Analysis of the Peak Load Leveling Mode of a Hybrid Power System with Flywheel Energy Storage in Oil Drilling Rig

The load frequently oscillates in large amplitude like pulses when the draw-works lift or lower in the oil well drilling rig, and that makes the diesel engine run uneconomically. A new solution for the pulse load problem is to add a motor/generator set and a flywheel energy storage (FES) unit to the diesel engine mechanical drive system to form a hybrid power system with energy storage. The storage capacity of the power and energy, and the charging-discharging operation modes are discussed for the first time. The engine power output in frequent fluctuation was measured in the oil well drilling engineering practice. The configuration and the theoretical model of the hybrid power system with energy storage and peak load leveling were established. Furthermore, 1% to 12% saving of fuel is possible for the case of single engine in the load leveling running mode compared to bi-engines in a traditional running mode for the peak load between 900 to 1200 kW and the valley load between 200 to 600 kW. The experimental verification of the load leveling with FES confirmed that the diesel engine worked more smoothly with less smoke emission. In addition, 5% to 10% more fuel was consumed in the load leveling test compared to the traditional running mode with the drive-by 800 kW diesel engine. However, 21% fuel saving was obtained in the load leveling test with the drive-by 400 kW diesel generator

Bis-Silicon-Bridged Stilbene: A Core for Small-Molecule Electron Acceptor for High-Performance Organic Solar Cells

Bis-Silicon-Bridged Stilbene: A Core for Small-Molecule Electron Acceptor for High-Performance Organic Solar Cell

Van der Waals Heterostructure Based Field Effect Transistor Application

Van der Waals heterostructure is formed by two-dimensional materials, which applications have become hot topics and received intensive exploration for fabricating without lattice mismatch. With the sustained decrease in dimensions of field effect transistors, van der Waals heterostructure plays an important role in improving the performance of devices because of its prominent electronic and optoelectronic behavior. In this review, we discuss the process of assembling van der Waals heterostructures and thoroughly illustrate the applications based on van der Waals heterostructures. We also present recent innovation in field effect transistors and van der Waals stacks, and offer an outlook of the development in improving the performance of devices based on van der Waals heterostructures

Multioperation Mode Ferroelectric Channel Devices for Memory and Computation

The traditional von Neumann architecture separates memory from the central processing unit (CPU), resulting in aggravated data transfer bottlenecks between the CPU and memory during a data volume surge. Emerging technologies, such as in‐memory computing (IMC), provide a new way to overcome the limitations due to the separation of memory and computation. However, existing IMC efforts are generally limited to a single (gate‐control or drain‐control) mode of operation to achieve functionality. Herein, a 2D ferroelectric channel device that enables the feasibility of multioperation modes is proposed. In addition, rich functionalities, such as logic, nonvolatile memory, and neuromimetic plasticity modulation, by switching the operating modes are realized. A device that facilitates multimodal operations and a promising technical solution for further development of burgeoning computing architecture is provided

Electric Field Facilitating Hole Transfer in Non-Fullerene Organic Solar Cells with a Negative HOMO Offset

The record high photoinduced current and power conversion efficiencies of organic solar cells (OSCs) should be attributed to the significant contribution of non-fullerene electron acceptors via hole transfer to electron donors and/or a pronounced decrease in energy losses for exciton dissociation by aligned highest occupied molecular orbitals (HOMOs) or lowest unoccupied molecular orbitals (LUMOs). However, the hole transfer mechanism in those highly efficient non-fullerene OSCs with small HOMO offsets has not been extensively studied and fully understood, yet. Herein, we comparatively study the hole transfer kinetics in two OSCs with a positive (0.05 eV) and a negative (-0.07 eV) HOMO offset (Delta HOMO) based on polymer donor PTQ10 paired with non-fullerene acceptors ZITI-C or ZITI-N. Short-circuit current densities (J(sc)) of 20.42 and 12.81 mA cm(-2) are achieved in the OSCs based on PTQ10:ZITI-C (Delta HOMO = 0.05 eV) and PTQ10:ZITI-N (Delta HOMO = -0.07 eV) with an optimized donor (D):acceptor (A) ratio of 1:1, respectively, despite the small and even negative Delta HOMO. Results from time-resolved transient absorption spectroscopy show slower hole transfer (14.3 ps) in PTQ10:ZITI-N than that (3.7 ps) in PTQ10:ZITI-C. To understand the decent J(sc) value in the OSCs of PTQ10:ZITI-N, the temperature and electric field dependences of hole transfer are investigated in low-donor-content OSCs (D:A ratio of 1:9) in which photocurrent is dominated by the contribution via hole transfer from ZITI-N to PTQ10. Devices based on PTQ10:ZITI-C and PTQ10:ZITI-N show similar free charge generation behavior as a function of temperature, whereas the external quantum efficiencies of the PTQ10:ZITI-N device exhibit a much stronger bias dependence than that of PTQ10:ZITI-C, which suggests that the electric field facilitates exciton dissociation in PTQ10:ZITI-N where the energetic driving force alone cannot efficiently dissociate excitons.Funding Agencies|Swedish Government Strategic Research Area in Material Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU ) [200900971]; Swedish Research CouncilSwedish Research Council [2017-04123]; Knut and Alice Wallenberg FoundationKnut &amp; Alice Wallenberg Foundation [2016.0059]; China Scholarship Council (CSC)China Scholarship Council; National Key R&amp;D Program of China [2019YFA0705900, 2017YFA0204701]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [21572234, 21661132006, 91833304]</p

Permeability enhancement theory and a complete set of technology for low permeability coal seam by liquid CO2 fracturing

Liquid CO2 fracturing in low-permeability coal seams has dual gas-enhanced drainage effects of fracture reconstruction and displacement. It is a permeability enhancement technology that is easy to be used in combination with other technologies and has the potential for large-scale application. This paper proposes a theoretical system and a complete set of technical framework for fracturing and permeability enhancement of low-permeability coal seam with liquid CO2; according to the principle of stress superposition and the maximum tensile stress criterion, a model for determining the initiation pressure of liquid CO2 fracturing was established considering the change of phase state and low viscosity and strong permeability of liquid CO2 during the injection process; taking type I fracture criterion as the discriminant condition of fracture propagation, the quantitative characterizing relationship between fracturing orifice pressure and fracture propagation distance under constant fluid injection flow was established, and the influence law of fluid injection pressure, fracturing fluid viscosity and fracture occurrence on fracture propagation was clarified. On this basis, the four key parameters and their calculation methods to determine the performance of the complete set of equipment for liquid CO2 fracturing and permeability improvement in coal seam were proposed, the first complete set of equipment for underground fracturing and permeability improvement in China was developed, and the construction technology of fracturing and permeability improvement was developed, which was applied in Huainan Mining Area and Binchang Mining Area respectively

Multi-Model Comparison in the Attribution of Runoff Variation across a Humid Region of Southern China

The natural hydrological cycle of basins has been significantly altered by climate change and human activities, leading to considerable uncertainties in attributing runoff. In this study, the impact of climate change and human activities on runoff of the Ganjiang River Basin was analyzed, and a variety of models with different spatio-temporal scales and complexities were used to evaluate the influence of model choice on runoff attribution and to reduce the uncertainties. The results show the following: (1) The potential evapotranspiration in the Ganjiang River Basin showed a significant downward trend, precipitation showed a significant upward trend, runoff showed a nonsignificant upward trend, and an abrupt change was detected in 1968; (2) The three hydrological models used with different temporal scales and complexity, GR1A, ABCD, DTVGM, can simulate the natural distribution of water resources in the Ganjiang River Basin; and (3) The impact of climate change on runoff change ranges from 60.07% to 82.88%, while human activities account for approximately 17.12% to 39.93%. The results show that climate change is the main driving factor leading to runoff variation in the Ganjiang River Basin

Low-Bandgap Small-Molecule Donor Material Containing Thieno[3,4‑<i>b</i>]thiophene Moiety for High-Performance Solar Cells

By replacing the central thiophene of <b>STDR</b>, a sepithiophene terminated with two 3-ethylrhodanine moieties, with 2-ethylhexyl 3-fluorothieno­[3,4-<i>b</i>]­thiophene-2-carboxylate, an A–D–Q–D–A-type small molecule has been developed for high-performance organic solar cells with improved photocurrent. <b>STDR</b>-<b>T</b><i><b>b</b></i><b>T</b> exhibits a significant bathochromic shift with a low optical bandgap of approximately 1.60 eV in the thin film. Accordingly, <b>STDR</b>-<b>T</b><i><b>b</b></i><b>T</b> shows broad external quantum efficiency spectral response up to 800 nm. A high short circuit current (<i>J</i>_sc) of 10.90 mA cm^–2 was achieved for <b>STDR</b>-<b>T</b><i><b>b</b></i><b>T</b>:PC₇₁BM-based devices; this is significantly higher than that of <b>STDR</b>:PC₇₁BM-based devices, <i>J</i>_sc: 5.61 mA cm^–2, with a power-conversion efficiency (PCE) of 5.05%. Compared with <b>STDR</b>-based devices, <b>STDR</b>-<b>T</b><i><b>b</b></i><b>T</b>-based devices show balanced charge carrier transport, better thin-film morphology, and favorable charge separation/collection