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Title: Evaluation of Methods to Correct for IR Loss in Eppley PSP Diffuse Measurements

Abstract

The IR loss in diffuse measurements made by thermopile pyranometers is examined. Diffuse measurements are used for the study of IR losses to minimize the effects of beam irradiance and therefore much of the cosine response error influences. Specifically, diffuse measurements of an Eppley PSP pyranometer are compared to those made with a Schenk Star pyranometer. Eppley B&W and Star type pyranometers suffer minimal IR loss because the reference and receiving junctions of the thermopile are at the same thermal level. The difference between diffuse values can be attributed to calibration and cosine response errors as well as IR loss. Therefore it is necessary to separate out the various sources of error and examination of the differences over various times of the year can help, at least for systematic errors. Several methods of correcting for IR loss will be examined. First subtracting out the average nighttime offset during the day will be tested. Next an extrapolation between early morning and late evening offsets will be tested. This should help eliminate the IR offset in both the morning and evening, but underestimate the IR losses during the rest of the day. Correlations of the remaining IR losses with temperature, relative humidity,more » and irradiance will be evaluated. In addition, the IR losses will be studied both for clear days and for totally overcast periods. Pyrgeometer measurements will also be compared to the estimated IR losses. The above measurements and comparisons will help quantify the magnitude and variation of the IR losses.« less

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
962050
Report Number(s):
PNNL-SA-56395
KP1205010; TRN: US200919%%363
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Conference
Resource Relation:
Conference: Proceedings of SPIE, Optical Modeling and Measurements for Solar Energy Systems, 6652:Art. No. 66520A
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; CALIBRATION; EVALUATION; EXTRAPOLATION; HUMIDITY; PYRANOMETERS; RADIANT FLUX DENSITY; SIMULATION; SOLAR ENERGY; THERMOCOUPLES

Citation Formats

Vignola, F, Long, Charles N, and Reda, I. Evaluation of Methods to Correct for IR Loss in Eppley PSP Diffuse Measurements. United States: N. p., 2007. Web. doi:10.1117/12.734474.
Vignola, F, Long, Charles N, & Reda, I. Evaluation of Methods to Correct for IR Loss in Eppley PSP Diffuse Measurements. United States. https://doi.org/10.1117/12.734474
Vignola, F, Long, Charles N, and Reda, I. 2007. "Evaluation of Methods to Correct for IR Loss in Eppley PSP Diffuse Measurements". United States. https://doi.org/10.1117/12.734474.
@article{osti_962050,
title = {Evaluation of Methods to Correct for IR Loss in Eppley PSP Diffuse Measurements},
author = {Vignola, F and Long, Charles N and Reda, I},
abstractNote = {The IR loss in diffuse measurements made by thermopile pyranometers is examined. Diffuse measurements are used for the study of IR losses to minimize the effects of beam irradiance and therefore much of the cosine response error influences. Specifically, diffuse measurements of an Eppley PSP pyranometer are compared to those made with a Schenk Star pyranometer. Eppley B&W and Star type pyranometers suffer minimal IR loss because the reference and receiving junctions of the thermopile are at the same thermal level. The difference between diffuse values can be attributed to calibration and cosine response errors as well as IR loss. Therefore it is necessary to separate out the various sources of error and examination of the differences over various times of the year can help, at least for systematic errors. Several methods of correcting for IR loss will be examined. First subtracting out the average nighttime offset during the day will be tested. Next an extrapolation between early morning and late evening offsets will be tested. This should help eliminate the IR offset in both the morning and evening, but underestimate the IR losses during the rest of the day. Correlations of the remaining IR losses with temperature, relative humidity, and irradiance will be evaluated. In addition, the IR losses will be studied both for clear days and for totally overcast periods. Pyrgeometer measurements will also be compared to the estimated IR losses. The above measurements and comparisons will help quantify the magnitude and variation of the IR losses.},
doi = {10.1117/12.734474},
url = {https://www.osti.gov/biblio/962050}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Sep 13 00:00:00 EDT 2007},
month = {Thu Sep 13 00:00:00 EDT 2007}
}

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