Analysis of maximum power point tracking data for obtaining photovoltaic parameters
- Authors: Chitura, Anesu Godfrey
- Date: 2020
- Subjects: Photovoltaic power system
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18576 , vital:42610
- Description: As a standard, photovoltaic (PV) modules are rated by the use of standard test conditions (STC). Such details entail current and voltage (I-V) measurements for modules under an irradiance of 1000 W/m2 an air mass ration of 1.5 global spectrum and 25˚C cell temperature. Outdoor weather conditions continuously vary with time and from one location to the other. This further offset the expected operational power outputs as outdoor conditions are generally characterized by high cell temperatures. The technology one uses will also complicate the power output prediction since different module technologies respond to these outdoor conditions differently. I-V tracers are able to measure the full I-V curve of the module thus can give the operational PV parameters at any given time. However, these tracers are sold at exorbitant prices and they require skilled personnel in order to operate them. Most if not all tracers require isolation of the module under test thereby disrupting the power production function of the module._________________________________________________________________________________________________________________________________________ In this study a method to obtain photovoltaic (PV) parameters using the maximum power point tracking (MPPT) data is presented and tested under natural outdoor conditions. The method features a customized data acquisition system (DAS) designed for the measurement and storage of meteorological and MPPT data. The DAS is capable of extracting parameters from any combination of modules with an open circuit voltage 〖(V〗_oc) less than or equal to 120 Volts and a short circuit current 〖(I〗_sc) of 100 Amps. The system used is capable of extracting MPPT data using a reliable, improved storage and a programmable data logger. In order to match the sampling operational speeds of internal charge controller switches a computer interfaced Peripheral Component Interconnect (PCI) card was also used. Data collection and characterization of the MPPT data was done in such a way that the power generation process remained uninterrupted throughout the whole process. The regression nonlinear least squares method was used to fit MPPT crests and obtain the knee part of the I-V curve. This was then extrapolated to obtain the full I-V curve, which then produces the operational PV parameters. The resultant parameters from the characterization process were logged and accessible at any time. The end result was a method that can be incorporated within a charge controller for quick, hands-free PV parameter extraction, using only the MPPT scanned data.
- Full Text:
- Authors: Chitura, Anesu Godfrey
- Date: 2020
- Subjects: Photovoltaic power system
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18576 , vital:42610
- Description: As a standard, photovoltaic (PV) modules are rated by the use of standard test conditions (STC). Such details entail current and voltage (I-V) measurements for modules under an irradiance of 1000 W/m2 an air mass ration of 1.5 global spectrum and 25˚C cell temperature. Outdoor weather conditions continuously vary with time and from one location to the other. This further offset the expected operational power outputs as outdoor conditions are generally characterized by high cell temperatures. The technology one uses will also complicate the power output prediction since different module technologies respond to these outdoor conditions differently. I-V tracers are able to measure the full I-V curve of the module thus can give the operational PV parameters at any given time. However, these tracers are sold at exorbitant prices and they require skilled personnel in order to operate them. Most if not all tracers require isolation of the module under test thereby disrupting the power production function of the module._________________________________________________________________________________________________________________________________________ In this study a method to obtain photovoltaic (PV) parameters using the maximum power point tracking (MPPT) data is presented and tested under natural outdoor conditions. The method features a customized data acquisition system (DAS) designed for the measurement and storage of meteorological and MPPT data. The DAS is capable of extracting parameters from any combination of modules with an open circuit voltage 〖(V〗_oc) less than or equal to 120 Volts and a short circuit current 〖(I〗_sc) of 100 Amps. The system used is capable of extracting MPPT data using a reliable, improved storage and a programmable data logger. In order to match the sampling operational speeds of internal charge controller switches a computer interfaced Peripheral Component Interconnect (PCI) card was also used. Data collection and characterization of the MPPT data was done in such a way that the power generation process remained uninterrupted throughout the whole process. The regression nonlinear least squares method was used to fit MPPT crests and obtain the knee part of the I-V curve. This was then extrapolated to obtain the full I-V curve, which then produces the operational PV parameters. The resultant parameters from the characterization process were logged and accessible at any time. The end result was a method that can be incorporated within a charge controller for quick, hands-free PV parameter extraction, using only the MPPT scanned data.
- Full Text:
Synthesis and characterization of binary and ternary palladium alloys for use as alternative counter electrode catalysts in dye sensitized solar cells
- Authors: Zingwe, Nyengerai Hillary
- Date: 2020
- Subjects: Electrocatalysis Chemistry
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: http://hdl.handle.net/10353/18513 , vital:42580
- Description: The dye sensitized solar cell counter electrode facilitates the regeneration of the dye molecules thereby ensuring the provision of higher sunlight to electricity conversion efficiency. The standard platinum electrode suffers from low efficiency due to corrosion by the redox mediator as well as being extremely expensive due to high demand. As an alternative this research study illustrates the efforts undertaken to replace the standard platinum counter electrode with palladium alloy counter electrodes. Application of palladium alloys ensures sustenance of high catalytic activity by palladium which is as effective as platinum. Although palladium is equally as expensive as platinum, its application in the form of alloys minimizes the amount required to produce an effective counter electrode to 0.001-0.004 moles thereby ensuring the provision of high efficiency at a lower cost. Furthermore, charge transfer from the other alloyed elements to the palladium atom increases active sites leading to higher catalytic activity than platinum. Additionally, changes in crystal structure due to alloying enhances resistance to corrosion thus enabling the longevity of the alloy counter electrode in the electrolyte ___________________________________________________________________________ Electrochemical analysis was conducted to determine the catalytic functionality of the developed alloys in cobalt, ferrocene and iodine redox mediators. The binary (PdNi-reduced graphene oxide (rGO) and PdCo-rGO) and ternary (PdNiCo-rGO) palladium alloys were fabricated via a hydrothermal method. In order to determine the composition which could provide the maximum activity, optimization was conducted through variation of the molar ratios of the precursor solutions. The properties of the synthesized palladium alloys were determined using various techniques including x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The developed alloys were observed to comprise of palladium, nickel, cobalt, and carbon atoms. The particles were spherical in nature for all the unsupported alloys with the carbon supported alloys exhibiting spherical particle wholly surrounded by graphene sheets. Cyclic voltammetry and electrochemical impedance spectroscopy analysis showed that the carbon supported alloys PdNi-rGO, PdCo-rGO and PdNiCo-rGO produced the highest catalytic activities due to the synergy between their respective alloys and the incorporated reduced graphene oxide. The high catalytic effectiveness of these alloys yielded power conversion efficiency in the order PdNiCo-rGO (9.01) > PdNi-rGO (8.4.%) > PdCo-rGO (6.56%) > Pt (5.7%) which were better than the platinum efficiency in the cobalt redox mediator. The higher efficiency in the cobalt redox mediator relative to the iodine electrolyte illustrates that they are viable alternatives to the, corrosive and volatile iodine. Obtained results show that, the high recombination rates between the photogenerated electrons and the oxidized dye molecule which have been reported to reduce power conversion efficiency in one electron redox mediators did not affect the performance of the cell. However, these higher recombination rates affected the ferrocene electrolyte leading to extremely poor efficiency metrics. The obtained results indicated that reduced graphene oxide supported PdNi-rGO, PdNiCo-rGO as well as the unsupported PdNi3 alloys could successfully be implemented as substitutes to the platinum counter electrode in dye sensitized solar cells. The application of the palladium alloys is vital for improving stability and power conversion efficiency, as well as reducing cost.
- Full Text:
- Authors: Zingwe, Nyengerai Hillary
- Date: 2020
- Subjects: Electrocatalysis Chemistry
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: http://hdl.handle.net/10353/18513 , vital:42580
- Description: The dye sensitized solar cell counter electrode facilitates the regeneration of the dye molecules thereby ensuring the provision of higher sunlight to electricity conversion efficiency. The standard platinum electrode suffers from low efficiency due to corrosion by the redox mediator as well as being extremely expensive due to high demand. As an alternative this research study illustrates the efforts undertaken to replace the standard platinum counter electrode with palladium alloy counter electrodes. Application of palladium alloys ensures sustenance of high catalytic activity by palladium which is as effective as platinum. Although palladium is equally as expensive as platinum, its application in the form of alloys minimizes the amount required to produce an effective counter electrode to 0.001-0.004 moles thereby ensuring the provision of high efficiency at a lower cost. Furthermore, charge transfer from the other alloyed elements to the palladium atom increases active sites leading to higher catalytic activity than platinum. Additionally, changes in crystal structure due to alloying enhances resistance to corrosion thus enabling the longevity of the alloy counter electrode in the electrolyte ___________________________________________________________________________ Electrochemical analysis was conducted to determine the catalytic functionality of the developed alloys in cobalt, ferrocene and iodine redox mediators. The binary (PdNi-reduced graphene oxide (rGO) and PdCo-rGO) and ternary (PdNiCo-rGO) palladium alloys were fabricated via a hydrothermal method. In order to determine the composition which could provide the maximum activity, optimization was conducted through variation of the molar ratios of the precursor solutions. The properties of the synthesized palladium alloys were determined using various techniques including x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The developed alloys were observed to comprise of palladium, nickel, cobalt, and carbon atoms. The particles were spherical in nature for all the unsupported alloys with the carbon supported alloys exhibiting spherical particle wholly surrounded by graphene sheets. Cyclic voltammetry and electrochemical impedance spectroscopy analysis showed that the carbon supported alloys PdNi-rGO, PdCo-rGO and PdNiCo-rGO produced the highest catalytic activities due to the synergy between their respective alloys and the incorporated reduced graphene oxide. The high catalytic effectiveness of these alloys yielded power conversion efficiency in the order PdNiCo-rGO (9.01) > PdNi-rGO (8.4.%) > PdCo-rGO (6.56%) > Pt (5.7%) which were better than the platinum efficiency in the cobalt redox mediator. The higher efficiency in the cobalt redox mediator relative to the iodine electrolyte illustrates that they are viable alternatives to the, corrosive and volatile iodine. Obtained results show that, the high recombination rates between the photogenerated electrons and the oxidized dye molecule which have been reported to reduce power conversion efficiency in one electron redox mediators did not affect the performance of the cell. However, these higher recombination rates affected the ferrocene electrolyte leading to extremely poor efficiency metrics. The obtained results indicated that reduced graphene oxide supported PdNi-rGO, PdNiCo-rGO as well as the unsupported PdNi3 alloys could successfully be implemented as substitutes to the platinum counter electrode in dye sensitized solar cells. The application of the palladium alloys is vital for improving stability and power conversion efficiency, as well as reducing cost.
- Full Text:
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