Operation of the water-energy and food nexus in a greenhouse hydroponic cultivation unit and technical solutions for the self-sufficiency of the system

This thesis examines the operation of the Water–Energy–Food (WEF) Nexus within a hydroponic greenhouse facility, focusing on technical strategies aimed at enhancing the system's self-sufficiency and reducing dependency on external inputs. The WEF Nexus is adopted as a conceptual and analytical framework that highlights the interdependence of water, energy, and food systems, and serves as a decision-making tool for integrated resource management. The study is based on real-world data collected from the “Markatos Hydroponics” unit located in Inofyta, Viotia. The facility's daily consumption of water, electricity, and nutrient inputs is analyzed alongside crop production data. Technical solutions are proposed and evaluated, including the installation of photovoltaic panels integrated into the greenhouse structure, geothermal heating and cooling systems, biogas generation, and combined heat and power (CHP) units. These interventions are tested through simulation models that explore energy autonomy scenarios over a full year of continuous operation. Hydroponic cultivation is examined both as a production system and as a resource-efficient method suitable for non-conventional or urban spaces. The method offers significant advantages, such as up to 90% water savings and 10-fold increase in productivity per unit area compared to conventional agriculture. Furthermore, the study explores the role of smart technologies (e.g., sensors, automated control, and monitoring software) in optimizing system efficiency and responsiveness. The results indicate that when a hydroponic greenhouse is designed following the WEF Nexus approach, it can achieve up to 90% energy autonomy and reduce external water needs by 25– 35%. The integration of renewable energy systems and closed-loop solutions strengthens the operational resilience of the facility. This thesis concludes that such infrastructures represent viable, efficient food production models with high applicability in both rural and urban contexts.