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The Case for
Solar Monitoring
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Levels of Monitoring
1. Flying Blind
2. Direct Panel Testing with Multimeter
3. Hardware Readings
Inverters (on site/web interface) Smart Combiners
Micro Inverters
4. Monitoring Service
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Levels of Monitoring
Flying Blind
PROS:
No expenditures for
monitoring hardware andservice, site maintenance, etc.
CONS:
No insight whatsoever into
system performance Potential for sustained
economic losses due to sub-
par generation
Wont satisfy data reporting
requirements
No public-facing interface
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Levels of Monitoring
Direct Panel Testing with Multimeter
PROS:
Provides highly accurate info
about generation at the panellevel
CONS:
Highly expensive and time-
consuming process Potential for lost generation
between site visits
No insight into AC side
data/inverter performance
No ability to see systemoverview at a glance
Wont satisfy data reporting
requirements
No public-facing interface
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Levels of Monitoring
Hardware Readings
PROS:
Avoid expenditure for
monitoring service and addedhardware
Some manufacturers provide
web-based interface
CONS:
Most devices require
expensive site visit to gatherreadings
Potential for lost generation
between site visits (no alarms)
Not revenue grade metering;
wont satisfy data reporting
requirements
No ability to see system
overview at a glance
No public-facing interface
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Levels of Monitoring
Monitoring Service
PROS:
See performance of entire
system/multiple systems at aglance
Convenience of web-based
interface
Discover issues/locate
problem areas quickly
Many monitoring providers
offer revenue-grade data
Many providers offer public-
facing Dashboard
Many providers offer tech
support services
CONS:
Extra up-front cost for project
Additional hardwareinstallation process
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Why Monitor?
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Solar Power Systems
as Investments
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Performance Ratio and
the Bottom Line
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Potential Causes of Diminished
Performance Ratio
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Downtime Loss Scenarios
(Data from SolarPRO Magazine -- 500 kW system in Washington DC)
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The Basics ofSolar Monitoring Service
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Hardware for
Basic Monitoring
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CTs
(Current Transformers)
Placed around wiring coming out of inverter
Measures AC current coming out of inverter
Wired into meter
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Revenue Grade Meter
Revenue grade metering is
desirable
Must be compatible with all
reporting devices Industry is standardizing to
Modbus protocol
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Gateway
Prepares data for web
publication
Pushes data out to web
through local connection orcellular modem
Requires configuration to
send data to correct server
address
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Software for
Basic Monitoring
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Admin Panel Tools for O&M Secure password-protected interface
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Gauges display
real-time systemgeneration
numbers
Your systemin sync with
Mother Nature
Basic graphs
to engage and
educate the
public
See your energy
savings
Dashboard Intended for general public Ideal tool to generate Green PR
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Expanded MonitoringFunctions
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Inverter Communications Allows you to see
information from all
system inverters side by
side with other system
data
Get inverter fault codes
and production data
through web interface
For most projects, saves
time and money vs. site
visits to retrieve inverter
readings
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Environmental Sensors
(Weather Station)May include:
Irradiance sensor (plane of array)
Irradiance sensor (global) Ambient temperature
Panel temperature
Wind speed
Wind direction Barometric pressure
Humidity
Mounting hardware
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Environmental Sensors
(Weather Station)Recommended:
Irradiance sensor (plane of array) enables best
metrics to measure system performance: irradiance
vs. kWh (only way to account for varied weather
conditions)
High panel temperatures can lead to diminished
generation
Wind speed and direction, barometric pressure,
humidity: all less valuable data points
Beware of low price, low quality devices!
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Granular Monitoring Options
(DC side)Sub-array (Zone) Monitoring:
Divides your array into several independently reporting
nodes. Each zone requires individual meter device.
Each zone meter is separate data reporting charge.
String Monitoring:
Each string of panels becomes an independentlyreporting node. Strings are brought together at smart
combiner boxes, where each string is metered
independently. Each string is separate data reporting
charge.
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Analytical Power You Can See
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The Granular Monitoring Solution
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Monitoring Level Comparison
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Special Needs:
Wireless Data Communications
Avoid cost for digging trenches, etc
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Special Needs:
Cellular Modems Replaces local network connection
Necessary for remote project locations
May be necessary where local web networks includesubstantial security software/firewalls (military,
government, etc)
Requires separate data plan from cellular service
provider (customer responsibility)
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Special Needs:
Display Monitors Static display
Interactive display (requires
keyboard or touch screen)
Ideal for academic environments
or for businesses/organizations
with green PR initiatives
Can be useful tool to encourage
energy conservation efforts
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Associated Services:
System Planning/Engineering Hardware device selection
One-line wiring diagrams
Expert help for less experienced system planners
Ensures all hardware devices will communicate with
one another
Helps to avoid common problems and delays forinstaller
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Associated Services:Installation
Hands-off advisory service
Full installation service
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Associated Services:
Third Party Data ReportingMandatory in some markets (CA,
MA) in order to collect utility
rebates/ other performance-based
incentives
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Installing a
Monitoring System
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Installer should bring the following materials to assist in the
installation process:
Laptop computer
Digital multimeter
Wire and conduit necessary for installation
Small flathead and phillips head screwdrivers
Ethernet patch cable A small router or hub
Materials Needed
for Installation
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Correct Electrical Wiring
RS485/Modbus RTU Wiring Standards
Devices should be networked as a single bus
Network should originate from a single Bus Master
device Network shall include cable termination per Modbus
protocol specifications
Network wiring shall be executed with appropriate
cable
Devices that induce noise into the Modbus network
shall each require one RS-485 Optical Isolator
More info at www.modbus.org
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Correct Electrical Wiring
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Placing the CTs There is a label on the CT that
says Source Side. Orient this
side of the CT towards the
inverter, the AC combiner, or
the power source you are
monitoring (not the grid).
The accuracy of the CT
readings depends on the
conductor being centered in the
CT window. Where the CT falls
loosely on the conductor, use
electrical tape to center the
conductor.
Secure the end caps of split
core CTs with electrical tape.
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Correct Power Sources
Always consult manufacturer spec sheets to
determine appropriate voltage for each powered
device
Some systems may require multiple power sources
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Establishing Web
CommunicationsStructure of Web Networks
Web communications for monitoring system should go
through web network at project site (except in cases
where cellular modem is used)
Web network at project site is controlled by network
owner, notby monitoring service provider
Problems arising from firewalls and security software
must be resolved with an IT representative employed
by the local network administrator
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Establishing Web
CommunicationsConfiguring Gateway for Web
Communication
Installers will need the following list of items before
starting the configuration process:
Valid IP address for your network
Subnet Mask
Gateway IP address
DNS IP address