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Non-linear programming optimization method was used to optimize total steam and air consumption in the dryer section of multi-cylinder fluting paper machine. Equality constraints of the optimization model were obtained from specified process blocks considering mass and energy balance relationships in drying and heat recovery sections. Inequality constraints correspond to process parameters such as production capacity, operating conditions, and other limitations. Using the simulation, the process parameters can be optimized to improve the energy efficiency and heat recovery performance. For a corrugating machine, optimized parameters show the total steam use can be reduced by about 11% due to improvement of the heat recovery performance and optimization of the operating conditions such as inlet web dryness, evaporation rate, and exhaust air humidity, accordingly total steam consumption can be decreased from about 1.71 to 1.53 tonnes steam per tonne paper production. The humidity of the exhaust air should be kept as high as possible to optimize the energy performance and avoid condensation in the pocket dryers and hood exhaust air. So the simulation shows the supply air should be increased by about 10% to achieve optimal humidity level which was determined about 0.152 kgH2O/(kg dry air). [ABSTRACT FROM AUTHOR]

In this paper, a combined air/water source heat pump water heater is presented. At ordinary time, the heater can be used for hot water heating in water-source mode to improve the energy efficiency. While in cold season, it gives priority to air-source mode for water heating to improve operational safety. Experiments were conducted to investigate the thermodynamic performance of the heater in each operation mode, and the experiment results were analyzed. The research indicated that its operation was reliable during the long-time running. This paper offers a promising energy-saving method in future. [ABSTRACT FROM AUTHOR]

This paper studies a local fractional vibration system with a damped non-linear term to reveal its frequency property and its energy consumption. A modification of He's frequency formulation is recommended for this purpose. Some examples are given to illustrate the solving process and the reliability of the method. Additionally, the effect of the initial conditions on the vibrating properties is elucidated. This paper offers a new window for fast and effective insight into local fractional vibration systems. [ABSTRACT FROM AUTHOR]

The micro-electro-mechanical system is widely used for energy harvesting and thermal wind sensor, its efficiency and reliability depend upon the pull-in instability. This paper studies a micro-electro-mechanical system using He-Liu [34] formulation for finding its frequency-amplitude relationship. The system periodic motion, pull-in instability and pseudo-periodic motion are discussed. This paper offers a new window for security monitoring of the system reliable operation. [ABSTRACT FROM AUTHOR]

Along with the rapid economic development and social progress, the problem of energy and environment is becoming more and more outstanding. Therefore, it is very important to use new energy saving techniques to increase energy consumption and reduce energy consumption. In this paper, we have developed a hot water system, which is based on solar energy technology, gas-source heat pump, and phase change energy storage technology. The system was designed and constructed, and its performance was tested in various control conditions, with an emphasis on the analysis of the influence of phase change heat supply on heat storage properties. In this paper, the effect of the heat storage property is analyzed. Studies have shown that compared to a conventional tank that does not have a phase change heat storage device, the heat storage tanks equipped with phase change energy storage devices have longer discharge time, higher discharge temperature, better temperature, and better operation efficiency. In addition, the data show that flow rate control is also an important factor in optimizing the thermal storage characteristics of the system. [ABSTRACT FROM AUTHOR]

This paper introduces a novel design for a solar photovoltaic/thermal (PV/T) air collector that utilizes staggered fins. The collector features double-layer flow channels in the same direction, with the upper channel equipped with transparent wave plates, and the lower channel fitted with staggered fins. The paper includes a calculation scheme for wave plate heat balance. The numerical model of the collector is established and verified by experimental results. A numerical model is used to analyze the height combination of the upper and lower runner and the fin arrangement of the lower runner. The results indicate that, under the given environmental parameters, as the PV panel moves down, the overall air heat transfer capacity decreases. When the height combination of the upper/lower runner is 23 mm/105 mm, the maximum value is 53.741%. With the increase of fin spacing, the heat transfer capacity of the lower runner decreases. With the increase of the number of fin rows, the heat transfer capacity of the lower runner increases. When the equivalent diameter of the rectangular channel and the number of fin rows were 70 mm and 3 rows, respectively, the maximum solar energy comprehensive utilization efficiency was 56.261%. [ABSTRACT FROM AUTHOR]

The combined production of electricity and thermal energy (combined heat and power or co-generation) is the most efficient and convenient approach to reduce costs for energy at industrial power plants and district heating plants that use natural gas as fuel to produce thermal energy for various needs. This paper analyses the operational characteristics of the combined heat and power plant, which has been operating since January 1, 2021, at the Voždovac Heating Plant as part of the Belgrade district heating system. The combined heat and power plant consists of three gas engine units with a total nominal electric power of 10 MW and thermal power of 10.1 MW, which use natural gas as fuel. The combined heat and power plant is used for district heating and preparing domestic hot water while electricity is sold to the local electric grid. The analysis in this paper focuses on the plant's operational characteristics: the number of working hours, the total energy consumption and energy production, the efficiency as well as the operational and maintenance costs. Also, the impact of the drastic changes in the prices of natural gas, electricity, and maintenance costs in the last year on the financial profitability of the combined heat and power plant was analysed in particular. [ABSTRACT FROM AUTHOR]

This paper deals with methods for calculation of potentials of waste heat generated in paper/board production process. For that purpose, the material and heat balance of the cardboard machine at Umka Cardboard Mill has been determined. Field measurements were conducted in order to define the unknown values of process parameters used for calculation in the balance equations and modelling. The focus was given to the cardboard drying section, which consumes most of the energy supplied to the machine. Additional aim of the work presented in the paper was to evaluate the specific energy consumption and the thermal efficiency of all individual energy units within the machine's drying section. The results indicate two main sources of waste heat: waste heat released to the atmosphere with the discharge air from the present waste heat recovery system (14,380 kW), and waste heat released in the hall from the machine and extracted by the hall ventilation system (4,430 kW). Waste heat from both sources is characterized by fairly low temperatures 58-75 °? and fairly high moisture content (30-40 g/kg). The specific heat consumption and specific steam consumption (consumption per tonne of produced cardboard) of the machine was 1,490 kWh/t and 1.4 t/t, respectively. The thermal efficiency of drying section and coating drying section was 55.6% and 33.6%, respectively. All these figures imply necessity for further waste heat utilization with the aim of improving the efficiency of energy use. [ABSTRACT FROM AUTHOR]

A damping system always results in energy consumption. This paper studies an exponentially damped oscillator with historical memory for a viscoelastic damper structure, its stability under an initial response is analyzed analytically and verified numerically. [ABSTRACT FROM AUTHOR]

The refrigeration system accounts for 40-60% of the total energy consumption of the base station, so an effective energy-saving technology is much needed. This paper proposes a heat pipe air-conditioner with an additional soil heat exchange unit. When the indoor and outdoor temperature difference is small, the indoor heat can be scattered to the soil to achieve energy-saving effect. [ABSTRACT FROM AUTHOR]

In view of the prominent and intractable problems of frequent high temperature alarms of the communication equipment and high energy consumption of air conditioners in Zhengzhou communication outdoor cabinets, a temperature control system with heat pipe as the main part and air conditioner as the auxiliary part is proposed in this paper. A prototype is developed and its applications are discussed. The annual field test shows the system works well, and it has a remarkable energy saving efficiency. [ABSTRACT FROM AUTHOR]

In this study, an innovation was made by adding helical fins on the vortex finder of a cylindrical gas-solid cyclone separator, and the effect of this structural improvement on the separation performance was analyzed based on the flow field characteristics. The results show that both cyclones with and without helical fins exhibit a separation efficiency of almost 100% for particles larger than 5 µm. As the inlet velocity increases, the effect of adding helical fins on the overall separation efficiency decreases, with a relative deviation of only 0.16% at an inlet velocity of 27 m/s, while it becomes increasingly effective in reducing energy consumption, with a pressure drop of 25.33%. The mechanism of the overall performance improvement lies in the fact that the helical fins change the flow field distribution in the cyclone, where the turbulence intensity in the vortex finder is significantly reduced, the tangential velocity of the external vortex is decreased, and the pressure gradient is reduced. The purpose of this paper is to provide new ideas for the optimal design of the internal components of the cyclone separator. [ABSTRACT FROM AUTHOR]

The intensification of municipal-solid-waste (MSW) production, energy usage, and the curb of the landfill have developed the need for our society to use MSW under the vision of a waste-to-energy (WTE) approach to eradicating MSW as well as to address the energy issues across the world. The WTE alteration is an environment-friendly way of disposing of MSW. This study examines the usage of plastic, wood, and paper for refuse-derived fuel (RDF) production. The RDF is solitary of MSW energy yields, whose dependability and superiority are analysed in the current work. Two different RDF have been obtained from diverse waste streams at the plant site to find the finest RDF based on energy efficiency. Plastics, wood, and paper are the principal constituents in the method of occupied RDF. The results exhibited that the RDF-PA holds a high amount of carbon as-well-as hydrogen content and a decent calorific value, which leads to better fuel quality. The retention time under combustion and pyrolysis, the volatile matter portion of RDF, has increased accordingly. As per obtained results, RDF-PA is a good option for energy applications and fuel for combustion and pyrolysis reactions. [ABSTRACT FROM AUTHOR]

For normal operating conditions of the centrifugal fan, the manufacturers provide operating curves (total pressure of the fan, static pressure of the fan, power, and efficiency) for standard air conditions. However, when a fan operates with air at different, usually elevated temperatures, their operating curves can significantly differ. As a result, the fan efficiency decreases, and the energy efficiency of the fan may be reduced. Fan operation in such air conditions also affects its acoustic characteristics. This paper investigates two types of centrifugal fans: with forward curved and backward inclined blades. The main goal was to determine how their operating and acoustic characteristics change with the change in air temperature. For this analysis, low pressure centrifugal fans are used, for which we already had measured operating and acoustic characteristics. The influence of the type of impeller and the curvature of the blades play an important role in the operation of the fan. For numerical investigation, ANSYS CFX software was used, and obtained results show excellent agreement with experimental measurements. [ABSTRACT FROM AUTHOR]

The great potential for reduction of CO2 emissions lies in the deep energy renovation of buildings that exploits the full potential of improving energy efficiency in buildings to maximize energy savings and minimize energy costs. However, in addition to the technical parameters, it is necessary to analyze the willingness of the client to pay for deep energy renovation. This paper presents a methodology applicable to all types of buildings that in a relatively short time provides an optimal solution that meets both parameters - technical and economic, while satisfying the legal requirements. The method was tested by simultaneous use of DESIGNBUILDER software package (which uses ENERGYPLUS as its dynamic simulation engine), PYTHON and SQL programming languages on an office building in the city of Zagreb, where a total of 720 combinations of building deep energy renovation were analyzed. In the analyzed case, it was proved that the application of this methodology results in obtaining the output values 20.51 times faster than the classical input of all combinations of deep energy renovation of the building in software tools. In addition, the probability of human error is much lower by applying this methodology given large amount of input data. [ABSTRACT FROM AUTHOR]

In order to improve the short-term energy consumption control effect of green buildings and shorten the control time, this paper proposes a short-term energy consumption control method of green buildings based on density peak optimization. Firstly, the research status of green building energy consumption control is analyzed, and the short-term energy consumption data information of green building is obtained. Secondly, the definition of peak density algorithm is given, the short-term energy consumption control model of green building is constructed, and the initial cluster center of the short-term energy consumption model of green building is selected to calculate the probability density of the short-term energy consumption control model of green building. Finally, the adaptive genetic algorithm is used to control the short-term energy consumption of green buildings. The experimental results show that the research method can achieve good prediction accuracy in each season, and the short-term energy consumption control time of green buildings is only 3.2 seconds, indicating that the research method can effectively improve energy consumption control efficiency, shorten the short-term energy consumption control time of green buildings, and verify the superiority of the research method. At the same time, it indicates that the research method has certain application value in short-term energy consumption control of green buildings, and can provide a theoretical basis and data support for the field of short-term energy consumption control of green buildings. [ABSTRACT FROM AUTHOR]

To address the current problem of high energy consumption in data centers, this paper proposes a data center heat pipe air-conditioning system based on the latent heat of water evaporation, which uses the latent heat of water evaporation for cooling by creating a low pressure environment to evaporate large amounts of water. In order to verify the effect of the system, a heat pipe test bench based on the latent heat of water evaporation was designed and built. Compared with the traditional heat pipe in the data center for heat dissipation, the performance and economy of the water evaporation latent heat pipe system designed in this paper are analyzed experimentally. A multi-physics coupled model of water evaporation latent heat pipe air-conditioning based on COMSOL Multiphysics was established to simulate and study the temperature field and velocity field distribution of water evaporation latent heat pipe air-conditioning system in data centers. The research shows that: -- Under the designed test conditions, compared with the traditional heat pipe system, the water evaporation latent heat pipe air conditioner can conduct 2540 kJ more heat in one day in an outdoor environment of 24 °C. -- At an ambient temperature of 3 5°C and an indoor temperature of 25.8 °C, the cooling capacity of the heat pipe in the data center water evaporation latent heat pipe air-conditioning system is twice the cooling capacity of the air conditioner, and the heat pipe can work efficiently regardless of the outdoor ambient temperature. -- The energy-saving effect of the latent heat pipe of water evaporation in the data center has a significant effect on air conditioners with an energy efficiency rating (EER) lower than 2.5-4.4. It can improve the energy efficiency of level 5 with an EER of 2.5 to level 2 with an EER of 3.22, greatly reducing the power consumption of the data center air-conditioning system. When the EER of the air conditioner exceeds 4.4, the coefficient of performance of the data center water evaporation latent heat pipe air-conditioning system will be lower than that of the air conditioner itself. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Since the reduction of energy consumption and efficient energy use, particularly in the building stock, is the priority for contemporary societies, the ways of how to improve the existing buildings should be examined. Flat roofs, as a part of the existing building thermal envelope, are recognized as a field of intervention for improving efficient energy use for space cooling and heating. The topic of the paper is to determine to what extent different improved roof structures affect energy consumption intended to achieve thermal comfort. Comparative analysis of four roof structures was conducted for the building of Healthcare center Niš in Serbia, one improved non-walkable flat roof structure and three green roof systems. Urbancsape extensive green roof system was used in all tested green roof models: non-walkable extensive green roof, walkable extensive green roof, and extensive and intensive green roof systems within walkable terraces. DesignBuilder software was used for energy modelling. The obtained results indicate a slight decrease in energy consumption for building models with green roofs compared to the building model with the improved non-walkable roof structure, along the cooling period, by approximately 1.5%, which is correlated with previous studies in similar conditions. On the other hand, the reduction of energy consumption over the heating period was negligible (less than 1%). Considering the results and predominant usage of commercial Urbanscape extensive green roof system in all green roof models, being characterized by small thickness (10.64 cm) and light structure, and which is predicted to be installed over the already well-insulated roof, the system's role as an additional thermal mass was confirmed. [ABSTRACT FROM AUTHOR]

The integration of wastewater heat pumps (using purified water) in district heating systems is analyzed in this paper. The simulation procedure is proposed to analyze the impacts of stochasticity of purified water temperature and flow to heat pump integration and operation. The analysis includes calculation of the daily and seasonal coefficient of performance, as well as fossil fuel savings and CO2 emission reduction due to wastewater heat pump use. The proposed procedure is implemented for the case study in the city of Šabac (Serbia) and obtained results are discussed and evaluated. The historical data for two heating seasons was used for simulation. It was shown that the wastewater heat pump could provide 27-28% savings in fuel consumption, and 3.6-4.1% GHG emissions reduction, while the seasonal COP could be 4.2 - 4.3. Simulation based approach shows approximately 40% less savings of fuel consumption, compared to the approach based on the average values of heat pump input parameters. [ABSTRACT FROM AUTHOR]

In this paper, the feasibility of two low global warming potential refrigerants R513A and R1234yf as alternatives to R134a was tested in an automotive air conditioning system in winter. The test results showed that the heating capacities of R513A and R1234yf were 2% and 4% lower than that of R134a, and their COP were 3-9% and 6-19% lower than that of R134a, respectively. It revealed that R513A can be used as a transition product to replace R134a, and R1234yf required further improvements to improve the energy efficiency. [ABSTRACT FROM AUTHOR]

In order to solve the problem of poor refrigeration performance during operation of the refrigeration system under low temperature conditions, this paper designs a refrigeration system test bench to study the effect of different air volumes on the cooling capacity of the refrigeration system under the conditions of 32 outside the warehouse and -10 inside the warehouse. The results show that when the air volume of condenser is set to 65% of the unit air volume and the air volume of evaporator is set to 100%, the cooling capacity of the system is 8.62 kW, the compressor power is 1.88 kW, the COP is 4.55 and the energy efficiency ratio is 1.64. In comprehensive consideration, this can not only ensure the best refrigeration performance but also can save considerable energy consumption. [ABSTRACT FROM AUTHOR]

In order to solve the problem that the cold/heat released from the underground pipe of coal mine into the soil layer is difficult to dissipate in a short time, the technology of enhancing the underground flow field of coal mine in geothermal energy development to improve the energy efficiency of the heat pump system is proposed. In this paper, based on the ground source heat pump project located in a coal mine, the energy efficiency enhancement technology of the artificial flow field ground source heat pump system is studied and tested. The test results show that when starting work at about 8:00, due to the increase of heating load, the accumulation of cooling capacity around the buried pipe increases gradually, and the return water temperature at the ground source side decreases gradually. At 14:05, the water was pumped for the operation of the artificial groundwater flow field. It can be seen that the temperature of the return water at the ground source side began to rise gradually, indicating that the accumulation of cold water around the buried pipe was relieved to a certain extent. In conclusion, the artificial groundwater flow field can alleviate the accumulation of cold water around the buried pipe heat exchanger to a certain extent, improve the return water temperature of the buried pipe heat exchanger, and improve the energy efficiency of the ground source heat pump system. [ABSTRACT FROM AUTHOR]

An emergency caused by the COVID-19 pandemic affected the rethinking of existing healthcare systems. The increased need for hospital beds appeared short after the outbreak of the pandemic and the solution was to adapt the existing buildings, primarily public ones. Among all, sports buildings, i.e. sports halls were successfully used around the globe for conversion into hospitals. Topic of the paper was to investigate whether sports halls in Serbia, which were also used as temporary hospitals, are suitable for conversion in terms of energy consumption needed for achieving thermal comfort. Two case studies were analysed. The energy simulations were done using the DesingBuilder software. The results of thermal comfort summary and energy consumption led to the conclusion that this building type in Serbia could be successfully used for hospital purposes. Although the multiple increase in energy consumption was noted during the heating period, the results were within the limits required by both national and international standards. [ABSTRACT FROM AUTHOR]

A numerical simulation of energy efficiency in commercially available double pipe heat exchangers in the market was investigated based on the Second law of thermodynamics in this paper. The effects of CO2 mass-flow rate, water mass-flow rate, pressure, CO2 inlet temperature, and water inlet temperature of the double pipe heat exchanger were considered to evaluate the energy efficiency by analyzing entropy generation, exergy destruction, and entransy dissipation. The changes of the entropy generation, the changes of exergy destruction, and entransy dissipation are similar regardless of the operating conditions. Pressure has the most significant effect on the energy efficiency of the double pipe gas cooler compared to other operating conditions but negligible on the exergy destruction. The pressure, flow rate, and inlet temperature have completely different effects on energy efficiency depending on the region. The entropy generation and entransy dissipation at y = 0 m to y = 0.05 m (y-axis is the radial direction) decrease with increasing pressure and the opposite after that. The increase of CO2 inlet temperature at y < 0.5 m is accompanied by an increase of entropy generation, exergy destruction, and entransy dissipation but this situation disappears after y = 0.5 m. Entropy generation, exergy destruction, and CO2 and water mass-flow rate are first negatively and then positively correlated with the cut-off point at y = 0.1 m. [ABSTRACT FROM AUTHOR]

The ground source heat pump system is a promising technology for building heating and cooling by using underground energy, however, many technical problems, e. g. low energy utilization rate and inefficiency operation, have greatly hindered its wide applications. This paper studies the key technologies of vertical U-shaped heat exchangers in construction engineering to solve the bottleneck problem and optimizes the system. Three commonly used backfill methods are analyzed, and a double U-shaped branch pipe is recommended to improve construction efficiency. The paper sheds a bright light on green energy utilization with high-efficiency, energy-saving, and environmental protection. [ABSTRACT FROM AUTHOR]

The main goal of this paper is to develop and prioritize renewable energy scenarios for electricity production. The model proposed in the paper was applied on the example of the municipality of Štrpce, enclave in south Kosovo**. The model consists out of three phases, and the decision-making and planning process involves a group of decision makers, i.e. selected experts and stakeholders. In the first phase, a group of decision makers, using a collaborative planning method and Homer pro software, defined eight renewable energy scenarios based on renewable energy potentials and electricity demand in Štrpce. In the second phase, a group of decision makers, using the strengths, weaknesses, opportunities, and threats analysis, defined a total of 22 criteria to evaluate scenarios. Finally, in the third phase, a group of decision makers used fuzzy analytical network process methodology to prioritize scenarios. Results show that a scenario that includes installation of photovoltaic panels in Štrpce households to cover 50% of the electricity demand is first ranked. The proposed model has a universal character which means that it can be applied in other municipalities/cities and regions. Also, the model enables collaborative planning through the inclusion of different stakeholders whose number and type can be adjusted according to the subject/ area of research. [ABSTRACT FROM AUTHOR]

The energy revolution considering renewable power is indispensable and inevitable in the development of modern power industry, yet has been restricted by many practical problems. The instability of renewable energy makes the whole power generation system unable to maintain stable output, which causes fluctuations in the power grid system, and ultimately affects the user side. Also, there are few researches on hybrid heat and power co-generation system and when applied to the regional power supply, current systems converse electric energy to thermal energy to meet the heating demand of users, which reduces the energy quality. Hybrid two or more kinds of renewable energy is a way to eliminate instability of renewable energy power generation system. In this paper, a hybrid heat and power co-generation system is designed to reach both heat and power demands of users, a solar-geothermal power generation system was simulated on ASPEN PLUS platform. The output power, entropy and energy efficiency are analyzed to optimize the system. Based on the solar-geothermal power generation system, exergy analysis shows that the parallel heating and power generating system is much more efficient than the original system. [ABSTRACT FROM AUTHOR]

Kindergartens are probably the very first public buildings we actively use in our lives. Therefore, they can be considered as the physical structures that are providing for the very important educational and social function. Additionally, they can also be considered as the specific learning tool for future generations where they can encounter the ideas of green and energy-efficient buildings. One of the results of the research project "Energy efficiency in public buildings" has been formulated through the development of Serbian National Typology of Kindergartens which was conceived as a specific tool that can be used for improving this portion of building stock. The paper presents the methodology for identification of typical kindergarten buildings, covering various construction periods, building sizes and illustrates the type of analysis performed for model representatives. The potential for energy upgrades covering physical structure, installed technological systems, as well as expected impact on energy performance, has been estimated. The study presents results based on the analysis of the data derived from the National Typology, stressing out that energy retrofits of large and medium-sized kindergartens built during the 1970s and 1980s should be the primary focus of refurbishment activities. Accounting for almost 60% of total buildings and 69.59% of heated area, they are responsible for 75.97% of energy demands. Estimated energy savings of more than 60% indicate the effectiveness of their retrofit. The paper also presents the potential uses of National Typology as a retrofit tool on various scales, from single-building considerations to a strategic approach at the national level. [ABSTRACT FROM AUTHOR]

A passive solar building cannot only save cost and reduce energy consumption, but also benefit the harmonious development of society. This paper introduces an optimal design strategy by taking into account its external environment, the building layout, the shape coefficient, the building envelope, and the building structure. An example is given to reveal various concepts and their applications. [ABSTRACT FROM AUTHOR]

Real time prediction of energy consumption is the basis of energy conservation and emission reduction. Aiming at the problems of large prediction error and poor effect, a real-time prediction method of energy consumption of geothermal system of public buildings based on wavelet neural network is proposed. Firstly, the energy consumption of geothermal system in public buildings is analyzed, the wavelet neural network is designed, the neural network is optimized and solved by genetic algorithm, and the necessity of constructing the real-time prediction model of energy consumption based on wavelet neural network is established. Then it introduces the basic principle of model establishment, wavelet analysis, and shows the role of wavelet analysis in prediction model. Finally, based on the distribution structure of public buildings, this paper analyzes the energy consumption system of geothermal system, constructs the energy consumption prediction method, analyzes the overall temperature regulation energy consumption prediction principle of building geothermal system, and realizes the real-time prediction of energy consumption of geothermal system of public buildings. The experimental results show that the energy consumption real-time prediction results of the designed method are basically similar to the actual prediction values, and the prediction efficiency is high, which can effectively reduce the energy consumption of the geothermal system of public buildings. [ABSTRACT FROM AUTHOR]

The current design of vibration energy recovery system for vehicle suspension does not analyze the vibration of the vehicle under different road conditions, resulting in the system's low energy recovery ratio, low recovery efficiency, and low energy utilization. Therefore, in this paper, the vibration energy recovery system of vehicle suspension based on ultrasonic sensors is proposed. The ultrasonic sensor is used to obtain the vibration information of the vehicle, and the vibration of the vehicle on the smooth and uneven roads is analyzed according to the obtained information. According to the analysis results, the design of the vibration energy recovery system for vehicle suspension is completed through four parts: the IGBT module, the control system, the direct thrust controller, and the energy management controller. The experimental results show that the system designed by the proposed method has a large energy recovery ratio, high recovery efficiency and high energy utilization rate. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to establish a mathematical framework to analyze the complex thermal economic performance of the calcination process. To find the factors affecting exergy efficiency loss, different exergy destruction is investigated in detail. Furthermore, the exergy flow cost model for exergy cost saving has also been developed. The results show that the vertical shaft furnace is a self-sufficiency equipment without additional fuel required, but the overall exergy destruction accounts for 54.11% of the total exergy input. In addition, the energy efficiency of the waste heat recovery boiler and thermal deaerator are 83.52% and 96.40%, whereas the exergy efficiency of the two equipment are 65.98% and 94.27%. Furthermore, the import exergy flow cost of vertical shaft furnace, waste heat recovery boiler and thermal deaerator are 366.5197 RMB per MJ, 0.1426 RMB per MJ, and 0.0020 RMB per MJ, respectively. Based on the result, several suggestions were proposed to improve the exergoeconomic performance. Assessing the performance of suggested improvements, the total exergy destruction of vertical shaft furnace is reduced to 134.34 GJ per hours and the exergy efficiency of waste heat recovery boiler is raised up to 66.02%. Moreover, the import exergy flow cost of the three different equipment is reduced to 0.0329 RMB per MJ, 0.1304 RMB per MJ, and 0.0002 RMB per MJ, respectively. [ABSTRACT FROM AUTHOR]

Utilization of efficient technologies, renovation of buildings and construction of new passive buildings, replacement of coal, natural gas, and nuclear power plants with "clean" technologies such as photovoltaics and wind, transition to 4-D in industry, and electrification are parts of the objectives set out in the Green Deal of the EU. The Green Deal foresees a transformation to a "green" economy while maintaining economic growth, as well as creating new "green" jobs. To meet these goals, each country needs to develop its own strategic documents that will guide the transition, taking into account its own specific conditions, the current state of the energy sector as well as geographical location. This paper aims to present a vision for the energy transition of a developing country, a member of the Energy Community, and a country that expects to join the EU. The vision of the development of the energy system of North Macedonia foresees a transformation from a system based on fossil fuels, where the share of RES in the gross final energy consumption is about 18%, to a 43% share of RES in 2040, while maintaining import dependence at the current level and guaranteeing the security of energy supply. For exploring the way and the pace at which such a vision can be achieved it is necessary to develop different models and simulations, including different technologies on the generation and consumption side. Such alternatives, packaged in different scenarios, allow policymakers to assess the effects of taking certain actions and the direction in which such decisions will lead. [ABSTRACT FROM AUTHOR]

The paper combines the testing work of ground source heat pump systems, discusses the installation, use methods and test errors of various testing instruments, combines the field test experience, gives the main points of ground source heat pump energy efficiency testing, and according to the problems encountered during the test. The faults with high frequency are analyzed, and the methods of fault diagnosis and troubleshooting are given. This paper uses the ground-source heat pump experimental platform to set up multiple sets of experimental schemes to study the impact of factors such as pipe diameter, single and double U, and flow rate on system energy efficiency. At the same time, it combines engineering cases to "large flow small temperature difference", "imbalance" phenomenon is analyzed, and feasible solutions and suggestions are given. By analyzing the energy efficiency and benefits of actual engineering of multiple ground source heat pump systems, the paper concludes that ground source heat pump systems have a wider application prospect in a certain area of Hubei. [ABSTRACT FROM AUTHOR]

Energy certification of buildings in Serbia was introduced in 2011 and energy label depends on energy need for heating per unit floor area of heated space, calculated by the fully prescribed monthly quasi-steady-state method defined by ISO 13790. In the Republic of Serbia, most of families live in single-family houses built before the energy certification of buildings was introduced. Therefore, the estimation of energy performance of the existing buildings is important for labeling, and evaluation of energy saving measures and energy strategies to be implemented. This paper examines the applicability of monthly method defined by National legislation on the existing buildings stock in Serbia, by comparing it to the more accurate dynamic simulation method. Typical singlefamily houses are taken as a test case, since they are responsible for about 76% of energy consumption for heating. The results show that the dynamic simulation method estimates 21% to 54% higher energy need for heating, compared to the monthly method. Also, the monthly method estimates up to 13% higher savings by typical building envelope energy saving measures, compared to the dynamic simulation. This paper recommends improvement in procedures for calculation of building energy performance index to better assess energy consumption, effects of energy saving measures, and create solid background for developing and implementing of energy saving strategies. [ABSTRACT FROM AUTHOR]

Buildings are significant energy consumers and provide a notable potential to reduce primary energy consumption and increase energy efficiency. Cost-effectiveness of energy efficiency projects is of crucial importance for their implementation. Cost-optimality of different packages of energy retrofit measures is studied across the EU, but Serbia mostly lacks such information. This paper analyzes cost-optimal solutions for Serbian residential buildings connected to district heating systems, considering three different scenarios related to the economic input parameters. Additionally, it considers the potential for primary energy savings beyond cost-optimality and associated costs. The optimal solutions, that correspond to minimal global cost or minimal primary energy consumption, are determined as the results of the combinatorial optimization problems. These problems are solved using the genetic algorithm and local search. The results are compared against the ones obtained with the sensitivity analysis. The global cost can be reduced by 8-43% in the cases of cost-optimal solutions, simultaneously saving 30-76% of primary energy. The potential to save primary energy is higher - it exceeds 70% in all the analyzed cases, but also requires higher global cost, sometimes larger than in the absence of the retrofit. The paper also emphasizes high dependencies of the results on very uncertain economic inputs. [ABSTRACT FROM AUTHOR]

The greenhouse effect was focused by more learners with the global warming. It has become a very serious issue the relationship between foreign direct investment (FDI) and carbon emissions in the process of sustainable economic development in Shandong. This paper studied the relationship trend in middle of FDI, carbon emissions, and greenhouse effect impact mechanism in Shandong Province based on the data from 2000 to 2016 in Shandong Province by simultaneous equation model from qualitative and quantitative analysis. There is an inverted environmental Kuznets curve correlation between FDI and carbon emissions. The mechanism of FDI's impact on Shandong's ecological environment in three aspects: scale effect, structure effect, and technology effect. The results show that FDI has negative scale effect, structure effect and positive technology effect on carbon emissions in Shandong Province, and the overall effect is negative. Accordingly, taking the transformation of new and old kinetic energy in Shandong Province as the goal, this paper puts forward the optimization strategy, provides policy suggestions for the government in the implementation of the transformation of new and old kinetic energy, in order to better promote economic development, industrial restructuring and upgrading, and realize the construction of regional ecological civilization. [ABSTRACT FROM AUTHOR]

Currently, in the building sector there is an increase in energy use due to the increased demand for indoor thermal comfort. Proper energy planning based on a real measurement data is a necessity. In this study, we developed and evaluated hybrid artificial intelligence models for the prediction of the daily heating energy use. Building energy use is defined by significant number of influencing factors, while many of them are difficult to adequately quantify. For heating energy use modelling, the complex relationship between the input and output variables is hard to define. The main idea of this paper was to divide the heat demand prediction problem into the linear and the non-linear part (residuals) by using different statistical methods for the prediction. The expectations were that the joint hybrid model, could outperform the individual predictors. Multiple linear regression was selected for the linear modelling, while the non-linear part was predicted using feedforward and radial basis neural networks. The hybrid model prediction consisted of the sum of the outputs of the linear and the non-linear model. The results showed that both hybrid models achieved better results than each of the individual feedforward and radial basis neural networks and multiple linear regression on the same dataset. It was shown that this hybrid approach improved the accuracy of artificial intelligence models. [ABSTRACT FROM AUTHOR]

One of the aspects for optimizing the powdered biofuel combustion technology is to ensure proper relationship between powder production and its delivery into the reactor. This paper focuses on the effect of a time delay between production and use of powdered fuel on its combustion efficiency using pine sawdust as an example. It was established that the ignition delay time increases with an increasing delay between powdered fuel production and use (i.e., the effect of sample aging takes place). A correlation between the ignition delay time, the amount of lignin radicals, and the sample's ability to release volatile combustible matter is demonstrated. [ABSTRACT FROM AUTHOR]

A walking beam type reheating furnace with advanced control technology has been evaluated by combined energy and exergy analysis. In order to gain insight into the performance of the present furnace, the results of energy analysis are compared with those in published papers and the irreversibility of the furnace is analyzed via exergy destruction calculation. The results show that slabs preheated before charged into the furnace can save fuel and improve energy utilization. The structure and material of the wall and roof show good thermal insulation. However, the oxidized scale is a little more and the temperature of flue gas is high in the present reheating furnace. The energy efficiency of the furnace is 71.01%, while exergy efficiency is 51.41%, indicating a potential for energy-saving improvements of the present furnace. The exergy destruction of the furnace accounts for 28.36% of total exergy input which is mainly caused by heat transfer through a finite temperature difference (14.71%), fuel combustion (11.66%), and scale formation (1.99%). [ABSTRACT FROM AUTHOR]

In this paper, based on the idea of reducing heat exchanger exergy destruction and increasing turbine work, a new three-stage cascade Rankine system and a new four-stage cascade Rankine system is proposed to improve the cold energy utilization rate during liquefied natural gas gasification on liquefied natural gas-floating storage and regasification unit. Then compare them with the original cascade Rankine cycle established under the same conditions. The results show that under the condition of 175 tonne per hour liquefied natural gas flow, the maximum net output power of the new three-stage cascade Rankine cycle system is 4593.31 kW, the exergy efficiency is 20.644%. The maximum net output power of the new four-stage cascade Rankine cycle system is 5013.93 kW, and the exergy efficiency is 22.509%. Compared with the original cascade Rankine cycle system, the maximum net output power of the new three-stage cascade Rankine cycle system and the new four-stage cascade Rankine cycle system is increased by 9.41% and 11.45%, respectively, and the system exergy efficiency is increased by 9.29% and 11.28%, respectively. [ABSTRACT FROM AUTHOR]

In order to reduce energy consumption of the centralized chilled-water cooling system in large buildings, a dynamic control strategy was proposed for cooling plants by modelling and optimization. Combined with the chilled water flow model, this paper analyzed the parallel operation characteristics of the chillers and takes the load distribution as one of the control parameters. Based on the measured data of a typical cooling system that has undergone preliminary energy-saving transformation, the residual neural network is applied to model the relationship among energy consumption, controllable parameters and environmental parameters, and the residual neural network outperforms multi-layer perceptron and support vector regression. To minimize the total energy consumption, the gray wolf optimizer was introduced to optimize the controllable variables of the cooling system. Compared with the energy consumption before optimization, the simulation energy consumption after optimization decreased 10.45% on average, while the energy saving rate is only 7.9% with equal chilled water supply temperature of parallel chillers. [ABSTRACT FROM AUTHOR]

The paper tests the changes in the pH value of the anolyte and catholyte. The 3-D multi-phase 3-D multi-current conductivity values analyze the electricity generation process and energy utilization of the microbial fuel cell (AMFC) and provide a theory for improving the AMFC following the performance. The test results show that with the operation of AMFC, the pH value of the anolyte and the 3-D multiflow conductivity show a downward trend, the pH value of the catholyte and the 3-D multi-flow conductivity show an upward trend, and the ratio of the pH value of the catholyte the pH value of the anolyte is about 0.30-0.50 higher, and the average 3-D multi-current conductivity of the anolyte and catholyte does not change much. When AMFC operates stably, the internal ohmic resistance is 29.69 Ω, the limiting current is 2.69 mA, the maximum output power is about 0.8 mW, and the corresponding internal resistance is about 95.72 Ω. The mass transmission of potassium ferricyanide is the limiting factor of limiting current. Numerical analysis of 3-D multi-phase flow found that other microorganisms consume 91.1% of the glucose in AMFC anolyte, and only 8.9% of the glucose is used for power generation. The 88.5% of the energy of the glucose used for power generation is converted into other forms of energy, only 11.5% of the energy is converted into electricity. [ABSTRACT FROM AUTHOR]

The paper takes the front-mounted parallel structure of the transmission as an example and uses the target detection algorithm to introduce a real-time equivalent energy consumption control strategy for the vehicle engine thermal energy system. Based on studying the relationship between fuel thermal energy and electrical energy consumed when the vehicle is driving in a cycle, we elaborated on the strategy’s critical issue, namely, the equivalent method of the electrical energy of the battery pack and the fuel thermal energy consumption of the engine. Finally, the thesis carries out a simulation test on this strategy based on the vehicle simulation model and compares it with other control strategies. [ABSTRACT FROM AUTHOR]

Data-driven black-box surrogate models are widely used in research related to buildings energy efficiency. They are based on machine learning techniques, learn from available data, and act as a replacement for or an addition to complex and computationally intensive knowledge-based models. Surrogate models can predict energy demand, indoor air temperature, or occupants behavior, explore search space in optimization problems, learn control rules, etc. This paper analyzes surrogate models that classify building retrofit measures directly according to the global cost. In addition, they quantify the importance of each variable for the classification process. The models are based on random forest classifiers, which are fast and powerful ensemble learners. They can be applied to effectively reduce search spaces when optimizing energy renovation measures or to rapidly identify projects that deserve financial support. This approach is applied to two residential buildings and three scenarios of price development. The training process uses a small share of retrofit options assessed with standard calculations of the heating and cooling demands, as well as the global cost. The results show very high classification performance, even when the models are trained with small and imbalanced training sets. The obtained recall, precision, and F-score values are mostly above 95%, except for extremely small training sets. [ABSTRACT FROM AUTHOR]

This paper analyses the possibility to apply energy refurbishment measures in restored historic buildings in order to ensure reuse. The objective of the paper is to provide an appropriate methodology for the structural restoration of historic buildings, their re-use and sustainable energy refurbishment in accordance with current needs and conservation principles. The study provides the analysis and evaluation of the realized goals regarding energy refurbishment and energy efficiency. The presented historic buildings belong to Hilandar Monastery, Mount Athos, Greece. Mount Athos has been listed in UNESCO World Heritage Site for decades. The paper deals with the expert analysis of abandoned and devastated structures included in the Haybarn Complex. This paper provides a positive outcome of the performed restoration in terms of energy refurbishment and repurpose, since these buildings were turned into unique accommodation facilities for visitors. This accomplishment can be seen as a useful recommendation for improving energy efficiency of historic buildings during their restoration. All the undertaken methods are in accordance with the environmental protection requirements. This study is a practical observation and analysis of energy refurbishment in the field of restoration of listed buildings. This certainly is the most important contribution of this paper. All energy efficiency measures and renewable energy sources were carried out in compliance with conservation requirements and visual authenticity of historic structures. Assessment and analysis of energy efficient refurbishment via building performance simulation method and energy efficiency optimization was applied to several different models of restoration that was carried out in the Haybarn Complex. [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]

The aim of paper was to discuss contribution of bi-fuel CNG powered light commercial vehicles to the well-to-wheel CO2 equivalent emissions, both today and in the coming decades in which the development of new fuels and new vehicles is expected. Field research was done in Belgrade, during one year, using Euro 5 diesel/LPG/CNG light commercial vehicles driving under low vehicle speed, low engine load, low exhaust gas temperature and high number of stops. The well-to wheel as neutral methodology was applied for understanding of each fuel pathway in terms of reducing greenhouse gas emissions and increasing energy efficiency. Calculation showed that total energy consumption per kilometre is the lowest for diesel vehicles since petrol/LPG and petrol/CNG vehicles use 21% and 7% more energy. Tank-to-wheel emission of CO2 equivalent is most favorable for petrol/CNG with 28.8% and 6.7% less CO2 equivalent with petrol/LPG and diesel vehicles. The same conclusion brings well-to-wheel analysis showing that diesel/CNG CO2 equivalent emission is 13.5% less than petrol/LPG, apropos 1.5% less than diesel operated vehicles considered within this field research. Figures are not as high as previous, due to the results of well-to-tank emission, that were most favorable for petrol/LPG powered vehicles, with almost 51% and 32% better results regarding to petrol/CNG and diesel, respectively. Within same time, lowest fuel cost per kilometre was achieved by petrol/CNG vehicles, with 32% and 35% less cost than petrol/LPG and diesel vehicles. The available CNG technology should not be neglected, waiting for new solutions to be proven. [ABSTRACT FROM AUTHOR]

The development of Internet of Things devices as well as the increase of nodes in wireless networks, motivates the use of node’s cooperation for wireless system performance improvement. On the other hand, the power requirements of the increasing number of nodes leads to the need for new powering sources. In this paper we consider device-to-device relay-assisted system, where decode-and-forward relay is not equipped with its own power supply, but it harvests energy and uses it for the data transfer to the destination node. System performance is derived for the Fisher-Snedecor F composite fading channel model and energy harvesting protocol based on time-switching scheme. The closed-form approximate expression for the outage probability is derived, that corresponds to the exact results. The impact of the channel fading and shadowing parameters and time-switching factor of energy harvesting protocol on the system performances are investigated. Numerical results are confirmed by an independent simulation method. [ABSTRACT FROM AUTHOR]