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The way citizens perceive air quality has a huge impact on the public's willingness to contribute agendas that promote a sustainable future. Consequently, the scientific community wonders do the sudden and short-term shifts in air quality (such as one caused by the COVID-19 pandemic) have the potential to induce long-term changes in community behavior. This study is based on the interpretation and analysis of a facultative survey administered to the student population of a medium-sized university city in the Balkans. The study's goal is to identify the types and strengths of factors that influence students' perceptions of air quality. In this regard, six classification algorithms were compared in order to select the one with the best fit between students' demographics, traveling habits, and air quality perception. Individual variable influence revealed that Weekly lectures attendance and Distances students travel determine the perception of air quality more than Gender and Permanent place of residence. According to the study, potential commuting reorganization should target those living 2-4 km from the faculty building. Students who regularly attend lectures are likely to be willing to rely on better-organized public transport. Those who do not, will generally contribute the initiative once the positive effects are evident.

he paper proposes a methodology for defining the optimal solution for the integrated usage of cogeneration and rooftop photovoltaics. The purpose is to minimize CO₂ emissions in industrial plants. The methodology is founded on the integral use of energy audit techniques (analyzing energy and material flows in a production process and the dependence of electricity and heat consumption on a production volume) and mathematical optimization (linear programming). In accordance with the obtained consumption profiles, technical limitations, and legal regulations, the potential for installing rooftop photovoltaic (PV) panels at appropriate locations and the implementation of appropriate cogeneration technologies were analysed. The proposed methodology was tested on a local margarine production facility. The integrated application of cogeneration (gas engines) and photovoltaics can reduce the current CO₂ emission by 56% if PV panels are installed on the entire accessible rooftop surface, i.e. up to 44.5% if 150 kW PV panels are installed as the new national regulation proposes.

The current flat-plate solar collectors perform best when their absorbers rotate around their axis. However, with their concentrators, reflectors, and tracking mechanisms, they take up a lot of space and are thus commercially speaking, not the best solutions. This paper proposes a novel solar collector design which employs the (relative) rotation of absorbers, but strives to combine the benefits of fixed and (absolute) tracking solar systems, i.e. volume occupancy from the former and thermal performance from the latter. The findings of our numerical analysis show that, the solar irradiance efficiency of this novel design is 20% higher than that of a fixed flat-plate collector during clear-sky days, and it is equally lower than that of an absolute tracking collector. This paper also introduces a new criterion for describing single-axis tracking solar collectors which should be included in the classifications of solar collectors. Finally, the article, which represents a continuation of our research in the field of solar energy utilization, can contribute to the future development of solar technologies and solve some of the current challenges. [ABSTRACT FROM AUTHOR]

Educational buildings have a significant share in the total number of buildings of public sector. Also, significant part of energy consumption belongs to these buildings. There are 15 kindergartens that are under 2 preschool institutions. Their specific annual heat consumptions are from 79.42 kWh/m2 to 491.52 kWh/m2 (from 106.02 kWh/m2 to 325 kWh/m2 for objects connected to the district heating system). The average specific annual heat consumption is about 22% more than the consumption in neighboring countries. Most kindergarten buildings were built in the '70 and '80s of the last century and do not have adequate thermal insulation. Based on the defined methodology, specific annual heat consumption of these buildings has been analyzed, priorities for reconstruction have been defined and measures for improvement of energy efficiency have been proposed. Conducted case study of implementing the proposed measures at 'Ciciban' kindergarten showed that savings could be from 36% to 58% in heat consumption.

To improve solar collector efficiency, a variety of designs and materials have been introduced into production practice. Studies describing solar collector specifics, therefore, are particularly valuable to the scientific community as they contribute to the overall body of knowledge and constant improvement the in the scientific field. In that regard, the study presented in this paper analyses the thermal performance of the fixed flat-plate collector with an Sn-Al2O3 selective absorber. The fixed flat-plate collector design utilizes gravity water flow in an open loop system. A two-month study was conducted to perform the analysis. The experiment was based on measurements of water flow in the fixed flat-plate collector, the water temperature at the fixed flat-plate collector inlet and outlet, and solar radiation intensity on a horizontal surface. Results for three randomly selected measurement days have shown that fixed flat-plate collector can achieve relatively satisfactory values for average daily specific heat power, thermal efficiency, and inlet-outlet water temperature gradient, respectively: June 29 (381.78 W/m2, 60.67%, and 9.06 °C), June 30 (364.33 W/m2, 59.43%, and 7.46 °C), and July 15 (373.06 W/m2, 59.85%, and 8.69 °C). Apart from the relatively good measurement results, this type of solar collector does not require circulating pumps for operation, which brings a double advantage: energy saving and energy production. [ABSTRACT FROM AUTHOR]

The food industry uses a considerable amount of energy and that amount has been constantly growing with further developments in the sector. The growth of the milk processing industries with the production of dairy products has followed the trends in the food industry in general. The authors made a systematization of the literature data on the most common energy efficiency opportunities (measures) in diaries. Authors also present a methodology for conducting an energy audit in dairies based on ISO 50002 which includes a multi-criteria analysis for ranking energy efficiency opportunities. The proposed methodology was applied to a case study dairy in central Serbia. Taking into account interactions between opportunities, implementation of the proposed energy saving opportunities can ensure 11-15% energy savings for electricity and 20-23% of heat energy annually. [ABSTRACT FROM AUTHOR]

The use of renewable energy sources for electricity generation in the Western Balkan countries is analyzed in this review paper. Since those countries are part of EU or intend to be, data for Western Balkan are also compared with data for EU-28. The first part of the paper presents a brief overview of main promotion mechanism for electricity generation from renewable energy sources. As a dominant support policy, the feed-in tariff is more elaborated as an incentive measure and a detailed overview of the amount of tariffs and quotas for dominant technologies in the Western Balkan countries is presented. Furthermore, the current state of installed capacities and annual productions of three particular renewable electricity technologies (small hydro power, wind power, and solar photovoltaic) are analyzed in detailes. Based on presented data, there is a discussion and consideration of the impact of incentive measures on the electricity market and power production from renewable sources. [ABSTRACT FROM AUTHOR]