bluuebunny/crossref_metadata_2025 huggingface dataset:
Renewable Fuel Performance in a Legacy Military Diesel Engine
Authors: Hamilton Leonard J. , Williams Sherry A. , Kamin Richard A. , Carr Matthew A. , Caton Patrick A. , Cowart Jim S.
Published: March 2012

A new Hydrotreated Vegetable Oil (HVO) from the camelina plant has been processed into a Hydrotreated Renewable Jet (HRJ) fuel. This HRJ fuel was tested in an extensively instrumented legacy military diesel engine along with conventional Navy jet fuel JP-5. Both fuels performed well across the speed-load range of this HMMWV engine. The high cetane value of the HRJ leads to modestly shorter ignition delay. The longer ignition delay of JP-5 delivers shorter overall combustion durations, with associated higher indicated engine torque levels. Both brake torque and brake fuel consumption are better with conventional JP-5 by up to ten percent, due to more ideal combustion characteristics.
From Grease to Gas: Anaerobic Digestion of Fats, Oils, and Grease (FOG) at the Hyperion Treatment Plant
Authors: Palacios Ronald N. , Fan Steven S. , Lee Hansong , Soto Michael A.
Published: March 2012

Anaerobic digestion of high-strength organic wastes, such as Fats, Oils, and Grease (FOG) has become increasingly popular among wastewater treatment facilities in Southern California [1]. In 2010, the City of Los Angeles’ Hyperion Treatment Plant started running its own FOG Digestion Pilot Project. The project injects processed grease trap wastewater (FOG) into one of 16 anaerobic digesters at the facility. A partnership was formed between the Hyperion Treatment Plant (HTP) and Baker Commodities, Inc., a Grease rendering company located in the City of Vernon. They provide processed grease trap wastewater (FOG) to the pilot project. The plan was to load the digester with increasing amounts of FOG and observe the impact. The parameters monitored in the digester during the test are volatile acids, pH, alkalinity, temperature, and gas production in the digester. The pilot project’s objective was to obtain a 10 to 20% increase in gas production. So far those expectations have been exceeded.
A Mobile Solar-PV Demonstration System for Hands-On Learning and Curriculum Development
Authors: Budischak Cory , Koepf Erik , Opila Robert
Published: March 2012

A mobile solar-photovoltaic (solar-PV) demonstration and experimentation system has been developed for hands-on learning and curriculum development for grades K-12. The final design and design process is presented in detail, along with an assessment of the perceived technical effectiveness in meeting our original project goals. In tandem with the robust teaching tool, a curriculum was developed to compliment learning about solar-PV systems, but also to meet the needs of basic science, math and engineering teaching objectives in an integrated and hands-on way. Overall successes, failures, and a projected path forward are discussed.
The Potential of Natural Ventilation in Single-Sided Ventilated Apartment to Improve Indoor Thermal Comfort and Air Quality
Authors: Mohamed M. F. , Behnia M. , King S. , Prasad D.
Published: March 2012

Cross ventilation is a more effective ventilation strategy in comparison to single-sided ventilation. In the NSW Residential Flat Design Code1 (RFDC) the majority of apartments are required to adopt cross ventilation. However, in the case of studio and one-bedroom apartments, it is acknowledged that single-sided ventilation may prevail. Deep plan studio and one-bedroom apartments may achieve lower amenity of summer thermal comfort and indoor air quality where mechanical ventilation is not provided by air conditioning. Since compliance with the code may allow up to 40% of apartments in a development in Sydney to be single sided, it is important to understand the natural ventilation performance of such apartments. The objective of this paper is to investigate the natural ventilation potential in single-sided ventilated apartments to improve indoor air quality and thermal comfort. This investigation includes simulating various facade treatments involving multiple opening and balcony configurations. Balcony configurations are included in this study because, in Sydney, a balcony is a compulsory architectural element in any apartment building. The study uses computational fluid dynamics (CFD) software to simulate and predict the ventilation performance of each apartment configuration. This study suggests that properly configured balconies and openings can significantly improve indoor ventilation performance for enhanced indoor air quality and thermal comfort, by optimizing the available prevailing wind. However, it is important to note that inappropriately designed fac¸ade treatments also could diminish natural ventilation performance.
Impact of Storage Integrated Solar Photovoltaics (PV) Power System on Utility Peak Loads
Authors: Agyenim-Boateng K. , Boehm R. F.
Published: March 2012

The promise of large-scale use of renewables such as wind and solar for supplying electrical power is tempered by the sources’ transient behavior and the impact this would have on the operation of the grid. One way of addressing this is through the use of supplemental energy storage. While the technology for the latter has not been proven on a large scale or to be economical at the present time, some assessments of what magnitude is required can be made. In performing this work we have used NREL’s Solar Advisor Model (SAM 2010) with TMY3 solar data to estimate the photovoltaic system power generation. Climatic conditions close to load centers were chosen for the simulations. Then the PV output for varying sizes of arrays were examined and the impact of varying amounts of storage investigated. The storage was characterized by maximum limiting energy and power capacities based on annual hourly peak load, as well as its charging and discharging efficiencies. The simulations were performed using hourly time steps with energy withdrawn from, or input to, storage only after considering base generation and the PV system output in serving the grid load. In this work, we examined the load matching capability of solar PV generation (orientated for maximum summer output) for a sample Southwestern US utility grid load of 2008. Specifically we evaluated the daily and seasonal peak load shifting with employing varying storage capacities. The annual average energy penetration based on the usable solar PV output is also examined under these conditions and at different levels of system flexibility.
Thermal Property Testing of Nitrate Thermal Storage Salts in the Solid-Phase
Authors: Iverson Brian D. , Cordaro Joseph G. , Kruizenga Alan M.
Published: March 2012

Implementation of molten salt compounds as the heat transfer fluid and energy storage medium provides specific benefits to energy collection and conversion. Nitrate salts have been identified as a strong candidate for energy transfer and storage and have been demonstrated for use in these applications over time. As nitrate salts have solidification temperatures above ambient, concern for recovery from salt freezing events has instigated efforts to understand and predict this behavior. Accurate information of salt property behavior in the solid-phase is necessary for understanding recovery from a freeze event as well as for phase change thermal energy storage applications. Thermal properties for three representative salts (that span the range of melting temperatures from approximately 90–221 °C), have been obtained. These properties include specific heat, coefficient of thermal expansion, and thermal conductivity. Specific heat and thermal conductivity were measured using differential scanning calorimetry.
The Oxidation of Macroporous Cerium and Cerium-Zirconium Oxide for the Solar Thermochemical Production of Fuels
Authors: Venstrom Luke J. , Petkovich Nicholas , Rudisill Stephen , Stein Andreas , Davidson Jane H.
Published: March 2012

The H2 and CO productivity and reactivity of three-dimensionally ordered macroporous (3DOM) cerium and cerium-zirconium oxide upon H2O and CO2 oxidation at 1073K is presented in comparison to the productivity and reactivity of non-ordered porous and low porosity cerium oxide. The production of H2 and CO2 constitutes the second step of the two-step solar thermochemical H2O and CO2 splitting cycles. The 3DOM cerium oxide, with a specific surface area of 25 m2 g−1, increases the average H2 and CO production rates over the non-ordered porous cerium oxide with a specific surface area of 112 m2 g−1: the average H2 production rate increases from 5.2 cm3 g−1 min−1 to 7.9 cm3 g−1 min−1 and the average CO production rate increases from 7.7 cm3 g−1 min−1 to 21.9 cm3 g−1 min−1. The superior reactivity of 3DOM cerium oxide is attributed primarily to the stability of the 3DOM structure and also to the improved transport of reacting species to and from oxidation sites realized with the interconnected and ordered pores of the 3DOM structure. Doping the 3DOM cerium oxide with 20 mol% zirconia further stabilizes the structure and increases the average H2 and CO production rates to 10.2 cm3 g−1 min−1 and 22.1 cm3 g−1 min−1, respectively.
Comparative Analysis of Solar Thermal Cooling and Solar Photovoltaic Cooling Systems
Authors: Fumo N. , Bortone V. , Zambrano J. C.
Published: March 2012

The Energy Information Administration of the United States Department of Energy projects that more than 80% of the energy consumption of the U.S. by 2035 will come from fossil fuels. This projection should be the fuel to promote projects related to renewable energy in order to reduce energy consumption from fossil fuels to avoid their undesirable consequences such as carbon dioxide emissions. Since solar radiation match pretty well building cooling demands, solar cooling systems will be an important factor in the next decades to meet or exceed the green gases reduction that will be demanded by the society and regulations in order to mitigate environmental consequences such as global warming. Solar energy can be used as source of energy to produce cooling through different technologies. Solar thermal energy applies to technology such as absorption chillers and desiccant cooling, while electricity from solar photovoltaic can be used to drive vapor compression electric chillers. This study focuses on the comparison of a Solar Thermal Cooling System that uses an absorption chiller driven by solar thermal energy, and a Solar Photovoltaic Cooling System that uses a vapor compression system (electric chiller) driven by solar electricity (solar photovoltaic system). Both solar cooling systems are compared against a standard air cooled cooling system that uses electricity from the grid. The models used in the simulations to obtain the results are described in the paper along with the parameters (inputs) used. Results are presented in two figures. Each figure has one curve for the Solar Thermal Cooling System and one for the Solar Photovoltaic Cooling System. One figure allows estimation of savings calculated based the net present value of energy consumption cost. The other figure allows estimating primary energy consumption reduction and emissions reduction. Both figures presents the result per ton of refrigeration and as a function of area of solar collectors or/and area of photovoltaic modules. This approach to present the result of the simulations of the systems makes these figures quite general. This means that the results can be used to compare both solar cooling systems independently of the cooling demand (capacity of the system), as well as allow the analysis for different sizes of the solar system used to harvest the solar energy (collectors or photovoltaic modules).
Design of a Novel High Temperature Gravity-Fed Solar Thermochemical Reactor for Solar-Fuels Production: Case Study - ZnO Powder
Authors: Koepf Erik , Advani Suresh G. , Prasad Ajay K.
Published: March 2012

Solar fuels are emerging as a viable pathway towards closing the gap between fuel production and consumption in the United States. If these fuels can be produced on large scale and achieve carbon-neutrality, a truly sustainable energy solution may be realized. Hydrogen is among the list of attractive solar fuels. Whether used in a PEM fuel cell or combustion engine, hydrogen as a fuel produced from sunlight and water represents an elegant energy harvesting cycle, with zero-emissions, high efficiency, and exceptional power-density. A novel solar-thermochemical reactor has been designed and constructed for the reduction of ZnO at temperatures close to 2000K as the first step in a closed two-step thermochemical cycle to produce hydrogen from water as a solar fuel. Abbreviated as GRAFSTRR (Gravity-Fed Solar-Thermochemical Receiver/Reactor), the reactor is closed to the atmosphere, and features an inverted conical-shaped reaction surface along which ZnO powder descends continuously as a falling sheet and undergoes a thermochemical reaction upon exposure to highly concentrated sunlight. The reactant feed is vibration-induced, metered, and gravity-driven. Beam-down, highly concentrated sunlight enters the reaction cavity through a water-cooled aperture, and Zn product gas is siphoned into a centrally-located exit stream via a stabilized vortex flow of inert gas originating from above the aperture plane. Unreacted or partially reacted solids exit annularly around the product stream. In this paper the GRAFSTRR concept is presented. Select design choices and investigations are summarized.
Simulation of Two-Phase Flow and Heat Transfer in Mini- and Micro-Channels for Concentrating Photovoltaics Cooling
Authors: Pellicone Devin , Ortega Alfonso , del Valle Marcelo , Schon Steven
Published: March 2012

Advances in concentrating photovoltaics technology have generated a need for more effective thermal management techniques. Research in photovoltaics has shown that there is a more than 50% decrease in PV cell efficiency when operating temperatures approach 60°C. It is estimated that a waste heat load in excess of 500 W/cm2 will need to be dissipated at a solar concentration of 10,000 suns. Mini- and micro-scale heat exchangers provide the means for large heat transfer coefficients with single phase flow due to the inverse proportionality of Nusselt number with respect to the hydraulic diameter. For very high heat flux situations, single phase forced convection in micro-channels may not be sufficient and hence convective flow boiling in small scale heat exchangers has gained wider scrutiny due to the much higher achievable heat transfer coefficients due to latent heat of vaporization and convective boiling. The purpose of this investigation is to explore a practical and accurate modeling approach for simulating multiphase flow and heat transfer in mini- and micro-channel heat exchangers. The work is specifically aimed at providing a modeling tool to assist in the design of a mini/micro-scale stacked heat exchanger to operate in the boiling regime. The flow side energy and momentum equations have been implemented using a one-dimensional homogeneous approach, with local heat transfer coefficients and friction factors supplied by literature correlations. The channel flow solver has been implemented in MATLAB™ and embedded within the COMSOL™ FEM solver which is used to model the solid side conduction problem. The COMSOL environment allows for parameterization of design variables leading to a fully customizable model of a two-phase heat exchanger.
Parametric Analysis of Parasitic Pressure Drop and Heat Losses for a Parabolic Trough With Considerations of Varying Aperture Sizes and Receiver Sizes
Authors: Glenn Kyle W. , Ho Clifford K. , Kolb Gregory J.
Published: March 2012

The collector aperture and diameter of the receiver of a parabolic trough were studied to investigate the relative impacts of parasitic pressure drop, heat losses, and heat flux intercepted by the receiver tube. The configuration of an LS-2 parabolic trough was used as the baseline, and the size of the HCE and collector aperture were parametrically varied using values between the baseline and twice their original size. A Matlab computer model was created to determine the flux on the receiver, heat loss from the HCE, and pressure drop within the heat transfer fluid (HTF) at each combination of aperture size and receiver diameter. Flux on the receiver is calculated for each geometry assuming a Gaussian flux distribution. Based on pressure data from SEGS VII, the standard Darcy-Weisbach equation for the pressure drop was modified to include the contribution that connective joints of varying quantities and types have on the pressure drop within the HTF. The model employs the Sandia thermal resistive network and iteratively solves for the temperatures accounting for various heat transfer modes that contribute to the heat lost by the HCE. The Matlab model expresses pressure drop and heat losses in terms of electric power. It does this by calculating both the power required to pump the HTF for varying pressure drops and the power that could have been produced if heat was not lost to the environment. The Matlab model displays the results in the form of surface plots that represent the values of heat loss, efficiency, pumping power, etc. as a function of aperture size and receiver diameter. The combined effects of pressure drop, heat loss, and heat flux intercepted by the receiver tube were evaluated, and results show that configurations with receiver diameters ranging from 85–90 millimeters and large (up to 10 meter) aperture sizes minimize the overall power consumption and maximize the efficiency of a single loop. Structural effects, wind and gravity loads, and factors associated with the balance of plant were not considered.
Modeling and Validation of Heliostat Deformation due to Static Loading
Authors: Moya Adam C. , Ho Clifford K.
Published: March 2012

Accurate and reliable models are necessary to predict the performance and efficiencies of concentrating solar power plant components and systems such as heliostats and central receiver systems. Heliostat performance is impacted from effects such as wind and gravity, and understanding the impact of these loads on the optical performance can yield heliostat designs that are potentially cheaper, while maintaining required structural stability. Finite element models of heliostats at the National Solar Thermal Test Facility (NSTTF) at Sandia National Laboratories in Albuquerque, NM, were developed to simulate displacements under different loading scenarios. Solidworks was used to develop the three-dimensional model of the NSTTF heliostat, and Solidworks Simulation was used to perform the finite element analysis with simulated loads along different points of the heliostat. Static displacement tests were performed on the NSTTF heliostat in order to validate these FEA models. The static test results provide us with a data set in which to properly calibrate the FEA model to better represent the NSTTF heliostat for future simulations of optical performance with impacts of wind and gravity sag. In addition to a single model validation, this real world test provides a method to validate and understand the structural stability of a heliostat under static loads.
Waste-Heat Driven Miniature Absorption Refrigeration System Using Ionic-Liquid as a Working Fluid
Authors: Kim Yoon Jo , Kim Sarah , Joshi Yogendra K. , Fedorov Andrei G. , Kohl Paul A.
Published: March 2012

An ionic-liquid (IL) is a salt in a liquid state usually with an organic cation and inorganic anion. ILs provide an alternative to the normally toxic working fluids in absorption systems, such as the ammonia/water system. They also eliminate the problems of poor temperature match, crystallization and metal-compatibility problems of the water/LiBr system. In the present study, an IL is explored the working fluid of a miniature absorption refrigeration system so as to utilize waste-heat within the system for low-cost, high-power electronics cooling. To determine performance benchmarks for the refrigerant/IL (e.g. [bmim][PF6]) pairs, system-level simulations have been carried out. An NRTL model was built and used to predict the solubility of the mixture as well as the mixture properties such as enthalpy and entropy. The properties of the refrigerants were determined using REFPROP 6.0. Saturation temperatures at the evaporator and condenser were 25°C and 50°C, respectively. Chip power was fixed at 100 W with the operating temperature set at 85°C. R32 gave the highest operating efficiency with the maximum coefficient of performance (COP) of ca. 0.55 while R134a and R152a showed comparable performance with the maximum COP of ca. 0.4 at the desorber outlet temperature of 80°C. When waste-heat is available for the system operation, R134a and R152a COPs were comparable or better than that of R32.
Structural Dynamics Testing and Analysis for Design Evaluation and Monitoring of Heliostats
Authors: Griffith D. Todd , Moya Adam C. , Ho Clifford K. , Hunter Patrick S.
Published: March 2012

Heliostat vibrations can degrade optical pointing accuracy while fatiguing the structural components. This paper reports the use of structural dynamic measurements for design evaluation and monitoring of heliostat vibrations. A heliostat located at the National Solar Thermal Testing Facility (NSTTF) at Sandia Labs in Albuquerque, New Mexico, has been instrumented to measure its modes of vibration, strain and displacements under wind loading. The information gained from these tests will be used to evaluate and improve structural models that predict the motions/deformations of the heliostat due to gravitational and dynamic wind loadings. These deformations can cause optical errors and motions that degrade the performance of the heliostat. The main contributions of this work include: (1) demonstration of the role of structural dynamic tests (also known as modal tests) to provide a characterization of the important dynamics of the heliostat structure as they relate to durability and optical accuracy, (2) the use of structural dynamic tests to provide data to evaluate and improve the accuracy of computer-based design models, and (3) the selection of sensors and data-processing techniques that are appropriate for long-term monitoring of heliostat motions.
Numerical Modeling and Optimization of Hydrokinetic Turbine
Authors: Kolekar Nitin , Mukherji Suchi Subhra , Banerjee Arindam
Published: March 2012

Hydrokinetic turbines, unlike conventional hydraulic turbines are zero head energy conversion devices which utilize the kinetic energy of flowing water for power generation. The basic operational principle of the horizontal axis hydrokinetic turbine (HAHkT) is same as the wind turbine, the only difference being change in working media: water instead of air. This paper discusses the hydrodynamic design of HAHkT via numerical modeling. Presently these turbines suffer from low coefficient of performance (Cp) which is governed by several design variables such as tip-speed ratio, chord distribution, solidity and number of blades. The numerical modeling is performed for both constant and varying chord geometries using commercially available computational fluid dynamics software (CFX/FLUENT) to understand the effect of each of the design variable on turbine performance. Since the flow Reynolds number is large (≥ 105), both one- and two-equation turbulence models are applied to solve Reynolds Averaged Navier Stokes equations. In addition, a three dimensional analysis of HAHkT is performed to give a better insight into the effect of tip vortices and flow separation phenomenon on turbine performance; the results are then compared with Blade Element Momentum (BEM) theory analysis. In addition, a procedure for a multivariate optimization scheme is discussed that aims at maximizing Cp for a constant flow velocity while maintaining optimum values of critical design variables listed above. Finally, the effect of variation of angle of attack on the flow around a hydrofoil is investigate using both static and transient analysis, the transient analysis being performed by subjecting the airfoil to periodic oscillations.
Pressure Drop as a Function of Air Flow Rate for Roll-Punched Transpired Solar Collectors With Different Porosities
Authors: Barker Greg , Kiatreungwattana Kosol
Published: March 2012

Transpired solar collectors are simple and cost-effective devices suited for preheating ventilation air for buildings. They work by drawing outside air through a south-facing perforated metal absorber. The absorber is heated by solar radiation, heat is transferred to the air as it is drawn through the perforations in the absorber, and the pre-heated air is delivered to the building. Often overlooked in the design of transpired collector systems is the effect on collector efficiency of pressure drop across the absorber. The pressure drop is a function of the air flow rate through the perforations, the overall porosity of the absorber, and the properties of the air. The National Renewable Energy Laboratory (NREL) conducted a series of laboratory tests to characterize the pressure drop as a function of the relevant parameters for six commercially-available absorber configurations; three porosities in aluminum and three in steel. Each absorber material is roll-punched to one of three depths to create absorbers with three different porosities. Pressure drop, air flow rate, air temperature, and air relative humidity data were collected during the tests. The data were fit to a model that can be used to predict pressure drop across the absorber as a function of air properties and flow rate. Use of these correlations is expected to aid designers in ensuring that transpired collector systems are designed for optimal thermal efficiency and cost effectiveness.
Sustainability Attributes and Their Implementation in Energy Resources Utilization
Authors: Dobran Flavio
Published: March 2012

Energy generation with fossil fuels produces emissions of greenhouse gases into the atmosphere and releases toxic chemicals into the environment. Greenhouse gases produce global warming which can cause climate change and costly human displacements. Toxic chemicals released into the environment produce health problems and damage the ecosystems. With fossil fuels providing today over 85% of energy needs and the Earth’s population projected to increase by several billion people and energy needs projected to double by the middle of this century, considerable pressure exists to develop sustainable energy supply services. This poses an enormous challenge to engineers, economists, and policy makers. The energy mix required to produce energy for humanity depends on the availability of energy resources, security of energy supply, climate change requirements, technological breakthroughs, financial conditions, and public acceptance. Population, standard of living, toxic and greenhouse gas emissions, thermodynamic limits imposed on biophysical processes, and economics and ethics of resource utilization produce some key sustainability indicators or attributes that need to be employed for guiding our path toward a sustainable energy future. Following a general discussion of indicators and frameworks of indicators, a small number of energy supply values or objectives are presented for the purpose of developing attributes that can measure the degree of accomplishment of these objectives. A systems approach is then employed to define indicators for generic energy supply services and a risk-based multi-criteria decision making procedure is presented for deciding which energy supply service option is most sustainable. The methodology can be applied locally, regionally, and globally, by both the energy services providers and energy policy makers.
Plasma Gasification Process Modeling and Energy Recovery From Solid Waste
Authors: Valmundsson Arnar S. , Janajreh Isam
Published: March 2012

In recent studies, plasma gasification has shown great potential as an effective method for solid waste treatment and energy recovery. In this study, a plasma gasification process is simulated based on a chemical equilibrium model developed in Aspen Plus. The model takes into account the properties of different feedstock, used for gasification, and the input plasma energy and evaluates the output syngas composition following a Gibbs free energy minimization approach. The model is used to evaluate plasma gasification of three types of feedstock i.e. industrial waste (shredded tires), construction waste (plywood), and baseline bituminous coal. The process is optimized for two different types of plasma gas: air and steam. Process metrics are evaluated and compared for the considered feedstock. Results showed an obtained plasma gasification efficiency of 46.4% for shredded tires and 41.1% for plywood and bituminous coal. Energy recovery potential is also evaluated using an integrated plasma gasification combined cycle (IPGCC) power plant model. Thermal efficiencies of the process are evaluated and compared for the different feedstock. Plasma gasification of waste tire material resulted in an energy efficiency of 28.5%, while the efficiency for coal and plywood was lower at 20.0% and 18.3%, respectively.
Performance Analysis and Modeling of Different Volumetric Expanders for Small-Scale Organic Rankine Cycles
Authors: Clemente Stefano , Micheli Diego , Reini Mauro , Taccani Rodolfo
Published: March 2012

In the last years one of the main research topics in energy field is represented by Organic Rankine Cycles (ORCs), due to their applicability in energy recovery from waste heat and in distributed combined heat and power (CHP) generation, particularly in small and micro scale systems. One of the key devices of the cycle is the expander: it must have a limited cost (like all the other components, in order to ensure the economic feasibility), but also a high efficiency, since the temperature of the heat source is often low and then the cycle efficiency is inherently scarce. In the first part of this paper a literature review on various positive-displacement expanders is presented, in order to outline their performances and their application field. Then, the numerical model of a volumetric reciprocating expander is implemented. This model, and another one previously developed to simulate scroll expanders, is combined with a thermodynamic model of the whole ORC system, so that a comparison between the two technologies can be carried out. The results confirm the possibility of realizing small scale energy recovery and cogeneration (CHP) systems with acceptable electrical efficiency also adopting low-cost components, directly derived from large scale industrial components.
Characterization of a Two-Phase Pore-Scale Network Model of Supercritical Carbon Dioxide Transport Within Brine-Filled Porous Media
Authors: Ellis J. S. , Ebrahimi A. , Bazylak A.
Published: March 2012

Sequestration of carbon dioxide in deep underground reservoirs has been discussed for the reduction of atmospheric greenhouse gas emissions in the short- to medium-term until more sustainable technologies are available. Cost and long-term stability are major factors in adoption, so techniques to improve the storage efficiency and trapping security are essential. Such improvements require modeling of the porous geological formations involved in the sequestration process, and comparison to both lab- and field-based experimental studies. To this end, we are developing a comprehensive, large-scale pore-network model to describe multi-phase flow in porous media, including the structural, dissolution, and mineral trapping regimes. To explore the optimal operating parameters for mineralization trapping, we describe a two-phase pore-network model of brine-saturated aquifers and model the invasion of supercritical carbon dioxide (CO2) into the pore structure. Regularly-aligned 2D and 3D pore networks are constructed, and rules-based transport models are used to characterize the saturation behavior over a range of viscosity and capillary parameters, and coordination numbers. Finally, saturation patterns are presented for model caprock and sandstone reservoir conditions, taking into account different contact angles for CO2 on mica and quartz at supercritical conditions. These saturation patterns demonstrate the importance of surface heterogeneities in pore-scale modeling of deep saline aquifers.
Performance Analysis of a Rankine-Goswami Combined Cycle
Authors: Vasquez Padilla Ricardo , Ramos Archibold Antonio , Demirkaya Gokmen , Besarati Saeb , Goswami D. Yogi , Rahman Muhammad M. , Stefanakos Elias L.
Published: March 2012

Improving the efficiency of thermodynamic cycles plays a fundamental role in reducing the cost of solar power plants. These plants work normally with Rankine cycles which present some disadvantages due to the thermodynamic behavior of steam at low pressures. These disadvantages can be reduced by introducing alternatives such as combined cycles which combine the best features of each cycle. In this paper a combined Rankine-Goswami cycle (RGC) is proposed and a thermodynamic analysis is conducted. The Goswami cycle, used as a bottoming cycle, uses ammonia-water mixture as the working fluid and produces power and refrigeration while power is the primary goal. This bottoming cycle, reduces the energy losses in the traditional condenser and eliminates the high specific volume and poor vapor quality presented in the last stages of the lower pressure turbine in the Rankine cycle. In addition, the use of absorption condensation in the Goswami cycle, for regeneration of the strong solution, allows operating the low pressure side of the cycle above atmospheric pressure which eliminates the need for maintaining a vacuum pressure in the condenser. The performance of the proposed combined Rankine-Goswami cycle, under full load, was investigated for applications in parabolic trough solar thermal plants for a range from 40 to 50 MW sizes. A sensitivity analysis to study the effect of the ammonia concentration, condenser pressure and rectifier concentration on the cycle efficiency, network and cooling was performed. The results indicate that the proposed RGC provide a difference in net power output between 15.7 and 42.3% for condenser pressures between 1 to 9 bars. The maximum effective first law and exergy efficiencies for an ammonia mass fraction of 0.5 are calculated as 36.7% and 24.7% respectively for the base case (no superheater or rectifier process).
Analysis of Waste-to-Energy Opportunities in the New York State Food Processing Industry
Authors: Trabold Thomas A. , Ramchandra Rajiv , Haselkorn Michael H. , Williamson Anahita A.
Published: March 2012

Many food processing plants in New York State generate large volume waste streams with a wide variety of physical and chemical properties. With greater environmental regulation and increasing fees for municipal sewer and solid waste disposal, additional innovative ‘disposal’ methods for these wastes need to be developed. One attractive alternative is to use the food processing waste as feedstock for a waste-to-energy conversion process comprising two distinct systems, namely waste-to-fuel and fuel-to-energy. The fuel can either be sold to generate revenue, or converted on-site to electrical or thermal energy to offset the plant power requirements. In this study, the technical viability and economic benefit of applying waste-to-energy solutions to a diverse selection of companies producing milk, cheese, beer, and tofu were assessed. Depending upon the volumes and composition of the available waste streams (including analysis of sugar content, biological oxygen demand, etc.) there may be a compelling business case to utilize the food waste as feedstock for ethanol, biodiesel or methane-rich biogas production.
Optimization of Technical and Operational Characteristics of a CAES Facility in West Texas to Balance Intermittent Wind Power
Authors: Townsend Aaron K. , Webber Michael E.
Published: March 2012

An optimization model was created to optimize the input power capacity and storage capacity relative to the output power capacity of a compressed air energy storage (CAES) facility in the Electric Reliability Council of Texas (ERCOT) grid. Historical electricity and non-spinning reserve prices were used to calculate the economic feasibility of CAES in each of the zones in ERCOT. The analysis found that with perfect knowledge of future prices a CAES facility would be economically attractive over the period of years considered, and the non-spinning reserve ancillary service market provided a substantial contribution to the overall revenue of the facility. Optimal input power capacity for the entire period of 2002 through 2010 was found to be about one-quarter of the output capacity in the Houston, South, and North zones in ERCOT and one-half the output power capacity in the West zone in ERCOT. Optimal storage capacity was found to be about 17 hours in the Houston, South, and North zones and 31 hours in the West zone. Optimal values for individual years varied significantly, as did revenues. The negative electricity prices that have occurred historically in the West zone are the consequence of wind generators and lack of transmission capacity to export electricity; this effect gives CAES greater opportunity to perform price arbitrage and improves the economics of such a facility.
An Integrated Energy Storage Scheme for a Dispatchable Solar and Wind Powered Energy System and Analysis of Dynamic Parameters
Authors: Garrison Jared B. , Webber Michael E.
Published: March 2012

The intermittency of wind and solar power and the mismatch between when they are available and when demand is high have hindered the expansion of these two primary renewable resources. The goal of this research is to analyze an integrated energy system (named DSWiSS for dispatchable solar wind storage system) that includes a novel configuration of wind and solar together with compressed air energy storage (CAES) that is driven from excess nighttime wind energy and thermal storage energized by concentrated solar power in order to make these sources dispatchable during peak demand. Notably, existing CAES facilities use natural gas for heating the compressed air before its expansion through a turbine; the system described in this paper replaces the use of natural gas with solar energy and thermal storage, thereby obviating the need for fossil fuels and yielding a dispatchable system powered completely by renewable sources. This paper builds off prior published work for the DSWiSS configuration with an analysis of temporally-resolved parameters, including wind and solar resources, which are important to the operation of DSWiSS. This analysis uses actual historical meteorological data for West Texas solar insolation, telemetry data for wind power in West Texas, and recorded electricity demand data of the ERCOT grid to assess system performance. We examined how the daily variation of these parameters could affect the operation of an energy storage facility such as DSWiSS. We found that the daily fluctuations were most pronounced in the summer when demand is highest and wind velocity is lowest. However, because all seasons show a time-of-day phase mismatch between demand and wind velocity, we expect that a load leveling energy storage technology would be useful to the electric grid. Research to be completed soon will attempt to use control strategies along with the existing thermodynamic model of the DSWiSS power system to determine how DSWiSS would be operated differently under the different seasonal situations.
Systems Engineering Development on a Student-Designed B20 Plug-In Hybrid Electric Vehicle for the EcoCar Competition
Authors: Carter Sean , White Darris , Karr Ashley , Liu Dahai
Published: March 2012

Systems engineering plays a vital role in project and production development. The complete life cycle of a project incorporates systems engineering throughout. Systems are involved from the beginning, involving the conceptual design and planning processes, to the very end with testing procedures and production finalization. The topic involves subject matter as testing procedures, validating data, verifying the requirements, designing for failure modes, instigating faults into the system, and most importantly developing requirements for the system continuously throughout the life cycle. The Department of Energy and many other large organizations use systems engineering to plan, process, and produce multiple types of products and projects. A lot of companies also follow this process due to the usefulness and productivity improvement. Engineers that learn this process are able to help streamline their area of expertise. General Motors along with Argonne National Laboratory and The Department of Energy have sponsored a competition named EcoCar: The NeXt Challenge. This competition requires a lot of planning by both the organizers and the collegiate students involved. A lot of requirements were developed and then given to the universities for the development of a hybrid vehicle architecture that would be successful after three years. The EcoEagles were required to develop documentation while following the simple guidelines of systems engineering. The paper plans to describe each area of systems engineering the team used along with what was learned and how the team benefitted from using the process. The paper more importantly plans to go into detail how systems engineering practices are vital to project development, safe products, and quality production standards.
Experimental Evaluation of a Solar Intermittent Refrigerator Working With the Mixtures NH3 – LiNO3 and NH3 – LiNO3 – H2O
Authors: Moreno-Quintanar G. , Rivera W. , Best R.
Published: March 2012

Solar energy could help to reduce the request of electric energy which is generated via hydrocarbons, having the possibility to provide energy to rural communities which do not have it through the conventional distribution. The application of solar system on refrigeration has a great range of development, that will have a competitive cost when the hydrocarbons diminish. An intermittent solar refrigerator that works with the absorption cycle is studied in the Center of Research on Energy of UNAM. It was designed to produce 8 kg of ice. The refrigerator consists of a condenser, an expansion valve, an evaporator and a generator/absorber. A compound parabolic concentrator (CPC) receives solar energy and turns into thermal energy. It is concentrated in the cylindrical receiver that works as generator or absorber. Being intermittent, the refrigerator performs two stages to complete a refrigeration cycle: a generation-condensation stage and another of evaporation-absorption stage. The present work focuses on the evaluation of the generation-condensation stage. One of the working mixture is ammonia-lithium nitrate (NH3 – LiNO3) that presents some advantages over the common mixtures such as the avoiding of rectification and working with relatively low manometric pressures. A disadvantage is that it presents crystallization at low concentrations. The other working mixture is ammonia-lithium nitrate-water (NH3 – LiNO3 – H2O) with higher conductivity and lower viscosity than the ammonia/lithium nitrate. Several test were made at different solution concentrations for both mixtures, binary mixture (NH3 – LiNO3) and ternary mixture (NH3 – LiNO3 – H2O). Comparing the performance of the system operating with the two mixtures, it was found that with the ternary mixture the solar coefficients of performance can be up to 24% higher than those obtained with the binary mixture.
CFD Simulation and Performance Analysis of Alternative Designs for High-Temperature Solid Particle Receivers
Authors: Khalsa Siri Sahib S. , Christian Joshua M. , Kolb Gregory J. , Ro¨ger Marc , Amsbeck Lars , Ho Clifford K. , Siegel Nathan P. , Moya Adam C.
Published: March 2012

Direct-absorption solid particle receivers are theoretically capable of yielding temperatures in excess of 1000°C, which enables higher efficiency power cycles and lower thermal storage costs. This paper presents rigorous CFD simulations of alternative solid particle receiver designs with recirculation to help identify optimal configurations that maximize the receiver thermal efficiency. The alternative receiver designs considered are a north-facing cavity receiver and a face-down surround-field cavity receiver. The CFD simulations model incident solar radiation from a heliostat field as a boundary condition on the model domain. The CFD simulations also couple convective flow with the thermal and discrete-phase (particle) solutions, which in turn affects absorption of incident solar radiation and thermal re-radiation within the receiver. The receivers are optimized to yield comparable particle temperatures at the outlets of 750–850°C, heated from an injection temperature of 300°C, and are compared on the basis of thermal efficiency. The CFD simulations yielded thermal efficiencies of the north-facing receiver at 72.3% (losses were 6.5% radiative and 20.9% convective) and the face-down receiver at 78.9% (losses were 11.4% radiative and 9.6% convective) at solar noon on March 22. Ongoing efforts are focused on reducing convective and radiative losses from both receiver configurations.
Heat Transfer Coefficient Between Flat Surface and Sand
Authors: Golob Matthew , Jeter Sheldon , Sadowski Dennis
Published: March 2012

Thermal energy storage (TES) systems are of interest in solar thermal power applications as an effective means of retaining energy. One of the primary issues with this type system is the exchange of thermal energy coming off the power field. In a heat exchanger, the effective heat transfer coefficient between the exchange mediums plays a crucial factor in determining the sizing of the heat exchange unit. A concept utilizing sand as a cheap particulate thermal medium was recently proposed for an alternative thermal energy storage system. The overall system will be described in some detail; however, the primary focus of this research report will be to present the experimental results measuring the heat transfer coefficient between flowing sand and a representative heat exchanger surface. To measure the heat transfer coefficient a horizontal rotating drum is used to continuously deposit sand over a centrally positioned test article. The heat transfer coefficient in this case was calculated by taking the power input divided by the known area of the test article covered by the sand as well as the measured temperature difference between the article surface and sand temperature. Calibrated thin film thermocouples attached to the test article surface as well as thin film thermocouples suspended into the sand pooling in drum satisfy the needed temperature measurements. Then, by electrically heating a known area of the test article, a heat transfer coefficient between the sand and surface can be determined. Insulation of key end surfaces and errors such as heat leak due to air as well as measurement inaccuracies were also accounted for in the experimental setup and are included in the report’s error propagation analysis. The overall results compare heat transfer coefficients measurements for a range of different sands and sizes, as well as model comparisons with known literature on the subject.