Absorption refrigeration technology was developed as a response to major challenges, including the energy crisis, rising fuel costs, and the environmental drawbacks of conventional vapor-compression refrigeration systems. Extensive research has focused on developing strategies to enhance the COP of absorption systems, with the aim of making absorption refrigeration technology more competitive compared to conventional compression systems This study investigates a hybrid absorption heat pump integrated with heat recovery combined heating and cooling production to improve the COP of absorption refrigeration systems. The system is based on low- and high-pressure absorber/evaporator pairs, operating with H₂O/LiBr as the working fluid, and driven by a low-temperature heat source. In order to drive the heat pump’s heat generator, natural gas (prepared in a boiler) or/and solar energy (prepared in solar panels) was used. The experimental reasearch were conducted on an experimental stand located in the Department of Heat Engineering and Thermal Equipment Laboratory from the Technical University of Civil Engineering, Bucharest. It can simultaneously supply both cooling and heating for preparation of domestic hot water. A performance analysis is carried out through experimental measuring data to calculate the total COP vs. COP for conventional single-effect absorption chiller under the same conditions. In recovery mode, the maximum total COP increases to 5.446 because of heat recovery from condenser and absorber. Nevertheless, the system achieves a temperature of hot water between 33.58–43.92 °C. Notably, the recovery heat mode performance is strongly influenced by the solar radiation during the month, which therefore represents a key design parameter for the proposed system.

Keywords: heat pump, heat recovery, H2O absorbtion

Lucrarea prezintă studiul condițiilor de confort termic în spații publice, utilizând metoda Fanger și datele standardului ASHRAE. Se analizează influența principalilor parametri microclimatici – temperatura aerului, temperatura radiantă, viteza aerului, umiditatea relativă, nivelul de activitate și rezistența termică a îmbrăcămintei – asupra senzației de confort. Rezultatele arată că metoda Fanger permite o evaluare mai exactă a interacțiunii factorilor, în timp ce standardul ASHRAE oferă valori orientative rapide. Intervalul de confort termic pentru spațiile analizate este cuprins între 18–24 °C, în funcție de condițiile specifice.

Cuvinte Cheie: confort termic, clădiri publice, metoda Fanger, ASHRAE, microclimat, îmbrăcăminte

This paper presents study of thermal comfort calculations in public buildings, using Fanger’s method and ASHRAE standards. The influence of six main parameters – air temperature, radiant temperature, air velocity, relative humidity, metabolic rate, and clothing insulation – on human comfort sensation is analyzed. Results show that Fanger’s method provides a more accurate evaluation of parameter interaction, while ASHRAE offers simplified comfort ranges for practical design. The comfort zone for the analyzed cases ranges between 18–24 °C, depending on specific indoor conditions.

Keywords: thermal comfort, public buildings, Fanger’s method, ASHRAE, microclimate, clothing insulation.

Articolul prezintă o abordare originală a renovării eficiente energetic a clădirilor existente prin evaluarea materialelor termoizolante și a impactului acestora asupra consumului de energie și emisiilor de CO₂. Au fost analizate cinci scenarii de izolație folosind software de simulare, concentrându-se pe performanța de mediu și economică. Rezultatele evidențiază eficiența soluțiilor inovative și durabile, oferind ghiduri pentru optimizarea izolației termice conform Green Deal-ului European și cerințelor EPBD 2024.

Cuvinte Cheie: renovare eficientă energetic, izolație termică, emisii CO₂, clădiri existente, simulare, Green Deal European, EPBD 2024

This paper presents an original approach to energy-efficient renovation of existing buildings by evaluating thermal insulation materials and their impact on energy consumption and CO₂ emissions. Five insulation scenarios were analyzed using simulation software, focusing on both environmental and economic performance. The results highlight the effectiveness of innovative and sustainable solutions, providing guidelines for optimizing thermal insulation in line with the European Green Deal and EPBD 2024 requirements.

Keywords: energy-efficient renovation, thermal insulation, CO₂ emissions, existing buildings, simulation, European Green Deal, EPBD 2024

Lucrarea analizează comparativ două scenarii de incendiu simulate cu PyroSim, într-o hală de 7050 m² destinată depozitării vopselurilor. Primul scenariu nu include activarea sistemului de sprinklere ESFR, iar al doilea evaluează eficiența acestuia. Sunt urmăriți parametri precum rata de eliberare a căldurii și distribuția temperaturii. Rezultatele evidențiază o reducere considerabilă a temperaturii maxime (de la 970 °C la 135 °C) și a intensității incendiului, subliniind rolul esențial al sistemelor cu sprinklere în limitarea propagării, protejarea bunurilor și siguranța personalului.

Cuvinte Cheie: PyroSim, Fire Dynamics Simulator, sprinklere ESFR, incendiu, deposit

The paper presents a comparative analysis of two fire scenarios simulated using PyroSim, within a 7050 m² warehouse designated for paint storage. The first scenario excludes the activation of the ESFR sprinkler system, while the second evaluates its efficiency. Parameters such as heat release rate and temperature distribution are monitored. The results show a significant reduction in peak temperature (from 970 °C to 135 °C) and fire intensity, highlighting the essential role of sprinkler systems in limiting fire spread, protecting assets, and ensuring personnel safety.

Keywords: PyroSim, Fire Dynamics Simulator, ESFR sprinklers, fire, warehouse

Poluarea luminoasă este în creștere la scară globală, expunând circa 80% din populația lumii - și până la 99% în Europa și America de Nord - unor niveluri excesive de lumină artificială nocturnă. Suprafața și intensitatea iluminatului pe timp de noapte cresc cu cel puțin 10% anual, impulsionate de urbanizare, industrializare și dinamica demografică. Inițiativele orientate spre eficiență energetică și reducerea costurilor stimulează inovația tehnologică și schimbă comportamentele de consum, contribuind la limitarea emisiilor luminoase inutile. Se estimează că, anual, aproximativ 50 de miliarde USD sunt irosite pe energie pentru iluminat care se disipă în atmosferă, degradând peisajele nocturne și afectând o gamă largă de specii. Consecințele includ perturbarea somnului, dereglarea ritmurilor circadiene și a secreției de melatonină la oameni, precum și alterarea comportamentelor naturale ale faunei sălbatice, arborilor și insectelor. În pofida amprentei semnificative asupra sănătății, biodiversității și funcționării ecosistemelor, Uniunea Europeană nu dispune încă de un cadru normativ coerent și unitar pentru gestionarea poluării luminoase. Sunt necesare strategii integrate care să reducă impactul ecologic al iluminatului menținând, în același timp, siguranța și funcționalitatea spațiului urban.

Cuvinte Cheie: poluare luminoasă; eficiență energetică; sănătate umană; biodiversitate; politici publice

Light pollution is intensifying globally, affecting around 80% of the world's population, a figure that rises to 99% in Europe and North America. The use of artificial light at night increases annually by at least 10% due to urbanization, industrialization, and population growth. Efforts to enhance energy efficiency and reduce energy costs are leading to technological advancements and changes in consumer behavior that help mitigate light pollution. Annually, about $50 billion is spent on energy for lighting that ultimately leaks into space, impacting nocturnal environments and various species. This pollution disrupts human sleep, circadian rhythms, and melatonin production, and alters the natural behaviors of wildlife, trees, and insects. Despite its extensive impact on health, biodiversity, and ecosystems, a unified legal framework to regulate light pollution is lacking in the EU. Effective strategies to minimize ecological impacts while maintaining city illumination are crucial.

Keywords: light pollution, energy efficiency, human health

articolul, intitulat „Modelarea și simularea integrată a sistemelor de energie pentru clădiri inteligente”, urmărește obținerea de rezultate relevante privind consumurile de energie într-o clădire inteligentă și compararea acestora cu cele ale unei clădiri mai puțin inteligente, dar cu același regim funcțional. Analiza comparativă a diferitelor modele evidențiază impactul fiecărei măsuri de transformare inteligentă. Prin simulări în DesignBuilder, studiul reconfirmă eficiența soluțiilor inteligente de control pentru sistemele energetice din clădiri. Rezultatele oferă valoare practică în optimizarea consumurilor, reducerea costurilor și sprijinirea deciziilor de proiectare sustenabilă.

Cuvinte Cheie: cuvinte reprezentative pentru articol

This paper, entitled “Integrated Modeling and Simulation of Energy Systems for Smart Buildings”, aims to obtain relevant results regarding energy consumption in a smart building and compare them with those of a less intelligent building with the same functional regime. A comparative analysis of different building models highlights the impact of each smart transformation measure. Using DesignBuilder simulations, the study confirms the efficiency of intelligent control solutions for building energy systems. The results provide practical value for optimizing energy consumption, reducing costs, and supporting sustainable design decisions.

Keywords: smart buildings, energy systems, simulation, DesignBuilder, energy efficiency

Aprovizionarea cu gaze naturale a 11 786 clienți cu consumul anual 16 523,3 mil m3 din 12 localități a Zonei de securitate a Republicii Moldova, racordate la sistemul de transport și distribuție din regiunea Transnistreană este supusă unui risc sporit datorită lipsei unei politici clare de acoperire de către consumatorii din regiune a costurilor suportate de furnizori. De menționat, că consumatorii din regiunea Transnistreană plătesc pentru gaze doar circa 11,4% din costul real al gazelor naturale furnizate. După criza din ianuarie 2025 costurile gazelor furnizate pentru regiunea transnistreană sunt suportate printr-un împrumut acordat de Federația Rusă în tranșe, la fiecare 10 zile, alocarea căruia periodic se reține, fapt care condiționează secționarea sistemului de transport din regiune de sistemul operatorului licențiat. În plus, nu există o claritate a durabilității acestei finanțări în perspectiva.

Cuvinte Cheie: consumatori, sustenabilitate, zona de securitate, regiunea Transnistreană, risc.

Natural gas supply to 11 786 customers with an consumption of 16 523,3 million m3 per year from 12 localities of the Security Zone of the Republic of Moldova, connected to the transmission and distribution system of Transnistrian region, is subject to increased risk due to the lack of a clear policy of covering the costs by consumers in the region of the costs incurred by suppliers. It is worth noting that consumers in Transnistrian region pay for gas only about 11.4% of the real cost of the natural gas supplied. After the crisis of January 2025, the costs of gas supplied to the Transnistrian region are covered by a loan granted by the Russian Federation in tranches, every 10 days, the allocation of which is periodically withheld, which conditions the sectioning of the region's transmission system from the licensed operator's system. In addition, there is no clarity on the sustainability of this particular financing of the gas supplies in the future.

Keywords: consumers, sustainability, security zone, Transnistrian region, risk.

This paper investigates the potential for improving the energy efficiency of electric boilers through the implementation of two innovative solutions. The first involves replacing the conventional electric resistance, typically immersed in water, with a mesh of carbon fiber conductors installed tangentially on the boiler shell, beneath the thermal insulation. This system operates similarly to a heating blanket, uniformly covering the boiler surface and providing a significantly larger contact area compared to traditional heating elements. Subsequently, phase change materials (PCMs) are integrated inside the boiler, with the role of storing thermal energy during the heating process and gradually releasing it during hot water consumption periods, thereby enhancing thermal performance. The study includes a detailed monitoring of the thermal behavior by installing temperature sensors at key points to analyze thermal stratification and energy efficiency. Comparative tests were conducted for three configurations: a standard boiler, a boiler with a carbon fiber conductor, and a boiler equipped with both the carbon fiber conductor and phase change materials.

Keywords: Carbon Fiber Conductor, Electric Boiler, Phase Change Materials

This paper presents an innovative digital twin solution for thermal manikins used to evaluate indoor environmental quality in buildings. While digital twin technology is gaining traction across industrial sectors, its adoption in building sector remains limited due to the industry's slow integration of innovative technologies. The research addresses the need for more accessible tools to analyze thermal comfort, which is often treated superficially in building design phases despite its fundamental importance for occupant well-being and energy efficiency. Traditional approaches rely on costly physical testing or simplified models that fail to capture complex human-building thermal interactions, leading to suboptimal designs and post-occupancy comfort issues. The proposed solution consists of a MATLAB application that provides an intuitive interface for monitoring thermal comfort parameters and real-time visualization of thermophysiological models applied to thermal manikins. A key innovation is the bidirectional data integration with ANSYS Fluent solver, enabling real-time simulations using data extracted from physical thermal manikin and vice versa. This work contributes to understanding and implementing digital twin concepts in thermal comfort evaluation, offering an innovative technological platform that balances occupant comfort with energy efficiency while providing a foundation for future research in this evolving field.

Keywords: Terms-Energy efficiency, Indoor environmental quality, Manikin Digital Twin, Thermal comfort.

Photovoltaic (PV) technology is a key renewable energy source; however, its performance is significantly hindered by overheating, which reduces efficiency and output. This study investigates passive cooling solutions for PV panels, with a focus on heat pipe integration. The research builds upon previous simulation-based work by extending experiments to real outdoor operating conditions, enabling a more accurate assessment of thermal and electrical behavior. Two types of heat pipes-narrow copper water-based pipes and flat aluminum acetone-based pipes—were integrated into aluminum transfer plates and tested against a conventional PV panel. Measurements were conducted over multiple days under comparable irradiance and ambient conditions, with performance indicators including panel surface temperature and electrical output. Results demonstrate that while the conventional PV panel reached average temperatures of 46.31 °C and produced 38.65 W, the narrow heat pipe–cooled module reduced the temperature to 44.28 °C and delivered 43.32 W. The flat heat pipe–cooled module achieved the best performance, lowering the temperature to 41.20 °C and increasing power output to 55.45 W. These findings confirm that passive heat pipe cooling is a practical and efficient method to mitigate PV panel overheating, significantly improving energy output and long-term system reliability.

Keywords: Energy efficiency, Heat pipes, Passive cooling, Photovoltaic Panels

The study presents a closed-loop sustainable farm concept that combines photovoltaic energy generation, livestock farming, greenhouse horticulture, and grain agriculture in a year-round, autonomous production model. The system was designed to minimize external inputs and environmental impact while maximizing the efficiency of internal resources. The farm model illustrates how agriculture could transition to a more efficient and self-sustaining system, aligned with the European Union's vision of a greener, climate-resilient future. Furthermore, the model will generate constant capital inflows, promoting a stable and predictable economic environment.

Keywords: circular economy, closed-loop system, renewable energy, sustainable agriculture.

The Thermal Response Test – abbreviated as TRT – is a standardized procedure for geothermal heat pump systems with closed-loop heat exchangers. The test enables the determination of key physical properties of the ground – thermal conductivity and borehole thermal resistance – which are essential for the correct sizing of the ground heat exchanger system, ensuring it meets the requirements of the building’s HVAC system. Additionally, the TRT provides valuable information regarding the technical and financial effort required for the drilling operation.

Keywords: Thermal Response Test, TRT, geothermal heat pumps, ground heat exchangers