Recent and Planned Improvements to the System Advisor Model

1. Recent and Planned Improvements
to the System Advisor Model
Nate Blair
Team: Aron Dobos, Janine Freeman, Paul
Gilman, Nick DiOrio, Steve Janzou
October 2016

2. 2
System Advisor Model
These calculations are done
using detailed performance
models, a detailed cash flow
finance model, and a library of
reasonable default values for
each technology and target
market.
Technologies SAM can model:
- Photovoltaics
- Concentrating Solar Power
(Trough, Tower, Linear Fresnel,
Dish Stirling)
- Geothermal (power)
- Solar Water Heating
- Wind (Small + Utility scale)
- Biomass Power
The System Advisor Model (SAM) is a free user-friendly platform that calculates a
renewable energy system’s (sub-)hourly energy output, and calculates detailed
financial metrics for a renewable energy project over the life of the project.
Weather
Data
System
Specs
Energy
Production Cost Data
Financing
Options
Utility Rates
&
Incentives
+ » + + + »
Annual, Monthly,
and Hourly Output,
LCOE, NPV,
Payback, Revenue,
Capacity Factor
Aron Dobos

3. 3
Irradiance
Transposition using Isotropic, HDKR, or Perez
Measured plane of array (POA) input
Shading
Irregular obstruction shading from 3D scene
Self-shading for regularly spaced rows
External input from SunEye, Solar Pathfinder
Non-linear shading algorithm
Snow cover loss model
Module
Simple efficiency model
Single diode model (CEC database or datasheet)
Extended single diode model (for IEC-61853 tests)
Sandia PV Array Performance Model
Inverter
Sandia/CEC grid-tied inverter model (with database)
Datasheet part-load efficiency curve
System
Sizing wizard or electrical layout
Multiple subarrays
Fixed, 1 axis, backtracking, azimuth axis, 2 axis
Battery storage
Degradation
Extrapolated single year
Lifetime simulation of all years
Simulation
1 minute to 1 hour time steps
Detailed photovoltaic model
Dobos, A.; MacAlpine, S. Procedure for Applying IEC-61853 Test
Data to a Single Diode Model. Proc. IEEE 40th PVSC Conf. Denver
CO, June, 2014

4. 4
Ability to calculate losses due to snow cover

5. 5
• Techno-economic model for
residential, commercial, and
third-party ownership
systems
o Lead acid & lithium ion
battery chemistries
o System lifetime analysis
including battery
replacement costs
o Models for terminal
voltage, capacity,
temperature
o Multiple dispatch controllers
available
PV with Battery Model Overview

6. 6
Battery Dispatch Visualization
Peak shaving for demand charge reduction Manual dispatch for energy arbitrage

7. 7
Parametric battery sizing results
• NPV maximized for no PV
system, battery bank
capacity of 70 kWh
• Illustrates simulation-based
method to approximate
‘optimal’ sizing.

8. 8
Interactive drag-and-drop 3D scene editing
for positioning PV arrays and obstructions
Predefined boxes, cylinders, trees, roof panes
Calculates linear beam irradiance shading
losses and sky diffuse view factor loss
Imports 2D mapping underlays from online
maps
Outputs are diurnal or hourly/subhourly time
series linear shade loss percentages
You can group PV surfaces into subarrays
and specify parallel strings
Scripting to automate panel layout and
import/export geometry data
3D shading calculator

9. 9
More efficient way to estimate nonlinear impact of partial
shading than a bottoms-up electrical cell-by-cell model.
Nonlinear loss model for parallel strings
Bottoms-up
electrical model
At each time step…
Precalculate once.
Lookup table
Number of parallel strings
Shade fraction on each string
Fraction of diffuse irradiance
DC power loss due to shade (%)
Nominal DC kW
Shaded DC kW
~
MacAlpine, S.; Deline, C.; Simplified Method for Modeling the Impact
of Arbitrary Partial Shading Conditions on PV Array Performance.
Proc. IEEE 41th PVSC Conf. New Orleans, LA, June, 2015

10. 10
Nonlinear shade model results
Electrical Linear Nonlinear
3 kW, two trees 21.1 % 13.8 % 20.4 %
18 kW, row shading 15.8 % 14.5 % 15.0 %
Two systems in Denver, CO. (% loss due to shading)
SAM
Linear
SAM
Nonlinear
PVsyst SunEye
NREL garage +4.1 % -0.1 % -1.5 % ---
Denver home +6.6 % -1.3 % +0.2 % -2.2 %
Boulder home +20.2 % -1.1 % -3.1 % ---
Comparison to measured data (% greater than measured)
Reference
MacAlpine, S.; Deline, C.; Dobos, A.; Measured and Estimated Performance of a Fleet of Shaded Photovoltaic Systems
with String- and Module-level Inverters. Progress in Photovoltaics, forthcoming, 2017.
Notes
• Models are quite sensitive to accurate placement of trees and obstructions in 3D.
• Lookup table method is extremely fast, but limited to 8 parallel strings.
• Efforts for additional validation are ongoing.

11. 11
Scripting
Built-in scripting language to automate
simulations and post-process results
Macros
Ready-to-run scripts that are packaged
into SAM for nonprogrammers
Software development kit
- Develop your own software that calls
the SAM models
- Developing mobile platform versions
(iOS and Android)
Public Source Code
Working to publicly release source code
for PV and battery models such that
users can modify and recompile the
SAM Simulation Core
Extending SAM
SAM Simulation Core (SSC)
inputs outputs
C/C++ MATLABPython .NET Java
External applications
PV CSP SWH Financials
SAMprojectfileCode
SDK

12. 12
New complex utility rate model options
Additional net metering options have been added and implemented to help users
understand the impact of different scenarios currently implemented in several states.
New data browser categorizes and consolidates results.
Linkage with OpenEI rate database improved and expanded for some international rates.
Note: This complexity now being used for projects in support of Mexico DG efforts
http://www.openei.org

13. 13
Current Version:
• Direct connection to the new NREL National
Solar Radiation Database (NSRDB) including
much of North and South America
• Lifetime PV+battery simulations
• Line-by-line debugging in scripting
• Parallel processing for batch simulations
• Simplified LCOE calculator w/ fixed charge rate
• 1600+ bundled weather in simple CSV format
• Support for high-DPI screens and Linux x64
Coming up…
• Direct link to India region weather data
• Inverters with multiple MPPT inputs
• Scripting enabled for 3D shading to program
trackers w/ arbitrary geometry
• Utility scale battery storage systems
• 3D shading model comparison study
• Source code for PV and Battery models
New features
30 years @ 1 min steps
http://nsrdb.nrel.gov
DC AC
Linux x64

14. 14
• Mexico: SAM is being used to help
evaluate the cost-effectiveness
(payback time) for regulators for
DG PV.
• India: Developing templates for PV
in India including minor
adjustments to financial models
and easier incorporation of India
resource data
• China: Developing a China
language version of the SAM
manual (PV and CSP being of large
interest)
• General: Accessing and
distributing free resource data as
available and better links to other
data providers (NSRDB in
particular)
Growing International Presence in Developing Countries

15. Our team
Aron Dobos Project lead, software architecture, PV modeling
Nate Blair Emeritus lead, financials, costs, international
Janine Freeman Photovoltaic and wind models
Nick DiOrio Battery storage models
Steve Janzou Programming, utility rate structures (subcontractor)
Paul Gilman User support and documentation (subcontractor)
Ty Neises Concentrating solar power models
Mike Wagner Concentrating solar power models
http://sam.nrel.gov