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There is a coupling relationship between the development of urban transportation and cities: Urban growth leads to increase in the demand for urban transportation and consequently, a lot of transportation emissions. Therefore, an in-depth understanding of the mechanism behind the driving effect of urban development on transportation emissions is a crucial prerequisite for coordinated development of low-carbon urban transportation and cities. Based on the oil product allocation method, this paper estimates the transportation emission in Beijing from 1995 to 2016. Then based on the understanding of the driving mechanism, this paper applies the urban allometric scaling law to analyze the relationship between city size and transportation emission. Finally, the driving mechanism is analyzed using the STRIPAT model. The results reveal a superlinear relationship between transportation emission in Beijing and the expansion of the city, as the former outgrew the latter. Population size, urbanization, economic size, industrial structure, spatial scale and infrastructure construction are positive driving factors of transportation emission, whereas progress of energy technologies as a negative driving factor can restrain the growth of transportation emission. Urbanization has the most significant impact on urban transportation emission, and economic size contributes the most to the growth of transportation emission. Based on the results, we make a few policy recommendations for low-carbon urban transportation of Beijing, which include: improving transportation efficiency in the process of urbanization; promoting energy conservation and emission reduction while pursuing economic development so as to decouple transportation emission from urban development; restricting unordered urban expansion and updating the concept of transportation infrastructure supply; and developing energy technologies to improve energy efficiency. [ABSTRACT FROM AUTHOR]

• CO 2 air conditioning systems driven by compressed air engines are designed innovatively. • CO 2 air conditioning system driven by compressed air engine can significantly reduce running costs. • Combination of air conditioning system and compressed air storage is promising. Traditional building air conditioning uses electricity or thermal energy to drive the refrigeration cycle. The energy released by the expansion of compressed air can also be used for driving the refrigeration cycle. Moreover, the expanded low-temperature air can be used in the air conditioning system too. In this paper, three forms of CO 2 air conditioning systems driven by novel reciprocating piston compressed air engines were designed, namely EAGC (Exhaust Air for Gas Cooler), EAS (Exhaust Air for Sub-cooler), and EASC (Exhaust Air for Space Cooling), to analyze the performance and economics of CO 2 air conditioning systems combined with compressed air energy storage technology. Twenty-seven typical cities were selected in different climate regions in China to evaluate the systems' performance and running cost under outdoor temperature changes and different electricity prices. The results show that compared with the electricity-driven CO 2 air conditioning system, the three systems can greatly improve the system COP (Coefficient of Performance) but still cannot reach the performance level of the conventional freon refrigeration systems. However, in cities like Beijing and Shanghai with the large peak-to-valley electricity price difference, EASC system compared to the electricity-driven R410A air conditioning system running costs are lower, the average running cost per hour can be saved 11.96% and 16.35%, respectively. This means that the CO 2 air conditioning system with compressed air energy storage technology has a certain economic application value and can be popularized on reasonable occasions. This innovative system design can help solve the contradiction between supply and demand of building energy, realize leisure energy consumption, and reduce the economic cost of energy consumption on the demand side. [ABSTRACT FROM AUTHOR]

Multi-energy systems can provide a constant level of service to end-use energy demands, while deriving delivered energy from a variety of primary/secondary energy sources. This fuel-switching capability can be used to reduce operating expenses, reduce environmental impacts, improve flexibility to accommodate renewable energy, and improve reliability. This paper presents four frameworks for incentivizing energy hub equipment investments for low-carbon operation targets. These frameworks vary in the measures taken to achieve low-carbon operation (explicit constraint versus carbon pricing) and in the relationship between the hub builder and operator (cooperative versus uncoordinated). The underlying energy hub model upon which these frameworks are built is an enhanced greenfield model, introducing “energy buses” to reduce dimensionality. A case study is conducted for a campus being designed in Beijing, and results from each framework are compared to illustrate their relative costs. When the operator cannot be trusted to cooperate in controlling emissions, the system must be “overbuilt” with more expensive equipment to ensure emissions target are met. A taxation-based approach increases overall costs at moderate emissions targets, but this effect decreases at aggressive targets. This paper also compares the cost of less efficient institutional frameworks with the most efficient approach, i.e., cooperation between builder and operator with constraints on emissions. [ABSTRACT FROM AUTHOR]

In recent years, Beijing has been facing serious environmental problems. As an important cause of environmental problems, a further study of the factors influencing CO2 emissions in Beijing has important significance for the social and economic development of Beijing. In this paper, Cointegration and Granger causality test were proposed to select influencing factors of CO2 emissions prediction in Beijing, the influencing factors with different leading lengths were checked as well, and the genetic algorithm (GA) was used to optimize the initial weight and threshold values of a support vector machine (SVM) and the new SVM optimized by GA (GA-SVM) was established to predict the CO2 emissions of Beijing from 2016-2020 with scenario analysis. Through the comparison of 36 kinds of development scenarios, we found that economic growth, resident population growth and energy intensity enhancement were the major growth factors of carbon emissions, of which the contributions exceed 0.5% in all kinds of development scenarios. Finally, this paper put forward some reasonable policy recommendations for the control of CO2 emissions. [ABSTRACT FROM AUTHOR]

Research has shown, that the replacement of conventional vehicles (CVs) by electric vehicles (EVs) can reduce urban heat island intensity (UHII). This leads not only to a more comfortable climate during summer but also to a reduction of carbon dioxide emissions from the vehicles themselves and to a reduction in the need for air conditioning (AC) and associated emissions. The current study examines to what extent a range of different mobility concepts, can lead to a reduction in urban heat island intensity and carbon dioxide emissions in the city of Beijing, China. For this purpose, the impact that electric vehicles fuelled with the average energy mix, hydrogen vehicles (HyVs) fuelled with hydrogen from electrolysis from the regular energy mix, HyVs fuelled with hydrogen produced through wind power, energy efficient CVs, EVs fuelled with wind power and energy efficient metro light railway (metro) travel have on summer heat island intensity (SHII) and CO 2 -emissions is analysed. The lowest SHII mitigation effect was found for a replacement of CVs with fuel efficient diesel cars while hydrogen cars that are fuelled with hydrogen generated from the average electricity mix even leads to higher SHII and higher CO 2 emissions. The largest SHII mitigation effect was found for a scenario where conventional vehicles are replaced with energy efficient metro travel. The CO 2 saving potential is highest for EVs which are powered with electricity generated from wind turbines, closely followed by HyVs that are fuelled with hydrogen generated from electrolysis of water using wind electricity. The paper helps policymakers and consumers to make the right choices when it comes to environmentally friendly mobility options. • Summer heat island intensity (SHII) is mitigated through different mobility choices. • CO 2 reduction by over 12,000 tons/day is possible through reduced usage of air conditioning. • Energy efficient public transportation leads to the highest mitigation of SHII and CO 2 levels. • Electric and hydrogen cars fuelled with renewable energies mitigate SHII and CO 2 levels. • Hydrogen cars fuelled with non-renewable energies lead to higher SHII and CO 2 levels. [ABSTRACT FROM AUTHOR]

Highlights • The increases of commuting CO 2 emissions are several times larger than the urban size, population, and economics' developments. • Metro services reducing commuting CO 2 emissions near the metro stations is not statistically significant, possibly because the proportions of car users near the metro stations are similar to the two cities' average levels, which is caused by their higher household income and the longer travel time using the metro. • In Beijing, there are the smallest commuting CO 2 emissions in the outer suburbs due to job-housing balances, short distance and large percentage of non-motorized mode uses while the largest commuting CO 2 emissions in the inner sprawl suburbs due to car trips with long distance. Abstract To understand the changing relationships between commuting CO 2 emissions (CCE), travel behavior and urban forms, this paper provides a comparative study between the typical Chinese cities of Beijing (more developed) and Xi'an (rapidly developing). Further, the effects of metro services on reducing CCE were explored, and comparative analysis on CCE between the inner sprawling suburbs and outer suburbs was conducted. It was found that: (i) the increases in CCE are several times larger than the increases in urban size, population, and economic developments; (ii) metro services reducing CCE near metro stations is not statistically significant, maybe because the proportions of car users near the metro stations are similar to the two cities' average levels, which is caused by their higher household income and the longer travel time using the metro; (iii) in Beijing, there are smallest CCE in the outer suburbs due to job-housing balances, short distance and large percentage of non-motorized mode uses while largest CCE in the inner sprawl suburbs due to car trips with long distance. These findings indicate that to cope with the rapidly increasing CCE, more attention should be paid to developing strong industry and real-estate simultaneously; the improvement in the feeder bus and public bicycle systems should also be reinforced to reduce the total travel time of metro users; and satellite cities with job-housing balance are greatly needed. The implications will benefit efforts to reduce CCE and mitigate global climate change, and they also provide empirical evidence and reference values for other global cities. [ABSTRACT FROM AUTHOR]

This paper developed internationally compatible methods for delineating boundaries of urban areas in China. By integrating emission source data with existing official statistics as well as using rescaling methodology of data mapping for 1 km grid, the authors constructed high resolution emission gridded data in Beijing-Tianjin-Hebei (Jing-Jin-Ji) region in China for 2012. Comparisons between urban and non-urban areas of carbon emissions from industry, agriculture, household and transport exhibited regional disparities as well as sectoral differences. Except for the Hebei province, per capita total direct carbon emissions from urban extents in Beijing and Tianjin were both lower than provincial averages, indicating the climate benefit of urbanization, comparable to results from developed countries. Urban extents in the Hebei province were mainly industrial centers while those in Beijing and Tianjin were more service oriented. Further decomposition analysis revealed population to be a common major driver for increased carbon emissions but climate implications of urban design, economic productivity of land use, and carbon intensity of GDP were both cluster- and sector-specific. This study disapproves the one-size-fits-all solution for carbon mitigation but calls for down-scaled analysis of carbon emissions and formulation of localized carbon reduction strategies in the Jing-Jin-Ji as well as other regions in China. [ABSTRACT FROM AUTHOR]

This paper calculates the energy consumption and CO emissions of Beijing over 2005-2011 in light of the Beijing's energy balance table and the carbon emission coefficients of IPCC. Furthermore, based on a series of energy conservation planning program issued in Beijing, the Long-range Energy Alternatives Planning System (LEAP)-BJ model is developed to study the energy consumption and CO emissions of Beijing's six end-use sectors and the energy conversion sector over 2012-2030 under the BAU scenario and POL scenario. Some results are found in this research: (1) During 2005-2011, the energy consumption kept increasing, while the total CO emissions fluctuated obviously in 2008 and 2011. The energy structure and the industrial structure have been optimized to a certain extent. (2) If the policies are completely implemented, the POL scenario is projected to save 21.36 and 35.37 % of the total energy consumption and CO emissions than the BAU scenario during 2012 and 2030. (3) The POL scenario presents a more optimized energy structure compared with the BAU scenario, with the decrease of coal consumption and the increase of natural gas consumption. (4) The commerce and service sector and the energy conversion sector will become the largest contributor to energy consumption and CO emissions, respectively. The transport sector and the industrial sector are the two most potential sectors in energy savings and carbon reduction. In terms of subscenarios, the energy conservation in transport (TEC) is the most effective one. (5) The macroparameters, such as the GDP growth rate and the industrial structure, have great influence on the urban energy consumption and carbon emissions. [ABSTRACT FROM AUTHOR]

• The net CO2 emissions of the Beijing-Shanghai high-speed rail are assessed. • The framework incorporates modal substitution and traffic generation effects. • Avoided infrastructure expansion and vehicle manufacturing are considered. • Large share of traffic diverted from ordinary-speed trains may raise emissions. This paper provides an ex-post assessment of net carbon dioxide (CO2) emissions of the Beijing-Shanghai high-speed rail (HSR) by including both mode substitution and traffic generation effects with a life-cycle approach. We are among the first authors to examine the emissions effects of a long-haul HSR and to consider the effects of avoided infrastructure expansion and vehicle manufacturing due to traffic diversion. We find that avoided infrastructure expansion plays a limited role in offsetting CO2 emissions from the construction of an HSR infrastructure, but the reduced demand for passenger vehicles can offset a larger share of emissions from the manufacturing of HSR rolling stock. Initially, too much traffic was diverted from ordinary-speed rail (OSR) to HSR, increasing emissions at the operation stage. As traffic diverted from road and air increased, the net emissions at the operation stage turned negative, offsetting emissions from infrastructure construction and vehicle manufacturing. [ABSTRACT FROM AUTHOR]