• Allison, P. D., 1999: Multiple Regression: A Primer. Pine Forge Press, 202 pp.

  • Bush, B. C., , Valero F. P. J. , , and Simpson A. S. , 2000: Characterization of thermal effects in pyranometers: A data correction algorithm for improved measurement of surface insolation. J. Atmos. Oceanic Technol., 17, 165175, doi:10.1175/1520-0426(2000)017<0165:COTEIP>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Carlund, T., 2013: Baltic region pyrheliometer comparison 2012, WMO Instruments and Observing Methods Rep. IOM 112, 46 pp.

  • Cess, R. D., , Taotao Q. , , and Moguo S. , 2000: Consistency tests applied to the measurement of total, direct, and diffuse shortwave radiation at the surface. J. Geophys. Res., 105, 24 88124 887, doi:10.1029/2000JD900402.

    • Search Google Scholar
    • Export Citation
  • Drummond, K. L., , and Roche J. J. , 1965: Corrections to be applied to measurements made with Eppley (and other) spectral radiometers when used with Schott colored glass filters. J. Appl. Meteor., 4, 741744, doi:10.1175/1520-0450(1965)004<0741:CTBATM>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Dutton, E. G., , Michalsky J. J. , , Stoffel T. , , Forgan B. W. , , Hickey J. , , Nelson D. W. , , Alberta T. L. , , and Reda I. , 2001: Measurement of broadband diffuse solar irradiance using current commercial instrumentation with a correction for thermal offset errors. J. Atmos. Oceanic Technol., 18, 297314, doi:10.1175/1520-0426(2001)018<0297:MOBDSI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Gueymard, C. A., , and Myers D. R. , 2009: Evaluation of conventional and high-performance routine solar radiation measurements for improved solar resource, climatological trends and radiative modeling. Sol. Energy, 83, 171185, doi:10.1016/j.solener.2008.07.015.

    • Search Google Scholar
    • Export Citation
  • Gulbrandsen, A., 1978: On the use of pyranometers in the study of spectral solar radiation and atmospheric aerosols. J. Appl. Meteor., 17, 899904, doi:10.1175/1520-0450(1978)017<0899:OTUOPI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Haeffelin, M., , Kato S. , , Smith A. M. , , Rutledge C. K. , , Charlock T. P. , , and Mahan J. R. , 2001: Determination of the thermal offset of the Eppley precision spectral pyranometer. Appl. Opt., 40, 472484, doi:10.1364/AO.40.000472.

    • Search Google Scholar
    • Export Citation
  • Ji, Q., , and Tsay S.-C. , 2010: A novel nonintrusive method to resolve the thermal dome effect of pyranometers: Instrumentation and observational basis. J. Geophys. Res., 115, D00K21, doi:10.1029/2009JD013483.

    • Search Google Scholar
    • Export Citation
  • Kipp & Zonen, 2000: Instruction manual for CM11 pyranometer and CM14 albedometer. Version 0805, 62 pp.

  • Kipp & Zonen, 2003: Instruction manual for CG1 pyrgeometer and CG2 net pyrgeometer. Version 0204, 63 pp.

  • Kipp & Zonen, 2008: Instruction manual for SOLYS 2, 2-Axis Sun Tracker. Version 0811, 66 pp.

  • Michalsky, J. J., and et al. , 2005: Toward the development of a diffuse horizontal shortwave irradiance working standard. J. Geophys. Res., 110, D06107, doi:10.1029/2004JD005265.

    • Search Google Scholar
    • Export Citation
  • PASCO, 2014: Fast Response Temperature Probe manual. Instruction sheet for the PASCO models PS-2135, 012-08475E, 2 pp.

  • Patsalides, M., and et al. , 2007: The effect of solar irradiance on the power quality behaviour of grid connected photovoltaic systems. Proc. Int. Conf. on Renewable Energy and Power Quality (ICREPQ’07), Seville, Spain, University of Vigo, 284. [Available online at http://www.icrepq.com/icrepq07/284-patsalides.pdf.]

  • Patsalides, M., , Stavrou A. , , Efthymiou V. , , and Georghiou G. E. , 2012: Towards the establishment of maximum PV generation limits due to power quality constraints. Int. J. Electr. Power Energy Syst., 42, 285298, doi:10.1016/j.ijepes.2012.03.043.

    • Search Google Scholar
    • Export Citation
  • Philipona, R., 2002: Underestimation of solar global and diffuse radiation measured at Earth’s surface. J. Geophys. Res., 107, 4654, doi:10.1029/2002JD002396.

    • Search Google Scholar
    • Export Citation
  • Reda, I., , Stoffel T. , , and Myers D. , 2003: A method to calibrate a solar pyranometer for measuring reference diffuse irradiance. Sol. Energy, 74, 103112, doi:10.1016/S0038-092X(03)00124-5.

    • Search Google Scholar
    • Export Citation
  • Sanchez, G., , Serrano A. , , Cancillo M. L. , , and Garcia J. A. , 2015: Pyranometer thermal offset: Measurement and analysis. J. Atmos. Oceanic Technol., 32, 234246, doi:10.1175/JTECH-D-14-00082.1.

    • Search Google Scholar
    • Export Citation
  • Smith, A. M., 1999: Prediction and measurement of thermal exchange within pyranometers. M.S. thesis, Dept. of Mechanical Engineering, Virginia Polytechnic Institute and State University, 64 pp.

  • Stine, R. A., 1995: Graphical interpretation of variance inflation factors. Amer. Stat. Assoc., 49, 5356.

  • Vignola, F., , Long C. N. , , and Reda I. , 2007: Evaluation of methods to correct for IR loss in Eppley PSP diffuse measurements. Optical Modeling and Measurements for Solar Energy Systems, D. R. Myers, Ed., International Society for Optical Engineering (SPIE Proceedings, Vol. 6652), 66520A, doi:10.1117/12.734474.

  • Vignola, F., , Long C. N. , , and Reda I. , 2008: Modeling IR radiative loss from Eppley PSP pyranometer. Optical Modeling and Measurements for Solar Energy Systems II, B. K. Tsai, Ed., International Society for Optical Engineering (SPIE Proceedings, Vol. 7046), 70460E, doi:10.1117/12.796457.

  • Vignola, F., , Long C. N. , , and Reda I. , 2009: Testing a model of IR radiative losses. Optical Modeling and Measurements for Solar Energy Systems III, B. K. Tsai, Ed., International Society for Optical Engineering (SPIE Proceedings, Vol. 7410), 741003, doi:10.1117/12.826325.

  • Wang, K., , Dickinson R. E. , , Ma Q. , , Augustine J. A. , , and Wild M. , 2013: Measurement methods affect the observed global dimming and brightening. J. Climate, 26, 41124120, doi:10.1175/JCLI-D-12-00482.1.

    • Search Google Scholar
    • Export Citation
  • WMO, 1996: Guide to Meteorological Instruments and Methods of Observation. 6th ed. WMO-8, 501 pp.

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Correcting Daytime Thermal Offset in Unventilated Pyranometers

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  • 1 Department of Physics, University of Extremadura, Badajoz, Spain
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Abstract

A main source of error in solar radiation measurements is the thermal offset inherent to pyranometers. Despite acknowledgment of its importance, its correction has been widely ignored for several decades. This neglect may have caused a generalized underestimation in solar radiation measurements. This study focuses on the correction of this error in solar irradiance measurements. For this aim a plethora of correction models built as a linear combination of several environmental variables related to the ambient temperature and to the incoming radiation were proposed. The models are fitted to experimental measurements obtained during capping events and, finally, their performance is evaluated and compared. The main results indicate that models with only one independent variable moderately correct the thermal offset error. These simple models are useful when no additional instrumentation other than the pyranometer is available. On the other hand, the more complex models show the best performance, with a coefficient of determination R2 over 0.8, an RMSE under 2 W m−2, and an absolute value of mean bias error (MBE) under 0.5 W m−2. Additionally, these models are used to study the differences between nighttime and daytime correction, revealing the unsuitability of using nighttime-fitted models to correct the daytime thermal offset. The general validity of the models is tested by their application to two different pyranometers. Results indicate that, whereas the factors involved in the best-performing models are the same, the values of the loading coefficients differ and therefore must be specifically calculated for each pyranometer.

Corresponding author address: Antonio Serrano, Department of Physics, University of Extremadura, Avda. de Elvas s/n, 06071 Badajoz, Spain. E-mail: asp@unex.es

Abstract

A main source of error in solar radiation measurements is the thermal offset inherent to pyranometers. Despite acknowledgment of its importance, its correction has been widely ignored for several decades. This neglect may have caused a generalized underestimation in solar radiation measurements. This study focuses on the correction of this error in solar irradiance measurements. For this aim a plethora of correction models built as a linear combination of several environmental variables related to the ambient temperature and to the incoming radiation were proposed. The models are fitted to experimental measurements obtained during capping events and, finally, their performance is evaluated and compared. The main results indicate that models with only one independent variable moderately correct the thermal offset error. These simple models are useful when no additional instrumentation other than the pyranometer is available. On the other hand, the more complex models show the best performance, with a coefficient of determination R2 over 0.8, an RMSE under 2 W m−2, and an absolute value of mean bias error (MBE) under 0.5 W m−2. Additionally, these models are used to study the differences between nighttime and daytime correction, revealing the unsuitability of using nighttime-fitted models to correct the daytime thermal offset. The general validity of the models is tested by their application to two different pyranometers. Results indicate that, whereas the factors involved in the best-performing models are the same, the values of the loading coefficients differ and therefore must be specifically calculated for each pyranometer.

Corresponding author address: Antonio Serrano, Department of Physics, University of Extremadura, Avda. de Elvas s/n, 06071 Badajoz, Spain. E-mail: asp@unex.es
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