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  • 1
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    Optimal control of sun tracking solar concentrators (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Application of the modern control theory to derive an optimal sun tracking control for a point focusing solar concentrator is presented. A standard tracking problem converted to regulator problem using a sun rate input achieves an almost zero steady state tracking error with the optimal control formulation. However, these control techniques are costly because optimal type algorithms require large computing systems, thus they will be used mainly as comparison standards for other types of control algorithms and help in their development.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    The sun-tracking control of solar collectors using high-performance step motors (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Sun-tracking solar energy-focusing devices involving a central receiver, thermionic conversion, or a distributed solar thermal collector system are described. The Perkins solar collector uses a fixed focal point about which an 18 m-diameter parabolic dish moves on tracks. The elevation axis also moves on a circular track. A microprocessor manipulates sun sensor information and sun ephemeris data to ensure correct placement. Stepper motors are digital devices which provide direct interface with digital electronics and a wide dynamic range, and could easily be associated with the microprocessors. Design philosophy, performance criteria, wind load analysis, and control system requirements are also discussed.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: Annual Symposium on Incremental Motion Control Systems and Devices; May 24, 1977 - May 27, 1977; Urbana, IL
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    NASA TECHNICAL REPORTS
  • 3
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    Efficiency degradation due to tracking errors for point focusing solar collectors (1978)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An important parameter in the design of point focusing solar collectors is the intercept factor which is a measure of efficiency and of energy available for use in the receiver. Using statistical methods, an expression of the expected value of the intercept factor is derived for various configurations and control law implementations. The analysis assumes that a radially symmetric flux distribution (not necessarily Gaussian) is generated at the focal plane due to the sun's finite image and various reflector errors. The time-varying tracking errors are assumed to be uniformly distributed within the threshold limits and allows the expected value calculation.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: ASME PAPER 78-WA/SOL-4 , American Society of Mechanical Engineers, Winter Annual Meeting; Dec 10, 1978 - Dec 15, 1978; San Francisco, CA
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    NASA TECHNICAL REPORTS
  • 4
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    Effects of pointing errors on receiver performance for parabolic dish solar concentrators (1978)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The effects of dynamic (moving) pointing errors on the performance of solar thermal receivers is investigated. Only point focusing types of solar collectors are considered. The key element in the study is the analytical derivation of the intercept factor that relates pointing errors to captured energy at the receiver. A detailed example using typical parameter values is modeled on the digital computer and demonstrates the theory and the dynamic nature of the problem.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: Intersociety Energy Conversion Engineering Conference; Aug 20, 1978 - Aug 25, 1978; San Diego, CA
    Format: text
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    NASA TECHNICAL REPORTS
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