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Title: Significant Improvements in Pyranometer Nighttime Offsets Using High-Flow DC Ventilation

Abstract

Ventilators are used to keep the domes of pyranometers clean and dry, but they affect the nighttime offset as well. This paper examines different ventilation strategies. For the several commercial single-black-detector pyranometers with ventilators examined here, high flow rate (50 CFM and higher), 12 VDC fans lower the offsets, lower the scatter, and improve the predictability of the offsets during the night compared with lower flow rate 35 CFM, 120 VAC fans operated in the same ventilator housings. Black-and-white pyranometers sometimes show improvement with DC ventilation, but in some cases DC ventilation makes the offsets slightly worse. Since the offsets for these black-and-white pyranometers are always small, usually no more than 1 Wm -2, whether AC or DC ventilated, changing their ventilation to higher CFM DC ventilation is not imperative. Future work should include all major manufacturers of pyranometers and unventilated, as well as, ventilated pyranometers. Lastly, an important outcome of future research will be to clarify under what circumstances nighttime data can be used to predict daytime offsets.

Authors:
 [1];  [2];  [1]
  1. Univ. of Colorado, Boulder, CO (United States); NOAA/Earth System Research Lab., Boulder, CO (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Wind and Water Technologies Office (EE-4W)
OSTI Identifier:
1369124
Alternate Identifier(s):
OSTI ID: 1364678
Report Number(s):
NREL/JA-5D00-67398
Journal ID: ISSN 0739-0572
Grant/Contract Number:
AC36-08GO28308
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Atmospheric and Oceanic Technology
Additional Journal Information:
Journal Volume: 34; Journal Issue: 6; Journal ID: ISSN 0739-0572
Publisher:
American Meteorological Society
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 47 OTHER INSTRUMENTATION; pyranometer; offsets; climate records; data processing; in situ atmospheric observations; instrumentation/sensors; quality assurance/control; surface observations

Citation Formats

Michalsky, Joseph J., Kutchenreiter, Mark, and Long, Charles N.. Significant Improvements in Pyranometer Nighttime Offsets Using High-Flow DC Ventilation. United States: N. p., 2017. Web. doi:10.1175/JTECH-D-16-0224.1.
Michalsky, Joseph J., Kutchenreiter, Mark, & Long, Charles N.. Significant Improvements in Pyranometer Nighttime Offsets Using High-Flow DC Ventilation. United States. doi:10.1175/JTECH-D-16-0224.1.
Michalsky, Joseph J., Kutchenreiter, Mark, and Long, Charles N.. Tue . "Significant Improvements in Pyranometer Nighttime Offsets Using High-Flow DC Ventilation". United States. doi:10.1175/JTECH-D-16-0224.1.
@article{osti_1369124,
title = {Significant Improvements in Pyranometer Nighttime Offsets Using High-Flow DC Ventilation},
author = {Michalsky, Joseph J. and Kutchenreiter, Mark and Long, Charles N.},
abstractNote = {Ventilators are used to keep the domes of pyranometers clean and dry, but they affect the nighttime offset as well. This paper examines different ventilation strategies. For the several commercial single-black-detector pyranometers with ventilators examined here, high flow rate (50 CFM and higher), 12 VDC fans lower the offsets, lower the scatter, and improve the predictability of the offsets during the night compared with lower flow rate 35 CFM, 120 VAC fans operated in the same ventilator housings. Black-and-white pyranometers sometimes show improvement with DC ventilation, but in some cases DC ventilation makes the offsets slightly worse. Since the offsets for these black-and-white pyranometers are always small, usually no more than 1 Wm-2, whether AC or DC ventilated, changing their ventilation to higher CFM DC ventilation is not imperative. Future work should include all major manufacturers of pyranometers and unventilated, as well as, ventilated pyranometers. Lastly, an important outcome of future research will be to clarify under what circumstances nighttime data can be used to predict daytime offsets.},
doi = {10.1175/JTECH-D-16-0224.1},
journal = {Journal of Atmospheric and Oceanic Technology},
number = 6,
volume = 34,
place = {United States},
year = {Tue Jun 20 00:00:00 EDT 2017},
month = {Tue Jun 20 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on June 20, 2018
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  • Accurate solar radiation measurements using pyranometers are required to understand radiative impacts on the Earth's energy budget, solar energy production, and to validate radiative transfer models. Ventilators of pyranometers, which are used to keep the domes clean and dry, also affect instrument thermal offset accuracy. This poster presents a high-level overview of the ventilators for single-black-detector pyranometers and black-and-white pyranometers. For single-black-detector pyranometers with ventilators, high-flow-rate (50-CFM and higher), 12-V DC fans lower the offsets, lower the scatter, and improve the predictability of nighttime offsets compared to lower-flow-rate (35-CFM), 120-V AC fans operated in the same type of environmental setup.more » Black-and-white pyranometers, which are used to measure diffuse horizontal irradiance, sometimes show minor improvement with DC fan ventilation, but their offsets are always small, usually no more than 1 W/m2, whether AC- or DC-ventilated.« less
  • Flow mechanism causing nightttime smog was investigated by analyzing 1) continuous records of meteorological data and concentration of oxidants (Ox) for 15 days and 2) aircraft data along the transportation route of a polluted air mass.
  • Attenuation of ventilator-synchronous pressure fluctuations of intracranial pressure has been demonstrated during high frequency ventilation in animal and human studies, but the consequences of this effect on cerebral blood flow have not been investigated in man. We compared the effects of high frequency jet ventilation and intermittent positive pressure ventilation on CBF in 24 patients investigated three hours after completion of open-heart surgery. The patients were investigated during three consecutive periods with standard sedation (morphine, pancuronium): a. IPPV; b. HFJV; c. IPPV. Partial pressure of arterial CO{sub 2} (PaCO{sub 2}: 4.5-5.5 kPa) and rectal temperature (35.5 to 37.5{degree}C) were maintainedmore » constant during the study. The CBF was measured by intravenous {sup 133}Xe washout technique. The following variables were derived from the cerebral clearance of {sup 133}Xe: the rapid compartment flow, the initial slope index, ie, a combination of the rapid and the slow compartment flows, and the ratio of fast compartment flow over total CBF (FF). Compared to IPPV, HFJV applied to result in the same mean airway pressure did not produce any change in pulmonary gas exchange, mean systemic arterial pressure, and cardiac index. Similarly, CBF was not significantly altered by HFJV. However, important variations of CBF values were observed in three patients, although the classic main determinants of CBF (PaCO{sub 2}, cerebral perfusion pressure, Paw, temperature) remained unchanged. Our results suggest that in patients with normal systemic hemodynamics, the effects of HFJV and IPPV on CBF are comparable at identical levels of mean airway pressure.« less