3,307 research outputs found
Large solar arrays
A spectrophotovoltaic converter, a thermophotovoltaic converter, a cassegrainian concentrator, a large silicon cell blanket, and a high flux approach are among the concepts being investigated as part of the multihundred kW solar array program for reducing the cost of photovoltaic energy in space. These concepts involve a range of technology risks, the highest risk being represented by the thermophotovoltaics and spectrophotovoltaics approaches which involve manipulation to of the incoming spectrum to enhance system efficiency. The planar array (solar blanket) has no technology risk and a moderate payback. The primary characteristics, components, and technology concerns of each of these concepts are summarized. An orbital power platform mission in the late 1980's is being used to allow a coherent technology advancement program in order to achieve a ten year life with maintenance at a capital recurring cost of $30/watt based on 1978 dollars
Solar array systems
The recent past, present state-of-the-art, and future needs in the area of large photovoltaic solar arrays are discussed. In the past most attention was focused upon performance whereas in the future most of the effort should go into cost reduction. Suggestions are made regarding possible approaches to reducing cost such as on-orbit maintenance, extended lifetime, solar concentrators, and high-voltage modular concepts
Transition Metal-Ethylene Complexes as High-Capacity Hydrogen Storage Media
From first-principles calculations, we predict that a single ethylene
molecule can form a stable complex with two transition metals (TM) such as Ti.
The resulting TM-ethylene complex then absorbs up to ten hydrogen molecules,
reaching to gravimetric storage capacity of 14 wt%. Dimerization,
polymerizations and incorporation of the TM-ethylene complexes in nanoporous
carbon materials have been also discussed. Our results are quite remarkable and
open a new approach to high-capacity hydrogen storage materials discovery.Comment: 5 pages, 4 figures, additional content, Phys. Rev. Lett. in pres
Toward better minimum tillage for south-coastal sandplain soils
Seventeen farmers compared their conventional cropping practices with some form of minimum tillage cropping. The minimum tilled crops yielded 21 percent less grain than the conventionally sown crops. The reasons for these decreased yields were in most cases related to inexperienced management. The minimum tilled treatments usually had very poor weed kill strategies which often resulted in large weeds at sowing, very cloddy seed-beds, and numerous insects in the young crops
On the melting of the nanocrystalline vortex matter in high-temperature superconductors
Multilevel Monte Carlo simulations of the vortex matter in the
highly-anisotropic high-temperature superconductor BiSrCaCuO
were performed. We introduced low concentration of columnar defects satisfying
. Both the electromagnetic and Josephson interactions among
pancake vortices were included. The nanocrystalline, nanoliquid and homogeneous
liquid phases were identified in agreement with experiments. We observed the
two-step melting process and also noted an enhancement of the structure factor
just prior to the melting transition. A proposed theoretical model is in
agreement with our findings.Comment: 4 figure
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