Advanced Power Systems

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Advanced Power Systems

• ECE 09.402.02 and ECE 09.504.02
• Lecture 10 PV System Designs
• 2 April 2007
• Dr Peter Mark Jansson PP PE

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Project Help

• This page offers many tools specifically for
  small wind
• http//www.renewwisconsin.org/wind/windtoolbox.htm
  l

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Technology Aid

• Sun Path Diagrams
• Solar PathFinderTM
• SunChart
• Allows location of obstructions in the solar view
  and enables estimation of how much reduction in
  annual solar gain that such shading provides

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PathFinder and Assistant
www.solarpathfinder.com
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Sun Path diagram
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Maximize your Solar Window
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CURRENT-VOLTAGE (I-V) CURVE
Standard Test Conditions (STC) 25C (77F)
cell temperature and 1000 W/m² insolation

• Important Points
• Maximum Power Point ( Vmp , Imp )
• Open Circuit Voltage ( Voc )
• Short Circuit Current ( Isc )

Voc
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VOLTAGE TERMINOLOGY

• Nominal Voltage ? 12 V
• (A PV panel that is sized to charge a 12V
  battery, but reads higher than 12V)
• Maximum Power Voltage (Vmax/Vmp)?17V-18V under
  STC
  (A 12V module will read 17V18V
  under MPPT conditions)
• Open Circuit Voltage (Voc) ? 20V-22V
  (This is seen in the early morning, late evening,
  and while testing the module)

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EFFECTS OF TEMPERATURE
Fahrenheit To Celsius Conversion

___C (5/9)( ___F - 32) OR ___F
(9/5)( ___C) 32
Example 25C (5/9) (77F - 32)
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BP 3160

• Rated Power 160 W
• Nominal Voltage 24V
• V at Pmax 35.1
• I at Pmax 4.55
• Min Warranty 152 W
• NOTE I-V Curves

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Other I-V Curves

• SunPower

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WATTAGE COMPARISON
BP Solar Polycrystalline
BP Solar Monocrystalline
Uni-Solar Amorphous
SunPower Back Contact
64 Watts __________________________________
_______________ _ 53.8 in x 29.2 in
__________________________________________________
____


20.2 lbs.
Source http//www.uni-solar.com
Source www.sunpowercorp.com/
Source http//www.bp.com/solar
Source http//www.bp.com/solar
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JUNCTION BOXES
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From modules to arrays

• Method
• First Determine Customer Needs (reduce)
• Determine Solar Resource (SP, model, calcs)
• Select PV Modules or
• Select DC-AC Inverter
• Look for Maximum Power Tracking Window
• Max DC voltage Current
• Assure Module Strings Voc and Isc meet inverter
  specifications

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SERIES CONNECTIONS

• Loads/sources wired in series
• Voltages are additive
• Current is equal
  (through all parts of the circuit)
• One interconnection wire is used between two
  components (Negative connects with
  positive)
• Combined modules make a series-string
• Leave the series string from a terminal not used
  in series connection

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PARALLEL CONNECTIONS

• Loads/sources are wired in parallel
• Voltage remains the same
• Currents are additive
• Two interconnection wires are used between two
  components (positive to positive and negative to
  negative)
• Leave from any parallel terminal to the next
  system component

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MODULES WIRED IN SERIES and PARALLEL

• Note In reality, this system would require
  series fusing for only 2 series strings and under
  can go without fusing by NEC

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MODULES WIRED FOR HIGH VOLTAGE
____V ____A
17V x 8 136
4
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Use the Same Modules

• Significant reductions in output can be observed
  when using dissimilar modules
• It can be done but you must be very careful in
  your analysis and design to see if it is worth it

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DISSIMILAR MODULES IN SERIES
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DISSIMILAR MODULES IN PARALLEL
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See Mesa Environmental Solar Audits

• Spreadsheet Customer Monthly Consumption
• Determine potential Shade Free Sites
• ID source for local Solar Resource Info
• Model (PVWATTS, PV FCHART, NJCEP)
• Weather Service Data
• Actual measurements from region

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Remember

• PV modules stack like batteries
• In series Voltage adds,
• constant current through each module
• In parallel Current adds,
• voltage of series strings must be constant
• Build Series strings first, then see how many
  strings you can connect to inverter

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Match Modules With Inverter

• Find Optimal Fit of Series Strings
• TO BE IN MAX POWER TRACKING WINDOW
• Assure module s do not exceed Voc
• Find Optimal of Strings in Parallel
• TO MEET MODULE POWER RATING
• CURRENT TO BE LESS THAN MAX Isc
• Are Modules and Inverter a good match?
• Overall Hardware Utilization efficiency

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Putting it all Together

• Customer Needs (energy usage ? reduce)
• PV System Design Requirements
• Solar Resource Assessment
• Potential Sites on Customer Property
• PV Module Inverter Selection
• Wiring Diagram
• System Economic Analysis

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Wiring the System
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Utility Interactive PV
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Utility Interactive with Battery
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Key Concepts of Chapter 9

• Photovoltaic system types
• Resistive loads for I-V curves
• Maximum Power Point Trackers
• Interfacing with Utility - Inverters
• NJ Incentives
• Grid Connected System Sizing
• Stand-Alone System Design

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PV system types

• Grid Interactive and BIPV
• Stand Alone
• Pumping
• Cathodic Protection
• Battery Back-Up Stand Alone
• Medical / Refrigeration
• Communications
• Rural Electrification
• Lighting

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Grid Interactive
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Grid-interactive roof mounted
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Building Integrated PV
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Stand-Alone First House
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Remote
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Maximum Power Trackers
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NJ Incentives

• NJ Clean Energy Program
• 40 rebate for grid connected systems up to 10kW
• Smaller rebates for increments above 10kW
• Net Metering to 2 MW
• Solar Renewable Energy Certificates
• NJ RPS requires
• Currently trading about 250/MWh

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Economic / Market Impacts

• Systems would have 25-30 year payback
• With NJCEP reduces to 14 year
• With SREC could be less than 10 year
• Lets see an example

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Grid Connected System Sizing

• See Sample PV System Wiring Diagram

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Stand-Alone PV System Designs
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Grounding
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All equipment should be grounded
All Stainless and copper components UL
outdoor rated
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Bonded to an Earth ground
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Specifying Inverter

• Watts output AC total connected watts of PV
• STC Rating
• DC voltage window array voltage
• 100-600 Volts DC typical (based on modules,
  Grid-tied systems have a high voltage window)
• Output voltage
• 120V / 240V (residential)
• 120V/ 240V/ 208V/ 480V (3-phase for commercial)
• Frequency 60hz (U.S.) or 50 hz (Europe)

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VOLTAGE INPUT FOR BATTERYLESS GRID-TIED INVERTERS

• Series string voltage needs to fit the inverters
  input window
• Voltage in a series string varies with
  temperature
• If PV array voltage is lower than inverters
  window ? no energy production
• If PV voltage exceeds inverters window ? could
  damage unit or void warranty

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AVAILABLE GRID-TIED INVERTERS
SMA
Source www.sma-america.com
POWER ONE
Source www.power-one.com
XANTREX
Source www.xantrex.com
KACO
Source www.kacosolar.com
FRONIUS
PV POWERED
SOLECTRIA
Source www.solren.com
Source www.fronius.com
Source www.pvpowered.com
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AVAILABLE GRID-TIED (WITH BATTERIES) INVERTERS
Grid-Tied with Batteries
SMA
Source www.outbackpower.com
Source www.sma-america.com

• OUTBACK

BEACON
XANTREX
Source www.xantrex.com
Source www.beaconpower.com
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Inverter/Module Sizing Tools

• SMA
• http//www.sma-america.com/
• Fronius
• http//www3.fronius.com/worldwide/usa.solarelectro
  nics/support/tool.html

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INVERTER SPECIFICATION EXAMPLE
Specifications for the Xantrex GT3
Source www.xantrex.com/
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EFFICIENCY vs. kWhOUTPUT OF INVERTER

• Only looking at efficiency can be misleading,
  other things to consider
• MPPT effectiveness (Start up ability during
  intermittent clouds)
• KWh output in high temperature
• Product reliability
• DC Voltage Window Start-Up point

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How NOT to fuse
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Assure the Hot Leg is Fused
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How much will PV System Make?

• PVWatts Tool
• http//rredc.nrel.gov/solar/codes_algs/PVWATTS/

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New homework

• HW 8 due next Monday 9 Apr
• now posted on web
• 9.1, 9.2, 9.4, 9.5, 9.6

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Lab Assignment 1

• Specify an 8 kw System for Atlantic City
• Where roof is south facing of 1200 SF
• And plot monthly output
• (According to PVWatts)