bluuebunny/crossref_metadata_2025_split huggingface dataset:
Short‐term adaptation and chronic cardiac remodelling to high altitude in lowlander natives and Himalayan Sherpa
Authors: Stembridge Mike , Ainslie Philip N. , Shave Rob 
Published: October 2014

New Findings
What is the topic of this review?
At high altitude, the cardiovascular system must adapt in order to meet the metabolic demand for oxygen. This review summarizes recent findings relating to short‐term and life‐long cardiac adaptation to high altitude in the context of exercise capacity.
What advances does it highlight?
Both Sherpa and lowlanders exhibit smaller left ventricular volumes at high altitude; however, myocardial relaxation, as evidenced by diastolic untwist, is reduced only in Sherpa, indicating that short‐term hypoxia does not impair diastolic relaxation. Potential remodelling of systolic function, as evidenced by lower left ventricular systolic twist in Sherpa, may facilitate the requisite sea‐level mechanical reserve required during exercise, although this remains to be confirmed.
Both short‐term and life‐long high‐altitude exposure challenge the cardiovascular system to meet the metabolic demand for O2 in a hypoxic environment. As the demand for O2 delivery increases during exercise, the circulatory component of oxygen transport is placed under additional stress. Acute adaptation and chronic remodelling of cardiac structure and function may occur to facilitate O2 delivery in lowlanders during sojourn to high altitude and in permanent highland residents. However, our understanding of cardiac structural and functional adaption in Sherpa remains confined to a higher maximal heart rate, lower pulmonary vascular resistance and no differences in resting cardiac output. Ventricular form and function are intrinsically linked through the left ventricular (LV) mechanics that facilitate efficient ejection, minimize myofibre stress during contraction and aid diastolic recoil. Recent examination of LV mechanics has allowed detailed insight into fundamental cardiac adaptation in high‐altitude Sherpa. In this symposium report, we review recent advances in our understanding of LV function in both lowlanders and Sherpa at rest and discuss the potential consequences for exercise capacity. Collectively, data indicate chronic structural ventricular adaptation, with adult Sherpa having smaller absolute and relative LV size. Consistent with structural remodelling, cardiac mechanics also differ in Sherpa when compared with lowlanders at high altitude. These differences are characterized by a reduction in resting systolic deformation and slower diastolic untwisting, a surrogate of relaxation. These changes may reflect a functional cardiac adaptation that affords Sherpa the same mechanical reserve seen in lowlanders at sea level, which is absent when they ascend to high altitude.
Modeling Building HVAC Energy Consumption During an Extreme Heat Event in a Dense Urban Environment
Authors: Tibana Yehisson , Gutierrez Estatio , Marte Sashary , Gonzalez J. E. 
Published: October 2014

Dense urban environments are exposed to the combined effects of rising global temperatures and urban heat islands, a thermal gradient between the urban centers and the less urbanized surroundings suburbs. This combination is resulting in increasing trends of energy consumption in cities, associated mostly to air conditioning to maintain indoor human comfort conditions. The energy demand is further magnified during extreme heat events to a point where the electrical grid may be at risk. Given the anticipated increased frequency of extreme heat events for the future, it is imperative to develop methodologies to quantify energy demands from buildings during extreme heat events.
The purpose of this study is to precisely quantify thermal loads of buildings located in the very dense urban environment of New York City under an extreme heat event that took place in the summer of 2010 (July 4–8). Two approaches were used to quantify thermal loads of buildings for these conditions; a single building energy model (SBEM), such as the US Department of Energy eQUEST and EnergyPlus™, and an urbanized weather forecasting model (uWRF) coupled to a building energy model. The SBEM was driven by Typical Meteorological Year (TMY) weather file and by a customized weather file built from uWRF’s weather data for the specific days of the heat wave. A series of simulations were conducted with both SBEM software to model building energy consumption data due to air conditioning for two locations in Uptown and Midtown Manhattan, NY, which represented a low density and a high density building area within the city. Assumptions were made regarding the building’s floor plans and operation schedule to simplify the model and provide a close comparison to uWRF.
Results of the ensemble of SBEM indicate there was an increase in energy consumption during the July 2010 heat-wave when compared with the central park TMY case. The uptown location consumed 137% more energy during the heat wave event, while the midtown location showed an increased in energy consumption of 125% when compared to a typical July three day period, reaching total loads of close to 9812 kWh for a 20 m height building. Comparison of the results directly from uWRF for the energy consumption for same locations, indicate that for the midtown location both SBEMs underestimated the total energy consumption within a factor of three. This may be due to the fact that uWRF energy model takes into account urban microclimate parameters such as anthropogenic sources and waste heat interactions between surrounding buildings.
Magnesium Hydride Slurry — A Better Answer to Hydrogen Storage
Authors: McClaine Andrew W. , Brown Kenneth , Bowen David D. G. 
Published: October 2014

Hydrogen has many properties that make it an attractive energy storage medium for a sustainable future. But hydrogen is also difficult to store safely and cheaply. By storing hydrogen in an oil-based slurry with powdered magnesium hydride, cheap and safe hydrogen storage can be realized. This paper describes the characteristics and benefits of cycling hydrogen in and out of magnesium hydride slurry.
Based on our experience with magnesium hydride slurry, we have performed a study to evaluate the cost effectiveness of applying bulk hydrogen storage, using magnesium hydride slurry, in a baseload wind power system that we will also discuss. This study concludes that a 150 MW baseload wind power system would produce an Internal Rate of Return (IRR) of 10% with an electric price of $0.088/kWh. The costs and performance characteristics of this power plant are described.
A Comparison Between the Monte Carlo Ray Trace and the FLUENT Discrete Ordinates Methods for Treating Solar Input to a Particle Receiver
Authors: Mecit Ahmet Murat , Miller Fletcher 
Published: October 2014

A new type of high temperature solar receiver for Brayton Cycle power towers is being designed and built in the Combustion and Solar Energy Laboratory at San Diego State University under a DOE Sunshot Award. The Small Particle Solar Receiver is a pressurized vessel with a window to admit concentrated solar radiation that utilizes a gas-particle suspension for absorption and heat transfer. As the particles absorb the radiation that enters the receiver through the window, the carrier fluid (air in this case) heats which oxidizes the particles and the flow leaves the receiver as a clear gas stream. After passing through an in-line combustor if needed, this hot gas is used to power a turbine to generate electricity.
The numerical modelling of the receiver is broken into three main pieces: Monte Carlo Ray Trace (MCRT) method (written in FORTRAN), ANSYS Fluent (CFD), and the User Defined function (written in C code) for oxidation. Each piece has its advantages, disadvantages, and limitations and the three pieces are coupled to finalize the calculation. While we have successfully demonstrated this approach to obtaining the velocity and temperature fields, one big challenge to this method is that the definition of the geometry is a time consuming programming task when using MCRT. On the other hand, arbitrary geometries can be easily modelled by Computational Fluid Dynamics (CFD) codes such as FLUENT.
The goal of this study is to limit the use of MCRT method to determining the appropriate input boundary condition on the outside of the window of the receiver and to use the built-in Discrete Ordinates (DO) method for all the radiation internal to the receiver and leaving the receiver due to emission. To reach the goal, this paper focuses on the DO method implemented within FLUENT. An earlier study on this subject is based and advanced. Appropriate radiation input for the DO method is extensively discussed. MIRVAL is used to simulate the heliostat field and VEGAS is used to simulate a lab-scale solar simulator; both of these codes utilize the MCRT method and provide intensity information on a surface. Output from these codes is discretized into DO parameters allowing the solution to proceed in FLUENT. Suitable benchmarks in FLUENT are used in a cylindrical geometry representing the receiver for the comparison and validation. This method will allow FLUENT to be used for a variety of problems involving concentrated solar energy.
Feasibility and Economic Evaluation of Applying Two Alternative Energy (R.D.F. and T.D.F) in Cement Industries in Iran
Authors: Nejati Vahid , Roknizadeh Jalil 
Published: October 2014

In 2012, approximately 3700 million tons of cement is produced all around the world. Iran by producing 65 million tons cement in 2012 is ranked in fifth. Production process of the cement requires a huge amount of energy and it is approximated that 25% to 35% (based on efficiency of factories) of total costs in cement industries belong to required heat energy in production process. To produce 65 million tons of cement in Iran, about 56×1012 kcal of heat energy is consumed. Thus applying the new and cheep sources of energy could play an important role in reducing energy costs. On the other hand one of the important environmental problems is the absolutely huge amount of used tire of vehicles and the Municipal Solid Waste (MSW) and they should be appropriately destroyed. As a result they can easily change to Tire-Derived Fuel (TDF) and Refuse-Derived Fuel (RDF) to provide the required heat energy in cement industries.
In this study the available amount of RDF and TDF for cement industry are estimated. The evaluation results show that in Iran TDF can only provide about 1.77 percent of this need. Also using RDF, whose production has large potential in Iran, can cover about 27.96 percent. It is concluded that reduction of 29.73 percent of fossil fuel consumption in cement industries stem from applying both of these fuels simultaneously, leading to gas saving about two billion cubic meters per year. It is determined that the export value of such volume of gas is equal to one billion and ten million dollars with current gas price. However there is no tendency for using the alternative energy by cement factories because of low price of oil and natural gas inside Iran than global rate. In fact at the moment applying RDF and TDF doesn’t have any benefit for cement factories.
The purpose of this paper is to evaluate the effects of using alternative fuels in the cement industry in Iran and to show that for persuading and encouraging the cement factories to apply RDF and TDF, instead of increasing the energy prices, the revenue from fuel savings in global rate should be paid directly to cement industries.
Thermal Stratification in Spherical Tanks
Authors: Khan Fahad , Savilonis Brian J. 
Published: October 2014

Spherical tanks have the potential for cost reduction in sensible thermal energy storage (TES) systems, by using less tank building material and insulation.
The current CFD study compares the Thermal Efficiency (TE) of a thermocline storage system in a spherical tank to a cylindrical tank of the same volume. A parametric study is then performed on a spherical tank during the discharge process to determine the flow parameters that govern the thermocline formation and entrainment. The following parameters are used: tank diameter to inlet diameter ratio D/d = 10, inlet velocity (0.02–0.1 m/s), and ΔT (10–70° C), leading to an inlet Froude number (0.4–3), inlet Reynolds number (500–7500), and tank Richardson number (2–100).
The results show a significant correlation between the inlet Reynolds and inlet Froude numbers, and the tank TE, in addition to a weak correlation between the tank Richardson number, based on the tank diameter, and the tank TE. The parametric study also shows a maximum tank TE at a Froude number equal to 0.5, and a proportional decrease of TE as the Reynolds number increases.
Empirically Driven Computer Simulations of Solar Thermal Systems for Space Heating and Domestic Hot Water
Authors: Robbins Curtis , Goldade Travis , Hoekman S. Kent , Jacobson Roger , Turner Robert 
Published: October 2014

The Desert Research Institute (DRI) has developed a Renewable Energy Deployment and Display Facility (REDD) which utilizes solar and wind to create a net zero energy residence for research, education, and outreach. The facility is a demonstration of the integration of many renewable energy technologies into a residential setting such that technology developers can show proof-of-concept, students and trade workers can get hands-on experience, and public organizations can see renewable energy components implemented into a residential setting. A major technological aspect of the facility is the use of solar thermal energy to provide space heating, Domestic Hot Water (DHW), and solar cooling. Data are monitored from three separate solar thermal systems, each with their own hot water storage, to evaluate optimized utilization of solar thermal energy into residential applications.
The three solar thermal systems differ in their working fluids. System 1 uses a conventional mixture of glycol and water in 200 ft2 of ground mounted collector area, System 2 uses DHW in 210 ft2 of roof mounted collector area, and System 3 uses air in a 578 ft2 collector built into the roof. Each system is configured to be used for space heating and DHW. Systems 1 and 2 are built into the HVAC system of the 1200 ft2 house, and System 3 is built into the HVAC system of the 600 ft2 detached workshop. Data collected from each system provide the basis for year-long energy and economic simulations using TRNSYS for comparison. The results from the simulations are used to demonstrate the effectiveness of site-built solar air collectors, which have the advantage of using conventional materials, and avoid the issues of liquid collectors associated with boiling and freezing. This paper describes the experimental setup of the solar thermal systems, how the data are used as inputs to the computer simulations, and the configuration of the computer simulations.
The REDD Facility, as well as the use of TRNSYS will continue to be used by DRI researchers to investigate not only the most feasible integration of components for a solar thermal residential system, but also as a tool to properly size and implement solar thermal systems.
Computer-Based Management of Mirror-Washing in Utility-Scale Solar Thermal Plants
Authors: Alon Lital , Ravikovich Gregory , Mandelbrod Matan , Eilat Udi , Schop Zafrir , Tamari Dror 
Published: October 2014

BrightSource solar power plants consist of fields of tens of thousands of mirrors, spread across kilometers of open areas. These huge mirrors are in constant motion, reflecting the sun’s rays on to the solar thermal collector. Maintaining high reflectivity of the mirrors is essential for the solar field’s performance, a task that becomes complex when expanded to encompass the solar field’s features. The solution for mirror cleaning must be efficient, cost-effective, time-saving, and easy to maintain for dozens of years.
BrightSource has designed and constructed a system of GPS-based mirror washing machines (MWMs) that are controlled and managed by end-to-end software. The system generates optimized cleaning tasks, positions the mirrors, and efficiently controls the navigation and state of the MWMs with their 25-meter-long extendable cranes. All of these actions together provide an optimal mirror cleaning solution.
This article describes the BrightSource cleaning control technology, for example, in the Ivanpah project, the world’s largest solar thermal facility. The Ivanpah solar field includes 173,500 heliostats divided among three solar fields. Each heliostat holds two mirrors of approximately 2.5 × 3.5 meters, all of which require periodic cleaning.
Specifically, this article addresses issues such as the following:
• The mirror washing machine (MWM) types: truck and tractor-based, and their differing usage in the solar field
• Designation and choice of the cleaning area
• Estimation of the stopping points in the designated area, and association of the mirrors to clean from each stopping point
• Cleaning time optimization: stopping point density, order in which to clean heliostats, and heliostat position during cleaning
• Heliostat positioning: opening clear corridors through which the MWM can travel, and setting heliostats in cleaning orientations
• Receiving and responding to callback messages from the MWMs, such as cleaning progress and machine faults
• Working in the real world: resources shared with the power plant, and recovery from system faults
Time Instant Optimization of a Heliostat Field Using a Heuristic Algorithm
Authors: Atif Maimoon , Al-Sulaiman Fahad A. 
Published: October 2014

Solar central receiver systems are viewed as one of the most promising concentrated solar power (CSP) technologies for power production, in which solar radiation is concentrated through large mirrors (heliostats) onto a central receiver. This is due to the fact that very high temperatures can be reached at the receiver and thus higher thermal efficiency can be achieved compared with other CSP technologies. Heliostat field layout optimization is an essential task for any solar central receiver system.
In this paper, a heuristic algorithm, i.e. the differential evolution (DE), was employed to perform efficient optimization of the conventional radial staggered heliostat field layout using MATLAB. The model calculates all the required optical performance parameters at every step of the optimization process for each heliostat and consequently more reliable results are obtained as compared with many other optimization methods. Two cases were considered: one with single variable optimization and the other with multi-variable optimization. For the first case, the azimuthal spacing between the adjacent heliostats or the radial distance between the rows of heliostats were optimized independently and for the second case both of these variables were optimized simultaneously. Both cases were examined for high sun altitude angle and low altitude angle and a comparison study was performed between them to check their effect on the heliostat field efficiency. Finally, it was noted that varying the radial distance between the rows of the heliostats yields slightly better efficiency as compared with when optimizing the azimuthal spacing.
Development of High Temperature, Corrosion Resistant Sensors for Concentrating Solar Power Systems
Authors: Usrey Michael W. , Liu Yiping , Anderson Mark , Lubbers Jon , Knowles Brady , Harsh Kevin , Pilant Evan 
Published: October 2014

Solar power is a sustainable resource which can reduce the power generated by fossil fuels, lowering greenhouse gas emissions and increasing energy independence. The U.S. Department of Energy’s SunShot Initiative has set goals to increase the efficiency of concentrating solar power (CSP) systems. One SunShot effort to help CSP systems exceed 50% efficiency is to make use of high-temperature heat transfer fluids (HTFs) and thermal energy storage (TES) fluids that can increase the temperature of the power cycle up to 1300°C.
Sporian has successfully developed high-temperature operable pressure, temperature, thermal flux, strain, and flow sensors for gas path measurements in high-temperature turbine engines. These sensors are based on a combination of polymer derived ceramic (PDC) sensors, advanced high-temperature packaging, and integrated electronics. The overall objective is the beneficial application of these sensors to CSP systems.
Through collaboration with CSP industry stakeholders, Sporian has established a full picture of operational, interface, and usage requirements for trough, tower, and dish CSP architectures. In general, sensors should have accurate measurement, good reliability, reasonable cost, and ease of replacement or repair. Sensors in contact with hot salt HTF and TES fluids will experience temperature cycling on a daily basis, and parts of the system may be drained routinely. Some of the major challenges to high-temperature CSP implementation include molten salt corrosion and flow erosion of the sensors. Potential high-temperature sensor types that have been identified as of interest for CSP HTF/TES applications include temperature, pressure, flow, and level sensors.
Candidate solar salts include nitrate, carbonate, and chloride, with different application temperatures ranging from 550°C-900°C. Functional ceramics were soaked for 500 hours in molten nitrate, carbonate, and chloride salts, showing excellent corrosion resistance in chloride salts and good resistance in nitrate salts. The demonstration of functional ceramics in relevant HTFs laid the foundation for full prototype sensor and packaging demonstration.
Sporian has developed a packaging approach for ceramic-based sensors in various harsh gaseous environments at temperatures up to 1400°C, but several aspects of that packaging are not compatible with corrosive and electrically conductive HTFs. In addition to consulting published literature, a 300 hour soak test in molten chloride salt allowed the authors to identify suitable structural metals and ceramics.
Based on discussions with stakeholders, molten salt corrosion testing and room-temperature water flow testing, suitable for CSP sensor/packaging concepts were identified for future development, and initial prototypes have been built and tested.