Енергетски пасивни објекти за домување

Пристапот до енергетски ефикасни и економски прифатливи енергетски ресурси е многу важен предуслов за брз економски развој на една земја. Ограничените енергетски ресурси и еколошките проблеми кои се јавуваат како резултат на употребата на различни извори на енергија, пред сé јаглен, сурова нафта, природен гас, но и електрична енергија произведена со користење на овие примарни енергетски извори, мора сериозно да се има во предвид. Во овој труд посебно внимание е посветено на ефикасното искористување на енергијата на примарните извори, вклучително и електрична енергија, особено за греење и ладење, преку развој на современ концепт на заштеда на енергија во приватното домување. Со изградба и користење на т.н. пасивни енергетски објекти, како и со внимателно планирање, лоцирање и изградба на такви објекти во комбинација со рационално користење на енергијата, може да се постигне висок степен на заштеда на енергија, намалување на потрошувачката на горивата, зачувување на примарните енергетски извори и значително намалување на вкупните трошоци за енергија

Simulation of Screening Current Reduction Effect in REBCO Coils by External AC Magnetic Field

Second-generation high-temperature superconducting (HTS) tapes have been examined for applications, such as NMR, MRI, and accelerators. Each of these applications requires a precise magnetic field profile. However, screening currents induced while charging an HTS magnet degrade its magnetic field quality. Techniques to reduce the screening current effect have been proposed in the literature. One of the means to reduce screening currents is to apply an AC magnetic field using a “shaking magnet.” The shaking effect enhances the quality of magnetic field by allocating the screening currents inside HTS tapes. Although some experiments to study the shaking field effect were reported, the current distribution inside HTS tapes has not yet been clarified by simulation. This paper presents the simulation results for an AC magnetic field applied to a REBCO tape to reduce the influence of screening currents. In addition, we investigated the influence of the angle of applied AC magnetic field at the magnet center. The area of negative current density is also shown. From the simulation results, we conclude that a shaking field applied at an angle between 10 and 30 deg. is effective to reduce the screening current effect

Високо ефикасни transnorm (TN) асинхрони мотори

Повеќе од 60% од целокупното искористување на електричната енергија отпаѓа на нејзино претворање во механичка енергија за потребните на различни индустриски погони, најчесто со користење на асинхрони мотори. Од друга страна, порастот на цената на енергенсите на глобално ниво, условува потреба од континуиран развој, сé со цел на замена на старите асинхрони мотори со конвенцијална изведба, со нови, современи и пред сé силно енергетски ефикасни асинхрони мотори, кои можат да работат како на низок така и на висок напон. Тенденцијата за постојано намалување на нивото на загуби како и значително подобрениот начин на одведување на топлината создадена при нивната работа, допринесуваат новата класа на мотори да се изработува според високите стандарди за енергетска ефикасност за овој тип на електрични машини, особено стандардот IEC 60034. Во овој реферат, накратко ќе бидат обработени основните карактеристики на т.н. transnorm (TN) асинхроните мотори за низок и висок напон кои произлегуваат од нивниот специфичен дизајн и конструктивна изведба, како и придобивките од замена на класичните асинхрони мотори со соодветни современи transnorm асинхрони мотори, како од технички така и од инвестициско-економски аспект

Sustainable tourism and hotel management in Macedonia through the use of renewable energy sources

This study aimed to investigate the nature of energy applied in hotel industry in Macedonia. It explored the indicators for resources application in three, four and five star hotels. The data were collected by means of an online survey conducted among 45 managers and department supervisors. It is found that large number of hotels lack measures to reduce the conventional energy use and replace it with renewable sources of energy. Considering the fact that energy use is a substantial cost factor, the modest and restricted application of geothermal energy, biofuels and photocell lightening is extremely alarming for achieving sustainable tourism development. The study concludes that Macedonian hotels although being fully aware of importance of energy efficiency concept, it is not their managerial priority. It further pointed out that the development and operation of sustainable hotels requires properly planned and designed environmental protection practices. Finally, the study recommends that instead of being driven by increased number of tourists regardless the environmental concern, Macedonian hotels should pay attention and become eco-friendly and be focused on applying environmental oriented practices. At the same time, the research poses new challenges that urgently need to be brought to hotel management in the line of achieving sustainable tourism development

Assessment of the energy efficiency practices in the hotel industry

The study evaluates the application of the energy efficiency practices in the hotel industry. It explores the determinants of energy consumption in three and four-star hotels in Macedonia. The research investigates the impacts of several elementary components of the energy practices, by measuring the current level of influence. The data were obtained by an online survey conducted among managers and processed by descriptive statistics and factor analysis. The results point out some alarming facts, i.e. these types of hotels lack policies on general environmental issues. The managers pose some high awareness of the benefits produced by this concept, which is due to the highly positive perception of the environmental protection. The lack of subsidies at local and national level is identified as the most profound constraint along with the technical limits of the hotel facilities and costs increase. The study recommends some new approaches in challenging the hotel industry to decrease the operating costs and suggests that managers are in need for better understanding of the importance of the energy efficiency practices

FEMM како едукативна алатка за решавање на проблеми од електромагнетизам

Во овој труд претставена е употребата на софтверскиот пакет FEMM како комплетна софтверска алатка за решавање на електромагнетни проблеми за едукативни цели. FEMM (Finite Element Method Magnetics) е бесплатен софтверски пакет за симулација и анализа на магнетно и електростатичко поле, топлинско поле и проток на индуцирани струи. Симулациите се вршат со користење на Методот на конечни елементи што на студентите им овозможува да анализираат лесно и брзо разни проблеми од овие области и визуелно и графички да ги анализираат и презентираат добиените нумерички решенија. Со споредба на нумерички добиените решенија студентите може да ги потврдат резултатите кои аналитички ги добиваат со помош на математички пресметки

Upgrading of the Spilje HPP

Total generation capacity of the electric power system of Republic of Macedonia is 1444 [MW], out of which 1010 [MW] are installed in TPP and only 434 [MW] in HPP. The hydropower production is subordinate to the thermal one with a specific and highly defined role in the whole electricity sector. HPP Spilje usually operates so the available water storage is used rationally and the overflows are minimal. This was achieved by enlargement of the water storage useful area as a result of the decreasing the minimal operation level. This paper deals with some additional possibilities for further upgrading of the installed capacity of this power plant for achieving better operational performances

Fast Magnetic Flux Line Allocation Algorithm for Interactive Visualization Using Magnetic Flux Line Existence Probability

The visualization of magnetic flux lines is one of the most effective ways to intuitively grasp a magnetic field. The depiction of continuous and smooth magnetic flux lines according to the magnetic field is of paramount importance. Thus, it is important to adequately allocate the distribution of magnetic flux lines in the analyzed space. The authors have already proposed two methods of determining the allocation of magnetic flux lines in 3-D space. However, both methods exhibited a long computation time to determine the allocation of magnetic flux lines. For solving this problem, in this paper, we propose a new improved method for correct allocation of magnetic flux lines in 3-D space with modest computational cost. The main advantages of this method are shorter computation time, correct allocation of the magnetic flux lines, and especially short computation time for visualization of magnetic flux lines when changes in the number of depicted flux lines is requested

Energy efficiency improvements of the industrial natural gas furnace using a heat recovery system

Enterprises are strongly focused on the implementation of various energy efficiency measures for optimizing their existing power systems, such as power generation engines, compressed air systems, lighting, production and distribution of hot water and steam, heating and cooling, energy recovery and recuperation systems, etc. The potential for energy efficiency can be divided mainly into two groups. Most of the measures are determined based on technical solutions, but several measures relate to human psychology and the inclusion of changes in the daily habits of users. Most energy efficiency measures are acceptable from a financial point of view and offer a relatively quick return on investment, but some are financially more intense and with a longer period of return of the investment. This project describes a combined project for improvement of energy efficiency based on the implementation of an energy recovery system from exhaust gases on industrial furnaces, which use natural gas as primary energy fuel and automatic regulation and control of fan speed depending on the temperature of the product. The basic idea of this project is to re-use the energy from exhaust gasses which was initially released freely into the atmosphere thought chimney by the development of a new heat recuperation system. Energy gained from the recuperation process was re-used in the same furnace as a pre-heat fresh air improving the energy efficiency of the same furnace. Additionally, the authors explained the regulation and control of the cooling fans with VFD speed controllers based on the online measurement of the product temperature. The implementation of both ideas could result in ignificant energy savings with an ROI period of less than 1 year

Towards Pollution Reductions and Decarbonization of District Heating Systems

Global climate change significantly affects the energy usage of district heating and cooling systems, especially when planning new operations or maintaining existing ones. These systems typically rely on fossil fuels as their energy source and are often located in densely populated areas, leading to a significant negative impact on air quality. The pollutants they emit, such as CO2, SO2, NOX, and dust particles, vary depending on the type of fossil fuel used, with coal being the worst and natural gas representing the least hazardous option. Given the growing emphasis on renewable energy sources like geothermal, solar, and wind power, and the availability of energy-efficient technologies, current research aims to develop new technologies for district heating systems that can reduce their negative environmental impact, lower pollutant emissions, and facilitate the decarbonization of this energy sector. In recent years, the city of Skopje has faced severe environmental issues, particularly during the winter season. Apart from city traffic, the underdeveloped district heating system, which only covers 40% of the city’s heating needs, is a major contributing factor. The remaining heating comes from conventional sources such as wood, wooden residuals, or wooden pellets, significantly worsening air quality and citizens' living standards. Moreover, due to lower economic standards and high costs of heat energy from district heating companies, many users have switched to alternative heating sources like air conditioning, heat pumps, or other environmentally unsuitable energy sources. This paper focuses on addressing the problems and potential solutions for transitioning the district heating system to a more sustainable model. Starting from the now outdated 1st and 2nd generation district heating systems, the primary goal is to facilitate a smooth transition from the widely accepted 3rd generation to the improved 4th generation of district heating systems. The district heating systems in Skopje currently fall between the 2nd and 3rd generation and urgently require transformation towards the fourth generation. While some countries, such as Denmark and the UK, propose moving towards the fifth generation of district systems, it appears that the fourth generation still offers significant advantages over the proposed fifth generation, considering the existing heating systems, economic factors, and expected benefits