Solar Site Evaluation Tips and Techniques Peter Hoberg VP Sales and Marketing Solmetric Corporation
Shade Measurement Topics • Site analysis considerations – Why measure shade? – Terminology – Shade measurement strategies
• Using the SunEye – Live demo – Common problems and solutions – State rebate requirements
• Resources, Questions and Answers
Solmetric Corporation • • • •
Founded in 2005 20 employees Headquarters in Sebastopol, CA Mission: to improve the effectiveness of solar systems and those who install them by providing high quality, easy-to-use, accurate tools with embedded technical know-how.
Solmetric Solutions
Solmetric Installations with Grid Alternatives
Why measure shade?
• • • •
Choose optimum location for panels Identify issues early in the process Ensure sufficient energy production Ensure optimum state rebate
Note: Shading can have disproportionate impact on energy production
PV String Simulation Model Sun position, panel tilt/Azimuth Irradiance, shade, temperature, wind speed
Module bypass diode configuration Module parameters Inverter parameters String wiring AC KWh
What’s Happening Electrically? I-V and P-V curves Max Power I-V
Isc
Output Power Current
Imp Max Power Point
P-V
Voltage
Vmp
Shade, String Current, and Bypass Diodes • Partial shading reduces current flow in module and string • Typical module has 24 cells in 3 sub-strings each with a bypass diode • When bypass diode activated, string current restored, but voltage drops
Multiple Peaks Challenging for the Inverter Impact of Shading on the P-V Curve Normal P-V curve
Inverter’s Max Power Point Tracker (MPPT) stays on peak, but which one?
Power
Shaded P-V curve (multipeaks--typical of mismatch conditions such as partial shade) Voltage
Shading: a little bit goes a long way 100%
73%
Business Card covering half of one cell
Sun path interaction
Max access
Reduced access
No access
Sun Path
Sun Trajectories (“Sunpaths”)
Noon
Sunrise
Sunset
Annual sun path example
Hemisphere view (Skyline)
Irradiance Incident solar radiation (power) per unit area in kW/m2
Approximately 1 kW/m2 at the earth’s surface.
Insolation – Solar Energy over Time per unit Area in kWh/m2
1 kW/m2 of irradiance for 6 hours = 1 kW/m2 x 6 hr = 6 kWh/m2 of insolation. 6 kWh/m2 of insolation on a 2 sq-m surface = 6 kWh/m2 * 2 m2 = 12 kWh of energy received by the surface.
San Diego insolation
Solmetric Compound Angle Tool
Solar Resource Terms • Insolation. Incident Solar Radiation, kWh/m2 • Solar Access. Insolation compared to no shading, in field of view of the panel. • Tilt and Orientation Factor (TOF). TOF is the solar insolation at the actual tilt and orientation divided by the insolation at the optimum tilt and orientation, expressed in percent. • Total Solar Resource Fraction (TSRF). TSRF is the ratio of insolation available accounting for both shading and TOF, compared to the total insolation available at a given location at the optimum tilt and orientation and with no shading. TSRF is also expressed in percent, according to the following equation: TSRF = Solar Access * TOF.
Solar Resource Terms Optimum Annual Insolation
TOF Solar Access Loss due to shading
TSRF
Loss due to suboptimal tilt/azimuth
Solar Resource Example Optimum Annual Insolation
TOF Solar Access Loss due to shading
Good Solar Access means little shade, but not necessarily the best solar production.
TSRF
Loss due to suboptimal tilt/azimuth
Obstruction Geometry
H/D = TAN (θr)
θr = TAN-1( (H/D)
• D/H as high as possible • D/H > 2 is California Minimal Shading ~26 degrees • D/H > 3+ is “shade free 9-3”
Sun path interaction
H
Solar Array D h
θr = TAN-1((H-h)/D) For “shade free from 9 to 3”, use Minimum θr = December 21 sun elevation at 9am or 3pm.
Shade measurement strategies
• Take multiple point readings – Spacing between readings
• Look for worst case – Array corners – Points closest to obstructions
• Average solar access readings • Obstruction elevation angles
Note: Be sure you meet the requirements of your state program and rebate calculators
Using the Solmetric SunEyeTM
Copyright Solmetric Corporation, 2008
Introducing the Solmetric SunEyeTM 210 • What’s New? – – – – – – – – –
Easy one-handed operation Brighter, higher Res. Display (4x) Electronic compass & inclinometer Dynamic Site-survey mode Large capacity battery Integrated stylus holder Integrated GPS option Impact resistant molded case 2 year warranty
Comparing to the original SunEye • What’s the same? – – – –
Easy to use and navigate user interface Powerful shade analysis software On-board editing tools for “What-if” Results viewable right on the SunEye • Solar Acess, Solar Resource • Sunpaths, Monthly Solar Access • Obstruction Elevation Angles – Desktop Companion Software included ( Proven after shipping thousands of Model 110 SunEyes )
Steps for measuring solar access Bubble Level
1. Point south* 2. Hold Level 3. Press the button
* Point south in the northern hemisphere; point north in the southern hemisphere.
Compass
Steps for measuring solar access Electronic Bubble Level
1. Point south* 2. Hold Level 3. Press the button
* Point south in the northern hemisphere; point north in the southern hemisphere.
Electronic Compass
Steps for measuring solar access Electronic Bubble Level
1. Point south* 2. Hold Level 3. Press the button
* north in the southern hemisphere
Electronic Compass
Built-in Inclinometer •
Measure Tilt and Azimuth 1. Set SunEye on plane of solar array. 2. Point arrow towards array heading. 3. Read tilt and azimuth from display. 4. Enter into panel orientation fields.
Site-Survey Mode •
Find optimum module placement 1. Find prospective solar site. 2. Survey potential module locations by: 1. Pressing Quick-launch survey button. 2. Scan area while observing obstructions entering the sunpath.
SunEye’s Key Benefits • Accuracy and repeatability – Calibrated fisheye lens – Multiple users, different situations, same results
• Speed and convenience – Full Sky Preview mode – One shot for the entire skyline – Point and shoot capability
• Data transfer – Solmetric PV Designer – Other Programs
Live indoor measurement example (for academic purposes) • “Sky Simulator” facilitates indoor use (demos and training) • Small tree toward the east; larger tree toward the west Example azimuth=150º; tilt=20º
SunEye position Always: Level, toward magnetic South
Dealing with Shade • Optimize Shade-Free production – Avoid shade whenever possible – Find the best location for the desired season/time-of-day
• Tree removal – Reduce shade – Minimize debris
• Module Level MPP – Incorporate new technologies that mitigate shade impact • Micro-inverters • Power Optimizers
The SolarMagic™ Power Optimizer
SolarMagic™ Input • High speed MPPT algorithms maximize panel energy harvest • Wide-input range accommodates almost all panel types
SolarMagic™ Output • Automatically scales output current and voltage to optimize power of the entire
string. • Wide output range maximizes flexibility
Slide courtesy of:
Predicting energy production • Solar Calculators: – PVWatts by NREL – Vendor web sites – State rebate calculators • CSI Incentive Calculator (EPBB Calculator) • NSHP Calculator – Commercial software products • PV*SOL, PV-Syst, Laplace, Maui • On-grid, CPF Tools, Clean Power Estimator • Etc.
Solmetric PV Designer
SunEye GPS Add-On • GPS option integrated into 210 • Detects latitude/longitude for session location and automatic sunpath generation • Records location of each skyline data set collected • Reports include file for Google Earth™
SunEye GPS output to Google Earth™
Data transfer to computer via USB • SunEye stores more than 100 Skylines in memory • Transfer data to PC for further analysis • View and edit data in same way as on hand-held • Create reports and export files to design tools
Solar Access and Shade Report Client Information
• All session data is combined into a single hypertext document • Converts to MS-Word™ • View, Email, or print
Installer business information/logo
Access raw data files
Day
• Import data files into design software – Excel spread sheet, OnGrid, PVOptimize, PV*SOL, T*SOL, PVSyst, QuickQuotes, CPF Tools
1 2 3 4 5 6 7 8
Month Jan Feb Mar 54.17 54.99 67.64 54.17 54.99 67.64 54.17 54.99 67.64 54.17 54.99 67.64 56.63 54.66 67.77 56.63 54.66 67.77 56.63 54.66 67.77 56.63 54.66 67.77
Updated Software and Accessories • New software updates available from: www.solmetric.com – Includes handheld and PC updates – Set for auto-update
Resources • User’s Guide accessible via desktop software – Help>Solmetric SunEye User’s Guide…
• Knowledge base at: – http://www.solmetric.com/knowledgebase.html
• Technical Support – 1-877-263-5026, opt 2 –
[email protected]
Dec-Jan issue: “Solar Site Evaluation” www.solarprofessional.com phoberg
Questions?
Solmetric Corporation www.solmetric.com 1-877-263-5026
