2014 PV Performance Modeling Workshop: Isis Power Plant Energy Simulation Tool, Bodo Littmann, First Solar


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2014 PV Performance Modeling Workshop: Isis Power Plant Energy Simulation Tool, Bodo Littmann, First Solar

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2014 PV Performance Modeling Workshop: Isis Power Plant Energy Simulation Tool, Bodo Littmann, First Solar

  1. 1. © Copyright 2013, First Solar, Inc.
  2. 2. 2 ©Copyright2013,FirstSolar,Inc. Isis-2: Energy Model Integrated with Business Systems Parametric Generator Cost Model Isis Energy Model Financial Model Optimized Plant Design & Layout Sales Tool Fleet Performance Database Expected Performance Reporting Energy Prediction Map
  3. 3. 3 ©Copyright2013,FirstSolar,Inc. Key Differentiating Features Spectral Shift Native implementation – traditionally backed into with other gain/loss factors Soiling Ramped model with rain-triggered and manually-triggered cleanings Lifetime analysis DC-side degradation in voltage & current Multi-year performance estimates/performance analysis Module temperature Transient model taking into account all heat fluxes Inverter Redefined as state engine with zones User-selectable maximum power setpoint with temperature & elevation derate Efficiency curves at many voltages Plant architecture Block-by-block breakdown with independent module characteristics, DC:AC loading factors, etc. with staggered installation & energization schedule for key financial analysis Time Scale Sub-hourly modeling to better avoid modeling artifacts due to weather averaging (inverter clipping) Improved power plant analysis Application Multi-user web application with shared components library Secure database of simulations results Integrated with other business systems
  4. 4. 4 ©Copyright2013,FirstSolar,Inc. Simulation
  5. 5. 5 ©Copyright2013,FirstSolar,Inc. Representation of a Power Plant Preliminary? As-Built? Contractual? Re-Usable Components
  6. 6. 6 ©Copyright2013,FirstSolar,Inc. Soiling Model with Ramp Rates & Cleaning Events Direct Monitoring of Energy Lost due to Soiling on First Solar Modules in California, 38th PVCS
  7. 7. 7 ©Copyright2013,FirstSolar,Inc. CdTe Spectral Shift Changes in Cadmium Telluride Photovoltaic System Performance due to Spectrum, 38th PVSC H2O Absorption Bands Monthly and hourly calculation of the CdTe spectral response using precipitable water or relative humidity
  8. 8. 8 ©Copyright2013,FirstSolar,Inc. Shading & Incidence Angle Modifier Losses Increased Energy Production of First Solar Horizontal Single-Axis Tracking PV Systems without Backtracking, 39th PVSC 0 100 200 300 400 500 ACPower(kW) Median System System C System D 100 200 300 400 500 ACPower(kW) Median System System C System D 0 100 200 300 400 500 ACPower(kW) Median System System C System D
  9. 9. 9 ©Copyright2013,FirstSolar,Inc. Dynamic Thermal Model A Time Dependent Model for Utility Scale PV Module Temperature, 40th PVCS 20 30 40 50 60 70 ModuleTemperature,Celsius Hourly Avg. Module Cell Temperatures; Desert Southwest during the Summer Measured PVsyst Default Model Updated PVsyst Model FSLR Model Reduces irradiance-weighted Tmod error at hot climate sites from 3.2 °C (RMSE) to 1.5-2.0 °C, overall RMSE reduction by 51%, MBE by 30% Measured Default Static Model Updated Static Model Dynamic Model
  10. 10. 10 ©Copyright2013,FirstSolar,Inc. Non-Linear Temperature Coefficient 𝑖 = 𝐼ph − 𝐼0 𝑒 𝑉d 𝑛cs ∙𝛾∙𝑉th − 1 − 𝑉d 𝑅sh − 𝐼ph ∙ 𝑏 1 𝑛cs 𝑉bi − 𝑉𝑑 𝑉d = 𝑣 + 𝑖 ∙ 𝑅s
  11. 11. 11 ©Copyright2013,FirstSolar,Inc. Array – Inverter Interaction Once module temperature is computed, the 1-diode coefficients are temperature corrected, and the array MPP is solved However, the inverter behavior is dynamic as well: • Efficiency is a function of V & P • Max capacity is a function of temperature and elevation What inverter “zone” are we operating at?
  12. 12. 12 ©Copyright2013,FirstSolar,Inc. Parametric Analysis for Power Plant Design Optimization
  13. 13. 13 ©Copyright2013,FirstSolar,Inc. Benchmarking Goals To quantify system-level prediction accuracy by using a well- understood subset of extremely high-confidence data sets • Deep look at performance to prediction • Error analysis of energy predictionReporting • Feedback for energy model development by re- benchmarking • Test-bed for advanced analytic methods Continuous Improvement • Demonstrate that Isis will hit the P50 for an ensemble of plant performance analyses in different climates & configurations Acceptance
  14. 14. 14 ©Copyright2013,FirstSolar,Inc. Monitoring Points Evaluating accuracy and error step-by-step through the model with a final goal of understanding WHY prediction error occurs at the energy meter Energy Meter AC Power Inverter Efficiency DC Power DC Voltage DC Current Module Surface Temperature Plane of Array Irradiance Gigawattsbytes of powerdata reduced into meaningful, easy-to- interpret results
  15. 15. 15 ©Copyright2013,FirstSolar,Inc. -5 -4 -3 -2 -1 0 1 2 3 4 5 Model Error (%) Average Error = 0.43% StDev Error = 2.53% Span Error = 7.75% Prediction Accuracy at the Energy Meter Isis-2 overpredicted energy by 0.43% on average with a standard deviation of 2.53% -5 -4 -3 -2 -1 0 1 2 3 4 5 0 1 2 3 4 5 Energy Meter Model Error (%) NumberofSystems Average Error = 0.06% StDev Error = 1.96% Span Error = 6.72% Introduction of advanced lifetime model of voltage and current reduced the error to 0.06% 10 sites | > 375 MW of PV modules | 15 system-years 3 2 1 No.Systems
  16. 16. 16 ©Copyright2013,FirstSolar,Inc. Look for First Solar at the 40th IEEE PVSC in Denver! • “Evaluation of GHI to POA Models at Locations across the United States” — Joint effort with SNL to quantify accuracy of irradiance decomposition/transposition models • “A Time Dependent Model for Utility Scale PV Module Temperature” — Updated module temperature module reduces RMSE by 51% and MBE by 30% • “Measuring Soiling Losses at Utility-scale PV Power Plants” — Continuing collaboration with Atonometrics to measure soiling losses • “Performance Characterization of Cadmium Telluride Modules Validated by Utility Scale and Test Systems” • “Self-Reported Field Efficiency of Utility-Scale Inverters” • “Spectral Mismatch Considerations in Multi-irradiance Characterization of PV Modules” • “Evaluation of a CdTe Spectrally Matched c-Si PV Reference Cell for Outdoor Applications” • “Regional Atmosphere-Solar PV Interactions”