Energy Efficiency Standpoint Research Articles

Enhanced magneto-convective heat transport in porous hybrid nanofluid systems with multi-frequency nonuniform heating

In high-performance thermal systems, convective heat transport is a critical phenomenon for sustainable operation from an energy efficiency standpoint. This study examines the convective heat transport dynamics of a hybrid nanofluid (aluminum oxide-copper–water nanofluid) under spatially varying nonuniform temperature conditions within a porous thermal system in the presence of a magnetizing field. The flow domain experiences nonuniform heating (following a half-sinusoidal profile) from both sidewalls and is cooled from the top, while the lower wall remains adiabatic. The flow domain is filled with a porous substance and a hybrid nanoliquid. The non-dimensional governing equations are derived and numerically solved using a finite volume method-based solver. To accurately capture thermal behavior, available experimental data on hybrid nanofluid thermophysical properties are utilized. The study analyzes significant control variables such as half-sinusoidal heating amplitude, frequency, and offset temperature, as well as flow control variables such as Darcy number (Da), modified-Rayleigh number (Ram), and Hartmann number (Ha). The analysis shows that non-uniform heating consistently enhances transfer by up to approximately 722% compared to uniform heating. The three temperature-controlling parameters (amplitude, frequency, and offset temperature) play a crucial role in enhanced heat transfer, and the higher their magnitudes, the higher the heat transfer. Heat flow dynamics between the heat source and the heat sink are well visualized through heat function and heatlines. Heat transfer is an increasing function of Ram and frequency, which is opposite to the rising Da or Ha. An optimum frequency at which thermal convection is maximum is about 70 for the considered range of Ram. Furthermore, mathematical correlations that combine control variables are developed for predicting heat transfer characteristics.

Efficiency of organic technologies of winter rye cultivation in Ukraine's Polissya in the context of climate change adaptation

In the conditions of the Polissya region of Ukraine, the cultivation of winter rye in organic farming is promising, but it is constrained by low crop yields. Therefore, the urgent task is to find ways to improve the efficiency of the fertilisation system of this traditional Polissya crop. The purpose of the study was to analyse the feasibility of using liquid complex fertilisers against the background of three fertilisation systems for organic and convection cultivation of winter rye in the conditions of Ukrainian Polissya. Field, laboratory and analytical, mathematical and statistical research methods were used. The results of a stationary experiment on light grey forest soil were analysed. It was found that the highest yield of winter rye was when grown using convection technology with a mineral fertilisation system – 4.2 t/ha, which provided an increase in grain yield of 1.07 t/ha or 34.4% compared to the control option. The use of organic technology based on organic and organo-mineral fertilisation systems provided a significantly smaller increase – 0.6 and 0.75 t/ha or 19.3 and 24.0%, respectively. However, the level of profitability for the mineral system decreased by 0.54 thousand UAH/tonne or 39.1%, net operating profit – by 1.6 thousand UAH/tonne or 26.0% compared to the organic fertilisation system. The latter was also better from the standpoint of energy efficiency. It is proved that double foliar top dressing with liquid organo-mineral fertilisers significantly increases the efficiency of the fertilisation system. In the conditions of the experiment, this was expressed in an additional increase in productivity by 0.47-1.16 t/ha, a reduction in the cost of production by 0.14-0.36 thousand UAH/ha, an increase in profitability by 19.3-48.3%, energy efficiency – by 0.14-0.71, and the plasticity of the crop to dry conditions during the growing season. The findings can become the basis for improving the fertilisation system for organic cultivation of winter rye, which would ensure the formation of sustainable yields by minimising the impact of stress factors (dry periods during the growing season) and increase the economic efficiency of grain production in agricultural enterprises of various forms of ownership

The unexpected effects of daylight-saving time: Traffic accidents in Mexican municipalities

Objective: Several countries implement the DST policy for energy saving purposes. However, by artificially changing the distribution of daylight, this practice can have unforeseen effects. The objective of this work is to measure the impact of DST on road accidents in Mexico.Methodology: Using hourly data, two empirical strategies are used: regression discontinuity (RDD) and difference-in-differences (DD).Results: The main finding is that DST significantly reduces the total number of accidents in metropolitan areas. However, there are no clear effects on the number of fatal accidents.Limitations/Implications: DST is implemented regardless of demand conditions and the economic cycle. Seasonal changes in prices and production can be difficult to capture before and after the time change. We introduce variables that mitigate the (potential) identification problem.Originality: this is the only study measuring these effects in Mexico (and one of the few with data from emerging countries).Conclusions: The DST is currently being discussed in Mexico, and our study offers a more comprehensive evaluation of the policy, not only from the standpoint of energy efficiency.

Энергетическое обоснование выбора системы кондиционирования воздуха для административно-торгового центра

Introduction. The air conditioning system is the main consumer of electricity inside office and shopping buildings. The coo­ling needs arise inside such buildings all over the year due to high amounts of heat emitted by people and equipment (computers, office equipment, cash registers), solar radiation (the envelopes of the majority of these buildings have continuous glazed facades) and sources of artificial lighting. A conventional cooling system has a compressor and condensers. The most important step towards an optimized and low-energy cooling system is the abandonment of compressor and condensers; in addition, the cold extracted from the outdoor air, is used in the system. This cooling technique is called an atmospheric co­oling system. The climatic features of Russia allow for a large-scale application of the cooling technology that uses natural cold. However, for a start, a decision was made to focus on a central region of the Russian Federation, namely, Moscow, rather than any northern areas of the country. Materials and methods. The problem is solved by the calculation method applied to the case of a 35-storey office building in Moscow. Various outdoor temperature options were considered as the bases for a transition to an atmospheric cooling system. The co-authors also compare different installation options for dry coolers, which in turn affect the routing length of refrigeration circuits. The annual demand for cold is calculated for all analyzed options. Results. Some results are presented in the form of tables of annual energy consumption by different types of air cooling systems. Conclusions. The co-authors have found that the location of dry coolers strongly affects the power consumption by a co­oling system. Power consumption by cooling systems was analyzed, and it was found out that transition to machine refrigeration at the higher outdoor temperature of +8 °C is more efficient from the standpoint of energy efficiency than the same transition at +5 and 0 °C.

IDIO: Orchestrating Inbound Network Data on Server Processors

Network bandwidth demand in datacenters is doubling every 12 to 15 months. In response to this demand, high-bandwidth network interface cards, each capable of transferring 100s of Gigabits of data per second, are making inroads into the servers of next-generation datacenters. Such unprecedented data delivery rates on server endpoints raise new challenges, as inbound network traffic placement decisions within the memory hierarchy have a direct impact on end-to-end performance. Modern server-class Intel processors leverage DDIO technology to steer all inbound network data into the last-level cache (LLC), regardless of the network traffic’s nature. This static data placement policy is suboptimal, both from a performance and an energy efficiency standpoint. In this work, we design IDIO , a framework that—unlike DDIO—dynamically decides where to place inbound network traffic within a server’s multi-level memory hierarchy. IDIO dynamically monitors system behavior and distinguishes between different traffic classes to determine and periodically re-evaluate the best placement location for each flow: LLC, mid-level (L2) cache or DRAM. Our results show that IDIO increases a server’s maximum sustainable load by up to $\sim$ ∼ 33.3% across various network functions.

The methodology for studying the process of destruction of solid bulk materials from the standpoint of energy efficiency and quality of the final product

The methodology for studying the process of destruction of solid bulk materials from the standpoint of energy efficiency and quality of the final product

Energy efficiency is the most important indicator of the quality of food grinders

A brief analysis of the methods of grinding technological raw materials from the standpoint of energy efficiency has been performed. Studies show that cutting (grinding) the feedstock into pieces of a certain size is the most energy-intensive. Existing designs of cutting elements of grinding mechanisms (cutting blade, cutting edge) are not optimal from the standpoint of energy efficiency. For example, the cutting blade in the working hole has a taper angle of 90°, and the taper angle of the cutting blade on the blades of the movable knife is also in the range of 80–90°. It is proposed to make the sharpening angles of the cutting blades on the blades of a movable knife equal to 5–8°. In addition, the blades of such a knife should have the shape of a classic wedge in all cross sections. Reducing the angle of sharpening of the cutting blade in the working hole of the grill to such values does not succeed in terms of design features (in particular, without violating transparency indicators). The reserves of reducing the angle of sharpening of the cutting blade in the working hole are shown (this angle can be less than 90°). The performed studies indicate that the smaller the energy costs for grinding the feedstock, the less it is rubbed and squeezed out of the holes of the grate. It can be assumed that the organoleptic properties did not deteriorate after grinding (but remained). The lower the transparency of the lattice, the grinding process is more energy-consuming. The smaller the sharpening angles of the cutting blades of the knives, the more energy-efficient the grinding process. The worse the quality of the crushed raw materials, for example, meat, which is characterized by the excessive presence of connective and cartilage tissues, films, etc., the more energy-efficient is the grinding process with knives with cutting blades with minimal sharpening angles.

Modeling of transport processes in the cigarette principle combustion furnace

This paper presents numerical and experimental investigations of complex and interrelated physical and chemical phenomena that occur during combustion of baled soybean residue in the furnace with the cigarette type of combustion. The result of comprehensive research is reactive flow model of biomass combustion inside furnace. Model is described by set of PDE which define momentum, heat and mass transfer processes in porous and fluid system. The main aim of developed CFD model is numerical simulation of combustion process inside the cigarette furnace. It is also used to provide deeper insight in complex processes occurring during biomass combustion. Verification of proposed numerical model was performed through comprehensive experimental tests on the experimental-industrial plant of 1.5 MW boiler for heating the greenhouses in the Agricultural Corporation in Belgrade. The tests included measurement of flow rate and air and flue gas temperature input and output values on the furnace that are taken as the boundary conditions of the developed model. Comparison of the experimental results shows satisfactory agreement with numerical results (the maximum relative deviation of calculation and measurement temperatures are 10-45%), therefore the developed mathematical model could be used to analyse the effects of structural and parametric (fuel composition, power rate, air excess etc.) changes of the facility, from the standpoint of energy efficiency and ecology.

System-Level Modeling and Optimization of the Energy Efficiency in Cellular Networks—A Stochastic Geometry Framework

In this paper, we analyze and optimize the energy efficiency of downlink cellular networks. With the aid of tools from stochastic geometry, we introduce a new closed-form analytical expression of the potential spectral efficiency (bit/sec/m2). In the interference-limited regime for data transmission, unlike currently available mathematical frameworks, the proposed analytical formulation depends on the transmit power and deployment density of the base stations. This is obtained by generalizing the definition of coverage probability and by accounting for the sensitivity of the receiver not only during the decoding of information data, but during the cell association phase as well. Based on the new formulation of the potential spectral efficiency, the energy efficiency (bit/Joule) is given in a tractable closed-form formula. An optimization problem is formulated and is comprehensively studied. It is mathematically proved, in particular, that the energy efficiency is a unimodal and strictly pseudo-concave function in the transmit power, given the density of the base stations, and in the density of the base stations, given the transmit power. Under these assumptions, therefore, a unique transmit power and density of the base stations exist, which maximize the energy efficiency. Numerical results are illustrated in order to confirm the obtained findings and to prove the usefulness of the proposed framework for optimizing the network planning and deployment of cellular networks from the energy efficiency standpoint.

System-Level Modeling and Optimization of the Energy Efficiency in Cellular Networks—A Stochastic Geometry Framework

In this paper, we analyze and optimize the energy efficiency of downlink cellular networks. With the aid of tools from stochastic geometry, we introduce a new closed-form analytical expression of the potential spectral efficiency (bit/sec/m$^2$). In the interference-limited regime for data transmission, unlike currently available mathematical frameworks, the proposed analytical formulation depends on the transmit power and deployment density of the base stations. This is obtained by generalizing the definition of coverage probability and by accounting for the sensitivity of the receiver not only during the decoding of information data, but during the cell association phase as well. Based on the new formulation of the potential spectral efficiency, the energy efficiency (bit/Joule) is given in a tractable closed-form formula. An optimization problem is formulated and is comprehensively studied. It is mathematically proved, in particular, that the energy efficiency is a unimodal and strictly pseudo-concave function in the transmit power, given the density of the base stations, and in the density of the base stations, given the transmit power. Under these assumptions, therefore, a unique transmit power and density of the base stations exist, which maximize the energy efficiency. Numerical results are illustrated in order to confirm the obtained findings and to prove the usefulness of the proposed framework for optimizing the network planning and deployment of cellular networks from the energy efficiency standpoint.

Uplink Spectral Efficiency Analysis for a Massive MIMO Primary Network

Faster development of smart electronic devices in recent years along with significant increase in demanding higher data rates has made cognitive radio networks (CRNs) to be taken into consideration as a promising technology. A CRN has the ability to increase spectral efficiency (SE) of communication systems by opportunistically using unused spectrums. Furthermore, Massive multiple-input multiple-output is a major candidate to be used in next generation cellular systems in light of its great capabilities to improve system performance from spectral as well as energy efficiency standpoint. In this paper, we propose a CRN whose base station, as well as the primary base station (PBS) are equipped with large numbers of antennas. We derive closed-form expressions for SE in the uplink of primary users for three different scenarios. In these scenarios perfect and imperfect channel state information are considered separately. In addition, the impact of pilot contamination due to the correlation among users’ pilot signals on sum SE of primary network is examined. For the first two scenarios, minimum number of antennas (MNA) at the PBS to achieve a specified SE is derived in a closed-form expression. MNA is analyzed numerically for the third scenario.

住宅用エアコンのCOPの現状とAPFの地域特性に関する研究

A conventional selection criterion of room air conditioners based on rated performance is considered suboptimal from the standpoint of energy efficiency. In order to help consumers evaluate energy performance, annual performance factor (APF) was introduced in the 2005 revision of JIS C 9612. However, APF assumes thermal environment of Tokyo, which makes regional deviation of APF remain unknown. In the present study, rated coefficients of performance (COPs) and market prices of year 2012 models of air conditioners are collected. From the collection, APFs are calculated at nine representative cities in Japan to quantify regional characteristics of APF.

Modeling of synchronous machines based on the interference of harmonics on power systems feeding nonlinear loads

The electricity sector has concerns about global energy use, more rational and optimized in view the difficulties of expanding the energy supply due to lack of technological resources and even financial, but emphasizing the sources. We present the concern with the generation of electricity through the synchronous machines, operating on electric power systems, where the waveforms of voltages and currents are no longer sine waves. Due to be feeding nonlinear loads, which are responsible for the generation of harmonic interference, which has grown tremendously the use of power electronics for building equipment and systems. The losses presented in synchronous machines according to the interference of harmonics resulted in the order of about 8%. These losses were due to the increases of the losses in copper, iron and additional torque, contrary to the fundamental torque. From the standpoint of energy efficiency for generating the same amount of energy that was generated in the month before the pollution sources of harmonics. There are today, the need to increase the fuel is at least 10%.

Urban noise and transport as a base of environmental quality strategy.

In recent years, urban noise has become an essential element in the environmental analysis since the study allows for a support tool for the analysis of environmental quality in the cities. Additionally, residents of large cities are demanding more options for transportation improvements from the standpoint of energy efficiency, low emissions of pollutants, and strategic routes, among others. This proposal presents the results of a diagnosis of urban noise on an avenue with high traffic flow in the city of Guadalajara, and analyzed during the construction of a rapid rail transit preferential and once it is running. The results of the noise levels actually indicate that the entry of a fast and environmental friendly bus significantly reduces noise emissions and contributes to the acoustic quality of the avenue with the benefits it represents for the people.

Urban housing & energy efficiency: a pollution prevention opportunity

Abstract In 1999, the New York Power Authority (NYPA) received the annual Governor's Award for Pollution Prevention for its Energy Efficiency Refrigerator Replacement Program, conducted in cooperation with the New York City Housing Authority (NYCHA). There are over 180,000 refrigerators in operation at NYCHA residences. In this article the authors describe how NYPA offered to design, finance and implement a program to replace inefficient refrigerators with more efficient models, recouping the cost of the program through energy savings. NYPA worked in partnership with major appliance manufacturers to develop refrigerators that fit the NYCHA space requirements while providing sufficient energy savings to pay for the program. In addition, refrigerant gas, compressor oil, mercury switches, PCB- and non-PCB capacitors, and metals are all recycled at a dedicated facility under the program; the shipping containers from the new refrigerators are also recycled. Since program inception, almost 48,000 refrigerators have been replaced, weighing an estimated 8.5 million pounds. To date, the program has recycled approximately 14,000 pounds of CFC-12 gas, 215,000 pounds of aluminum, 36,000 pounds of copper, and eight million pounds of steel. From an energy efficiency standpoint, energy consumption has been reduced by 62,000 MWH, which has eliminated air emissions totaling ninety-five tons of SO2, seventy-eight tons of NOx and 52,000 tons of CO2 (using metropolitan New York generation profiles). Likewise, partnerships have been developed with the US Department of Housing and Urban Development and the U.S. Department of Energy.

Energy minimised v. cost minimised alternatives for the US beef production system

A model of the US beef production system has been utilised to project tradeoffs between minimised cost of feeding and minimised fossil energy use to produce amounts of beef similar to 1976 consumption. Cost minimisation approaches the present actual beef production system, but suggests increases in bull feeding and the use of silage and grass finishing of cattle. Energy minimisation indicated energy savings could exceed the equivalent of 240 million barrels of crude oil/year. If energy costs increased three times the 1979 levels, energy and cost minimised solutions appear equivalent. USDA ‘Choice’ grade has been a cost effective strategy, even without consideration of price differentials for the higher quality beef. However, maintenance of current levels of ‘Choice’ beef production does not appear optimal from an energy efficiency standpoint. The model results for energy minimisation suggest an increase in grass finishing and feeding of large bulls, rather than steers, practices which could further reduce fossil fuel inputs, but would result in less ‘Choice’ quality meat. Each increase in energy efficiency in the beef system (other than simple elimination of waste) may be anticipated to have a cost penalty over current practice, given constant or moderately increasing energy costs. However, if energy prices were to reach three times their present level, the model suggests that national cost minimisation would require more energy efficient production systems, and the production of the higher quality beef grades would increase in relative expense. The beef industry does not, at present, minimise energy input because energy's apparent real cost has been low compared with other inputs.