Limits on the Benefits of Energy Storage for Renewable Integration

The high variability of renewable energy resources presents significant challenges to the operation of the electric power grid. Conventional generators can be used to mitigate this variability but are costly to operate and produce carbon emissions. Energy storage provides a more environmentally friendly alternative, but is costly to deploy in large amounts. This paper studies the limits on the benefits of energy storage to renewable energy: How effective is storage at mitigating the adverse effects of renewable energy variability? How much storage is needed? What are the optimal control policies for operating storage? To provide answers to these questions, we first formulate the power flow in a single-bus power system with storage as an infinite horizon stochastic program. We find the optimal policies for arbitrary net renewable generation process when the cost function is the average conventional generation (environmental cost) and when it is the average loss of load probability (reliability cost). We obtain more refined results by considering the multi-timescale operation of the power system. We view the power flow in each timescale as the superposition of a predicted (deterministic) component and an prediction error (residual) component and formulate the residual power flow problem as an infinite horizon dynamic program. Assuming that the net generation prediction error is an IID process, we quantify the asymptotic benefits of storage. With the additional assumption of Laplace distributed prediction error, we obtain closed form expressions for the stationary distribution of storage and conventional generation. Finally, we propose a two-threshold policy that trades off conventional generation saving with loss of load probability. We illustrate our results and corroborate the IID and Laplace assumptions numerically using datasets from CAISO and NREL.Comment: 45 pages, 17 figure

Asymptotic description of solitary wave trains in fully nonlinear shallow-water theory

We derive an asymptotic formula for the amplitude distribution in a fully nonlinear shallow-water solitary wave train which is formed as the long-time outcome of the initial-value problem for the Su-Gardner (or one-dimensional Green-Naghdi) system. Our analysis is based on the properties of the characteristics of the associated Whitham modulation system which describes an intermediate "undular bore" stage of the evolution. The resulting formula represents a "non-integrable" analogue of the well-known semi-classical distribution for the Korteweg-de Vries equation, which is usually obtained through the inverse scattering transform. Our analytical results are shown to agree with the results of direct numerical simulations of the Su-Gardner system. Our analysis can be generalised to other weakly dispersive, fully nonlinear systems which are not necessarily completely integrable.Comment: 25 pages, 7 figure

Visual Attention in 3D Video Games.

Understanding players’ visual attention patterns within an interactive 3D game environment is an important research area that can improve game level design and graphics. Several graphics techniques use a perception based rendering method to enhance graphics quality while achieving the fast rendering speed required for fast-paced 3D video games. Game designers can also enhance game play by adjusting the level design, texture and color choices, and objects’ locations, if such decisions are informed by a study of players’ visual attention patterns in 3D game environments. This paper seeks to address this issue. We present results showing different visual attention patterns that players exhibit in two different game types: action-adventure games and first person shooter games. In addition, analyzing visual attention patterns within a complex 3D game environment presents a new challenge because the environment is very complex with many rapidly changing conditions; the methods used in previous research cannot be used in such environments. In this paper, we will discuss our exploration seeking a new approach to analyze visual attention patterns within interactive 3D environments

Distributed Lossy Averaging

An information theoretic formulation of the distributed averaging problem previously studied in computer science and control is presented. We assume a network with m nodes each observing a WGN source. The nodes communicate and perform local processing with the goal of computing the average of the sources to within a prescribed mean squared error distortion. The network rate distortion function R^*(D) for a 2-node network with correlated Gaussian sources is established. A general cutset lower bound on R^*(D) is established and shown to be achievable to within a factor of 2 via a centralized protocol over a star network. A lower bound on the network rate distortion function for distributed weighted-sum protocols, which is larger in order than the cutset bound by a factor of log m is established. An upper bound on the network rate distortion function for gossip-base weighted-sum protocols, which is only log log m larger in order than the lower bound for a complete graph network, is established. The results suggest that using distributed protocols results in a factor of log m increase in order relative to centralized protocols.Comment: 25 pages, 1 figur

Removing Ilmenite-Based Filter Cakes Using Hydrochloric Acid and Chelating Agent – Experimental Study

Ilmenite is often used as a weighting agent in drilling fluids to increase the fluid density, but the formation of a filter cake on the borehole wall can impact cementing operations and reduce well productivity. To remove the filter cake, various techniques can be employed such as chemical treatments, mechanical methods, or a combination of both. The goal of this study is to evaluate the effectiveness of chemical removal of ilmenite-based filter cake using 7.5 wt.% hydrochloric acid (HCl) and hydroxyethyl ethylenediamine triacetic acid (HEDTA) – chelating agent. The filter cakes were generated using API filter press under harsh conditions of 300 psi pressure and 250°F temperature. Sandstone cores (2.5-in. diameter and 1-in. thickness) were utilized to replicate the formation during filtration experiments. The filtrate fluid was collected and the sandstone cores with filter cakes were scanned using computerized tomography (CT) technology. Immediately after that, the cores and filter cakes were soaked with HCl–HEDTA solution for 6 hours, followed by CT-scanning the cores and remaining filter cakes again. After acidizing, the effluent solution was analyzed using inductively coupled plasma (ICP). Scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS) was used to analyze the dried filter cakes and remaining residue. The results showed that, the use of 7.5 wt.% HCl was effective in partially removing the ilmenite-based filter cake. Additionally, the use of HEDTA showed limited effect on the efficiency of filter cake removal, but it effectively prevented corrosion problems during the treatment. This study presents useful findings on removing ilmenite-based filter cake with a low acid concentration and reducing the risk of corrosion issues

On the nonlinear dynamics of the traveling-wave solutions of the Serre system

We numerically study nonlinear phenomena related to the dynamics of traveling wave solutions of the Serre equations including the stability, the persistence, the interactions and the breaking of solitary waves. The numerical method utilizes a high-order finite-element method with smooth, periodic splines in space and explicit Runge-Kutta methods in time. Other forms of solutions such as cnoidal waves and dispersive shock waves are also considered. The differences between solutions of the Serre equations and the Euler equations are also studied.Comment: 28 pages, 20 figures, 3 tables, 33 references. Other author's papers can be downloaded at http://www.denys-dutykh.com

Allelic segregation and independent assortment in <i>T. brucei</i> crosses: proof that the genetic system is Mendelian and involves meiosis

The genetic system on Trypanosoma brucei has been analysed by generating large numbers of independent progeny clones from two crosses, one between two cloned isolates of Trypanosoma brucei brucei and one between cloned isolates of T. b. brucei and Trypanosoma brucei gambiense, Type 2. Micro and minisatellite markers (located on each of the 11 megabase housekeeping chromosomes) were identified, that are heterozygous in one or more of the parental strains and the segregation of alleles at each locus was then determined in each of the progeny clones. The results unequivocally show that alleles segregate in the predicted ratios and that alleles at loci on different chromosomes segregate independently. These data provide statistically robust proof that the genetic system is Mendelian and that meiosis occurs. Segregation distortion is observed with the minisatellite locus located on chromosome I of T. b. gambiense Type 2 and neighboring markers, but analysis of markers further along this chromosome did not show distortion leading to the conclusion that this is due to selection acting on one part of this chromosome. The results obtained are discussed in relation to previously proposed models of mating and support the occurrence of meiosis to form haploid gametes that then fuse to form the diploid progeny in a single round of mating

Performance and economic comparisons of manual and mechanised fertiliser applications for mature oil palm

The problem of labour shortage in addition to environmental hazard due to improper fertiliser application method calls for efficient and effective method of fertiliser application. This study compares the productivity of workers, human energy expenditure and operational cost between manual and mechanised method of fertiliser application operation for matured oil palm in Malaysia. Results indicate that workers' productivity increased by 3.74 times with mechanised method compared to the manual method based on the measured field capacities of 4.64 ha per hour and 1.24 ha per hour for the mechanised and manual methods, respectively. In addition, mechanised fertiliser application was 4.53 times less labour intensive than manual application based on the measured human energy expenditure of 2.03 kcal per min and 9.19 kcal per min for mechanised and manual methods, respectively However, the estimated total cost for the mechanised method is 1.6 times more than the manual method which amounted to an additional cost of RM4.18 per hectare based on the estimated total cost of RM11.10 per hectare and RM6.92 per hectare for mechanised and manual methods, respectively. The high estimated total cost of the mechanised method is due to the low annual usage of the tractor considered in the economic analysis for this study

Does Religiosity Affect Stock Investors’ Herding Behaviour? Global Evidence

We investigate if religiosity promotes herding among stock market investors. In a global sample of 21 markets over the period 2006–2018, increasing religiosity fosters herding only when the absolute religiosity level is relatively high. At low levels, an increase in religiosity has the opposite effect, promoting anti-herding. Our finding that changes in religiosity, depending on its level (high versus low), exert opposing effects on herding helps to understand contradictory findings in prior literature. Religiosity further induces more herding when economic freedom is low and the state is either impotent or corrupt, and promotes anti-herding when institutional quality is high

Prevalence of Newcastle disease virus antibodies in sera and eggs of helmeted guinea fowls (Numida meleagris galeata pallas) in Borno and Yobe States, Nigeria

The seroprevalence and maternal antibody profiles to Newcastle disease virus infection of guinea fowls  were studied using haemagglutination inhibition (HI) test, in Borno and Yobe States of Nigeria. Of 822 sera  and 354 egg yolk extracts tested, 327 (39.8%) and 242 (68.4%) were positive for NDV antibodies  respectively. The seroprevalence was significantly higher (P&lt; 0.05) in the dry (47%) than in the rainy  (32.8%) seasons. Maternal antibodies in egg yolk extract (sampled during the rainy season), were  significantly (P&lt; 0.05) higher (68.4%) than the seroprevalence. The frequency distribution of antibody  titers were skewed with 79.8% and 63.2 % of sera and egg yolk respectively having reciprocal antibody  titres ≤ 20. The geometric mean antibody titre was higher (P&lt; 0.05) in the dry season (3.7±2.0) than in  the rainy season (2.5 ±1.7). The geometric mean titre was also higher (P&lt;0.05) in egg (8.9±2.5) than in  sera (3.1±1.9). These results showed that Newcastle disease virus is enzootic among guinea fowls in Borno and Yobe states, especially in the dry season. The geometric mean titer of antibodies from egg yolk (8.9)  was below the protective reciprocal titres ≥35.4, suggesting the need for control measures immediately  after hatching. In addition, birds with titers ≤ 35.4 are partially immune and may shed the virus without a clinical disease when infected thereby becoming a risk to in-contact birds.Keywords: Egg, Guinea fowls, Maternal antibodies Newcastle disease, Seroprevalenc