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Shape Control of Solar Collectors Using Shape Memory Alloy ActuatorsSolar collectors that are focused on a central receiver are designed with a mechanism for defocusing the collector or disabling it by turning it out of the path of the sun's rays. This is required to avoid damaging the receiver during periods of inoperability. In either of these two cases a fail-safe operation is very desirable where during power outages the collector passively goes to its defocused or deactivated state. This paper is principally concerned with focusing and defocusing the collector in a fail-safe manner using shape memory alloy actuators. Shape memory alloys are well suited to this application in that once calibrated the actuators can be operated in an on/off mode using a minimal amount of electric power. Also, in contrast to other smart materials that were investigated for this application, shape memory alloys are capable of providing enough stroke at the appropriate force levels to focus the collector. Design and analysis details presented, along with comparisons to test data taken from an actual prototype, demonstrate that the collector can be repeatedly focused and defocused within accuracies required by typical solar energy systems. In this paper the design, analysis and testing of a solar collector which is deformed into its desired shape by shape memory alloy actuators is presented. Computations indicate collector shapes much closer to spherical and with smaller focal lengths can be achieved by moving the actuators inward to a radius of approximately 6 inches. This would require actuators with considerably more stroke and some alternate SMA actuators are currently under consideration. Whatever SMA actuator is finally chosen for this application, repeatability and fatigue tests will be required to investigate the long term performance of the actuator.
Document ID
19960047688
Acquisition Source
Langley Research Center
Document Type
Conference Paper
Authors
Lobitz, D. W.
(Sandia National Labs. Albuquerque, NM United States)
Grossman, J. W.
(Sandia National Labs. Albuquerque, NM United States)
Allen, J. J.
(Sandia National Labs. Albuquerque, NM United States)
Rice, T. M.
(Sandia National Labs. Albuquerque, NM United States)
Liang, C.
(San Diego State Univ. San Diego, CA United States)
Davidson, F. M.
(San Diego State Univ. San Diego, CA United States)
Date Acquired
August 17, 2013
Publication Date
March 1, 1996
Publication Information
Publication: Proceedings of the 4th Annual Workshop: Advances in Smart Materials for Aerospace Applications
Subject Category
Metallic Materials
Accession Number
96N33298
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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