Optimal Carbon Taxes for Emissions Targets in the Electricity Sector

The most dangerous effects of anthropogenic climate change can be mitigated by using emissions taxes or other regulatory interventions to reduce greenhouse gas (GHG) emissions. This paper takes a regulatory viewpoint and describes the Weighted Sum Bisection method to determine the lowest emission tax rate that can reduce the anticipated emissions of the power sector below a prescribed, regulatorily-defined target. This bi-level method accounts for a variety of operating conditions via stochastic programming and remains computationally tractable for realistically large planning test systems, even when binary commitment decisions and multi-period constraints on conventional generators are considered. Case studies on a modified ISO New England test system demonstrate that this method reliably finds the minimum tax rate that meets emissions targets. In addition, it investigates the relationship between system investments and the tax-setting process. Introducing GHG emissions taxes increases the value proposition for investment in new cleaner generation, transmission, and energy efficiency; conversely, investing in these technologies reduces the tax rate required to reach a given emissions target

Testable polarization predictions for models of CMB isotropy anomalies

Anomalies in the large-scale CMB temperature sky measured by WMAP have been suggested as possible evidence for a violation of statistical isotropy on large scales. In any physical model for broken isotropy, there are testable consequences for the CMB polarization field. We develop simulation tools for predicting the polarization field in models that break statistical isotropy locally through a modulation field. We study two different models: dipolar modulation, invoked to explain the asymmetry in power between northern and southern ecliptic hemispheres, and quadrupolar modulation, posited to explain the alignments between the quadrupole and octopole. For the dipolar case, we show that predictions for the correlation between the first 10 multipoles of the temperature and polarization fields can typically be tested at better than the 98% CL. For the quadrupolar case, we show that the polarization quadrupole and octopole should be moderately aligned. Such an alignment is a generic prediction of explanations which involve the temperature field at recombination and thus discriminate against explanations involving foregrounds or local secondary anisotropy. Predicted correlations between temperature and polarization multipoles out to l = 5 provide tests at the ~ 99% CL or stronger for quadrupolar models that make the temperature alignment more than a few percent likely. As predictions of anomaly models, polarization statistics move beyond the a posteriori inferences that currently dominate the field.Comment: 17 pages, 15 figures; published in PRD; references adde

Teaching Tip: developing an intercollegiate Twitter forum to aid student exam study and the development of digital professionalism

#VetFinals has been developed as a novel online Twitter teaching event designed to support intercollegiate veterinary teaching using social media. Previous studies in other fields have suggested that Twitter use within universities may have benefits for undergraduate education. This “teaching tip” paper describes a project using Twitter to host online exam study sessions. The project has been a highly successful collaborative effort between the Royal Veterinary College and Nottingham Veterinary School in the UK. Over 4 years, the #VetFinals project has developed into a long-term, self-sustaining enterprise. This initiative provides a semi-structured means for student exam preparation with direct real-time input from a faculty member. It also creates a network of peers both horizontally across institutions and vertically throughout year groups. Based on similar initiatives in other disciplines, an anticipated outcome of this project was to contribute to student online professionalism. This could help address the veterinary community's recently highlighted problems with professional conduct and appropriate use of social media. Analysis of the success of this endeavor will be available in a future publication

Tris(ethane-1,2-diamine-κ2 N,N′)nickel(II) diiodide

The title compound, [Ni(C2H8N2)3]I2, crystallizes with an [Ni(en)3 2+] cation (en is ethane-1,2-diamine) and two iodide ions in the asymmetric unit. Two of the en ligands surrrounding the Ni2+ ion have disordered C atoms, while the third exhibits extensive weak N—H⋯I inter­actions with the two iodide ions that extend throughout the crystalline lattice, producing an infinite network along (011)

Uncertainty-Informed Renewable Energy Scheduling: A Scalable Bilevel Framework

Accommodating the uncertainty of variable renewable energy sources (VRES) in electricity markets requires sophisticated and scalable tools to achieve market efficiency. To account for the uncertain imbalance costs in the real-time market while remaining compatible with the existing sequential market-clearing structure, our work adopts an uncertainty-informed adjustment toward the VRES contract quantity scheduled in the day-ahead market. This mechanism requires solving a bilevel problem, which is computationally challenging for practical large-scale systems. To improve the scalability, we propose a technique based on strong duality and McCormick envelopes, which relaxes the original problem to linear programming. We conduct numerical studies on both IEEE 118-bus and 1814-bus NYISO systems. Results show that the proposed relaxation can achieve good performance in accuracy (0.7%-gap in the system cost wrt. the least-cost stochastic clearing benchmark) and scalability (solving the NYISO system in minutes). Furthermore, the benefit of the uncertainty-informed VRES-quantity adjustment is more significant under higher levels of VRES (e.g., 70%), under which the system cost can be reduced substantially compared to a myopic day-ahead offer strategy of VRES.Comment: Submitted to IEEE PES general meeting 202

Seismic-scale petrophysical interpretation and gas-volume estimation from simultaneous impedance inversion

© 2017 by The Society of Exploration Geophysicists. Simultaneous impedance inversion was performed to obtain the seismic-scale P-and S-wave impedances as well as the bulk density volumes from seismic angle stacks at a siliciclastic turbidite offshore gas reservoir. To translate these variables into seismic-scale total porosity (φ), clay content, and water saturation (S w ), we used a deterministic rock-physics model established at the well. A crucial input into this model is the bulk modulus (K f ) of the brine/gas system. We need to link it to S w at the seismic scale. This link can be one of simple mixing laws, such as harmonic and arithmetic. Alternately, it can be derived at the well by using upscaled variables and ensuring that they obey the well-data-driven rock-physics model. These different K f -S w relations produce different interpretations for φ and S w thus allowing one to assess the variability in the estimates of the gas volume in place that is proportional to the product of φ and (1 - S w )

Tris(ethane-1,2-diamine-κ2 N,N′)cobalt(III) carbonate iodide tetra­hydrate

The title compound, [Co(C2H8N2)3](CO3)I·4H2O, crystallizes with a [Co(en)3]3+ cation (en is ethane-1,2-diamine), CO3 2− and I− anions and four water mol­ecules in the asymmetric unit. In the cation, the three rings formed by the ethyl­enediamine units and the CoIII metal ion are in slightly distorted twist conformations. Numerous O—H⋯O, N—H⋯O, N—H⋯I and O—H⋯I inter­molecular hydrogen bonds between the cation and two anions in concert with the four water mol­ecules dominate the crystal packing and create a supra­molecular infinite three-dimensional framework

BICEP2 / Keck Array VIII: Measurement of gravitational lensing from large-scale B-mode polarization

We present measurements of polarization lensing using the 150 GHz maps which include all data taken by the BICEP2 & Keck Array CMB polarization experiments up to and including the 2014 observing season (BK14). Despite their modest angular resolution ($\sim 0.5^\circ$), the excellent sensitivity ($\sim 3\mu$K-arcmin) of these maps makes it possible to directly reconstruct the lensing potential using only information at larger angular scales ($\ell\leq 700$). From the auto-spectrum of the reconstructed potential we measure an amplitude of the spectrum to be $A^{\phi\phi}_{\rm L}=1.15\pm 0.36$ (Planck $\Lambda$CDM prediction corresponds to $A^{\phi\phi}_{\rm L}=1$), and reject the no-lensing hypothesis at 5.8$\sigma$, which is the highest significance achieved to date using an EB lensing estimator. Taking the cross-spectrum of the reconstructed potential with the Planck 2015 lensing map yields $A^{\phi\phi}_{\rm L}=1.13\pm 0.20$. These direct measurements of $A^{\phi\phi}_{\rm L}$ are consistent with the $\Lambda$CDM cosmology, and with that derived from the previously reported BK14 B-mode auto-spectrum ($A^{\rm BB}_{\rm L}=1.20\pm 0.17$). We perform a series of null tests and consistency checks to show that these results are robust against systematics and are insensitive to analysis choices. These results unambiguously demonstrate that the B-modes previously reported by BICEP / Keck at intermediate angular scales ($150\lesssim\ell\lesssim 350$) are dominated by gravitational lensing. The good agreement between the lensing amplitudes obtained from the lensing reconstruction and B-mode spectrum starts to place constraints on any alternative cosmological sources of B-modes at these angular scales.Comment: 12 pages, 8 figure