**4. Conclusions**

In this study, the energy, water, CO2 and primary energy consumption of different configurations of air conditioning systems for electric cabins were analysed considering 16 ASHRAE climate zones worldwide. The case at hand refers to electric cabins of EAF steelmaking sites, but the methodology and general results could be easily extended to similar installations in process industries having considerable low-grade waste heat flows.

It was confirmed that the proposed waste heat utilization system for absorption cooling allowed substantial energy savings and an overall favourable water–energy–GHG balance in all climate zones compared with traditional mechanical vapour compression air cooling systems for electric cabins. Compared with the simple airside free cooling configuration proposed here, absorption cooling was also the better option as to electric energy consumption in nearly all climate zones (15 out of 16 climate zones for systems with cooling towers and 12 out of 16 climate zones for systems with dry coolers as heat rejection units). A similar trend was observed for GHG emissions and primary energy demand, which had more or less pronounced differences depending on the local electricity generation mix of the analysed locations. In some cases, such indicators were shown to be more heavily affected by the country's energy mix than by climatic conditions.

However, it was shown that in configurations using cooling towers, free cooling led to significantly lower direct water consumption in nearly all climate regions, and to a lower overall water footprint, particularly in mixed to very cold climates. In climate regions 4B to 7, free cooling was also more cost effective than waste-heat recovery for the examined ranges of economic parameters. In those regions, free cooling also allowed substantial energy savings, though lower than those of corresponding absorption cooling solutions.

Hence, in general terms, our results indicate that waste heat recovery for electric cabin cooling is an energy efficient solution which is also water efficient when dry cooling systems are used. In systems with cooling towers, it generally decreases the system's water footprint compared with baseline configurations, but not with free cooling alternatives. Under the technical and market conditions examined in this paper, absorption cooling was clearly the least cost option for electric cabin cooling in warm to very hot climate zones, but where CTs are used it is the most water-efficient option only in very hot dry climates.

Due to the better performance of absorption cooling in terms of energy and carbon footprint, even in cold climates and with a low-carbon national energy generation mix, carbon- or energy-efficient incentives could make it economically feasible also in further climate regions (e.g., in mixed climate zones), even for systems using cooling towers and at high water prices. In that case, industrial designers and energy managers might prefer absorption cooling solutions because of their energy efficiency even where, compared with FC, they are suboptimal in terms of water consumption.

It is thus recommended that, particularly in intermediate climate conditions, decision makers accurately evaluate the water footprint of their energy efficiency projects; the approach proposed in the current analysis could support them in this task. It is also desirable that policy makers who design incentives supporting industrial energy efficiency or GHG reduction combine them with constraints or incentives for water consumption reduction, taking a nexus approach.

**Author Contributions:** Conceptualization: D.C. and O.S.; Methodology: collectively developed by all authors; Investigation: M.S. and A.Z.; Software and Visualization: M.S. and A.Z.; Supervision: D.C., O.S. and A.D.A.; Writing—original draft: D.C. and M.S.; Writing—review and editing: O.S., A.Z. and A.D.A.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
