A Dual-Window DC Bus Interacting Method for DC Microgrids Hierarchical Control Scheme

Hierarchical control schemes have been commonly employed in dc microgrid controls, which combine local control, dc bus voltage coordination, and communication links to guarantee smart operation of dc microgrids. Conventional dc bus voltage regulation cannot conduct signal exchange. Therefore, external communication links are usually needed for hierarchical control schemes. However, once the communication link fails, the hierarchical control system will lose its ability to coordinate the distributed power smartly. This paper proposed a dual-window dc bus interacting (DBI) method to exchange information between the distributed energy sources, for the situations where communication link fails or is not available. A small-scale dc microgrid experimental system was set up, and a simple master-slave control scheme was implemented without communication link to demonstrate the feasibility of the proposed DBI method for dc microgrid controls. The expandability and immunity of the proposed DBI method were also evaluated

Water Use in the Eagle Ford Shale: An Economic and Policy Analysis of Water Supply and Demand

The Eagle Ford Shale is a massive geologic formation located in South Texas spanning 30 Texas counties from Brazos County in the north east to Webb County in the southwest . With the advent of hydraulic fracturing (HF) and horizontal drilling, over 200 operators have been able to tap into previously inaccessible shale reserves to p roduce abundant amounts of oil and gas. The oil and gas proliferation in the Eagle Ford has seen exponential growth , and production is not anticipated to decline until 2025. In addition, a typical HF well in the Eagle Ford is estimated to consume about 13 acre - feet of water for a standard 5000 foot lateral . Approximately 90% of water for HF comes from fresh groundwater aquifers. This interaction of HF and water consumption is of primary importance from a poli tical and economic perspective. This s erves as t he focal point of our report. Using the tools of statistics, our research considered the groundwater consumption trends within the Eagle Ford counties using water consumption data of municipal, irrigation, mining (oil and gas) and other categories over a span of four years . This analysis showed that fresh groundwater is being consumed at about 2.5 times the groundwater recharge rates . Furthermore, irrigation is using more water than all other water - consuming categories combined. Thus, the water problem reaches well beyond the use of fresh grou ndwater for mining . With respect to likely requirements of water for HF, we posited this question: “ W ill technology bail us out?” Retrofitting learning curves to our data for water uses and the length of the well la teral , we find that after i nitial improvements in water us age, the technology appears to have stabilized. This, coupled with massi ve irrigation water consumption suggests that technology will not be a major source of water savings in the long run. Instead, we must look to better public policies . From a policy perspective, the status quo for groundwater u se is governed by the Rule of Capture and the oversight of groundwater conservation districts (GCDs) . T here exists a real conflict as large - scale water users are competing for a diminishing aquifer resource with no market signals of increasing scarcity. In addition, groundwater wells drilled in connection with oil and gas exploration are exempt from GCD per mitting requirements and receive a de facto “free pass” to water for HF. Likewise, limita tions imposed on irrigation users by the GCDs are rarely binding, so these users usually get a free pass as well. Our analysis leads us to three basic policy recommend ations . The first involves mandatory reporting of all groundwater uses by all classes of water use r s. Currently, government agencies and the public lack basic information on actual water consumption; t his policy seeks to relax that knowledge gap and bring transparency. Second , we propose incentivizing oil and gas companies to substitute brackish groundwater for fresh ground water. Our proposal calls for a severance tax reduction for tho se companies limiting fresh groundwater use for HF in the Eagle Ford. In addition to a temporary reduction in the severance tax, these companies c ould be recognized by the RRC and possibly the TCEQ for their environmental stewardship with a “ Green Star ” designation. Our t hird , most heterodox and long - term recommendation is to define ground water property rights on a per - acre ownership basis, which would attach to the surface owner’s real property. Under this system, the owner s of the water rights would be able to sell their water as they would any other resource, and the market would adjust the price of water to an economically efficient level. Most importantly, it would remove the incentive to use all you can today , leaving more water for the future at a lower future price.Commissioner Christi Craddick, Texas Railroad Commissio

Replication Data for Do Markets Make Good Commissioners?: A Quasi-Experimental Analysis of Retail Electric Restructuring in Ohio

Empirical support for the purported benefits of retail electric deregulation is mixed at best. Prior studies that identify states as simply “retail deregulated” overlook complex policy environments in which deregulation is implemented by regulators with a high degree of discretion. Prior studies also rely on Energy Information Administration (EIA) data that does not account for core regulatory interventions that can take place during the process of implementing deregulation. Using robust time series household final bill survey data from the Public Utilities Commission of Ohio (PUCO), this paper provides a quasi-experimental analysis of the price impacts of retail electric restructuring in Ohio. The results suggest that residential electricity prices have increased following retail restructuring in all service territories in Ohio, with significant favorable welfare effects observed only in the Cincinnati area, where key policy implementation stages were not circumvented

Visualizing the intellectual landscape and evolution of transportation system resilience: A bibliometric analysis in CiteSpace

As an emerging concept of a system's ability to resist disasters, transportation system resilience (TSR) has attracted the attention of scholars. In this study, a bibliometric analysis of 303 academic publications from the Web of Science related to TSR is presented to portray the intellectual landscape by visualizing the evolution of the collaboration network, the co-citation network, and keywords co-occurrence. The results showed that the number of publications in the field of TSR exploded after 2014 and attracted multi-disciplinary and cross-disciplinary attention from all over the world. Collaborative efforts among authors in this field tend to confine in small groups, and a large-scale collaborative network has yet to be established. This study also identifies the influential journals, institutions, scholars, and literature and summarizes the hot research topics and future research directions. In addition, it offers valuable references for researchers interested in TSR, and put forward recommendations on the emphasis and orientations of future studies

Microfluidic Generation of High-Viscosity Droplets by Surface-Controlled Breakup of Segment Flow

Fluids containing high concentration polymers, sols, nanoparticles, etc., usually have high viscosities, and high-viscosity fluids are difficult to be encapsulated into uniform droplets. Here we report a surface-controlled breakup method to generate droplets directly from various aqueous and nonaqueous fluids with viscosities of 1.0 to 11.9 Pa s and a dispersed-to-continuous viscosity ratio up to 1000, whereas the volume fraction of droplets up to 50% can be achieved. It provides a straightforward method to encapsulate high viscosity fluids, in a well-controlled manner in the rapid developing droplet-based applications, including materials synthesis, drug delivery, cell assay, bioengineering, etc

Groundwater use in the Eagle Ford Shale: some policy recommendations

Advances in hydraulic fracturing (fracking) and horizontal drilling have allowed oil and gas companies to tap into Texas’ previously inaccessible shale reserves. Fracking in the state has grown at an exponential rate and is not expected to decline until 2025. Fracking requires the consumption of vast amounts of groundwater, a resource that is already strained. This study quantifies the water consumption associated with fracking in the Eagle Ford Shale, evaluates the current regulatory framework, and proposes 3 policy recommendations. The data show that fracking has become the primary consumer of groundwater in the most active counties within the Eagle Ford. Our study proposes 3 policy solutions to ensure that groundwater is consumed in an economically efficient manner in these areas. These solutions are a more thorough system for reporting consumption, tax incentives for oil and gas companies to use substitutes for fresh groundwater, and an alternative property rights system to the current rule of capture system. Citation: Steadman M, Arnett B, Healy K, Jiang Z, David LeClere, Leslie McLaughlin, Roberts J. 2015. Groundwater use in the Eagle Ford Shale: some policy recommendations. Texas Water Journal. 6(1):67-78. Available from: https://doi.org/10.21423/twj.v6i1.7023

Integral Effects of Porosity, Permeability, and Wettability on Oil–Water Displacement in Low-Permeability Sandstone Reservoirs—Insights from X-ray CT-Monitored Core Flooding Experiments

Porosity, permeability, and wettability are crucial factors that affect the oil–water displacement process in reservoirs. Under subsurface conditions, the integral effects of these factors are extremely difficult to document. In this paper, waterflooding experiments were carried out using a core flooding system monitored with X-ray dual-energy CT. The mesoscale, three-dimensional characteristics of water displacing oil were obtained in real time. The integral effects of porosity, permeability, and wettability on the waterflooding in the low-permeability sandstone reservoirs were investigated. It was found that if the reservoir rock is water-wet, then the residual oil saturation decreases gradually with increasing porosity and permeability, showing an increasing waterflooding efficiency. On the contrary, if the reservoir rock is oil-wet, the residual oil saturation gradually increases with improving porosity and permeability, showing a decreasing waterflooding efficiency. The porosity, permeability, and wettability characteristics of reservoirs should be comprehensively evaluated before adopting technical countermeasures of waterflooding or wettability modification during oilfield development. If the porosity and permeability of the reservoir are high, water-wet reservoirs can be directly developed with waterflooding. However, it is better to make wettability modifications first before the waterflooding for oil-wet reservoirs. If the porosity and permeability of the reservoir are poor, direct waterflooding development has a better effect on oil-wet reservoirs compared with the water-wet reservoirs

Cubic AgMnSbTe₃ semiconductor with a high thermoelectric performance

The reaction of MnTe with AgSbTe2 in an equimolar ratio (ATMS) provides a new semiconductor, AgMnSbTe3. AgMnSbTe3 crys-tallizes in an average rock-salt NaCl structure with Ag, Mn, and Sb cations statistically occupying the Na sites. AgMnSbTe3 is a p-type semiconductor with a narrow band gap of ~0.33 eV. A pair distribution function analysis indicates that local distortions are associated with the location of the Ag atoms in the lattice. Density functional theory calculations suggest a specific electronic band structure with multi-peak valence band maxima prone to energy convergence. In addition, Ag2Te nanograins precipitate at grain boundaries of AgMnSbTe3. The energy offset of the valance band edge between AgMnSbTe3 and Ag2Te is ~0.05 eV, which implies that Ag2Te precipitates exhibit a negligible effect on the hole transmission. As a result, ATMS exhibits a high power factor of ~12.2 μWcm-1K-2 at 823 K, ultralow lattice thermal conductivity of ~0.34 Wm-1K-1 (823 K), high peak ZT of ~1.46 at 823 K, and high av-erage ZT of ~0.87 in the temperature range of 400–823 KAgency for Science, Technology and Research (A*STAR)Ministry of Education (MOE)Submitted/Accepted versionThis study was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under grant DESC0014520, DOE Office of Science. The User Facilities are supported by the Office of Science of the U.S. Department of Energy under Contract Nos. DE-AC02-06CH11357 and DEAC02-05CH11231. We acknowledge the access to facilities for high-performance computations at Northwestern University, Singapore MOE AcRF Tier 2 under Grant No. 2018-T2-1-010, Singapore A*STAR Pharos Program SERC 1527200022, Singapore A*STAR project A19D9a0096, support from FACTs of Nanyang Technological University for the sample analysis, National Natural Science Foundation of China (Grant Nos. 52002137, 51802070, 51572098, and 51632006), National Basic Research Program of China (Grant No. 2013CB632500), the Fundamental Research Funds for the Central Universities under Grant Nos. 2021XXJS008 and 2018KFYXKJC002, Natural Science Foundation of Hubei Province (Grant No. 2015CFB432), Open Fund of State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology (No. 2016- KF-5), and Graduates’ Innovation Fund, Huazhong University of Science and Technology (No. 2019ygscxcy032)