Integrated Design Tools for Advanced Atmospheric Water Generators in Building-Scale Water–Energy Nexus Solutions

Original Authors: Lucia Cattani, Roberto Figoni, Paolo Cattani, Anna Magrini

Original paper is accessible at: https://doi.org/10.3390/en18143874

The water–energy nexus highlights the deep interdependence between energy production and water resources, emphasizing the need for integrated solutions in both infrastructure and building design. This study focuses on embedding advanced Atmospheric Water Generators (AWGs) into building energy systems, addressing water scarcity and efficiency challenges through simulation-based integration. While AWG technology has matured—particularly vapor-compression refrigeration cycle (VCRC)-based systems—their potential as multipurpose devices capable of producing water, heating, and cooling remains underutilized in building-scale design tools.

Methodological Framework

The research builds on a prior methodology combining AWGSim—a simulation tool tailored for AWG thermodynamic modeling—with DesignBuilder (DB), a commercial building energy simulation platform. AWGSim models the system’s thermal and moisture performance using physically based energy and mass conservation equations, while DB allows dynamic modeling of buildings, HVAC systems, and environmental conditions.

Key steps in the integration process included:

• Case Study Selection: A hospital wing in Pavia, Italy, requiring both high-quality water and thermal energy (cooling and domestic hot water).

• Data Acquisition: Geometric, HVAC, and operational data were collected from official design documents, on-site surveys, and 2023 energy consumption records.

• Modeling and Validation: The existing HVAC system was scaled to the hospital wing, simulated in DB, and calibrated against real-world energy use. AWGSim outputs were used to model the AWG’s thermal functions (cooling, heating, and post-heating) in DB.

• AWG Implementation: The AWG was modeled to supply 11,015 m³/h of cooled, dehumidified air, recover condenser heat for domestic hot water (DHW) and post-heating, and supply water for photovoltaic (PV) panel cleaning.

Case Study and Simulations

Two configurations were compared:

1. Configuration A: Existing HVAC system only.

2. Configuration B: HVAC integrated with an advanced multipurpose AWG.

In Configuration A, annual summer-period (May–September) energy use included 15,467 Sm³ methane for DHW and post-heating, and 40.4 MWh electricity for cooling. Configuration B eliminated methane use entirely by substituting AWG thermal output for DHW and post-heating, producing 257 m³ of purified water, and covering most cooling demand (317.4 MWh) with AWG output, leaving only 34.9 MWh to the existing chiller.

Results and Implications

• Energy Efficiency: Primary energy consumption dropped from 231.3 MWh (Configuration A) to 193.6 MWh (Configuration B), a 16.3% reduction. When factoring in PV cleaning gains from AWG water, consumption decreased to 101.9 MWh—a 55.9% saving.

• Water Production and Use: AWG-produced water met DHW needs and PV cleaning requirements, with surplus potentially supporting other hospital or district solar fields.

• System Integration Benefits: AWG integration enhances building resilience to water scarcity, reduces operational carbon footprint, and provides multipurpose energy services without increasing total system load.

Conclusion

This research demonstrates the feasibility and benefits of integrating advanced multipurpose AWGs into building-scale energy simulation tools, enabling optimized water–energy nexus designs. By embedding AWG models into tools like DesignBuilder, designers can assess the synergistic benefits of water production, heating, and cooling from a single system during the design phase. Such integration supports sustainable infrastructure development, especially in water-stressed or energy-intensive contexts such as hospitals.