A thermally immature specimen extracted from the Bakken Formation was exposed to both anhydrous and hydrous pyrolysis (AHP/HP) experiments spanning a temperature range of 300 to 450 °C. The objective ...was to investigate the potential discrepancies in geochemical properties, organic petrology, and chemical composition of the byproducts. The presence of unresolved complex mixtures (UCM) in gas chromatography (GC) resulted in fluctuations in the concentration of normal-alkanes as the temperature increased. Furthermore, it was observed that the ratios of Pr/Ph, Pr/nC17, and Ph/nC18 exhibited a significant reduction with temperature advancement during both the HP and AHP settings. This decline can be attributed to the enhanced maturation process. Significant reductions in C29Ts were observed in response to temperature, but a modest rise was observed in the GI. The ratio of Ts to Tm exhibited an increase during HP and a reduction during AHP conditions. The increase in temperature under both HP and AHP conditions resulted in an increase in the ratios of C23 tricyclic/C24 tetracyclic terpanes (C23 tt/C24 Tt), C24 tetracyclic terpane and C30 hopane, and C30 rearranged hopane/C30 hopane (C30RH/C30H). The C29/C30 hopanes (C29 H/C30H) ratio exhibited a marginal increase from 10.11 to 10.5 when subjected to HP, and had a rising pattern when subjected to AHP. Based on petrographic investigations, it was observed that the physical alteration of telalginite was more pronounced when water was present in the system and temperature was increased. Furthermore, it was observed that the fluorescence of telalginite ceased to be detectable when exposed to temperatures exceeding 325 °C. The reflectance values of bitumen exhibited an increase when the temperature rose, regardless of whether it was under AHP or HP settings. However, the changes seen were more significant under HP conditions than under AHP conditions. The observation of a granular mosaic texture formed by pyrobitumen under HP conditions at a temperature of 450 °C indicates that it possesses graphitizing characteristics. The divergent outcomes of pyrolysis pathways in the presence and absence of water highlight the substantial effect exerted by water in the production and release of petroleum and its derivatives with particular emphasis on the potential contribution of exogenous hydrogen in this context.
This paper discusses the technical, regulatory and policy challenges inherent in planning and operating power systems with high penetrations of Distributed Energy Resources (DER): generators, ...flexible demand and energy storage connected within electricity distribution networks. Many liberalised electricity systems worldwide are seeing growth in DER including significant capacities of distributed renewable generation. The paper starts from the premise that optimal distribution networks are those that satisfy the objective of a lowest cost power system whilst meeting customers’ expectations of reliability and societal desire for sustainability. It highlights major challenges that policy makers face in respect of market and regulatory arrangements that support energy and flexibility provision from a large number of small, variable and often uncertain resources. These challenges include the need to respect the technical limits of the system and ensure its operability, development of well-designed mechanisms to support innovation, and an appropriate share of risk between market actors. A key contribution of the paper is to discuss the opportunities offered by more active distribution system operation as a substitute for capital investment and its regulatory and policy implications. Finally, the paper presents priorities for policy to facilitate a highly distributed electricity system.
•Impact of increased Distributed Energy Resources into power system on policy needs.•Development should focus on low costs within appropriate sustainability and security constraints.•Key issues include sharing of risk and information, locationality and timing of pricing.•Reviews existing and developing arrangements across regulated and non-regulated sectors.•Concludes with 6 key principles for system design and policy implications.
The increase of environmental concerns, scarcity of fossil fuel resources, uncontrolled growth of demand, along with the development of efficient multi-generation systems have made the restructuring ...of current energy systems inevitable. Future energy systems will be in the form of sustainable multi-energy systems. The optimal operation of such systems requires an integrated energy management system for optimal planning, control and management. Energy hub is a new and promising concept for optimal management of systems with multiple energy carriers. Energy hub has a large potential for realization of energy system models and moving towards sustainable multi-energy systems. This paper provides a comprehensive overview of the concepts and different applications of energy hubs in various energy consumption sectors including residential, commercial, industrial, agricultural, and the integration of these systems. The potential role of energy hub as an integrated energy management system to solve the main challenges in these consumption sectors is evaluated. This study focuses on the benefits earned by integration of the options such as demand side management, distributed energy resources, renewable energy resources, multi-generation systems, storage systems as well as using the smart technologies by introducing the concept of smart energy hubs.
•This paper presents a holistic review of the concept and applications of energy hub.•Residential, commercial, industrial and agricultural micro hubs have been evaluated.•The concept and advantages of smart energy hubs have been discussed in this paper.•Energy hub is a promising option for integrated and smart management.•Smart and sustainable energy systems can be achieved in the form smart energy hubs.
The kinetic and thermodynamic characteristics of supercritical methane adsorption are beneficial to understanding the methane adsorption mechanism in gas reservoirs, which is poorly documented. In ...this work, nitrogen (N2) physical adsorption and methane isothermal adsorption are used to analyze the pore structure and methane adsorption characteristics of the Wufeng and Longmaxi shales. The energy alterations of methane adsorption process for gas shale were analyzed from the aspects of adsorption thermodynamics and kinetics. Results have shown that high temperature reduces the adsorption capacity of methane molecules on the pore surface, but high pressure increases the interaction force between methane molecules and the solid surface, thereby promoting adsorption on shale. Regardless of the temperature effect, the adsorption potential decreases and becomes stable as pressure increases, and adsorption decay rate curves generally show an S-shape. In the early period of methane adsorption, methane molecules occupy high-energy sites, and surface free energy begins to decrease and then stabilize, indicating a decrease in adsorption potential. As pressure increasing, the actual adsorption heat shows a decreasing trend on shale. In the low-pressure stage (<10 MPa), isosteric adsorption heat is relatively close under different temperatures. In the high-pressure stage (>10 MPa), adsorption heat will cross with increasing pressure, showing that higher temperatures can change methane molecules’ sensitivity on the substrate surface. As the burial depth of shale increases, adsorption ability increases first and then decreases. When the burial depth of shale is smaller than approximately 1000 m the pressure has a positive effect on the adsorption capacity. When the depth of shale is between 1000 and 3500 m, the pressure and temperature have comparable effects on the adsorption of shale. In contrast, when the depth is greater than 3500 m, the negative effect of temperature exceeds the influence of pressure on adsorption ability, which is not conducive to the adsorption of shale gas.
Carbon-based nanoparticles possess ultrasmall size (<10 nm) and show great application potential in reducing the injection pressure of unconventional reservoirs. However, the strong hydrophilicity of ...carbon nanoparticles limits the oil–water interfacial activity, which hinders the further improvement of oil recovery. In this study, active carbon dots (S-CDs) are synthesized through two-step hydrothermal reactions by first preparing carbon dot (CD) carriers from citric acid and ethylenediamine and then grafting cocamidopropyl-N,N-dimethylglycine and characterizing them by high-resolution transmission electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The stability experiment verifies that the abundant hydrophilic groups on the surface substantially enhance the electrostatic repulsion between S-CDs, and the absence of carboxyl groups avoids the reaction with other groups, which endows S-CDs with intrinsic aqueous dispersibility and resistance to high temperature (130 °C) and high salinity (16 × 104 mg/L). In addition, S-CDs with an average hydration particle size of 2.84 nm exhibit excellent oil–water and oil–solid interfacial activity by controlling the interfacial tension, interfacial viscoelastic modulus, wettability alteration, and adsorption capacity. Core flooding tests show that 0.05 wt % S-CD nanofluids can reduce the injection pressure by 32.92% and increase the oil recovery rate by 19.15% compared to simulated formation water.
Kerogen evolution in organic-rich sedimentary rocks, by its time scale and complexity, is a particularly challenging process for atomistic modeling and simulations. Yet, such modeling approaches, ...provided that appropriate simulation techniques are used and reasonable simplifications are made, can unravel the most significant physicochemical mechanisms underlying oil and gas generation and the evolution of the kerogen structure and properties. Here, we combine reactive molecular dynamics and the replica-exchange molecular dynamics simulation technique to simulate a simple model of type I organic matter, described as a mixture of five unsaturated fatty acids as a simplified model of algae, along its maturation pathway, from diagenesis to late metagenesis. We describe fluid production, from the oil to gas windows, and kerogen evolution in terms of the structure and properties. We show that the formation of permanent microporosity within the kerogen matrix is intimately correlated to both the fluid production and the rigidification of the kerogen skeleton occurring in the gas window, i. e., at low O/C and H/C atomic ratios. We show that because of their pristine molecular structures with a more or less long tail made of alternating single and double carbon–carbon bonds, fatty acid molecules do decompose into alkanes of various lengths, up to octane in our simulations, by contrast to lignin and cellulose that only produces short alkanes, mostly methane.
•This paper addresses combined heat and power system and energy network expansion planning.•The proposed model considers different scenarios of energy consumption.•The introduced method uses a ...three-level iterative heuristic optimization algorithm.•The proposed method is applied to 9-bus, 33-bus and 123-bus test systems.
This paper addresses a hierarchical framework for the energy resources and network expansion planning of an Energy Distribution Company (EDC) that supplies its downward Active Industrial MicroGrids (AIMGs) with hot water and/or steam and electricity through its district heating and electric grid, respectively. The main contribution of this paper is that the proposed model considers AIMGs’ electricity transactions with each other and/or other customers through the EDC’s electric main grid and investigates the impacts of these transactions on the expansion planning problem. The solution methodology is another contribution of this paper that tries to trade-off between accuracy and computational burden. The proposed framework uses a three-stage iterative heuristic optimization algorithm that considers different uncertainties of the planning and operational parameters. At the first stage, the algorithm determines the characteristics of energy system facilities for different stochastic parameter scenarios. At the second stage, the feasibility and optimality of AIMGs’ electric transactions are evaluated and the optimal scheduling energy resources in normal states are determined. Finally, at the third stage, different demand response alternatives, load shedding and the AIMGs’ electric transaction interruptions for contingent conditions are decided. The proposed method is applied to 9-bus, 33-bus and 123-bus IEEE test systems. Further, a full search algorithm is used to evaluate the quality of solutions of the proposed algorithm. The introduced algorithm reduced the total costs for the 9-bus, 33-bus and 123-bus system about 18.645%, 9.658%, and 4.849% with respect to the costs of custom expansion planning exercises, respectively.
Can cannabis go green? Madhusoodanan, Jyoti
Nature (London),
08/2019, Letnik:
572, Številka:
7771
Journal Article
Recenzirano
Odprti dostop
With its demand for water, land and artificial lighting, cannabis growing can leave a large environmental footprint. But heightened awareness could make cultivation more benign.
We conducted a series of molecular dynamics (MD) simulations to investigate the molecular structure, dynamics, and nuclear magnetic resonance (NMR) relaxation of multicomponent shale condensate ...confined within kerogen nanopores. Detailed analysis of the mean-squared displacements (MSD), diffusion coefficients (D A), and NMR relaxations times was carried out on each component of the shale condensate as a function of pore size, pressure, and Larmor frequency. Simulations show that kerogen–fluid interactions strongly affect the dynamic behavior of shale condensate when the size of the pore is reduced from 29 to 3 nm. Additionally, the results indicate that pressure plays an important role in the diffusion and relaxation of each condensate component inside kerogen nanopores. MSD analysis shows that the mobility of each molecular compound decreases as the molecular weight increases. MD results also indicate that the branched-chain hydrocarbons (isobutane and isopentane) exhibit higher diffusivity compared to n-butane and n-pentane species. Furthermore, diffusion coefficients, obtained via Einstein’s relation, decrease as the pore size decreases and pressure increases. NMR relaxation times of each compound of shale condensate are affected by confinement and pressure. To quantify the contribution of Larmor’s frequency to the NMR relaxation properties, we computed the longitudinal relaxation time (T 1) for three different Larmor frequencies (2.3, 22, and 400 MHz). At higher frequencies, lighter shale condensate components exhibit longer longitudinal relaxation times compared to the heavier components. These results contribute to a deeper understanding of the dynamic and NMR behavior of shale condensate confined in kerogen nanopores.
Gas transport within the coal matrix is key to realizing mass exchange between the fracture and matrix systems. However, considerable controversy remains regarding gas transport within the coal ...matrix system. In this study, the applicability of several typical models was evaluated based on the proposed criteria, mainly through gas emission under pressure experiments, and it is found that the Darcy seepage model describes gas transport behavior within the coal matrix more scientifically. Subsequently, the validity of the seepage model was re-evaluated through pore structure analysis, and the gas transport patterns and underlying mechanisms of the dual-porosity and dual-permeability models were discussed. The results suggest that gas transport within the matrix is dominated by the Fick diffusion flow only when methane molecules within the coal matrix are located in the micropore filling section. When the pore size is located in the outer pore section, gas within the matrix will be transported outward in a free state driven by pressure. In addition, the proposed gas transport model and field data were used to validate the analysis. It is concluded that in view of the low efficiency of gas transport in the micropore filling section, the dual-porosity and double-permeability models can be used to simplify gas transport in coal seams.
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