IMPACT OF REDUCED HEATING DEMAND ON GREENHOUSE GASES EMISSION UNDER COST-OPTIMAL OPERATION OF COGENERATION PLANTS

Demand-side energy efficiency measures in buildings are usually considered advantageous from the environmental aspect. Similarly, the implementation of modern flexible energy-efficient cogeneration plants is often beneficial in respect for energy consumption and the environmental impact. However, the joint effects of these two approaches towards energy efficiency and greenhouse gases emission reduction are: dependent on many factors, more complex and harder to estimate. This paper analyses the impact of residential buildings heating demand reduction on greenhouse gases emission from a cogeneration plant. It illustrates realistic scenarios in which the reduction of heating demand might lead to the increase of greenhouse gases emission when an energy supply system operates in a cost-optimal manner

Bin weather data for City of Niš

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POSSIBILITIES TO MINIMIZE GREENHOUSE GASES EMISSION AND MAINTAIN THERMAL COMFORT IN OFFICE BUILDINGS WITH CO-SIMULATION ASSISTED OPERATION OF AIR HANDLING UNITS

Energy efficiency measures in existing buildings include improvements in heating, ventilation and air conditioning systems but from the perspective of system renovation and components upgrade. These measures target the building energy consumption and resulting greenhouse gases emissions, with thermal comfort of occupants being seen only by one or two parameters. Improvements in existing system operation can lead to minimal greenhouse gases emission, but with thermal comfort maintained at the desired level. This paper evaluates the possibility to minimize greenhouse gases emission while maintaining occupant thermal comfort within prescribed class, by optimizing the existing air conditioning system operation with 5 weekdays planning horizon. Particle swarm optimization method is used. The paper shifts the focus from minimal emissions to minimal emissions for desired thermal comfort range, without system renovation or upgrade. The results show that maintaining thermal comfort results in higher greenhouse gases emission compared to usual system operation where emissions are lower but thermal comfort is outside desired range almost all the time

The possibility of fireside corrosion occurrence in domestic boilers furnaces with low NOx combustion technology

The emission of nitrogen oxides (NOx) during combustion of fossil fuels is considered as one of the major sources of environmental hazards. As a result, the limitations of concentration of nitrogen oxides in fuel gases are regulated. The implementation of low NOx burners in pulverized coal-fired boilers has led to a rise in the fireside corrosion rate of the waterwall boiler tubes in some power plants. Under normal combustion conditions, an oxidizing atmosphere helps formation of a protective oxide scale on the surface of the boiler tubes, thus impeding gaseous corrosion. However, the use of low NOx technology changes the combustion environment, resulting in the presence of reduction gases characterized by large amounts of CO and H2S. In areas of reducing atmosphere, a porous, non-protective scale is produced on the waterwalls that could leads to significant metal loss per year due to corrosion. In order to better understand the mechanisms and kinetics of the fireside corrosion, it was determined that, in addition to the type of atmosphere formed during fuel combustion, coal composition has an important role in the occurrence of fireside corrosion. The aim of this paper is to analyze the possibility of occurrence of fireside corrosion, i.e., determine the corrosion potential of domestic coals and identify possible problems that could occur during combustion using low NOx technologies

Multi-Objective Combinatorial Optimization of Trigeneration Plants Based on Metaheuristics

In this paper, a methodology for multi-objective optimization of trigeneration plants is presented. It is primarily applicable to the systems for buildings’ energy supply characterized by high load variations on daily, weekly and annual bases, as well as the components applicable for flexible operation. The idea is that this approach should enable high accuracy and flexibility in mathematical modeling, while remaining efficient enough. The optimization problem is structurally decomposed into two new problems. The main problem of synthesis and design optimization is combinatorial and solved with different metaheuristic methods. For each examined combination of the synthesis and design variables, when calculating the values of the objective functions, the inner, mixed integer linear programming operation optimization problem is solved with the branch-and-cut method. The applicability of the exploited metaheuristic methods is demonstrated. This approach is compared with the alternative, superstructure-based approach. The potential for combining them is also examined. The methodology is applied for multi-objective optimization of a trigeneration plant that could be used for the energy supply of a real residential settlement in Niš, Serbia. Here, two objectives are considered: annual total costs and primary energy consumption. Results are obtained in the form of a Pareto chart using the epsilon-constraint method

Examination of the physical-chemical and mechanical properties of helical cylindrical compression springs preserved in the Legacy in the Nikola Tesla Museum

The results of the scientific research work and creativity of Nikola Tesla (Smiljan, 1856 - New York, 1943), a Serbian-American scientist, engineer and inventor, represent the foundation of new technical and technological breakthroughs that began at the end of the 19th century, and without which our everyday life would be unthinkable. The legacy of Nikola Tesla is located in his museum in Belgrade and present unique collection composed from archive documents, different items (personal and technical items) and library (monographies, periodical publications and newspaper clips). The number of original technical items from Tesla's legacy (295 in total) is finite and unchangeable. The collection of items from the field of mechanical engineering consists of 122 different museum artifacts from the following areas: turbo machines, tribology, speed measurement, length measurement, temperature measurement, measuring tools, accessories for technical drawing and writing, machine assemblies and elements, etc. The most numerous groups of objects consist of springs (coil-cylindrical, spiral strip), a total of 30 exhibits. Models of spiral cylindrical springs, depending on how they are loaded, are compression (8 pcs.) or tension type (14 pcs.). The aim of this paper is to present preserved models and to examine the physical-chemical and mechanical properties and contribute with additional knowledge to the Nikola Tesla legacy

Impact of climatic conditions of the area on wheat

The aim of this study was to analyze the influence of climatic conditions in the city of Leskovac, in the period from 2000 to 2008th year, the yield of wheat. This paper presents the average yield of wheat according to the mean monthly temperature and total precipitation during the vegetation period. So they separated two years ago (2003) when he achieved the lowest yield of wheat in the territory of Leskovac (2.4 t ha-1) and the 2004th years ago, when achieved the highest average yield in the period (3.7 t ha- 1). The average yield in the year with favorable schedule and rainfall, and average air temperature was higher by 1.3 t ha-1 of the unfavorable climatic conditions. Deficiency, poor distribution of rainfall, high average temperature, and temperature fluctuations during the growing negative impact on wheat yield. By choosing a variety that is more tolerant to drought, as well as quality and timely application of agro-technical measures can mitigate the adverse impact of climate conditions on the yield of wheat fields

EFFECTS OF IMPLEMENTATION OF CO-GENERATION IN THE DISTRICT HEATING SYSTEM OF THE FACULTY OF MECHANICAL ENGINEERING IN NIŠ

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 co-generation 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 Niš. 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

Hemangioma of the uterus

This paper presents a case of a patient with hemangioma of the uterus, which is one of the very rare localizations for this type of tumors. Hemangiomas are tumors that originate from blood vessels and are more often found on the skin or in the liver. No one has ever thought of its localization in the uterus until histopathological finding proves it. We presented a case of a 57 years old patient who was operated at the clinic for surgical oncology - department of gynecology of the Institute of Oncology Sremska Kamenica

Impact of climatic conditions of the area on wheat

The aim of this study was to analyze the influence of climatic conditions in the city of Leskovac, in the period from 2000 to 2008th year, the yield of wheat. This paper presents the average yield of wheat according to the mean monthly temperature and total precipitation during the vegetation period. So they separated two years ago (2003) when he achieved the lowest yield of wheat in the territory of Leskovac (2.4 t ha-1) and the 2004th years ago, when achieved the highest average yield in the period (3.7 t ha- 1). The average yield in the year with favorable schedule and rainfall, and average air temperature was higher by 1.3 t ha-1 of the unfavorable climatic conditions. Deficiency, poor distribution of rainfall, high average temperature, and temperature fluctuations during the growing negative impact on wheat yield. By choosing a variety that is more tolerant to drought, as well as quality and timely application of agro-technical measures can mitigate the adverse impact of climate conditions on the yield of wheat fields