Browsing by Author "James Leach, Committee Member"

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An Experimental Evaluation of the Performance of the Amorphous Silicon PV Array on the NCSU AFV Garage
(2007-04-24) Christy, Daniel William; James Leach, Committee Member; Tarek Echekki, Committee Member; Herbert M. Eckerlin, Committee Chair
A comprehensive performance test has been conducted on the 3 kW amorphous silicon photovoltaic (PV) system on the roof of the Alternative Fuel Vehicle Garage of the North Carolina Solar Center. The purpose of this testing program was to measure the performance of the PV system, to determine if any deterioration has occurred over the past three years since installation, and to evaluate the performance of the individual circuits that makeup the PV system. Test conducted on the individual circuits of the PV system showed significant differences. This is particularly true for the two different solar panel models, which were installed using different techniques. Numerous tests were conducted on these circuits to isolate the problem. The current-voltage curves of the factory-laminated panels were much worse than the self-laminated panels. No cause of the poor performance could be definitively established. Discussions with the PV panel manufacturer are continuing to identify the cause of the variation in PV circuit performance. Comparisons made to performance data recorded in 2003-2004 show a similar kWh production over 3-month periods, this is encouraging. However, comparisons between global irradiance and AC power production show a 9% reduction in power production. Continued research is recommended to further evaluate the circuit issues and to study how PV panel temperatures can be reduced so as to improve over PV system efficiencies.
Field Study and Modeling of an Unglazed Transpired Solar Collector System
(2004-07-08) Maurer, Christine Carol; Richard R. Johnson, Committee Chair; Nancy Ma, Committee Member; James Leach, Committee Member
An unglazed transpired solar collector (UTC) consists of a perforated metal cladding mounted on the south side of a structure. Outdoor air is drawn through the collector for low temperature heating including preheating ventilation air, preheating combustion air, and crop drying. While UTC systems are more commonly used in the Northeast U.S. and Canada, they have not been installed as much in the southeast because of the short heating season. The NC Solar Center installed a data acquisition system to monitor the performance of a UTC system at a manufacturing facility in North Carolina. The main objectives of this project were to evaluate the performance of the components of the system and determine the energy collected and potential monetary savings from the system. The case study was used to understand the principles behind operation of these collectors and compare the monitoring results to previous models of collector performance. A simulation of a UTC system was built in TRNSYS and used to look at the potential for transpired collectors in warmer climates than where UTCs are typically installed. A heat transfer analysis was done to look at the possibility of the collector causing additional heat gain to the building in the summer. The results show that it is possible that the collector causes unwanted heat gain in the summer. Additional investigation could be done to characterize the flow conditions in bypass mode and validate theory with experimental data. Despite the short heating season, some industrial or commercial buildings could still benefit from the technology. The success of the technology depends on site characteristics and building conditions; therefore, transpired collector systems must be considered on a case by case basis. Even if the system works well, space heating is only a minor portion of the energy used in industrial facilities in North Carolina.
Thermal Conductivity and Permeability of Activated Carbon with Variance in Sample Porosity.
(2010-08-10) Harder, Abram; Richard Gould, Committee Chair; Robert Nagel, Committee Member; James Leach, Committee Member