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The goal of this paper is to develop models for estimating the potential profit of a battery storage system that provides multiple services in a competitive electricity market. We assume the size of the battery is small relative to the energy market volume and its actions do not impact the energy market outcomes; thus, it is a price-taker in the energy market. However, considering the relatively smaller market volume for ancillary services, we consider the battery’s strategies to impact the outcomes of the markets for frequency regulation service, spinning reserve, and non-spinning reserve. An optimization model is proposed considering the uncertainties in energy prices, the offers of ancillary services by competitors, and the energy deployment in ancillary services markets. We employ robust and stochastic optimization approaches to account for the different nature of each uncertain variable. The scheduling is done in day-ahead and is later refined closer to real time. Numerical results are provided based on real-life data.

Abstract This paper presents a new upscaling method to derive the core-scale apparent gas permeability from an improved pore-scale permeability model and experimental data, with more rigorous incorporation of varying gas storage/transport mechanisms in nano/micro pores. First, in use of SEM images of a gas-rich shale field example in Sichuan Basin from our lab, pore network models of inorganic-matter (IOM) and organic-matter (OM) are characterized by using a digital-core technique. Next, an improved pore-scale real gas apparent permeability is modeled rigorously for both IOM/OM, respectively, with 1) bulk gas transport, gas adsorption, surface diffusion, pore-size confined phase behavior, and stress-dependent rock properties and 2) an additional reduction in inorganic pore sizes by water film adhered on pore surfaces. Core-scale permeability is then derived by assembling the permeabilities of stochastically distributed IOM/OM patches with different pore network models properties using the Monte Carlo sampling method. The new core-scale permeability model is validated by pulse-decay permeability experiment. Moreover, the representative elementary volume (REV) size is determined by analyzing the relative standard deviation of apparent gas permeability in cases with different sample sizes. The contributions of different gas transport mechanisms are discussed, and the impacts of stress-dependence for several field examples (i.e., Sichuan, Pierre and Barnett Basins) and water film with varying relative humidity (RH) on core-scale apparent permeability are analyzed. This work provides an effective approach to determine the core-scale shale permeability by directly using pore-scale experimental data, which is a common challenge in the unconventional resources.

Abstract In this article, the novel concept of using magnetic nanofluidic electrolyte for redox flow batteries is demonstrated for the first time. In this regard, the stable magnetic nanofluidic electrolytes are prepared by dispersing magnetic modified multiwalled carbon nanotubes (MMWCNTs) in the positive electrolyte of a polysulfide-iodide redox flow battery at mass concentrations of less than 0.3 g L−1. The electrochemical behavior of magnetic nanofluidic electrolyte was examined using cyclic voltammetry at different mass concentrations of MMWCNTs with a carbon felt electrode. Higher and stable peak current densities were observed at larger mass concentrations of MMWCNTs. A polysulfide-iodide redox flow battery was employed to evaluate the influence of magnetic nanofluidic electrolyte on the battery performance for various mass concentrations, velocities of flowing electrolyte, and current densities using electrochemical impedance spectroscopy, polarization, and galvanostatic charge-discharge experiments. A decrease in ohmic resistance as well as reductions in the charge-transfer and mass-transfer resistances were observed for the magnetic nanofluidic electrolyte compared to those obtained in the absence of MMWCNTs. Adding MMWCNTs to the positive electrolyte at the mass concentration of 0.3 g L−1 results in enhanced performance of the polysulfide-iodide redox flow battery, whereby the peak power density increases by 45% and an energy efficiency of 79.91% was obtained at a current density of 20 mA cm−2. Moreover, high coulombic efficiency close to 100% and stable cycling performance over 200 cycles were achieved using magnetic nanofluidic electrolyte. After 50 cycles, at a current density of 30 mA cm−2, the energy efficiency of the battery operated with magnetic nanofluidic electrolyte remains 10% greater than that obtained in the absence of MMWCNTs. Besides improving the battery performance, MMWCNTs can be separated and recovered using magnetic decantation during electrolyte replacement for redox flow batteries involving high capacity fade and precipitation, which preserves system cost-benefits. The magnetic nanofluidic electrolyte could be applied for different redox solutions using appropriate magnetic nanoscale conductors. This innovative concept opens up a new opportunity to develop the next generation of high-performance and low-cost flow batteries.

Abstract The dissolution of carbon dioxide (CO 2 ) in deep saline aquifer water is recognized as one of the fundamental mechanisms in the subsurface for storing significant quantities of CO 2 . One fundamental physical effect of CO 2 dissolution is the slight increase in water density in the layer in contact with the buoyant free-phase CO 2 plume. Under specific conditions, this may lead to gravitational instability and the onset of free convection, significantly accelerating the dissolution of the free-phase CO 2 by bringing CO 2 in contact with a larger volume of aquifer water. It is also feasible to enhance CO 2 dissolution using engineering methodologies such as injecting water on top of the plume of CO 2 . The objective of this review is to provide a perspective on the progress in modeling and experimental observations of physical aspects of CO 2 dissolution in deep saline aquifers. We review the published research efforts concerning the physical effects of CO 2 dissolution in formation water, the conditions under which process can be accelerated either naturally, such as by free convection, or by use of engineering methodologies, and the effects of CO 2 dissolution on CO 2 storage. Finally, we discuss areas in need of further research.

Accurate and fast estimation of power system phasors is the key to reliable operation of power system and its control/protective equipment. There have been many studies on phasor estimation techniques under dynamic and transient conditions. Although the performance under dynamic conditions of estimators based on the static phasor model has improved, significant errors still exist during large dynamic deviations. Two fast and precise dynamic phasor estimation algorithms under power system oscillations and off-nominal frequency conditions are described in this paper. The methods use the signal model under these dynamic conditions, linearize them by using Taylor’s series expansion, and estimate the phasor using least squares technique. Frequency and its rate of change are also calculated using adjacent phasors with minimum complexity. Results obtained show that the performance errors of the proposed methods are way below the minimum requirement of the standard and better than other similar dynamic phasor algorithms.

Abstract This study presents the comparison of the life cycle performance of two different urban energy systems, applied to a large mixed-use community, in Calgary (Canada). The two systems investigated consist of an energy efficient conventional system, using heat pumps for heating, cooling and domestic hot water; the second design widely deploys solar thermal panels coupled to district heating infrastructure and a borehole seasonal thermal storage. The analysis is based on the Life Cycle Assessment methodology and includes the stages of raw materials and energy supply, system manufacturing, use stage of the systems, generation and use of energy on-site, maintenance and components’ substitution, and explores the performances of the systems on a life cycle perspective thanks to the use of different indicators of ILCD 2011 Midpoint impact assessment method. The solar-based system, performs better than the conventional system from the point of view of all indicators used in the study. In detail, ozone depletion and land use can be reduced of about 79.7% and 27% respectively, while the remaining impact categories show a reduction of about 39–56%. These results can be extended to other similar systems operating under similar weather constraints, energy systems included in the operation, thermal loads requirements. Moreover, the study is based on the premises and assumptions of real documented case studies in Canada, thus further reinforcing the solidity of the results.

AbstractOver the last few decades, research on the abatement of carbon dioxide (CO2) gas has gained momentum, due to its increasing atmospheric levels. This study investigated high‐temperature steam‐only gasification of woody biomass for the production of high‐purity hydrogen integrated with CO2 capture in a moving‐bed gasifier. Extensive process modelling and simulation were performed using the superior solid handling features of the Aspen Plus process simulator software. After validating the model with experimental data from a demonstration plant available in the open literature, a reversible carbonation‐calcination reaction of calcium oxide (CaO) with CO2 was added to the system. Sensitivity analyses were conducted to verify the predictive accuracy of the model. The effects of steam‐to‐carbon (S/C) ratio on the resulting gas composition were thoroughly studied to delineate the complex process of gasification. Beyond the mitigation of CO2 emissions, the introduction of a CaO‐based sorbent in the process simulation significantly enhanced hydrogen production by simultaneously promoting the forward water‐gas shift reaction and reducing tars through increased tar‐cracking reactions. The results show that hydrogen of a higher purity was produced with the inclusion of dry‐sorption CO2 capture in the gasification process. Moreover, the addition of the sorbent increased the higher heating values (HHV) by 3 times and improved the cold gas efficiency by 34 %.

Bradshaw et al. (2021) make a call to action in light of three major crises—biodiversity loss, the sixth mass extinction, and climate disruption. We have no contention with Bradshaw et al.’s diagnosis of the severity of the crises. Yet, their call for scientists to “tell it like it is,” their appeal to political “leaders,” and the great attention they afford to human population growth as a main driver underpinning the three crises, rest on contested assumptions about the role of science in societal transformations, and are scientifically flawed and politically problematic. In this commentary, we challenge Bradshaw et al.’s assumptions concerning the nature of science, polity, and humanity as well as the implicit politics underlying their analysis and messaging. We end with an alternative call to action.

Aerobic granules, a relative novel form of microbial aggregate, are capable of degrading many toxic organic pollutants. Appropriate strategy is needed to acclimate seed sludge to the toxic compounds for successful granulation. In this study, two distinct strategies, i.e. mixed or single carbon sources, were experimented to obtain phenol-acclimated sludge. Their effects on reactor performance, biomass characteristics, microbial population and the granulation process were analyzed. Sludge fed with phenol alone exhibited faster acclimation and earlier appearance of granules, but possibly lower microbial diversity and reactor stability. Using a mixture of acetate and phenol in the acclimation stage, on the other hand, led to a reactor with slower phenol degradation and granulation, but eventual formation of strong and stable aerobic granules. In addition, the content of intracellular polyhydoxyakanoates (PHA) was also monitored, and significant accumulation was observed during the pre-granulation stage, where PHA >50% of dry weight was observed in both reactors.