Distributed Renewable Energy Operating Impacts and Valuation Study

APPENDIX F — PHOTOVOLTAIC SYSTEM MODELING
F.1 Model Selection
A number of photovoltaic performance models were considered for this study. Most of the
models provide comparable results, as shown in the following table. This evaluation was
performed by Sandia National Laboratories, and compares simulation results from each model,
along with actual data from a photovoltaic system in Phoenix.
Model
Table F-1
Annual
Energy
Production
(kWhac)
Final Annual
Yield
(kWhac/kWdc)
PV Watts 3683 1615
PV Watts Ver2 3522 1545
Maui (PV Design Pro) 4140 1816
PV Mod 3311 1562
RETScreen 3834 1682
SAM (Solar Advisor Model) 3609 1583
Measured Data
(4-year average) 3529 1548
Source: Sandia National Laboratories, “Larry More and Chris
Cameron, DOE Solar Energy Technologies Program presentation,
April 17-19, 2007, Denver, CO
The Solar Advisor Model (SAM) was selected for this study. Following are the key factors used
in making this decision:
• The model provides good correlation with actual PV production
• It uses state-of-the-art modeling of the PV modules (an I-V curve based on actual module
data) and inverters (an efficiency versus load curve based on actual inverter performance)
• SAM produces hourly data strips of PV system power/energy production
• APS uses this model for solar thermal studies
• It is free from National Renewable Energy Laboratory (NREL)
SAM Version 2.0 was released during the APS study, and this version was used for all final
results.
004137/02-01766-01000
Arizona Public Service | Distributed Renewable Energy Operating Impacts & Valuation Study