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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Evacuated all-glass concentric tube collector using air or liquid transfer mediums is very efficient at high temperatures. Collector can directly drive existing heating systems that are presently driven by fossil fuel with relative ease of conversion and less expense than installation of complete solar heating systems.
Black cobalt oxide coatings were deposited on thin layers of silver or gold which had been deposited on oxidized stainless steel substrates. The reflectance properties of these coatings were measured at various thicknesses of cobalt oxide for integrated values of the solar and infrared spectrum. The values of absorptance and emittance were calculated from the measured reflectance values before and after exposure in air at 650 C for 1000 hours. Also, these cobalt oxide/noble metal/oxide diffusion barrier coatings have absorptances greater than 0.90 and emittances of approximately 0.20 even after about 1000 hours at 650 C.
A discrete-gradient optimization algorithm is used to identify the parameters in a one-node and a two-node capacitance model of a flat-plate collector. Collector parameters are first obtained by a linear-least-squares fit to steady state data. These parameters, together with the collector heat capacitances, are then determined from unsteady data by use of the discrete-gradient optimization algorithm with less than 10 percent deviation from the steady state determination. All data were obtained in the indoor solar simulator at the NASA Lewis Research Center.
The spectral reflectance properties of black nickel electroplated over stainless steel and of black copper produced by oxidation of copper sheet were measured for various plating times of black nickel and for various lengths of time of oxidation of the copper sheet, and compared to black chrome over nickel and to converted zinc. It was determined that there was an optimum time for both plating of black nickel and for the oxidation of copper black. At this time the solar selective properties show high absorptance in the solar spectrum and low emittance in the infrared. The conditions are compared for production of optimum optical properties for black nickel, black copper, black chrome, and two black zinc conversions which at the same conditions had absorptances of 0.84, 0.90, 0.95, 0.84, and 0.92, respectively, and emittances of 0.18, 0.08, 0.09, 0.10, and 0.08, respectively.
System has only three components per cell. Cell parts are fabricated from readily available materials and, following a construction procedure which requires use of only simple handtools, can be mounted in place by one person.
System consists of three major components: vertical deflector assembly, stationary reflector, and motor driven tracking mechanism. Deflector assembly directs incident incoming energy to a vertical direction, using series of horizontally mounted vanes. Energy is then redirected via reflector to fixed collector.
This evaluation of the flat-plate collector system was designed to determine the number of flat-plate collectors required to generate a given amount of electricity with optimum efficiency. Variable parameters are the temperature of the heat-transport fluid, both to and from the collector field. In the analysis, the efficiency of the flat-plate collectors was coupled to the efficiency of the thermal cycle to calculate optimal overall system efficiencies. Overall system efficiencies for the system are on the order of 3.5 per cent or less. Over two million 4 ft-by-4 ft collectors would be required to produce 100,000 kW(e). Based on the results, it can be shown that the limiting factor in the use of the flat-plate collector system for electric power generation is the efficiency of the collectors. An increase in the overall system efficiency can occur only if the collector efficiency can be increased at higher surface temperatures.
Concentric glass-tube-envelope device surrounds flat-plate absorber having spectrally selective coating. Transparent envelope has antireflection coating. Heat-transfer medium is gas that circulates along hairpin path.
Similar to flat-plate collector, concentrator uses water lenses to achieve temperatures near 200 degrees Centigrade. Lens assembly consists of parallel cylindrical lenses made of glass or plastic shells, reducing manufacturing costs and improving portability.
Five-port ganged valve isolates collector from primary load system pressure and drains collectors, allowing use of direct heating with all its advantages. Valve is opened and closed by same switch that controls pump or by temperature sensor set at O C, while providing direct dump option.
A flat plate collector employing a mild steel, pressure-expanded absorber plate has been developed. It is capable of energy output levels commensurate with the requirements of driving an absorption refrigeration system while operating at efficiency levels in the 35-40% range. Selective absorber surfaces of black chrome over nickel and black copper over copper were analyzed and prototype collectors containing each type of absorber plating were fabricated and tested for performance. Criteria applied to the cost effectiveness analysis of the collector included both the energy output per unit area and the collector fabrication cost per unit area.
Four reports trace development from preliminary design through delivery of hardware. Developmental test, including airflow, air temperature, and efficiency are discussed in reports, as are qualification tests on prototypes and final acceptance tests. Qualification test program includes measurements tests, and structural analysis.
Package includes installation, operation and maintenance manual for collector, analysis of safety hazards, special handling instructions, materials list, installation drawings, and warranty and certification statement. Manual includes instructions for roof preparation and for preparing collector for installation. Several pages are devoted to major and minor repairs.
Report describes program to determine thermal performance and structural characteristics of selected hot-air collectors in both real and simulated environmental conditions.
Report presents test procedures and results of program to obtain thermal performance data on liquid, incident-angle-modifier, heat-loss-coefficient, and stagnation tests.
The installation and layout design, and parts fabrication are described. The master development schedule for the design of the system is also included.
The test procedure used and the test results obtained during an evaluation test program to obtain thermal efficiency performance data are presented. The flat plate collector used water/prestone antifreeze solution as the working fluid.
Testing of the evacuated tubular air collector in conjunction with air/liquid heat exchange and liquid storage elements was completed. Test results emphasize matching of heat exchanger and collector characteristics with specific attention to the dynamic response of each of the elements.