Photovoltaic (PV) panels experience significant efficiency degradation under elevated operating temperatures, making effective thermal regulation an important challenge for sustainable solar energy systems. Passive cooling techniques based on phase change materials (PCMs) have attracted considerable attention because of their latent heat storage capability; however, the low thermal conductivity of conventional paraffin-based PCMs restricts heat transfer performance during transient melting processes. This study investigates the thermal behavior of a PV cooling system employing paraffin enhanced with Ag–Al$_2$O$_3$–TiO$_2$ ternary nanoparticles and porous metal foam. A transient numerical model was developed using a Galerkin finite element approach combined with an adaptive mesh refinement technique to accurately capture the movement of the melting front and the associated thermal gradients. The thermal performance of the proposed cooling configuration was evaluated through temperature distribution, liquid fraction evolution, and PV electrical efficiency under transient operating conditions. The results showed that the incorporation of ternary nanoparticles and porous metal foam significantly enhanced heat diffusion and accelerated the melting process within the PCM domain. The liquid fraction increased by approximately 38.66% compared with the conventional PCM configuration, indicating more effective latent heat absorption and faster phase transition behavior. It was also found that the enhanced cooling system reduced the PV panel temperature by nearly 12.75% and improved the PV electrical efficiency by approximately 26.75% relative to the uncooled case. In addition, the incorporation of pure paraffin beneath the PV panel reduced the panel temperature by about 9.94%, confirming the effectiveness of latent heat storage for passive thermal regulation. The results indicate that the simultaneous utilization of ternary nano-enhanced PCM and porous metal foam provides an effective passive cooling strategy for PV thermal management. The proposed configuration offers improved thermal energy dissipation, enhanced phase change heat transfer characteristics, and promising potential for the development of high-performance solar energy systems.

Renewable Energy Communities (RECs) are increasingly recognized as decentralized energy systems capable of improving renewable energy integration, enhancing local self-consumption, and supporting the transition toward low-carbon energy infrastructures. However, the effective deployment of RECs still faces significant challenges related to the integration of spatial analysis, energy modelling, operational optimization, and socio-economic assessment within a unified framework. This study investigates an integrated multi-objective framework for the design, evaluation, and operational support of RECs through the combination of geospatial analysis, energy performance modelling, and digital decision-support tools developed within the ENEA Smart Energy Communities (SEC) platform. The proposed methodology was developed by integrating spatially explicit territorial datasets, renewable resource assessments, electricity demand profiles, and multidimensional key performance indicators (KPIs) within a coordinated analytical framework. Three complementary tools were implemented and evaluated: the geoCER geoportal for territorial-scale renewable energy planning and REC scenario modelling, the DHOMUS platform for residential load monitoring and self-consumption optimization, and the Local Token Economy (LTE) system for token-based user engagement and energy-aware behavioral incentives. The results showed that the integrated framework effectively supported the assessment of REC configurations under different territorial and operational conditions. In the Anguillara Sabazia case study, the REC configuration increased the Self-Consumption Index (SCI) from 30% to 65% and the Self-Sufficiency Index from 36% to 79%, while reducing the Energy Surplus Index from 70% to 35%. In the Sardinia case study, the scenario-based analysis demonstrated that renewable energy integration and coordinated energy sharing significantly improved territorial self-sufficiency under optimized REC configurations. The geospatial modelling approach also enabled the identification of suitable renewable deployment scenarios while considering environmental and territorial constraints. The results indicate that the integration of energy modelling, digital monitoring systems, and spatially explicit planning tools provides an effective pathway for improving the operational performance, flexibility, and scalability of RECs. The proposed framework offers practical support for decentralized energy planning, distributed renewable energy management, and data-driven decision-making processes in future community-based energy systems.

This study addresses the growing role of Renewable Energy Communities (RECs) in supporting decentralized renewable energy integration and improving local energy self-sufficiency within the European energy transition framework. The work aimed to evaluate the technical and economic feasibility of a municipal REC in Pattada, a small municipality located in Sardinia, Italy, through an energy balance analysis based on distributed photovoltaic generation and shared electricity consumption. A techno-economic assessment framework was developed by combining the estimated electricity production of municipally owned photovoltaic systems with the load profiles of municipal, commercial, and residential users participating in the REC. The photovoltaic energy production was estimated using the Photovoltaic Geographical Information System (PVGIS) simulation platform, while the shared energy within the REC was evaluated by considering the simultaneity between electricity generation and demand under different residential participation scenarios. The results showed that the municipal photovoltaic systems achieved an annual electricity production of approximately 506.41 MWh, while direct physical self-consumption remained limited to 3.10 MWh/year due to the mismatch between municipal demand and photovoltaic generation profiles. The analysis further showed that the REC reached an energy equilibrium condition with the participation of 285 residential users, corresponding to nearly 23% of the households within the municipality, allowing virtually shared energy to reach 425.92 MWh/year. The economic evaluation demonstrated that the municipal administration obtained the highest share of the overall economic return, mainly driven by electricity exported to the grid and incentive revenues associated with shared energy. The results indicate that the integration of municipally owned photovoltaic systems within REC configurations provides an effective approach for improving local energy sharing and enhancing the economic viability of distributed renewable energy systems in small municipalities. The proposed framework offers practical support for local administrations in planning renewable energy investments and optimizing REC configurations under real operating conditions.

Cold thermal energy storage systems are widely employed in refrigeration, food preservation, and thermal management applications; however, their performance is often constrained by the inherently low thermal conductivity of phase change materials (PCMs), which limits the rate of solidification. Improving heat transfer during the freezing process therefore remains a central issue in the design of efficient storage systems. The present work examines the solidification behavior within a cold energy storage unit featuring a non-conventional container geometry with an elliptical cooling wall. Two enhancement strategies are considered in combination: the dispersion of a ternary nanoparticle mixture (TiO₂–Ag–Al₂O₃) in the base fluid at a volume fraction of 0.015%, and the incorporation of a metal foam structure to promote conductive heat transfer. A transient numerical model is established using a Galerkin-based finite element approach with adaptive mesh refinement to accurately capture the evolution of the solid–liquid interface. The results indicate that the addition of ternary nanoparticles leads to a reduction in total freezing time of approximately 13.12%, while the introduction of metal foam yields a substantially greater reduction of 82.35%. When both techniques are applied simultaneously, the freezing time decreases by 84.66%, demonstrating a clear synergistic effect. A comparative analysis further shows that the influence of foam porosity on the advancement of the solidification front is approximately 6.27 times greater than that of nanoparticle concentration. These findings suggest that structural enhancement through porous media plays a dominant role in accelerating heat transfer, and that prioritizing internal thermal pathways offers a more effective design strategy than relying solely on modifications of fluid properties. The results provide a quantitative basis for the development of high-efficiency cold energy storage systems in engineering applications.

Controlled-environment agriculture has emerged as a promising approach for improving food security and climate resilience in semi-arid regions. Among recent innovations, Cadmium Telluride (CdTe) photovoltaic-integrated greenhouses offer the dual benefit of renewable energy generation and sufficient photosynthetically active radiation for crop growth. However, the thermal and microclimatic performance of ventilation systems in such greenhouses remains insufficiently investigated, particularly under sub-Saharan African conditions. In this study, a gable-roof CdTe photovoltaic-integrated greenhouse structure (3.6 m × 2.25 m × 2.0 m) was numerically analyzed using a validated three-dimensional Computational Fluid Dynamics (CFD) model developed in SolidWorks Flow Simulation. Three ventilation strategies—natural, mechanical, and hybrid ventilation—were evaluated for their effects on thermal regulation and airflow distribution. Natural ventilation employed top and side vents equivalent to 10% of the floor area, while mechanical ventilation used four 13 W fans providing 40 air changes per hour (ACH). The hybrid system combined natural and mechanical ventilation. A Design of Experiments (DoE) framework was further applied to evaluate interactions among airflow, temperature, humidity, and energy demand. Experimental validation using a full-scale prototype at Busitema University showed strong agreement between simulated and measured temperatures, with a Coefficient of Determination (R²) of 0.92, a Root Mean Square Error of 1.18 °C, and a Normalized Mean Bias Error of +1.3%. The hybrid ventilation system achieved the best performance, maintaining greenhouse temperatures within the optimal range of 21–27 °C. Furthermore, the greenhouse energy and water requirements were estimated, indicating that stable tomato production could be sustained using a heating capacity of 0.5 kW and a daily irrigation demand of 44 L for 24 tomato plants operated under six precision pulse-irrigation cycles per day. These findings demonstrate that CdTe photovoltaic-integrated greenhouses can effectively balance energy efficiency and crop productivity, thereby providing a scalable and sustainable framework for protected agriculture in developing countries and semi-arid environments.