Design and Experimental Analysis of Charge Recovery for Piezoelectric Fan

The piezoelectric (PE) fan is widely adopted in the field of microelectronics cooling due to its advantages of high reliability and good heat dissipation characteristics. However, PE fans driven by conventional circuits suffer from plenty of energy loss. To save energy, we propose an inductor-based charge recovery method and apply it to the driving circuit for the PE fan. Two inductor-based driving circuits, a single inductor-based driving (SID) circuit and a double inductor-based driving (DID) circuit are compared. The SID circuit has a simple structure and a slightly higher energy-saving rate, while the DID circuit introduces no additional oscillations and is more stable. The experimental results show that when the supply voltage changes, both circuits have a relatively stable energy-saving rate, which is about 30% for the SID circuit and 28% for the DID circuit. Moreover, the proposed circuits enjoy the same driving capacity as the conventional circuit, and the driven fan has the same cooling performance.

An Internet of Things (IoT)-Based Master-Slave Regionalized Intelligent LED-Light-Controlling System

Reducing residential and industrial electricity consumption has been a goal of governments around the world. Lighting sources account for a large portion of the whole energy/power consumption. Unfortunately, most of the existing installed lighting systems are ancient and have poor energy efficiency. Today, many manufacturers have introduced light-controlling systems into the current market. However, existing light controlling systems may not be successfully applied to buildings, streets, and industrial buildings due to high costs and difficult installation and maintenance. To combat this issue, this article presents an easy-to-install, low-cost, Master-Slave intelligent LED light-controlling system based on Internet of Things (IoT) techniques. The benefit of using the proposed system is that the brightness of the LED lights in the same zone can be changed simultaneously to save in energy consumption. Furthermore, the parameters of the LED lights can be directly set. Moreover, the related data are collected and uploaded to a cloud platform. In this article, we use 15 W T8 LED tubes (non-induction lamps) as a case study. When the proposed system is installed in a zone with few people, the energy-saving rate is as high as 90%. Furthermore, when 12 people pass by a zone within one hour, its energy-saving rate can reach 81%. Therefore, the advantages of using the proposed system include: (1) the original lamp holder can be retained; (2) no wiring is required; and (3) no server is set up. Moreover, the goal of energy saving can also be achieved. As a result, the proposed system changes the full-dark mode of the available sensor lamp to the low power low-light mode for standby. Further, it makes the sensor lamps in the same zone brighten or low-light way simultaneously, which can quickly complete large-scale energy-saving and convenient control functions of intelligent LED lighting controlling system.

Idle Youth and Macroeconomics in Latin America

This paper analyzes the macroeconomic repercussions of the existence of idle youth in a cross-section of Latin American countries. The results indicate that idle youth has a close association with the indices of gender inequality and governance, and with informality. By estimating a series of equations, it was possible to infer that idle youth exerts adverse effects on economic growth, the domestic saving rate and economic vulnerability. It is also reported that the prevention of idle youth rests on substantial increases in tax revenues so as to increase social spending.

Analysis of Energy Performance and Integrated Optimization of Tubular Houses in Southern China Using Computational Simulation

Chinese rural construction is currently booming, but faces considerable challenges in terms of energy performance. The objective of this research was to analyze the energy performance of tubular houses, which are a unique type of rural house in southern China, with a particular architectural form and environmental adaptations. Previous field measurements showed that there was much room for improvement, with both winter and summer cases requiring particular attention. Numerical simulations of the annual energy consumption were conducted using Open-Studio. The results show that various levels of reduction in energy consumption (varying from 1.6% to 30.5%) were achieved by combining different renovations. Among them, using solar energy with a sunroom was found to be the most effective approach, with an energy-saving rate of 28%, followed by the approach of attaching insulation to the walls and roof, with an energy-saving rate ranging from 13.2% to 30.5%. The integrated optimization measures had an energy-saving rate of 47.4% with a total renovation cost of CNY 41,143.1, and the payback period of investment was within five years. If a tubular house with improved thermal insulation can be inherited as a component in the process of urbanization, it will aid in energy conservation and natural ecosystem protection for southern China.

Passive Energy-Saving Optimal Design for Rural Residences of Hanzhong Region in Northwest China Based on Performance Simulation and Optimization Algorithm

The rural residences of Northwest China are characterized by a state of high energy consumption and low comfort due to the limited economic level and awareness of energy-saving compared with the urban residences. To remedy this, appropriate passive design strategies should be adopted first, in order to provide a design mode with low energy consumption and low cost for rural residences under the premise of thermal comfort. In this paper, taking Hanzhong region (Shaanxi Province, China) as an example, we establish a benchmark model based on a field survey and develop an optimization process by combining EnergyPlus simulation software, the MOBO optimization engine, and weighted sum method. The action mechanisms of passive design parameters, including the building orientation, length–width ratio, building envelope parameters, external shading system, and window–wall ratio, on heating, cooling, and total energy consumption are analyzed, and the quantitative relationships between single-parameter and energy consumption are established. Then, the mutually restricted indices of total energy consumption and initial investment cost are taken as optimization objectives, and 17 design parameters are selected as the optimization variables. The NSGA-II algorithm is adopted to conduct the multi-parameter, multi-objective optimization design for rural houses in Hanzhong area, through coupling of the EnergyPlus and MOBO software. In this way, Pareto solutions are obtained and the value distributions of the multi-objectives and design parameters are analyzed. Based on the actual requirements of decision-makers and using the weight method, three design schemes focusing on different performance tendencies are proposed. The results indicate that by using the proposed optimization process, the building energy consumption can be significantly reduced while taking initial investment costs into account, where the energy-saving rate is in the range of 31.9%–61.5%. When the EC/IC ratio is 1:1, 2:1, and 1:2, the energy-saving rate can reach 51.5%, 57.8%, and 43.5%, respectively. It can provide a beneficial pattern for the energy-saving design and renovation of rural residences in Hanzhong area of China.

Transitional dynamics of the saving rate and economic growth

We estimate the relationship between GDP per capita growth and the growth rate of the national saving rate using a panel of 130 countries over the period 1960–2017. We find that GDP per capita growth increases (decreases) the growth rate of the national saving rate in poor countries (rich countries), and a higher credit-to-GDP ratio decreases the national saving rate as well as the income elasticity of the national saving rate. We develop a model with a credit constraint to explain the growth-saving relationship by the saving behavior of entrepreneurs at both the intensive and extensive margins. We further present supporting evidence for our theoretical findings by utilizing cross-country time series data of the number of new businesses registered and the corporate saving rate.

CAPITAL AND GROWTH

This paper develops and discusses a neoclassical growth model with two inputs: physical capital stock and combined stock of human and intellectual capital. The production process is subject to diminishing returns to capital in perfect markets, in sharp contrast to new endogenous growth models that assume increasing returns to capital in imperfect markets. The model finds that a high saving rate raises both transitional and steady state growth rates of output through increases in physical, human, and intellectual investments that augment labor productivity—a key extension of the Solow (1956)-Swan (1956) growth model. Additionally, the paper derives an optimal rule for choosing the saving rate that maximizes consumer welfare. Implications for growth policies are drawn.

Energy Efficiency Improvement Solutions for Supermarkets by Low-E Glass Door and Digital Semi-Hermetic Compressor

This research presents an energy efficiency improvement solution for supermarkets with the use of low-E glass doors for open refrigerators and a digital semi-hermetic compressor to fix the speed of semi-hermetic compressors. The impact of a door’s installation causes its load to be reduced by 40%, and the compressor shuts down frequently, which decreases its lifetime. In order to ensure that energy-saving solutions do not affect maintenance costs, the installation of a digital semi-hermetic compressor is proposed to lower costs and save energy. Our economic results from tests carried out at a 3000 square meter supermarket, which was open from 6:00 am to 12:00 am and in which we installed 82 doors on 15 open refrigerators, showed a 1.1-year payback period with an energy saving rate of 192,220 kWh/year for store No.1 (R22) and in which we installed 80 doors on 15 open refrigerators, showed a 1.4-year payback period with an energy saving rate of 171,185 kWh/year for store No.2 (R404A). The energy-saving effects of the digital semi-hermetic compressor, which fixes the speed of the semi-compressor and solves the problem of impact from fridge door installation, showed a 2.9-year payback period with an energy saving rate of 26,890 kWh/year for store No.1 (R22) and showed a 2.9-year payback period with an energy saving rate of 26,571 kWh/year for store No.2 (R404A). The results of store No.1 (R22) and store No.2 (R404A) showed no differences. This research is an extension of an energy-saving project that can be carried out on a continuous basis, increasing the efficiency of energy use and being a sustainable source of energy conservation.

Off-Design Dynamic Performance Analysis of a Solar Aided Coal-Fired Power Plant

Coal consumption and CO2 emissions are the major concerns of the 21st century. Solar aided (coal-fired) power generation (SAPG) is paid more and more attention globally, due to the lesser coal rate and initial cost than the original coal-fired power plant and CSP technology respectively. In this paper, the off-design dynamic performance simulation model of a solar aided coal-fired power plant is established. A 330 MW subcritical coal-fired power plant is taken as a case study. On a typical day, three various collector area solar fields are integrated into the coal-fired power plant. By introducing the solar heat, the variations of system performances are analyzed at design load, 75% load, and 50% load. Analyzed parameters with the change of DNI include the thermal oil mass flow rate, the mass flow rate of feed water heated by the solar energy, steam extraction mass flow rate, coal consumption, and the plant thermal efficiency. The research results show that, as DNI increases over a day, the coal saving rate will also increase, the maximum coal saving rate reaches up to 5%, and plant thermal efficiency reaches 40%. It is analyzed that the SAPG system gives the best performance at a lower load and a large aperture area.