SAM Photovoltaic Model Technical Reference Update

1 NREL is a national laboratory of the Department of Energy Office of Energy Efficiency & Renewable Energy Operated by the Alliance for Sustainable Energy, LLC This report is available at no cost from the National Renewable Energy Laboratory (NREL) at Contract No. DE-AC36-08GO28308 SAM Photovoltaic Model Technical Reference Update Paul Gilman, Aron Dobos, Nicholas DiOrio, Janine Freeman, Steven Janzou, and David Ryberg National Renewable Energy Laboratory Technical Report NREL/TP-6A20-67399 March 2018 NREL is a national laboratory of the Department of Energy Office of Energy Efficiency & Renewable Energy Operated by the Alliance for Sustainable Energy, LLC This report is available at no cost from the National Renewable Energy Laboratory (NREL) at Contract No.

2 DE-AC36-08GO28308 National Renewable Energy Laboratory 15013 Denver West Parkway Golden, CO 80401 303-275-3000 SAM Photovoltaic Model Technical Reference Update Paul Gilman, Aron Dobos, Nicholas DiOrio, Janine Freeman, Steven Janzou, and David Ryberg National Renewable Energy Laboratory Prepared under Task No. Technical Report NREL/TP-6A20-67399 March 2018 NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights.

3 Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. This report is available at no cost from the National Renewable Energy Laboratory (NREL) at Available electronically at SciTech Connect Available for a processing fee to Department of Energy and its contractors, in paper, from: Department of Energy Office of Scientific and Technical Information Box 62 Oak Ridge, TN 37831-0062 OSTI Phone: Fax: Email: Available for sale to the public, in paper, from: Department of Commerce National Technical Information Service 5301 Shawnee Road Alexandria , VA 22312 NTIS Phone: or Fax: Email: Cover Photos by Dennis Schroeder: (left to right) NREL 26173, NREL 18302, NREL 19758, NREL 29642, NREL prints on paper that contains recycled content.

4 Executive SummaryThis manual is describes the Photovoltaic performance Model in the system advisor Model (SAM) Version (SSC 178). It is an Update to Gilman (2015), which describes the Photovoltaic Model in SAM Version (SSC 41).The Department of Energy s National Renewable Energy Laboratory maintains and distributes SAM, which isavailable as a free download is a techno-economic feasibility Model for renewable energy projects. It is designed for a range of differentusers, including project developers, system designers, policy makers, financial planners, and academic s Photovoltaic performance Model is available both as part of the SAM desktop application, and in the SAMsoftware development kit (SDK). This manual is intended for people who want to understand SAM s photovoltaicmodel, or for people who are using the SDK to develop their own runs on Windows 32- and 64-bit, and OS X 64-bit, and Linux 64-bit operating systems, and is a user interfacethat performs the following functions: Organizes and displays the performance and financial Model inputs in a user-friendly interface.

5 Manages tasks associated with running Model simulations. Provides options for advanced" simulations that involve multiple simulation runs for parametric and sensitiv-ity studies. Stores arrays of Model results. Calculates secondary results such as monthly and annual totals, capacity factor, system performance factor,and system losses. Displays tables and graphs of results. Allows for exporting data in different formats including CSV, graph images, Microsoft Excel, and PDF SAM SDK is a package containing the SAM Simulation Core (SSC) libraries and a set of software developmenttools that allow Model developers to create their own interfaces to the simulation modules as either web or report is available at no cost from the National Renewable Energy Laboratory at of Contents1 Nomenclature.

6 22 Photovoltaic Performance Model Overview.. Algorithm .. and Solar Resource Libraries .. Sizing ..73 Irradiance and Weather Data.. Period and Resolution .. Observations ..104 Sun Position.. Time .. Angles .. and Sunset Hours .. Flag .. Radiation .. Solar Time and Eccentricity Correction Factor ..175 Surface Angles.. of Incidence .. , Azimuth and Two-axis Tracking .. Tracking .. Angle for One-axis Trackers .. for One-axis Trackers ..216 POA (Incident) Irradiance.. POA Calculations .. (Incident) Beam Irradiance .. (Incident) Sky Diffuse Irradiance .. Model .. Model .. 1990 Model .. (Incident) Ground-reflected Irradiance ..267 Effective POA Irradiance.. POA Irradiance.

7 Shading .. External Shading and Shading Database Lookup .. Shading .. Irradiance ..301 This report is available at no cost from the National Renewable Energy Laboratory 3D Shade Calculator.. Irradiance Loss .. Irradiance Loss ..339 Self Shading Algorithm.. Shading Assumptions .. Option: Diffuse POA Irradiance Reduction .. Dimensions .. Option: Beam POA Irradiance Reduction .. Option: DC Loss Factor .. tracking: Shaded Fraction .. Position Unit Vectors .. Vertices .. Panel .. Fraction ..4410 Module DC Output.. Module Models .. Cell Temperature Models .. Sandia Module Model .. CEC Module Model .. Simple Efficiency Module Model .. NOCT Cell Temperature Model .. Heat Transfer Cell Temperature Model .

8 Sandia Cell Temperature Model .. IEC 61853 Single Diode Module Model ..5811 Array DC Output.. Voltage and Current .. Power Output .. DC Electrical Losses .. DC Snow Losses .. Maximum Power Point Tracking .. Subarray Mismatch Losses ..6712 Inverter AC Output.. Inverter Models .. Sandia Inverter Model .. Inverter Part Load Curve Model .. Inverter Clipping Losses and Voltage Checks ..7213 Degradation.. AC Degradation: PV Simulation Over One Year .. DC and AC Degradation: PV Simulation Over Analysis Period ..7414 Battery Storage.. Battery with no Photovoltaic system .. Battery Model Inputs and Outputs .. Dispatch Modes ..7615 system AC Output.. AC Losses ..812 This report is available at no cost from the National Renewable Energy Laboratory Curtailment and Availability Losses.

9 Power Generated by system ..82 References..83 List of FiguresFigure Performance Model Simplified Block Diagram ..5 Figure Angles ..13 Figure Angles ..19 Figure scene editor for shading calculations ..33 Figure Dimensions for Portrait Module Orientation ..35 Figure View of Two Rows with Self-shading Mask Angle Variables ..38 Figure of Two-slab Module Cover Reflection Loss Model ..61 Figure Comparison of Angular Response of Two-slab Model to Single-slab Model ..62 Figure of Snow Cover on a Photovoltaic Array ..66 Figure Block Diagram for AC-Connected Battery ..75 Figure Block Diagram for DC-Connected Battery ..76 List of TablesTable Models in SAM s Photovoltaic Performance Model .

10 4 Table Data ..9 Table Position Variable Definitions ..13 Table Angle Variable Definitions ..19 Table Irradiance Variable Definitions ..23 Table Sky Diffuse Irradiance Model Coefficients ..26 Table POA Irradiance Variable Definitions ..28 Table Shading Variable Definitions ..36 Table Model Variable Definitions ..47 Table Models in SSC ..48 Table Temperature Models ..48 Table Module Model Inputs ..49 Table Module Model Inputs ..513 This report is available at no cost from the National Renewable Energy Laboratory Efficiency Module Model Inputs ..54 Table Cell Temperature Model Variable Definitions ..55 Table Transfer Cell Temperature Model Variable Definitions ..56 Table Cell Temperature Model Variable Definitions.