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Fluorescence of CdSe/ZnS quantum dots in toluene: effect of cyclic temperature
摘要： As an increasingly popular green building technology, natural ventilation (NV) is an effective solution for better thermal comfort and lower HVAC system energy consumption. However, to achieve NV’s full potential in practice, it is critical to control windows and HVAC systems. Three main types of control schemes are examined in this study: spontaneous occupant control, informed occupant control, and fully automatic control. Five representative climates, ranging from hot, temperate, to severely cold, are tested for the effectiveness of each control scheme. The results confirmed the superior performance of the fully automatic system, especially with the model predictive control algorithm, which demonstrates a cooling energy saving of 17%–80%, with zero discomfort degree hours. Neither the informed or spontaneous occupant controls are able to maintain the indoor temperature within the comfort range at all times. In particular, the informed occupant operation following the fixed-schedule four-times-daily signals shows the worst thermal control capacity and leads to 1500–4000 discomfort degree hours. In terms of energy performance, the informed occupant control, by following the heuristic control signals, shows the least energy savings and even indicates energy waste in some scenarios. Based on the study’s results, it is recommended to either adopt the fully automatic natural ventilation control system to achieve maximum energy-saving potential or allow occupant autonomy for natural ventilation controls to achieve a lower budget for initial installation and maintenance cost.
关键词： Occupant behavior,Natural ventilation,Building energy efficiency,Advanced building control
更新于2025-09-11 14:15:04
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Coloured Building Integrated Photovoltaics: Influence on Energy Efficiency
摘要： Building integrated photovoltaics (BIPV) has attracted increased commercial interest in recent years due to a growing focus on efficient utilization of land area and local renewable energy generation. Aesthetic aspects must be considered when photovoltaic panels are applied as building elements. Colours can be added by reflecting some of the sunlight that otherwise could have been utilized for electricity generation. Reflectance spectra of commercial solar cell modules have been measured and analysed. Relative efficiency loss caused by the reflected solar radiation energy has been calculated. The calculated losses in efficiency based on measured spectra have been compared to model spectra with colour coordinates corresponding to RAL colours as well as more idealized monochromatic spectra. The analysis shows that the most important colour parameter affecting loss is the lightness. The second most important parameter is the hue of the colour, with green-yellow colours having the lowest loss, and pink colours resulting in the highest loss, when colours with the same lightness are compared. A Colour Performance Index (CPI) given by luminous reflectance divided by relative loss has been proposed as a figure of merit, thus allowing for a useful comparison of colours with different lightness.
关键词： Building integrated photovoltaics,Solar cell,Colour,Energy efficiency,BIPV
更新于2025-09-11 14:15:04
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[Communications in Computer and Information Science] Smart Cities, Green Technologies, and Intelligent Transport Systems Volume 921 (6th International Conference, SMARTGREENS 2017, and Third International Conference, VEHITS 2017, Porto, Portugal, April 22-24, 2017, Revised Selected Papers) || The SAGITTA Approach for Optimizing Solar Energy Consumption in Distributed Clouds with Stochastic Modeling
摘要： Facing the urgent need to decrease data centers’ energy consumption, Cloud providers resort to on-site renewable energy production. Solar energy can thus be used to power data centers. Yet this energy production is intrinsically fluctuating over time and depending on the geographical location. In this paper, we propose a stochastic modeling for optimizing solar energy consumption in distributed clouds. Our approach, named SAGITTA (Stochastic Approach for Green consumption In disTributed daTA centers), is shown to produce a virtual machine scheduling close to the optimal algorithm in terms of energy savings and to outperform classical round-robin approaches over varying Cloud workloads and real solar energy generation traces.
关键词： Renewable energy,Scheduling,On/OFF techniques,Distributed clouds,Data centers,Energy efficiency
更新于2025-09-10 09:29:36
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A New Design Technique for Sub-Nanosecond Delay and 200 V/ns Power Supply Slew-Tolerant Floating Voltage Level Shifters for GaN SMPS
摘要： Dual-output gate drivers for switched-mode power supplies require low-side reference signals to be shifted to the switch-node potential. With the move to ultra-fast switching GaN converters, there is a commercial need to achieve switch-node slew-rates exceeding 100 V/ns, however, reported level shifters do not simultaneously achieve the required power supply slew immunities and sub-ns propagation delays. This paper presents a novel design technique to achieve the first floating voltage level shifters that deliver slew-rate immunities above 100 V/ns and sub-ns delay in the same circuit. Step-by-step transistor-level design methods are presented. This technique is applied to improve a reported level shifter, and experimentally validated by fabricating this level shifter in a 180 nm high-voltage CMOS process. The final level shifter has zero static power consumption, and is shown to have a sub-nanosecond delay across the whole operating range, a 200 V/ns positive power-rail slew tolerance, and infinite negative slew tolerance. The measured propagation delay decreases from 722 ps with the floating ground at ?1.5 V, to 532 ps for a floating ground of 45 V, and the power consumption is 30.3 pJ per transition at 45 V. It has a figure of merit of 0.06 ns/(μmV), which is an 1.7× improvement on the next best reported level shifter for this type of application.
关键词： slew level shifter,energy efficiency,GaN,Area efficient,tolerance,high speed,floating voltage low power,gate driver
更新于2025-09-10 09:29:36
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A comprehensive assessment of alternative absorber-exchanger designs for hybrid PVT-water collectors
摘要： In this paper, 26 alternative absorber-exchanger designs for hybrid PV-Thermal (PVT) solar collectors are proposed and compared against a reference-case, commercial sheet-and-tube PVT collector. The collectors involve different geometric design features based on the conventional sheet-and-tube configuration, and also on a newer flat-box structure constructed from alternative polymeric materials with the aim of maintaining or even improving heat transfer and overall (thermal and electrical) performance while achieving reductions in the overall weight and cost of the collectors. The main contributions of this research include: (i) the development and validation of a detailed 3-D computational finite-element model of the proposed PVT collector designs involving multi-physics processes (heat transfer, fluid dynamics and solid mechanics); (ii) results from comparative techno-economic analyses of the proposed PVT designs; and, (iii) further insights from thermal stress and structural deformation analyses of the proposed collectors, which are crucial for ensuring long lifetimes and especially important in the case of polymeric collectors. The results show that, in general, the flat-box designs (characterised by a thin absorber plate) are not sensitive to the flow-channel size or construction material, at least within the range of investigation. A PVT collector featuring a polycarbonate (PC) flat-box design with 3 × 2 mm rectangular channels appears to be a particularly promising alternative to commercial PVT collectors, achieving a slightly improved thermal performance compared to the reference case (with a 4% higher optical efficiency and 15% lower linear heat-loss coefficient), while also lowering the weight (by around 9%) and investment cost (by about 21%) of the collector. The structural analysis shows that the maximum von Mises stress experienced in the absorber-exchanger of the PC flat-box collector is considerably lower than that in the copper sheet-and-tube collector (< 13% vs. 64% of the material’s yield stress), which is attributed to the larger thermal expansion of the PC absorber-exchanger, that leads to lower stresses. Therefore, the proposed PC flat-box design is not expected to suffer higher strains than the commercially-available PVT collector.
关键词： Cost savings,Hybrid PVT collector,Solar energy,Efficiency,Absorber-exchanger,Structural analysis
更新于2025-09-10 09:29:36
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Show me (more than) the money! Assessing the social and psychological dimensions to energy efficient lighting in Kenya
摘要： Despite economic, social and environmental benefits, the uptake of energy-saving compact fluorescent lamp light bulbs (CFLs) in Kibera, an informal settlement in Nairobi, remains low. We conducted a randomized controlled field experiment involving 651 Kibera residents assessing whether the joint impact of monetary incentives and behavioral interventions (pre-commitment and simplified information highlighting CFL benefits) could increase CFL uptake. A monetary incentive covering the incremental cost of a CFL compared to an incandescent bulb positively impacted uptake. However, adding simplified information more than tripled the impact of the monetary incentive alone, resulting in a remarkable uptake rate of about 84%. While a post endline survey conducted two years following the administration of the randomized control trial does not find lasting effects, this paper provides evidence for additional behavioral hypotheses in developing countries, also assessing the contribution of intelligence and measured discount rates to account for potential household present bias. It is to date the only intervention of its type that explores the extent to which behavioral interventions can complement monetary incentives.
关键词： Energy efficiency,Randomized controlled field trial,Behavioral intervention,Africa
更新于2025-09-10 09:29:36
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Charge transient behaviour and spectroscopic ellipsometry characteristics of TiN/HfSiO MOS capacitors
摘要： A combination of two powerful techniques, namely, charge Deep level transient spectroscopy and spectroscopic ellipsometry is employed on atomic layer deposited Si-metal oxide semiconductor capacitors (MOSCAPs) to investigate the energy ef?ciency of the physical process. Ultra-thin TiN/HfSiO acted as gate-dielectric stack on Si substrate was carefully subjected to rapid thermal processing and subsequent spectroscopic measurements to determine the transient behaviour of charges and electro-optical characteristics. Some key parameters such as trap concentration, activation energy required to surmount the traps, capture cross section, refractive index and extinction coef?cient are found to play an important role in order to assess the energy ef?ciency of the devices both in terms of post-process quality of the retained surface and residual ef?ciency of the process by virtue of dynamics at atomistic scales. The results may provide a useful insight to the Si manufacturing protocols at ever decreasing nodes with desirable energy ef?ciency.
关键词： energy efficiency,charge Deep level transient spectroscopy,MOSCAPs,spectroscopic ellipsometry,TiN/HfSiO
更新于2025-09-10 09:29:36
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Efficient solar-driven electrocatalytic CO2 reduction in a redox-medium-assisted system
摘要： Solar-driven electrochemical carbon dioxide (CO2) reduction is capable of producing value-added chemicals and represents a potential route to alleviate carbon footprint in the global environment. However, the ever-changing sunlight illumination presents a substantial impediment of maintaining high electrocatalytic efficiency and stability for practical applications. Inspired by green plant photosynthesis with separate light reaction and (dark) carbon fixation steps, herein, we developed a redox-medium-assisted system that proceeds water oxidation with a nickel-iron hydroxide electrode under light illumination and stores the reduction energy using a zinc/zincate redox, which can be controllably released to spontaneously reduce CO2 into carbon monoxide (CO) with a gold nanocatalyst in dark condition. This redox-medium-assisted system enables a record-high solar-to-CO photoconversion efficiency of 15.6% under 1-sun intensity, and an outstanding electric energy efficiency of 63%. Furthermore, it allows a unique tuning capability of the solar-to-CO efficiency and selectivity by the current density applied during the carbon fixation.
关键词： solar-driven,electric energy efficiency,solar-to-CO photoconversion efficiency,redox-medium-assisted system,electrocatalytic CO2 reduction
更新于2025-09-09 09:28:46
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Evaluation of Photoelectric Characteristics of a Volume DBD Excited by Power Density Modulation
摘要： Photoelectric characteristics are an important reference for high-voltage discharges and are closely related to the excited mode of the high-voltage source. In this paper, we built a large-scale volume dielectric barrier discharge (DBD) system, which is composed of multilayer parallel-plate DBD electrodes and is excited by a high-voltage source in the power density modulation (PDM) mode. Subsequently, we analyzed the applied energy equation and evaluated the DBD systems photoelectric characteristics. The results show that the energy values of different applied voltage cycles during a PDM period exhibit significant differences. However, the average energy in a PDM period is approximately constant. Moreover, the equivalent capacitance of the DBD cell is a function of both the applied voltage and energy density. For the DBD cell, with the increase in both the applied voltage and energy loaded on the DBD cell, the total equivalent capacitance (C) is approximately constant, the dielectric capacitance (Cd) increases exponentially and decreases linearly, while the discharge gap capacitance (Cg) decreases and increases in the same cases. In addition, the relative intensities of the discharge emission increase and the energy efficiency ratios of the relative photoquantum yield of active species decline with the increase in both the applied voltage and energy density loaded on the DBD cell. The experimental results have been analyzed by evaluating the influence of the electrical parameters, and the underlying physical principles have been discussed. This paper clearly demonstrates that the photoelectric characteristics of the DBD reactor are significantly influenced by both the applied voltage and energy density, thus providing helpful insights into the energy evaluation and application of high-voltage discharges.
关键词： Applied energy,power density modulation (PDM),photoelectric characteristics,relative photo-quantum yield,energy efficiency ratio (EER)
更新于2025-09-09 09:28:46
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[Advances in Intelligent Systems and Computing] Image Processing and Communications Challenges 10 Volume 892 (10th International Conference, IP&C’2018 Bydgoszcz, Poland, November 2018, Proceedings) || Interference-Aware Virtual Machine Placement: A Survey
摘要： In order to maintain energy e?ciency and optimize resource utilization in cloud datacenters, cloud providers adopt virtualization technologies as well as server consolidation. Virtualization is the means used to achieve multi-tenant environments by creating many virtual machines (VMs) on the same physical machine (PM) in a way that they share same physical resources (e.g. CPU, disk, memory, network I/O, etc.). Server consolidation consists of placing as much as possible VMs on as less as possible PMs, in the aim of maximizing idle servers and then minimize the energy consumption. However, this vision of server consolidation is not as simple as it seems to be. Hence, it is crucial to be aware of its emerging concerns, such as severe performance degradation problem when placing particular VMs on the same PM. Furthermore, the Virtual Machine Placement (VMP) is one of the most challenging problems in cloud environments management and it’s been studied from various perspectives. In this paper, we are going to propose a VMP taxonomy in order to understand the various aspects that researchers consider while de?ning their VMP approaches. We will also survey the most relevant interference-aware virtual machine placement literature and then we shall give a comparative study between them.
关键词： Server Consolidation,Energy Efficiency,Interference-aware,Cloud Computing,Virtual Machine Placement
更新于2025-09-09 09:28:46