Xunmin Ou

Analysis on energy–water nexus by Sankey diagram: the case of Beijing

Abstract We visualize water utilization in Beijing from source to service and onwards to destination using Sankey diagram to analyze the energy–water nexus at the city level. First, we describe the methodology, definition, and data and apply the Sankey diagram approach. Beijing faces highly constrained water resources and relies heavily on water that is energy-intensive to supply (such as underground water or water that must be conveyed over long distances. We find that the electricity required for water supply, treatment, utilization, and post-use utilization comprised about 5–7% of total electricity consumption in Beijing in 2009. We further find that water used in the energy-related sub-sectors accounted for about one-fourth of the water used in the whole industrial sector and about of 3% of the total fresh water used in Beijing in 2009. Among the energy related sub-sectors, the electricity sub-sector was found to be the largest contributor.

The Status Quo and Development Trend of Low-carbon Vehicle Technologies in China

Three types of low-carbon vehicle technologies in China are reviewed. Potential effects are listed for those integrated energy-saving technologies for conventional vehicles. Low carbon transitions, including alternative vehicle power train systems and fuels, are discussed on their development status and trends, including life cycle primary fossil energy use and greenhouse gas emissions of each pathway. To further support the low-carbon vehicle technologies development, integrated policies should seek to: (1) employ those integrated energy-saving technologies, (2) apply hybrid electric technology, (3) commercialize electric vehicles through battery technology innovation, (4) support fuel cell vehicles and hydrogen technology R&D for future potential applications, (5) boost the R&D of second generation biofuel technology, and (6) conduct further research on applying low-carbon technologies including CO2 capture and storage technology to coal-based transportation solutions.

Petroleum substitution, greenhouse gas emissions reduction and environmental benefits from the development of natural gas vehicles in China

This study develops a bottom-up model to quantitatively assess the comprehensive effects of replacing traditional petroleum-powered vehicles with natural gas vehicles (NGVs) in China based on an investigation of the direct energy consumption and critical air pollutant (CAP) emission intensity, life-cycle energy use and greenhouse gas (GHG) emission intensity of NGV fleets. The results indicate that, on average, there are no net energy savings from replacing a traditional fuel vehicle with an NGV. Interestingly, an NGV results in significant reductions in direct CAP and life-cycle GHG emissions compared to those of a traditional fuel vehicle, ranging from 61% to 76% and 12% to 29%, respectively. Due to the increasing use of natural gas as a vehicle fuel in China (i.e. approximately 28.2 billion cubic metres of natural gas in 2015), the total petroleum substituted with natural gas was approximately 23.8 million tonnes (Mt), which generated a GHG emission reduction of 16.9 Mt of CO2 equivalent and a CAP emission reduction of 1.8 Mt in 2015. Given the significant contribution of NGVs, growing the NGV population in 2020 will further increase the petroleum substitution benefits and CAP and GHG emission reduction benefits by approximately 42.5 Mt of petroleum-based fuel, 3.1 Mt of CAPs and 28.0 Mt of GHGs. By 2030, these benefits will reach 81.5 Mt of traditional petroleum fuel, 5.6 Mt of CAPs and 50.5 Mt of GHGs, respectively.

Life Cycle Analysis on Energy Consumption and GHG Emissions of Secondary Energy in China in 2008

This paper presents life cycle fossil primary energy consumption (FPEC) and greenhouse gas (GHG) emission intensity of nine types of dominant secondary energy (SE) in China in 2008. Three major types of GHG (CO2, CH4 andN2O) are considered for GHG emissions intensity and then on-combustion CH4 leakage during the feedstock production sub-stage is included. It is found that: (1) the life cycle FPEC intensities of crude coal, crude NG, crude oil, coal, NG, diesel, gasoline, residual oil and electricity are 1.055, 1.155, 1.167, 1.172, 1.161, 1.302, 1.343, 1.220 and 2.924 MJ per MJ SE obtained and utilized, respectively, (2) their life cycle GHG emissions intensities are 100.5, 68.6, 89.2, 104.5, 72.7, 102.4, 98.9, 102.9 and 289.6 when the direct GHG emissions are included. The life cycle intensities of both FPEC and GHG emissions for SE in China are higher than those in the developed world (even the world average) and the main reasons include the relatively low energy efficiencies and the high CH4 leakage levels during feedstock extraction.