Photovoltaic

Association of Energy Engineers -NEA discussion about Solar Photovoltaics9/10/2014

Agenda

PV system overview & components

National Grid’s role in integrating Photovoltaic

The photovoltaic market , its benefits, and opportunities

Questions

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What is Photovoltaics? – MiniHistory

Edmund Becquerel, a French physicist, discovered that certain materials produced a current in 1839.

Prior to 1918 selenium was used in solar applications for its photoconductivity. Then a process to create single-crystal silicon was developed. (The vast majority of PV panels use silicon today!)

PV started to make its way into spacecraft design in the 1960s

National Grid deployed solar technology in the 1980s, launching solar installations on over 30 homes and businesses in Gardner, MA and app.75 kW installation at Beverly High School in Beverly, MA.

Current day it’s a new leaf of life, to live sustainably and use green energy is the transitioning mentality. Solar is used at the commercial level by utilities and residential level by many eager incentivized homeowners.

1830

1900

1970

2013

What is Photovoltaics?Basic PV Cell Operation

Circuit diagram attained from National Instruments (NI.com)Cell VI curve attained from boatdesign.net

System Overview

There are differences between large commercial PV arrays and smaller residential PV arrays.

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Residential System

Smaller solar systems will be encountered more often

Usually PV panels are roof-mounted which may make responding to emergency situations challenging

System components include:

Panels (Array)

Combiner box (Not shown)

Inverter

AC power disconnect (Panel)

Storage batteries (Not shown)

A basic residential PV system

Holt, Mike. Residential PV System Scope. Digital image. Mike Holt Enterprises, Inc. Charles Michael Holt, 11 Nov. 2011. Web. 22 July 2013.

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Commercial System

Large solar arrays typically have a power capacity of 150 kilowatts (kW) to 100 megawatts (MW) These arrays will have:

Combiner boxes for multiple strings of PV panels DC power disconnects Weather station System Rack Ballasts 1 or more large inverter High voltage AC power disconnect

National Grid’s 1.25 MW solar installation in Dorchester

System Components

Component identification is essential for ensuring safety and preventing health hazards.

A Solectria SGI 500W inverter at NG’s Dorchester solar site.

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Panels – Modules

Solar Modules are made up of silicon cells, a highly abundant element on earth

Monocrystalline production is old and inefficient

Polycrystalline production is more efficient and more current than monocrystalline production

These panels will be framed (aluminum or other lightweight/ durable metal)

Installing Evergreen Solar 210 Watt polycrystalline modules at National Grid’s NEDC site.

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Panels – Shingles

Another way to produce solar cells is with amorphous silicon.

To create these panels, silicon is vaporized and deposited on a flexible surface.

The advantage of this is the variety of application enabled by the flexibility of the solar panel.

NREL. 17W Solar Integrated Roofing Shingles. Digital image. National Renewable Energy Laboratory. WebDAM, n.d. Web. 22 July 2013.

NREL. Roofing Shingles. Digital image. National Renewable Energy Laboratory. WebDAM, n.d. Web. 22 July 2013

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Panels - Measurement Devices

For data collection purposes, measurement devices may be attached to modules.

Module Surface Temperature Sensor - measures temperature of module

Pyranometer – measures solar irradiance (amount of radiation per unit area)

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Combiner Boxes

Each string of modules will have a combiner box.

This is a central place where all the modules on that string connect.

Small arrays will have one combiner box while large arrays will have many.

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DC disconnects

An Important feature of a PV system are the disconnects

The DC disconnects are usually located near the panels, after the combiner boxes.

NOTE: Even after panels are disconnected, electricity is still generated when the panels are exposed to light.

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System Rack

The rack provides the mounting structure for the panels and other PV instruments

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Ballasts

Some PV systems are not mounted directly to the surface they are on. Instead, heavy footings made of rubber, cement, or other durable material is provided to secure the rack and panels. These can weight 300 Ib each.

Ballasts are used on ground or flat roofs

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Inverters

The inverters will convert DC to AC so the solar system can tie to the grid or supply power to a household.

These units contain high voltages.

Caution: These contain large capacitors that will continue to hold a lethal charge even after being disconnected from the grid side and panel side

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AC disconnects

An AC disconnect is the “main power” shut off in a PV system. This is where the solar array will connect to the grid.

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Storage Batteries

Storage batteries are becoming practical for commercial solar applications . Currently, most battery systems will be found in residential applications.

During times of overcast or at night the PV system will use battery power to continue providing electricity to the home.

NREL. Solar Battery System . Digital image. National Renewable Energy Laboratory. WebDAM, n.d. Web. 22 July 2013.

NREL. Solar Battery System 2 . Digital image. National Renewable Energy Laboratory. WebDAM, n.d. Web. 22 July 2013.

Why does National Grid invest in PV?

Why is National Grid doing PV?

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• Since 2009, National Grid has integrated over 300 MW of third party-owned distributed generation facilities within its service territory.

• National Grid is looking to integrate a greater number of projects with higher benefits to customers, developers and the electric distribution system, especially given the Commonwealth’s new goal of 1,600 MW of solar by 2020, set by Governor Deval Patrick.

• Installing solar generation in pre-selected areas will enable the company to experiment with new tools and unlock technical challenges. Which National Grid will share with the entire energy community, assisting toward the Commonwealth’s clean energy goals.

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The Green Communities Act (GCA)

The Green Communities Act was passed in MA in 2008

Allowed investor owned utilities to own, operate and recover the cost of 50 MW of solar

Grow the solar industry and stimulate broader economic growth

Advance the market to lower the cost of renewables

Achieve 250 MW of solar power installations by 2017

Meet at least 20% of the states electric load by the year 2020 through renewable and alternative energy generation

Company Owned Solar

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Phase I Solar Constructed 5MW’s of PV Five sites: Dorchester, Haverhill, Everett,

Revere and Sutton Production and more facts can be found at:https://www.nationalgridus.com/masselectric/solar/

Phase II Solar DPU approved June 28, 2014.

Objective: Purchase 20 MW of turn-key solar

sites Implement advanced inverters Learn more about impacts of solar on

areas with: High PV Penetration Lightly Loaded feeders Heavy Loaded Feeders

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National Grid Solar Phase I

National Grid owns the systems.

Energy (kWh) and Solar renewable energy certificates (SRECs) are sold to the market at prevailing market prices and are used to offset the cost of the installation.

Project is financed by National Grid’s customers in MA through an approved monthly fee added to the electric bills.

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Dorchester - 1,250 kW

Waltham - 225 kW

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Everett – 605 kW

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Haverhill – 1016 kW

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Revere – 750 kW

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National Grid Solar Phase II

In progress…

Expected Completion: June 30th, 2014

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The Photovoltaic Market

The Benefits of PV

Known Benefits

Reduced carbon footprint

Reduced fossil fuel consumption by conventional power plants

Reduced energy bills for customers

Providing jobs

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The Benefits of PV

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Solar Emissions Offset of National Grid Sites

The Benefits of PV

Potential Benefits

Reducing the effects of outages

Reducing utility system and customer costs

Grid support through advanced inverter technology

Power quality

Reliability

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Economics of Solar Generation

Dependent on

scale, solar variability, intermittency, carbon displacement

ancillary services vs. displacement of other type of generation (carbon intense)

Locational Marginal prices and solar power production

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Economic benefits

Employment opportunity

Investment opportunities

New sources of income for property owners

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Capital Costs

Courtesy of NREL

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Expected O&M

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Courtesy of NREL

Useful Life

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Courtesy of NREL

Solar in the U.S.

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Solar generation in New England

Location Capacity FactorBoston, MA 14.2%Lynchburg, VA 15.3%Boulder, CO 16.7%Albuquerque, NM 19.2%Flagstaff, AR 18.4%San Francisco, CA 16.5%San Diego, CA 17.1%* Values from NREL’s PVwatts

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Is PV feasible in New England?

How does it compare with other locations in the US?

Solar Renewable Energy Credits (SRECs)

-- SRECs are an opportunity for solar plants to create income --

A SREC is attained for each MWh produced by a solar renewable energy

Want to increase plant efficiency and decrease power consumption

Can be worth significantly more than LMP

In rare cases, LMP goes to 0, or even negative

Renewables stay on as long LMP > REC price

Companies create renewable portfolios

Some states mandate Renewable Portfolio Standards (RPS)

Energy Created

Accounted for by ISO RECs Issued

Put into RPS by owner or

sold

Investment Tax Credit (ITC)

A Federal policy created by the Energy Policy Act of 2005 to encourage renewable energy growth

Solar developers receive a 30% tax credit on residential and commercial PV systems.

Currently, the ITC will continue through December 31,2016

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Financing – PPA

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-- Power Purchase agreement –

No construction/installation cost for customer

Customer pays a specific rate for electricity generated

At end of term property owner extends contract or buys the PV system

Financing PV – Lease

-- Lease --

Customer signs a tradition lease and pays for the use of the system

Allows for minimal to no up-front costs

Eventual ownership

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Investment based on tariffs rather than contracts

Long term contracts are not always the best answers

Rhode Island General Assembly introduced approved new renewable energy bill H-7727 and S-2690

Renewable energy developers are guaranteed a long term tariff instead of a contract

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Net Metering

Gaining popularity as distributed generation (DG) grows

Allows the tracking of imported and exported electricity for finances.

If customer generates more energy than consumed, an electricity credit will be issued.

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Virtual (or remote) Metering

Allows customers with net metered PV to allocate net metering credits to other NG accounts within the ISO-NE load zone

Helps customers who are interested in PV

May not be best fit for customers without DG

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Challenges to Large Scale PV Generation

Peak power output around midday – summer peak power usage is early evening

Land availability – clearing woodland for solar panels?

Unknown effects of large scale use of renewable energy on the Grid –renewable energy sources are not predictable.

Resiliency without battery storage

PV is subject to:

Weather intermittency

Peak load demand

Night time

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Potential problems:

Slow transients that can cause voltage swings on feeders

Peak load demand will not be alleviated if maximum generation azimuth is used

Base load PPs cannot quickly change with solar generation variance

Resiliency with battery storage

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Possible solution to:

Voltage fluctuations

Maximum generation and peak load demand relief trade off

Night time generation

Courtesy of NREL

Looking to install a PV systems at a facility?

Fixed PPA VS variable PPA. What is the risk?

Guaranteed output?

Is the assumed utility rate increase per year for the life of the contract valid?

Is the energy degradation factor of the solar generation over the life of the system reasonable?

Is the fixed PPA $/ kWh reasonable?

Robust O&M plans?

At the end of contract term, what are the costs associated with dismantling, owning, or extending the contract?

Is there a lease payment for the property and is fair?

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Questions