• Energy Research
• 7. Clean energy close
• Chinese Academy of Sciences close

An effective SiO2-protecting pyrolysis method for the synthesis of highly active meso/microporous Fe–N-CNF catalysts is presented.

Despite its high capacity as a promising candidate material for lithium‐ion battery anodes, SiOx (x < 2) has the limitation of low conductivity and large volume change during cycling of SiOx, leading to low lithium‐ion transport rate, electrode destruction, and thus poor lithium‐ion storage performance. Herein, a novel 3D vertical graphene@SiOx/B‐doped carbon (3DVG@SiOx/BC) composite microsphere with 3DVG grown on SiOBC microspheres prepared by the pyrolysis of liquid tris(trimethylsilyl) borate in a sealed vessel using thermal chemical vapor deposition is reported. SiOBC can be transformed into SiOx/BC with homogeneously dispersed subnanoscale SiOx and BC particles during heating. The subnanoscale BC particles in spheres and 3DVG surface provide a fast lithium‐ion transport path and a robust skeleton, with an ultrahigh lithium‐ion diffusion coefficient (1.7 × 10−9 cm2 s−1) and an ultralow volume change (13.8%). The 3DVG@SiOx/BC microspheres exhibit a high electrical conductivity (6.5 × 103 S m−1) and tap density (0.83 g cm−3) as well as a high capacity, long cycling life, and excellent rate capability as anodes in half/full cells. The full cell with LiCoO2 as the cathode shows a high gravimetric and volumetric energy density of 459.4 Wh kg−1 and 1167.9 Wh L−1, respectively.

Abstract Two models of a designed small size lead-cooled fast reactor (LFR) were built by RELAP5-HD to simulate the behavior of the reactor system during pump shutdown accidents, along with different levels of core blockage. Two typical pump shutdown accidents of pump rotor seizure accident and loss-of-pump-power accident were selected to do the simulation and analysis of the behavior of the nuclear power reactor during pump shutdown accidents, when all the safety systems were assumed to be unavailable. A one dimensional vessel-one dimensional core model was built to simulate the long term cooling condition of the pump shutdown accidents under the reactor shutdown or operation conditions. The simulation results would help to analyze whether pump accidents could cause core damage. In order to show the heat removing capability of the coolant in the reactor system, a more detailed one dimensional vessel-three dimensional core model was built to simulate the long term cooling condition of the pump shutdown accidents along with different levels of core blockage accidents.

Source apportionment studies of particulate matter (PM) link chemical composition to emission sources, while health risk analyses link health outcomes and chemical composition. There are limited studies to link emission sources and health risks from ambient measurements. We show such an attempt for particulate trace elements. Elements in PM2.5 were measured in wintertime Beijing, and the total concentrations of 14 trace elements were 1.3-7.3 times higher during severe pollution days than during low pollution days. Fe, Zn, and Pb were the most abundant elements independent of the PM pollution levels. Chemical fractionation shows that Pb, Mn, Cd, As, Sr, Co, V, Cu, and Ni were present mainly in the bioavailable fraction. Positive matrix factorization was used to resolve the sources of particulate trace elements into dust, oil combustion, coal combustion, and traffic-related emissions. Traffic-related emission contributed 65% of total mass of the measured elements during low pollution days. However, coal combustion dominated (58%) during severe pollution days. By combining element-specific health risk analyses and source apportionment results, we conclude that traffic-related emission dominates the health risks by particulate trace elements during low pollution days, while coal combustion becomes equally or even more important during moderate and severe pollution days.

In this work, heat production potential from hot dry rock by water circulating through two horizontal wells was numerically investigated based on the geological data of well DP23-1 under the enhanced geothermal system (EGS) project at Desert Peak geothermal field. The results indicate that the desirable electricity production power and energy efficiency can be obtained under suitable reservoir permeability, water production rate and injection temperature; meanwhile water flow impedance remains at a relative lower level. The sensitivity analysis indicates that the electricity production power mainly depends on the water production rate and the injection temperature; the water flow impedance mainly depends on the reservoir permeability, water production rate and injection temperature; the energy efficiency mainly depends on the reservoir permeability and the water production rate. The heat production performance will be improved when the reservoir permeability, the water production rate and the injection temperature are under reasonable conditions. However, this study is based on that the fractured reservoir is equivalent to a homogeneous porous medium and there is no water loss in the reservoir, so the practical energy output and efficiency of water circulating through two horizontal wells at Desert Peak geothermal field needs further study in the future.

AbstractAnchoring groups are extremely important in controlling the performance of dye‐sensitized solar cells (DSCs). The design and characterization of sensitizers with new anchoring groups, in particular non‐carboxylic acid groups, has become a recent focus of DSC research. Herein, new donorπacceptor zincporphyrin dyes with a pyridine ring as an anchoring group have been designed and synthesized for applications in DSCs. Photophysical and electrochemical investigations demonstrated that the pyridine ring worked effectively as an anchoring group for the porphyrin sensitizers. DSCs that were based on these new porphyrins showed an overall power‐conversion efficiency of about 4.0 % under full sunlight (AM 1.5G, 100 mW cm−2).

The Zhundong coalfield is a newly discovered superhuge coal deposit in China. Zhundong coal is considered as a potential resource for gasification, due to its high reactivity. However, the high sodium content in Zhundong coal could cause serious ash-related problems during its thermal utilization. This study was conducted to investigate the gasification characteristics and sodium transformation behavior of a typical high-sodium Zhundong coal. The gasification performance of Zhundong coal is greatly improved at elevated temperature, which is verified by both thermogravimetric analysis and bench-scale study in a bubbling fluidized bed reactor. Compared to Shigouyi coal, Zhundong coal shows better gasification reactivity at the same temperature, indicating better adaptability of Zhundong coal to fluidized bed gasification. Sodium in Zhundong coal chiefly exists as the water-soluble form. The temperature is a crucial parameter affecting the release and transformation of sodium. With increasing temperature, mo...

Abstract In this work, the cascaded supercritical CO 2 system integrated with solar and biomass energy is proposed. The system contains two parts, i.e. the recompression cycle and the simple cycle. The solar receiver or biomass burner replaces the combustor chamber in conventional Brayton cycle. Energy analysis and exergy analysis are implemented to evaluate the feasibility of the proposed system. Under the consideration of the changes of solar irradiations and biomass complementary, the design and off-design thermodynamic performances of the system are numerically studied. Results indicate that the thermal efficiency of total system reaches 40.1%. Owing to the introduction of biomass input in the proposed system, the power generation efficiency is insensitive to solar radiations and times, and thus an efficient and stable utilization approach of solar energy and biomass is achieved at all work conditions. The theoretical results indicate that the cascaded supercritical CO 2 with multi-energies input as a power cycle is a promising option for the efficient utilization of the abundant solar and biomass resources in the Western China.

To meet the requirement of the wind energy resource assessment and utilization, the statistical characteristics of wind climate in the China mainland were analyzed in this study by using observation wind dataset for 1971–2017 from the China Meteorological Administration (CMA). A series of key factors closely related to wind power development were analyzed, systematically including the spatial and temporal characteristic of wind speed, the distribution of wind speed at different density grades, the density of the cumulative distribution, strong wind days and weak wind days. The characteristics of wind patterns in different regions are also compares. Results indicate that: (1) the regions with the highest wind speed in China centrally locate in Northwest China, North China and Northeast China with the highest wind speed occurs in spring. The annual variation of wind speed in northern China is bimodal while in southern China it is unimodal. (2) The wind speed probability density distribution shows a significant spatial–temporal difference. The wind speed probability distribution is the most concentrated in spring for almost all regions. For each season, the concentrated and stable wind speed occurs in Xinjiang region in spring. While it appears in the region from Northwest China to the northern part of North China for summer and autumn, and in the southern part of North China and Central China for winter. In the case of equal cumulative probability, the highest wind speed locates in Northeast China and the lowest in Sichuan Basin. (3) For 1971–2017, the wind speed in all regions of China showed a decreasing trend on the whole. But this trend slowed down since 1990s. It is​ worth noting that the wind speed in some regions even increased since 2000. (4) The numbers of strong wind day have been decreasing in all regions, but the numbers of weak wind day demonstrate an evolutionary feature of a growth followed by decrease. In most regions, the numbers of weak wind day reached the maximum in the vicinity of 2000 and then decreased rapidly.