PCM application in light construction buildings in various climates

Incorporating phase change materials (PCM) into building structures as passive latent heat thermal energy storage technologies offers a potential solution for reducing energy demand and regulating thermal comfort in occupied buildings. Integrating PCM into lightweight walls can improve their thermal performance by increasing building heat capacity and decreasing energy consumption. The effects of phase change materials (PCMs) added to the thermal envelope of lightweight residential containers on building thermal comfort are investigated in this study. The simulations were run for the summer period because it is difficult to achieve thermal comfort without using a lot of energy at that time. Thermal comfort is highly dependent on both, climatic conditions and the materials used to construct the building's thermal envelope, and the simulation was performed for weather conditions in five different geographic locations using TRNSYS simulation software. The paper examines the effects of PCM on indoor air temperature, specifically on reduction of maximum air temperature and temperature fluctuationsXII Međunarodna konferencija o društvenom i tehnološkom razvoju, Trebinje, 15-18. juni 2023

Impact of lockdown on air quality in Belgrade during COVID-19 pandemic

The Environmental Protection Agency of the Republic of Serbia continuously monitors and collects air quality parameters at numerous measuring points throughout the country. The results revealed that the levels of air pollution recorded during the lockdown differed from those recorded during the same period the previous years. In this paper, we examined pollutant concentration trends in 2020 and a few previous years to determine the underlying causes of these trends. Pollutants are measured at five stations in Belgrade from the beginning of March to the end of July between 2015 and 2020. Because no hourly data were available, NO2, SO2, and suspended particles PM10 and PM2.5 are average daily values, whereas CO and ozone are daily 8-hour maximums. Concentrations were compared and averaged only when data for the same period over time was available, i.e. when comparing 2020 to previous years. The results were compared to the annual and daily limit values (for ozone and CO 8 hours maximum, respectively), as well as the variations in concentrations over time. The goal of calculating and displaying these values is to specifically identify a change in air pollution during the COVID-19 virus pandemic isolation period. In general, for Belgrade in 2020, NO2 concentrations are lower at four stations, PM2.5 concentrations are lower at two stations, PM10 concentrations are higher at one station and lower at another, and SO2 concentrations are higher than in previous years (2015-2019)

Recent advancements of solar dryers with implemented phase change materials

Using solar energy for drying agricultural products is one of the oldest methods of preserving food. Excellent results are obtained by using solar dryers, both in the quality of dried products and in energy-efficient drying procedures. The problem occurs when the solar radiation is low intensity or absent, which makes it impossible for the solar dryer to work. This problem can be solved by implementing phase change materials (PCM) which improve the efficiency of the system and allow the dryer to work in a period during off sunshine hours. This review provides insight into the progress in the field of solar dryers in which PCM is implemented. The impact of using PCM on the quality and efficiency of product drying compared to solar dryers without PCM and open sun drying is shown. It has been noticed that the use of PCM improves the global thermal efficiency of the system. The temperature and the percentage weight of moisture removal was increased and the drying time of the product was reduced. Various cases of drying apples, tomatoes, basil, bitter melons, strawberries and medicinal herbs have been considered. Different positions of PCM in flat solar collectors increased the thermal efficiency of the flat plate collector in the range from 5.02% to 10.13%, and the overall efficiency varied from 21.92% to 25.72%. The use of hybrid systems consisting of two or more synchronized systems also have been considered. The hybrid solar dryer with implemented PCM and integrated geothermal system showed an improvement in performance efficiency of 20.5% compared to a flat plate solar collector. The progress of solar dryers with the implementation of PCM is given with the aim of further developing the application of renewable energy sources in food preservation.ISAE 2021 : 5th international symposium on agricultural engineering : proceedings; September 30th - October 2nd, 2021; Belgrade, Serbi

Influence of the building energy efficiency on indoor air temperature: The case of a typical school classroom in Serbia

Greenhouse gases emission as well as total energy consumption in buildings of public importance, such as schools, municipal buildings, health care centers, can be significantly reduced by increasing buildings’ energy efficiency. Buildings’ energy consumption adds up to 37% of total energy consumption in the EU countries. In the Republic of Serbia this amount is significantly higher, about 50%. School buildings are considered as one of the most diverse structures from the point of energy-efficient design and construction. The main aim of this paper is to determine the most appropriate settings for possible improvements in energy efficiency and temperature comfort inside a typical primary school classroom in Serbia. The energy efficiency analysis was performed during the heating season for the naturally ventilated primary school classroom located in the eastern Serbia region. The analysis was performed using novel CFD model, suggested in this paper. The suggested model was used to solve two hypothetical scenarios. The first scenario simulates the temperature field in classroom with current energy characteristic envelope of the school building. The calculated numerical data from the first scenario were compared with in-situ measurements values of temperature and wall heat fluxes and showed satisfying accuracy. The second scenario was simulated to indicate possible improvements, which would allow energy consumption decrease and thermal quality enhancement. The analyzed results, calculated using the suggested numerical model under the second scenario conditions, showed that using appropriate set of measures, it is possible to obtain desired temperature comfort levels without need for increase in the building energy consumption

Numerical simulation of fire spread in terminal 2 of Belgrade airport

This paper concern the results of software fire spread process prototype in terminal 2 of Belgrade airport using computational fluid dynamics. Numerical simulation of fire for the most critical fire scenario has been performed, primarily obtaining the space and time distribution of: velocity, pressure, temperature, and smoke concentration, assuming that HVAC systems have been switched off and all doors on the evacuation ways have been opened, just as the fire started Also, two simulations have been compared of the smoke ventilation and not ventilation for the same scenario. Within the framework of the results presentation, isosurfaces of constant temperature (100 degrees C) and smoke concentration (4000 ppm) are presented, based on the numerical simulation. Progression of these surfaces along the terminal 2 coincides to the experimental and experience evidence, forming the plume zone just above the fireplace, and spreading in the zone of underground ceiling and stairwell openings

The possibility of using polymer-based phase change materials for thermal energy storage

Phase change materials (PCM) are attractive energy storage technologies due to their high energy storage density and the ability to reversible absorb and release thermal energy at a nearly constant temperature. Polymers and polymer-based eutectic mixtures are promising PCMs. This study aims to investigate heat properties (melting temperature (Tm), latent heat (ΔH) and thermal conductivity(λ)) of potential PCMs based on polyethylene glycol polymer (PEG2000). We prepared following two and three components materials: PEG2000: ethylene glycol (5:6): PEG2000: PPG 400 (1:5); PEG2000: PPG400: Choline chloride (2:2:15); PEG2000: ethylene glycol (5:6); PEG2000: Glyoxal (5:2). The prepared three components material belong to deep eutectic solvents. Tm of the prepared materials are lower compared to pure PEG2000 (Tm = 57 ºC) e.g. Tm of PEG2000: PPG400: Choline chloride is 43 ºC. The determined melting enthalpies are also lower for prepared materials compared to PEG2000. This decrease is lower for eutectic mixture such as PEG2000: Choline chloride: ethylene glycol. We can conclude based on the obtained result that eutectic mixtures based on polymers are promising PCMs.XII Međunarodna konferencija o društvenom i tehnološkom razvoju, Trebinje, 15-18. juni 2023

The effect of phase-changing material thickness on light construction building indoor temperature

Due to the excessive use of air conditioners and heating systems, energy consumption by the builiding sector has been growing significantly in recent years, which leads to the accelerated depletion of conventional energy sources and to the fact that renewable energy sources are becoming more and more popular. Phase change materials are suitable for use in latent heat energy storage technology due to their high storage density and stable thermal properties. The thickness of phase change materials (PCMs) added to the thermal envelope of a lightweight building is investigated in this study. The simulations were run for 7 days in July, which was determined to be the hottest period of the summer based on the Meteonorm weather file, and when it is difficult to maintain thermal comfort without using a lot of energy. The thermal behavior of the building without PCM and with builtin PCM in the envelope of the building in one wall on the south side and on the ceiling, with different thicknesses of phase-changing material was simulated and the results obtained were analyzed with the aim of establishing which thickness of phase-changing material is optimal for installation in the envelope of the buildingThe 6th International Symposiumon Agricultural Engineering; Oct 19-21, Belgrade, 2023

Analysis of different scenarios and sustainability measurement in the district heating sector in Serbia

The district heating system in Serbia, with an installed capacity of 6,600 MW, currently supplies 58 towns with thermal energy. As a candidate country for accession to the European Union, Serbia faces the obligation to reduce the level of its greenhouse gas emissions as part of environmental reforms. This paper presents a basic scenario and three alternatives for final energy consumption in the district heating sector for the years 2015, 2020 and 2025. It is suggested that demand for heating will increase 10% up to 2020 and by 15% up to2025, in relation to 2015 levels, while the share of each energy carrier will not change. Changing the structure of energy sources for heat supply assumes a decrease in the share of coal and liquid fuel, and increases in the use of biomass and natural gas. The results obtained were compared to the General Index of Sustainability which is a measure of the complexity of the proposed energy scenario. The paper considers the formation of related energy indicators as quantitative tools for the analysis of changes. It also proposes a methodology for multi-criteria analysis in the sustainability assessment of complex energy systems based on the stochastic evaluation of criteria (sets of indicators and sub-indicators). In this way, the results of the multi-criteria assessment can help in the decision-making process in cases where economic, social and ecological criteria are considered to be influential. © 2018 Serbian Society of Heat Transfer Engineers

Experimental and Numerical Modelling of Thermal Performance of a Residential Building in Belgrade

The main objective of this paper is to evaluate simulation of thermal performance of a residential 4 floors high building placed in the suburb of Belgrade (ground and 3 upper floors) with its total surface area of 1410 m(2). Its supplied with liquid petroleum gas storage lank as a fuel reservoir since there is automatic gas boiler in each apartment. Measurements have been carried out in first floor apartment (68 m(2) heating area) in heating season period Measured parameters are: inside and outside air temperature and U-value of apartment envelope. Weather data is obtained by using METEONORM, the software package for climatic data calculation based on last 10 years measurements. TRNSYS 16 has been used as the simulation tool. The behavior of the building in terms of heating loads for climate on a daily and monthly basis in heating season is investigated The calculations show possibility for saving energy by optimization inside temperature during different gas boiler working regimes