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The COVID-19 pandemic is impacting human activities, and in turn energy use and carbon dioxide (CO 2 ) emissions. Here we present daily estimates of country-level CO 2 emissions for different sectors based on near-real-time activity data. The key result is an abrupt 8.8% decrease in global CO 2 emissions (-1551 Mt CO 2 ) in the first half of 2020 compared to the same period in 2019. The magnitude of this decrease is larger than during previous economic downturns or World War II. The timing of emissions decreases corresponds to lockdown measures in each country. By July 1st, the pandemic's effects on global emissions diminished as lockdown restrictions relaxed and some economic activities restarted, especially in China and several European countries, but substantial differences persist between countries, with continuing emission declines in the U.S. where coronavirus cases are still increasing substantially.

As the human population increases and production expands, energy demand and anthropogenic carbon emission rates have been growing rapidly, and the need to decrease carbon emission levels has drawn increasing attention. The link between energy production and consumption has required the large-scale transport of energy within energy transmission networks. Within this energy flow, there is a virtual circulation of carbon emissions. To understand this circulation and account for the relationship between energy consumption and carbon emissions, this paper introduces the concept of "carbon emission flow in networks" and establishes a method to calculate carbon emission flow in networks. Using an actual analysis of China's energy pattern, the authors discuss the significance of this new concept, not only as a feasible approach but also as an innovative theoretical perspective.

The COVID-19 pandemic is impacting human activities, and in turn energy use and carbon dioxide (CO2) emissions. Here we present daily estimates of country-level CO2 emissions for different sectors based on near-real-time activity data. The key result is an abrupt 8.8% decrease in global CO2 emissions (-1551 Mt CO2) in the first half of 2020 compared to the same period in 2019. The magnitude of this decrease is larger than during previous economic downturns or World War II. The timing of emissions decreases corresponds to lockdown measures in each country. By July 1st, the pandemic's effects on global emissions diminished as lockdown restrictions relaxed and some economic activities restarted, especially in China and several European countries, but substantial differences persist between countries, with continuing emission declines in the U.S. where coronavirus cases are still increasing substantially.

Highlights • A modified multi-period Nash-Cournot model is established. • The large-scale of renewables and flexible resources are considered in the model. • The renewables curtailment situations are considered in the model. • An empirical example is provided, based on the real data of BTT region, China. • Suggestions for future electricity and environment policies are presented. Abstract Facing stricter energy policies, the power mix in China is experiencing significant changes. First, the proportion of renewables, which have intermittent and stochastic generation, is assumed to be rapidly increasing. Thus, there is an increasing requirement to install more flexible generation capacity in the power system. According to the Chinese government’s energy planning, in the near future, the proportion of gas-fired units will be greatly promoted to add flexibility to the power system. The impacts incurred by developing a high proportion of both renewables and gas-fired generation on the power market should be formulated and analyzed. In this study, a modified Nash-Cournot equilibrium model is proposed, considering renewable curtailment situations during valley times. Then, a large-scale and multi-period unit commitment model that considers the combined heat and power characteristics is presented to simulate market behaviors. On this basis, an empirical analysis of the Beijing-Tianjin-Tangshan power system equilibrium is illustrated as numerical examples, presenting the influences of the changing power mix on electricity prices, renewable energy integration, carbon emissions and air pollutant emissions. Finally, some suggestions on future electrical and environmental policies are presented. [ABSTRACT FROM AUTHOR]