bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance Characteristics of Philippine Hydrous Ethanol-Gasoline Blends: Preliminary Findings
Authors: Yu John Luis , Quiros Edwin N. 
Published: December 2019

Abstract
To reduce dependence on imported fossil fuels and develop indigenous biofuels, the Philippines enacted the Biofuels Act of 2006 which currently mandates a 10% by volume blend of 99.6% anhydrous bio-ethanol for commercially sold Unleaded and Premium gasolines. To urge a regulation review of the anhydrous requirement and examine the suitability for automotive use of hydrous bioethanol (HBE) blends, preliminary engine dynamometer tests at 1400–4400 rpm were conducted to measure specific fuel consumption (SFC) and power. In this study, HBE (95 % ethanol and 5% water by volume) produced from sweet sorghum using a locally-developed process, was blended volumetrically with three base gasoline fuels — Neat, Unleaded, and Premium. The four HBE blends tested were 10% and 20% with Neat gasoline, 20% with Unleaded gasoline, and 20% with Premium gasoline.
For blends with Neat gasoline, the SFC of the 10%HBE blend was comparable with to slightly higher than Neat gasoline. The SFC of the 20%HBE blend was comparable with Neat gasoline up to 2800 rpm and lower beyond this speed thus being better overall than the 10%HBE blend. Compared to their respective commercial base fuels, the HBE-Unleaded blend showed lower SFC while the HBE-Premium blend yielded slightly higher SFC over most of the engine speed range. Between commercial fuel blends, the HBE-Unleaded blend gave better SFC than the HBE-Premium blend. Power was practically similar for the fuels tested. No engine operational problems and fuel blend phase separation were encountered during the tests. This preliminary study indicated the suitability of and possible optimum hydrous bio-ethanol blends for automotive use under Philippine conditions.
Characterization of Particle and Heat Losses From Falling Particle Receivers
Authors: Ho Clifford K. , Kinahan Sean , Ortega Jesus D. , Vorobieff Peter , Mammoli Andrea , Martins Vanderlei 
Published: December 2019

Abstract
Camera-based imaging methods were evaluated to quantify both particle and convective heat losses from the aperture of a high-temperature particle receiver. A bench-scale model of a field-tested on-sun particle receiver was built, and particle velocities and temperatures were recorded using the small-scale model. Particles heated to over 700 °C in a furnace were released from a slot aperture and allowed to fall through a region that was imaged by the cameras. Particle-image, particle-tracking, and image-correlation velocimetry methods were compared against one another to determine the best method to obtain particle velocities. A high-speed infrared camera was used to evaluate particle temperatures, and a model was developed to determine particle and convective heat losses. In addition, particle sampling instruments were deployed during on-sun field tests of the particle receiver to determine if small particles were being generated that can pose an inhalation hazard. Results showed that while there were some recordable emissions during the tests, the measured particle concentrations were much lower than the acceptable health standard of 15 mg/m3. Additional bench-scale tests were performed to quantify the formation of particles during continuous shaking and dropping of the particles. Continuous formation of small particles in two size ranges (&lt; ∼1 microns and between ∼8–10 microns) were observed due to de-agglomeration and mechanical fracturing, respectively, during particle collisions.
Robust Control of Hydrogen Flow for an Automotive Fuel Cell System via Model Reference Adaptive Control
Authors: Hwang Janghwan , Yu Sangseok 
Published: December 2019

Abstract
Efficient hydrogen flow control is of great importance to ensure the reliable operation of an automotive fuel cell system because it is closely associated with the safety and the economic efficiency. In this study, an effective hydrogen flow control algorithm for hydrogen excess ratio control is addressed by pointing out the recovery speed and overshoot response. Unlike previous studies on the hydrogen management systems of an automotive fuel cell, this study presents an analytic hydrogen tank model which can present the characteristics of the discharge and charge of hydrogen from a type 4 hydrogen tank. To this end, a mode reference adaptive control (MRAC) based on proportional-integral (PI) control is introduced, to ensure robust hydrogen flow during the dynamic operation of fuel cell system. The MRAC was compared with the nominal PI control and PWM control in the hydrogen management system of an automotive fuel cell operating within normal conditions, under steady-state responses and transient. Based on these result, it can further demonstrate that the MRAC algorithm shows better recovery speed and tracking performance than the nominal PI, and PWM control algorithm with respect to the transient behaviors.
Optimization of Storage Bin Geometry for High Temperature Particle-Based CSP Systems
Authors: Sment Jeremy , Albrecht Kevin , Christian Joshua , Ho Clifford K. 
Published: December 2019

Abstract
Solid particle receivers provide an opportunity to run concentrating solar tower receivers at higher temperatures and increased overall system efficiencies. The design of the bins used for storing and managing the flow of particles creates engineering challenges in minimizing thermomechanical stress and heat loss. An optimization study of mechanical stress and heat loss was performed at the National Solar Thermal Test Facility at Sandia National Laboratories to determine the geometry of the hot particle storage hopper for a 1 MWt pilot plant facility. Modeling of heat loss was performed on hopper designs with a range of geometric parameters with the goal of providing uniform mass flow of bulk solids with no clogging, minimizing heat loss, and reducing thermomechanical stresses. The heat loss calculation included an analysis of the particle temperatures using a thermal resistance network that included the insulation and hopper. A plot of the total heat loss as a function of geometry and required thicknesses to accommodate thermomechanical stresses revealed suitable designs. In addition to the geometries related to flow type and mechanical stress, this study characterized flow related properties of CARBO HSP 40/70 and Accucast ID50-K in contact with refractory insulation. This insulation internally lines the hopper to prevent heat loss and allow for low cost structural materials to be used for bin construction. The wall friction angle, effective angle of friction, and cohesive strength of the bulk solid were variables that were determined from empirical analysis of the particles at temperatures up to 600°C.
Comparison and Implementation of Thermally Massive Wall and Roof Models for Use in Simplified Building Energy Models
Authors: Fernandez Christopher , Jeter Sheldon 
Published: December 2019

Abstract
Although contemporary and complex building energy models such as EnergyPlus are highly advanced and predictive, a simplified building energy model has many advantages and applications. Chief among the advantages are adaptability to the measured response of a building and conciseness in computer implementation. Important applications will include automated fault detection. One of the most important aspects of a successful building energy model is the ability to accurately account for the heat capacity of the structure, especially the envelope. As part of the development of a simplified physics-based building energy model, a variety of roof and wall models were considered. Three different generic models were considered for opaque walls and roofs (1) an analytical model with closed-form solution, (2) a time-series solution using the ASHRAE transfer function method, and (3) a lumped capacity model with various numbers of capacitive nodes. This paper will describe an investigation of various simplified models for the transient conduction through building walls. Specifically, how different kinds of wall constructions and materials can change when the conduction load passes through the wall and when it impacts the HVAC system. Understanding how the physics of dynamic envelope loading can change how much energy a building uses for heating or cooling and when room conditioning loads occur is vital for energy savings and proper modeling.
Effect of Quartz Aperture Covers on the Fluid Dynamics and Thermal Efficiency of Falling Particle Receivers
Authors: Yue Lindsey , Mills Brantley , Ho Clifford K. 
Published: December 2019

Abstract
Falling particle receivers are an emerging technology for use in concentrating solar power systems. In this work, quartz tubes cut in half to form tube shells (referred to as quartz half-shells) are investigated for use as a full or partial aperture cover to reduce radiative and advective losses from the receiver. A receiver subdomain and surrounding air volume are modeled using ANSYS® Fluent®. The model is used to simulate fluid dynamics and heat transfer for the following cases: (1) open aperture, (2) aperture fully covered by quartz half-shells, and (3) aperture partially covered by quartz half-shells. We compare the percentage of total incident solar power lost due to conduction through the receiver walls, advective losses through the aperture, and radiation exiting out of the aperture. Contrary to expected outcomes, simulation results using the simplified receiver subdomain show that quartz aperture covers can increase radiative losses and, in the partially covered case, also increase advective losses. These increased heat losses are driven by elevated quartz half-shell temperatures and have the potential to be mitigated by active cooling and/or material selection.
Optical Performance Modeling and Analysis of a Tensile Ganged Heliostat Concept
Authors: Yellowhair Julius , Andraka Charles E. , Armijo Kenneth M. , Ortega Jesus D. , Clair Jim 
Published: December 2019

Abstract
Designs of conventional heliostats have been varied to reduce cost, improve optical performance or both. In one case, reflective mirror area on heliostats has been increased with the goal of reducing the number of pedestals and drives and consequently reducing the cost on those components. The larger reflective areas, however, increase torques due to larger mirror weights and wind loads. Higher cost heavy-duty motors and drives must be used, which negatively impact any economic gains. To improve on optical performance, the opposite may be true where the mirror reflective areas are reduced for better control of the heliostat pointing and tracking. For smaller heliostats, gravity and wind loads are reduced, but many more heliostats must be added to provide sufficient solar flux to the receiver. For conventional heliostats, there seems to be no clear cost advantage of one heliostat design over other designs.
The advantage of ganged heliostats is the pedestal and tracking motors are shared between multiple heliostats, thus can significantly reduce the cost on those components. In this paper, a new concept of cable-suspended tensile ganged heliostats is introduced, preliminary analysis is performed for optical performance and incorporated into a 10 MW conceptual power tower plant where it was compared to the performance of a baseline plant with a conventional radially staggered heliostat field. The baseline plant uses conventional heliostats and the layout optimized in System Advisor Model (SAM) tool. The ganged heliostats are suspended on two guide cables. The cables are attached to rotations arms which are anchored to end posts. The layout was optimized offline and then transferred to SAM for performance evaluation.
In the initial modeling of the tensile ganged heliostats for a 10 MW power tower plant, equal heliostat spacing along the guide cables was assumed, which as suspected leads to high shading and blocking losses. The goal was then to optimize the heliostat spacing such that annual shading and blocking losses are minimized. After adjusting the spacing on tensile ganged heliostats for minimal blocking losses, the annual block/shading efficiency was greater than 90% and annual optical efficiency of the field became comparable to the conventional field at slightly above 60%.
On-Sun Tracking Evaluation of a Small-Scale Tensile Ganged Heliostat Prototype
Authors: Yellowhair Julius , Armijo Kenneth M. , Ortega Jesus D. , Clair Jim 
Published: December 2019

Abstract
Various ganged heliostat concepts have been proposed in the past. The attractive aspect of ganged heliostat concepts is multiple heliostats are grouped so that pedestals, tracking drives, and other components can be shared, thus reducing the number of components. The reduction in the number of components is thought to significantly reduce cost. However, since the drives and tracking mechanisms are shared, accurate on-sun tracking of grouped heliostats becomes challenging because the angular degrees-of-freedom are now limited for the multiple number of combined heliostats. In this paper, the preliminary evaluation of the on-sun tracking of a novel tensile-based cable suspended ganged heliostat concept is provided. In this concept, multiple heliostats are attached to two guide cables. The cables are attached to rotation spreader arms which are anchored to end posts on two ends. The guide cables form a catenary which makes tracking on-sun interesting and challenging. Tracking is performed by rotating the end plates that the two cables are attached to and rotating the individual heliostats in one axis. An additional degree-of-freedom can be added by differentially tensioning the two cables, but this may be challenging to do in practice. Manual on-sun tracking was demonstrated on small-scale prototypes. The rotation arms were coarsely controlled with linear actuators, and the individual heliostats were hand-adjusted in local pitch angle and locked in place with set screws. The coarse angle adjustments showed the tracking accuracy was 3–4 milli-radians. However, with better angle control mechanisms the tracking accuracy can be drastically improved. In this paper, we provide tracking data that was collected for a day, which showed feasibility for automated on-sun tracking. The next steps are to implement better angle control mechanisms and develop tracking algorithms so that the ganged heliostats can automatically track.
Green Diesel From Microalgae
Authors: Costa Iago G. , Vargas José V. C. , Balmant Wellington , Z. Filho Arion , Ramos Luiz P. , Taher Dhyogo M. , Mariano André B. 
Published: December 2019

Abstract
This work developed a process of extraction of crude oil from microalgae for production of hydrocarbon based fuel (green diesel). The microalgae Tetradesmus obliquus were cultivated in 12 m3 compact photobioreactors (FBRS) for 15 days using biodigester effluent as nutrients. Microalgae oil was obtained from the dry biomass through hot extraction with organic solvents (hexane and ethanol). After extraction the solvents were recovered from the sample using evaporation methods. After solvent recovery, the results showed that with pure ethanol, only 1.7% w/w crude oil was obtained, whereas with a mixture of hexane and ethanol the yield was 11.1% w/w. Fractional distillation was used as purification methods of the compounds in order to separate the nonsterifiable portion. The first process (pure hexane) after purification delivered 0.4% w/w, and the second process (hexane and ethanol) yielded 6.3% w/w. In addition, the sample was characterized using gas chromatography coupled to a mass spectrometer (GC-MS). An average of 70.6% w/w hydrocarbons ranging from C11 to C22 was found in the first experimental condition, and the main compounds were undecane (8.1% w/w) and pentadecane (10.62% w/w). For the second experimental condition, about 79.6% w/w hydrocarbons were found that varied from C13 to C23 and the main compounds were pentadecane (13.5% w/w) and heptadecane (11.28% w/w). The lower heating value of the purified microalgae oil was measured as 42,464.6 kJ·kg−1, whereas petroleum-based diesel has a lower heating value of 42,500.2 kJ·kg−1. In sum, green diesel from microalgae was proven to have potential to be a concrete alternative to replace diesel from the technical point of view.
Evaluating the Energy Savings From Community Scale Solar Water Heating in Los Angeles County: Residential Case Studies
Authors: Cudd Robert , Anderson Kevin , Yassine Wael 
Published: December 2019

Abstract
Estimation of Energy Savings from Community Scale Solar Water Heating in Los Angeles County explores the extent to which community scale solar water heating systems, designed for residential structures in Los Angeles County and constructed from currently available technology, can displace natural gas for domestic water heating through a series of case studies. The effects of policy, urban form, and building characteristics on the performance of solar water heating systems, as well as community scale solar water heating’s potential to reduce emissions from the residential housing sector, are discussed herein. Three public and three private residential developments were selected as case studies for community scale solar water heating, with numbers of units and residents ranging from the tens to hundreds. These six cases were draw from the pool of approximately 19,000 “energy communities” in Los Angeles County, i.e. residential developments where the installation and operation of community scale solar water heating systems is broadly feasible. The six properties were also chosen to represent a cross-section housing stock and development patterns common in Los Angeles County, and different levels of suitability for solar water heating. The performance of and energy savings from solar water heating systems on each of these properties is then evaluated using the National Renewable Energy Laboratory’s System Advisor Model (NREL SAM). The results of the system simulations reveal how building characteristics and hot water demand affect the performance of community scale solar water heating systems. The case study sites’ system simulations show that residential developments with community scale solar water heating systems reach an average solar fraction of 50%. The results of the case studies indicate that community scale solar water heating is viable as an emissions reduction technology for the residential building sector in Mediterranean climates. However, side-by-side comparison with solar PV systems and other water heating technologies (such as grid-connected heat pumps) is necessary to determine optimality in terms of cost, emissions reduction, and thermal efficiency) in specific contexts.
Numerical Investigations on the Flow Past an Inclined Thin Square Plate at Re = 300
Authors: Zhao Yakun , Tian Xinliang , Wu Xia , Zhang Xiantao , Li Xin 
Published: December 2019

Abstract
Direct numerical simulations are performed for the flow past an inclined square plate. The side length-thickness ratio of the plate is selected as 50, representing a reasonably thin plate. Various incidence angles of the plate with respect to the flow are considered from 0° to 75°, where 0° refers to the condition in which the flow is normal to the plate. The Reynolds number (Re) based on the flow velocity and the side length in the streamwise direction of the plate is up to 300. The hydrodynamic characteristics, including the force coefficients, the three-dimensional vortical structures and vortex shedding process, are presented. The effects of incidence angle on the wake transition are also discussed. It is observed that as the incidence angle increases, the flow firstly changes from a chaotic state to a periodic state and finally returns to chaos again at high incidence angles.
Poly-Generation Using Biogas From Agricultural Wastes
Authors: Welch Michael 
Published: December 2019

Abstract
Across the world, many people, especially in rural communities, still lack access to secure, affordable electricity supplies. Many countries also lack or have under-developed indigenous fossil fuel resources, or rely on environmentally unfriendly fuels such as coal or Heavy Fuel Oil. Many under-developed regions though are blessed with considerable agricultural resources, and well-suited to Distributed Power Generation, where smaller decentralized power plants are located close to the actual energy consumers. Distributed Power eliminates the need for an electricity transmission grid, or reduces the investment costs necessary to strengthen the grid system, and helps ensure stable, secure electricity to support local economic growth. Agricultural wastes can be used as a locally available feedstock to produce the energy required to electrify regions and stimulate economic growth.
This paper examines the benefits of applying Poly-generation — the production of multiple products at a single location — and examines a proposed bio-refinery scheme to produce ethanol from agricultural waste. The ethanol production process produces a waste biogas, which can then be used in a high efficiency Cogeneration (or Combined Heat and Power) plant as a fuel for gas turbines to generate electricity and steam (heat), not just for the bio-refinery but also local industry and businesses. By creating a high value product (ethanol) along with a free fuel, the bio-refinery acts as an anchor plant to provide reliable, affordable electricity to the local community. As well as providing economic benefits, such a concept has multiple environmental benefits as regions and nations try to combine growth in energy demand with reduction in global greenhouse gas emissions: agricultural residues that would otherwise have decayed emitting methane and CO2 into the atmosphere are used to create a high value product in ethanol, while using the biogas as a fuel displaces combustion of fossil fuels, reducing both combustion emissions and those associated with transportation of the fuel to the point of use.
Revenue Maximization for a Groundwater Desalination Plant and Small Modular Reactor Coupling
Authors: Worsham Elizabeth K. , Thomas Alexander D. , Terry Stephen D. 
Published: December 2019

Abstract
Desalination is becoming a popular and necessary process for producing fresh water in deserts and areas across the word affected by drought. Small Modular Reactor (SMR) technology is attractive for this application because it cogenerates steam and electricity to run multiple desalination processes at once. Multi-Effect Distillation (MED) technology requires steam to evaporate fresh water, while Reverse Osmosis (RO) only requires electricity for desalination. While RO typically produces fresh water more efficiently than MED, condensate from the evaporators can be flashed and sent to an absorption chiller to produce chilled water for space cooling. This study uses a 6-effect backward feed evaporator model to analyze revenues and savings from total freshwater and chilled water produced and determine the steam pressure from the SMR and loading schedule to produce maximum revenue for the specified desalination facility. Three loading schedules were chosen for this study: base loading, day/night loading, and diurnal demand loading, and revenues were calculated by closely matching a demand of 50,000 people. Day/night loading resulted in significantly more revenue and chilled water production than the other two schedules. The coupling of RO and MED systems to a small modular reactor could result in increased revenue for a desalination plant while meeting the freshwater demands of a community.