bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance Evaluation and Outlook of Utility-Scale Linear Fresnel Technology
Authors: Zhu Guangdong , Wagner Mike , Wendelin Tim , Kutscher Chuck 
Published: December 2013

As one of the viable concentrating solar power (CSP) technologies, linear Fresnel collectors differ from parabolic troughs by virtue of their low-profile mirror arrays and fixed receiver assemblies. This technology is capable of achieving high concentration ratios and so is applicable to high-temperature solar power plant designs. In addition, its low wind profile and linear nature lead to low system and operation and maintenance (O&M) costs.
In this report two linear Fresnel solar plant configurations, namely a direct steam generation (DSG) system and a direct high-temperature molten-salt plant, are examined via a levelized cost of electricity (LCOE) analysis. By treating LCOE as a function of the annual investment energy return (IER, or the ratio of annual net electricity to the total direct system cost) under various assumptions of O&M cost, a few plant scenarios employing high-temperature linear Fresnel technology are carefully configured to meet the aggressive LCOE goals of 8 cents/kWh and 6 cents/kWh. The latter is the Department of Energy (DOE) SunShot Initiative goal aimed at making CSP cost competitive in the current energy market. In particular, a linear Fresnel scenario with the potential to meet the SunShot goal is featured with a collector cost of $100/m2, an annual system energy efficiency of 18%, a storage system cost of $15/kWh-th, and an O&M cost of $7.5/MWh. One of the most aggressive assumptions is an advanced power block with about 52% cycle efficiency and a turbine inlet temperature of 700°C.
This work addresses unanswered questions regarding linear Fresnel cost and performance and identifies future research and development directions for linear Fresnel technology, including economic optimization of collectors and receivers, development of physical plant performance models, development of automated O&M mechanisms and sophisticated plant control software.
Morfoplane: Energetic Analysis of a Novel Green Aerial Vehicle Concept
Authors: Trancossi Michele , Dumas Antonio , Madonia Mauro 
Published: December 2013

Costs of Helium are increasing more rapidly than provided by economic analysts because of the high demanded if compared with actual production possibilities. These economic disadvantages are slowing many airship projects, because of the necessary costs that need to be faced for initial inflation. They are forcing the definition of novel airship architectures which could use hydrogen as buoyant gas with a higher level of safety than in the past.
This paper starts from those economic issues to define a general model based on the variable volume airship defined in the MAAT cruiser-feeder airship project. It defines a future hydrogen airships concept which could avoid the disasters of the past and maximize the safety of people and goods.
The model has been compared with the results of an optimization of the very general airship conceptual design based on Constructal theory. The goal of the optimization has been defined in terms of maximization of solar energy caption possibility, minimization of frontal area, volume, and energy consumption at a predefined operative altitude. A surprising accordance of the proposed model with the results of the Constructal optimization results has been obtained.
A comparison with a traditional model of airship has been performed and results have been validated by CFD simulation at different altitudes.
Solar-Assisted Heat Pump Systems: A Review of Existing Studies and Their Applicability to the Canadian Residential Sector
Authors: Chu Jenny , Cruickshank Cynthia A. 
Published: December 2013

Heat pumps are commonly used for space-heating and cooling requirements. The combination of solar thermal and heat pump systems as a single solar-assisted heat pump (SAHP) system is a promising technology for offsetting domestic hot water, space-heating and cooling loads more efficiently. Task 44 of the Solar Heating and Cooling Programme of the International Energy Agency is currently investigating ways to optimize SAHP systems for residential use. This paper presents a review of past and current work conducted on SAHP systems. Specifically, the key performance data from many studies are highlighted and different system configurations are compared in order to establish insight towards which system configurations are suitable for the Canadian residential sector.
It was found that the most suitable configuration for Canadian residential buildings depend on a combination of factors which may include occupant behavior, building characteristics, operation parameters, system components, the performance criteria of interest and climate. A large variety of configurations and parameters exist for SAHP systems and this made analyzing a specific system, comparing differing systems and establishing an optimal design fairly difficult. It was found that different authors used various different performance criterions and this inconsistency also added to the difficulty of comparing the studies of different systems. Overall, a standard performance criterion needs to be established for SAHP systems in order to meaningfully compare different configurations and determine optimal configurations for certain requirements.
Carbon Particle Generation and Preliminary Small Particle Heat Exchange Receiver Lab Scale Testing
Authors: Frederickson Lee , Kitzmiller Kyle , Miller Fletcher 
Published: December 2013

High temperature central receivers are on the forefront of concentrating solar power research. Current receivers use liquid cooling and power steam cycles, but new receivers are being designed to power gas turbine engines within a power cycle while operating at a high efficiency. To address this, a lab-scale Small Particle Heat Exchange Receiver (SPHER), a high temperature solar receiver, was built and is currently undergoing testing at the San Diego State University’s (SDSU) Combustion and Solar Energy Laboratory. The final goal is to design, build, and test a full-scale SPHER that can absorb 5 MWth and eventually be used within a Brayton cycle.
The SPHER utilizes air mixed with carbon particles generated in the Carbon Particle Generator (CPG) as an absorption medium for the concentrated solar flux. Natural gas and nitrogen are sent to the CPG where the natural gas undergoes pyrolysis to carbon particles and nitrogen is used as the carrier gas. The resulting particle-gas mixture flows out of the vessel and is met with dilution air, which flows to the SPHER.
The lab-scale SPHER is an insulated steel vessel with a spherical cap quartz window. For simulating on-sun testing, a solar flux is produced by a solar simulator, which consists of a 15kWe xenon arc lamp, situated vertically, and an ellipsoidal reflector to obtain a focus at the plane of the receiver window. The solar simulator has been shown to produce an output of about 3.25 kWth within a 10 cm diameter aperture. Inside of the SPHER, the carbon particles in the inlet particle-gas mixture absorb radiation from the solar flux. The carbon particles heat the air and eventually oxidize to carbon dioxide, resulting in a clear outlet fluid stream.
Since testing was initiated, there have been several changes to the system as we have learned more about the operation. A new extinction tube was designed and built to obtain more accurate mass loading data. Piping and insulation for the CPG and SPHER were improved based on observations between testing periods. The window flange and seal have been redesigned to incorporate window film cooling. These improvements have been made in order to achieve the lab scale SPHER design objective gas outlet flow of 650°C at 5 bar.
Spherical Tanks for Use in Thermal Energy Storage Systems
Authors: Khan Fahad , Savilonis Brian J. 
Published: December 2013

Thermal energy storage (TES) is a vital component of concentrated solar power (CSP). TES makes up for intermittent solar radiation, bad weather, and peak power demand. Currently, a sensible heat storage system using two tanks containing molten salt is considered the most practical and economical TES. Yet further system development is needed in order to improve its performance and economics.
In this study of molten salt storage tanks, spherical tanks were investigated as an alternative to cylindrical tanks. Structural and thermal aspects of cylindrical tanks with varying H/D ratios (0.25–5) and spherical tanks of the same volume were compared.
Comparison showed that utilization of spherical instead of cylindrical tanks resulted in significant savings in shell building material (28–47%). Heat transfer from the spherical tank’s shell is at least 35% less than cylindrical tanks. Reduction in building material, foundation, and insulation cost can lead to significant cost savings.
Waste From Metallurgic Industry: A Sustainable High-Temperature Thermal Energy Storage Material for Concentrated Solar Power
Authors: Calvet Nicolas , Dejean Guilhem , Unamunzaga Lucía , Py Xavier 
Published: December 2013

The ambitious DOE SunShot cost target ($0.06/kWh) for concentrated solar power (CSP) requires innovative concepts in the collector, receiver, and power cycle subsystems, as well as in thermal energy storage (TES).
For the TES, one innovative approach is to recycle waste from metallurgic industry, called slags, as low-cost high-temperature thermal energy storage material. The slags are all the non-metallic parts of cast iron which naturally rises up by lower density at the surface of the fusion in the furnace. Once cooled down some ceramic can be obtained mainly composed of oxides of calcium, silicon, iron, and aluminum. These ceramics are widely available in USA, about 120 sites in 32 States and are sold at a very low average price of $5.37/ton. The US production of iron and steel slag was estimated at 19.7 million tons in 2003 which guarantees a huge availability of material.
In this paper, electric arc furnace (EAF) slags from steelmaking industry, also called “black slags”, were characterized in the range of temperatures of concentrated solar power. The raw material is thermo-chemically stable up to 1100 °C and presents a low cost per unit thermal energy stored ($0.21/kWht for ΔT = 100 °C) and a suitable heat capacity per unit volume of material (63 kWht/m3for ΔT = 100°C). These properties should enable the development of new TES systems that could achieve the TES targets of the SunShot (temperature above 600 °C, installed cost below $15/kWht, and heat capacity ≥25 kWht/m3). The detailed experimental results are presented in the paper.
After its characterization, the material has been shaped in form of plates and thermally cycled in a TES system using hot-air as heat transfer fluid. Several cycles of charge and discharged were performed successfully and the concept was validated at laboratory scale. Apart from availability, low-cost, and promising thermal properties, the use of slag promotes the conservation of natural resources and is a noble solution to decrease the cost and to develop sustainable TES systems.
A Computational Analysis: A Honeycomb Flow Distributor With Porous Approximation for a Thermocline Thermal Energy Storage System
Authors: Afrin Samia , Ortega Jesus D. , Kumar Vinod , Bharathan Desikan 
Published: December 2013

Conversion of direct solar energy, in particular the Concentrated Solar Power (CSP) technologies, has a significant role on conventional energy cost and efficiency. A single tank thermocline Thermal Energy Storage (TES) system is accountable for the overall efficiency of this conversion system. A single tank TES system has a thermocline region that produces the temperature gradient between hot and cold storage fluid by density difference. The overall energy storage capacity depends on sustaining of this region at uniform manner. This paper analyzes how the difference in the percentage of porous medium influences the effectiveness of the flow-distribution and hence, the overall performance of the TES system. The effectiveness is assessed by the optimal flow distribution. The optimal distribution is obtained by examining the velocity profile at any horizontal plane. This plane should be uniform for sustaining the thermocline region during the operation period. To achieve a uniform velocity distribution, two symmetric perforated plate flow distributors were placed in the tank. The distributors were positioned near the inlet and outlet, and checked the performance by varying the percentage of porous medium since the distribution is influenced by the porosity. Porous distributors with hexagonal shape pore were considered and Hitec® molten salt was used as a heat transfer fluid. These respective percentages of porosity affect the flow distribution throughout the tank during the flow distribution. The standard deviations of the velocity field at different positions along z-plane and thermal diffusivity were analyzed. The analyses of our cases were done to distinguish a configuration for the minimum thermal diffusivity and velocity deviation from the mean flow.
A finite volume based computational fluid dynamics software was used to execute the computational analysis.
Electric Mobility as Part of City Transportation Systems
Authors: Weber B. , Chávez G. , Durán M. D. 
Published: December 2013

Nowadays there is a trend that more people prefer to live in cities than in rural areas, so there is the necessity of different urbanization strategies with various transportation schemes. While in most cities in the US the population density is very low with an interval of 20 to 50 inhabitants per hectare, in cities like Hong Kong more than 250 inhabitants live on an area of one hectare. As a consequence transportation needs are different, for example gasoline driven cars as preferred transportation systems for US citizens, giving rise to an average consumption of 2000 liters per year for every inhabitant; in comparison to Hong Kong, where average consumption is only 300 Liters per year. So there is a great challenge to reduce these emissions. Apparently solutions are not planned in relation to studies by the International Energy Agency that places the United States as biggest crude oil producer in the year 2017, due the increments of tight oil exploitation. In the shown scenery electro mobility can be a solution for sustainable transportation, when it is combined with PV systems.
This study starts with the feasibility of such a combination, and shows the coverage of population where this system can be implemented. From the analysis of economy results: It can be observed that the return of investment of a PV-system can be reduced when it is combined with electric mobility. Today cars driven by an electronic motor with cost of 0.035±0.015 USD/km afforded for transportation energy are more efficient than gasoline motors (based on fuel costs of 0.5±0.1 USD/km for economic cars with a coverage of 14 km/L). So it’s demonstrated that the return of investment is minor than 5 years for the PV system. It’s worth mentioning that charging batteries of electric cars could help to smooth energy peaks in the grid caused by renewables like sun and wind energy (a challenge for further grid systems). Besides the economic study the ecological impact has to be evaluated.
A Cost/Performance Evaluation of Advanced Low-Cost Heliostat Reflective Facets
Authors: Yellowhair Julius , Andraka Charles E. 
Published: December 2013

Heliostat reflective facets have traditionally been constructed with glass/silver and a metal back support. During the past year, Sandia National Laboratories evaluated low-cost materials and alternative manufacturing methods to construct facets with the goal of reducing current facet cost by at least 25% while maintaining surface slope errors at 1 milli-radians rms or below. Several companies developed prototype facet samples, which were optically evaluated at Sandia and compared to baseline facet samples using a proposed cost-to-performance metric.
A cost-performance metric for comparing facets was developed by modeling and optimizing a 200 MWe power tower plant scenario in DELSOL, a computer code for system-level modeling of power tower systems. We varied the slope error on the facets and adjusted the cost on the facets to maintain the constant plant levelized cost of energy. The result of these models provides a chart of the facet optical performance and the allowable facet cost for a constant plant LCOE.
The size of the prototype facet samples ranged from 1.4 to 3 m2. The measured optical slope errors were between 1 and 2 milli-radians rms when compared to a flat mirror design shape. Despite slope errors greater than 1 mrad rms, some of the prototype samples met the cost goals for this project using the cost-performance metric. Next steps are to work with the companies to improve the manufacturing processes and further reduce the cost and improve on the optical performance to reach DOE SunShot goal of $75/m2 for heliostats.
Thermoeconomic Analysis of Combined Cycle Coupled With Parabolic Trough Solar Plant
Authors: Duran M. D. , Rincón E. A. , Martínez I. , Lentz A. 
Published: December 2013

Parabolic trough technology is currently one of the most extended solar thermal systems for the production of electricity.
This paper describes a thermo-economic study of an integrated, combined-cycle parabolic trough power plant. The parabolic trough plant is considered an economizer or a superheater of the HRSG (heat recovery steam generator). The main objective is to obtain the optimum design of the different sections of the boiler and the size of the parabolic field. The configurations analyzed are two pressure levels with and without a reheater. A Euro Trough (ET) concentrator was used in this study, the working fluid being water with direct steam generation. There will be no problem with the evaporation in the absorber, since the solar plant will be the economizer of the HRSG and an approach point greater than 3°C is considered.
The methodology applied for the optimization is Genetic Algorithms. This methodology was employed in previous works developed by the authors and yielded good results. So that method is applied to the configurations analyzed but including the parabolic trough plant. As a result, a thermoeconomic optimum design of a parabolic trough plant used as the section of the HRSG is obtained. The results show that the solar field increases the power and efficiency of the combined-cycle plant during the operation and makes it less susceptible to load variations.
3D Modeling of an Anode Supported SOFC Using FEM and LBM
Authors: Andersson Martin , Paradis Hedvig , Yuan Jinliang , Sundén Bengt 
Published: December 2013

Solid oxide fuel cells (SOFCs) are promising as energy producing device, which at this stage of its development will require extensive analysis and benefit from numerical modeling at different time- and length scales. In this study, two models based on finite element method (FEM) and Lattice Boltzmann model (LBM), respectively, are evaluated and compared for an anode-supported SOFC. First, a 3D model is developed based on the FEM, using COMSOL, of a single SOFC operating at an intermediate temperature range. Heat, gas-phase species, momentum, ion and electron transport are implemented and coupled to the kinetics of the electrochemical reactions. Secondly, a 3D model of the porous anode of a SOFC is developed using LBM to investigate the effects of electrochemical reactions on the transport processes at microscale for 3 components (H2, H2O and O2−). Parallel computing in Python is employed through the program Palabos to capture the active microscopic catalytic reaction effects on the heat and mass transport.
It is found that LBM can be effectively used at a mesoscale ranging down to a microscale and proven to effectively take care of the interaction between the fluid particles and the walls of the porous media. The 3D LBM model takes into account the transport of oxygen ions within the solid particles of the SOFC anode. Both the oxygen ions and the hydrogen are mainly consumed by the reaction layer. One of the improvements in this study compared to our previous (FEM) models is the captured 3D effects which was not possible in 2D. High current density spots are identified, where the electron transport distance is short and the oxygen concentration is high. The relatively thin cathode results in a significant oxygen mole fraction gradient in the direction normal to the main flow direction.
Optimization of PEM Fuel Cell Flow Channels: Modeling Analysis and Experimental Tests
Authors: Liu Hong , Li Peiwen 
Published: December 2013

The dimensions of gas flow channels and walls/ribs of PEM fuel cells are optimized using a convenient mathematical model. Experimental work for several PEM fuel cells with modeling-optimized gas flow channels was conducted, and the tested results validate the modeling work and the optimization.
The model considered average mass transfer and species’ concentrations in flow channels, which allows the determination of an average concentration polarization, the humidity in anode and cathode gas channels, and thus the proton conductivity of membranes, as well as the activation polarization. An electrical circuit for the current and ion conduction is applied to analyze the ohmic losses from anode current collector to cathode current collector. The modeling computation required relatively less computational time and thus can be applied to compute a large number of cases with various flow channel designs and operating parameters for optimization analysis. Optimum ratio of the width of flow channels against the walls/ribs was found from the modeling analysis.
In the experimental work, PEM fuel cells were fabricated based on the flow channel dimensions optimized from the modeling analysis. Experimental results agreed with the modeling analysis satisfactorily in respect to the comparison of V-I performance between fuel cells with several optimized designs. The model is recommended as a tool for optimization design of gas flow channels for PEM fuel cells. The optimization results are of significance to the improvement of PEM fuel cell designs and performance.
Lattice Boltzmann Modeling of Advection-Diffusion Transport With Electrochemical Reactions in a Porous SOFC Anode Structure
Authors: Paradis Hedvig , Andersson Martin , Sundén Bengt 
Published: December 2013

Lattice Boltzmann method (LBM) is a method that can be used to capture the detailed activities of the transport processes at microscale. Here LBM is used to model the porous anode for an anode-supported Solid Oxide Fuel Cell (SOFC). The purpose of this study is to investigate the effects of electrochemical reactions on the transport processes by a 3D model at microscale. A porous 3D modeling domain is created with randomly placed spheres to resemble the part of the anode structure close to the electrolyte. The 3D model is simulated with parallel computing in Python using Palabos and also MATLAB to capture the active microscopic catalytic effects on the heat and mass transport. A multicomponent reaction-advection-diffusion transport for three components (H2, H2O and O2−) is analyzed with electrochemical reactions and particle collisions. This combined with the heat, momentum and charge transport in the 3D model.
It is here been shown that LBM can be used to evaluate the microscale effect of electrochemical reactions on the transport processes and some potential risk of hot spots to reduce harming interaction sites. The electrochemical potential is gradually increased along the flow direction as the species come in contact with each other. There is a potential risk for a hot spot when the active interacting species reach a catalytic layer and the smooth flow pattern is disturbed. Improving the flow structure by the catalytic interface can increase interaction of the reforming reactions and the electrochemical reactions, which in turn can improve the cell performance.