Matching Items (15)

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Degradation of gas-phase ethanol using TiO2 photocatalyst

Description

TiO2 has been studied in the degradation of ethanol for indoor application. A dynamic flowing non-loop system was utilized. The reactor was a quartz tube filled with the TiO2 catalyst

TiO2 has been studied in the degradation of ethanol for indoor application. A dynamic flowing non-loop system was utilized. The reactor was a quartz tube filled with the TiO2 catalyst with glass wool on the ends. The analytical equipment used were Vernier's ethanol and CO2 sensors with a two-point calibration performed on the ethanol sensor. The purpose of the calibration was to create a known standard to establish accurate readings. The experimental procedure followed the scheme of bypassing the reactor, flowing into the reactor without the UV lights on for a small period, turning the UV lights on for five minutes, and then going back to the bypass. A CFD simulation using ANSYS Fluent was done to determine the optimal inlet and outlet positions of the biochamber that housed the sensors. The objective of the simulation was to determine which inlet and outlet locations provided the best fluid flow for sensor contact and mixing. Sensitivity analysis of varying parameters were tested to determine the optimal settings in producing accurate results to fulfill the simulation goals. It was determined that a vertical position biochamber with an inlet centered on the top face and the outlet on the bottom of a side face was ideal. The main experimental results showed that ethanol of both low and high concentrations were completely or almost fully degraded into carbon-products. The results showed that there was CO2 consumption and it was most likely due to a combination of sensor inaccuracy and accumulation onto the catalyst surface. However, the sensor inaccuracy would not account for the entirely of the CO2 consumption and previous studies have shown that carbon-products do form on the catalyst surface. Therefore, it can be asserted that CO2 has accumulated on the catalyst and the inclusion of water may have caused catalyst deactivation. Having the light on the photoreactor the whole time rather than waiting to turn on the light has shown to decrease the period of degradation but has no effect on the amount of degradation. Research from Nimlos, Muggli, etc., have determined that intermediate products such as acetaldehyde, acetic acid, formaldehyde, and formic acid form during ethanol degradation and this can be assumed to have occurred in this research as well. These intermediate products were not analyzed for this study, but has been included in the go-forward for future works. For indoor applications, TiO2 catalyst have already been implemented into consumer and commercialized air purifiers, but there is tremendous potential for HVAC systems. There are concerns with HVAC application as discussed, but if implemented correctly, it can be a useful tool for indoor air purification.

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  • 2017-05

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Investigation of Parameters that Affect Capsaicin Stability During Culinary Techniques

Description

Capsaicin and dihydrocapsaicin account for 90% of capsaicinoids when it comes to the pungency of peppers. Capsaicin stability was investigated through a cooking and storage parameter where three different tests

Capsaicin and dihydrocapsaicin account for 90% of capsaicinoids when it comes to the pungency of peppers. Capsaicin stability was investigated through a cooking and storage parameter where three different tests were done; cooking duration, cooking temperature, and storage stability. The concentration of capsaicinoids was quantified through gas chromatography-mass spectrometry where those values were then used to determine the total Scoville heat units (SHU). Furthermore, half-life was determined by finding the decay rate during cooking and storage. Results showed that there was an increase in degradation of capsaicinoids concentration when peppers were cooked for a long period of time. Degradation rate increases with increasing temperatures as would be expected by the Arrhenius equation. Hence, if a maximum pungency is wanted, it is best to cook the least time as possible or add the peppers towards the end of the culinary technique. This would help by cooking the peppers for a short period of time while not being exposed to the high temperature long enough before significant degradation occurs. Lastly, the storage stability results interpreted that a maximum potency of the peppers can be retained in a freezer or refrigerator opposed to an open room temperature environment or exposure from the sun. Furthermore, the stability of peppers has a long shelf life with even that the worse storage condition's half-life value was 113.5 months (9.5 years). Thus, peppers do not need to be bought frequently because its potency will last for several years.

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  • 2017-12

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Design of hygrothermal aging experiment for epoxy and composite samples

Description

Epoxy resins and composite materials are well characterized in their mechanical properties. However these properties change as the materials age under different conditions, as their microstructure undergoes changes from the

Epoxy resins and composite materials are well characterized in their mechanical properties. However these properties change as the materials age under different conditions, as their microstructure undergoes changes from the absorption or desorption of water. Many of these microstructural changes occur at the interfacial region between where the matrix of the composite meets the reinforcement fiber, but still result in significant effects in the material properties. These effects have been studied and characterized under a variety of conditions by artificially aging samples. The artificial aging process focuses on exposing samples to environmental conditions such as high temperature, UV light, and humidity. While conditions like this are important to study, in real world applications the materials will not be simply resting in a laboratory created environment. In most circumstances, they are subjected to some kind of stress or impact. This report will focus on designing an experiment to analyze aged samples under tensile loading and creating a fixture that will sustain loading while the samples are aged. . The conditions that will be tested are control conditions at standard temperature and humidity in the laboratory, submerged, thermal heating, submerged and heated, and hygrothermal.

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Date Created
  • 2018-05

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26+ year old photovoltaic power plant: degradation and reliability evaluation of crystalline silicon modules - north array

Description

The object of this study was a 26 year old residential Photovoltaic (PV) monocrystalline silicon (c-Si) power plant, called Solar One, built by developer John F. Long in Phoenix, Arizona

The object of this study was a 26 year old residential Photovoltaic (PV) monocrystalline silicon (c-Si) power plant, called Solar One, built by developer John F. Long in Phoenix, Arizona (a hot-dry field condition). The task for Arizona State University Photovoltaic Reliability Laboratory (ASU-PRL) graduate students was to evaluate the power plant through visual inspection, electrical performance, and infrared thermography. The purpose of this evaluation was to measure and understand the extent of degradation to the system along with the identification of the failure modes in this hot-dry climatic condition. This 4000 module bipolar system was originally installed with a 200 kW DC output of PV array (17 degree fixed tilt) and an AC output of 175 kVA. The system was shown to degrade approximately at a rate of 2.3% per year with no apparent potential induced degradation (PID) effect. The power plant is made of two arrays, the north array and the south array. Due to a limited time frame to execute this large project, this work was performed by two masters students (Jonathan Belmont and Kolapo Olakonu) and the test results are presented in two masters theses. This thesis presents the results obtained on the north array and the other thesis presents the results obtained on the south array. The resulting study showed that PV module design, array configuration, vandalism, installation methods and Arizona environmental conditions have had an effect on this system's longevity and reliability. Ultimately, encapsulation browning, higher series resistance (potentially due to solder bond fatigue) and non-cell interconnect ribbon breakages outside the modules were determined to be the primary causes for the power loss.

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Date Created
  • 2013

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Characterization and analysis of long term field aged photovoltaic modules and encapsulant materials

Description

Photovoltaic (PV) module degradation is a well-known issue, however understanding the mechanistic pathways in which modules degrade is still a major task for the PV industry. In order to study

Photovoltaic (PV) module degradation is a well-known issue, however understanding the mechanistic pathways in which modules degrade is still a major task for the PV industry. In order to study the mechanisms responsible for PV module degradation, the effects of these degradation mechanisms must be quantitatively measured to determine the severity of each degradation mode. In this thesis multiple modules from three climate zones (Arizona, California and Colorado) were investigated for a single module glass/polymer construction (Siemens M55) to determine the degree to which they had degraded, and the main factors that contributed to that degradation. To explain the loss in power, various nondestructive and destructive techniques were used to indicate possible causes of loss in performance. This is a two-part thesis. Part 1 presents non-destructive test results and analysis and Part 2 presents destructive test results and analysis.

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Date Created
  • 2015

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Assessment and solutions for waste handling of compostable biopolymers

Description

Fossil resources have enabled the development of the plastic industry in the last century. More recently biopolymers have been making gains in the global plastics market. Biopolymers are plastics derived

Fossil resources have enabled the development of the plastic industry in the last century. More recently biopolymers have been making gains in the global plastics market. Biopolymers are plastics derived from plants, primarily corn, which can function very similarly to fossil based plastics. One difference between some of the dominant biopolymers, namely polylactic acid and thermoplastic starch, and the most common fossil-based plastics is the feature of compostability. This means that biopolymers represent not only a shift from petroleum and natural gas to agricultural resources but also that these plastics have potentially different impacts resulting from alternative disposal routes. The current end of life material flows are not well understood since waste streams vary widely based on regional availability of end of life treatments and the role that decision making has on waste identification and disposal.

This dissertation is focused on highlighting the importance of end of life on the life-cycle of biopolymers, identifying how compostable biopolymer products are entering waste streams, improving collection and waste processing, and quantifying the impacts that result from the disposal of biopolymers. Biopolymers, while somewhat available to residential consumers, are primarily being used by various food service organizations trying to achieve a variety of goals such as zero waste, green advertising, and providing more consumer options. While compostable biopolymers may be able to help reduce wastes to landfill they do result in environmental tradeoffs associated with agriculture during the production phase. Biopolymers may improve the management for compostable waste streams by enabling streamlined services and reducing non-compostable fossil-based plastic contamination. The concerns about incomplete degradation of biopolymers in composting facilities may be ameliorated using alkaline amendments sourced from waste streams of other industries. While recycling still yields major benefits for traditional resins, bio-based equivalents may provide addition benefits and compostable biopolymers offer benefits with regards to global warming and fossil fuel depletion. The research presented here represents two published studies, two studies which have been accepted for publication, and a life-cycle assessment that will be submitted for publication.

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Date Created
  • 2015

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Climate-specific degradation rate and linearity analysis of photovoltaic power plants using performance ratio, performance index, and raw kWh methods

Description

In the past 10 to 15 years, there has been a tremendous increase in the amount of photovoltaic (PV) modules being both manufactured and installed in the field. Power plants

In the past 10 to 15 years, there has been a tremendous increase in the amount of photovoltaic (PV) modules being both manufactured and installed in the field. Power plants in the hundreds of megawatts are continuously being turned online as the world turns toward greener and sustainable energy. Due to this fact and to calculate LCOE (levelized cost of energy), it is understandably becoming more important to comprehend the behavior of these systems as a whole by calculating two key data: the rate at which modules are degrading in the field; the trend (linear or nonlinear) in which the degradation is occurring. As opposed to periodical in field intrusive current-voltage (I-V) measurements, non-intrusive measurements are preferable to obtain these two key data since owners do not want to lose money by turning their systems off, as well as safety and breach of installer warranty terms. In order to understand the degradation behavior of PV systems, there is a need for highly accurate performance modeling. In this thesis 39 commercial PV power plants from the hot-dry climate of Arizona are analyzed to develop an understanding on the rate and trend of degradation seen by crystalline silicon PV modules. A total of three degradation rates were calculated for each power plant based on three methods: Performance Ratio (PR), Performance Index (PI), and raw kilowatt-hour. These methods were validated from in field I-V measurements obtained by Arizona State University Photovoltaic Reliability Lab (ASU-PRL). With the use of highly accurate performance models, the generated degradation rates may be used by the system owners to claim a warranty from PV module manufactures or other responsible parties.

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Date Created
  • 2016

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Spatial temperature uniformity and statistical determination of dominant degradation modes in PV modules

Description

This is a two-part thesis.

Part 1 of this thesis investigates the influence of spatial temperature distribution on the accuracy of performance data of photovoltaic (PV) modules in outdoor conditions and

This is a two-part thesis.

Part 1 of this thesis investigates the influence of spatial temperature distribution on the accuracy of performance data of photovoltaic (PV) modules in outdoor conditions and provides physical approaches to improve the spatial temperature distribution of the test modules so an accurate performance data can be obtained in the field. Conventionally, during outdoor performance testing, a single thermocouple location is used on the backsheet or back glass of a test module. This study clearly indicates that there is a large spatial temperature difference between various thermocouple locations within a module. Two physical approaches or configurations were experimented to improve the spatial temperature uniformity: thermally insulating the inner and outer surface of the frame; backsheet and inner surface of the frame. All the data were compared with un-insulated conventional configuration. This study was performed in an array setup of six modules under two different preconditioning electrical configurations, Voc and MPPT over several clear sunny days. This investigation concludes that the best temperature uniformity and the most accurate I-V data can be obtained only by thermally insulating the inner and outer frame surfaces or by using the average of four thermocouple temperatures, as specified in IEC 61853-2, without any thermal insulation.

Part 2 of this thesis analyzes the field data obtained from old PV power plants using various statistical techniques to identify the most influential degradation modes on fielded PV modules in two different climates: hot-dry (Arizona); cold-dry (New York). Performance data and visual inspection data of 647 modules fielded in five different power plants were analyzed. Statistical tests including hypothesis testing were carried out to identify the I-V parameter(s) that are affected the most. The affected performance parameters (Isc, Voc, FF and Pmax) were then correlated with the defects to determine the most dominant defect affecting power degradation. Analysis indicates that the cell interconnect discoloration (or solder bond deterioration) is the dominant defect in hot-dry climate leading to series resistance increase and power loss, while encapsulant delamination is being the most dominant defect in cold-dry climate leading to cell mismatch and power loss.

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Date Created
  • 2015

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Defects and statistical degradation analysis of photovoltaic power plants

Description

As the photovoltaic (PV) power plants age in the field, the PV modules degrade and generate visible and invisible defects. A defect and statistical degradation rate analysis of photovoltaic (PV)

As the photovoltaic (PV) power plants age in the field, the PV modules degrade and generate visible and invisible defects. A defect and statistical degradation rate analysis of photovoltaic (PV) power plants is presented in two-part thesis. The first part of the thesis deals with the defect analysis and the second part of the thesis deals with the statistical degradation rate analysis. In the first part, a detailed analysis on the performance or financial risk related to each defect found in multiple PV power plants across various climatic regions of the USA is presented by assigning a risk priority number (RPN). The RPN for all the defects in each PV plant is determined based on two databases: degradation rate database; defect rate database. In this analysis it is determined that the RPN for each plant is dictated by the technology type (crystalline silicon or thin-film), climate and age. The PV modules aging between 3 and 19 years in four different climates of hot-dry, hot-humid, cold-dry and temperate are investigated in this study.

In the second part, a statistical degradation analysis is performed to determine if the degradation rates are linear or not in the power plants exposed in a hot-dry climate for the crystalline silicon technologies. This linearity degradation analysis is performed using the data obtained through two methods: current-voltage method; metered kWh method. For the current-voltage method, the annual power degradation data of hundreds of individual modules in six crystalline silicon power plants of different ages is used. For the metered kWh method, a residual plot analysis using Winters’ statistical method is performed for two crystalline silicon plants of different ages. The metered kWh data typically consists of the signal and noise components. Smoothers remove the noise component from the data by taking the average of the current and the previous observations. Once this is done, a residual plot analysis of the error component is performed to determine the noise was successfully separated from the data by proving the noise is random.

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Date Created
  • 2016

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Determination of dominant failure modes using combined experimental and statistical methods and selection of best method to calculate degradation rates

Description

This is a two part thesis:

Part 1 of this thesis determines the most dominant failure modes of field aged photovoltaic (PV) modules using experimental data and statistical analysis, FMECA (Failure

This is a two part thesis:

Part 1 of this thesis determines the most dominant failure modes of field aged photovoltaic (PV) modules using experimental data and statistical analysis, FMECA (Failure Mode, Effect, and Criticality Analysis). The failure and degradation modes of about 5900 crystalline-Si glass/polymer modules fielded for 6 to 16 years in three different photovoltaic (PV) power plants with different mounting systems under the hot-dry desert climate of Arizona are evaluated. A statistical reliability tool, FMECA that uses Risk Priority Number (RPN) is performed for each PV power plant to determine the dominant failure modes in the modules by means of ranking and prioritizing the modes. This study on PV power plants considers all the failure and degradation modes from both safety and performance perspectives, and thus, comes to the conclusion that solder bond fatigue/failure with/without gridline/metallization contact fatigue/failure is the most dominant failure mode for these module types in the hot-dry desert climate of Arizona.

Part 2 of this thesis determines the best method to compute degradation rates of PV modules. Three different PV systems were evaluated to compute degradation rates using four methods and they are: I-V measurement, metered kWh, performance ratio (PR) and performance index (PI). I-V method, being an ideal method for degradation rate computation, were compared to the results from other three methods. The median degradation rates computed from kWh method were within ±0.15% from I-V measured degradation rates (0.9-1.37 %/year of three models). Degradation rates from the PI method were within ±0.05% from the I-V measured rates for two systems but the calculated degradation rate was remarkably different (±1%) from the I-V method for the third system. The degradation rate from the PR method was within ±0.16% from the I-V measured rate for only one system but were remarkably different (±1%) from the I-V measured rate for the other two systems. Thus, it was concluded that metered raw kWh method is the best practical method, after I-V method and PI method (if ground mounted POA insolation and other weather data are available) for degradation computation as this method was found to be fairly accurate, easy, inexpensive, fast and convenient.

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Date Created
  • 2014