Abstract

With the rapid development of railway traffic in China’s alpine regions, real-time self-powered snow removal is an important route for cleaning track switch, which currently still use manual sweeping or electrical heating. These two traditional snow removal methods require large amounts of manpower or electricity. Here we propose a zero-energy snow clearing device that can continuously remove snow for switch only by track vibration. This device mainly contains a motion conversion mechanism and an air compression component. The motion conversion mechanism can amplify the micro-vibration of the rail and act as a mechanical engine (ME) that drives the air compression component to generate high-pressure air to blow off the snow at the track switch. A prototype was manufactured to demonstrate the feasibility of the design. From the high-pressure air generated by rail vibration to the process of snow removal, it is a nature cycle of no external energy consumption.

Abstract

Thermoelectric generator (TEG) technology has considerable potential in the recovery and utilization of waste heat of automobile exhaust. This paper simulated the thermoelectric generator by using the automobile exhaust waste heat in numerical simulation method. The numerical calculation shows that the total open voltage of the thermoelectric modules increases with the wall thickness increases when the length of exhaust gas channel is same as the length of all one-side thermoelectric modules. When the length of the exhaust gas channel increases, the open circuit voltage of the thermoelectric modules on the channel first decreases and then increases along the air inlet direction, and the total open circuit voltage of the thermoelectric modules also increases with the increase of the wall thickness of the exhaust gas channel.

Abstract

Energy consumption model is the key for energy demand reduction in data center, but existing models are usually static, which cannot well represent the dynamic coupling characteristics of energy consumption in each component and fluid change. To address this issue, this paper constructs a dynamic energy consumption model (named the DECM) to simulate the energy consumption dynamic process in MATLAB/Simulink platform. The DECM mainly includes two energy-consumption components of data center, namely information technology (IT) equipment and cooling equipment. For the IT equipment, a polynomial based general modeling method is proposed by fitting real data from the SPECpower_ssj2008 benchmark, so as to improve the modeling accuracy in data center. For the cooling equipment, a dynamic model consisted of server fan, computer room air conditioning (CRAC), chilled water pump, refrigeration chiller and cooling tower is developed, and the cooling system is coupled with IT equipment. Finally, taking a data center with 100 racks and having 10 servers in each rack as an example, simulation results illustrate the effectiveness of the proposed DECM while ensuring the internal temperature of data center at an accept able value to some extent.

Abstract

Rapid economic development has led to the deterioration of atmospheric environmental quality in China, where outdoor PM2.5 exposure has become the fourth leading risk factor. Meanwhile, differences in
socioeconomic level and demographic characteristics have led to gaps in provinces coping with air pollution, which means different social vulnerability levels in different provinces. With reference to research
achievements of social vulnerability, this study made a new trial regarding social vulnerability assessment to air pollution, which contains exposure, susceptibility and adaptability three dimensions. Based on ChinaHighPM2.5 and LandScanTM dataset, socioeconomic and demographic data at provincial level, we used PM2.5 exposure risk assessment model and global exposure mortality model (GEMM) to analyze the spatiotemporal distribution of PM2.5 concentration and its health effect, then assess the social vulnerability to air pollution for China provinces based on principle component analysis (PCA) and disaster risk assessment method. Results show that the PM2.5 concentration increased during 2000~2013 and decreased significantly after 2013 because of air control policies. Correspondingly, the number of PM2.5-related premature mortality also showed a trend of increasing first and then decreasing during 2000~2019. In the context of air pollution, high social vulnerability level is mainly concentrated in the central region of China, such as Sichuan and Chongqing, and the level decreases from the central region to the periphery, the eastern coastal regions have a relatively weak social vulnerability, such as Guangdong and Shanghai. As a result, PM2.5 is still a great threat to human health in China and the spatial variation and inequality in social vulnerability provide policy-makers a scientific basis for air pollution prevention and sustainable
management.

Abstract

Road pavements have tremendous potential in solar energy harvesting since they occupy a great share of urban surface and can absorb abundant solar radiation. Pavement-integrated photovoltaic (PIPV) module, pavement-integrated solar thermal (PIST) module, and pavement-integrated photovoltaic thermal (PIPVT) module are typical solar energy harvesting pavement modules that have emerged in the past few years. In this study, the performance of these modules was assessed and compared through numerical simulations on the weather conditions of four typical days representing different seasons in Shanghai. The results show that the PIPVT module can generate slightly more electricity than the PIPV module, while output less heat compared with the PIST module on all typical days. The PIPVT module can achieve the average overall energy efficiency of 37.31% considering both electricity and heat yields. Additionally, all three solar energy harvesting pavement modules have positive impact on mitigating the urban heat island (UHI) effect, and the PIPVT and PIST module can mitigate the UHI effect most and least significantly, respectively.

Abstract

It is important to prevent the decomposition of perovskite by UV-radiation in air environment for commercialization. The structure of a mesoscopic perovskite solar cell has great potential for the solar cell industry. It is vulnerable to UV-radiation due to reversible performance deterioration that has been observed in this structure. In this study, perovskite solar cells (PSCs) were prepared using an Al-doped TiO2 buffer layer as electron transport layer combined with a mesoporous-TiO2 layer in order to prevent this problem. The Al concentration of 7 mol% in Al-TiOx buffer layer was shown to enhance the performance of the perovskite solar cell, as these solar cells exhibited a power conversion efficiency of up to 11.87%.

Abstract

This study analyzes the impact of urban compactness on carbon emissions. The essay proposes three broad dimensions to evaluate compactness: urban form, spatial structure and infrastructure efficiency. The impact of compactness on carbon emissions is then analyzed by a panel model using data from 2002 to 2018 on 49 high-tier Chinese cities. The results suggest that of all compact variables, only mixed land use tends to be associated with less carbon emissions. In addition, higher ranking cities emit more carbon than lower ranking cities.

Abstract

As energy issues become serious, the utilization of distributed energy resources in microgrid has become the most popular choice. At the same time, electric vehicles are growing fast and have been recognized as the most promising direction. However, the uncertainty of power generation and EVs charge/discharge will cause power grid fluctuation, which in further increases the control load. Under this circumstance, battery energy storage system is considered as the most effective way to overcome the instability and alleviate energy crisis. This paper evaluates the battery energy storage system optimal configuration in a residential area involving electric vehicles based on cost analysis includes the basic structure of MG and the model of electric vehicles. The BESS investment cost, environmental value and EVs subsidy are taken into account in cost analysis part. The Battery Performance and Cost model is used for the bottom-up design and calculation for unit capacity costs with different levels of rated capacity. The results in the case study show the system rated capacity and power decrease greatly when electric vehicles participate in frequency control with economical energy management strategy. And the using of Battery Performance and Cost could make the result more accurate, which benefits from unit cost changing value. Finally, the most optimal configuration is given by balancing the effect of the microgrid frequency control and the total daily cost.

Abstract

In this study, two-dimensional CFD simulation model is developed for investigating the hydrogen separation process across the Pd-membrane type. The influences of H2 feeding flow rate and membrane thickness on the hydrogen permeation process were investigated. Also, two Pd-membrane thicknesses of 15μm and 20μm were investigated to understand the hydrogen embrittlement and diffusion through membrane. The numerical model parameters was adjusted at a reactor temperature of 150 :C and feed pressure of 100 kPa. The velocity, concentration, and diffusion mass transfer flux distribution were numerically achieved by the model. The simulation results showed that the hydrogen velocity distribution increased with the feeding gas flow rate. Furthermore, the diffusion flux was enhanced with the permeation time and the feeding flow rate increased. It can be concluded that the hydrogen concentration and diffusion mass transfer flux through thick membranes was low compared with lower membrane thickness. It can be expected that the CFD simulation model will aid in the membrane separation design, selection and development.