Matching Items (100)

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ZINC TIN OXIDE AND SELF ASSEMBLED MONOLAYERS IN BULK HETEROJUNCTION ORGANIC PHOTOVOLTAICS

Description

Solar cells are an increasingly important energy source for meeting growing energy demands. Organic photovoltaics in particular have potential in this area due to their low cost and the relative

Solar cells are an increasingly important energy source for meeting growing energy demands. Organic photovoltaics in particular have potential in this area due to their low cost and the relative abundance of their constituents. One concern with the inverted configuration (a type of OPV with increased long-term stability) is their reliance on activation by ultraviolet (UV) light. Here we examine the incorporation of a new electron transport layer (ETL) material, zinc tin oxide (ZTO), in order to assess its interaction with UV light. Current-voltage characteristics were analyzed using a 420 nm cutoff filter to control UV light exposure. ZTO proved to be an adequate alternative to ZnO when comparing photovoltaic response. However, no improvement was found in terms of UV light activation. In addition, recent works show that oxygen plasma treatment of metal oxides used for hole transport layers modifies the work function and yields higher efficiency devices. Spin cast benzyl phosphonic acid self-assembled monolayers (BPA SAMs) provide similar results without the need for plasma treatment. Here we examine the use of BPA SAMs in standard devices utilizing PV2000, a proprietary active layer blend made by Plextronics. The use of BPA SAMs on a nickel oxide hole transport layer deepened the work function significantly, yielding greater device performance.

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Date Created
  • 2014-05

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Theoretical Model of Solar Photovoltaic Air Conditioning with Ice Thermal Storage

Description

An investigation is undertaken of a prototype building-integrated solar photovoltaic-powered thermal storage system and air conditioning unit. The study verifies previous thermodynamic and economic conclusions and provides a more thorough

An investigation is undertaken of a prototype building-integrated solar photovoltaic-powered thermal storage system and air conditioning unit. The study verifies previous thermodynamic and economic conclusions and provides a more thorough analysis. A parameterized model was created for optimization of the system under various conditions. The model was used to evaluate energy and cost savings to determine viability of the system in several circumstances, such as a residence in Phoenix with typical cooling demand. The proposed design involves a modified chest freezer as a thermal storage tank with coils acting as the evaporator for the refrigeration cycle. Surrounding the coils, the tank contains small containers of water for high-density energy storage submerged in a low freezing-point solution of propylene glycol. The cooling power of excess photovoltaic and off-peak grid power that is generated by the air conditioning compressor is stored in the thermal storage tank by freezing the pure water. It is extracted by pumping the glycol across the ice containers and into an air handler to cool the building. Featured results of the modeling include the determination of an optimized system for a super-peak rate plan, grid-connected Phoenix house that has a 4-ton cooling load and requires a corresponding new air conditioner at 4.5 kW of power draw. Optimized for the highest payback over a ten year period, the system should consist of a thermal storage tank containing 454 liters (120 gallons) of water, a 3-ton rated air conditioning unit, requiring 2.7 kW, which is smaller than conventionally needed, and no solar photovoltaic array. The monthly summer savings would be $45.The upfront cost would be $5489, compared to a conventional system upfront cost of $5400, for a payback period of 0.33 years. Over ten years, this system will provide $2600 of savings. To optimize the system for the highest savings over a twenty year period, a thermal storage tank containing 272 liters (72 gallons) of water, a 40-m2 photovoltaic array with 15% efficiency, and a 3.5-ton, 3.1-kW rated air conditioning unit should be installed for an upfront cost of $19,900. This would provide monthly summer savings of $225 and 1062 kWh grid electricity, with a payback period of only 11 years and a total cost savings of $12,300 over twenty years. In comparison, a system with the same size photovoltaic array but without storage would result in a payback period of 16 years. Results are also determined for other cooling requirements and installation sizes, such that the viability of this type of system in different conditions can be discussed. The use of this model for determining the optimized system configuration given different constraints is also described.

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Date Created
  • 2013-05

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Electrode Surface Area Roughness Effect on Power Output of Thermogalvanic Cells

Description

This paper presents an experimental investigation into the effects of altering electrode surface area roughness on thermogalvanic cell performance. A temperature difference between two electrodes was induced and brought to

This paper presents an experimental investigation into the effects of altering electrode surface area roughness on thermogalvanic cell performance. A temperature difference between two electrodes was induced and brought to steady state to achieve a difference of around 50 °C, which was maintained with a DC power generated hot wire and a pumped ice bath. The open-circuit voltage values at steady-state were measured by a programed multimeter and the temperatures were measured by a series of type K thermocouples. Electrode surface area roughness was altered using different grit values of sandpaper and measuring the values using a Zescope Optical Profilometer. Once three different surface area average values were achieved, 6 trials were performed with 2 trials per roughness value. The results were tabulated in Section 4 of this report.
It was predicted that increasing the surface area roughness would increase the number of electrons present in the reduction oxidation reaction and decrease the activation resistance of the thermogalvanic system. Decreasing the activation resistance, a component of total internal resistance, would therefore increase the power output of the cell by a small magnitude. The results showed that changing the surface area roughness of the Copper electrodes evidently had no effect on the outputs of the cell system. Additionally, the Seebeck coefficient was also unaffected by the presence of increased surface area roughness.
The work presented in the following paper is part of a continuing effort to better understand the performance of thermogalvanic cells and their heat to electrical energy transfer properties.

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Date Created
  • 2017-05

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Mechanical and Thermal Properties of Copper Slag Concrete

Description

In this investigation, copper slag was used as a coarse aggregate in four different mixes of concrete, consisting of 0%, 25%, 50%, and 100% copper slag by volume. Locally available

In this investigation, copper slag was used as a coarse aggregate in four different mixes of concrete, consisting of 0%, 25%, 50%, and 100% copper slag by volume. Locally available Salt river aggregate was used as a control, and mixes were tested for density, strength, thermal conductivity, specific heat capacity, and thermal diffusivity. Density was shown to increase with increasing copper slag content, increasing an average of 2298 kg/m^3, 2522 kg/m^3, and 2652 kg/m^3 in the 25%, 50%, and 100% mixes. This represents a 15% increase in density from 0% to 100%. Compressive strength testing indicated that the presence of copper slag in concrete provides no definitive strength benefit over Salt River aggregate. This result was expected, as concrete's strength is primarily derived from the cement matrix and not the aggregate. Thermal conductivity showed a decreasing trend with increasing copper slag content. Th control mix had an average conductivity of 0.660 W/m*K, and the 25%, 50%, and 100% mixes had conductivities of 0.649 W/m*K, 0.647 W/m*K, and 0.519 W/m*K, respectively. This represents 21% drop in thermal conductivity over the control. This result was also expected, as materials formed at higher temperatures, like copper slag, tend to have lower thermal conductivities. Specific heat capacity testing yielded results that were statistically indeterminate, though unlike strength testing this arose from inaccurate assumptions made during testing. This also prevented accurate thermal diffusivity results, as diffusivity is a function of density, thermal conductivity, and specific heat capacity. However, given the trends of the first two parameters, it is plausible to say that diffusivity in copper slag concrete would be lower than that of the control ix. All of these results were plugged into ASU's Pavement Temperature Model to see what effect they had in mitigating the UHI effect.

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Date Created
  • 2012-05

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Heat Transport System Design

Description

Part of the AORA and LightWorks collaboration in utilizing exhaust heat for the AORA Tulip is the purpose to design a heat transport system that meets system requirements. The

Part of the AORA and LightWorks collaboration in utilizing exhaust heat for the AORA Tulip is the purpose to design a heat transport system that meets system requirements. The investigation included research in potential fluids, equipment, costs, and conducting an analysis to determine favorably fluids. The operating range of the system is 100℃ to 200℃ from the 270℃ exhaust heat 30 meters high. The best, affordable heat transfer fluids (HTF) for this operating temperature range are: XCELTHERM CA, XCELTHERM 600, XCELTHERM 315, Therminol 55, Paratherm NF, Water, Dynalene PG-XT, and Dynalene HC-20. These fluids consist of synthetic oils, mineral oils, propylene glycol, potassium formate/water-based, and water. The ideal operating temperature and HTF depends on the location, accessibility to these fluids, and load application for the heat transport system design. Furthermore, the cost of electricity in the area is a factor for whether the system should use a variable speed drive on the pump. Water is the ideal heat transfer fluid if the operating temperature doesn’t exceed 170℃ and can be readily maintained to avoid corrosion. It has the lowest initial cost and most favorable heat transfer characteristics. The potassium formate/water-based Dynalene HC is the next best choice if the operating temperature doesn’t exceed 210℃. It has similar heat transfer characteristics, but costs more. Lastly, if the operating temperature range exceeds 210℃, then XCELTHERM 600 (white oil) is likely the best HTF to use. It has an operating range up to 315℃, has favorable characteristics, the most affordable oil price, is food contact rated, and has one of the longest life of any fluid of its type.

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Date Created
  • 2016-05

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Balance of System Cost Analysis to Investigate Future Economic Competitiveness of Tandem Solar Cells

Description

As single junction silicon based solar cells approach their Shockley\u2014Queasier (SQ) conversion efficiency limits, tandem solar cells (TSC) provide an attractive prospect for higher efficiency cells. Although TSCs have been

As single junction silicon based solar cells approach their Shockley\u2014Queasier (SQ) conversion efficiency limits, tandem solar cells (TSC) provide an attractive prospect for higher efficiency cells. Although TSCs have been shown to be more efficient, their higher fabrication costs are a limiting factor for their economic competitiveness and large-scale integration in PV power systems. Current literature suggests that even with reduced costs of fabrication in the future, TSCs still offer no competitive benefit for integration in utility-scale systems and may yield minimal benefits only in places where area-related costs are high. This work investigates Balance of Systems (BoS) circumstances under which TSCs can attain economic viability in scenarios where the necessary technological advances are made to increase the efficiency of solar cells beyond the SQ limit.

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Date Created
  • 2017-05

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E-bike Retrofitting Kit

Description

The goal of this honors thesis creative project was to design, manufacture and test a retrofitted E-bike kit that met certain stated design objections. To design a successful E-bike kit,

The goal of this honors thesis creative project was to design, manufacture and test a retrofitted E-bike kit that met certain stated design objections. To design a successful E-bike kit, the needs of the customer were researched and turned into measurable engineering requirements. For the biker, these requirements are speed, range, cost and simplicity. The approach is outlined similarly to the capstone program here at ASU. There is an introduction in sections 1 and 2 which gives the motivation and an overview of the project done. In section 3, the voice of the customer is discussed and converted into requirements. In sections 4, 5,6,7 and 8 the design process is described. Section 4 is the conceptual design where multiple concepts are narrowed down to one design. Section 5 is the preliminary design, where the design parts are specified and optimized to fit requirements. Section 6 is fabrication and assembly which gives details into how the product was manufactured and built. Sections 7 and 8 are the testing and validation sections where tests were carried out to verify that the requirements were met. Sections 9 and 10 were part of the conclusion in which recommendations and the project conclusions are depicted. In general, I produced a successful prototype. Each phase of the design came with its own issues and solutions but in the end a functioning bike was delivered. There were a few design options considered before selecting the final design. The rear-drive friction design was selected based on its price, simplicity and performance. The design was optimized in the preliminary design phase and items were purchased. The purchased items were either placed on the bike directly or had to be manufactured in some way. Once the assembly was completed, testing and validation took place to verify that the design met the requirements. Unfortunately, the prototype did not meet all the requirements. The E-bike had a maximum speed of 14.86 mph and a range of 12.75 miles which were below the performance requirements of 15 mph and 15 miles. The cost was $41.67 over the goal of $300 although the total costs remained under budget. At the end of the project, I delivered a functioning E-bike retrofitting kit on the day of the defense. While it did not meet the requirements fully, there was much room for improvement and optimization within the design.

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Date Created
  • 2017-05

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Thermal Energy Storage Using Organic and Metallic Phase Change Materials

Description

Concentrated Solar Power and Thermal Energy Storage are two technologies that are currently being explored as environmentally friendly methods of energy generation. The two technologies are often combined in an

Concentrated Solar Power and Thermal Energy Storage are two technologies that are currently being explored as environmentally friendly methods of energy generation. The two technologies are often combined in an overall system to increase efficiency and reliability of the energy generation system. A collaborative group of researchers from Australia and the United States formed a project to design solar concentrators that utilize Concentrated Solar Power and Thermal Energy Storage. The collaborators from Arizona State designed a Latent Heat Thermal Energy Storage system for the project. It was initially proposed that the system utilize Dowtherm A as the Heat Transfer Fluid and a tin alloy as the storage material. Two thermal reservoirs were designed as part of the system; one reservoir was designed to be maintained at 240˚ C, while the other reservoir was designed to be maintained at 210˚ C. The tin was designed to receive heat from the hot reservoir during a charging cycle and discharge heat to the cold reservoir during a discharge cycle. From simulation, it was estimated that the system would complete a charging cycle in 17.5 minutes and a discharging cycle in 6.667 minutes [1]. After the initial design was fabricated and assembled, the system proved ineffective and did not perform as expected. Leaks occurred within the system under high pressure and the reservoirs could not be heated to the desired temperatures. After adding a flange to one of the reservoirs, it was decided that the system would be run with one reservoir, with water as the Heat Transfer Fluid. The storage material was changed to paraffin wax, because it would achieve phase change at a temperature lower than the boiling point of water. Since only one reservoir was available, charging cycle tests were performed on the system to gain insight on system performance. It was found that the paraffin sample only absorbs 3.29% of the available heat present during a charging cycle. This report discusses the tests performed on the system, the analysis of the data from these tests, the issues with the system that were revealed from the analyses, and potential design changes that would increase the efficiency of the system.

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Date Created
  • 2016-12

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A Bench-Top Demonstration of a Novel Material Thermal Storage System Test Apparatus

Description

As part of a United States-Australian Solar Energy Collaboration on a Micro Urban Solar Integrated Concentrator project, the purpose of the research was to design and build a bench-top apparatus

As part of a United States-Australian Solar Energy Collaboration on a Micro Urban Solar Integrated Concentrator project, the purpose of the research was to design and build a bench-top apparatus of a solar power concentrator thermal storage unit. This prototype would serve to be a test apparatus for testing multiple thermal storage mediums and heat transfer fluids for verification and optimization of the larger system. The initial temperature range for the system to test a wide variety of thermal storage mediums was 100°C to 400°C. As for the thermal storage volume it was decided that the team would need to test volumes of about 100 mL. These design parameters later changed to a smaller range for the initial prototype apparatus. This temperature range was decided to be 210°C to 240°C using tin as a phase change material (PCM). It was also decided a low temperature (<100°C) test using paraffin as the PCM would be beneficial for troubleshooting purposes.

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Date Created
  • 2015-05

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Highly Efficient Selective Metamaterial Absorber for High-Temperature Solar Thermal Energy Harvesting

Description

In this work, a selective solar absorber made of nanostructured titanium gratings deposited on an ultrathin MgF2 spacer and a tungsten ground film is proposed and experimentally demonstrated. Normal absorptance

In this work, a selective solar absorber made of nanostructured titanium gratings deposited on an ultrathin MgF2 spacer and a tungsten ground film is proposed and experimentally demonstrated. Normal absorptance of the fabricated solar absorber is characterized to be higher than 0.9 in the UV, visible and, near infrared (IR) regime, while the mid-IR emittance is around 0.2. The high broadband absorption in the solar spectrum is realized by the excitation of surface plasmon and magnetic polariton resonances, while the low mid-IR emittance is due to the highly reflective nature of the metallic components. Further directional and polarized reflectance measurements show wide-angle and polarization-insensitive high absorption within solar spectrum. Temperature-dependent spectroscopic characterization indicates that the optical properties barely change at elevated temperatures up to 350 °C. The solar-to-heat conversion efficiency with the fabricated metamaterial solar absorber is predicted to be 78% at 100 °C without optical concentration or 80% at 400 °C with 25 suns. The performance could be further improved with better fabrication processes and geometric optimization during metamaterial design. The strong spectral selectivity, favorable diffuse-like behavior, and good thermal stability make the metamaterial selective absorber promising for significantly enhancing solar thermal energy harvesting in various systems at mid to high temperatures.

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Date Created
  • 2015-06-01