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Zero Energy Communities with Central Solar Plants using Liquid Desiccants and Local Storage: Preprint

Description: The zero energy community considered here consists of tens to tens-of-thousands of residences coupled to a central solar plant that produces all the community's electrical and thermal needs. A distribution network carries fluids to meet the heating and cooling loads. Large central solar systems can significantly reduce cost of energy vs. single family systems, and they enable economical seasonal heat storage. However, the thermal distribution system is costly. Conventional district heating/cooling systems use a water/glycol solution to deliver sensible energy. Piping is sized to meet the peak instantaneous load. A new district system introduced here differs in two key ways: (i) it continuously distributes a hot liquid desiccant (LD) solution to LD-based heating and cooling equipment in each home; and (ii) it uses central and local storage of both LD and heat to reduce flow rates to meet average loads. Results for piping sizes in conventional and LD thermal communities show that the LD zero energy community reduces distribution piping diameters meeting heating loads by {approx}5X and meeting cooling loads by {approx}8X for cooling, depending on climate.
Date: August 1, 2012
Creator: Burch, J.; Woods, J.; Kozubal, E. & Boranian, A.
Partner: UNT Libraries Government Documents Department

Zero energy homes: Combining energy efficiency and solar energy technologies

Description: In a typical Florida house, air-conditioning accounts for about 35% of all the electricity the home uses. As the largest single source of energy consumption in Florida, a home's air-conditioning load represents the biggest energy challenge facing Florida residents. The Florida Solar Energy Center designed a project to meet this challenge. Two homes were built with the same floor plan on near-by lots. The difference was that one (the control home) conformed to local residential building practices, and the other (the Zero Energy home) was designed with energy efficiency in mind and a solar technology system on the roof. The homes were then monitored carefully for energy use. The projects designers were looked to answer two questions: (1) could a home in a climate such as central Florida be engineered and built so efficiently that a relatively small PV system would serve the majority of its cooling needs--and even some of its daytime electrical needs; and (2) would that home be as comfortable and appealing as the conventional model built alongside it? The answer was yes, even though it was conducted in the summer of 1998--one of the hottest summers on record in Florida.
Date: March 9, 2000
Creator: National Renewable Energy Laboratory (U.S.)
Partner: UNT Libraries Government Documents Department

ZnMgO by APCVD Enabling High-Performance Mid-bandgap CIGS on Polyimide Modules: October 2009--October 2010

Description: This Pre-Incubator project was designed to increase the 'real world' CIGS based photovoltaic module performance and decrease the Levelized Cost of Energy (LCOE) of systems utilizing those modules compared to our traditional CIGS based photovoltaic modules. This was enabled by a) increasing the CIGS bandgap and b) developing better matched device finishing layers to the mid-bandgap CIGS based photovoltaics; including window and buffer layers (and eventually the TCO). Incremental progress in the novel device performance was demonstrated throughout the program, and ultimately achieved performance results that exceeded the milestones ahead of schedule. Metal-oxide buffer layer devices with mid-bandgap CIGS alloys on polyimide substrates were produced with efficiencies of over 12%. Corresponding mid-bandgap devices with CdS buffers produced over 13% efficient devices. Furthermore, no obvious degradation in the device performance has been observed to date, after proper storage ambient of the different types of unencapsulated devices were identified.
Date: April 1, 2011
Creator: Woods, L.
Partner: UNT Libraries Government Documents Department

ZnO:Al Doping Level and Hydrogen Growth Ambient Effects on CIGS Solar Cell Performance: Preprint

Description: Cu(In,Ga)Se2 (CIGS) photovoltaic (PV) cells require a highly conducting and transparent electrode for optimum device performance. ZnO:Al films grown from targets containing 2.0 wt.% Al2O3 are commonly used for this purpose. Maximum carrier mobilities of these films grown at room temperature are ~20-25 cm2V-1s-1. Therefore, relatively high carrier concentrations are required to achieve the desired conductivity, which leads to free carrier absorption in the near infrared (IR). Lightly doped films (0.05 - 0.2 wt.% Al2O3), which show less IR absorption, reach mobility values greater than 50 cm2V-1s-1 when deposited in H2 partial pressure. We incorporate these lightly doped ZnO:Al layers into CIGS PV cells produced at the National Renewable Energy Laboratory (NREL). Preliminary results show quantum efficiency values of these cells rival those of a past world-record cell produced at NREL that used 2.0 wt.% Al-doped ZnO films. The highest cell efficiency obtained in this trial was 18.1%.
Date: May 1, 2008
Creator: Duenow, J. N.; Gessert, T. A.; Wood, D. M.; Egaas, B.; Noufi, R. & Coutts,T. J.
Partner: UNT Libraries Government Documents Department