3. Topics for today:
Online tools for site assessment
Performing "ball-park estimates”- the risks
Grid Direct VS. battery-based systems
Site Analysis: system layout and installation-
component location, NEC requirements, & effects on
performance and cost
Equipment selection- component matching and utility
interconnection requirements
4. Resource will be provided:
Array string calculations: effects of temperature, inverter
matching
Solar resource assessment: Azimuth, magnetic declination
Array sizing: by area, budget, energy demand
Online resources for solar resource assessment (Peak Sun
Hours)
Determining useable roof area and attachment points
required
Trigonometry : tilt angles, shading obstructions
5. #SolarMOOC Resources
Subject Matter Experts
#SolarMOOC Academy dropdown menu option is
Subject Matter Experts
ARCHIVE: #SolarMOOC Academy dropdown menu
Most Recent Lessons2012 / 2013 Archive
6. Online tools for site assessment
Google Earth - ruler and Azimuth tool
Google Maps -
“Classic maps” - ruler for rough estimate on sizing under
“Maps Labs”
LIMITATIONS of tools and virtual assessment
Trees grow
Roof - hard to determine age / structural integrity
Can not see obstructions - vents/pipes
Can not achieve true shading analysis
7. Online tools for site assessment
NREL PV Watts Calculator - multiple versions
Solar resource
Performance estimate
ROI
Google it: ”PV WATTS”
Other professional proposal software will calculate more
accurate costs and ROI specific to the customer
Ex. Rebates from utility & financing (effects ROI)
Ex. Of programs- Energy Periscope, OnGrid Solar
8. Google Earth
• Measure lines, save for later viewing and sharing
• Measure azimuth degrees instantly, declination
preconfigured
9. Google- ruler tool and street view
• Measurements
• Azimuths
• Roof pitch
• Building height
10. PVWATTS from NREL
FREE online tool
NREL's PVWatts calculator determines the energy
production and cost savings of grid-connected PV
Systems.
11. Select your location...
& click "send to PVWatts".
Tweek a few things, click to calculate, and viola!
13. Site Analysis:
Solar resource and shading
RESOURCES
NREL - Data tables (PSH)
Trig for shading analysis-
Go to solpowerpeople.com
Search for “trigonometry”:
14. Site Analysis:
Solar resource and shading
Resources:
Azimuth - production, shading
Altitude - production, shading
Solar window - year round production assessment
Magnetic declination - accurate production and shading
Site assessment
fundamentals
15. Performing "ball-park estimates"-
the risks
Online calculated area is not an accurate
calculation of system size potential
Must visit site-
Obstructions
Shade
Mechanical considerations- roof trusses
Area efficiency not same as module efficiency
Power (kW), Area (m2), Efficiency
DC vs. AC
16. Performing "ball-park estimates"-
the risks
Costs may change depending on site specific
conditions
Roof mount - type and age
Pole or Ground mount - soil- rock?
Roof tilt - not easy to determine online
Be sure customer is aware of utility charges when
considering expected bills
Return on Investment (ROI)
Utility buyback policies
17. Performing "ball-park estimates"-
the risks
Resources:
#SolarMOOC Subject Matter Experts page:
Determine required attachments
Determine # of modules that will fit in area
Area, Budget and Energy demand sizing estimates
Ball park
estimates
18. Grid Direct VS. battery-based systems
Grid direct- requires anti islanding
DOES NOT function when grid is down
Net-metering/ dual metering potential
Grid offers “free storage”
More efficient than batteries
Inverter selection
19. Battery based / Battery back-up
Stand Alone - will function when grid is down if storage exists
Grid tied with Battery Back-up- Critical load panel will function
when grid is down-
limited capacity depending on battery bank size (autonomy)
More reliable = more storage = more expensive
Inverter selection, additional components
Conductors, OCPDs, charge controller, batteries, critical load
panel, extra inverter if AC Coupled (battery backup)
NEC 690 Part VIII - Storage Batteries
NEC 480 - Storage Batteries
Grid Direct VS. battery-based systems
21. Site Assessment: Layout & Install
Component location
NEC requirements
Effects on performance and cost
2011 NEC
22. Component Location
& NEC Requirements
Installed in neat and workmanlike manner - NEC
110.12
Installed as listed or labeled - NEC 110.3(B)
Spaces required - NEC 110.26
Depends on location, voltage, etc.
23. Component Location
MODULES:
IFC regulations - becoming a standard
Not mandated in 2012 NEC
Look for it in 2014
Attachments - framing considerations (roof)
Shading - again and again
24. Inverter Location
Inverter - Distance from load center
Locate inverter near installation to avoid voltage drop
Potential shut down (design for inverter voltage range)
Prevent extra installation costs
Power loss, reduced ROI
Conductors
Conduit runs
Expansion fittings
Design time
Labor time
Chosen to match electrical connection
25. Component functionality/treatment:
Out of sun
Consider temperature
Requirements for equipment installation
NEC 110.13 - mounting and cooling
NEC 110.12 - neat and workmanlike
NEC 110.26 - working spaces
NEC 110.27 - live parts
Equipment manual - NEC 110.3(B)
Installed as listed and labeled
Inverter Location
26. Component Selection / Location
Resources
Resources:
Voltage drop - #SolarMOOC with Raymer and Stovall
String sizing: Jeff Gilbert #SolarMOOC
Verifying System Design- voltage considerations, inverter
matching, string sizing
27. Component Selection / Location
DC rated- NEC 690.4(D)
Disconnects, OCPDs
Disconnecting means- NEC 690 Part III
DC disconnect must be in an accessible location
AHJ may require additional external DC disconnect even if
integrated into Inverter
AC modules/microinverters: NEC 690.6
Batteries: NEC Article 480 & Article 690 Part VIII
NEC 480.9: Battery locations (NEC 110)
NEC 480.8: Racks and trays
NEC 690.71(B): dwellings = <50V Nominal
NEC 690.71(D): Nonconductive racks
28. Effects on Performance
and Cost
Performance
SHADE!- needs to be taken seriously- a tiny amount could kill
production, and ROI for customer
Consider microinverters for potential solution
Geographical site considerations for production-
smog, elevation, & Peak Sun Hours
High temperatures effect voltage (lowers)
High temperatures can effect equipment
Costs
Roof type and tilt or soil determines ease of installation
Requirements of interconnection- may require electrical
upgrade
29. Equipment selection:
component matching
Grid Direct Systems:
Inverter to Voltage (string design of array)
Match the inverter voltage window
Start voltage
Max of inverter as well as 600V DC limit per NEC code
Consider MPPT range
30. Equipment selection:
component matching
Grid Direct Systems:
Inverter to Voltage (string design of array)
Match the inverter voltage window
Start voltage
Max of inverter as well as 600V DC limit per NEC code
Consider MPPT range
Conductor chosen for ampacity and conditions
Mike Holt- Verifying System Design
31. Other BOS components…
Conduit and conductors chosen for conditions and NEC
requirements
Ex.: NEC requires metal conduit for DC conductors run inside of
a building - NEC 690.31(E)
Ex.: PV Source conductors must be USE-2 or PV wire- NEC
690.31(B)
All equipment must be DC rated (unless dealing with AC
modules/microinverters)
32. Component Selection:
utility interconnection requirements
Make sure panel is not overloaded
NEC705.12(A) - Supply side connections possible
Treated as service connections- reference to NEC 230
NEC 705.12(D)(5) - Circuit breakers must be “suitable
for backfeed” - if marked line and load, not suitable for
load side connection
33. Component Selection:
utility interconnection requirements
NEC 705.12(D) - Utility Interactive inverters
NEC 705.12(D)(2) - load side connection- 120% rule allowed
Sum of amp rating of OCPDs connected must not exceed 120%
of rating of busbar
Ex. 200A bus bar x 1.2 = allowable 240A OCPDs
240A - 170A = 70A
170A in use, then max load side connection is 70A
Exception - with battery bank- can use inverter output
current:
Ex. 30A output from inverter = 30 x 1.25 = 37.5A, 40A OCPD
37. Who are we, and who am I?
SolPowerPeople, Inc.
IREC Accredited Continuing Education Provider
Offering Solar Training, in person and online
Sarah Raymer
Director of Education and Training
Asst. Instructor, #SolarMOOC host
NABCEP Certified PV Installation Professional
sraymer@solpowerpeople.com