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Educational buildings represent an indivisible part of every society, and it is necessary to make them energy efficient. In the current research on the energy-efficient retrofit of school buildings...

In this paper, we propose the system for AI-assisted control of District Heating Systems (DHS) for efficient distribution of heat to residential and commercial buildings in urban areas. Currently, DHS operation is controlled semi-automatically by SCADA systems, where the operation decisions are made by the DHS plant operator. Operation is considered reactive as control decisions are made based on the real-time meteorological data. This proposal is aiming at facilitating proactive DHS control, by using predictive modelling techniques based on modern Artificial Intelligence (AI) architectures, namely the Deep Learning (DL)-based multivariate time-series forecasting. The initial results of forecasting heat demand and local explanations are provided for the case of small 8MW DHS, as a proof of concept.

The existing public buildings in Serbia provide many opportunities for energy-efficient improvements and energy savings. Based on a computer simulation using the SketchUp and EnergyPlus software packages, the energy consumption of existing primary schools in Nis, Serbia. The parametric study included interventions on the building envelope (thermal insulation, glazing characteristics), as well as using of Trombe wall (TW), double skin facade (DSF), and green roof (GR), Blinds (BL) as a representative of passive design (PD) strategies. This study aims to determine the most favorable combination of proposed interventions as a strategy for improving the energy efficiency of existing school buildings. Outputs from the analysis are evaluated to find out which measures are the best for heating and cooling energy savings during the whole school year. Based on the obtained results, the study proposes the combination of alternatives that yielded the highest and lowest energy savings for heating and cooling.

Modern society and economic development are completely dependent on various forms of energy while the ever-increasing demand for energy, in combination with significant environmental topics, has resulted in state-of-the-art ideas and solutions for fulfilling these often-contradictory goals, i.e. increasing efficiency or environmental protection and economic goal. The efficiency of the existing operating units for electricity production based on the usage of low-quality coal does not go hand in hand with the requirements of this new concept.One of the most efficient ways to reduce specific energy consumption is using Combined Heat and Power plants. In comparison to classical, separate heat and power plants, the advantage for CHP plants comes from their high efficiency. The result of higher efficiency is lower primary energy consumption and lower environmental pollution due to low values of CO2 emissions.Several revitalization configurations can be applied in order to fit the existing thermal power plants into combined cycles. The idea is to install, at the existing location, one gas turbine to increase the overall efficiency. This paper analyzes the potential of a combined gas-steam facility in the situation where the gas facility is used for heating feed water, which enters the heat recovery steam generator.A comparison of energy efficiency for various operating regimes, with and without heat production, is performed for this option.

Energy consumption has reached its highest level globally. Buildings have the largest share in total energy consumption, so designers must take into account their functioning and the consequences that can arise. Passive solar design is an imperative in modern architecture, and Trombe wall, as one of the principles of this design, is certainly distinguished. The paper presents an overview of the characteristics of the construction of the Trombe Wall in order to improve thermal stability and reduce energy consumption in buildings. Starting from the consideration of climatic influencing factors, through the heat capacity of the materials applied and their thickness and color of the thermal mass, it is very important to know in detail all the factors that can lead to the improvement of the efficiency of this system. The specific heat of the walls in the building, the time delay, the decrement factor and the influence and position of the thermal insulation were also taken into account. The effect of glazing as well as the influence of the ventilation openings were highlighted as significant elements. On the basis of the analysis of the above components, the conclusions and guidelines for designing this type of constructions were made in order to improve the efficiency and reduced energy consumption while providing adequate comfort in the facility.

Relying on coal as primary fuel in thermal power plants represents an unsustainable concept due to limited coal reserves and a negative environmental impact. Efficient utilization of coal reserves and a request for minimization of irreversibilities are imperative for thermal power plants operation. Numerous studies have shown that a steam boiler is a thermal power plant component with the highest irreversibility. The idea of this paper is to quantify the amounts and sources of irreversibilities within a steam boiler and its components, serving a 348.5MWe thermal power plant. Having this in mind, exergy and exergoeconomic analysis of a steam boiler is presented in this paper. Exergy destruction and exergy efficiency of all boiler components and of the boiler as a whole were calculated. Based on exergy flows and economic parameters (cost of the boiler, annual operation hours of the unit, maintenance factor, interest rate, operating period of the boiler), exergy analysis resulted in the cost of produced steam. The obtained results show that the boiler exergy efficiency is at 47.4%, with the largest exergy destruction occurring in the combustion chamber with a value of 288.07 MW (60.04%), and the smallest in the air heater with a value of 4.57 MW (0.95%). The cost of produced steam is calculated at 49,356.7 $/h by applying exergoeconomic analysis.

Jedinice lokalne samouprave u Republici Hrvatskoj u vlasništvu imaju velik broj različitih oblika imovine. Nekretnine su najvredniji oblik u portfelju nefinancijske imovine. To je vrsta imovine s najvećom vrijednošću kojom raspolažu i upravljaju gradovi. Navedene vrste nekretnina posredno su vlasništvo svih građana, zbog čega je bitno osigurati njihovo učinkovito upravljanje. Ovaj rad pokazuje kako su nekretnine slabo korišten izvor financiranja gradova, što se odražava i na pokazatelj povrata koji gradovi ostvaruju na temelju nekretnina u svojem vlasništvu. Također, u radu se panel-regresijom empirijski istražuju odrednice povrata na nekretnine u hrvatskim gradovima od 2005. do 2017., s posebnim naglaskom na kvalitetu gradske uprave kao važne odrednice iskorištenosti nekretnina. Zbog nedostatka kredibilnih i javno dostupnih indikatora o kvaliteti gradskih uprava, u ovom se radu kao proxy varijablom za kvalitetu gradske uprave koristi broj poduzetnika po stanovniku. Takav se pristup temelji na Tieboutovu modelu glasanja nogama., Local self-government units in the Republic of Croatia own a large number of different types of property. Real estate represents the most valuable form of income in the non-financial property portfolio. It is considered property of the highest value, which is disposed of and managed by the cities. Such real estate is the indirect ownership of all citizens, making the insurance of its effective management important. This paper shows the poor use of real estate as a city’s source of financing, reflected in the indicator of return which the cities realise on the basis of the real estate in their ownership. Using panel regression, the paper empirically explores the indicators of return on real estate in Croatian cities in the period between 2005 and 2017, with particular emphasis on the quality of city administration as an important indicator of the utilisation of real estate. Due to the lack of credible and publicly available indicators on the quality of the cities’ administration, this paper uses the number of entrepreneurs per capita as a proxy variable for the quality of the cities’ administration. This approach is based on the Tiebout model of foot voting.

Primary energy is the quantity often used to express the total amount of consumed or saved energy. It is especially important for certification and standards compliance evaluation of buildings. In order to accurately assess primary energy consumption and savings of building retrofit measures, one needs adequate models that can be based on the knowledge of phenomena, on the collected data, or both. This paper analyzes the learning performance and accuracy of data-driven models based on decision trees that predict primary energy savings related to building retrofit measures. It uses supervised machine learning methods — regression decision trees and ensemble methods based on them — to train, validate, and test such models. Ensemble methods based on decision trees are powerful, accurate, but also convenient to prepare and fast to train. In addition, they calculate the relative importance of each feature. The research results with highly accurate data-driven models and consistent feature importance values.

In a time of permanent care for environmental protection, energy consumption and conservation of resources, heat pumps are becoming increasingly important as a technology for reducing greenhouse gas emissions while preservation thermal comfort in build environment. This paper presents the experimental results of air-source heat pump in different real operating conditions, as follows: for space heating by low-temperature underfloor heating when the supply water temperature was set at 38°C, or for domestic hot water heating in the storage tank volume of 180 liters at a temperature of 46°C. In the low-temperature underfloor heating mode, the efficiency of the air-source heat pump could be increased if the maximum temperature at the end of the compression process and the condensing temperature were reduced in the initial phase of the heat pump operation. In the domestic hot water heating mode, the efficiency of the air-source heat pump could be increased if the maximum condensation temperature in the final phase of the heat pump operation was limited.

One of the possible ways to improve balance between building energy consumption and occupant thermal comfort in existing buildings is to use simulation-assisted operation of HVAC systems. Simulation-assisted operation can be formulated as a type of operation that implements knowledge of future disturbance acting on the building and that enables operating the systems in such a way to fulfill given goals, which in nature can often be contradictory. The most important future conditions on building energy consumption are weather parameters and occupant behavior and expectations of thermal environment. In order to achieve this type of operation, optimization methods must be applied. Methodology to create HVAC system operation strategies on a daily basis is presented. Methodology is based on using building energy performance simulation software EnergyPlus, available weather data, global sensitivity analysis, and custom developed software with particle swarm optimization method applied over the moving horizon. Global sensitivity analysis is used in order to reduce number of independent variables for the optimization process. The methodology is applied to office part of real combined-type building located in Niš, Serbia. Use of sensitivity analysis shows that the reduced number of independent variables for the optimization would lead to similar thermal comfort and energy consumption, with significant computer runtime reduction.

This paper presents a way to generate bin weather data for regions where hourly meteorogical data are being collected in order to provide necessary weather input database for estimation of energy consumption for heating and cooling of buildings. Using weather records for sufficient period of time, preferably more than 5 years, bin weather data raging from minimum to maximum values of outdoor dry bulb temperature recorded in the location should be calculated with finite temperature increments in adequate number of daily shifts. For the purpose of obtaining sensible energy consumption, hourly measurements of dry bulb temperature are necessary, but in order to take into account latent energy consumption hourly values of relative humidity and the atmospheric pressure are needed as well. The derived results should be in form suitable for building energy analysis using basic or modified bin method.

Buildings use a significant amount of primary energy and largely contribute to greenhouse gases emission. Cost optimality and cost effectiveness, including cost-optimal operation, are important for the adoption of energy efficient and environmentally friendly technologies. The long-term assessment of buildings-related greenhouse gases emission might take into account cost-optimal operation of their energy systems. This is often not the case in the literature. Long-term operation optimization problems are often of large scale and computationally intensive and time consuming. This paper formulates a bottom-up methodology relying on an efficient, but precise operation optimization approach, applicable to long-term problems and use with buildings simulations. We suggest moving-horizon short-term optimization to determine near-optimal operation modes and show that this approach, applied to flexible energy systems without seasonal storage, have satisfactory efficiency and accuracy compared with solving problem for an entire year. We also confirm it as a valuable pre-solve technique. Approach applicability and the importance of energy systems optimization are illustrated with a case study considering buildings envelope improvements and cogeneration and heat storage implementation in an urban residential settlement. EnergyPlus is used for buildings simulations while mixed integer linear programming optimization problems are constructed and solved using the custom-built software and the branch-and-cut solver Gurobi Optimizer.

U saborskoj proceduri nalazi se prijedlog Zakona o Sredisnjem registru državne imovine ciji su glavni ciljevi uspostava evidencija i ucinkovitog upravljanja imovinom RH. U posljednjih pet godina vec je bilo vise institucija i verzija registara s istim ciljevima, pa se opravdano postavlja pitanje može li i ovaj novi Zakon (Registar) osigurati ispunjenje tih ciljeva.

A proposal for an Act on a Central Registry of State Assets is currently under parliamentary procedure, with the aim of establishing the records and ensuring effective management of the property of the Republic of Croatia (RC). Over the last five years, several versions of the registry have been developed and a number of institutions set up with the same goals, so that a reasonable question is whether the new act, i.e. the Registry, can ensure that those goals are met.

This study presents the results of the actual thermal behaviour of a multi-storey naturally ventilated double skin facade. Governed by lack of experimentally measured data, a field of detailed measurements were performed during the 2013/2014 season in the office building located in Belgrade, Serbia. The uniqueness of this building is that the first facade layer is made in the tradition manner. Apart from studying classical environmentally influenced air cavity behaviour, the methodology incorporates a detailed analysis of the air cavity enthalpy flow. The main purpose of this research is to examine the current state of the building facade and how it affects energy performance. To this effect, measurement data was used in order to analyse transmission losses and gains and to quantify enthalpy change of the cavity air linked to the airflow established within the facade. Analyse of the transmission losses and gains were described by a series of diagrams of vertical and horizontal temperatures trends for selected typical days in each regime. For investigation of the natural ventilation potential, an adequate indicator based on the enthalpy change was established. Overall, the experiment results highlight that the use of a double skin facade does not necessarily reduce energy consumption.

One of the possible ways to provide heating to the building is to use thermally activated building systems. This type of heating, besides providing significant increase in building energy efficiency, allows using low-temperature heating sources. In this paper, special attention is given to opaque part of the building fa?ade with integrated thermally activated building systems. Due to fact that this type of system strongly depends on temperature of this construction-thermal element and type and thickness of other materials of the fa?ade, influence of these parameters on energy efficiency was analyzed in this paper. Since the simplest and most promising way of using geothermal energy is to use it directly, for our analysis this source of energy was selected. Building energy needs for heating were obtained for real residential multi-family building in Serbia by using EnergyPlus software. The building with all necessary input for simulation was modeled in Google SketchUp with aid of Open Studio Plug-in. Obtained results were compared with measured heating energy consumption. The results show that thermally activated building systems represent good way to increase building energy efficiency and that applying certain temperatures within this element, low-energy house standard can be achieved.

External fixed shadings are largely used to provide solar protection for building glazed surfaces. They are reducing heat gains and sensational visual discomfort caused by excessive daylighting. This paper presents a comparative study on external aluminium fixed shadings used on a student dormitory on different orientations and different slat angles. The purpose is to determine which slat angles are best to use in different orientations, from the point of view of energy consumption, thermal comfort, and daylighting. An analysis of annual energy consumption of the student dormitory was performed by using the software EnergyPlus, whereas the model of the building was created using SketchUp and OpenStudio software. Then, a parametric study was carried out by changing slat angles and building orientations, in order to find the best-balanced results with no occupant discomfort and possible energy savings. Results have shown that by considering the most balanced results between energy savings and thermal comfort, the best angles of the slats are from 105˚ to 120˚ on the south side, and from 45˚ to 75˚ on the east and west sides. By installing external shading devices, indoor thermal conditions are improving and may lead to significant energy savings, compared to a building without shading devices.

Implementation of co-generation of thermal and electrical energy in district heating systems often results with higher overall energy efficiency of the systems, primary energy savings and environmental benefits. Financial results depend on number of parameters, some of which are very difficult to predict. After introduction of feed-in tariffs for generation of electrical energy in Serbia, better conditions for implementation of co-generation are created, although in district heating systems barriers are still present. In this paper, possibilities and effects of implementation of natural gas fired cogeneration engines are examined and presented for the boiler house that is a part of the district heating system owned and operated by the Faculty of Mechanical Engineering in Nis. At the moment, in this boiler house only thermal energy is produced. The boilers are natural gas fired and often operate in low part load regimes. The plant is working only during the heating season. For estimation of effects of implementation of co-generation, referent values are taken from literature or are based on the results of measurements performed on site. Results are presented in the form of primary energy savings and greenhouse gasses emission reduction potentials. Financial aspects are also considered and triangle of costs is shown.