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Abstract Even though renewable energy development has gained momentum in China, thermal power generation still accounts for approximately 70% of the county's total power generation serving as the major source of carbon dioxide (CO2) emissions in China. Facing the challenges of meeting 2030 peak target of CO2 emission and realizing the coordinated development of thermal power generation in Beijing-Tianjin-Hebei region, this paper applies generalized Divisia Index Method (GDIM) to decompose the dynamics in the relevant CO2 emission. The effects of five factors including electricity demand, energy consumption, technology, energy efficiency and energy-mix are considered. The decomposition suggests that electricity demand is the primary factor driving the CO2 emission up, whereas technology effect decreases CO2 emission the most. Given the significant roles of technology, energy-mix and energy efficiency in CO2 emissions reduction, seven scenarios are designed to identify the optimal coordinated development pathway for thermal power generation in Beijing-Tianjin-Hebei region. Through upgrading energy structure and/or enhancing energy efficiency, the thermal power generation in Beijing-Tianjin-Hebei region can achieve coordinated development and realize the 2030 peak target under four scenarios. The detailed development pathways for CO2 emissions and specific policy implications for Beijing, Tianjin and Hebei are provided to further govern CO2 emissions and maintain sustainable development.

Coalbed methane (CBM) resources cannot be efficiently explored and exploited without a robust understanding of the permeability of fracture-size heterogeneities in coal. In this study, two sister coal samples were imparted with pre-developed cleat and connected fractures, and the permeability of the coal samples was measured under different conditions of controlled confining and gas pressures. Furthermore, the implications of the results for CBM exploration and exploitation were discussed. The permeability of coal with cleat development ranged from 0.001–0.01 mD, indicating ultra-low permeability coal. The gas migration in this coal changed from a linear flow to a non-linear flow, with the increase in gas pressure (>1 MPa). Thus, the permeability of the coal initially increased and then decreased. However, the Klinkenberg effect does not exist in this ultralow-permeability coal. For the coal sample with connected fracture, permeability ranged from 0.1–10 mD, which is larger by hundred orders of magnitude than that of the sample with cleat. For this coal, with a decrease in gas pressure (<1 MPa), the Klinkenberg effect significantly increased the permeability of the coal. With an increase in the applied confining pressure, both the Klinkenberg coefficient and permeability of the coal presented a decreasing trend. It is suggested that field fracture investigation is a prerequisite and indispensable step for successful CBM production. The coal beds that cleat network is well conductive to the connected fracture can be an improved target area for CBM production. During CBM production, a variety of flow regimes are available owing to the decrease in CBM reservoir pressure. In particular, under the low CBM reservoir pressure and low in situ geo-stress conditions, the gas migration in the CBM reservoir with connected facture development exhibits remarkable free-molecular flow. Thus, the reservoir permeability and predicted CBM production will be enhanced.

Abstract This study evaluated the feasibility of ethanol production from expired rice by surface immobilization technology fermentation. The process was carried out using temperature tolerant active fresh yeast TH-AADY cells immobilized on cotton fiber placed in a reticular hollow sphere. A 320-ton pilot reactor with a multi-layer packed bed immobilized structure and multi-branch circulation path was used instead of the typical cylindrical immobilized reactor. The average values of the alcohol degree and fermentation efficiency of the immobilized yeast cells were 12.46% (v/v) and 83.72%, respectively, which were 0.45% (v/v) and 3.2% higher than those of a free-cell fermentation. The fermentation was repeated for 32 batches with good reusability and long-term stability. In addition, fermentation via cell immobilization created an extra benefit of 6.37% per ton of fuel alcohol based on the mean market price in China. The results obtained in this study indicate that ethanol production from expired rice using immobilized yeast in the new bioreactor is feasible and may meet the demands of industrial production based on the fermentation indexes and economic evaluation.

Abstract Wind-induced vibration (WIV) and power extraction performances of a circular cylinder with symmetrically installed fin-shaped rods (FSR) were experimentally and numerically investigated under different coverages. The FSR coverage which is expressed as an angle (α) is measured from the upstream edge to the downstream edge of the rod. The effect of FSR installation angle (θ) which is the angle from the stagnation point of cylinder to the upstream edge of the rod was also considered in this work. The FSR cylinder is exposed in uniform wind and allowed to vibrate in cross-flow direction. The output electric power is realized by piezoelectric patch. It is found that, for most cases, the output power of FSR cylinder increases monotonously with the rise of α for a given wind velocity (U). In addition, the tendency of output voltage varies with the wind velocity is highly similar to that of output power. The maximum values of output voltage and power are 19.70 V and 1.90 mW can be obtained when α= 20° (θ= 60°). The WIV responses of FSR cylinder show that the amplitudes of FSR cylinder increase with the rise of α for low installation angle (θ= 0°, 30°) and the maximum amplitudes exceed 2D (D: diameter of circular cylinder) can be observed for α= 40°/50° (θ= 30°) and α= 20° (θ= 60°). The reduced frequency of cylinder for θ= 0° and 30° does not sensitive to the coverage (α). It is worth noting that multiple frequencies can be captured for high coverage. Due to the boundary layer separating point moves in downstream direction with the increase of U and α, the vortex pattern switches from 2S to 2P.

Considering multiple transmit antennas in each distributed antenna unit (DAU), two power allocation (PA) schemes are proposed for energy efficiency (EE) maximization for downlink distributed multiple-input single-output (DMISO) systems with orthogonal frequency-division multiplexing (OFDM) over frequency-selective fading channels, where the power constraints for individual antenna units are addressed. The optimization problem for the maximization of the EE subject to per-antenna maximum power constraints is formulated. By means of linear programming, the optimization is simplified to as if for a DMISO system whose DAUs use a single antenna corresponding to the largest channel-gain-to-noise ratio (CGNR) for transmission. Using the block coordinate descent (BCD) method, an iterative optimal PA scheme to the simplified optimization problem is derived, where an efficient procedure for determining the number of effective subcarriers and the optimized PA is developed. Since the optimal scheme needs iterative calculations, a closed-form suboptimal PA scheme is also derived by sorting the total CGNR and using the principle of the BCD method. Interestingly, this suboptimal scheme has small performance loss in comparing with the optimal scheme, and its relative EE loss is decreased with the number of subcarriers. Moreover, these two schemes include the ones with single transmit antenna for distributed antenna systems as special cases. Computer simulations verify the effectiveness of the two proposed schemes, and the proposed optimal one can obtain the same performance as the existing optimal scheme for DMISO-OFDM but with lower complexity.

Heat recovery of air ventilation is a means of energy conversation in buildings. In the present paper, a plastic film heat recovery ventilator that works under cross-flow mode was developed. The thin film vibrates when airflow passes through the channels, which enhances heat exchange performance. Experiments, as well as theoretical analyses, were carried out to study the performance of such a unit. Results show that the effectiveness of the heat exchanger varies from 0.65 to 0.85 with airflow rate and the pressure drop is less than 20.0 Pa. Film vibration induced by airflow can improve heat transfer. The extent of the enhancement is proportional to film vibration intensity that increases with airflow rate while decreases with film thickness.

Green ammonia is gaining momentum as a globally significant technology for deep decarbonisation. In this thesis, several models are developed across chemical, techno-economic, and energy system modelling disciplines to explore the future role of green ammonia. First, standalone models of production (i.e., power-to-ammonia) and re-electrification (i.e., ammonia-to-power) are developed and compared to competing technologies. Second, these models are integrated into a planning and dispatch energy system model (ESM) of India to 2050. The ESM has several novel additions including the sector coupling of hydrogen and ammonia, multiple years of granular weather data, and learning-curve-based technology cost forecasts. India is chosen as an ideal case study given its globally unmatched demand growth in all three relevant sectors: electricity, green hydrogen, and green ammonia. The projected electricity demands for green hydrogen and ammonia production account for 25% of the total Indian electricity demand in 2050, underscoring the transformational potential that green hydrogen and ammonia sector coupling can have on the Indian energy system. The results of the state-of-the-art ESM highlight synergistic effects of hydrogen and ammonia sector coupling with the power system. The least-cost system employs seasonal green ammonia production paired with up to 40 million tonnes (i.e., 200 TWh) of ammonia storage, as well as some re-electrification via gas turbines. Sector coupling reduces system curtailment, addresses challenges of long-duration storage, and improves system resilience to interannual weather variations. While India is a crucial case study from a global decarbonisation perspective, the methodology and findings are generally applicable, and it is the aim of this work to motivate and accelerate the wider research community into considering the potential impacts of green ammonia sector coupling on electricity grid design. Finally, this work highlights strategic technology development direction for ammonia producers and gas turbine manufacturers, as well as implications for policymakers.

AbstractStratified thermal energy storage (TES) tanks are widely used in thermal power plants to enhance the electric power peak load shifting capability and integrate high renewable energy shares. In this study, a data‐driven surrogate modeling and optimization study of the unequal diameter radial diffuser previously proposed by the present authors is conducted. First, based on the orthogonal experimental design, numerical experiments are performed to generate the performance database. Then, the database is used to establish the data‐driven surrogate model via the support vector machine. Subsequently, the single‐objective optimization and multiobjective optimization of an unequal diameter radial diffuser are conducted using the genetic algorithm. For the single‐objective optimization, the optimal thermocline thickness is 0.829 m when the diameter ratio of the long baffle and the tank is 0.426, the diameter ratio of the short baffle and the long baffle is 0.823, and the distance between the two baffles is 228.51 mm. For multiobjective optimization, the obtained Pareto optimal solutions are obtained. Under the premise of maintaining excellent thermal stratification, the selected Point C can reduce the steel cost by 88.1%. The research results are helpful for designing efficient and economical unequal diameter radial diffusers for TES tanks.

Voluntary environmental management programs for firms have become an increasingly popular instrument of environmental policy. However, the literature’s conclusion on the effectiveness of suchprograms is ambiguous, and for the European region there is a lack of evidence based on a large control group. We seek to fill this gap with an evaluation of the Eco-Management and Audit Scheme (EMAS), introduced in 1995 by the European Union as a premium certification of continuous pro-environmental efforts above regulatory minimum standards. It is more demanding than other voluntary programsdue to annual public reports of the environmental performance and targets for improvements. We use official firm-level production census data on the German manufacturing sector, a major energy consumer and emitter in Europe. To account for the self-selection of firms, we combine the Coarsened Exact Matching approach with a Difference-in-Differences estimation. Our results do not suggest reductions of firms’ CO2 intensity and energy intensity neither before nor after certification. Moreover, program participants do not increase renewable energy consumption or investments into the protection of the environment and climate. Our results are robust to a variety of checks and call into question the effectiveness of the EMAS program concerning these particular outcome variables.