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Open Access Publications from the University of California

Scholarly Works (33 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2020)

This dissertation focus on the classification of topological matters in static and periodically driven systems.

First, we build a complete topological classification of local unitary operators in free fermionic systems. This result can be encoded in a periodic table with a period of eight, similar to the periodic table of topological insulators. In our classification, we define two local unitaries in a certain symmetry class to be topologically equivalent if they can be connected via finite time evolutions (locally generated unitaries) without breaking the symmetries of the symmetry class while maintaining locality. In this way, the classification we derive will allow us to distinguish locally generated unitaries from those that cannot be locally generated.Besides, we also how to find possible generating Hamiltonians for locally generated unitaries. These results can be used to study the edge behaviors of Floquet systems.

Second, we propose bulk invariants and edge invariants that are locally computable and improve existing topological invariants by being applicable to systems with the disorder. Afterward, we set up a rigorous connection between bulk and edge invariants for Floquet systems belonging to Class AIII and class AII of the Altland-Zirnbauer symmetry classification.

Last, after treating a static system as a Floquet system generated by a constant Hamiltonian, we employ the tools we developed in Floquet systems to classify the edge behaviors in static systems.

    Cover page: Classification of Static and Driven Topological insulators
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2018)
    China's economy has entered a “new normal,” characterized by slower economic growth and widespread overcapacity in its industrial sectors. Nevertheless, construction of power plants, especially coal-fired plants, continues at a rapid pace. Our analysis examines the extent of overcapacity in China's regional electricity grids. We show that already in 2014, the average reserve margin across China's regional grids was roughly 28%, almost twice as high as a standard planning reserve margin in the U.S. In addition, we find large variations in reserve margins across regional power grids in China, with the highest reserve margin (64%) in the Northeastern grid. This paper examines future reserve margins across regions in China under three growth scenarios. The results suggest that the majority of China will not need new baseload coal power (at least for reliability purposes) before 2020, and potentially not until 2025, under the low- and mid-growth scenarios. Under the high-growth scenario, China's central and eastern regions will need to import more power or built new capacity by 2020. As China's energy sector enters this new normal, our results highlight the growing importance of establishing mechanisms — planning processes and markets — that coordinate generation and transmission investments across grid regions, and that align the country's energy sector investments with its longer-term air quality and climate goals.
      Cover page: A regional analysis of excess capacity in China’s power systems
      • Article
      LBL Publications (2016)
        Cover page: Excess Capacity in China’s Power Systems: A Regional Analysis:
        • Article
        • Peer Reviewed
        Energy Analysis Env Impacts (2020)
        A structural shift to the tertiary sector and production reduction in heavy industries slow growth in electricity consumption in China. GDP remains as the leading factor driving electricity demand. It is projected an annual growth rate of 3.1 percent to 5.1 percent for electricity consumption in China by 2020, given that key features in China's economic transition are likely to continue in the foreseeable future. There exist regional patterns in electricity demand growth, separating the more developed regions along the eastern coast and the less-developed inland regions, due to different economic and demographic trends.
          Cover page: Regional electricity demand and economic transition in China
          • Article
          • Peer Reviewed
          UC Berkeley Previously Published Works (2019)
          Forecasts indicate that China's non-carbon dioxide (CO2) greenhouse gas (GHG) emissions will increase rapidly from the 2014 baseline of 2 billion metric tons of CO2 equivalent (CO2e). Previous studies of the potential for mitigating non-CO2 GHG emissions in China have focused on timeframes through only 2030, or only on certain sectors or gases. This study uses a novel bottom-up end-use model to estimate mitigation of China's non-CO2 GHGs under a Mitigation Scenario whereby today's cost-effective and technologically feasible CO2 and non-CO2 mitigation measures are deployed through 2050. The study determines that future non-CO2 GHG emissions are driven largely by industrial and agricultural sources and that China could reduce those emissions by 47% by 2050 while enabling total GHG emissions to peak by 2023. Except for F-gas mitigation, few national or sectoral policies have focused on reducing non-CO2 GHGs. Policy, market, and other institutional support are needed to realize the cost-effective mitigation potentials identified in this study.
            Cover page: China’s Non-CO2 Greenhouse Gas Emissions: Future Trajectories and Mitigation Options and Potential
            • Article
            • Peer Reviewed
            LBL Publications (2022)
            Renewable energy is poised to play a major role in achieving China's carbon neutrality goal by 2060; however, reliability and flexibility is a big concern of a renewable-dominant power system. Various strategies of enhancing flexibility are under discussion to ensure the reliability of such a system, but no detailed quantitative analysis has been reported yet in China. We combine the advantages of a capacity expansion model, SWITCH-China, with a production simulation model, PLEXOS, and analyze flexibility options under different scenarios of a renewable-dominant power system in China. We find that a larger balancing area offers direct flexibility benefits. Regional balancing could reduce the renewable curtailment rate by 5-7%, compared with a provincial balancing strategy. National balancing could further reduce the power cost by about 16%. However, retrofitting coal power plants for flexible operation would only improve the system flexibility marginally.
              Cover page: Large balancing areas and dispersed renewable investment enhance grid flexibility in a renewable-dominant power system in China
              • Article
              • Peer Reviewed
              LBL Publications (2019)
              China's electricity system is the world's largest, in terms of installed generating capacity, and is also the world's largest single source of greenhouse gas emissions. In 2015, China embarked on reforms in its electricity sector that aim to introduce market mechanisms in wholesale pricing. This study provides a quantitative assessment of the economic and carbon dioxide (CO2) emission impacts of transitioning to electricity markets in China, focusing on Guangdong Province. We find that market reforms deliver significant annual cost savings (21 to 63 billion yuan, 9%–27% reduction in total costs in a base case) to consumers in Guangdong, with smaller production cost savings (12 billion yuan, 13% reduction in production costs in a base case). Savings for consumers are accompanied by a large reduction in net revenues for coal and natural gas generators, raising concerns about generator solvency, longer-term resource adequacy, and the need for transition mechanisms. Market reforms increase CO2 emissions in Guangdong, as a result of gas-to-coal switching, though higher hydropower imports from neighboring provinces could offset these emissions. CO2 pricing has a limited impact on CO2 emissions in the short run and has the potential to lead to significant wealth transfers. The most important benefit of market reforms will be in providing an economic framework for longer-term operations and investment.
                Cover page: Economic and carbon emission impacts of electricity market transition in China: A case study of Guangdong Province
                • Article
                • Peer Reviewed
                LBL Publications (2020)
                China, whose power system accounts for about 13% of global energy-related CO2 emissions, has begun implementing market-based power-sector reforms. This paper simulates power system dispatch in China's Southern Grid region and examines the economic and environmental impacts of market-based operations. We find that market-based operation can increase efficiency and reduce costs in all Southern Grid provinces—reducing wholesale electricity costs by up to 35% for the entire region relative to the 2016 baseline. About 60% of the potential cost reduction can be realized by creating independent provincial markets within the region, and the rest by creating a regional market without transmission expansion. The wholesale market revenue is adequate to recover generator fixed costs; however, financial restructuring of current payment mechanisms may be necessary. Electricity markets could also reduce the Southern Grid's CO2 emissions by up to 10% owing to more efficient thermal dispatch and avoided hydro/renewable curtailment. The benefits of regional electricity markets with expanded transmission likely will increase as China's renewable generation increases.
                  Cover page: Economic and environmental benefits of market-based power-system reform in China: A case study of the Southern grid system
                  • Article
                  • Peer Reviewed
                  Bldg Technology Urban Systems (2019)
                  This paper conducts panel analysis to evaluate the effects of a structural economic shift from the industrial to the tertiary sector, a reduction in industrial overcapacity, and improvements in energy efficiency on energy consumption using data for 30 Chinese provinces from 1995 to 2015. We find that, at the national level, the structural shift to the tertiary sector, the reduction in cement and steel production, and the increase in energy efficiency in the industrial sector all have statistically significantly negative effects. We also divide the sample into three geographic and economic regions to evaluate regional differences. We find that the gross domestic product (GDP) share of the tertiary sector shows its greatest impact on reducing energy consumption in the eastern region, a decline in heavy industry production would reduce energy demand more in the central region, and improvement in industrial electricity efficiency would also help reduce energy consumption the most in eastern China. We also forecast energy consumption in China will reach 4.8–4.9 billion tonnes of coal equivalent (tce) in 2020 and further grow to 5.0–5.4 billion tce in 2030.
                    Cover page: Economic Transition, Technology Change, and Energy Consumption in China: A Provincial-Level Analysis
                    • Article
                    LBL Publications (2017)
                      Cover page: A Review of the American Recovery and Reinvestment Act Smart Grid Projects and Their Implications for China:
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