Results 1 - 10 of 109901
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[en] We demonstrated a method for measuring the quantum efficiency of deep UV emission using the two-step excitation and the difference of the integrated spectral intensities in Pr3+-doped CaAl4O7 and SrAl4O7 crystals. The quantum efficiencies of the emission from the lowest 4f5d state in the two systems have been estimated to be less than 10% at room temperature. The effect of excited-state absorption of the lowest 4f5d state is analyzed for the quantum efficiency measurement. The actual efficiency may be higher when this effect is taken into account, especially under the condition of strong excitation
[en] Energy Efficiency is an important aspect in building management, in particular, to reduce the waste of energy and at the same time can reduce the Carbon Dioxide (CO2) emission into the atmosphere. An energy audit is a mechanism which is capable of measuring energy efficiency performance and to identify potential energy savings for a building. The purpose of this research study is to identify energy efficiency in Building Management & Education training (BPPL), Malaysian Nuclear Agency (Nuclear Malaysia), Bangi. To achieve the purpose of this study, two objectives had been identified which are; to measure Building Energy Index (BEI) and to provide recommendations of energy saving from aspects cost and rates of carbon dioxide emissions into the atmosphere. Data collected through Preliminary Energy Audit and Targeted Energy Audit and were assisted with mathematical model analysis. Result for this study shows that the results of BEI is 79 kWh/ m2/year. To maximize the energy efficiency and reduce the electricity bills, several strategies and techniques for reducing energy waste are recommended for improvement which are; no-cost initiatives (for example Awareness campaign, the arrangement of operating hours) and with cost initiatives (for example installation of energy efficient equipment). The implementation of this strategy is expected to reduce about RM93, 851.85 of electricity cost and 2.0 % of a total of Nuclear Malaysia electricity bill. If the strategy is fully implemented, the amount of BEI and CO2 emission also can be reduced up to 38.5 kWh/ m2/ year and 192,074.87 kg CO2. The implementation of strategy also provides a payback period in a short time with the expected of between 0.1 to 1.9 years. In fact, through this strategy, Nuclear Malaysia has the potential to increase the life of equipment and reduce maintenance costs. (author)
[en] Highlights: • Investigated the operation status of the industrial boilers in Hunan Province. • Obtaining an importance ranking of the corresponding key factors. • Supposed industrial boiler energy efficiency standards for Hunan Province. Specially tailored energy efficiency standards are critical for the energy-saving of local industrial systems. We take the Hunan province as a concrete example, and select its industrial boiler as the study subject based on the survey results of Hunan’s leading industrial structure. Effective energy and exergy quantitative analysis methods were applied to obtain the efficiency of the target industrial boilers. Combining the corresponding reference standards with the exergy & thermal efficiency, the analytic hierarchy process, and uncertainty analysis results, we propose a reasonable regional industrial boiler energy efficiency standard. Additionally, the main factors affecting the industrial boiler system were distilled and ranked: 1-exhaust gas temperature, 2-fuel volatile matter, 3-air coefficient, 4-boiler capacity, 5-cold air temperature, 6-slag carbon content, 7-slag temperature. These results could provide a theoretical foundation for designing further energy-saving renovation projects of the industrial boiler system.
[en] This research examines some of the multiple benefits of a home energy efficiency upgrade programme for social housing tenants. Employing a quasi-experimental approach, we examine a range of objectively measured and self-reported outcomes, including metered gas consumption, for a control and upgrade group, before and after the upgrade. We drew our sample from a large home energy efficiency programme in Ireland, The SEAI Better Energy Communities Scheme, which provides funding for whole communities to upgrade the efficiency of their dwellings. Dwellings were selected for upgrade based on need, allowing us to control for observable dwelling characteristics correlated with selection into the trial. The upgrades undertaken were extensive relative to the average home energy improvement, with many dwellings receiving a number of measures. Households reported improvements across a range of outcomes associated with heating-related deprivation and comfort in the home. We use panel regression models to estimate the elasticity of gas demand with respect to the thermal efficiency of the dwellings. Overall, we find that use of natural gas fell much less than 1:1 for each increment to thermal efficiency of the home. For the average household in this study, about one third of the marginal increase in thermal efficiency was reflected in reduced gas demand. This result highlights issues with standard engineering models which are commonly used to assess the energy efficiency of dwellings and points to a behavioural response from households, potentially taking back some of the savings as increased internal temperatures.
[en] While perovskite nanocrystals (NCs) have shown great potential as materials for efficient light emitting diodes, low photoluminescence quantum yield (PLQY)and stability of the blue, and green emitting perovsldtes NCs is impedimentto development of light emitting diodes with high luminous efficiency and long durability. Herein, we report a halide-rich synthesis of blue and green emitting CsPbX3(X=CI, Br) NCs, which leads to near-unity PLQY with remarkable photo stability. (author)
[en] The heat pump system with economizer coupled with scroll compressor can operate steadily under the conditions of large temperature differences with high capacity and efficiency, and it has a great potential for application in cold regions. Based on the second law of thermodynamics, the heat pump system with economizer coupled with scroll compressor is exergetically analyzed, and the expressions related to exergy, exergy loss and exergy efficiency are derived. Experimental data for such a heat pump prototype have been obtained and used for the exergy analysis. It is found that compressor is a main bottleneck to improve the energy efficiency of heat pump followed by evaporator and condenser, and the improvement of refrigerating accessories such as filter-dryer and expansion valve is also effective to increase the efficiency of the heat pump. (author)
[en] The acceleration efficiency of a laser driven linear accelerator is analyzed. The laser power, loss factor and impedances determine the maximum charge that can be accelerated and the efficiency of that acceleration. The accelerator structure can be incorporated into a laser cavity. The equation for the resultant laser pulse is derived and analyzed. A specific example is presented, and the steady-state laser pulse shapes, acceleration efficiency, and average unloaded gradient are calculated
[en] The transition to a cleaner and more cost-efficient electricity system in China is political-economic as well as technological. An example is the reform of China's method of dispatching power plants, which potentially affects the economic relationships between consumers and producers, between grid and generating companies, and between central and provincial governments. Historically, coal-fired power plants in China all received roughly the same number of operating hours, regardless of efficiency or cost. In 2007, Chinese government agencies began to pilot “energy efficient dispatch,” which requires that generators be dispatched on the basis of thermal efficiency. Using a case study of Guangxi Zhuang Autonomous Region in southern China, we evaluated potential energy and cost savings from a change to energy efficient dispatch. We found that the savings are at best relatively small, because large, efficient generators already account for a significant share of total generation. Moreover, as an administrative policy that does not change economic incentives, energy efficient dispatch exacerbates imbalances and center-provincial tensions in the current system. We argue that incentive-based dispatch reform is likely to produce better outcomes, and that the keys to this reform are empowering an independent regulator with pricing authority and establishing a formal, transparent ratemaking process. - Highlights: ► Savings from China's energy efficient dispatch (EED) policy are at best relatively small. ► EED exacerbates imbalances and center-provincial tensions in China's current power system. ► Incentive-based dispatch reform is likely to produce better outcomes than EED. ► Keys to reform are independent regulation and a formal, transparent ratemaking process. ► Transition to cleaner, cost-efficient electricity system in China is political-economic as well as technological.
[en] The cement industry is one of the world’s largest energy consumers. In this work, a walk-through study of representative cement companies was carried out to characterize the energy profile of the cement industry in Colombia, with emphasis on evaluating the degree of obsolescence of the technology used in the processes, as well as identifying the main barriers that prevent the adaptation of more efficient technologies. Perception-surveys were performed among the energy managers to determine the barriers that hinder the implementation of energy efficiency measures. A factor that quantifies the influence of each type of barrier was defined according to the results of the survey. The results show that the Colombian cement industry has a specific energy consumption that is competitive with the largest cement producers in the world, while the technological obsolescence found is at a medium - low level. Furthermore, the main barrier to the penetration of energy efficiency technologies and measures is identified as the hidden costs associated with the implementation of these technologies. Finally, some conventional and emerging technologies are proposed to improve the efficiency of thermal energy use in the processes studied. - Highlights: • Colombian cement industry has competitive specific energy consumption. • Technological obsolescence was found to be at a medium - low level. • The main barrier to the penetration of efficient technologies is the hidden costs.
[en] Without reinforced energy saving policies, residential consumption of electricity will increase sharply over the next 20 years, in particular, as a result of expected growth in the specific uses of electricity. The main problem is not a lack of energy-efficient technologies, which do indeed exist for electrical appliances, but one of slow diffusion of existing technologies due to the weakness of the price signal and the purchasing behaviour of consumers. In association with energy labelling, minimum energy performance standards have proved to be very effective in stimulating technological progress and organising market transformation. But standards also suffer from long and often difficult implementation periods because of the resistance of the industrial sector. For manufacturers, similar results could be obtained more easily and more rapidly with voluntary agreements because they introduce flexibility margins in the achievement of commitments. This paper analyses the specific advantages of voluntary agreements for improving energy efficiency in the domestic appliances sector. We conclude that voluntary agreements may be an effective instrument for market transformation in certain conditions, but the alternative of regulatory measures must remain a credible, realistic threat if voluntary agreements are to have a really significant impact on performance improvement