2.1.1. Voltage on the Grid

Compared with the DC-based method, the AC based approach benefits from being the currently established technology at the airport side. Therefore, a large selection of installation components is available, as are trained technical staff to work with standard grids. However, from a technical perspective, the DC approach has multiple benefits. For example, integrating additional battery storage units and photovoltaic systems is simplified by eliminating the AC/DC or DC/AC conversation stages for all DC-based devices. Therefore, fewer conversation stages are needed between local battery storage, photovoltaic generators, and consumers (e.g., DC chargers). In addition, a DC-based grid increases the system's efficiency and decreases complexity. Furthermore, DC-connected systems are easier to control than AC-connected systems [11].

There is also an advantage when it comes to power distribution cables. An AC system uses a four-wire setup for the power distribution network. As such, the transported power results in Equation (1).

$$P\_{\rm AC} = \sqrt{3} \cdot \mathcal{U}\_{\rm peak} \cdot I\_{eff} \cdot \cos(\mathcal{q}) \tag{1}$$

with the effective current (*Ieff*), the peak voltage (*Upeak*) and the power factor (cos(*ϕ*)). Using the same four-wire setup for a DC system with two wires used for positive and negative, the maximum current per wire matches the effective AC to not overload the conductor. For AC systems, the insulation rates for the peak voltage. As such, the nominal voltage in a DC system can be *Upeak*, and the power in a four-wire DC system results in Equation (2).

$$P\_{\rm DC} = 2 \cdot \mathcal{U}\_{\rm peak} \cdot I\_{eff} \tag{2}$$

Comparing the DC and AC power results in Equation (3):

$$\frac{P\_{DC}}{P\_{AC}} = \frac{2 \cdot \mathcal{U}\_{peak} \cdot I\_{eff}}{\sqrt{3} \cdot \mathcal{U}\_{peak} \cdot I\_{eff} \cdot \cos(\varphi)} = \frac{2}{\sqrt{3} \cdot \cos(\varphi)}\tag{3}$$

Even with a power factor cos(*ϕ*) of 1, the same wire system can transport about 15% higher power using a DC system. Using the reciprocal reduces the required copper crosssection of the wiring system to approximately 85% for the same power. Despite the many advantages of a DC network, however, the AC network is considered in this study because, as already mentioned, the AC network is an established technology, trained specialists are available, and the airport is equipped with an AC network. However, developing a DC network could also become a key element in the future.
