Title page for ETD etd-06282001-131406


Type of Document Master's Thesis
Author Carnicero Dominguez, Bernardo Antonio
Author's Email Address bcarnice@vt.edu
URN etd-06282001-131406
Title Characterization of Pyranometer Thermal Offset and Correction of Historiacal Data
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Haeffelin, Martial P. Committee Chair
Mahan, James Robert Committee Member
Scott, Elaine P. Committee Member
Keywords
  • Correction of data
  • Cloud cover fraction
  • net IR
  • Pyranometer
  • Thermal offset
  • Pyrgeometer
Date of Defense 2001-06-15
Availability unrestricted
Abstract
The Eppley Precision Pyranometer (PSP) is a

radiometer used in networks around the world to measure

downwelling and upwelling diffuse and total hemispherical

broadband solar irradiances. PSP's present an offset in the

signal, called thermal offset, produced by a radiation heat

exchange between the glass dome, which defines the spectral

throughput and the detector. This offset can reach up to 15\% of

the total value of the signal when measuring diffuse irradiance

under clear sky conditions. The thermal offset is characterized by

monitoring the temperature gradient between the dome and detector

using thermistors at key locations. The temperatures are acquired

by using thermistors. Relationships between the thermal offset and

the temperature gradient are established using nighttime data and

subsequently used to estimate the offset during daytime. To

correct historical data the thermal offset is related to other

variables such as the output of a Precision Infrared Pyrgeometer

(PIR) or the fraction of cloud cover in the sky. The use of

thermistors is a very reliable method to estimate and correct the

thermal offset. The relationships between the offset and the IR

output and between the offset and the cloud cover fraction provide

good estimates of the thermal offset in historical data sets,

reducing it 60\% to 100\% depending on the instrument and the

relationship used.

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  Appendix1.pdf 825.83 Kb 00:03:49 00:01:57 00:01:43 00:00:51 00:00:04
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  Chapter6.pdf 48.16 Kb 00:00:13 00:00:06 00:00:06 00:00:03 < 00:00:01
  References.pdf 47.84 Kb 00:00:13 00:00:06 00:00:05 00:00:02 < 00:00:01

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