Engineering topics

Kran, A.

Publications and source records attributed to Kran, A..

8 records

NASA NTRS1978

Contribution to solving the energy crisis - Simulating the prospects for low cost energy through silicon solar cells

PECAN (Photovoltaic Energy Conversion Analysis) is a highly interactive decision analysis and support system. It simulates the prospects for widespread use of solar cells for the generation of electrical power. PECAN consists of a set of integrated APL functions for evaluating the potential of terrestrial photovoltaics. Specifically, the system is a deterministic simulator, which translates present and future manufacturing technology into economic and financial terms, using the production unit concept. It guides solar cell development in three areas: tactical decision making, strategic planning, and the formulation of alternative options.

Kran, A.↗

NASA NTRS1978

Silicon ribbon technology assessment 1978-1986 - A computer-assisted analysis using PECAN

The paper presents a 1978-1986 economic outlook for silicon ribbon technology based on the capillary action shaping technique. The outlook is presented within the framework of two sets of scenarios, which develop strategy for approaching the 1986 national energy capacity cost objective of $0.50/WE peak. The PECAN (Photovoltaic Energy Conversion Analysis) simulation technique is used to develop a 1986 sheet material price ($50/sq m) which apparently can be attained without further scientific breakthrough.

Kran, A.↗

NASA NTRS1977

Silicon ribbon growth by a capillary action shaping technique

Substantial improvements in ribbon surface quality are achieved with a higher melt meniscus than that attainable with the film-fed (EFG) growth technique. A capillary action shaping method is described in which meniscus shaping for the desired ribbon geometry occurs at the vertex of a wettable die. As ribbon growth depletes the melt meniscus, capillary action supplies replacement material. Topics discussed cover experimental apparatus and growth procedures; die materials investigations, fabrication and evaluation; process development for 25 mm, 38 mm, 50 mm and 100 mm silicon ribbons; and long grain direct solidification of silicon. Methods for the structural and electrical characterization of cast silicon ribbons are assessed as well as silicon ribbon technology for the 1978 to 1986 period.

Schwuttke, G. H.↗

NASA NTRS1977

Silicon ribbon growth by a capillary action shaping technique

The crystal-growth method under investigation is a capillary action shaping technique. Meniscus shaping for the desired ribbon geometry occurs at the vertex of a wettable dye. As ribbon growth depletes the melt meniscus, capillary action supplies replacement material. The configuration of the technique used in our initial studies is shown. The crystal-growth method has been applied to silicon ribbons it was found that substantial improvements in ribbon surface quality could be achieved with a higher melt meniscus than that attainable with the EFG technique.

Schwuttke, G. H.↗

NASA NTRS1976

Silicon ribbon growth by a capillary action shaping technique

The crystal growth method described is a capillary action shaping technique. Meniscus shaping for the desired ribbon geometry occurs at the vertex of a wettable die. As ribbon growth depletes the melt meniscus, capillary action supplies replacement material. A capillary die is so designed that the bounding edges of the die top are not parallel or concentric with the growing ribbon. The new dies allow a higher melt meniscus with concomitant improvements in surface smoothness and freedom from SiC surface particles, which can degrade perfection.

Schwuttke, G. H.↗

NASA NTRS1976

Silicon ribbon growth by a capillary action shaping technique

The technique of silicon ribbon growth by the capillary action shaping is assessed for applicability to photovoltaic power device material. Ribbons 25 mm in width and up to 0.5 m in length have been grown from SiC dies, and some new characteristics of growth from such dies have been identified. Thermal modifiers have been studied, and systems were developed which reduce the frozen-in stress un silicon ribbons and improve the thickness uniformity of the ribbons. Preliminary spreading resistance measurements indicate that neither surface striations nor twin boundaries give rise to appreciable resistivity variations, but that large-angle grain boundaries cause local resistivity increases of up to 200%.

Schwuttke, G. H.↗

NASA NTRS1976

Alternative strategies for implementing silicon-ribbon technology for photovoltaic applications

Interactive computer models are being designed to support the development of technological and economic data required to define the potential of silicon sheet growth for large scale photovoltaic applications. Technology projection and sensitivity analysis suggest that single-ribbon growth systems offer the best potential for achieving low-cost silicon sheet material within the shortest period of time. Such systems must be highly reliable, be capable of near unattended growth, and feature automatic melt replenishment. Processing-technology improvement, such as the following, are the key elements for reducing the cost of silicon sheet material: (i) increasing ribbon width; (ii) speeding up the growth rate; and (iii) decreasing ribbon thickness. Such tasks should be pursued in that order to minimize sheet material cost. One interesting finding is that significant reductions in sheet material cost are achievable in the near future by increasing ribbon width to 5 cm.

Kran, A.↗

NASA NTRS1975

Low cost silicon solar arrays

Continuous growth methodology for silicon solar cell ribbons deals with capillary effects, die effects, thermal effects and crystal shape effects. Emphasis centers on the shape of the meniscus at the ribbon edge as a factor contributing to ribbon quality with respect to defect densities. Structural and electrical characteristics of edge defined, film-fed grown silicon ribbons are elaborated. Ribbon crystal solar cells produce AMO efficiencies of 6 to 10%.

Ravi, K. V.↗