**2. Methodology**

To achieve the objectives mentioned above, a reference electric cabin is defined in Section 2.1, and the air conditioning configurations described in Section 2.2 were examined—that is, traditional vapour compression cooling (baseline strategy, mechanical vapour compression (MVC)), vapour compression cooling combined with airside free cooling (FC), and waste-heat-recovery-based absorption cooling (ABS). Each air conditioning option was evaluated in combination with either DC or CT in order to identify the best-performing configurations.

The cooling systems for the reference cabin were modelled with the transient energy simulation software TRNSYS [33] in locations representing worldwide climate zones as defined by the ASHRAE [34] using climate data available with TRNSYS, as specified in Section 2.3. To evaluate the water–energy impact of these systems, the primary energy demand as well as the carbon and water footprints were calculated for each configuration by evaluating the direct electricity and water consumption based on simulations, as well as indirect contributions such as carbon emissions, primary energy and blue water consumption associated with electricity generation in each location, based on the approach and assumption described in Section 2.4. The economic e fficiency was also assessed using the data reported in Section 2.5, particularly by establishing if and where absorption cooling is able to compete with the airside free cooling configuration.

#### *2.1. Air Conditioning System and Building Specifications*

The cabin cooling system consists of an air-cooling unit located inside the room, where the thermostat is set to keep the inside temperature under 40 ◦C—a safety operation threshold provided by electric equipment manufacturers.

Compared with data centres [30], the regulation requirements for electric cabins at steelmaking sites are substantially less restrictive, as they house robust equipment designed for harsh working environments. Thus, in this study, it was assumed that the temperature control system operates with a set point temperature of 35 ± 2.5 ◦C. In this analysis, a 1000-kW cooling load from internal equipment was assumed as typical for a reference electric cabin having a building surface area of 3700 m<sup>2</sup> and a volume of 17,000 m3. Outside electric cabins were investigated in the present work in order to determine the extent to which local climate a ffects the cabin cooling load and the performance of di fferent cooling systems. The thermal transmittance of the cabin was evaluated based on data provided by cabin manufacturers at 0.4 <sup>W</sup>/m2·K.
