bluuebunny/crossref_metadata_2025 huggingface dataset:
Transcriptome‐wide sequencing provides insights into geocarpy in peanut (Arachis hypogaea L.)
Authors: Chen Xiaoping , Yang Qingli , Li Haifen , Li Heying , Hong Yanbin , Pan Lijuan , Chen Na , Zhu Fanghe , Chi Xiaoyuan , Zhu Wei , Chen Mingna , Liu Haiyan , Yang Zhen , Zhang Erhua , Wang Tong , Zhong Ni , Wang Mian , Liu Hong , Wen Shijie , Li Xingyu , Zhou Guiyuan , Li Shaoxiong , Wu Hong , Varshney Rajeev , Liang Xuanqiang , Yu Shanlin
Published: October 2015

A characteristic feature of peanut is the subterranean fructification, geocarpy, in which the gynophore (‘peg’), a specialized organ that transitions from upward growth habit to downward outgrowth upon fertilization, drives the developing pod into the soil for subsequent development underground. As a step towards understanding this phenomenon, we explore the developmental dynamics of the peanut pod transcriptome at 11 successive stages. We identified 110 217 transcripts across developmental stages and quantified their abundance along a pod developmental gradient in pod wall. We found that the majority of transcripts were differentially expressed along the developmental gradient as well as identified temporal programs of gene expression, including hundreds of transcription factors. Thought to be an adaptation to particularly harsh subterranean environments, both up‐ and down‐regulated gene sets in pod wall were enriched for response to a broad array of stimuli, like gravity, light and subterranean environmental factors. We also identified hundreds of transcripts associated with gravitropism and photomorphogenesis, which may be involved in the geocarpy. Collectively, this study forms a transcriptional baseline for geocarpy in peanut as well as provides a considerable body of evidence that transcriptional regulation in peanut aerial and subterranean fruits is complex.
Engineered selective plant male sterility through pollen‐specific expression of theEcoRIrestriction endonuclease
Authors: Millwood Reginald J. , Moon Hong S. , Poovaiah Charleson R. , Muthukumar Balasubramaniam , Rice John Hollis , Abercrombie Jason M. , Abercrombie Laura L. , Green William Derek , Stewart Charles Neal
Published: October 2015

Unintended gene flow from transgenic plants via pollen, seed and vegetative propagation is a regulatory concern because of potential admixture in food and crop systems, as well as hybridization and introgression to wild and weedy relatives. Bioconfinement of transgenic pollen would help address some of these concerns and enable transgenic plant production for several crops where gene flow is an issue. Here, we demonstrate the expression of the restriction endonucleaseEcoRIunder the control of the tomato pollen‐specificLAT52 promoter is an effective method for generating selective male sterility inNicotiana tabacum(tobacco). Of nine transgenic events recovered, four events had very high bioconfinement with tightly controlledEcoRIexpression in pollen and negligible‐to‐no expression other plant tissues. Transgenic plants had normal morphology wherein vegetative growth and reproductivity were similar to nontransgenic controls. In glasshouse experiments, transgenic lines were hand‐crossed to both male‐sterile and emasculated nontransgenic tobacco varieties. Progeny analysis of 16 000–40 000 seeds per transgenic line demonstrated five lines approached (>99.7%) or attained 100% bioconfinement for one or more generations. Bioconfinement was again demonstrated at or near 100% under field conditions where four transgenic lines were grown in close proximity to male‐sterile tobacco, and 900–2100 seeds per male‐sterile line were analysed for transgenes. Based upon these results, we concludeEcoRI‐driven selective male sterility holds practical potential as a safe and reliable transgene bioconfinement strategy. Given the mechanism of male sterility, this method could be applicable to any plant species.
Oligonucleotide‐directed mutagenesis for precision gene editing
Authors: Sauer Noel J. , Mozoruk Jerry , Miller Ryan B. , Warburg Zachary J. , Walker Keith A. , Beetham Peter R. , Schöpke Christian R. , Gocal Greg F. W.
Published: October 2015

Differences in gene sequences, many of which are single nucleotide polymorphisms, underlie some of the most important traits in plants. With humanity facing significant challenges to increase global agricultural productivity, there is an urgent need to accelerate the development of these traits in plants. oligonucleotide‐directed mutagenesis (ODM), one of the many tools of Cibus’ Rapid Trait Development System (RTDS™) technology, offers a rapid, precise and non‐transgenic breeding alternative for trait improvement in agriculture to address this urgent need. This review explores the application of ODM as a precision genome editing technology, with emphasis on using oligonucleotides to make targeted edits in plasmid, episomal and chromosomal DNA of bacterial, fungal, mammalian and plant systems. The process of employing ODM by way of RTDS technology has been improved in many ways by utilizing a fluorescence conversion system wherein a blue fluorescent protein (BFP) can be changed to a green fluorescent protein (GFP) by editing a single nucleotide of the BFP gene (CAC→TAC; H66 to Y66). For example, dependent on oligonucleotide length, applying oligonucleotide‐mediated technology to target the BFP transgene in Arabidopsis thaliana protoplasts resulted in up to 0.05% precisely edited GFP loci. Here, the development of traits in commercially relevant plant varieties to improve crop performance by genome editing technologies such as ODM, and by extension RTDS, is reviewed.
Different Ways of Being Authoritarian: The Distinct Effects of Authoritarian Dimensions on Values and Prejudice
Authors: Passini Stefano
Published: October 2015

The traditional and still dominant approach to authoritarianism measures it as a unidimensional construct. However, in the past few years some studies have assessed the three hypothesized authoritarianism components (i.e., authoritarian submission, authoritarian aggression, and conventionalism) separately. The aims of this study are to verify that the three‐correlated‐factor structure fits the data better than the one‐factor model and to analyze the distinct effects of the three dimensions of authoritarianism on values and prejudice. A total of 169 Italian citizens responded to a questionnaire. As hypothesized, a structural equation model shows that the dimension of authoritarian submission is mainly related to the openness to change vs. conservation values opposition; the dimension of authoritarian aggression is more characterized on the self‐transcendence vs. self‐enhancement values opposition; conventionalism is mainly linked to traditional values. As concerns prejudice, this variable is predicted just by authoritarian aggression. Theoretical implications as concerns the conceptualization of authoritarianism are discussed.
Mixtures, Envelopes and Hierarchical Duality
Authors: Polson Nicholas G. , Scott James G.
Published: October 2015

We develop a connection between mixture and envelope representations of objective functions that arise frequently in statistics. We refer to this connection by using the term ‘hierarchical duality’. Our results suggest an interesting and previously underexploited relationship between marginalization and profiling, or equivalently between the Fenchel–Moreau theorem for convex functions and the Bernstein–Widder theorem for Laplace transforms. We give several different sets of conditions under which such a duality result obtains. We then extend existing work on envelope representations in several ways, including novel generalizations to variance–mean models and to multivariate Gaussian location models. This turns out to provide an elegant missing data interpretation of the proximal gradient method, which is a widely used algorithm in machine learning. We show several statistical applications in which the framework proposed leads to easily implemented algorithms, including a robust version of the fused lasso, non-linear quantile regression via trend filtering and the binomial fused double-Pareto model. Code for the examples is available on GitHub at https://github.com/jgscott/hierduals.
Generalized Additive and Index Models with Shape Constraints
Authors: Chen Yining , Samworth Richard J.
Published: October 2015

We study generalized additive models, with shape restrictions (e.g. monotonicity, convexity and concavity) imposed on each component of the additive prediction function. We show that this framework facilitates a non-parametric estimator of each additive component, obtained by maximizing the likelihood. The procedure is free of tuning parameters and under mild conditions is proved to be uniformly consistent on compact intervals. More generally, our methodology can be applied to generalized additive index models. Here again, the procedure can be justified on theoretical grounds and, like the original algorithm, has highly competitive finite sample performance. Practical utility is illustrated through the use of these methods in the analysis of two real data sets. Our algorithms are publicly available in the R package scar, short for shape-constrained additive regression.
Group Contests with Internal Conflict and Power Asymmetry
Authors: Choi Jay Pil , Chowdhury Subhasish M. , Kim Jaesoo
Published: October 2015

We investigate simultaneous inter‐ and intra‐group conflict in the shadow of within‐group power asymmetry and complementarity in members' group‐conflict efforts. A more symmetric group faces a higher degree of internal conflict, and might expend more effort in external conflict when the group‐conflict effort technology is highly complementary. Depending on the degree of complementarity, the stronger player's relative contribution to external conflict might be higher in a more asymmetric group and, as a result, it is possible for the weaker player to earn a higher payoff. In the absence of any complementarity, the rent‐dissipation is non‐monotonic with the within‐group power asymmetry.
Household Formation, Female Labor Supply, and Savings
Authors: Fehr Hans , Kallweit Manuel , Kindermann Fabian
Published: October 2015

In this paper, we aim to quantify the impact of changing family structures on labor supply and savings in Western societies. Our dynamic general equilibrium model features both genders, and it takes into account changes in marital status as a stochastic process. The numerical results indicate that changes in household formation can partly explain the reallocation of male and female labor supply observed during the last decades in Germany. We also find a negative impact on capital accumulation, and we show that a combination of higher marital risk and a narrowing gender wage gap can explain the changes in hours ratios between single and married men and women.
Is There a Causal Effect of Working Part‐Time on Current and Future Wages?
Authors: Paul Marie
Published: October 2015

In this paper, I study the causal effects of part‐time work on current and future wages. To estimate these effects, I use a random effects model with a wage equation capturing the employment history and a dynamic multinomial probit component for the choice of employment status. Exclusion restrictions from the institutional context are exploited to support identification. The results suggest that working part‐time with few hours has a large causal effect on current wages, but more extensive part‐time work does not reduce current wages. However, both types of part‐time work lead to negative long‐term wage effects.
Immigration, Conflict, and Redistribution
Authors: Sánchez‐Pagés Santiago , Solano García Ángel
Published: October 2015

In this paper, we analyze how the possibility of conflict between natives and immigrants shapes income redistribution in developed democracies. This possibility can generate income redistribution towards immigrants even if they have no voting rights. We show that the threat of conflict between natives and immigrants lowers vertical income redistribution (from the rich to the poor) as the level of immigration increases. The opposite holds for horizontal income redistribution (from natives to immigrants), which increases with the level of immigration. Income inequality weakens the negative effect of immigration on vertical redistribution, but it also reduces horizontal redistribution. These theoretical predictions are consistent with the results of our empirical analysis on data from 29 European countries: larger immigrant populations are associated with more redistribution towards immigrants and lower vertical redistribution.
Impact of Immigration on Inhabitants' Educational Investments
Authors: Røed Marianne , Schøne Pål
Published: October 2015

We examine whether immigration into the labour market of the building and construction (BaC) industry affects enrolment in vocational programmes that teach the skills required in this industry. Results suggest that a higher supply of immigrant labour is associated with lower enrolment into programmes teaching BaC skills. The strength of this relationship increases according to the grades that the students achieved in lower secondary school. This finding indicates that the negative effect of immigration on educational recruitment is mainly caused by students who turn away from these programmes, rather than a reduction in apprenticeship positions offered by employers.
The deletion of /t, d/ in Hong Kong English
Authors: EDWARDS JETTE G. HANSEN
Published: October 2015

Previous research on /t,d/ deletion, the omission of the final /t/ or /d/ sound in word‐final consonant clusters of two or more consonants (e.g. just pronounced as jus), indicates that it is pervasive in many varieties of English, including world Englishes such as Indian English, Singapore English, and Nigerian English. This study examines /t,d/ deletion in Hong Kong English in order to examine whether the finding that it occurs systematically across a wide range of Englishes can be extended to this new English. Conversational data were collected from 36 Hong Kong tertiary students; analysis of the data via both descriptive and inferential statistics found that /t,d/ deletion occurred for all the participants in the study, and was governed by linguistic factors and in particular, grammatical category and following linguistic environment.
Corticospinal axons make direct synaptic connections with spinal motoneurons innervating forearm muscles early during postnatal development in the rat
Authors: Maeda Hitoshi , Fukuda Satoshi , Kameda Hiroshi , Murabe Naoyuki , Isoo Noriko , Mizukami Hiroaki , Ozawa Keiya , Sakurai Masaki
Published: October 2015

Key points

Direct connections between corticospinal (CS) axons and motoneurons (MNs) appear to be present only in higher primates, where they are essential for discrete movement of the digits. Their presence in adult rodents was once claimed but is now questioned.

We report that MNs innervating forearm muscles in infant rats receive monosynaptic input from CS axons, but MNs innervating proximal muscles do not, which is a pattern similar to that in primates.

Our experiments were carefully designed to show monosynaptic connections. This entailed selective electrical and optogenetic stimulation of CS axons and recording from MNs identified by retrograde labelling from innervated muscles. Morphological evidence was also obtained for rigorous identification of CS axons and MNs.

These connections would be transient and would regress later during development.

These results shed light on the development and evolution of direct CS–MN connections, which serve as the basis for dexterity in humans.

Recent evidence suggests there is no direct connection between corticospinal (CS) axons and spinal motoneurons (MNs) in adult rodents. We previously showed that CS synapses are present throughout the spinal cord for a time, but are eliminated from the ventral horn during development in rodents. This raises the possibility that CS axons transiently make direct connections with MNs located in the ventral horn of the spinal cord. This was tested in the present study. Using cervical cord slices prepared from rats on postnatal days (P) 7–9, CS axons were stimulated and whole cell recordings were made from MNs retrogradely labelled with fluorescent cholera toxin B subunit (CTB) injected into selected groups of muscles. To selectively activate CS axons, electrical stimulation was carefully limited to the CS tract. In addition we employed optogenetic stimulation after injecting an adeno‐associated virus vector encoding channelrhodopsin‐2 (ChR2) into the sensorimotor cortex on P0. We were then able to record monosynaptic excitatory postsynaptic currents from MNs innervating forearm muscles, but not from those innervating proximal muscles. We also showed close contacts between CTB‐labelled MNs and CS axons labelled through introduction of fluorescent protein‐conjugated synaptophysin or the ChR2 expression system. We confirmed that some of these contacts colocalized with postsynaptic density protein 95 in their partner dendrites. It is intriguing from both phylogenetic and ontogenetic viewpoints that direct and putatively transient CS–MN connections were found only on MNs innervating the forearm muscles in infant rats, as this is analogous to the connection pattern seen in adult primates.
Fundamental role for the KCNE4 ancillary subunit in Kv7.4 regulation of arterial tone
Authors: Jepps Thomas A. , Carr Georgina , Lundegaard Pia R. , Olesen Søren‐Peter , Greenwood Iain A.
Published: October 2015

Key points

KCNE4 alters the biophysical properties and cellular localization of voltage‐gated potassium channel Kv7.4.

KCNE4 is expressed in a variety of arteries and, in mesenteric arteries, co‐localizes with Kv7.4, which is important in the control of vascular contractility.

Knockdown of KCNE4 leads to reduced Kv7.4 membrane abundance, a depolarized membrane potential and an augmented response to vasoconstrictors.

KCNE4 is a key regulator of the function and expression of Kv7.4 in vascular smooth muscle.

The KCNE ancillary subunits (KCNE1–5) significantly alter the expression and function of voltage‐gated potassium channels; however, their role in the vasculature has yet to be determined. The present study aimed to investigate the expression and function of the KCNE4 subunit in rat mesenteric arteries and to determine whether it has a functional impact on the regulation of arterial tone by Kv7 channels. In HEK cells expressing Kv7.4, co‐expression of KCNE4 increased the membrane expression of Kv7.4 and significantly altered Kv7.4 current properties. Quantitative PCR analysis of different rat arteries found that the KCNE4 isoform predominated and proximity ligation experiments showed that KCNE4 co‐localized with Kv7.4 in mesenteric artery myocytes. Morpholino‐induced knockdown of KCNE4 depolarized mesenteric artery smooth muscle cells and resulted in their increased sensitivity to methoxamine being attenuated (mean ± SEM EC50 decreased from 5.7 ± 0.63 μm to 1.6 ± 0.23 μm), which coincided with impaired effects of Kv7 modulators. When KCNE4 expression was reduced, less Kv7.4 expression was found in the membrane of the mesenteric artery myocytes. These data show that KCNE4 is consistently expressed in a variety of arteries, and knockdown of the expression product leads to reduced Kv7.4 membrane abundance, a depolarized membrane potential and an augmented response to vasoconstrictors. The present study is the first to demonstrate an integral role of KCNE4 in regulating the function and expression of Kv7.4 in vascular smooth muscle.
Self-Sufficient Photovoltaic Powered Chiller for Dairy Applications
Authors: Alabdulkarem Abdullah , Muehlbauer Jan , Hwang Yunho , Radermacher Reinhard
Published: October 2015

Milk spoilage is a common issue in remote dairy farms due to the unavailability of power grid. Many farmers rely on diesel engines to power their milk chillers. A sustainable approach is to replace the environmentally harmful diesel generators with solar powered chillers. Solar energy is attractive in such application because the peak cooling demand occurs at the peak solar irradiance. Solar energy can be converted to cooling through PV powered chiller or through thermally driven chillers. This concept was applied to a Modular Solar Bulk Milk Chiller (MilkPod™) which uses the solar energy to generate electricity in 6 kWp PV panels. The system cools 600 liters of milk per day as well as produces hot water for cleaning the milk tank. A detailed model was used in the design process and the system equipment were selected such that the system uses about 98% of its energy from the sun throughout the year. The effect of the solar energy utilization ratio, equipment supplied current as well as milk loading were investigated on the system performance.
Comparison of an Engineering Model and a Statistical Model to Estimate the Performance of a Solar Photovoltaic System
Authors: Fumo Nelson , Zambrano Juan Carlo , Bortone Vicente
Published: October 2015

At the design stage of a solar photovoltaic (PV) system, equipment’s information from the specifications provided by manufacturers is the most reliable information. Parameters used to describe the performance are obtained under laboratory conditions, but the information is the appropriate for estimating the performance of the components of the solar PV system. When a system is in operation, the engineering models used at the design stage can also be used to predict the performance of the system. However, under real conditions, many factors can affect the performance which suggests that statistical models developed with field data could give better results to predict the performance of a solar PV system. Experimental data used in this study correspond to the energy generated by a 7.5 kW PV system installed to supply electricity to a research house at the University of Texas at Tyler, as well as the outdoor temperature and global horizontal solar radiation (as energy) recorder on site. The data is used to develop a multiple linear regression model and compare this model with an engineering model. Results show that the statistical model has a better quality than the engineering model.
Hybrid Stirling/Otto Cycle for CCHP
Authors: Welty Stephen
Published: October 2015

The use of a novel thermodynamic cycle combined with a high efficiency expander and compressor provides a unique product opportunity for residential, commercial and industrial Combined Cooling, Heating and Power (CCHP) applications. The cycle can be described as a combination between a Stirling Cycle and an Otto Cycle with isothermal compression followed by constant volume heat addition then by isentropic expansion with the final process being heat addition or heat reject in either a constant volume or constant pressure process. The cycle can be run in an open cycle or a closed cycle with the closed cycle providing a more compact device for a given capacity while the open cycle provides an opportunity to get rid of one of the heat exchangers and cool or heat the air directly.
Optimal Operation Strategies for Thermal Energy Storage Systems in Solar Thermal Power Plants
Authors: Tse Louis A. , Wirz Richard E. , Lavine Adrienne S.
Published: October 2015

This paper examines the economic benefits of various operation strategies for a thermal energy storage (TES) system in a solar thermal power plant. A thermodynamic model developed to evaluate different design options has been utilized to calculate system performance and assess the impact of operation strategies, storage capacity, and market prices on the value of TES. The overall performance is also investigated through several parametric studies, such as solar multiple, geographic location, and choice of HTF. The influence of these parameters has been evaluated in consideration of exergy destruction due to heat transfer and pressure drop. By incorporating exergy-based optimization alongside traditional energy analyses, the results of this study evaluate the optimal values for key parameters in the design and operation of TES systems, as well as highlight opportunities to minimize thermodynamic losses. Annual performance for each case is characterized both by nominal and part-load efficiency. Levelized cost of electricity (LCOE) is calculated for all cases, illustrating a set of optimal parameters that yield a minimum LCOE value.
Gas Turbine Engine Exhaust Waste Heat Recovery Using Supercritical CO2 Brayton Cycle With Thermoelectric Generator Technology
Authors: Di Bella Francis A.
Published: October 2015

This presentation will discuss the results of the feasibility analysis of a Brayton cycle-based, supercritical CO2 system that recovers waste heat from an MT30 gas turbine used in marine applications. The analysis also included the use of thermoelectric generator (TEG) devices that are one of several direct energy conversion methods known to be applicable to waste heat recovery. The analysis was conducted by Concepts NREC, in collaboration with the Maine Maritime Academy and their principal consultant, Thermoelectric Power Systems, LLC. The feasibility analysis was conducted under Navy SBIR Proposal Number N103-229-0533, entitled “Gas Turbine Engine Exhaust Waste Heat Recovery Shipboard Module Development”. The objective of the project was to improve the energy efficiency of the MT30 prime-mover power system for the Navy and other commercial vessels. The performance goal for the energy recovery system was to improve the fuel economy of the prime mover by 20% when significantly part-loaded.
Experimental Investigation of Divider Plate Assisted Thermocline Storage
Authors: Codd Daniel S.
Published: October 2015

A new type of single-tank thermal energy storage (TES) with an actuated, loose-fitting insulated divider plate positioned between the hot and cold fluids is described, based on the CSPonD volumetric molten salt thermal receiver with integrated TES concept. A 240 L lab-scale assisted thermocline tank was fabricated and tested using water as the working fluid, connected to a 5 kW heat addition and extraction loop. The axial position of the divider plate was controlled to follow the thermocline interface as energy was added or removed under various charge-store-discharge profiles. For 6 hour storage cycles, the divider plate tank exhibited a round-trip storage efficiency of 0.53, compared to 0.46 for the baseline tank, a 14% improvement. Output temperatures remained within 90% of initial values for 89% of the divider plate tank volume, as compared to only 58% for the baseline case, representing a 53% improvement in usable storage capacity. Internal conduction losses were found to be less for the divider plate tank and correlated well with models (measured 83–93% values vs 86% internal loss prediction).
Transient Turbulent Natural Convection in Vertical Tubes for Indirect Thermal Energy Storage
Authors: Lakeh Reza Baghaei , Kavehpour H. Pirouz , Wirz Richard E. , Lavine Adrienne S.
Published: October 2015

In this study, turbulent natural convection heat transfer during the charge cycle of a Thermal Energy Storage system was studied computationally and analytically. The storage fluids were supercritical CO2 and liquid toluene which are stored in vertical and sealed storage tubes. A computational model was developed and validated to study turbulent natural convection during the charge cycle. The results of this study show that the aspect ratio of the storage tube (L/D) has an important effect on the heat transfer characteristics. A conceptual model was developed that views the thermal storage process as a hot boundary layer that rises along the tube wall and falls in the center to replace the cold fluid in the core. This model shows that dimensionless mean temperature of the storage fluid and average Nusselt number are functions of a Buoyancy-Fourier number.
Solar Updraft Tower Project
Authors: Monemi Sean , Easton Matt , Freire Chris
Published: October 2015

In this project, we designed a small scale model of a solar updraft tower. Our design was based upon previous renderings for solar updraft towers in Spain and Arizona. The purpose of our small scale solar updraft tower was twofold: 1) to prove the theory behind the solar updraft tower is plausible and 2) to produce enough energy to charge a battery storage system. The battery storage system would be used as a backup for fault conditions in our Smart Grid system. Our main objectives were to find optimal dimensions and materials to construct our solar updraft tower, all within the constraints of a budget. Our goal was to use what we’ve learned through design and testing to expand the knowledge of solar updraft towers.
Impact of Passive Cooling Strategies on Energy Consumption Reduction of Residential Buildings in the Kingdom of Saudi Arabia
Authors: Alaidroos Alaa , Krarti Moncef
Published: October 2015

In this paper, passive cooling strategies have been investigated to evaluate their effectiveness in reducing cooling thermal loads and air conditioning energy consumption for residential buildings in Kingdom of Saudi Arabia (KSA). Specifically, three passive cooling techniques have been evaluated including: natural ventilation, downdraft evaporative cooling, and earth tube cooling. These passive cooling systems are applied to a prototypical KSA residential villa model with an improved building envelope. The analysis has been carried using detailed simulation tool for several cities representing different climate conditions throughout KSA. It is found that both natural ventilation and evaporative cooling provide a significant reduction in cooling energy for the prototypical villa located in Riyadh. Natural ventilation alone has reduced the cooling energy end-use by 22% and the total villa energy consumption by 10%, while the evaporative cooling system has resulted in 64% savings in cooling energy end-use and 32% in the total villa energy consumption. When applying both passive cooling systems together to the villa, the cooling energy end-use is significantly reduced by about 84.2% and the total villa energy savings by 62.3% relative to the un-insulated basecase residential building model. Moreover, natural ventilation is found to have a high potential in all KSA climates, while evaporative cooling can be suitable only in hot and dry climates such as Riyadh and Tabuk.
Feasibility Study of Distributed Energy Generation at a Colorado Ski Resort
Authors: Krarti Moncef
Published: October 2015

The ski industry in Colorado is the largest in the United States and makes up a significant portion of the state’s tourism revenue, but changes in the climate threaten the future of this highly weather-dependent business. In recent years, many ski resorts have taken steps to reduce greenhouse gas emissions in an effort to mitigate the effects shorter winters, less snowfall, and continued drought are having on the future viability of the industry. Energy efficiency and renewable energy projects are common strategies to reduce emissions; less common, however, are resort-wide analyses of distributed generation (DG) systems combining traditional and alternative energy sources. The intent of this study is to evaluate the economic and technical feasibility of a hybrid conventional-renewable DG system at Vail Resort.

Electrical and thermal loads for Vail’s mountain operations were used to analyze three DG technologies; combined heat and power (CHP), photovoltaics (PV), and horizontal axis wind turbines. Technologies were chosen based on a resource assessment as well as input from site managers and analyzed using the Hybrid Optimization Model for Electric Renewables (HOMER). The results indicate that the most cost-competitive DG system is a 700 kilowatt (kW) natural gas-fired CHP plant used to meet the site’s base load during the summer months. Although CHP systems are generally most effective at displacing conventional grid-based power for facilities with little seasonal load variation, the findings of this study align closely with an existing system at Snowbird Resort in Utah.

A small 700 kW CHP system could provide approximately 31% of annual electricity use and 24% of annual thermal energy needs based on the energy model used in this analysis. Furthermore, annual energy costs could be reduced by 3% and carbon emissions by 11%. Additional analyses are needed to more precisely determine the optimal system for Vail and the authors recommend that future studies include the energy use from base operations in addition to the mountain area considered in this analysis. The additional base area energy load during the summer could potentially make a larger CHP system more viable with subsequent cost and carbon emission savings. Additionally, site-specific resource data such as biomass production and ridge top wind speeds could aid in more definitively eliminating these technologies from consideration.
New Design of a Bimetallic Finned Tube for the Use in Latent Heat Thermal Energy Storage Units
Authors: Urschitz Georg , Brier Jens , Walter Heimo , Mertz Roland , Bleicher Friedrich , Haider Markus
Published: October 2015

The use of finned tubes as enhancement method to increase the heat flow rate into a phase change material, which has in many cases a low thermal conductivity, is a common method. A highly efficient and easy-to-assemble solution for finned heat exchanger tubes is a key component for innovative thermal energy storage systems which play a key-role in electricity production and industrial heat management.

In the present article the results of the investigation for different designs of bimetallic heat exchanger tubes is presented. These tube designs are developed for the use in latent heat thermal energy storage systems (LHTES) at a medium temperature range. For the use in latent heat thermal energy storage systems, the probably high pressure of the heat transfer medium and the high temperature differences between the operating temperature and the ambient temperature are challenging. Therefore, the bimetallic finned heat exchanger tube consists of a steel tube, where the heat transfer fluid flows, and an aluminum tube with longitudinal fins, which should improve the heat transfer to the phase change material. Due to different thermal expansion coefficients, displacements of the tubes are given. To guarantee a high heat transfer rate between the two connected tubes the contact between aluminum and steel plays an important role.

In the present study 4 prototypes (including the new design) were designed, analyzed and compared on the connection strength. Long-term tests for simulating the application in a LHTES were done to determine the creep rupture properties of the compositions. All prototypes were tested successfully; the new design is convinced in many aspects of that challenge and is submitted to the Austrian patent office. Main advantages of the new design are the simple production and assembling compared to other analyzed prototypes. Furthermore, the new design shows the best results under the analyzed operation conditions and the layout of the geometry has a high optimization potential in terms of stresses.
Transient Analysis of an Improved Finned Tube Heat Exchanger for Thermal Energy Storage System
Authors: Walter Heimo , Beck Anton , Hameter Michael
Published: October 2015

The melting and solidification process of sodium nitrate, which is used as energy storage material, is studied in a vertical arranged energy storage device with two different bimetal finned tube designs (with and without transversal fins) for enhancing the heat transfer. The finned tube design consists of a plain steel tube while the material for the longitudinal (axial) fins is aluminum. The investigation analyses the influence of the transversal fins on the charging and discharging process. 3-dimensional transient numerical simulations are performed using the ANSYS Fluent 14.5 software. The results show that every obstruction given by transversal fins reduces the melting and solidification velocity in direction to the outer shell. In the present study also a comparison of the simulation results between 2D and 3D simulation of the melting and solidification behavior of the sodium nitrate is presented.
A Framework for the Development of Technical Requirements for Renewable Energy Systems at a Small-Scale Airport Facility
Authors: Nguyen Troy V. , Ariza Aldo Fabregas , Miller Nicholas W. , Cremer Ismael
Published: October 2015

Airports are key components of the global transportation system and are the subject of continuous sustainability improvements. Promoting clean energy sources and energy-efficient practices can help attain major sustainability goals at airports around the world. Although small airports are greater in number, most of the “sustainability” attention has been given to large airports. Small airports are typically located in rural areas, making them excellent candidates for renewable energy. This paper focuses on the planning and selection of renewable energy systems as a strategic method to reduce energy use and increase electric power reliability at small-scale airport facilities. The target system may use a combination of renewable energy sources to produce electrical power for the on-site facilities. The framework details include methods of energy collection, power production, and energy storage that are environmentally sound. A small airport serving a dual role as a flight training facility was used as case study. In the case study, systems engineering methodology was adapted to the small airport/ renewable energy domain in order to effectively identify stakeholders and elicit user requirements. These, coupled with industrial standards, relevant government regulations, and a priori constraints, are used to derive the initial requirements that serve as the basis for a preliminary design. The proposed framework also contains provisions for an on-site assessment of existing airport energy needs, sources, providers, and location-specific assets and challenges.
Thermal Modeling of a Multi-Cavity Array Receiver Performance for Concentrating Solar Power Generation
Authors: Fleming Austin , Ma Zhiwen , Wendelin Tim , Ban Heng , Folsom Charlie
Published: October 2015

Concentrating solar power (CSP) plants can provide dispatchable power with the thermal energy storage (TES) capability for greater renewable-energy grid penetration. To increase the market competitiveness, CSP technology needs to increase the solar-to-electric efficiency and reduce costs in the areas of solar collection from the heliostat field to the receiver, energy conversion systems, and TES. The current state-of-the-art molten-salt systems have limitations regarding both the potential for cost reduction and improvements in performance. Even with significant improvements in operating performance, these systems face major challenges to satisfy the performance targets, which include high-temperature stability (>650°C), low freezing point (<0°C), and material compatibility with high-temperature metals (>650°C) at a reduced cost. The fluidized-bed CSP (FB-CSP) plant being developed by the National Renewable Energy Laboratory (NREL) has the potential to overcome the above issues with substantially lower cost. The particle receiver is a critical component to enable the FB-CSP system.

This paper introduces the development of an innovative receiver design using the blackbody design mechanism by collecting solar heat with absorber tubes that transfer the radiant heat to flowing particles. The particle and receiver materials can withstand temperatures of >1000°C because the receiver can use low-cost materials, such as ceramics and stainless steel, and the solid particles can be any low-cost, stable materials such as sand or ash for particle containment and TES. The heated particles can be stored in containers for TES or supply heat for power generation. This study investigated the performance of convection, reflection, and infrared (IR) re-radiation losses on the absorber solar receiving side. We developed a flux model to predict the reflection losses from the absorber tubes based on the NREL SolTrace program, and conducted thermal modeling by using the Fluent Software. This paper presents the thermal modeling and results on the receiver performance. The receiver configuration may have broad applications for different heattransfer fluids (HTFs), including gas, liquid, or the solid particle-based system in our receiver development.
Electricity Generation From Large Marine Vessel Engine Jacket Water Heat
Authors: Yuksek Errol L. , Mirmobin Parsa
Published: October 2015

As world trade grows, fuel prices increase, and International Maritime Organization (IMO) emissions requirements tighten, there is more demand for the marine industry to employ innovative means of reducing the fuel consumption and emissions of shipping vessels.

The main engines of large shipping vessels produce a large quantity of low temperature heat, but this valuable heat energy is transferred to cooling systems and rejected to the oceans as waste. At the same time, the electrical needs of shipping vessels are sustained by burning diesel fuel to run generators.

Calnetix Technologies, in partnership with Mitsubishi Heavy Industries, has developed the Hydrocurrent™ 125EJW Organic Rankine Cycle (ORC), a modularized system capable of absorbing the waste heat of main engine jacket water and converting it into grid-quality electric power. By combining this renewable source with the existing non-renewable source (engine gensets) a unique renewable-non-renewable hybrid power system is realized with minimal changes to overall ship power train. This novel hybrid system can be applied to all new and existing ships and allow for further integration into ship systems with available waste heat.

Shipping vessels such as tankers, bulk carriers, and container vessels are typically equipped with a category 3 marine diesel engine for main propulsion. A 30 MW engine, a most common engine size, utilizes 200–300 m3/hr of jacket water regulated to a heated temperature of 80–95 C. When integrated into the jacket water and sea water loops, the ORC can produce up to 125 kW of gross grid-quality electric power. This adds an immense benefit to the ship. To produce the same amount of power, a diesel generator consumes as much as 250 metric tons of diesel fuel per year, generates emissions, and requires significant maintenance.

Calnetix Technologies has leveraged its core technologies to develop the ORC into a reliable, high efficiency, compact and modular design. The turbo-generator or Integrated Power Module (IPM) is a hermetically sealed, high speed radial turbine coupled to a permanent magnet generator supported by magnetic bearings. Power from the IPM is converted by a high efficiency power converter supplying the ship with reliable power. The integrated design of the ORC along with the sophistication of its controls systems ensures essential ship functions are undisturbed under all conditions. The ORC is designed to comply with Nippon Kaiji Kyokai and Lloyd’s Register marine regulations and sea trials are anticipated to take place in 2015.
Deployment of Fuel Cell Electric Buses in Transit Agencies: Hydrogen Fueling Infrastructure Scenarios
Authors: Castillo Analy , Samuelsen Scott , Shaffer Brendan
Published: October 2015

For transit agencies looking to implement Zero Emission Vehicles (ZEV), Fuel Cell Electric Buses (FCEBs) represent an opportunity because of the similar range and refueling times compared to conventional buses, but with improved fuel economy. To assure an environmentally sensitive hydrogen infrastructure that can respond to the wide range of needs and limitations of transit agencies, a systematic evaluation of options is essential. This paper illustrates the systematic evaluation of different hydrogen infrastructure scenarios for a transit agency. The Orange County Transportation Authority (OCTA) in California was selected for the study.

Three different hydrogen infrastructure configurations are evaluated and compared to the existing paradigm of compressed natural gas buses and diesel buses. One additional scenario is analyzed in order to compare feasibility and environmental benefits of FCEBs with Plug-in Electric Buses. Each scenario represents (1) a specific mix and percentage of contribution from the various hydrogen generation technologies (e.g., on-site electrolysis, central SMR, and on-site SMR), (2) defined paths to obtain the corresponding feedstock for each generation process (e.g., biogas, natural gas, renewable energies), (3) detailed hydrogen distribution system (e.g., mix of gaseous/liquid truck delivery), and (4) the spatial allocation of the generation location and fueling locations (e.g., on-site / off-site refueling station) while also accounting for constraints specific to the OCTA bases.

This systematic evaluation provides Well-to-Wheel (WTW) impacts of energy and water consumption, greenhouse gases and criteria pollutant emissions of the processes and infrastructure required to deploy FCEBs and Plug-in Electric Buses at OCTA. In addition, this evaluation includes a detailed analysis of the space requirements and operations modifications that may be necessary, but yet feasible, for the placement of such infrastructure.
An Evaluation of Containment Materials for High Temperature Metal Thermal Storage
Authors: Curran David , Miller Fletcher , Carrington Russell , Hunt Arlon
Published: October 2015

Concentrated solar power (CSP) must decrease its levelized cost of electricity (LCOE) below the DOE SunShot program targets of 6 ¢/kWhe and improve its reliability to enable widespread adoption. Two features of CSP that will decrease LCOE and improve reliability are higher operating temperatures for the power cycle and thermal energy storage (TES). Thermaphase Energy and San Diego State University are developing the Liquid Metal Thermal Energy Storage System (LiMTESS), an innovative TES system based on phase change in Al-Si and Mg-Si alloys that stores thermal energy produced by gas-cooled solar receivers at temperatures above 800 C. Proper containment for Al-Si and Mg-Si alloys is critical for LiMTESS commercialization. Any containment vessel must be simultaneously compatible with the molten alloys and high-temperature oxidizing gases (e.g., air), facilitate heat transfer between the alloys and high-temperature oxidizing gases, and accommodate internal stresses associated with TES operation.

A ceramic-metallic composite material (TCON) and select ceramics such as siliconized silicon carbide (SiSiC) and alumina initially showed promise in meeting these requirements. A series of thermal cycling tests were performed to check the integrity of the containment vessels. TCON produced macroscopic nodules during the thermal cycling that eliminated it from further consideration. On the other hand, SiSiC performed well when exposed to high-temperature, AlSi36, MgSi56, and air. To further evaluate SiSiC as a containment material, the research team conducted multiple thermal cycles with variable temperature profiles, duration of test, and gas environments. Before and after each thermal cycle, the team conducted a mass analysis and performed SEM and EDS analysis on prepared, treated samples. The results confirm SiSiC is a good candidate for a containment vessel.

At this point the research team is evaluating Morcoset, a silicon carbide-based mortar, for creating an air-tight seal for SiSiC. The research team assessed the quality of the seal by using the mortar to seal MgSi56 and conducted thermal cycling tests to compare the mass loss of the system due to Mg vapor escaping the system to that of a controlled system with no alloys sealed. Results confirmed that Mg vapor did not exit the system. There is still more work to do, but preliminary results indicate the Morcoset + SiSiC system is a good containment system for AlSi36/MgSi56. In this paper the results of the long-duration thermal cycling tests as well as electron micrographs of the containment seals and phase change materials are presented.