Mission analysis of photovoltaic solar energy conversion. Volume IV. Supplementary studies

A discussion is presented of the most significant problems associated with the production and deployment of photovoltaic arrays. The principal chemical compounds to be used in the manufacture of silicon, gallium arsenide, and cadmium sulfide photovoltaic arrays are discussed with respect to physical and chemical properties, sources of the raw materials required to extract or synthesize these materials, the methods of manufacture, storage and handling in large quantities, transportation restrictions, spills, leaks, ignition and explosion. A discussion of safety hazards associated with the finished products is followed by an analysis of the toxicological properties of all raw, refined, and finished chemical species involved. The principal tool used in the evaluation of incentive strategies was a new Public Utility Financial Analysis and Planning Model which is described in some detail. After adaptation to match the characteristics of photovoltaic plants, it was used in the comparative evaluation of six different incentive strategies. The candidate strategies, the rationale for their selection, and the results of the comparative evaluation are presented. An account is given of an attempt to assess the full non-internalized costs of coal-fired power generation. A detailed description is given of the various damage elements and their associated societal costs for coal production, coal transportation, and coal-fired power generation. (MHR

Experimental Replication of an Aeroengine Combustion Instability

Combustion instabilities in gas turbine engines are most frequently encountered during the late phases of engine development, at which point they are difficult and expensive to fix. The ability to replicate an engine-traceable combustion instability in a laboratory-scale experiment offers the opportunity to economically diagnose the problem (to determine the root cause), and to investigate solutions to the problem, such as active control. The development and validation of active combustion instability control requires that the causal dynamic processes be reproduced in experimental test facilities which can be used as a test bed for control system evaluation. This paper discusses the process through which a laboratory-scale experiment was designed to replicate an instability observed in a developmental engine. The scaling process used physically-based analyses to preserve the relevant geometric, acoustic and thermo-fluid features. The process increases the probability that results achieved in the single-nozzle experiment will be scalable to the engine

Longitudinal-Mode Combustion Instabilities: Modeling and Experiments

Combustion instabilities can lead to increased development time and cost for aeroengine gas turbines. This problem has been evident in the development of very-low emissions stationary gas turbines, and will likely be encountered in the newer, more aggressive aeroengine designs. In order to minimize development time and cost, it is imperative that potential combustion dynamics issues be resolved using analyses and smaller-scale experimentation. This paper discusses a methodology through which a problem in a full-scale engine was replicated in a single-nozzle laboratory combustor. Specifically, this approach is valid for longitudinal and "bulk" mode combustion instabilities. An explanation and partial validation of the acoustic analyses that were used to achieve this replication are also included. This approach yields a testbed for the diagnosis of combustion dynamics problems and for their solution through passive and active control techniques

Graphene Growth Using a Solid Carbon Feedstock and Hydrogen

Graphene has been grown on Cu at elevated temperatures with different carbon sources (gaseous hydrocarbons and solids such as polymers); however the detailed chemistry occurring at the Cu surface is not yet known. Here, we explored the possibility of obtaining graphene using amorphous-carbon thin films, without and with hydrogen gas added. Graphene is formed only In the presence of H-2(g), which strongly suggests that gaseous hydrocarbons and/or their Intermediates are what yield graphene on Cu through the reaction of H-2(g) and the amorphous carbon. The large area, uniform monolayer graphene obtained had electron and hole mobilities of 2520 and 2050 cm(2) V-1 s(-1), respectively