bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of the Chilled Water System Analysis Tool for Assessing Energy Conservation Opportunities
Authors: Gaudani Ghanshyam , Quintal Alex , Kosanovic Dragoljub
Published: December 2013

Chilled water systems constitute a major portion of energy consumption in air conditioning systems of the large buildings and process cooling of the manufacturing plants. These systems do not operate optimally in most of the cases because of the operating parameters set and/or the components used. The Chilled water system analysis tool software (CWSAT) is developed as a primary screening tool for energy evaluation. This tool quantifies the energy usage of the various chilled water systems and typical measures that can be applied to these systems to conserve energy. The tool requires minimum number of inputs to analyze the component-wise energy consumption and incurred overall cost. Both air-cooled and water-cooled systems can be analyzed with this tool; however, this paper focuses on water-cooled systems. The tool uses weather data of the chilled water system location and loading schedules to calculate the chilled water system energy consumption. The Air-Conditioning and Refrigeration Institute (ARI) standard 550/590 typical loading schedule is also incorporated for the chiller(s) loading. The tool is capable of comparing economics by analyzing the energy consumption and relevant cost of the existing system and the new system with cost reduction opportunities considered like: (1) increase chilled water temperature set point, (2) lowering the condenser cooing water supply temperature set point, (3) replace chiller(s), (4) Apply variable speed control to chilled and/or condenser water pumps, (5) upgrade cooling tower fan speed control, (6) Use free cooling when possible for water-cooled systems. The savings can be calculated separately for each cost reduction opportunity or can be combined. The economics comparison can be a primary decision criterion for further detailed engineering and cost analysis related with system changes. The comparison between actual system energy consumption and CWSAT results are also shown.
Modeling a Novel Composite Adsorbent Based Adsorption Chiller Driven by Solar Energy
Authors: Tso C. Y. , Fu S. C. , Chao Christopher Y. H.
Published: December 2013

This paper aims to study the performance of a solar-powered adsorption chiller with a novel composite adsorbent material (silica activated carbon/CaCl2) operating during some typical months in Hong Kong. Modeling is established to investigate the cooling performance of this adsorption chiller driven by flat-type solar collectors with three different configurations of glaze: 1) single glazed cover; 2) double glazed cover and 3) transparent insulation material (TIM) cover. The simulation results show that the higher the solar collector temperature is, the better the coefficient of performance (COP) and the specific cooling power (SCP) of the adsorption chiller are. It is suggested to select a double glazed collector with a small value of the lumped capacitance for this adsorption chiller. Seasonal effects are discussed in which the solar COP achieves its highest value during autumn. However, the cooling capacities in spring, summer and autumn are similar. All in all, this newly developed composite material as adsorbent used in the adsorption chiller could achieve a mean solar COP of 0.36 and SCP of 94W/kg on a typical summer day of operation.
Microfluidic Tunable Liquid Prisms for Solar Beam Steering and Concentration
Authors: Park Sung-Yong , Cheng Jiangtao , Chen Chung-Lung (C.-L. )
Published: December 2013

Concentrated photovoltaic (CPV) is an alternative solution to reduce the cost of solar PV systems by using less semiconductor materials. One key component in CPV systems is a solar tracker that enables to keep them in an optimal position to maximize solar concentration. However, CPV solar trackers typically are expensive, often unreliable and require lots of power, because they are composed of bulky, complex and heavy mechanical moving parts such as motors and supporting frames. These bulky and heavy tracking components make CPV systems difficult to be installed on building or residential rooftop.

We present a microfluidic tunable liquid prim panel that enables to track the daily and seasonal sun’s motion and concentrate steered sunlight onto a solar cell for solar power generation. The panel consists of arrayed tunable liquid prisms. An apex angle in each prism is tuned by electrowetting, which allows incident light to be adaptively steered and focused onto a solar cell. Our systems consume very little power in the range of ∼mW as well as require no heavy and expensive supporting hardware or moving parts for solar tracking. We discuss concept, design and analytical estimation of the system performances. It is able to steer incoming light beam with incident angle up to α = ± 70°, while only causing additional optical reflection loss about 5 ∼ 10%. We have fabricated the liquid prism with a 1cm × 1cm aperture area and demonstrated apex angle modulation up to φ = ± 30°, and beam steering up to Δα = 14.6°. By eliminating expensive and inefficient motor-driven mechanical solar trackers, our optofluidic solar tracking system can offer a cost-effective CPV system with low power consumption for residential or building rooftop installation.
Transient Three-Dimensional Heat Transfer Model of a Solar Thermochemical Reactor for H2O and CO2 Splitting via Nonstoichiometric Ceria Redox Cycling
Authors: Lapp Justin , Lipiński Wojciech
Published: December 2013

A transient heat transfer model is developed for a solar reactor prototype for H2O and CO2 splitting via two-step non-stoichiometric ceria cycling. Counter-rotating cylinders of reactive and inert materials cycling between high and low temperature zones permit continuous operation and heat recovery. To guide the reactor design a transient three-dimensional heat transfer model is developed based on transient energy conservation, accounting for conduction, convection, radiation, and chemical reactions. The model domain includes the rotating cylinders, a solar receiver cavity, and insulated reactor body. Radiative heat transfer is analyzed using a combination of the Monte Carlo method, Rosseland diffusion approximation, and the net radiation method. Quasi-steady state distributions of temperatures, heat fluxes, and the non-stoichiometric coefficient are reported. Ceria cycles between temperatures of 1708 K and 1376 K. A heat recovery effectiveness of 28% and solar-to-fuel efficiency of 5.2% are predicted for an unoptimized reactor design.
Metal Oxide Reduction Using a Solar-Driven Vacuum Thermogravimeter
Authors: Neises-von Puttkamer Martina , Takacs Michael , Haueter Philipp , Maier Markus , Steinfeld Aldo
Published: December 2013

We present a kinetic study performed in a solar-driven vacuum thermogravimeter (solar-TG), in which solid reactants are directly exposed to high-flux irradiation while their weight change is continuously monitored. The system allows testing under a total vacuum pressure as low as 10 mbar. With this arrangement, the rate of thermochemical reactions can be examined under the same radiative heat transfer characteristics and heating rates typical of solar reactors. The solar-TG system is used to investigate metal oxides redox cycles for splitting H2O and CO2 and for high-temperature heat storage. Operation of the metal oxide reduction under vacuum pressures is of special interest because it eliminates the need for purge gas, thus simplifying the process and avoiding energy penalties associated with inert gas recycling.
Corrosion of Austenitic Alloys in Binary 60/40 Nitrate Salt at 600°C
Authors: Kruizenga Alan , Gill David , LaFord Marianne
Published: December 2013

Industrial power utilities are using molten binary nitrate salt as a heat transfer fluid and thermal storage media for solar energy generation. Currently, the maximum bulk temperature is 565°C, due to concerns of salt degradation and materials compatibility with containment vessels.

To increase overall cycle efficiency, one must increase the upper temperature of the nitrate salt, thereby lowering the levelized cost of electricity (LCoE) through higher power cycle efficiency. The corrosion performance of 316 stainless steel and Inconel 625 is currently characterized at 600°C. However, the 316SS has exhibited stress corrosion cracking (thought due to aqueous flush in Solar Two [1]), and while In625 performs well, its cost is prohibitive. Therefore, current research seeks to evaluate heat-resistant austenitic alloys for use with nitrate salts, ascertaining if they have superior performance characteristics, as well as assessing their mechanisms of corrosion.

Sandia National Laboratory is researching four alloys (S35140, ATI332Mo, RA330, and HA556) for corrosion performance at 600°C for 3000 hours, under a cover gas of air. Air is used to simulate the chemistry conditions expected in a power plant.

This work details the corrosion rate and the oxide structure for each alloy. Research indicates all alloys are very corrosion-resistant, with metal loss rates projected to be less than 21μm/year after 3000 hours. Though all alloys performed well, corrosion rate data for RA330 (Fe-19Cr-35Ni + minor elements) currently appears to exhibit a linear loss mechanism. In conclusion, this paper will explore the differences in oxide formation between these similar alloys.
Enhancement Performance of Rotary Air Preheater for Thermal Power Plants
Authors: Abdulsada Ghanim K. , Alhamdo Mohammed H.
Published: December 2013

All the previous theoretical models of the dynamic thermal behavior of the periodic–flow Air Pre-Heater (APH) have ignored the effects of the baskets walls. Therefore, the purpose of this work is to develop experimental and a numerical model simulating transient energy transport in a periodic-flow regenerative APH to involve the important thermal effect of the basket walls surrounding the heating element matrices.

Three main different types of matrices that are intended to be used in periodic-flow APH have been investigated and comparison was made between them. These materials are corrugated plates matrices (CPMs), wire mesh matrices (WMMs) and stone media matrices (SMMs). Total of (13) different configurations of matrices have been tested. The investigations covered a range of geometrical parameters of corrugated plate angle, wire diameter of mesh, pitch and screen to screen position and size of stones. The investigation has been carried out for hydraulic – diameter base Reynolds number, Re, in the range of 680<Re < 10100.

The basket wall was determined to have a significant influence on the thermal behavior of the packing matrices especially in the near–wall region, and had been seen to introduce different thermal response for each type of the tested materials.

New (13) correlation equations for the overall J-factor have been developed for each matrix type to provide the best matching between the gathered experimental data with the numerical model.
Archimedes Screws for Microhydro Power Generation
Authors: Lyons Murray , Lubitz William David
Published: December 2013

Archimedes screw generators (ASGs) are beginning to be widely adopted at low head hydro sites in Europe, due to high efficiency (greater than 80% in some installations), competitive costs and low environmental impact. Compared to other microhydro generation technologies, ASGs have greatest potential at low head sites (less than about 5 m). The performance of an Archimedes screw used as a generator depends on parameters including screw inner and outer diameter, slope, screw pitch and number of flights, and inlet and outlet conditions, as well as site head and flow. Despite the long history of the Archimedes screw, there is very little on the dynamics of these devices when used for power generation in the English literature. Laboratory tests of small Archimedes screws (approximately 1 W mechanical power) have been conducted to support the design and validation of ASG design tools. This paper reports experimental results examining the relationship between torque, rotation speed and power. The laboratory screw maintained reasonable efficiency over wide ranges of operating conditions, although distinct efficiency peaks were found to occur. The cause of changes in power output caused by varying the water level at the outlet of the screw were attributed primarily to the corresponding variation in head, and dynamic limiting of screw rotation speed causing corresponding limits in volume flow through the screw. Test results were qualitatively consistent with data from a prototype ASG installed by Greenbug Energy in southern Ontario, Canada, and recent data reported from European laboratory tests and commercial installations.
Effect of Natural Convection on Thermal Energy Storage in Supercritical Fluids
Authors: Lakeh Reza Baghaei , Lavine Adrienne S. , Kavehpour H. Pirouz , Ganapathi Gani B. , Wirz Richard E.
Published: December 2013

Heat transfer to the storage fluid is a critical subject in thermal energy storage systems. The storage fluids that are proposed for supercritical thermal storage system are organic fluids that have poor thermal conductivity; therefore, pure conduction will not be an efficient heat transfer mechanism for the system. The current study concerns a supercritical thermal energy storage system consisting of horizontal tubes filled with a supercritical fluid. The results of this study show that the heat transfer to the supercritical fluid is highly dominated by natural convection. The buoyancy-driven flow inside the storage tubes dominates the flow field and enhances the heat transfer dramatically. Depending on the diameter of the storage tube, the buoyancy-driven flow may be laminar or turbulent. The natural convection has a significant effect on reducing the charge time compared to pure conduction. It was concluded that although the thermal conductivity of the organic supercritical fluids are relatively low, the effective laminar or turbulent natural convection compensates for this deficiency and enables the supercritical thermal storage to charge effectively.
A Multi-Zone Building Energy Simulation of a Data Center Model With Hot and Cold Aisles
Authors: Phan Long , Lin Cheng-Xian , Schäfer Mirko
Published: December 2013

In this paper, a building energy simulation code, EnergyPlus, was used to study selected important conditions, i.e. wall boundary conditions and locations, which potentially affect the energy consumption and thermal management of a popular data center model. The data center model having 1120 servers distributed in four rows of rack was investigated under two major climate conditions — hot and humid (Miami, FL), and cool and humid (Chicago, IL), and under five different wall boundary conditions. The data center model was first simulated under a well-mixed single-zone condition as a baseline. Then, a multi-zone approach was proposed to resolve the hot and cold aisles and used to investigate the data center performance. Both monthly and annual overall energy consumption as well as cooling load reports were analyzed and compared among various boundary conditions. In addition, monthly thermal behavior of hot and cold aisle zones within the data center was analyzed. The simulation results show that thermal performance of the data center is significantly affected by locations or climate conditions. The effects of location and wall boundary conditions are particularly appreciable during the summer and winter seasons.
Analysis of a Latent Heat Storage Device With Radial Fins
Authors: Kozak Y. , Rozenfeld T. , Ziskind G.
Published: December 2013

Phase-change materials (PCMs) can store large amounts of heat without significant change of their temperature during the phase-change process. This effect may be utilized in thermal energy storage, especially for solar-thermal power plants. In order to enhance the rate of heat transfer into PCMs, one of the most common methods is the use of fins which increase the heat transfer area that is in contact with the PCM.

The present work deals with a latent heat thermal storage device that uses a finned tube with an array of radial fins. A heat transfer fluid (HTF) flows through the tube and heat is conducted from the tube to the radial fins that are in contact with the bulk of the PCM inside a cylindrical shell. The thermal storage charging/discharging process is driven by a hot/cold HTF inside the tube that causes the PCM to melt/solidify.

The main objective of the present work is to demonstrate that close-contact melting (CCM) can affect the storage unit performance. Accordingly, two different types of experiments are conducted: with the shell exposed to ambient air and with the shell submerged into a heated water bath. The latter is done to separate the PCM from the shell by a thin molten layer, thus enabling the solid bulk to sink. The effect of the solid sinking and close-contact melting on the fins is explored. It is found that close-contact melting shortens the melting time drastically.

Accordingly, two types of models are used to predict the melting rate: numerical CFD model and analytical/numerical close-contact melting model. The CFD model takes into account convection in the melt and the PCM property dependence on temperature and phase. The analytical/numerical CCM model is developed under several simplifying assumptions. Good agreement is found between the predictions and corresponding experimental results.
Thermo-Mechanical Storage of Electricity at Power Plant Scale
Authors: Steinmann Wolf-Dieter
Published: December 2013

The availability of cost effective storage capacity is considered essential for increasing the share of renewables in electricity generation.

With the development of solar thermal power plants large thermal storage systems have become commercial in recent years. Various storage concepts are applied, systems using solid storage media are operated at a maximum temperature of 680 °C, other systems using molten salt as storage medium show thermal capacities in the GWh range. Heating these storage systems directly by surplus electricity and using the heat later during the discharge process to operate turbines is not very attractive, since the process is limited by the Carnot efficiency.

Alternatively, surplus electricity can be used to transform low temperature heat into high temperature heat which is stored in a thermal storage system during the charging process. During discharge, this heat is used to drive a turbine generating electric energy. Theoretically, this concept allows a roundtrip efficiency of 100%.

Various options for the implementation of this storage concept have been suggested, using air or CO2 as working fluids. Recently, DLR has demonstrated the operability of a latent heat storage system connected to a steam circuit at 100 bar. The availability of this latent heat storage technology allows new implementations of the storage concept based on heat transformation. Using a left-running Rankine cycle during the charging process, heat from the environment is used to evaporate steam, which is compressed using the surplus electricity. Superheated steam exiting the compressor flows through the thermal storage system composed of latent heat storage sections and sensible heat storage sections. After throttling, the water enters the evaporator again. During discharging, heat from the storage system is used to evaporate and superheat steam, which drives the turbine. A cascaded implementation of this concept, using ammonia for the low temperature part of the process, while water is used for the high temperature part, reaches a storage efficiency of 70%. The integration of low temperature waste heat sources allows the compensation of losses.
Latent Solar Thermal Storage Systems: Packed Beds With Spherical Phase Change Capsules of Different Physiochemical Properties
Authors: Aldoss Taha
Published: December 2013

A latent thermal storage system LTSS of spherical PCM capsules packed bed is considered in this investigation. Such a LTSS is considered to be one of the most practical systems for the purpose. It is compact, easy to construct and maintain, with very good storage characteristics. Physiochemical properties of PCM and the capsules size are the two most effective properties of the storage system. Number of researchers investigated the performance of such systems under different designs and operating conditions. In this work a LTSS system is constructed with PCM capsules of different sizes and of different PCM properties. The capsules are packed with different capsules sizes and varying PCM properties along the bed to match the temperature profile best. The performance of the LTSS as described is investigated numerically and presented in terms of the bed temperature profiles function of location and charging time. The effectiveness of the storage system is presented in terms of time evolution of the liquid fraction of the PCM and in terms of the percentage of the energy storage in the PCM. The first represent the degree of utilization of the PCM and the later shows the effectiveness of the heat transfer and storage process of the LTSS for different system designs. The results as above are compared with the reference cases of uniform arrangements with uniform and constant PCM properties along the bed.
Technical and Economic Feasibility Analysis of Using Concentrated Solar Thermal Technology in the Cement Production Process: Hybrid Approach — A Case Study
Authors: Gonzalez Ricardo S. , Flamant Gilles
Published: December 2013

Currently, increasing world population demands a higher cement production. Therefore atmospheric emissions and energy consumption become two of the most important environmental and economic issues. Fuel and electricity consumption for the production of cement represent 40% of the total production cost [1]. It is known that cement production is an energy-intensive process which contributes with approximately 5% of the worldwide carbon dioxide (CO2) emissions [2] [3].

By using Concentrated Solar Thermal (CST) at the calcination process in the cement production line, CO2 emissions can be reduced by 40% and savings of up to 60% through fuel substitution can be obtained if all the fuel used at the calcination step is substituted.

The aim of the study is not to propose a detailed design of the solar process but to examine and quantify the various options in order to define the favorable economic conditions and the technical issues to face in a conventional cement plant aiming: substituting energy sources and achieving continuous operation of the cement plant employing a hybrid mode.

Three options related with how to apply the CST technology were evaluated. The best solution is a Central Tower with Solar Reactor at the Top of the Tower since it allows energy substitution with high thermal energy efficiency. This implies, compared with the other options, the minimum changes in the process.

Several energy substitution scenarios are investigated considering different energy losses and amount of energy to be replaced. It was found that the solar energy availability is not a constraint, meaning that from the technical point of view it is possible to replace up to 100% of the energy requirements for the calcination process.

Economic results are promissory since the application of the proposed approach (Go Process) became attractive. The Payback Time (PBT) obtained (from 6 to 10 years) is lower when it is compared with the PBT for applications of CST for electricity production. Besides, the IRR values obtained (from 8% to 11%) are adequate in accordance with the typical values expected by most of the equity investors in renewable energy projects (between 8% and 12%) [4].

It is expected that CST technology will become more attractive and profitable due to economic aspects like increments in fossil fuels and alternative fuels cost and the current deployment of the CST technology to produce electricity. Other aspects such as more strict legislation related with CO2 emissions combined with encouraging legislation to use of renewable energy also play an important role in the economic attractiveness of the proposed application.
Enhanced Thermal Performance of Ionic Liquid-Al2O3 Nanofluid as Heat Transfer Fluid for Solar Collector
Authors: Paul Titan C. , Morshed A. K. M. M. , Fox Elise B. , Visser Ann E. , Bridges Nicholas J. , Khan Jamil A.
Published: December 2013

Next generation Concentrating Solar Power (CSP) system requires high operating temperature and high heat storage capacity heat transfer fluid (HTF), which can significantly increase the overall system efficiency for power generation. In the last decade several research going on the efficacy of ionic liquids (ILs) as a HTF in CSP system. ILs possesses superior thermophysical properties compare to currently using HTF such as Therminol VP-1 (mixture of biphenyl and diphenyl oxide) and thermal oil. However, advanced thermophysical properties of ILs can be achieved by dispersing small volume percentage of nanoparticles forming nanofluids, which is called Nanoparticle Enhanced Ionic Liquids (NEILs). In the present study NEILs were prepared by dispersing 0.5% Al2O3 nanoparticles (spherical and whiskers) in N-butyl-N, N, N-trimetylammonium bis(trifluormethylsulfonyl)imide ([N4111][NTf2]) IL. Viscosity, heat capacity and thermal conductivity of NEILs were measured experimentally and compared with the existing theoretical models for liquid–solid suspensions. Additional, the convective heat transfer experiment was performed to investigate thermal performance. The thermal conductivity of NEILs enhanced by ∼5%, heat capacity enhanced by ∼20% compared to the base IL, which also gives 15% enhancement in heat transfer performance.
Three-Dimensional Fluid Dynamics and Radiative Heat Transfer Modeling of a Small Particle Solar Receiver
Authors: Fernández del Campo Pablo , Miller Fletcher , Crocker Adam
Published: December 2013

We present an investigation of the effects of the solar irradiation and mass flow conditions on the behavior of a Small Particle Solar Receiver employing our new, three-dimensional coupled fluid flow and radiative heat transfer model. This research expands on previous work conducted by our group and utilizes improved software with a set of new features that allows performing more flexible simulations and obtaining more accurate results. For the first time, it is possible not only to accurately predict the overall efficiency and the wall temperature distribution of the solar receiver, but also to determine the effect on the receiver of the window, the outlet tube, real solar irradiation from a heliostat field, non-cylindrical geometries and 3-D effects. This way, a much better understanding of the receiver’s capabilities is obtained. While the previous models were useful to observe simple trends, this new software is flexible and accurate enough to eventually act as a design and optimization tool for the actual receiver.

The solution procedure relies on the coupling of the CFD package ANSYS Fluent to our in-house Monte Carlo Ray Trace (MCRT) software. On the one hand, ANSYS Fluent is utilized as the mass-, momentum- and energy-equation solver and requires the divergence of the radiative heat flux, which constitutes a source term of the energy equation. On the other hand, the MCRT software calculates the radiation heat transfer in the solar receiver and needs the temperature field to do so. By virtue of the coupled nature of the problem, both codes should provide feed-back to each other and iterate until convergence. The coupling between ANSYS Fluent and our in-house MCRT code is done via User-Defined Functions.

After developing the mathematical model, setting up and validating the software, and optimizing the coupled solution procedure, the receiver has been simulated under fifteen different solar irradiation and mass flow rate cross combinations. Among other results, the behavior of the receiver at different times of the day and the optimum mass flow rate as a function of the solar thermal input are presented. On an average day, the thermal efficiency of the receiver is found to be over 89% and the outlet temperature over 1250 K at all times from 7:30 AM to 4:00 PM (Albuquerque, NM) by properly adapting the mass flow rate. The origin of the losses and how to improve the efficiency of the Small Particle Solar Receiver are discussed as well.
Optical-Mechanical Analysis of Parabolic Trough Solar Concentrators to Support Commercial Development
Authors: Biggio Kenneth , Backes Rachel , Crawford Jennifer
Published: December 2013

The thermal performance of parabolic trough concentrating solar collectors depends on both the structural and optical characteristics of the design. In order to reduce the cost of energy, advanced concentrating structures must significantly reduce the cost of collectors while maintaining good optical performance. This paper discusses a Finite Element Ray Tracer (FERT) that has been developed specifically to support the commercial design process. This is achieved by tying the whole of the support structure directly to its optical effects. Consequently, the optical performance metrics go beyond the typical reflector slope error RMS or average intercept factor to present the designer with spatially resolved analysis of localized performance. By incorporating this analytical method into the structural design process, collector cost and performance can be balanced efficiently and rapidly, allowing for an accelerated design period. At times, this insight has driven better, albeit unexpected, design decisions.

The paper presents an overview of the development process that Abengoa R&D uses to take advantage of its analytical optical analysis capability throughout all phases of a project, as well as a review of its implementation. A selection of case studies is also presented to illustrate how FERT enables the designer to identify local areas of concern, diagnose the cause, and quickly develop possible redesign strategies. Finally, the significance of various parameters within the ray tracer are discussed.
Investigating the Structural Properties of Corn Stover at Macro and Fiber Levels
Authors: Özdemir Ozan Ç. , Suess Taylor N. , Letcher Todd M. , Gent Stephen P.
Published: December 2013

The purpose of this study is to analyze structural properties of biomass materials, namely corn stover. The structural properties of the biomass corn stover are examined at macro and fiber levels by performing a series of tests including three-point bending and tensile strength. Results of the stated tests are statistically analyzed. The goal of this analysis is to test the strength under loading from various directions to gather a full understanding of the structural properties of corn stalk fibers. Tests are performed using universal testing machines (UTMs). The results of these studies will be used to compile a database of the structural properties of biomass. These properties have the potential to be used in finite element computer simulations for structural analysis and bulk solid flows. The bulk fluid motion of the pulverized/chopped biomass can be simulated in storage and transportation equipment, including auguring screws and pneumatic conveyance systems, as well as devices for feeding biomass feedstocks in biorefineries. Traditional biochemical and thermochemical reactors operate as batch systems because of the difficulty of feeding the biomass feedstock in a continuous manner. Having a clearer background about the structural and rheological properties of biomass feedstock will help simulate and design the bulk-solid flows within storage bins and conveyance systems.
Electric Vehicle Improved by Three-Phase Asynchronous Cooled Motor
Authors: Rattighieri Giuseppe , Trancossi Michele , Dorigo Salomon Nicola , Vucinic Dean
Published: December 2013

This paper presents the EVITA electric car. EVITA is the acronym of Electric Vehicle Improved by Three-phase Asynchronous cooled motor. It is a research project developed jointly by RGEngineering and University of Modena and Reggio Emilia. It aims to produce a novel electric power train with the capability of solving three fundamental problems of today commercial electric vehicles:

1. direct torque dependency of the rotation speed, and its reduction at high speed regimes;

2. electric motors performances reduction due to the overheating effects under heavy load conditions;

3. acclimatization of the car cabin interior in winter times.
Optical Analysis of a Window for Solar Receivers Using the Monte Carlo Ray Trace Method
Authors: Mecit Ahmet Murat , Miller Fletcher
Published: December 2013

Concentrated solar power (CSP) systems use heliostats to concentrate solar radiation in order to produce heat, which drives a turbine to generate electricity. We, the Combustion and Solar Energy Laboratory at San Diego State University, are developing a new type of receiver for power tower CSP plants based on volumetric absorption by a gas-particle suspension. The radiation enters the pressurized receiver through a window, which must sustain the thermal loads from the concentrated solar flux and infrared reradiation from inside the receiver. The window is curved in a dome shape to withstand the pressure within the receiver and help minimize the stresses caused by thermal loading. It is highly important to estimate how much radiation goes through the window into the receiver and the spatial and directional distribution of the radiation. These factors play an important role in the efficiency of the receiver as well as window survivability.

Concentrated solar flux was calculated with a computer code called MIRVAL from Sandia National Laboratory which uses the Monte Carlo Ray Trace (MCRT) method. The computer code is capable of taking the day of the year and time of day into account, which causes a variation in the flux. Knowing the concentrated solar flux, it is possible to calculate the solar radiation through the window and the thermal loading on the window from the short wavelength solar radiation. The MIRVAL code as originally written did not account for spectral variations, but we have added that capability.

Optical properties of the window such as the transmissivity, absorptivity, and reflectivity need to be known in order to trace the rays at the window. A separate computer code was developed to calculate the optical properties depending on the incident angle and the wavelength of the incident radiation by using data for the absorptive index and index of refraction for the window (quartz) from other studies and vendor information. This method accounts for regions where the window is partially transparent and internal absorption can occur.

A third code was developed using the MCRT method and coupled with both codes mentioned above to calculate the thermal load on the window and the solar radiation that enters the receiver. Thermal load was calculated from energy absorbed at various points throughout the window. In our study, window shapes from flat to concave hemispherical, as well as a novel concave ellipsoidal window are considered, including the effect of day of the year and time of the day.
Analysis of Food Waste Resources Available for Sustainable Energy Production in the Finger Lakes Region of New York State
Authors: Chan Wai Hon , Ebner Jacqueline , Ramchandra Rajiv , Trabold Thomas
Published: December 2013

Prior research conducted by our Institute has revealed the large quantities of food waste available in New York State, particularly in the Upstate corridor extending from Buffalo to Syracuse. The Finger Lakes region is heavily populated with agricultural operations, dairy farms and food processing plants, including those producing milk, yogurt, wine, and canned fruits and vegetables. The diverse supply of organic waste generated by these facilities offers the opportunity for sustainable energy production through one of three primary pathways:

• Anaerobic digestion to produce methane

• Fermentation to produce alcohols

• Transesterification to produce biodiesel.

Generally speaking, food wastes are better suited for biochemical conversion instead of thermo-chemical conversion (combustion, gasification, pyrolysis) due to their relatively high moisture content. The current paper provides an initial assessment of food wastes within the 9-County Finger Lakes region around Rochester, New York. Available databases were utilized to first identify all the relevant companies operating in one of four broad industry sectors: agriculture, food processing, food distribution and food services (including restaurants). Our analysis has demonstrated that anaerobic digestion can be a viable method for sustainable energy production from food waste in the Finger Lakes region, due to the dual economic benefits of effective disposal cost reduction and production of methane-rich biogas.
Dome Window Geometry for a Large Scale Solar Receiver
Authors: Saung E-Fann , Miller Fletcher
Published: December 2013

Windows are being evaluated for use in some high temperature solar receivers to reduce radiative and convective losses. The design process of a 1.7 meter diameter quartz dome window is explained to arrive at a window geometry able to maintain acceptable stresses when exposed to pressure differentials. The dome must be able to withstand the operational differential pressures of 0.5 MPa where the efficiency of the solar receiver/power cycle is maximized, and maximum temperatures upwards to 800°C may be observed. Brittle materials like glass need the tensile stresses to be reduced or eliminated to maximize the reliability of the dome window. However, glass does not possess a consistent characteristic strength and it is dependent on the flaw size. The dome mount is critical to maintaining an environmental seal, but careful attention must be taken in the glass-metal interface to minimize tensile bending stresses that can cause a catastrophic or rapid failure.

A method to characterize the strength of the quartz dome is discussed and aides in determining the maximum design stresses allowable during operation of the solar receiver. To determine an accurate model of the dome stress, a statistical analysis based on strength data has been carried out using the Weibull failure probability method. Finite Element Analysis (FEA) analysis of the dome is discussed, and a design trade study of the dome window geometry (ranging from a shallow angle to a full hemisphere) is presented. The combination of these perspectives will give insight on the process to design a glass dome window for this challenging environment and to predict the reliability.
Modelling of an Indirect Solar-Assisted Heat Pump System for a High Performance Residential House
Authors: Chu Jenny , Cruickshank Cynthia A. , Choi Wilkie , Harrison Stephen J.
Published: December 2013

Heat pumps are commonly used for residential space-heating and cooling. The combination of solar thermal and heat pump systems as a single solar-assisted heat pump (SAHP) system can significantly reduce residential energy consumption in Canada. As a part of Team Ontario’s efforts to develop a high performance house for the 2013 DOE Solar Decathlon Competition, an integrated mechanical system (IMS) consisting of a SAHP was investigated. The system is designed to provide domestic hot water, space-heating, space-cooling and dehumidification. The system included a cold and a hot thermal storage tank and a heat pump to move energy from the low temperature reservoir, to the hot. The solar thermal collectors supplies heat to the cold storage and operate at a higher efficiency due to the heat pump reducing the temperature of the collector working fluid. The combination of the heat pump and solar thermal collectors allows more heat to be harvested at a lower temperature, and then boosted to a suitable temperature for domestic use via the heat pump. The IMS and the building’s energy loads were modeled using the TRNSYS simulation software. A parametric study was conducted to optimize the control, sizing and configuration of the system. This paper provides an overview of the model and summarizes the results of the study. The simulation results suggested that the investigated system can achieve a free energy ratio of about 0.583 for a high performance house designed for the Ottawa climate.
Compensation of Gravity Induced Heliostat Deflections for Improved Optical Performance
Authors: Yuan James K. , Christian Joshua M. , Ho Clifford K.
Published: December 2013

Heliostat optical performance can be affected by both wind- and gravity-induced deflections in the mirror support structure. These effects can result in decreased energy collection efficiency, depending on the magnitude of structural deflections, heliostat orientation and field position, and sun position. This paper presents a coupled modeling approach to evaluate the effects of gravity loading on heliostat optical performance, considering two heliostat designs: The National Solar Thermal Test Facility (NSTTF) heliostat and the Advanced Thermal Systems (ATS) heliostat. Deflections under gravitational loading were determined using finite element analysis (FEA) in ANSYS Mechanical, and the resulting deformed heliostat geometries were analyzed using Breault APEX optical engineering software to evaluate changes in beam size and shape. Optical results were compared against images of actual beams produced by each respective heliostat, measured using the Beam Characterization System (BCS) at Sandia National Laboratories. Simulated structural deflections in both heliostats were found to have visible impacts on beam shape, with small but quantifiable changes in beam power distribution. In this paper, the combined FEA and optical analysis method is described and validated, as well as a method for modeling heliostats subjected to gravitational deflection but canted in-field, for which mirror positions may not be known rigorously. Furthermore, a modified, generalized construction method is proposed and analyzed for the ATS heliostat, which was found to give consistent improvements in beam shape and up to a 4.1% increase in Annual Incident Power Weighted Intercept (AIPWI).
Economic Analysis of Solar PV and Batteries for Common Residential Electricity Rate Structures Using Green Button Data
Authors: Nagabhairava Mithun Mohan , Ma Yin , Kissock Kelly
Published: December 2013

Rising electricity prices, falling photovoltaic (PV) system costs and the availability of net metering are encouraging consumers to consider PV systems. However, the variety and complexity of utility rate structures can be a formidable barrier to consumers in making economically informed decisions. This paper describes a methodology to integrate Green Button energy use data from electric utilities, with solar and temperature data to analyze the economics of PV systems, with and without battery storage, under different rate structures. Case study results indicate that the economics of PV systems are nearly identical under PG&E’s time-of-use and inverted-block rate structures, and are more favorable than under flat rate structures with the same average annual cost per kWh. However, simple paybacks remain well short of the typical life of PV systems. The simple payback for the addition of batteries is initially competitive with PV systems, but rises rapidly as battery size is increased.
Synthesis and Analysis of Cobalt Ferrite in YSZ for Use as Reactive Material in Solar Thermochemical Water and Carbon Dioxide Splitting
Authors: Allen Kyle M. , Klausner James F. , Coker Eric N. , AuYeung Nick , Mishra Rishi
Published: December 2013

This paper reports the synthesis, characterization and evaluation of different weight loadings of cobalt ferrite (CoFe2O4) in 8 mol% yttria-stabilized zirconia (8YSZ) via the co-precipitation method. Prepared powders were calcined at 1350 °C for 36 hours and 1450 °C for 4 hours in air. These powders were then formed into a porous structure using sacrificial pore formation via oxidation of co-mixed graphite powder. These formed structures obtained were then characterized using thermogravimetric analysis (TGA), X-ray diffraction (XRD), high temperature X-ray diffraction (HT-XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Brunauer-Emmett-Teller (BET) surface area analysis was performed on the most promising of the structures before being subjected to 50 thermal reduction-CO2 oxidation (redox) cycles using TGA. Together, these results indicate that CoFe2O4-8YSZ can provide a lower reduction temperature, maintain syngas production performance from cycle to cycle, and enhance utilization of the reactive material within the inert support in comparison to iron oxide only structures.
Carbon Dioxide Emission Reduction Potentials in West Virginia’s Power Generation Sector
Authors: Zabihian Farshid , Gartin Darrel C. , Fung Alan S.
Published: December 2013

In this paper, research will be discussed on how to scientifically, systematically, and economically reduce greenhouse gas emissions within the state of West Virginia, USA. While fossil fuels such as coal and natural gas remain the top resources within this particular state, there are new technologies, different approaches and modifications to current power generation cycles, and different fuels that can be presented to gain further reduction of these harmful emissions.

To achieve this objective, eight different scenarios were introduced. In the first scenario, existing power stations’ fuel was switched to natural gas. Existing power plants were replaced by natural gas combined cycle (NGCC), integrated gasification combined cycle (IGCC), solid oxide fuel cell (SOFC), hybrid SOFC, and SOFC-IGCC hybrid power stations in scenarios number 2 to 6, respectively. The last two scenarios involved carbon capture systems. It has been found that the CO2 emissions can be significantly reduced by introducing changes and alternatives to the current cycles and methods that are in place today.
The Engineering Practice of a CCHP System With the Condensation Heat Recovery of the Flue Gas in China
Authors: Zhao Xiling , Fu Lin , Wang Xiao
Published: December 2013

As an energy-saving and environmentally friendly technology, the combined cooling heating and power system (CCHP) had been applied in the field of heating and air conditioning. Chinese researchers recently designed a CCHP system with the condensation heat recovery of the flue gas, which composed of a gas-powered internal combustion engine (ICE), an exhaust-gas-driven absorption heat pump (AHP), a flue gas condensation heat exchanger (CHE), and other assistant facilities, such as pumps, fans, and end user devices. The system was built and operated in 2011. We tested the parameters of the system on the heating and cooling status from the ICE to the CHE, including the temperature and flux of water, the inlet and outlet parameters of different facilities, and the performance of different facilities for a typical operation status. Based on the test results, the overall COP of the system in the heating and cooling mode was computed, and the energy efficiency level was analyzed. The results indicated that the energy utilization efficiency is about 94% on the heating status, and the energy utilization efficiency is about 84% on the cooling status. These results could serve as a reference for designing or evaluating the CCHP systems.