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Technical Briefs

On the Development of a Low Cost Pyrheliometer

[+] Author and Article Information
Michael Gnos1

 V. P. of Research Sustainable Energy Technologies, 1404 Hamlin Avenue Unit G, St. Cloud, FL 34771mgnos@sustaintech.com

Brenton Greska

 V. P. of Research Sustainable Energy Technologies, 1404 Hamlin Avenue Unit G, St. Cloud, FL 34771mgnos@sustaintech.com

Anjaneyulu Krothapalli

Eminent Scholar Professor and Director Energy and Sustainability Center, Department of Mechanical Engineering,  Florida State University, Tallahassee, FL 32306akrothapalli@esc.fsu.edu

1

Corresponding author.

J. Sol. Energy Eng 133(3), 034501 (Aug 17, 2011) (7 pages) doi:10.1115/1.4004266 History: Received November 12, 2010; Revised May 18, 2011; Published August 17, 2011; Online August 17, 2011

A low cost pyrheliometer, based on a thermoelectric sensor, was developed at the Energy and Sustainability Center at the Florida State University. In addition, an inexpensive double-axis tracking device, capable of autonomous operation, enables the pyrheliometer to operate as a stand-alone system. Widely available off-the-shelf components were used and compromises in accuracy and time responsiveness were made in order to keep the cost low. The obtained data was compared with an Eppley Normal Incidence Pyrheliometer (NIP) using model ST-1 solar tracker. Steady state values of irradiance were measured with an accuracy better than ±2%. Transient measurements are time delayed by a thermal lag of about 2 min, which leads to a high error for instantaneous measured values. However, the integrated irradiance over the course of any given day yields irradiation values with accuracy better than ±2%, even on days when the sun and clouds quickly alternate. Based on a manufacturing cost analysis, the prototype pyrheliometer system is anticipated to cost an order of magnitude less than commercially available products if mass-produced.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Various parameters to consider in the experimental setup, (a) reflectance of VIS coated acrylic lens within the solar spectrum and (b) concentrated sun spot size in comparison to receiver disk size

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Figure 2

Alignment control with the use of a center bore, (a) overview of the alignment control and (b) close up view of the center with the sun spot

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Figure 3

ESC-MG-2-F4 pyrheliometer with double axis tracking system

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Figure 4

Receiver disk, (a) determination of receiver disk size and (b) energy balance on receiver disk

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Figure 5

Determination of unknown parameters from transient measurements (a) determination of the effective heat transfer coefficient from transient experimental data for F#4 and (b) determination of the optical efficiency from transient experimental data for F#4

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Figure 6

Instantaneous irradiance measured with the ESC-MG-2-F4 and the Eppley NIP on a very clear day

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Figure 7

Instantaneous difference in irradiance between the Eppley NIP and the ESC-MG-2-F4 on a very clear day

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Figure 8

Instantaneous irradiance measured with the ESC-MG-2-F4 and the Eppley NIP for a partly cloudy day

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Figure 9

Instantaneous irradiance measured with the ESC-MG-2-F4 and the Eppley NIP for a mostly cloudy day

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Figure 10

Instantaneous irradiance measured with the ESC-MG-2-F4 and the Eppley NIP for a sunny day with special interest for large zenith angles

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Figure 11

Instantaneous difference in irradiance between the Eppley NIP and the ESC-MG-2-F4 for a sunny day with special interest for large zenith angles

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Figure 12

Time response for the cooling off and heating up process of the ESC-MG-2-F4 and the Eppley NIP

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