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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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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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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



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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



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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

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