5 research outputs found
Recommended from our members
Tandem Filter Development for Thermophotovoltaic Energy Conversion from January 2003 to February 2006
The intent of this report is to summarize the tandem filter development for spectral control of thermophotovoltaic energy conversion from January 2003 to the termination of the program in February 2006 and to closeout tandem filter development in order to capture the knowledge gained from the development effort. Over the last three years, the goals of the tandem filter development have been the following: (1) Study the limits of the design of the interference optical coatings component of a tandem filter in order to develop higher performance designs; (2) Enhance the fabrication process of the optical interference coatings to increase the fidelity with the intended design and allow more complex, higher performing designs; (3) Support TPV module testing by providing tandem filters and assembly assistance; (4) Identify and develop materials for optical interference coatings that are stable at higher temperatures than current materials; and (5) Improve the understanding of the directional and spectral reflectance and transmittance characterization of the completed tandem filters to insure the veracity of the characterization data and to provide useful feedback to the tandem filter development process. This development effort has been a collaboration between KAPL and its contracted development partner, Rugate Technologies Inc
Recommended from our members
Reduction of Thermal Conductivity in Wafer-Bonded Silicon
Blocks of silicon up to 3-mm thick have been formed by directly bonding stacks of thin wafer chips. These stacks showed significant reductions in the thermal conductivity in the bonding direction. In each sample, the wafer chips were obtained by polishing a commercial wafer to as thin as 36 {micro}m, followed by dicing. Stacks whose starting wafers were patterned with shallow dots showed greater reductions in thermal conductivity. Diluted-HF treatment of wafer chips prior to bonding led to the largest reduction of the effective thermal conductivity, by approximately a factor of 50. Theoretical modeling based on restricted conduction through the contacting dots and some conduction across the planar nanometer air gaps yielded fair agreement for samples fabricated without the HF treatment
Recommended from our members
Development of Front Surface, Spectral Control Filters with Greater Temperature Stability for Thermophotovoltaic Energy Conversion
Spectral control is an important consideration in achieving high conversion efficiency with thermophotovoltaic (TPV) energy conversion systems. TPV modules using front surface filters as the primary spectral control device have demonstrated conversion efficiencies in excess of 20% with power densities in excess of 0.4 W/cm{sup 2}. The front surface filter we are developing is a short pass, long wavelength reflection filter consisting of an interference filter deposited on a plasma filter. The materials used in the interference filter must exhibit high broad band transmission and good film quality and sufficient temperature stability at the operating temperature of the TPV cells and over any potential temperature excursions that may occur. Three high refractive index materials that offer good potential for use in TPV spectral control filters are antimony selenide (Sb{sub 2}Se{sub 3}), antimony sulfide (Sb{sub 2}S{sub 3}), and gallium telluride (GaTe). The highest spectral efficiency has been demonstrated using Sb{sub 2}Se{sub 3}; however this material develops significant near infrared (NIR, 0.72-2.5 {micro}m) absorption at temperatures in excess of 90 C. The other two materials are being developed as high temperature alternatives to Sb{sub 2}Se{sub 3}. TPV filters using GaTe and Sb{sub 2}S{sub 3} have been designed and fabricated, and initial results indicate that GaTe based filters are capable of operation at temperatures of 150 C or greater. Measured performance of TPV filters containing Sb{sub 2}Se{sub 3}, GaTe and Sb{sub 2}S{sub 3} are presented, along with the impact that these have on TPV module performance
Recommended from our members
Engineering Spectral Control Using Front Surface Filters for Maximum TPV Energy Conversion System Performance
Energy conversion efficiencies of better than 23% have been demonstrated for small scale tests of a few thermophotovoltaic (TPV) cells using front surface, tandem filters [1,2]. The engineering challenge is to build this level of efficiency into arrays of cells that provide useful levels of energy. Variations in cell and filter performance will degrade TPV array performance. Repeated fabrication runs of several filters each provide an initial quantification of the fabrication variation for front surface, tandem filters for TPV spectral control. For three performance statistics, within-run variation was measured to be 0.7-1.4 percent, and run-to-run variation was measured to be 0.5-3.2 percent. Fabrication runs using a mask have been shown to reduce variation across interference filters from as high 8-10 percent to less than 1.5 percent. Finally, several system design and assembly approaches are described to further reduce variation