• Energy Research
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Abstract Many organizations in the world are interested in waste management problems and their potential solutions. In order to solve these problems, a Japanese venture company has developed an innovative thermal decomposer for organic wastes called ERCM (Earth-Resource-Ceramic-Machine). The ERCM reactor employs electron injected air to promote the thermal decomposition reaction, while the effect of electron injection into air has not yet been clarified. An experimental work was performed using a fixed bed reactor to explore the effects of different parameters of electron injection into air, the reaction temperature and different feedstock on the syngas generation. The main purpose of this study is to clarify the phenomena occurring in the ERCM reactor where a direct current electric field is produced in the flame reaction zone to enhance the thermal decomposition of wastes. In this regard, a mathematical model for simulating the thermal decomposition of solid waste in the presence of an electric field have been developed. The equations of aero-thermochemistry are coupled to the balance equations for densities of charged species, and the Poisson equation for the electrical potential is solved. The model was validated by the experimental data and showed a good agreement. The results showed that the electric field significantly improves the stabilization of the flame. From the release behavior of CO and CO2, it is noted that the electron injection would affect the char combustion process significantly. Finally the effect of the flame reaction zone generated by the field induced ion wind on the thermal decomposition was investigated.

Abstract Global energy consumption is increasing at a dramatic rate and will likely continue to do so. The major source of energy is still fossil fuel, which has resulted in the well-documented problem of global warming due to the emission of greenhouse gases from the burning of such fuel. Climate change and global warming are among the crucial and complex issues encountered by the world today, and they require an immediate solution. Technological innovation is the key to ensuring energy security without causing emissions and providing efficient cost-effective energy solutions. Power electronic technologies offer high reliability and renewable energy conversion efficiency, thus contributing to energy conservation, improving energy efficiency, and helping in the mitigation of harmful global emissions. This review focuses on various aspects of power electronic technologies and their importance in tackling carbon emission and global warming problems. The key topologies of power electronic converters are explained based on types, control difficulties, benefits, and drawbacks. Power electronic controllers utilized for energy conversion are comprehensively reviewed with regard to their structure, algorithm complexity, strengths and weaknesses, and mathematical modeling. The review focuses on power converters and controllers used in different applications and highlight their contributions to energy conservation, increasing the share of renewable energy sources, and mitigating emissions. Moreover, existing research gaps, issues, and challenges are identified. The insights provided by are expected to lead to the enhanced development of advanced power electronic converters and controllers for sustainable energy conversion. Such development can reduce carbon emissions and mitigate global warming.

Fossil fuel based power generation is and will still be the back bone of our world economy, albeit such form of power generation significantly contributes to global CO2 emissions. Solar energy is a clean, environmental friendly energy source for power generation, however solar photovoltaic electricity generation is not practical for large commercial scales due to its cost and high-tech nature. Solar thermal is another way to use solar energy to generate power. Many attempts to establish solar (solo) thermal power stations have been practiced all over the world. Although there are some advantages in solo solar thermal power systems, the efficiencies and costs of these systems are not so attractive. Alternately by modifying, if possible, the existing coal-fired power stations to generate green sustainable power, a much more efficient means of power generation can be reached. This paper presents the concept of solar aided power generation in conventional coal-fired power stations, i.e., integrating solar (thermal) energy into conventional fossil fuelled power generation cycles (termed as solar aided thermal power). The solar aided power generation (SAPG) concept has technically been derived to use the strong points of the two technologies (traditional regenerative Rankine cycle with relatively higher efficiency and solar heating at relatively low temperature range). The SAPG does not only contribute to increase the efficiencies of the conventional power station and reduce its emission of the greenhouse gases, but also provides a better way to use solar heat to generate the power. This paper presents the advantages of the SAPG at conceptual level.

Abstract Understanding the drivers of past and present energy consumption trends is important for a range of stakeholders, including governments, businesses and international development organizations, in order to prepare for impacts on global supply chains caused by changes in future energy price or availability shocks. In this paper we use environmentally-extended input–output tables to: (a) quantify the long-term drivers that have led to diversified energy footprint profiles of 186 countries around the world from 1990 to 2010; (b) identify which countries and sectors recorded an increase or decrease in energy footprints during this time period; (c) highlight the effect of international outsourcing of energy-intensive production processes by decomposing the structural and spatial change in energy footprints; and (d) discuss the implications for national economic policy for the identified drivers. To this end, we use a detailed Multi-Regional Input–Output database and three prevalent structural decomposition analysis methods. To reduce biases in the results due to time lapse and currency variations, we convert input–output tables to common US$ and 1990-constant prices. This study provides a broad overview of the magnitude and distribution of the drivers for energy footprints across countries. The results of this study demonstrate that for almost all countries affluence and population growth are driving energy footprints worldwide, which is in part counteracted by the retarding effect of industrial energy intensity. In particular, this study demonstrates that with increasing per-capita GDP, the total energy footprint of a country is increasingly concentrated on imports or consumption.

Abstract The present energy system faces at least two challenges. For one thing, the power system’s stability is challenged by the increasing penetration of variable renewable energies, especially wind power, due to its fluctuation and intermittency. For the other, the transport sector is facing enormous difficulty to decarbonize. This paper proposes a new energy system that integrates the hydrogen production and distribution system to the combined cooling, heating and power (CCHP) system with significant wind power to solve these two challenges simultaneously. The new energy system can meet the energy needs of the building. At the same time, the wind power utilization rate reaches 92.6%, and the typical daily hydrogen production capacity in winter, transition season and summer is 500 kg, 500 kg and 266 kg, respectively. The system’s energy efficiency is 72%, and the energy of the system is utilized efficiently. By comparison, the new system can reduce costs and carbon dioxide emissions, save primary energy, and effectively improve energy efficiency.

Abstract In the United States, natural gas-fired generators gained increasing popularity in recent years due to the low fuel cost and emission, as well as the proven large gas reserves. Consequently, the highly interdependency between the gas and electricity networks is needed to be considered in the system operation. To improve the overall system operation and optimize the energy flow, an interval optimization based coordinated operating strategy for the gas-electricity integrated energy system (IES) is proposed in this paper considering demand response and wind power uncertainty. In the proposed model, the gas and electricity infrastructures are modeled in detail and their operation constraints are fully considered, wherein the nonlinear characteristics are modeled including pipeline gas flow and compressors. Then a demand response program is incorporated into the optimization model and its effects on the IES operation are investigated. Based on interval mathematics, wind power uncertainty is represented as interval numbers instead of probability distributions. A case study is performed on a six-bus electricity network with a seven-node gas network to demonstrate the effectiveness of the proposed method; further, the IEEE 118-bus system coupling with a 14-node natural gas system is used to verify its applicability in practical bulk systems.

Abstract The clathrate hydrate formation from a model natural gas, i.e., a mixture of methane, ethane, and propane in a 90:7:3 molar ratio, under a constant pressure was experimentally investigated, focusing on the compositional evolution of hydrate crystals formed inside a gas-bubbling-type reactor during each semi-batch hydrate-forming operation. The experimental system used in this study was specially designed for obtaining several hydrate samples formed at different, arbitrarily selected stages during each hydrate-forming operation. Each hydrate sample was analyzed by a gas-chromatograph to determine the mole fractions of methane, ethane and propane encaged in the hydrate. These analyses revealed a monotonic increase in the methane fraction and decreases in the ethane and propane fractions during each operation until a quasi-steady state was established. Powder X-ray diffraction analyses showed that both structure-I and structure-II crystals were simultaneously formed during the quasi-steady period. The compositional evolution of the hydrates formed during the early stages before the quasi-steady state was reached deviated from corresponding predictions based on the thermodynamic-simulation scheme previously reported. A hypothetical explanation for the discrepancy between the experimental and simulation-based results was provided.

Abstract In energy distribution systems, thermal energy is usually transferred by a heat carrier fluid via pumps. Improper design and unreasonable control of pumping systems result in inefficient operation which accounts for a significant part of electricity consumption in the industry. The need to save energy has been sharpened the focus on improving energy efficiency in pumping systems. The application of a decentralized pumping system with the variable-frequency drive can be considered a technological improvement that has potential in saving energy compared to the conventional centralized pumping system. In this paper, a reduced-scale experimental apparatus and computational fluid dynamic model are used to investigate the energy saving potential of decentralized and centralized pumping systems. The energy-saving potential of decentralized configuration and two types of centralized configurations are then compared. The results showed that the decentralized pumping system consumes less power than centralized pumping systems under the same conditions. When the flow rate is reduced to 80%, the power consumption of the decentralized configuration decreases by 47% while the consumption for a centralized configuration with constant pressure control decreases by only 19%. The decentralized pumping system can offer higher energy-saving potential under variable flow rate conditions, which is expected to extend to other fluid delivery systems for improving efficiency. Moreover, the computational fluid dynamic simulation results correspond well with experimental results. The maximum discrepancies of the developed model for prediction of gauge pressure and system total pressure loss are 7.2% and 9% respectively, which confirms the accuracy and applicability of this model.

Abstract This study proposes a novel analysis framework to investigate the CO2 and SO2 emission efficiency, emission reduction potential, and marginal abatement cost (MAC) of 316 coal-fired power plants in China. The comprehensive analysis framework is based on the combined approach of utilizing the directional output distance function (DODF) and parametric linear programming (PLP). The average emission efficiencies of CO2 and SO2 were 0.48 and 0.61, respectively, which indicates that China’s coal-fired power plants have a large potential to reduce CO2 and SO2 emissions, on average by 52% and 39%, respectively. In 2010, the average CO2 and SO2 emissions reduction potential for the 316 investigated power plants were 1,517 kt and 3,773 t, respectively. The average MAC prices for CO2 and SO2 were estimated to be 598 yuan/tonne and 22,401 yuan/tonne, respectively, indicating that the reduction of such emissions is very expensive. Furthermore, I formulated an optimization problem for maximizing CO2 and SO2 emission reductions under the governmental budget constraint. Solving this optimization problem yielded the total cost for the maximum reductions of CO2 and SO2 emissions, the maximum possible reductions for CO2 and SO2 emissions for each allocated budget scale, and the optimal budget allocation for each power plant at a given budget scale. I finally suggest effective mitigation strategies for CO2 and SO2 emissions generated from China’s coal-fired power plants.