Probabilistic cost prediction for submarine power cable projects

It is estimated that Europe alone will need to add over 250,000 km of transmission capacity by 2050, if it is to meet renewable energy production goals while maintaining security of supply. Estimating the cost of new transmission infrastructure is difficult, but it is crucial to predict these costs as accurately as possible, given their importance to the energy transition. Transmission capacity expansion plans are often founded on optimistic projections of expansion costs. We present probabilistic predictive models of the cost of submarine power cables, which can be used by policymakers, industry, and academia to better approximate the true cost of transmission expansion plans. The models are both generalizable and well-specified for a variety of submarine applications, across a variety of regions. The best performing statistical learning model has slightly more predictive power than a simpler, linear econometric model. The specific decision context will determine whether the extra data gathering effort for the statistical learning model is worth the additional precision. A case study illustrates that incorporating the uncertainty associated with the cost prediction to calculate risk metrics - value-at-risk and conditional-value-at-risk - provides useful information to the decision-maker about cost variability and extremes.     

Study of H2O adsorption on sulfides surfaces and thermokinetic analysis

Adsorption of water on mineral surfaces was studied using density functional theory and microcalorimetry technique. The calculation results show that galena and molybdenite are hydrophobic, while pyrite and sphalerite is hydrophilic. Thermokinetic analysis shows that the heat of adsorption is in decreasing order of pyrite, sphalerite, galena and molybdenite, which is in good agreement with the calculation results. The adsorption kinetics parameters of hydrophobic galena and molybdenite surfaces are close, while those of hydrophilic pyrite and sphalerite surfaces are very different. The adsorption rate of water on the sphalerite surface is larger than that of water on the pyrite surface.     

A novel anions and cations co-doped strategy for developing high-performance cobalt-free cathode for intermediate-temperature proton-conducting solid oxide fuel cells

The sluggish activity of cathode at intermediate-temperature limits commercialization of proton-conducting solid oxide fuel cells (H-SOFCs). In this investigation, a novel cathode of Ba_0.95Ca_0.05Fe_0.85Sn_0.05Y_0.1O_2.9−δF_0.1 was successfully developed by co-doping of anion F and cations Ca, Sn, Y. We studied the effect of F⁻-doping on phase structure, electrical conductivity and electrochemical properties of the cell. Compared with Ba_0.95Ca_0.05Fe_0.85Sn_0.05Y_0.1O_3−δ, F⁻-doped Ba_0.95Ca_0.05Fe_0.85Sn_0.05Y_0.1O_3−δ exhibited higher conductivity. Composite cathode consisting of Ba_0.95Ca_0.05Fe_0.85Sn_0.05Y_0.1O_2.9−δF_0.1 and Sm_0.2Ce_0.8O_2−δ was applied in H-SOFCs with BaZr_0.1Ce_0.7Y_0.2O_3−δ electrolyte which achieves an encouraging performance with the maximum power density of 1050 mW cm⁻² and polarization resistance of 0.04 Ω cm² at 700 °C. The result of First-principles calculations based on spin-polarized Density Functional Theory shows that doping of F⁻ reduces the activation energy required for migration of oxygen ions. These results demonstrate that the anions and cations co-doped strategy can provide a new horizon for the cathode in H-SOFCs.     

Doping sp-hybridized B atoms in graphyne supported single cobalt atoms for hydrogen evolution electrocatalysis

Electrochemical water splitting to hydrogen is considered as a promising approach for clean H₂ production. However, developing highly active and inexpensive electrocatalysts is an important part of the hydrogen evolution reaction (HER). Herein, we present a multifaceted atom (sp²-and sp-hybridized boron) doping strategy to directly fine-modify the electronic structures of the active site and the HER performance by the density functional theory calculations. It is found that the binding strength between the Co atom and the B doped graphyne nanosheets can be enhanced by doping B atoms. Meanwhile, the Co@B₁-GY and Co@B₂-GY catalysts exhibit good thermodynamic stability and high HER catalytic activity. Interestingly, the Co@B₂-GY catalyst has an ideal HER performance with the ΔG_H* value of −0.004 eV. Moreover, the d-band center of the Co atoms is upshifted by the sp²-or sp-hybridized B dopants. The concentrations of the sp-hybridized B atoms have a positive effect on the electrons transformation of the Co atoms. The interaction between the H and Co atoms becomes strong with the increase of the concentrations of the sp-hybridized B atoms and thus the corresponding catalysts show sluggish HER kinetics. This investigation could provide useful guidance for the experimental groups to directly and continuously control the catalytic activity towards HER by precisely doping multifaceted atoms.     

Thermodynamic property of ternary compound MgCaSi: A study from ab initio Debye-Grüneisen model

The thermodynamic properties of MgCaSi and its mother phase Ca₂Si are comparatively investigated from ab initio calculations and quasi-harmonic Debye-Grüneisen model. At 0 K, MgCaSi is more thermodynamically stable. Under high temperature, the advantage of higher thermodynamically stability of MgCaSi is reduced, originating from the less negative entropy contribution because the thermodynamic entropy of MgCaSi increases more slowly with temperature and the entropy values are slightly smaller. With increasing temperature, the anti-softening ability for MgCaSi is slightly smaller due to the slightly faster decrease trend of bulk modulus than that of Ca₂Si, although the bulk modulus of MgCaSi is higher in the whole temperature range considered. The thermal expansion behaviors of both MgCaSi and Ca₂Si exhibit similar increase trend, although thermal expansion coefficient of MgCaSi is slightly lower and the increases is slightly slower at lower temperature. The isochoric heat capacity and isobaric heat capacity of MgCaSi and Ca₂Si rise nonlinearly with temperature, and both are close to the Dulong–Petit limit at high temperature due to the negligibly small electronic contribution. The Debye temperature of both phases decrease with increasing temperature, and the downtrend for MgCaSi is slightly faster. However, MgCaSi possess slightly higher Debye temperature, implying the stronger chemical bonds and higher thermal conductivity than the mother phase Ca₂Si. The Grüneisen parameter of MgCaSi and Ca₂Si increase slightly with temperature, the values of MgCaSi are slightly larger. The investigation of electronic structures shows that with substitution of partial Ca by Mg in Ca₂Si, the stronger MgSi, MgCa and SiSi covalent bonds are formed, and plays a very significant role for the structural stability and mechanical properties.     

Structural and electronic properties of Ti-nanowires/C-single wall nanotubes composites by density functional theory calculations

Structural and electronic properties of composite Ti-nanowires/single wall carbon nanotubes ((6,0) and (10,0)) (SWNT) were evaluated by means of density functional theory computations. We considered the cases of monoatomic (MNW), BCC (β-NW) and HCP (α-NW) nanowires that were either inserted or deposited in/on the SWNTs. In all cases the NWs turn the cylindrical SWNTs’ shape to ellipsoid, an effect that is closely related to charge transfer from Ti toward C neighboring atoms. We found that the wires inside the SWNT appear to be more stable compared to the outside cases, while all NWs contribute with new energy states at the Fermi level, transforming the semiconducting (10,0) to a conducting composite. In addition, we found spin up–down differences in the β-NW_on case and electronic charge redistributions e.g. in α-NW_in (charge accumulation internally along the tube's axis) or in α-NW_on (superficial charge accumulation in the vicinity of the NW), accompanied by manifestation of electric dipole moment that reaches the value of 10 Debye in a-NW_on. These results may be of use in the design of new C-based nanocomposite systems suitable for applications in microelectronics, sensors and catalysis.     

Compton profiles of MoP and WP: Validation of second order generalized gradient approximation

Recently, Zhao and Truhlar (J. Chem. Phys. 128, 184109, 2008) have constructed second order generalized gradient approximation (SOGGA) within the density functional theory. The authors have successfully tested the performance of SOGGA by computing lattice constants, cohesive energies, bond distances and few energetic quantities of different solids and molecules. In this paper, to establish the usefulness of SOGGA in deducing the momentum densities, we have compared our experimental Compton profiles of MoP and WP with those computed using GGA and SOGGA within density functional theory. It is seen that SOGGAPBE based Compton profiles of both the samples are in better agreement with the corresponding experimental data than those derived from BPBE-GGA. In addition, energy bands, density of states and relative nature of bonding in both the phosphides is explained in terms of equal-valence-electron-density profiles and Mulliken’s population analysis.     

First-principles derived complexion diagrams for phase boundaries in doped cemented carbides

This article reviews a method for calculating an equilibrium interfacial phase diagram depicting regions of stability for different interface structures as function of temperature and chemical potentials. Density functional theory (DFT) is used for interfacial energies, Monte Carlo simulations together with cluster expansions based on DFT results for obtaining configurational free energies, and CALPHAD-type modeling for describing the thermodynamic properties of the adjoining bulk phases. An explicit case, vanadium doped cemented carbides, is chosen to illustrate the progress in the research field and the interfacial diagram, a complexion diagram, for the phase boundary WC(0 0 0 1)/Co is constructed as function of temperature and chemical potentials.     

Factorial 2 p–q Plans Robust Against Linear and Quadratic Trends

When the substrate of a 2 ^n–q factorial or fractional factorial experiment may be expected to show trends representable by linear and quadratic terms in time, then certain orderings spaced at equal time-intervals permit better estimation of the effects than do others. Some of these ordered plans are given for p – q = 2, 3, 4, 5. Simple methods are given for computing effects, trends, and efficiencies.     

Density and Young׳s Modulus of ternary glasses close to the eutectic composition in the CaO–Al2O3–SiO2-system

The elastic properties and the density of ternary glass forming systems within the CaO–SiO₂–Al₂O₃-system (CAS) were evaluated. Different glass compositions near the lowest eutectic (1170 °C) composition within the CaO–Al₂O₃–SiO₂-system have been melted from pure raw materials. Their target compositions differed not more than 4 wt% for each component. Exact chemical compositions were measured by x-ray fluorescence. The density, and acoustic properties were determined and the Young׳s Moduli were derived herefrom. It was of special interest to obtain information on these properties and their dependencies upon small variations in the composition. The density values were between 2.600 and 2.667 g cm⁻³ and the packing density factors V_p of the oxides glasses using the ionic radii of Pauling were in the range from 0.559 to 0.571. The determined data were compared to different model calculations. Density model calculations show relative deviations between 2 and 6%. The values calculated from the model for Young׳s Modulus by Makishima and Mackenzie (1973) [1] were somewhat smaller than the measured ones. The correction by Rocherulle et al. (1989) [3] of the Makishima model showed better agreement with the measured values.