Junling Huang and Michael B. McElroy. 2015. “
A 32-year perspective on the origin of wind energy in a warming climate.” Renewable Energy, 77, May, Pp. 482-492.
Publisher's VersionAbstractBased on assimilated meteorological data for the period January 1979 to December 2010, the origin of wind energy is investigated from both mechanical and thermodynamic perspectives, with special focus on the spatial distribution of sources, historical long term variations and the efficiency for kinetic energy production. The dry air component of the atmosphere acts as a thermal engine, absorbing heat at higher temperatures, approximately 256 K, releasing heat at lower temperatures, approximately 252 K. The process is responsible for production of wind kinetic energy at a rate of 2.46 W/m2 sustaining thus the circulation of the atmosphere against frictional dissipation. The results indicate an upward trend in kinetic energy production over the past 32 years, indicating that wind energy resources may be varying in the current warming climate. This analysis provides an analytical framework that can be adopted for future studies addressing the ultimate wind energy potential and the possible perturbations to the atmospheric circulation that could arise as a result of significant exploitation of wind energy.
Yanxia Zhang, Haikun Wang, Sai Liang, Ming Xu, Qiang Zhang, Hongyan Zhao, and Jun Bi. 2015. “
A dual strategy for controlling energy consumption and air pollution in China's metropolis of Beijing.” Energy, 81, 1 March, Pp. 294-303.
Publisher's VersionAbstract
It is critical to alleviate problems of energy and air pollutant emissions in a metropolis because these areas serve as economic engines and have large and dense populations. Drivers of fossil fuel use and air pollutants emissions were analyzed in the metropolis of Beijing during 1997-2010. The analyses were conducted from both a bottom-up and a top-down perspective based on the sectoral inventories and structural decomposition analysis (SDA). From a bottom-up perspective, the key energy-intensive industrial sectors directly caused the variations in Beijing's air pollution by means of a series of energy and economic policies. From a top-down perspective, variations in production structures caused increases in most materials during 2000-2010, but there were decreases in PM10 and PM2.5 emissions during 2005-2010. Population growth was found to be the largest driver of energy consumption and air pollutant emissions during 1997-2010. This finding suggests that avoiding rapid population growth in Beijing could simultaneously control energy consumption and air pollutant emissions. Mitigation policies should consider not only the key industrial sectors but also socioeconomic drivers to co-reduce energy consumption and air pollution in China's metropolis.
Hongfei Cui, Pan Mao, Yu Zhao, Chris P Nielsen, and Jie Zhang. 2015. “
Patterns in atmospheric carbonaceous aerosols in China: Emission estimates and observed concentrations.” Atmospheric Chemistry and Physics, 15, Pp. 8657–8678.
Publisher's VersionAbstract
China is experiencing severe carbonaceous aerosol pollution driven mainly by large emissions from intensive use of solid fuels. To gain a better understanding of the levels and trends of carbonaceous aerosol emissions and the resulting ambient concentrations at the national scale, we update an emission inventory of anthropogenic organic carbon (OC) and elemental carbon (EC), and employ existing observational studies to analyze characteristics of these aerosols including temporal, spatial, and size distributions, and the levels and contributions of secondary organic carbon (SOC) to total OC. We further use ground observations to test the levels and inter-annual trends of the calculated national and provincial emissions of carbonaceous aerosols, and propose possible improvements in emission estimation for the future. The national OC emissions are estimated to have increased 29% from 2000 (2127 Gg) to 2012 (2749 Gg) and EC by 37% (from 1356 to 1857 Gg). The residential, industrial, and transportation sectors contributed an estimated 76±2%, 19±2% and 5±1% of the total emissions of OC, respectively, and 52±3%, 32±2% and 16±2% of EC. Updated emission factors based on the most recent local field measurements, particularly for biofuel stoves, lead to considerably lower emissions of OC compared to previous inventories. Compiling observational data across the country, higher concentrations of OC and EC are found in northern and inland cities, while larger OC/EC and SOC/OC ratios are found in southern cities, due to the joint effects of primary emissions and meteorology. Higher SOC/OC ratios are estimated at rural and background sites compared to urban ones, attributed to more emissions of OC from biofuel use, more biogenic emissions of volatile organic compound (VOC) precursors to SOC, and/or transport of aged aerosols. For most sites, higher concentrations of OC, EC, and SOC are observed in colder seasons, while SOC/OC is reduced, particularly at regional sites, attributed partly to weaker atmospheric oxidation and SOC formation compared to summer. Enhanced SOC formation from oxidization and anthropogenic activities like biomass combustion is judged to have crucial effects on severe haze events characterized by high particle concentrations. Several observational studies indicate an increasing trend in ambient OC/EC (but not in OC or EC individually) from 2000 to 2010, confirming increased atmospheric oxidation of OC across the country. Combining the results of emission estimation and observations, the improvement over prior emission inventories is indicated by inter-annual comparisons and correlation analysis. It is also indicated, however, that the estimated growth in emissions might be faster than observed growth, and that some sources with high primary OC/EC like burning of biomass are still underestimated. Further studies to determine changing emission factors over time in the residential sector and to compare to other measurements such as satellite observations are thus suggested to improve understanding of the levels and trends of primary carbonaceous aerosol emissions in China.
X.F. Wu, G.Q. Chen, X.D. Wu, Q. Yang, A. Alsaedi, T. Hayat, and B. Ahmad. 2015. “
Renewability and sustainability of biogas system: Cosmic exergy based assessment for a case in China.” Renewable and Sustainable Energy Reviews, 51, Pp. 1509-1524.
Publisher's VersionAbstract
The household-scale biogas system gains its popularity in rural China, and is now playing a prominent role in relieving energy shortages and reducing environmental pollution. A comprehensive review is performed for related environmental and ecological assessment studies. For an overall assessment of the biogas system, especially for its renewability and sustainability, an updated exergy methodology in terms of cosmic exergy is introduced in this paper, and is concretely illustrated by a case study to an integrated biogas engineering in Hubei, China. Associated with the fundamental universal scale of the cosmic-solar-terrestrial ecosystem, this new approach aggregates natural resources, economic inputs and environmental contamination on a common basis. Furthermore, a series of cosmic exergy based indicators are established to quantify the renewability and sustainability of the system. The integrated biogas engineering is proved to be with remarkable positive net ecological benefits, around twice that of the corresponding conventional production system. Near half of resource inputs in the integrated biogas system are found to be renewable. The renewability and sustainability of the biogas system turn out to be respectively double and six times those of the conventional system. The findings are fully supportive for policy makers in their action towards further progress of biogas project for sustainable development.
Haikun Wang, Yanxia Zhang, Xi Lu, Chris P Nielsen, and Jun Bi. 2015. “
Understanding China's carbon dioxide emissions from both production and consumption perspectives.” Renewable and Sustainable Energy Reviews, 52, Pp. 189-200.
Publisher's VersionAbstract
China is now the largest emitter of CO2 in the world, having contributed nearly half of the global increase in carbon emissions between 1980 and 2010. The existing literature on China’s carbon emissions has focused on two dimensions: the amount of CO2 emitted within China’s geographical boundaries (a production-based perspective), and the drivers of, and responsibility for, these emissions (a consumption-based perspective). The current study begins with a comprehensive review of China’s CO2 emissions, and then analyzes their driving forces from both consumption and production perspectives, at both national and provincial levels. It is concluded that China’s aggregate national CO2 emissions from fossil fuel consumption and cement production maintained high growth rates during 2000-2010. National emissions reached 6.8–7.3 billion tons in 2007, nearly 25% of which were caused by net exports (i.e., exports minus imports) to other countries. However, emission characteristics varied significantly among different regions and provinces, and considerable emission leakage from the developed eastern regions to inland and western areas of the country was found. The objectives of China’s policies should therefore be broadened from continued improvement of energy efficiency to accelerating regional technology transfer and preventing mere relocation of carbon-intensive economic activities from developed coastal regions to less developed, inland provinces. To rapidly and effectively cut down China’s carbon emissions, moreover, its energy supply should be aggressively decarbonized by promoting renewable and low carbon energy sources.