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Quality of ground data for assessment and benchmarking

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Quality of ground data for assessment and benchmarking

  1. 1. Quality of ground data for Assessment and Benchmarking L. Ramírez, J. Polo, L.F.Zarzalejo, L. Martín, A. Navarro CIEMAT (Energy department – Solar Platform of Almería)4th Meeting IEA SHC Task 36 Hamburg 23-25 Oct 2007
  2. 2. Objective Model development, benchmarking exercises, assessment of models could be strongly affected by the quality of the solar radiation ground data. As a consequence, quality checking of ground data use to be a first step prior to model development or assessment, etc.. Excepting the case of BSRN, ARM, WRC etc, many times ground databases with unknown quality criteria are used. What quality criteria are then available? Are there consensus? Are them complete enough? Any guide on how to use solar radiation data should include a chapter for data quality 4th Meeting IEA SHC Task 36 Hamburg 23-25 Oct 2007
  3. 3. Background on Quality ProceduresBSRN  Measurements with physical sense (Solar Constant, I0, .)  Extremely rare values (Idiffuse > 700 Wm-2)  Crossing components (Iglobal=Ibeamcosθ+Idiffuse±50 Wm-2)NREL SERI_QC for Atmospheric Radiation Measurement (ARM) Program  Physical sense (Max & Min values for Kn,Kt,Kd  Crossing components (Kt=Kn+Kd ± 0.03)  Other one, two or three-component tests 4th Meeting IEA SHC Task 36 Hamburg 23-25 Oct 2007
  4. 4. Other proceduresR. Claywell, T. Muneer, M. Asif, 2005. Journal of Solar EnergyEngineering kd-kt scatter envelope kd ∈[< kd > −2σ k , < kd > +2σ k ] 4th Meeting IEA SHC Task 36 Hamburg 23-25 Oct 2007
  5. 5. Frequent errors found in some databases Error in time reference registered. This error affects to the clearness index estimation. Error in beam measurements close to sunset/sunrises. 4th Meeting IEA SHC Task 36 Hamburg 23-25 Oct 2007
  6. 6. Error in time reference1. Error detection: Kt analysis. 4th Meeting IEA SHC Task 36 Hamburg 23-25 Oct 2007
  7. 7. Error in time reference2. Proposed correction: THEORY 1. Depending on the time frequency, data interpolation in intervals lower than 10 minutes. 2. Centering data around midday. 3. Trying different displacements: (±1 hour) 4. Kt analysis: (from wsr+1 to wss-1)=> n iterations. 5. In each iteration, Maxi(Kt) of the whole day is selected. 6. True displacement = position (i), where min(Maxi(Kt)). 4th Meeting IEA SHC Task 36 Hamburg 23-25 Oct 2007
  8. 8. Error in time reference2. Proposed correction: PRACTICCE:  Start : centered position: green points (hourly); yellow (interpolated)  Kt matrix analyzed (red big square)  Position selected: position (i), where min(Maxi(Kt)). hourly data selected: blue points. 4th Meeting IEA SHC Task 36 Hamburg 23-25 Oct 2007
  9. 9. Error in time reference3. Results: 4th Meeting IEA SHC Task 36 Hamburg 23-25 Oct 2007
  10. 10. Error in beam radiation near sunrise and sunset4th Meeting IEA SHC Task 36 Hamburg 23-25 Oct 2007
  11. 11. Conclusion Should Task 36 propose a general procedure for quality of ground measurements? In that case, which criteria should be included? Should this procedure be included in a guide of solar radiation data (MESoR)? 4th Meeting IEA SHC Task 36 Hamburg 23-25 Oct 2007

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