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Abstract Compared with other traditional energy sources, renewable energy, which results the less pollution and has numerous resources, is a significant factor in addressing the current issues of the serious environmental pollution and the resource depletion. Large-scale renewable energy integrated to the grid could bring change in both morphological structure and operation modes of energy transmission. Therefore, it is necessary to research the evolution mechanism of the future transmission network with a high proportion of the renewable energy. In this paper, an evolution framework of power system with high proportion of renewable energy is proposed. Firstly, a network equivalence and simplification based on power transfer distribution factors (PTDFs) is proposed, which can effectively simplify the decision-making process of evolution of large-scale power system. Then, an annual production simulation (8760 h) which takes into account renewable energy and load fluctuations is used to find out the bottleneck of the power grid. Based on the above methods, evolution strategy of power system with high proportion of renewable energy is studied for finding out optimal expansion strategy. A real power system of Zhejiang province is used as a test system. Test results demonstrate the feasibility of the proposed evolution framework.

Abstract To alleviate the shortage of natural gas resource and ease carbon emissions, a novel solar-driven combined cooling, heating and power (CCHP) system is designed and optimized using the genetic algorithm in the work. Different from the process of direct combustion in a conventional CCHP system, natural gas is firstly converted into syngas by a solar-driven natural gas reforming step, which is consumed in an efficient tri-generation system. Energy, economic and environmental evaluations on five office buildings in different climate zones in China are implemented to validate the advantages of the proposed system. Results show that the annual maximum primary energy saving, total cost saving, and CO2 emission reduction are 69.76%, 49.80%, and 71.55%, respectively. The system located in severe cold zones, where solar energy is abundant and building requires more heat load in whole year, achieves the highest benefits in comparison with separate systems. Furthermore, the sensitivities on the price fluctuations of electricity, natural gas and solar field to the system profits are investigated, which indicates that the influence of electricity price on the system performance is the most significant. Thus, a promising method for reducing the natural gas consumption and improving the utilization efficiency of solar energy is provided.

Abstract A recent field survey provided eight typical soffits used in the residential houses within the typhoon-prone coastal region of southeastern China. Their aerodynamic effects in alleviating rooftop extreme wind pressures were evaluated via wind tunnel testing on a series of 1/20 gable roof house models. Local pressures, area-averaged pressures and uplift forces acting on roofs were examined. Results showed that in contrast to the model without soffits, the presence of these gutters or eaves gives a rise to a significant reduction of negative peak wind pressures at edges and corners near them. However, they hardly impact wind loads on the other roof surface. Some minor simple architectural elements attached to eaves, such as cantilevered spoiler and semicircular gutter, were observed to facilitate the reduction of extreme wind pressure at edges and corners. Additionally, the reduction rate of spatially averaged wind pressures with area was found to be dependent on the size of tributary area, rather than the shape of tributary area.

In a former study, a German lignite extract exhibited toxicity to Danio rerio and Caenorhabditis elegans and was shown to have mutagenic and dioxin-like activity. Besides the comparatively low content of known toxic polycyclic aromatic hydrocarbons (PAH), highly intensive peaks of m/z 274 and m/z 324 were observed during the chromatographic analysis. These compounds are assumed to be alkylated chrysenes and picenes (3,3,7-trimethyl-1,2,3,4-tetrahydrochrysene, 1,2-(1'-isopropylpropano)-7-methylchrysene and an isomer of the latter, 1,2,9-trimethyl-1,2,3,4-tetrahydropicene and 2,2,9-trimethyl-1,2,3,4-tetrahydropicene). These compounds are intermediates in the diagenetic formation of chrysene and picene from triterpenoids. Due to their general high abundance in lignites and the toxicity observed for the lignite extract, the mechanism-specific toxicity and bioavailability of these compounds were investigated in the present study using the approach of effect-directed analysis. After the separation of the compounds from other PAH, their mutagenic activity (Ames Fluctuation test) and dioxin-like activity (EROD activity) were studied. Both, mutation induction factor (up to 2.9±2.7) and dioxin-like activity (Bio-TEQ of 224±75 pg/g; represents the amount (pg) 2,3,7,8-tetrachlorodibenzo-p-dioxin per g coal that would provoke the same toxic effect) were rather low. Bioavailability estimated by the bioaccumulation test with Lumbriculus variegatus was also very limited. Based on the obtained results, the environmental risk of the highly abundant alkylated chrysenes and picenes in lignites is concluded to be low.

Abstract Spark-ignition (SI) aviation piston engines are widely used on light helicopters and unmanned aerial vehicles (UAVs) because of the high-power density and ultra-high cost performance. Kerosene with high flash point is expected to improve safety of aforementioned aircrafts by replacing gasoline. However, in spark-ignition mode, kerosene is difficult to mix and is easy to knock. Short-chain alcohols have high volatility and octane number which can just make up for some defects of kerosene. In this paper, three kinds of alcohols including ethanol, n-propanol and n-butanol were blended with aviation kerosene (RP-3) by volume fraction of 30%, 50%, 70%, respectively. The combustion and emission characteristics of the blended fuels were deeply studied on a typical spark-ignition aviation piston engine. Meanwhile, engine performance fueled with commercial gasoline was also tested for comparison. Results indicated that alcohol/kerosene blends could reach higher brake thermal efficiency (BTE) (alcohol ratio ≥50%) compared to gasoline. Carbon monoxide (CO) and nitrogen oxides (NOx) emissions of blended fuels expressed dramatically descending. With the increase in alcohol ratio, the CO, hydrocarbons (HC) and soot emissions gradually decreased. The brake thermal efficiency showed an upward trend with the increase of alcohol ratios. The brake thermal efficiency of E70, P70 and B70 were increased by 2.15%, 3.52% and 6.51%, and the CO emissions of E70, P70 and B70 were reduced by 39.8%, 38.5% and 49.0%, respectively, compared to those of gasoline. Notably, n-butanol/kerosene blends exhibited the better combustion and emission characteristics, which had the higher efficiency and lower CO, HC and soot emissions.

Abstract In arid areas, dry cooling technology is a preferable alternate of wet cooling mainly owing to the scarcity of abundant water supply. However, the supercritical CO2 power cycle still offers considerable thermal performance even at higher ambient temperature using dry cooling. The novelty of this work is the exhaustive designing of dry cooler for supercritical CO2 cycles (recompression and partial cooling) in concentrating solar power application. Prior to the design of tower, a preliminary analysis is conducted in achieving the optimum main compressor inlet temperature (33 °C-recompression and 40 °C-partial cooling) at which the cycle delivers the maximal efficiency. The comparison is performed at same higher and lower pressure and for the partial cooling, the intermediate pressure is optimized. At relatively higher compressor inlet temperatures (above 50 °C), the partial cooling achieves higher efficiency while at lower temperatures (30–49 °C), the recompression shows superior performance. An iterative nodal method is used for the air-cooled finned tube heat exchanger units that takes account of the dramatic variation in thermodynamic properties of CO2 with the bulk temperature. Kroger’s detailed methodology of designing dry cooler is adapted with the implementation of nodal approach for CO2 property variation. A dry cooling tower with 52.45 m height is essential for the recompression cycle, whereas the partial cooling requires two towers of the height of 35.4 m and 38.7 m. A thermal assessment is carried out on the dry cooler under various cycle fluid inlet temperatures and ambient temperatures. During hot and humid ambient conditions, lower compressor inlet temperatures (up to 53.1 °C) are obtained with the recompression cycle compared to partial cooling (up to 64.5 °C). In extreme climate condition of 50 °C air temperature, the recompression cycle provides superior thermal efficiency (46.5% against 45.5%). For future commercialization of dry cooled sCO2 power plant, the recompression cycle is preferred due to its superior performance and lower capital cost for cooling tower design and solar field. The work demonstrates the impact of dry cooling tower design strategy in the context of cycle thermal assessment under various working condition.

Abstract Comprehensive information about the concentrations, distribution, and modes of occurrence of elements in coal are important from the environmental and economic point of view. Although a great number of previous studies have investigated the geology of coalbed methane in the Qinshui Basin, only a few studies focused on the inorganic constituents in coal. More specifically, the mode of occurrences of valuable element Li in the No. 3 Coal is still unclear, although Li was found enriched. In this study, we present mineral characteristics, as well as multi-element data on the Permian No. 3 Coal from the Sucun and Gaohe Mines, Changzhi City, southern Qinshui Basin. The studied coals are characterized by low- to medium-ash yield (Ad = 5.72%- 28.18%, 12.34% on average), low volatile matter yield (Vdaf = 8.49–15.17%, 10.96% on average), suggesting a low volatile bituminous coal to semi-anthracite. NH4-illite and kaolinite are the main minerals in the coals detected by XRD, and trace amount of minerals calcite, dolomite, quartz, pyrite and diaspore can also be found. The major elements of the studied No. 3 coals are dominated by SiO2 and Al2O3, ranging 2.49–16.45 wt% and 2.13–12.9 wt% (on a whole-coal basis), respectively. Li is enriched in the No. 3 coals (5

AbstractBy using the data of 30 provinces from 1998 to 2016 in China, this paper estimates the water rebound effect in the agricultural crop farming by combining Slacks‐based Measure (SBM‐based) of Malmquist Index and Logarithmic Mean Divisia Index (LMDI) method. We find that the average water rebound effect is 70.3%, implying that over two‐thirds of the water saving from irrigation technology improvement is offset by higher water consumption. We find evidence on the regional heterogeneity in terms of the magnitude of rebound: Southwest is the highest, whereas Northwest is the lowest. The heterogeneous rebound effect across regions is mainly due to the difference in water endowment and irrigation land availability. Our results indicate that irrigation technology improvement is not necessarily sufficient for achieving agricultural water conservation. In particular, the difference in natural geography conditions across regions needs to be considered in designing water conservation policies at a sub‐regional level.

Abstract Fouling is one of the most significant problems for internally enhanced tubes installed in the shell and tube condensers. Due to the lack of long-term test data, current fouling models are developed based on accelerated particulate fouling tests that have the low precision and hence are inapplicable for predicting combined fouling in most practical cooling tower systems. In addition, the constant values of fouling resistance (factor) recommended by the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) are extremely limited under different operating conditions. To overcome these challenges, this research developed and validated two fouling prediction models based on experimental long-term tests. One of the models was in the form of a ratio of asymptotic fouling resistance of the enhanced tube to that of the plain tube ( R f ∗ / R f , p ∗ ), and the other one was in the form of the asymptotic fouling resistance of the directly enhanced tube ( R f ∗ ). Both models considered water quality, water velocity, and the tube geometries as the variables with the acceptable accuracy for prediction. 1) For the water quality, the parameter of valid concentration ( C com ) of cooling water was defined in this study, which reflected the potential amount of valid components to form the fouling. 2) For the water velocity, its impacts on the two critical parameters of the fouling process: sticking probability ( P ) and deposit bond strength ( ξ ) were investigated using experimental studies. Test results showed that in enhanced tubes with the increased water velocity the sticking probability ( P ) decreased continuously while the deposit bond strength (ξ) initially increased, and then, decreased. 3) For the tube geometries, by taking the parameters of tube geometries as variables the multi-variable correlations of the sticking probability ( P ) and deposit bond strength ( ξ ) were developed. From the results the generalized fouling prediction model as a ratio of asymptotic fouling resistance ( R f ∗ / R f , p ∗ ) was recommended for the application in HVAC&R industry due to its suitability and accuracy in practical project applications.