bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Simulation of Stress Relief of Buried Pipeline at Pembina River Crossing
Authors: Song Bing , Cheng J. J. Roger , Chan Dave H. , Zhou Joe
Published: October 2008

Pipelines in operation often experience various loadings due to operational and environmental conditions. Large strain may be accumulated in the pipes under these loadings, and it may eventually induce local buckling or even fractures on the pipes. It is a common practice that a stress relief procedure is applied to a pipe by removing the soil around the pipe, allowing the pipe to spring back to a zero load state. The frequency of stress relief procedure is dependent on the severity of loading and soil conditions. This project is intended to study the behavior of buried pipes subjected to repeated stress relief procedures. The buried pipeline at Pembina River Crossing in Lodgepole, Alberta was simulated using the finite element method and the results were compared with field measured data. The pipeline at Pembina River Cross is situated at the active soil movement locations. A finite element model was developed to simulate the slope movement and the pipeline response. The correlation between soil movement and precipitation was investigated. With shell elements for pipe, 3D-solid elements for soil, this model captures the global and local behavior of pipeline. Soil-pipe interaction was simulated by setting a weak layer of soil surrounding the pipeline. The model incorporates nonlinear material, slope soil creep and water table change. Modified Drucker-Prager Cap Model was applied to soils based on direct shear test results. The finite element model was calibrated by slope indicator data and strain gauge data with satisfactory agreement. The model was used to simulate the strain accumulation and the stress relief in the pipeline, before and after the stress relief operation. Reasonable agreement was achieved when compared to the field data. The model can be used to further understand the behavior of pipe under repeated soil movement and stress relief procedure. It can also be used to develop the optimum stress relief procedure and operating schedule.
Best Practices for Pipeline Management: Shaan-Jing Pipeline Integrity Management and Practice
Authors: Dong Shohua , Gu Bill , Yao Wei
Published: October 2008

Pipeline integrity management is essential for today’s operators to operate their pipelines both in a safe and cost effective manner. Around the world, the latest developments of pipeline integrity management are driven by changes in regulation, industry standards and the latest innovations in technology. Beijing Huayou Gas Company (BHGC) is a pioneer in the Chinese pipeline industry through its implementation of pipeline integrity management and utilization of the latest developed technologies such as in-line inspection (ILI), Geographic Information Systems (GIS), risk assessments and advanced repair technologies. By using smart pigging inspections combined with GIS and EAM (Enterprise Assets Management) on 1,000 km of Shaanxi-Beijing gas pipeline, BHGC is able to manage the pipeline’s integrity in five areas, pipe materials safety, natural and geotechnical hazards management, coating and corrosion protection, stationing plus associated facilities maintenance and underground gas storage integrity. This paper describes the latest achievements of BHGC in their pipeline integrity programs.
Experimental Setup for Full-Scale Testing of Pipes Under Combined Loads
Authors: Ozkan Istemi F. , Mohareb Magdi
Published: October 2008

A versatile experimental setup was recently built at the University of Ottawa Structural Laboratory with the capability of testing full-scale pipes under load combinations involving axial tensile/compressive force, twist, shear, internal pressure, and imposed bending deformations. This paper presents the innovative aspects of the new experimental setup and documents some aspects of the deformational behavior of pipe specimen of X65 material, 20 in. OD with a diameter to thickness ratio of 80, under the combined action of internal pressure, axial tensile force, torsion, and imposed curvature, which was recently conducted under the new setup. The results reported are part of a testing program, which is currently underway.
Optimization of UOE Pipe Manufacturing Process for Improved Collapse Performance Under External Pressure
Authors: Kyriakides Stelios , Herynk Mark D. , Yun Heedo
Published: October 2008

Large-diameter pipes used in offshore applications are commonly manufactured by cold-forming plates through the UOE process. Collapse experiments have demonstrated that these steps, especially the final expansion, degrade the mechanical properties of the pipe and result in a reduction in its collapse pressure, upwards of 30%. In this study, the UOE forming process has been modeled numerically so that the effects of press parameters of each forming step on the final geometry and mechanical properties of the pipe can be established. The final step involves simulation of pipe collapse under external pressure. An extensive parametric study of the problem has been conducted, through which ways of optimizing the process for improved collapse performance have been established. For example, it was found that optimum collapse pressure requires a tradeoff between pipe shape (ovality) and material degradation. Generally, increase in the O-strain and decrease in the expansion strain improve the collapse pressure. Substituting the expansion by compression can not only alleviate the UOE collapse pressure degradation but can result in a significant increase in collapse performance.
Performance Analysis of Thermocline Energy Storage Proposed for the 1 MW Saguaro Solar Trough Plant
Authors: Kolb Gregory J. , Hassani Vahab
Published: October 2008

The 1 MW Saguaro solar parabolic trough power plant began operation in December 2005. The plant will initially operate without an energy storage system. However, recent studies predict a thermocline-type storage should be the most cost-effective storage concept for solar parabolic troughs power plants. If such a system can be successfully demonstrated at Saguaro, future trough plants will likely adopt this storage technology. A thermocline storage system for Saguaro has been proposed by Department of Energy (DOE) laboratories and the solar industry. In this paper, the time-dependent performance of the proposed storage system was evaluated with a new model of the plant based on the TRNSYS simulation system. Results indicate that the proposed system should work well at Saguaro. The paper describes the TRNSYS model and the engineering insights gleaned from annual performance simulations of the plant.
China Energy Label: A Strategy to Encourage Energy Conservation and the Challenge Ahead in Power Markets
Authors: Yu Zhun , Xie Yingbai , Jing Youyin , Shi Guohua
Published: October 2008

This paper aims to elucidate China energy label and «The minimum allowable values of the energy efficiency and energy efficiency grades for room air conditioners» implemented recently (2005). Energy efficiency ratio (EER) considered in this standard was compared with coefficient of performance (COP), based on it, two air-conditioners with different EER were calculated to be contrasted by their total cost during the operational life. At the same period, the content, significance and result of the energy standard was analyzed. The results show that air-conditioners with higher EER can be more economical, and they can obtain better qualities as well as utilization effects. Also, this standard determines the energy efficiency grade index of room air-conditioners below 14 kW and the market entrance admission index of energy efficiency. Starting this standard requires that each air-conditioner should have an energy label, thus market transformation goals can be achieved, consequently, it will accelerate the advancement of enterprises and reinforce the energy-saving management of the government. However, designers, manufacturers and high efficiency product sellers in the power market will be challenged.
Airflow Distribution and Microenvironment Evaluation of CMP Task Conditioning System
Authors: Jing Youyin , Zheng Guozhong
Published: October 2008

Microenvironment of a typical office workplace consisting computer monitor panel (CMP) task conditioning systems was studied by numerical simulation. Two CMP task conditioning systems were operated while a conventional HVAC system supplied air through a diffuser located in the ceiling. Air was exhausted through a ducted ceiling-level grill. Numerical simulation by k-ε 3-D turbulent model was conducted to study the influence of supply velocity on microenvironment of CMP task conditioning system. Three task conditioning velocities, 0.8, 1.0 and 1.2 m/s were studied Temperature and velocity distribution, Draught Rating (DR) and Predicted Percentage of Dissatisfied (PPD) of the room and workstation were studied. Results showed that room temperature was distributed by region, and occupant was exactly in supplying area. Temperature around occupant was apparently lower than surrounding temperature. So task conditioning had high air-supplying efficiency. Results also showed that task conditioning can provide excellent working environment when supply velocity were well designed. Task conditioning may cause draught according to conventional thermal comfort standard. When supply velocity is 1.0 or 1.2 m/s, DR around head reached 25 or 30 and PPD reached 12 or 15, so it may be uncomfortable to occupant. However occupant can control supply velocity and air blowing distance of task conditioning system to maintain acceptable thermal comfort. To summarize, flexible control of task conditioning system can create a more comfortable indoor environment.
Energy Grade Balance of Gas Engine-Driven Heat Pump
Authors: Xie Yingbai , Liu Chuntao , Yu Zhun
Published: October 2008

Gas Engine-driven heat pump (GEHP) is the compressed heat pump driven by gas engine. For an R-134a GEHP system at 2°C evaporator and 50°C condensing temperature, analyses based on the first law of thermodynamics, exergy and energy grade are processed. Comparing to other heating devices, such as electric driven heat pump, coal fired boiler, electric boiler and gas fired boiler, GEHP has higher performances, the primary energy ratio (PER) of which is 1.76, the exergy efficiency is 0.291 and the energy grade balance efficiency is 0.394. The results of the energy grade balance analysis are consistent with that of the first law thermodynamics analysis and the exergy analysis. Since the anergy plays an important role when heat pump extracts heat from the surroundings, energy grade balance analysis, which takes into account the anergy, is suggested to evaluate the performance of heat pump.
A 300 kW Solar Chemical Pilot Plant for the Carbothermic Production of Zinc
Authors: Wieckert C. , Guillot E. , Epstein M. , Olalde G. , Sante´n S. , Frommherz U. , Kra¨upl S. , Osinga T. , Steinfeld A.
Published: October 2008

In the framework of the EU-project SOLZINC, a 300 kW solar chemical pilot plant for the production of zinc by carbothermic reduction of ZnO was experimentally demonstrated in a beam-down solar tower concentrating facility of Cassegrain optical configuration. The solar chemical reactor, featuring two cavities, of which the upper one is functioning as the solar absorber and the lower one as the reaction chamber containing a ZnO/C packed bed, was batch-operated in the 1300–1500 K range and yielded 50 kg/h of 95%-purity Zn. The measured energy conversion efficiency — ratio of the reaction enthalpy change to the solar power input — was 30%. Zinc finds application as a fuel for Zn-air batteries and fuel cells, and can also react with water to form high-purity hydrogen. In either case, the chemical product is ZnO, which in turn is solar-recycled to Zn. The SOLZINC process provides an efficient thermochemical route for the storage and transportation of solar energy in the form of solar fuels.
Hydrogen Production by Steam-Gasification of Petroleum Coke Using Concentrated Solar Power: Reactor Experimentation With Slurry Feeding
Authors: Z’Graggen Andreas , Haueter Philipp , Maag Gilles , Vidal Alfonso , Romero Manuel , Steinfeld Aldo
Published: October 2008

We report on the experimental evaluation of a 5 kW solar chemical reactor for the steam-gasification of petcoke, carried out at PSI’s solar furnace. A petcoke-water slurry was continuously injected into a solar cavity-receiver to create a vortex flow directly exposed to concentrated solar radiation. For a nominal reactor temperature of 1500 K, a residence time of 2.4 s, and a water-petcoke molar ratio of 4.8, the maximum degree of petcoke conversion was 87%. Typical syngas composition produced was 62% H2, 25% CO, 12% CO2, and 1% CH4. The energy conversion efficiency — defined as the portion of solar energy absorbed as chemical energy and sensible heat — attained 17%. The effect of varying the particle size (range 8.5–200 μm) and slurry stoichiometry (range 2.1–6.3) on the degree of chemical conversion and energy conversion efficiency was examined.
Monitoring and Measurement of Thermal Performance of Solar Heated Outdoor Swimming Pools With Different Covers
Authors: Anunciada-Santos A. , Gomes-Sousa C. , Lillo Bravo Isidoro , Ruiz Herna´ndez Valeriano
Published: October 2008

A comparative analysis of the performances of three outdoor swimming pools for private use with different types of covers is presented in this paper. They are designed to take advantage of solar irradiation to maintain the swimming pool temperature within certain acceptable limits, so that the swimming pool can be used during most of the year under South-Europe climatic conditions. In this region, the annual global irradiation is of the order of 1800 kWh/m2 and air temperature is in the range from 0°C to 40°C during the whole year. No auxiliary boosting is used to heat the swimming pools.
Double-Focus Configuration at DLR Solar Furnace for Operating a Continuous Reactor
Authors: Neumann Andreas , Willsch Christian , Roeb Martin , Graf Daniela , Sattler Christian
Published: October 2008

The DLR Solar Furnace in Cologne is a facility that concentrates solar radiation for research experiments. It offers many different possibilities of using concentrated solar radiation to scientists and industrial users. Most of the experiments are from the research fields ‘Solar Chemistry’, ‘Solar Thermal’, and ‘Material Research’. In a recent experiment series the solar thermal hydrogen production is investigated. This experiment is based on a two-step thermochemical water splitting process. In the first step steam is decomposed by a low-valence metal oxide coated on a ceramic support at 800°C, leading to hydrogen and a higher valence state of the metal oxide. In the second regeneration step the oxygen is released from the metal oxide using an inert purge gas and a temperature range of 1100–1200°C. In the new concept two reaction chambers had the task to perform a quasi-continuous process, having one reactor in the hydrogen production mode, and the other in the regeneration mode. The DLR Solar Furnace usually generates a single high flux focal spot. For the new approach we had to realign the concentrator in order to get two focal spots. Both of them had to have the same power and beam shape. Furthermore, a power regulation was necessary for both focal spots, as the two process steps needed different temperature levels and therefore a temperature control option.
CFD Modeling of Gas Particle Flow Within a Solid Particle Solar Receiver
Authors: Chen Huajun , Chen Yitung , Hsieh Hsuan-Tsung , Siegel Nathan
Published: October 2008

A detailed three dimensional computational fluid dynamics (CFD) analysis on gas-particle flow and heat transfer inside a solid particle solar receiver, which utilizes free-falling particles for direct absorption of concentrated solar radiation, is presented. The two-way coupled Euler-Lagrange method is implemented and includes the exchange of heat and momentum between the gas phase and solid particles. A two band discrete ordinate method is included to investigate radiation heat transfer within the particle cloud and between the cloud and the internal surfaces of the receiver. The direct illumination energy source that results from incident solar radiation was predicted by a solar load model using a solar ray tracing algorithm. Two kinds of solid particle receivers, each having a different exit condition for the solid particles, are modeled to evaluate the thermal performance of the receiver. Parametric studies, where the particle size and mass flow rate are varied, are made to determine the optimal operating conditions. The results also include detailed information for the particle and gas velocity, temperature, particle solid volume fraction, and cavity efficiency.
Preparations and Photovoltaic Properties of Thin Films Using Soluble Fulleropyrrolidine Derivatives for Organic Solar Cells
Authors: Kim Mi-Ra , Shin Won Suk , Jin Sung-Ho , Fujida Kastuhiko , Tsutsui Testuo , Lee Jin-Kook
Published: October 2008

Organic solar cells made from bi-layer thin-film heterojunctions having poly((2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene)vinylene) (MEH-PPV) as an electron donor and fulleropyrrolidine derivatives as an electron acceptor were investigated. We synthesized soluble fulleropyrrolidine derivatives substituted different chain lengths for the organic solar cell. Due to the high solubility and sufficiently long chain length of fulleropyrrolidine derivatives, though those are monomers, a thin film (about 50 nm) could be fabricated individually by the spin-coating method. The fill factor of the bi-layer device was achieved to be 0.40, which is higher than that of the single-layer device by a polymer/fulleropyrrolidine derivative blend film of 0.29, due to the decrease of the recombination.
Solid-State Dye-Sensitized Solar Cells Using Conducting Polymers as Hole Transporting Materials
Authors: Kim Mi-Ra , Lee Seung-Yeop , Yeo Yun-Seon , Cho Yong-Rae , Park Sung-Hae , Shin Won Suk , Jin Sung-Ho , Jung Ki-Suck , Han Sang Min , Lee Jin-Kook
Published: October 2008

Thiophene-based polymers have good prospects in the field of electronic and photoelectronic devices because of their solubility, processability, environmental stability, and excellent electrical conductivity. We synthesized new type of thiophene-based polymers to use as hole transporting materials on dye-sensitized solar cells (DSSC). The thiophene-based polymers were synthesized as random copolymers containing 3-{2-[2-(2-(4-methoxybiphenyl)ethoxy)ethoxy]ethoxy}methylthiophene (MEET) units and 3-hexylthiophene (3HT) units. The photovoltaic performance of the solid-state DSSC device was improved to 3.88% overall efficiency under AM 1.5 illumination when the thiophene-based copolymer was introduced to the electrolyte as a hole transporting material.
An Improvement in the Solar Water Heating Systems by Thermal Storage Using Phase Change Materials
Authors: Vikram D. , Kaushik S. , Prashanth V. , Nallusamy N.
Published: October 2008

The present work has been undertaken to study the feasibility of storing solar energy using phase change materials (like paraffin) and utilizing this energy to heat water for domestic purposes during nighttime. This ensures that hot water is available through out the day. The system consists of two simultaneously functioning heat-absorbing units. One of them is a solar water heater and the other a heat storage unit consisting of Phase Change Material (PCM). The water heater functions normally and supplies hot water during the day. The storage unit stores the heat in PCMs during the day and supplies hot water during the night. The storage unit utilizes small cylinders made of aluminium, filled with paraffin wax as the heat storage medium and integrated with a Solar Collector to absorb solar heat. At the start of the day the storage unit is filled with water completely. This water is made to circulate between the solar collector and the PCM cylinders. The water in the storage tank receives heat form the solar collector and transfers it to the PCM. The PCM undergoes a phase change by absorbing latent heat, excess heat being stored as sensible heat. The water supply in the night is routed to the storage unit using a suitable control device. The heat is recovered from the unit by passing water at room temp through it. As water is drawn from the overhead tank, fresh water enters the unit disturbing the thermal equilibrium, causing flow of heat from PCM to the water. The temperature of the heated water (outlet) is varied by changing the flow rate, which is measured by a flow meter. The storage tank is completely insulated to prevent loss of heat. The performance of the present setup is compared with that of a system using same PCM encapsulated in High Density PolyEthylene (HDPE) spherical shells.
Some Alternative Technologies for Solar Thermal Power Generation
Authors: Utamura Motoaki , Tamaura Yutaka , Hasuike Hiroshi
Published: October 2008

Two advanced optical systems and a highly efficient thermal cycle suitable for beam-down power tower with thermal storage are presented. (1) To increase field efficiency, the “cross beam” heliostat array concept is proposed. Using continuum optical model, the characteristics of the cross beam concept and its economy were investigated. (2) To protect the central reflector (CR) against wind force, a “multi-ring CR” concept is proposed. The concentration performance of multi-ring CRs is calculated using the ray-tracing method. It shows no worse results than the case with a single hyperboloid mirror. (3) The potential of a closed gas turbine cycle with supercritical carbon dioxide as a working fluid was investigated. An optimal cycle configuration involves a regenerative cycle with pre-cooling and inter-cooling cycles, in which theoretically achievable cycle thermal efficiency is 47% at the turbine inlet temperature of 800 K and turbine inlet pressure of 20 MPa. Detailed thermal design of a critical component, regenerative heat exchanger (RHX) is carried out using a newly developed printed heat exchanger (PCHE). It proved to be a feasible design.
Green Development in Turkey
Authors: So¨zer Hatice
Published: October 2008

This paper introduces a proposal for the architectural design of development for 20 town houses in the city of Nigde, located on central Turkey. The municipality of Nigde is looking for an innovative design for the town houses, that will achieve maximum level of desired comfort, but will adhere to energy conservation and minimum construction cost. These houses, however, while incorporating contemporary technologies, has to preserve the legacy of the great architectural heritage. The city of Nigde has a very rich history and consists of multicultural settlements. Unfortunately only few buildings are still standing to tell that great story; and the new buildings in Nigde do not stand up to the challenge. The site’s topography adds visual interest and variety to the project’s housing. The climate is dominated by lack of humidity, big differences between day and night time temperatures.
Experimental Characterization of a Natural Convection Heat Exchanger for Solar Domestic Hot Water Systems
Authors: Cruickshank Cynthia A. , Harrison Stephen J.
Published: October 2008

To predict the long-term performance of solar domestic hot water (SDHW) systems requires computational models that can characterize the systems under a range of operating conditions. The development of detailed fundamental models that suitably describe the operation of systems with natural convection heat exchangers is, however, difficult and time consuming. The fact that the natural convection flow through the heat exchanger is intrinsically self-controlling and temperature dependent complicates the analysis. One approach to modeling this type of system is to use performance characteristics, empirically derived from experimental data, to predict the performance of the heat exchanger under typical operating conditions. Unfortunately, a significant number of tests may be required to characterize the full operation of the device. This paper presents a simplified test method that was developed to allow pre-configured SDHW systems that use natural convection heat exchangers, to be characterized. The results of this test method produce performance coefficients for simple empirical expressions that describe the fluid flow and heat transfer in the heat-exchange loop. These empirically derived coefficients are an input to a general simulation routine that allows overall system performance to be determined for various loads and climatic conditions. In this paper, data is presented for a typical heat exchanger under a range of operational conditions.
Evaluation of Energy Savings by Optimization Control in Thermal Energy Storage System
Authors: Seo Donghyun , Krarti Moncef
Published: October 2008

By using both passive and active thermal energy storage (TES) systems, a significant portion of the on-peak cooling can be shifted to the off-peak period and thus the energy costs associated can be considerably reduced. This paper summarizes the results of a comprehensive evaluation of the performance of optimal and conventional control strategies for combined passive (i.e., pre-cooling building thermal mass) and active (i.e., charging ice storage tanks) TES systems for typical commercial buildings in the US. Specifically, the paper examines the impact of selected design and operating factors on the performance of optimal control strategies for combined passive and active TES systems. Among the factors analyzed include building shape, climate, adaptation of optimization control, TES systems control, and utility rate structure. The analysis is performed using a detailed simulation energy program (EnergyPlus) modified to incorporate TES models and various optimization algorithms. The results of the analysis indicate that optimal TES priority controls can achieve up to 35% in on-peak electricity demand reduction and up to 30% in total electrical energy cost savings.
Design and Construction of the APS 1-MWe Parabolic Trough Power Plant
Authors: Canada Scott , Brosseau Doug A. , Price Henry
Published: October 2008

Arizona Public Service (APS) is currently installing and operating new power facilities to generate a portion of its electricity from solar resources that will satisfy its obligation under the Arizona Environmental Portfolio Standard. During FY04, APS began construction on a 1-MWe parabolic trough concentrating solar power plant. Site preparation and construction activities continued throughout FY05 and early FY06. Construction was completed and initial startup occurred by the end of December 2005. Full power production and initial performance monitoring and evaluation will occur early in 2006. This project is the first commercial deployment of parabolic trough collector technology developed by Solargenix Energy, Inc. of Raleigh, North Carolina. The plant, located near Red Rock, Arizona, uses an organic Rankine cycle power plant by Ormat, which is much simpler than conventional steam Rankine cycles and allows unattended operation of the facility. APS has teamed with the National Renewable Energy Laboratory and Sandia National Laboratories (collectively called SunLab), along with Nexant, Inc. to support design and startup activities and performance assessment. SunLab has developed TRNSYS models of the plant and will utilize initial performance baseline data to validate the models. Eventually, those models will be used to determine whether a proposed thermocline energy storage system designed by Nexant, Inc. is technically and economically feasible for this plant. SunLab has also assisted APS with development of an O&M database using the Maximo system to track solar plant costs and component failure modes.
Numerical Modeling of Solar Thermo-Chemical Water-Splitting Reactor
Authors: James Darryl L. , Siegel Nathan P. , Diver Richard B. , Boughton Barry D. , Hogan Roy E.
Published: October 2008

Production of hydrogen using solar thermal energy has the potential to be a viable alternative to other hydrogen production methods, typically fossil-fuel driven processes. Thermochemical reactions for splitting water require high temperatures to operate effectively, for which solar is well-suited. Numerical modeling to investigate the concept of a solar-driven reactor for splitting water is presented in detail in this paper for an innovative reactor, known as the “counter-rotating-ring receiver/reactor/recuperator” (CR5) solar thermochemical heat engine that is presently under development. In this paper, details of numerical simulations predicting the thermal/fluid behavior of the innovative solar-driven thermo-chemical reactor are described in detail. These scoping calculations have been used to provide insight into the thermal behavior of the counter-rotating reactor rings and to assess the degree of flow control required for the CR5 concept.
Solar Thermochemical Water-Splitting Ferrite-Cycle Heat Engines
Authors: Diver Richard B. , Miller James E. , Allendorf Mark D. , Siegel Nathan P. , Hogan Roy E.
Published: October 2008

Thermochemical cycles are a type of heat engine that utilize high-temperature heat to produce chemical work. Like their mechanical work-producing counterparts, their efficiency depends on operating temperature and on the irreversibilities of their internal processes. With this in mind, we have invented innovative design concepts for two-step solar-driven thermochemical heat engines based on iron oxide and iron oxide mixed with other metal oxides (ferrites). These concepts utilize two sets of moving beds of ferrite reactant material in close proximity and moving in opposite directions to overcome a major impediment to achieving high efficiency – thermal recuperation between solids in efficient counter-current arrangements. They also provide inherent separation of the product hydrogen and oxygen and are an excellent match with high-concentration solar flux. However, they also impose unique requirements on the ferrite reactants and materials of construction as well as an understanding of the chemical and cycle thermodynamics. In this paper, the Counter-Rotating-Ring Receiver/Reactor/Recuperator (CR5) solar thermochemical heat engine concept is introduced and its basic operating principals are described. Preliminary thermal efficiency estimates are presented and discussed. Our results and development approach are also outlined.
Design of Photovoltaic-Powered Refrigeration for Tropical Climates
Authors: Kassels Seth M. , Brandemuehl Michael J.
Published: October 2008

The increased global demand for energy will generate a growing need to electrify rural populations. Photovoltaic systems are being considered for many rural areas in the tropics. The development of photovoltaic-powered refrigeration will provide access to food preservation, which will result in improved health conditions. The over-arching objective of this investigation is to develop a properly designed, cost effective and energy efficient photovoltaic-powered refrigerator for tropical climates. The specific objectives of this investigation are to develop a design methodology and evaluate design variables for a photovoltaic system and refrigeration unit for tropical climates (high heat, low sun) that can be manufactured at relatively low costs. The price goal for the refrigerator and photovoltaic system is $1,000 retail. The investigation was accomplished through a five-step process: 1) background engineering and market research, 2) modeling, 3) model verification, 4) hourly simulation, and 5) cost analysis. Results indicate that over-sizing the condenser and the extreme insulation of the refrigeration unit reduced the overall cost of the refrigerator and photovoltaic system. Also, the investigation demonstrated that proper design of the photovoltaic system is the key to determining the refrigerator’s ability to perform in harsh climates.
Implementing Solar Energy in the Colorado Production Home Market
Authors: Lyng Jeffrey R. , Brandemuehl Michael J.
Published: October 2008

A standardized deployment of solar electric systems in the Colorado production home market is crucial to the success of the renewable portfolio standard recently adopted by Colorado voters. This research uses the Built Green® program as a context for investigating energy conservation measures (ECMs), viable within the production home market, for their efficacy in curtailing new home annual energy consumption and peak electrical demand loads. The research examines the cost effectiveness and impact of residential solar systems compared to the energy conservation measures. Colorado is a state with good solar resources and considerable production-scale residential development. However, most production homes built in the state today are not highly energy efficient. It is generally believed that improvements to energy efficiency — more insulation, better windows, more efficient appliances — are more cost-effective than solar production systems given current costs. In other words, most production homes in Colorado are not ready to don a solar home system (SHS). The analysis uses extensive energy simulation to determine energy savings of selected energy-saving home features relative to the baseline Building America Benchmark for Denver, CO. This optimization process seeks to identify the least-cost combinations of improvements, assuming present day component costs, with the greatest annual energy savings, with the ultimate goal of implementing solar energy in the Colorado production home market. The results of the analysis suggest that optimal characteristics of production home, designed to minimize total costs, are readily achievable in today’s market. Moreover, when these optimal ECMs are implemented, the marginal cost of a SHS is found to be less than additional energy efficiency. With further energy efficiency improvements, site-based solar electric systems can compete economically given current state and federal incentive programs. The results also indicate that a solar system oriented west of due south can offer significant reductions in peak demand relative to both the household and utility load profiles.
Field Survey of Parabolic Trough Receiver Thermal Performance
Authors: Price Henry , Forristall Russell , Wendelin Timothy , Lewandowski Allan , Moss Timothy , Gummo Carin
Published: October 2008

This paper describes a technique that uses an infrared (IR) camera to evaluate the in-situ thermal performance of parabolic trough receivers at operating solar power plants. The paper includes results to show how the glass temperature measured with the IR camera correlates with modeled thermal losses from the receiver. Finally, the paper presents results of a field survey that used this technique to quickly sample a large number of receivers to develop a better understanding of how both original and replacement receivers are performing after up to 17 years of operational service.
Preparation of CIGSS Thin-Film Solar Cells by Rapid Thermal Processing
Authors: Kulkarni Sachin S. , Shirolikar Jyoti S. , Dhere Neelkanth G.
Published: October 2008

Rapid thermal processing (RTP) provides a way to rapidly heat substrates to an elevated temperature to perform relatively short duration processes, typically less than 2–3 minutes long. RTP can be utilized to minimize the process cycle time without compromising process uniformity, thus eliminating a bottleneck in CuIn1-xGaxSe2-ySy (CIGSS) module fabrication. Some approaches have been able to realize solar cells with conversion efficiencies close or equal to those for conventionally processed solar cells with similar device structures. Florida Solar Energy Center (FSEC) PV Materials Lab has developed excellent facilities for the preparation of CIGSS thin-film solar cells. A RTP reactor for preparation of CIGSS thin films on 10 cm × 10 cm substrates has been designed, assembled and tested at the FSEC PV Materials Lab. This paper describes the synthesis and characterization of CIGSS thin-film solar cells by RTP technique. Materials characterization of these films was done by SEM, XEDS, XRD, AES, EPMA and electrical characterization was done by current-voltage measurements on soda lime glass substrates by RTP technique. Encouraging results were obtained during the first few experimental sets, demonstrating that reasonable solar cell efficiencies (up to 9%) can be achieved with relatively shorter cycle times, lower thermal budgets and without using toxic gases.
Comparative Thermal Analysis of Structural Insulated Panels and Wood Frame Walls for Residential Buildings
Authors: Krarti Moncef , Hildreth Tom
Published: October 2008

This paper overviews the thermal performance of various wall construction assemblies including structural insulated panels (SIP) and wood frame walls based on laboratory testing and in-situ testing. Moreover, results from a series of simulation analysis are summarized to assess the thermal performance of residential buildings constructed with SIPs for various locations in the US. The simulation results are utilized to developed a simplified analysis tool to estimate the energy use savings associated of utilizing any wall construction assembly SIPs instead of wood frame walls are discussed for selected US locations.
C/SiC Composites by Electrophoretical Infiltration
Authors: Dittrich Rosemarie , Mu¨ller Eberhard , Popp Uta
Published: October 2008

Due to its high thermodynamical stability carbon fiber reinforced silicon carbide is an interesting material for high temperature applications. Studies are described to find an innovative route for fabricating C/SiC composites by using electrophoresis for infiltrating carbon fiber mats with non-aqueous suspensions of mixtures of silicon carbide powders, stabilizers and sintering aids. The suitability of nano-scaled and submicron powders is discussed. Based on investigations of the interaction between the SiC particle surfaces and the carbon fibers essential technological parameters of the electrophoretic infiltration are defined. The fabrication of C/SiC composites by lamination of single infiltrated fiber mats and a subsequent thermal process is demonstrated.
Mechanical Properties of Plastics Reinforced With Carbon Nanotubes
Authors: Podgaets Aleksandr R. , Ockels Wubbo J. , Sokolkin Yuriy V.
Published: October 2008

This paper describes the first steps in the area of prediction mechanical properties of nanotubes-plastic composites. Multi-level approach is used in order to take into account all the known data about all levels of composite material. Effective (macroscopic) mechanical properties are produced from solution of inverse boundary problem of continuum medium mechanics with coordinate-dependent elastic tensor. Theoretical results are compared with known experiment [1] on reinforcing polystyrene film.
Multifunctional Characteristics of Carbon Nanotube (CNT) Yarn Composites
Authors: Hernandez Corey D. , Zhang Mei , Fang Shaoli , Baughman Ray H. , Gates Thomas S. , Kahng Seun K.
Published: October 2008

By forming composite structures with Carbon Nanotube (CNT) yarns we achieve materials capable of measuring strain and composite structures with increased mechanical strength. The CNT yarns used are of the 2-ply and 4-ply variety with the yarns having diameters of about 15–30 μm. The strain sensing characteristics of the yarns are investigated on test beams with the yarns arranged in a bridge configuration. Additionally, the strain sensing properties are also investigated on yarns embedded on the surface of a flexible membrane. Initial mechanical strength tests also show an increase in the modulus of elasticity of the composite materials while incurring a weight penalty of less than one-percent. Also presented are initial temperature characterizations of the yarns.
Microstructural and Mechanical Characterization of Carbon Nanofiber Reinforced Composites
Authors: Rohatgi Aashish , Pogue William R. , Baucom Jared N. , Thomas James P.
Published: October 2008

Carbon nanofibers, such as single walled carbon nanotubes (SWNT), multiwalled carbon nanotubes (MWNT) and vapor-grown carbon nanofibers (VGCF or VGCNF) are routinely compounded with polymers to create thermally and electrically conductive polymer nanocomposites. Our group is interested in combining the conduction with structural functionality by reinforcing a high-performance thermotropic liquid crystal polymer (LCP) matrix with vapor-grown carbon nanofibers and single walled carbon nanotubes. High strength and stiffness can be achieved in LCPs through the alignment of molecular domains during high-shear mixing and extrusion. Further strength and stiffness enhancements are potentially possible if the carbon nanofibers could also be aligned, perhaps, with the assistance of the aligned domains of the LCP matrix. However, the geometrical structure of VGCF is quite different and the diameter is one to two orders of magnitude larger than that of SWNT. Therefore, the processing conditions and the interactions between the LCP domains and the nanofibers are expected to lead to different dispersion and alignment characteristics of VGCF and SWNT within the LCP matrix. In this work, twin-screw and Maxwell-type mixer-extruders were used to produce neat LCP filaments and LCP-nanofiber composite filaments with various concentrations of VGCF and SWNT. The dispersion and orientation of the VGCF and SWNT reinforcements were determined by X-ray diffraction and electron microscopy. The filaments were loaded in quasi-static uniaxial tension until fracture to determine the tensile modulus, strength and strain-to-failure. The mechanical properties showed a strong dependence on the filament diameter, nanofiber concentration and processing parameters. A significant increase in mechanical performance was observed with decreasing filament diameter irrespective of the carbon nanofiber concentration. Fracture surfaces examined under electron microscopy revealed hierarchical features at multiple length scales. At the macroscopic scale, a skin-core configuration was observed in the filament cross-section with the skin possessing a greater degree of LCP molecular alignment and nanofiber alignment than the core. The mechanical and electrical properties of the LCP, LCP-VGCF and LCP-SWNT nanocomposite filaments will be described and related to processing parameters, the type of carbon nanofibers (VGCF or SWNT) and the resulting composite microstructure.
EMI Shielding Effectiveness of Carbon Nanotube BuckyPaper Nanocomposite/Foam Sandwich Structures
Authors: Wang Ben , Liang Richard , Marietta-Tondin Olivier , Wang Sheng , Zhang Chuck , Kramer Les , Funchess Percy
Published: October 2008

Carbon nanotubes are known for their exceptional mechanical, electrical and thermal properties. Nanotubes’ electrical properties will play a vital role in many critical applications, with EMI shielding as one of the more important applications. In this study, the authors examined the effectiveness of SWNT BuckyPaper films’ electromagnetic interference (EMI) shielding. Individual BuckyPaper films used in the research were only 15∼25μm thick with an area density of 0.0705 oz./ft2 or 21.5g/m2. Highly conductive SWNT BuckyPapers films were incorporated into foam sandwich structures. EMI tests revealed that the foam structures with a surface skin of two layers of randomly oriented BuckyPaper films achieved attenuation as great as 26 dB at 455–500 MHz or an average of 21 dB across the entire frequency range, compared to the pure foam control panel. At frequency ranges of 4GHz-18GHz, the foam sandwich samples with three layers SWNT BuckyPapers showed an EMI attenuation as high as 30dB across the entire frequency range. The results show that SWNT BuckyPaper materials offer a very promising lightweight technical solution for EMI shielding application. BuckyPapers can also easily be incorporated into conventional composite structures, which is critical for potential large scale application of SWNTs for multifunctional composites and structures.
Characterization of the Consolidation Behavior of Fabricated Nanocrystalline-Nanopowders of TiC/Al-2124 Composite
Authors: Salem Hanadi G. , El Eskandarany Sherif , Fattah Hassan Abdul
Published: October 2008

Nanoscale materials have been the subject of major interest in recent years due to the anticipated ultrahigh strength and toughness combination anticipated in contrast to materials with conventional meso and micro-scale structures. The key issue lays in the optimization of the processing parameters suitable for the production of bulk nanostructured materials (BNSM) with superior properties suitable for elevated and cryogenic temperature applications. In the current research, a top down approach was employed for the refinement of a micron scale Al-2124 alloy powder about 45μm in average size using high energy ball milling up to 24 hours. Reinforcement of the refined Al-2124 nanocrystalline powders with 1μm nanostructured powder of TiC with internal structure <100 nm was performed to investigate the compaction and consolidation behavior of the produced nanocomposites. X-ray diffraction was employed to determine the crystallite size as a function of milling time (MT). microhardness of the milled powders was characterized for the hot compacts. Microstructural evolution of the green compacts was investigated by a 1nm resolution field emission scanning electron microscope (SEM), while the hot compacts were investigated using optical microscopy. Nanocrystalline-nanopowders <300nm in particle size and 20nm internal structural size were fabricated successfully at 24hr of MT from a 45μm particle sized 2124-Al powder with internal structure of 78nm in average size. The green compact densities of the nanoscale powder decreased to 92% compared to 97% for the microscale as-received powder due to the resistance of the strain hardened agglomerates to the applied pressure used for compaction. The microscale as-received powder was severely deformed during compaction, which resulted in higher densities. The degree by which the density decreased with the addition of 5-wt% TiC to the matrix was much lower for the nanoscale powder compared to the microscale one due to the low RPS ratio between the matrix and the reinforcement which promoted uniform distribution of the TiC particles within the matrix agglomerates. Increasing TiC content up to 10 wt% resulted in the formation of large voids and cavities. Refinement of the microscale powder to the nanoscale size resulted in 22.5% increase in hardness in the un-reinforced condition. Moreover, significant increase in hardness was also achieved with increasing TiC-content up to 10%.