utility-grid intertied photovoltaic systems

Utility-grid Intertied Photovoltaic Systems

Dan Lepinski, P.E.

Dan@ntree.org

IEEE Power and Energy Society Presentation, October 16, 2018

Presenter: Dan Lepinski, P.E.Solar Design Engineer & ConsultantActive In the Solar Industry Since 1972

Synopsis

This presentation will provide a basic understandingof how the grid and solar electricity work together.

An overview of solar panels, inverters, wind power, micro-grids, energy storage, and related topics willbe covered.

Safety features and how solar energy systems react in the event of a grid failure will also be discussed.

� Voting Member - Underwriters Laboratories UL 1741 Standards Technical Panel.The STP authors the UL1741 Safety Standard for the entire solar energy industry.

Dan Lepinski, P.E. - Consulting & Design Engineer in the Solar & Power Industries

� Solar Industry Task Force Interacting with the National Fire Protection Association Code Panel 4. NFPA publishes the National Electric Code.

� Solar America Board for Codes and Standards (“Solar ABCs”)Interface with and advise the NEC Task Force and UL 1741 STP.

� Electric Power Research Institute "Smart Grid" Development CommitteeEngineers, scientists & experts address “next generation power grid” challenges.

� Intertek / ETL Consultancy GroupIntertek is one of several Nationally Recognized Testing Laboratoriescertified by OSHA to test products to UL Safety Standards.

� US Dept of Energy Building Codes Assistance Project. (2017, and ongoing…)One of only two engineers selected for participation in this national program.

� Active in the Solar Industry since 1972.

Your Presenter…

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Utility-Grid Intertied Photovoltaic Systems

� Solar Energy History & “PV” Fundamentals

� Inverters - What They Are - What They Do

� Wind Power

� Myths & Misconceptions about Solar Energy

� Solar Micro-Grids

� Energy Storage

� A Look Ahead

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� Safety Features

� Q & A

Today’s Presentation

� Basic Terminology

Utility-Grid Intertied Photovoltaic Systems

� Solar Energy History & “PV” Fundamentals

� Inverters - What They Are - What They Do

� Wind Power

� Myths & Misconceptions about Solar Energy

� Solar Micro-Grids

� Energy Storage

� A Look Ahead

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� Safety Features

� Q & A

� Basic Terminology

Photovoltaic (“PV”): Electricity from light

Basic “Solar" Terminology

Photovoltaic Array:

Solar Cell: Converts sunlight into electricity

Multiple photovoltaic modules

Photovoltaic Module: Multiple solar cells connected in one unit

Inverter: Device that changes DC to AC

(Must be a sine wave for “grid-tied” use.)

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“DER”: Distributed Energy Resource

Utility-Grid Intertied Photovoltaic Systems

� Solar Energy History & “PV” Fundamentals

� Inverters - What They Are - What They Do

� Wind Power

� Myths & Misconceptions about Solar Energy

� Solar Micro-Grids

� Energy Storage

� A Look Ahead

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� Safety Features

� Q & A

� Basic Terminology

A home in California in 1906

"Solar Printing Press" - Paris - 1882

Solar Energy Isn’t New…

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Solar collector for Solar collector for Solar collector for Solar collector for

heating waterheating waterheating waterheating water

A home in California in 1906

Solar hot water - California – 1906

Solar Energy Isn’t New…

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Solar Energy System

Solar Energy Isn’t New…

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Solar P

anels

Solar Energy System

Solar Energy Isn’t New…

1955 Bell Telephone Ad Promoting Solar Electricity.Bell Labs is credited with inventing solar cells.

Solar Energy Isn’t New…

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Monocrystalline Cell Polycrystalline Cell

Both are crystalline silicon. Manufacturing methods differ.

Most solar cells are black to various shades of blue…

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Tempered Glass

Ethelene Vinyl Acetate ("EVA")

Solar cells

Backsheet

Aluminum Frame

Ethelene Vinyl Acetate ("EVA")

Must withstand a minimum 1" hailstone at 55 mph. (UL 1703)

Supports snow, and withstands wind.

Seals environment out - permanently.

Survive 25+ years of heating and cooling.

Solar Panel Construction…

Cell

Module

Array

Definitions: "Solar Cell", "PV Module", "PV Array"

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Amorphous Silicon Cadmium Telluride Copper Indium

Gallium Selenide

"Thin-film" modules are reddish-brown, gray, or black.

This technology is often installed as "solar shingles“, and is used in flexible modules.

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Solar P

anels

Inverters

Solar Energy System

Utility-Grid Intertied Photovoltaic Systems

� Solar Energy History & “PV” Fundamentals

� Inverters - What They Are - What They Do

� Wind Power

� Myths & Misconceptions about Solar Energy

� Solar Micro-Grids

� Energy Storage

� A Look Ahead

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� Safety Features

� Q & A

� Basic Terminology

Inverters – The Basics

DC In

Some Models Are Single Phase*

* Depends on inverter brand and model. Output is o ne or the other, not both.

AC Output

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+ _

Note: Highest efficiencies have been independently lab-verified at 99%!

Inverter

Some Models Are Three Phase*(From solar panels )

Some General Considerations for Selection and Use:1. Sites where shade may be an issue.2. Odd-facing roof surfaces.3. Insufficient continuous roof surface.4. Allows for incremental system growth.5. System Size (typical): 2 kW to 50 kW, but may be larger.

"Micro-inverters"

Microinverters

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MicroMicroMicroMicro----inverters:inverters:inverters:inverters:

Typically 200-350 Watts each.Some models are up to 1,000 Watts.

Attach to racking or PV modules.

Typically one PV module per inverter. A few configurations have two, and sometimes four PV modules per inverter.

"Micro-inverter" System

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Output: 240Vac or 208 Vac three-phase.

Some General Considerations for Selection and Use:1. Slightly lower installation cost than micro-inverters in small systems.2. More easily serviced than micro-inverter systems.3. Inverter may be installed in an environmentally-friendly location.4. Typical output: 240Vac, 208V three-phase, 480V three-phase.

Note: Some Code-required hardware omitted for simplicity.

"String" Inverter System

Solar panels are connected one to another .. in a series"string". Inverter size (typical): 3.5 kW to 150 kW.

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(1) Inverter, (2) DC disconnect, (3) solar production meter (optional),(4) AC disconnect, (5) utility company meter.

1111

2222

3333 4444

5555

"String" Inverter System

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Photovoltaic modules

convert sunlight into

electricity.

"Inverter" - changes

solar "DC" into

household "AC".

Solar electricity serves the building

loads firstfirstfirstfirst. Any excess goes out to

the utility grid to the neighbors, and

may accrue credit to the owner.

Utility meter: Measures energy

consumed, and any excess energy

that may be fed back to the utility

grid.

“Local” Solar Electricity Works Like This...

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“Central" Inverter System – Utility Scale

Some General Considerations for Selection and Use:1. Large utility-scale three-phase (“solar farm”) systems.2. High power output. Typically 250 kW to 2.5 MW, 480 or 690V ac.3. Sometimes involve a long distance from the system to consumers.

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Urban Utility-Scale … Phoenix, Arizona

Photo Credit: Tim Roberts Photography / Shutterstock

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Urban Utility-Scale … San Antonio, Texas

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“Near-Rural” Solar Farm… Minnesota!

Photo Credit: Minneapolis/St Paul Business Journal

Rural “Solar Farm” - Imperial Valley, California

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Photo Credit: Kindle Project

Utility-Grid Intertied Photovoltaic Systems

� Solar Energy History & “PV” Fundamentals

� Inverters - What They Are - What They Do

� Wind Power

� Myths & Misconceptions about Solar Energy

� Solar Micro-Grids

� Energy Storage

� A Look Ahead

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� Safety Features

� Q & A

� Basic Terminology

Wind Power

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Blue & Purple = Greatest Wind Resource.

Wind Power

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Image: Green Mountain Energy Wind Farm - Fluvanna, Texas (SE of Lubbock)

Wind Power

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Texas is #1 in wind electricity in the USA…

… producing more than the next 3 states combined!

Transmission&

DistributionCompanies

600 MW

Coal & Natural Gas Plants

Residential Customers

Nuclear Plant

700 - 3,500 MW

Hydroelectric Plant600-800 MW Industrial Power Plant

10-30 MW

Medium Sized Plant

150 MW

Municipal Power Plant

Electricity GenerationCompanies

100 MW

Industrial Customers

Rural Customers

Retail Electric Providers

The Economics of Solar Energy

Let’s start with “How We’ve Always Done It”…

Customers

Customers

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The Economics of Solar Energy…

Why Is Distance Significant?

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The Economics of Solar Energy…

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Chart Credit: www.lazard.com (2017-2018 Data)

Utility-Grid Intertied Photovoltaic Systems

� Solar Energy History & “PV” Fundamentals

� Inverters - What They Are - What They Do

� Wind Power

� Myths & Misconceptions about Solar Energy

� Solar Micro-Grids

� Energy Storage

� A Look Ahead

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� Safety Features

� Q & A

� Basic Terminology

Solar Micro-Grids

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What is a "micro-grid?

Topologies vary:

Micro-grids can be capable of connecting to and operating in parallel

with the utility grid (as above), or operate in a “stand-alone” mode,

providing power for buildings, or up to entire communities.

Utility-Grid Intertied Photovoltaic Systems

� Solar Energy History & “PV” Fundamentals

� Inverters - What They Are - What They Do

� Wind Power

� Myths & Misconceptions about Solar Energy

� Solar Micro-Grids

� Energy Storage

� A Look Ahead

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� Safety Features

� Q & A

� Basic Terminology

Energy Storage

� BatteriesLead-AcidLithium-IonLithium Iron Phosphate“Flow” Batteries… and other developing battery technologies.

� Other ApproachesPumped WaterMolten Salts (heat storage)Fuel cellsHydrogen Generation (Combustion, and for use in fuel cells)Compressed AirFlywheels

� Advantages / Disadvantages of Each

Utility-Grid Intertied Photovoltaic Systems

� Solar Energy History & “PV” Fundamentals

� Inverters - What They Are - What They Do

� Wind Power

� Myths & Misconceptions about Solar Energy

� Solar Micro-Grids

� Energy Storage

� A Look Ahead

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� Safety Features

� Q & A

� Basic Terminology

Applicable Safety Standards (Not all shown)

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� UL 1703 – Photovoltaic Modules

� UL 1741 – All Electrical Equipment and Switchgear

� IEEE 1547 – Standard for Interconnection of "DER"

� NFPA 70 – National Electric Code

� IBC 2015 – Commercial Building Code

� IRC 2015 – Residential Building Code

� IFC 2015 – International Fire Code

� FCC Part 15 – Radio Frequency Interference

� IEEE 62.41 – Standard for Surge Withstand (‘B’ or ‘C’)� IEEE 37.90 – Standard for EMI/RFI Immunity

� UL 2703 – Rack Hardware (grounding)

Required System Safety Actions and Features

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� Cease operation if the grid goes down (“anti-islanding”).

� Stop generating power in the event of “abnormal” grid.

� Must wait five minutes after “good grid” to resume output.

� Sense and report “ground faults” and “arc faults”.Manual correction of fault required, then manual reset.

� Inverters are “current-limited” devices.

� “Rapid Shutdown”.

� … and others.

To be in compliance with the National Electric Code,all solar equipment must be certified to UL Safety Standards

by any of several Nationally Recognized Testing Laboratories.

These are the four most commonly used in the solar industry:

Underwriters Laboratories ("UL") Intertek ("ETL")

Canadian Standards Association("CSA") TÜV

A Comment About “Compliance”…

Despite decades of education, some inspectors still don't recognize any lab other than "UL".

Safety Features

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Utility-Grid Intertied Photovoltaic Systems

� Solar Energy History & “PV” Fundamentals

� Inverters - What They Are - What They Do

� Wind Power

� Myths & Misconceptions about Solar Energy

� Solar Micro-Grids

� Energy Storage

� A Look Ahead

45

� Safety Features

� Q & A

� Basic Terminology

Myths and Misconceptions About Solar Energy

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False.

The United States Department of Energy National Renewable Energy Laboratory proved PV systems "repay" their energy investment in about 2 years in the sun.

In other words .. a solar panel will generate as much energy in two years as it took to manufacture it. This includes the aluminum frame.

Source: US Dept of Energy, National Renewable Energy Laboratory, "PV FAQ Sheet", Report 35489.pdf, updated Sept 05, 2013.

The Top Four Solar Myths:

1. Solar panels require more energy to manufacture than

they’ll produce in their lifetime.

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The Top Four Solar Myths:

3. Solar energy is too expensive.

1. Solar panels require more energy to manufacture than

they’ll produce in their lifetime.

2. Solar manufacturing results in more pollution than is

saved by solar usage.

4. Solar equipment is ugly.

Take a close look – is this the profile

of a young lady, or the face of an

older woman?

They’re both here, but some of you see one woman, some see the other.

Solar energy is the same…

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Three Additional Common Myths and Misconceptions

5. Solar panels are heavy.

6. Solar panels work better in hot weather.

7. Solar panels require regular maintenance.

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ALL FALSE

Utility-Grid Intertied Photovoltaic Systems

� Solar Energy History & “PV” Fundamentals

� Inverters - What They Are - What They Do

� Wind Power

� Myths & Misconceptions about Solar Energy

� Solar Micro-Grids

� Energy Storage

� A Look Ahead

50

� Safety Features

� Q & A

� Basic Terminology

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Storage

Grid S

upport

Solar P

anels

Inverters

Solar Energy System

A Look Ahead…

1. Continued improvements in energy storage.

2. Expanded use of micro-grids.

3. “Community Solar”.

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4. Mandated Solar. Example: Starting in 2020, all new homes

built in California must have solar panels installed.

5. ULULULUL----1741 1741 1741 1741 ““““SASASASA”””” ---- Grid support: Grid support: Grid support: Grid support: (Utility companies take note!)(Utility companies take note!)(Utility companies take note!)(Utility companies take note!)

� Real time power factor correction adjustable by utility

� Peaking demand assistance

� Voltage “sag” detection and support

� Responsive to abnormal line voltage and frequency

� Adjustable power output and “ramp” rate

� System output controlled by utility company

In closing .. I’d like to leave you with the words of one

rather famous American, who said:

"I'd put my money on the sun and solar energy. What a source of power! I hope we don't have to wait until oil and coal run out before we tackle that."

~Thomas A. Edison ~(1847-1931)

…in conversation with Henry

Ford and Harvey Firestone...

Any idea who may have

made such an insightful

statement?

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Thank You!Thank You!

Contact Information:Contact Information:Dan Lepinski, P.E.Dan Lepinski, P.E.

Dan@ntree.orgDan@ntree.org817.884.6081817.884.6081

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