Pv solar plant components

 2012 Jim Dunlop Solar
Chapter 4
System Components and
Configurations
Major Components ● Balance-of-System
● System Classifications and Designs

 2012 Jim Dunlop Solar System Components and Configurations: 4 - 2
Overview
 Identifying major PV system components and their functions,
including PV modules and arrays, energy storage, power
conditioning equipment and other energy sources.
 Discussing the key trends and sources of U.S. energy supply and
consumption.
 Identifying the key components of the electrical utility system
and the differences between centralized and distributed power
generation.
 Identifying the basic types of stand-alone and interactive PV
systems, their operating principles and major components.

Solar Photovoltaic (PV) Systems
 Solar PV systems are electrical generators that produce energy for
electrical loads and may interface with other electrical systems.
Electrical
LoadEnergy
Source
Power
Conditioning
Energy
Conversion
Inverter
PV Array
Power
Distribution
Load
Center
Battery
Energy
Storage
(optional)
Electric
Utility

Major System Components
 Photovoltaic (PV) Array
 An assembly of PV modules that convert sunlight to DC electricity.
 Power Conditioning Equipment
 Inverters, chargers and controllers that process DC power from PV arrays
and produce AC power for utilization loads.
 Energy Storage
 Batteries store energy produced by PV arrays, and are used in most
stand-alone systems, but only in specially-designed grid-tied systems.

PV System Components
1. PV modules and array
2. Combiner box
3. DC disconnect
4. Inverter (charger & controller)
5. AC disconnect
6. Utility service panel
7. Battery (optional)
1
2
3
4
5
7
6

Balance-of-System Components
 Balance-of-System (BOS) Components
 Mechanical or electrical equipment and hardware used to assemble and
integrate major components, and to conduct, distribute and control the
flow of power in the system.
 Examples of BOS components include:
 Conductors (wiring)
 Raceways (conduit)
 Junction and combiner boxes
 Disconnect switches
 Fuses and circuit breakers
 Terminals and connectors
 Array mounting hardware

PV Modules and Arrays
 PV modules are assembled electrically and mechanically to form an
integrated DC power supply.
 An array is the total DC power generating unit designed to produce a
specified electrical output.
PV Array
PV Module

Energy Storage
 Batteries are the primary type of energy storage used in PV
systems, and transform electrical and chemical energy.
 Other types of energy storage systems include:
 Flywheels store kinetic energy
 Supercapacitors store electrical charge
 Fuels store chemical energy
 Hydroelectric dams and compressed air systems store potential energy

Batteries
 Batteries are used in most stand-
alone PV systems to store
energy from the PV array and
establish the operating voltage
for DC utilization equipment,
such as inverters or DC loads.
 Lead-acid batteries are the most
common type used in PV
systems.
Flooded Lead-Acid
Sealed Lead-Acid

Power Conditioning Equipment
 Power conditioning equipment converts, controls or processes
the DC power produced by PV arrays, for interfacing with
electrical loads, utilization equipment or other electrical systems.
 Power conditioning equipment includes:
 Inverters
 Charge controllers
 Battery chargers
 DC-DC converters
 Maximum power point trackers

Inverters
 Stand-Alone Inverters
 Operate from batteries and supply power independent of the utility grid.
 Utility-Interactive or Grid-Connected Inverters
 Operate from PV arrays and supply power in parallel with the utility grid.
 Bi-Modal or Battery-Based Interactive Inverters
 Operate as diversionary charge controllers, and produce AC power output
to regulate PV array battery charging when the grid is energized.
 Transfer PV system operation to stand-alone mode and provide backup
electric power to critical loads when the utility grid is not energized

Inverters
Bi-Modal Inverter
Interactive Inverter
Stand-Alone Inverter

Charge Controllers
 A charge controller regulates battery
charging by limiting the charging
current from a PV array, and protects
a battery from overcharge.
 A load controller regulates battery
discharge current by disconnecting
electrical loads, and protects a
battery from overdischarge.
 A diversion charge controller
regulates battery charging by
diverting power to a DC diversion
load or grid-connected inverter.
48 V / 40 A Charge Controller
12 V / 10 A Charge Controller

Battery Chargers
 Battery chargers are commonly
used in stand-alone hybrid and
UPS systems where an AC
power source is available, such
as a generator or the utility grid.
 Many stand-alone inverters have
a built-in battery charger.
Xantrex/Schneider Electric
Separate Charger
Integral Inverter/Charger

Uninterruptible Power Supplies
 An uninterruptible power supply (UPS) is an emergency power
system that supplies electrical loads when the primary source of
power is lost.
 Typically includes a battery, charger, inverter and automatic
transfer switch.
 Grid-connected PV systems with battery storage are a type of
UPS system, transferring loads to the battery-inverter system
when the grid de-energizes.
 Unlike most UPS systems, the PV array still charges the batteries and
extends load operating time.

Maximum Power Point Trackers
 Maximum power point trackers
(MPPTs) are electronic devices
that operate PV modules or
arrays at their maximum power
output.
 MPPT functions are included in
all interactive inverters and in
some battery charge controllers.
 Also used at the PV module and
source circuit level for some
applications.
MPPT Controller
Module MPPT
Outback Power Systems
SolarMagic/National Semiconductor

Electrical Loads
 Electrical loads include DC or AC appliances or utilization
equipment that consumes power.
 DC loads typically operate from batteries and are used in some
small stand-alone PV systems, such as for lighting.
 AC loads are powered by inverters, generators or the utility grid.
 Electrical loads are characterized by their operating voltage (AC
or DC), power and energy consumption.
where
= load energy consumption (kWh/day)
= load average power (kW)
= load operating time (hrs/day)
E P t
E
P
t
= ×

Energy Sources
 Basic forms of energy include thermal, chemical, electrical,
kinetic and potential energy sources:
 Solar radiation
 Fuels (biomass, fossil and alternative fuels)
 Radioactive materials
 Hydro and geothermal
 Energy sources can be converted from one form to another with
various energy conversion devices.
 Steam, combustion and wind turbines
 Electrical generators
 Fuel cells
 PV devices

The Energy Dilemma

U.S. Energy Consumption
 U.S Energy consumption is growing at extraordinary rates.
The turning point: production peaks,
consumption exceeds production
DOE/EIA

U.S. Energy Flow
DOE/EIA
Quadrillion Btu [2007]

U.S. Electricity Flow
Quadrillion Btu [2007]
DOE/EIA

Central Power Generation
 Most power generation is centralized in remote areas and
transmitted over the grid to consumers in population areas. A
large percentage of the energy content in the fuel goes
unutilized.
Electricity33%
Fuel
100%
67%
Waste Heat
CO2 + Pollution
Power Plant
(Remote from thermal users)
Thomas Casten

Combined Heat and Power
 Combined heat and power (CHP) systems utilize waste heat from
electrical power generation for other purposes.
Fuel
100% Steam
Electricity
Chilled
Water
90%
10%
Waste Heat
CO2 + Pollution
CHP Plants
(located close to thermal users)
Thomas Casten

Electrical Generators
 Most electrical power is
produced from synchronous
generators that are mechanically
driven by turbines or engines.
 A typical generator consists of
an electromagnet, called the field
or rotor, which rotates inside a
coil of wire with an iron core,
called the stator.

Engine Generators
 Engine generators use internal
combustion engines to drive
electrical generators, and are
often used in conjunction with
off-grid PV systems.

Combustion Turbines
 Combustion turbines are large power generators that are similar
to jet engines.
Caterpillar/Solar Turbines

Microturbines
Ingersoll-Rand
 Microturbines are small gas turbine generators adapted for
distributed power and CHP applications.

Wind Turbines
 Small wind turbines are sometimes used in stand-alone off-grid
PV applications. Large turbines and wind farms are becoming
increasing popular for utility-scale power generation.
Southwest Windpower

Stirling Engines
 Stirling engines use an external heat
source, such as concentrated solar
energy, to compress a gas which
expands to produce mechanical
shaft power to drive an electrical
generator.
NREL/Bill Timmerman

Fuel Cells
 Fuel cells convert chemical to electrical energy directly. Most fuel
cells combine hydrogen and oxygen to produce heat, water and
DC electricity.
Fuel Cell
Water
DC Electricity
Heat
Hydrogen
Oxygen

Electric Utility System
 The electric utility system
consists of three principal
parts:
 Generation
 Transmission
 Distribution

Types of PV Systems
 Stand-Alone Systems
 Operate autonomously off-grid.
 Typically use batteries for energy storage.
 Sizing is based on electrical loads.
 Interactive Systems
 Operate in parallel with the electric utility grid.
 Intended to supplement site energy use from utility.
 Operation is independent of electrical loads.
 Do not generally use batteries or provide backup for utility power.

Direct-Coupled
Stand-Alone Systems
 Direct-coupled PV systems are the most basic type of stand-alone
system.
 A DC load is matched and directly connected to a PV module or array.
 Uses no energy storage.
 Load only operates when sun is shining.
PV Array DC Load
Water Pump or
Ventilation Fan

Stand-Alone PV System
with Battery Storage
 Most stand-alone PV systems use batteries to store energy
produced by the array for use by loads as required.
 A self-regulating PV system does not use charge control, but the
battery is susceptible to overcharge and overdischarge.
DC LoadPV Array Battery
Maximum charge must be
limited, typically lower
voltage modules are used.
Load must be well-defined,
operate daily and not
subject to user control.
Battery must be oversized in
relation to PV array charge
rates and daily load energy.

Stand-Alone PV Systems
with Charge Control
 A charge controller is required in most PV systems using
batteries to protect from overcharge and overdischarge, and may
also provide load control functions.
DC LoadPV Array
Battery
Charge
Controller

with Charge Control
Battery is not protected
from overdischarge by load.
Charge controller protects battery
from overcharge by PV array
PV Array
Charge
Controller
Battery
DC Load

Stand-Alone PV Systems with
Charge and Load Control
This controller
protects battery
from overcharge
This controller
protects battery
from overdischarge
PV Array
Battery
DC Load
Load
Controller
Charge
Controller

Multiple Charge Controllers
PV Subarray #1 Charge
Controller #1
One subarray may be
directly connected to battery
without charge control if
charge rates <= 3% of
battery capacity.
Controller #2
Controller #3
PV Subarray #4
Battery
DC Load or
Inverter

Diversionary Charge Control
PV Array
Charge
Controller
Battery
Diversion
Controller
Diversion
Load
This controller protects the battery when
the diversion load is unavailable
Diversionary controller protects the
battery from overcharge by diverting
power to a diversionary load

with AC Loads
DC LoadPV Array
Battery
Charge
Controller
Inverter/
Charger
AC Load AC Source
(to Charger Only)

Hybrid System
DC LoadPV Array
Battery
Charge
Controller
Inverter/
Charger
AC Load
Engine/Wind
Generator

Utility-Interactive PV System
Load
Center
PV Array Inverter
AC Loads
Electric
Utility

Utility-Interactive PV System
with Energy Storage
Inverter/
Charger
Critical Load
Sub Panel
Backup
AC Loads
Main Panel
Primary
AC Loads
Electric
Utility
Bypass circuit
BatteryPV Array
AC Out AC In
DC
In/out
Charge
Control

Bi-Modal System

Summary
 Major components used in PV systems include modules and
arrays, inverters, batteries, chargers and controllers.
 Balance-of-system components include electrical and
mechanical equipment needed to construct a complete PV
system and integrate the major components.
 Stand-alone PV systems operate off-grid and are designed to
power specific electrical loads.
 Interactive PV systems are connected to the utility grid and
supplement site electrical loads.

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