer segments, whereas a piecewise-linear approach with at least two segments ensures accurate and computationally efficient solutions.