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The fluctuation characteristics of wind, solar and electric load in microgrid are predicted by BP neural network. Based on forecast error, an economic robust optimization model is established considering uncertain variables, flexible load and carbon emission, solving by C&CG algorithm, which adjusted for individual uncertainty degree and overall conservatism of variables. The power of gas turbine is closely related to time-of-use price while the power of energy storage depends on the relationship of electrovalence and operation cost and flexible load is transferred to valley consumption time. As overall conservatism increases, the electricity purchase increases where microgrid refers to buy more electricity to resist risks, leading to 1897.4 yuan and 1007.2 kg of carbon emission added. Robust scheduling has lower costs compared to intra-day scheduling of 14.2 % decreasing when the intra-day electrovalence increases. Considering carbon quota constraint dispatching is more inclined to utilize gas turbine and energy storage while the total cost would rise by 247.6 yuan. With changing the operating cost of gas turbine, a balance point could be obtained in the game between economy and carbon emission. And there would exist an optimal equipment operation strategy when carbon emission is sufficiently enough, which realizes a balance of energy-carbon-economy. • Use neural network prediction errors as uncertainty set for robust day-ahead optimization. • Realize uncertainty degree adjustment for multi-variables and overall conservatism changing. • Explain the operation law along with boundary conditions of energy equipment under time-of-use price. • Obtain a balance point of economy and carbon emission simultaneously together with energy distribution. [ABSTRACT FROM AUTHOR]

• A heterogeneous energy coupling model is established for optimal operation and configuration. • Annual 8760 data of wind, solar and load are achieved and utilized. • Waste heat originated from CCHP is harvested by ORC system. • Carbon Singular Point shows the directionality of multi-objective optimization. Integrated energy system characterizes with improving cascade utilization rate of energy and efficient energy conservation and substantial carbon reduction. Aiming at the total annual cost and annual carbon emission of integrated energy system, the capacity optimal configuration model of integrated energy system based on the principles of cooling determining heat and heat determining electricity is established in this paper, considering energy complementary coupling characteristic and distribution ratio. Moreover, Non-dominated Sorting Genetic Algorithm-II combined with Technique Order Preference by Similarity to an Ideal Solution comprehensive solution model is adopted to achieve the optimal solution under Pareto solution set. The configuration result reflected that renewable energy is preferred, and there are more electricity storage devices with less electricity equipment. Furthermore, the optimal operation schemes of three typical season days are analyzed and compared, specifically presenting the effectiveness of the operation strategy proposed in this paper. In addition, waste heat originated from integrated energy system and harvested by ORC is analyzed herein, which highlights generating electricity with 2.19 × 104 kWh totally participating in operation of power subsystem and reducing CO 2 emissions by 15.056 tons. Furthermore, the sensitivity of carbon emission factors is analyzed, achieving that there is a Carbon Singular Point with 0.18 kg/kWh of natural gas emission and 0.98 kg/kWh of power grid emission respectively in the optimization process, which is significant for multi-objective optimization and construction of Integrated energy system. [ABSTRACT FROM AUTHOR]

This paper presents an unsteady numerical study of the unsteady flow in the unscalloped radial turbine cavity considering the effect of computational sector size and sealing flow rate. A simplified U-shaped cavity with vanes and blades was simulated and the sealing efficiency was obtained using additional variables method. Unsteady low-pressure structures exist under a certain sealing flow rate, which is similar with axial turbine cavity, while the impact area is much larger. A comparison of computational domains sizes for 60° and 360° shows that whether the sector model can accurately predict the flow field depends highly on the number of low-pressure structures. As the sealing flow rate increases, the number and the speed of low-pressure structures at high radius decrease, and the corresponding low-frequency amplitude increases initially but decreases subsequently. The speed of low-pressure structure is positively correlated with its number, which seems contrary to the phenomenon observed in the axial turbine cavity. [ABSTRACT FROM AUTHOR]

The electromagnetic shielding effectiveness of kenaf fiber based composites with different iron oxide impregnation levels was investigated. The kenaf fibers were retted for removing the lignin and extractives from the fibers and magnetized. Using the unsaturated polyester and the magnetized fibers, kenaf fiber based composites were manufactured by the compression molding process. The transmission energies of the composites were characterized when the composite samples were exposed under the irradiation of electromagnetic (EM) wave with a variable frequency from 9 GHz to 11 GHz. Using the Scanning Electron Microscope (SEM), the iron oxide nanoparticles were observed on the surfaces and inside the micropore structures of single fibers. As the Fe content increased from 0% to 6.8%, 15.9% and 18.0%, the total surface free energy of kenaf fibers with the magnetizing treatments increased from 44.8 mJ/m 2 to 46.1 mJ/m 2 , 48.8 mJ/m 2 and 53.0 mJ/m 2 , respectively, while the modulus of elasticity reduced from 2875 MPa to 2729 MPa, 2487 MPa and 2007 MPa, respectively. Meanwhile, the shielding effectiveness was increased from 30–50% to 60–70%, 65–75% and 70–80%, respectively. [ABSTRACT FROM AUTHOR]

A unified viscoplastic constitutive model with wide temperature adaptability is developed based on the basic framework of the Chaboche type model to capture the intricate cyclic viscoplastic behaviors of Haynes 230 subjected to isothermal low-cycle fatigue and fatigue-creep loads. By introducing effective aging time into drag stress in the hyperbolic sine viscosity function, the critical value of back stress and the additional hardening model, a rate-dependent model based on the dimensionless concentration of solute atoms or precipitates is further improved to realize simulation of dynamic strain aging effects. A multistage evolutionary approach to determining asymptotic value of back stress influenced by strain range and cumulative plastic strain is proposed to respond to cyclic hardening or softening evolved differently with the variation of temperature. For the fatigue-creep interaction, a rate or time dependent directional hardening cumulative model combined with the existing mean stress model is established. After the multi-step material parameter determination method is given, the capabilities of the proposed model are fully validated to accurately depict the mechanical behaviors of Haynes 230 for five representative temperatures. • A systematically modified viscoplastic constitutive model with wide temperature adaptability has been developed. • A rate-dependent model to fully reflect the effect of dynamic strain aging is given. • The idea of the multistage asymptotic value evolution of back stress is proposed to respond to cyclic hardening and softening. • A rate-dependent directional hardening accumulation model is proposed for fatigue-creep interaction. • The capabilities of the proposed model are fully validated to accurately depict the mechanical behaviors of Haynes. [ABSTRACT FROM AUTHOR]

Abstract A cryogenic air separation unit (ASU) with the implementation of vapor recompression column (VRC) and LNG cryogenic energy is proposed and investigated. To this end, three types of cryogenic rectification column for air separation are first illustrated, and their thermodynamic characteristics are evaluated by the first and second thermodynamic laws. The results show the purity and recovery ratio of product are determined by the total amount of heat duty and the scheme of heat distribution. Compared with the conventional double rectification column and internally heat-integrated distillation column, the VRC is the most suitable column for the ASU with use of LNG cryogenic energy as its lower demand of shaft work and minimum energy of separation. Based on the above analysis, adopting the cryogenic energy from product to cool the reflux and feed air is beneficial for producing vapor product in the proposed process. The operating pressure of ASU could be reduced by about 24%, and the cryogenic energy of LNG can be used efficiently and sufficiently with respect to the supercritical thermophysical property. By adding the air-aid refrigeration process, the proposed process also has the ability to produce liquid oxygen. Under the same oxygen purity and recovery ratio, the optimal results show the power consumption is about 6.9% and 11.1% lower than that in the previous studies in producing vapor and liquid product respectively, and the minimum energy of separation is improved by use of LNG cryogenic energy. Highlights • The unified governing equations of air separation is deduced. • The vapor recompression column has the lowest shaft work and minimum energy of separation. • The cryogenic energy of LNG can be used efficiently and sufficiently. • Energy consumption of the proposed process is less than that of conventional processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel IES combined with hybrid electrical/thermal storage and ORC is proposed. • Off-design of gas turbine, ORC's combined heat and power, and harvesting heat flexibly are considered. • SOC of battery energy storage system and HSD / CSD of thermal energy storage system are compared. • ORC's CHP mode is beneficial to decrease investment of hybrid electric/thermal storage and increase its planning capacity. • Bi-level optimization method is beneficial for IES's optimal dispatch, planning and renewal. Integrated energy system (IES) is characterized as a heterogeneous system, providing energetic, economic and environmental benefits by cooperating with multiple energy carriers. However, current studies rarely focus on utilizing hybrid electric/thermal storage in coordination with harvesting heat flexibly in IES, which should be further considered in the planning period. To this end, a novel IES combined with hybrid electric/thermal storage and multi-output organic Rankine cycle (ORC) is proposed. Considering operating modes of gas turbine, ORC's working manners, and converting patterns of harvesting heat in IES, comparisons of case study and operating characteristics on typical season days are analyzed. A bi-level optimal planning model of hybrid electric/thermal storage with ORC is proposed, consisting of a lower-level operating model and an upper-level planning model. Results show that there is the least operating cost of IES on typical season days under the off-design mode of gas turbine, ORC's combined heat and power (CHP) mode and harvesting heat flexibly, when enabling multi-flows to adjust thermoelectric ratio effectively. ORC's pure power generating mode in IES with low electrical load is not economically attractive, while ORC's CHP mode is beneficial to enhance ORC's consistent dispatching time and electricity producing amount. State of charge of battery energy storage system has similar varying patterns, while heat storage degree and cold storage degree of thermal energy storage system change differently owing to varying thermal loads. The IES is thermodynamically feasible and economically attractive thanks to the bi-level optimization, achieving optimal battery energy storage system capacity of 1773 kWh, thermal energy storage system capacity of 4823 kWh and ORC capacity of 91.25 kW. [ABSTRACT FROM AUTHOR]

Due to strong nonlinear variation of supercritical liquid nature gas (LNG) and nitrogen (N 2 ) isobaric heat capacity with temperature and pressure, pinch point analysis is conducted for heat exchange process between LNG and N 2 and its effect on the air separation unit cooled by LNG cryogenic energy (CEASU) is studied in the present study. The effect of pinch point value, temperature difference at the cold end and pressure of N 2 on mass flow ratio (N 2 to LNG), approach temperature difference, energy consumption of CEASU and cryogenic energy utilization rate are analyzed in detail. For the heat exchanger process between LNG and N 2 , the different value of pinch point have little effect on its location, and increasing the temperature difference at the cold end effectively increases the mass flow ratio and decreases the approach temperature difference, while rising the pressure of N 2 leads to a valley value of the mass flow ratio, in contrast to a peak value in the approach temperature difference. For the energy consumption of CEASU, choosing the lower temperature difference at the cold end is good for the energy consumption and equivalent energy consumption per kilogram liquid production, but a large amount of LNG is needed and cryogenic energy could not be fully used; while the influence of pressure of N 2 on the energy consumption presents different variation trend. The result shows the energy consumption per kilogram liquid production of proposed CEASU is roughly 5–12% lower than that of convectional processes which the cryogenic energy is only used for cooling the nitrogen or the feed air. [ABSTRACT FROM AUTHOR]

Using natural fiber mats, aluminum sheets and epoxy resin, hybrid composites were fabricated through vacuum assisted resin transfer molding (VARTM) process. With novel sandwich structures, these hybrid composites contain natural fiber-based shells and ultra-thin aluminum sheet core. The hybrid composites offered excellent electromagnetic interference (EMI) shielding performance with good mechanical properties inherited from aluminum sheets and natural fiber-based composites, respectively. Furthermore, the shell material (natural fiber-based composites) provides protection of the aluminum sheets from exposing to atmosphere directly to prevent being corroded. In this study, the EMI shielding effectiveness, microstructure, flexure property, tensile property, and internal bonding strength of the hybrid composites were examined. The excellent EMI shielding performance and good mechanical properties enable the new hybrid composites to be used as engineering materials in the EMI protection fields. [ABSTRACT FROM AUTHOR]

Natural fiber reinforced composites with dual-functional properties, including electromagnetic shielding and paramagnetic functions, as well as improved water-resistant property, were fabricated using vacuum assisted resin transfer molding (VARTM) process. Magnetite particles were firstly mixed with kenaf fibers to form a mat, followed by resin intrusion and compression for the composite fabrication. The obtained kenaf fiber/magnetite/polyester composites were endowed with electromagnetic shielding and paramagnetic properties, without compromising the mechanical properties. When 35.2% magnetite was incorporated into the composites, the electromagnetic interference shielding effectiveness reached 79.2% with the range 8–12 GHz, and the saturation magnetization was 29.2 emu g −1 . The 24-h thickness swelling and water absorption of the composites after introducing magnetite were drastically reduced from 19.7% to 2.4% and 18.3% to 2.6%, counting as the decreases of 87.6% and 73.4%, respectively. It was indicated that the water resistance of the composite was improved significantly. [ABSTRACT FROM AUTHOR]

To fabricate kenaf fiber composites with electromagnetic interference (EMI) shielding function, the technique of vacuum-assisted resin transfer molding (VARTM) and Cu film magnetron sputtering were employed. The EMI shielding effectiveness (SE) and composite surface characteristics were examined with PNA Network Analyzer, Quanta 200 environmental scanning electron microscope and OCA20 contact angle meter. After being Cu-sputter coated for 0.5 h, 1 h, 2 h, and 3 h, the EMI SE values were increased to be 23.8 dB, 32.5 dB, 43.3 dB, and 48.3 dB, which denoted 99.5799%, 99.9437%, 99.9953%, or 99.9985% incident signal was blocked, respectively. The SEM observations revealed that the smoother surface of the composites was obtained by longer time sputtering, resulting in the SE improvement. The contact angle increased from 49.6° to 129.5° after 0.5 h sputtering, which indicated that the coated Cu film dramatically improved the hydrophobic property of composite. When the coating time increased to 3 h, the contact angle decreased to 51.0° because the composite surface roughness decreased with the increase in coating time. [ABSTRACT FROM AUTHOR]