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- Sustainable CO2 refrigeration system for fish cold storage facility using a renewable integrated system with solar, wind and tidal energy for Cape Verde: analyzing scenariosPublication . Garcia, João; Semedo, ArianThis study compares four feasible alternative solutions for an integrated cold storage system in the city of Tarrafal, Santiago, Cape Verde. Integrated systems using grid electricity are compared with autonomous systems generating electrical energy from renewable sources, alongside various types of refrigeration facility systems. Its objective is to assess the energy efficiency, financial feasibility, and environmental impact across four scenarios. Scenario 1 utilizes two R134a refrigeration units powered by the public grid. Scenario 2 employs a transcritical R744 (CO2) system using grid electricity. Scenario 3 incorporates R744 and autonomous renewable energy. Scenario 4 employs R744 for refrigeration with seawater heat exchange and autonomous renewable energy sources. The findings favor Scenario 4, emitting 15,882 kg CO2 eq with a 5-year return on investment. Autonomous electricity production in this scenario reduces emissions by 95%. Despite an initial cost of EUR 769,172.00, Scenario 3 demonstrates financial viability, contributing to energy sustainability. This autonomous production reduces emissions by 360,697 kg CO2 compared to conventional systems, highlighting the positive impact of local renewable energy integration.
- Heat transfer mechanisms in refrigerated spaces: a comparative study of experiments, CFD predictions and heat load software accuracyPublication . Lança, Miguel; Garcia, João Nuno Pinto Miranda; Gomes, JoãoA correct cold room heat load calculation ensures that the refrigeration system operates efficiently, reducing operating costs while maintaining a constant temperature to prevent stored goods from spoiling. Refrigeration engineers typically use software to size equipment such as expansion devices and evaporators and to estimate heat loads in cold rooms. These tools are available for free from refrigeration manufacturers or can be purchased from software developers. Although practical and easy to use, most of these programs do not follow the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE)-recommended approach for estimating heat loads. This article evaluates heat transfer mechanisms, especially natural convection in a refrigerator, through experimental and CFD simulations. Depending on the expression used, the estimated convection heat flux at the evaporator ranged from 5.3 W to 14.2 W in case 0-N, 7.7 W to 25.1 W in case −10-N, and 5.1 W to 22.4 W in case 0-Y. Compared to convective heat transfer, radiation heat flux estimations are often more consistent across different expressions. The results from validated simulations were used to assess the performance of cold room heat load estimation software. Differences of up to 236% in heat load estimates were reported between the results.
- A systematic review of numerical modelling approaches for cryogenic energy storage systemsPublication . Semedo, Arian; Garcia, João Nuno Pinto Miranda; Brito, MoisésCryogenic Energy Storage (CES) has emerged as a promising solution for large-scale and long-duration energy storage, offering high energy density, zero local emissions, and compatibility with intermittent renewable energy sources. This systematic review critically examines recent advances in the numerical modeling of CES systems, with the objective of identifying prevailing methodologies, emerging trends, and existing research gaps. The studies analyzed are classified into three main categories: global thermodynamic modeling, simulation of specific components, and transient dynamic modeling. The findings highlight the continued use of thermodynamic models due to their simplicity and computational efficiency, alongside a growing reliance on high-fidelity CFD and transient models for more realistic operational analyses. A clear trend is also observed toward hybrid approaches, which integrate deterministic modeling with machine learning techniques and response surface methodologies to enhance predictive accuracy and computational performance. Nevertheless, significant challenges persist, including the absence of multiscale integrative models, the scarcity of high-resolution experimental data under transient conditions, and the limited consideration of operational uncertainties and material degradation. It is concluded that the development of integrated numerical frameworks will be critical to advancing the technological maturity of CES systems and ensuring their robust deployment in real-world energy transition scenarios. Additionally, the review also discusses local thermal non-equilibrium (LTNE) conditions, the influence of geometric and operational parameters, and the role of multidimensional and multi-region modeling in predicting thermal and exergy performance of packed-bed TES within LAES cycles.
- Sustainable energy management in the cheese industry: a simulation model integrated with renewable energy sourcesPublication . Teixeira, Tiago; Monteiro, Joaquim; Garcia, João Nuno Pinto Miranda; Dias, João MestreCheesemaking is an energy-intensive process that relies heavily on heating and cooling operations traditionally powered by fossil fuels and electricity from the national grid. Reducing this dependence and integrating renewable energy sources are essential to align the sector with European decarbonization targets. This study presents the development of a simulation tool for optimizing the energy management of a cheese production facility by integrating solar, wind, and biomass systems. The model evaluates techno-economic and environmental performance under different climatic conditions and operational scenarios. Experimental validation was carried out using a prototype installed at the Polytechnic Institute of Beja (Portugal), achieving a deviation of only 2.3% in renewable energy contribution between simulated and measured data. Results demonstrate that renewable integration can reduce non-renewable energy consumption, achieving weekly profits up to 0.019 €/kg of cheese and carbon emissions as low as 0.0109 kg CO2e/kg. The proposed approach provides a reliable decision-support tool for small- and medium-scale cheese producers, promoting both environmental sustainability and economic competitiveness in rural regions.