Networks I

1
Networks I

• ECE 09.201.01 and ECE 09.201.03
• Lecture 12 PV System Designs
• 15 October 2008
• Dr Peter Mark Jansson PP PE

2
Solar Power (1994 -2006)
Wind production PV production
3
2007 Results

• Global Wind is now over 20,000 MW/yr a dramatic
  30 increase over 2006
• Global PV increased to over 3,800 MW/yr
• a growth of over 117

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PV Market
5
Solar Resources Total Diffuse
6
Generic PV cell
Incoming Photons
Top Electrical Contacts
electrons ?
- - - - Accumulated Negative Charges - - - -
n-type
Holes
E-Field
Depletion Region


- - - - - -
- - -
Electrons
p-type
Accumulated Positive Charges
Bottom Electrical Contact
I ?
7
From Cells to Arrays
8
Photovoltaics Practical Information

• Approx South Facing Roof or field
• Roof angles from 20-50 degrees
• Less than 200 from loads
• Every 70 square feet of area can yield up to 1000
  kWh per year in New Jersey
• 90 solar window required
• Each 1 kW-DC installed can yield about 1200 kWh
  annually

9
Orientation and Incoming Energy
10
PV Module Prices (still around 4/watt)
Source P. Maycock, The World Photovoltaic Market
1975-1998 (Warrenton, VA PV Energy Systems,
Inc., August 1999), p. A-3.
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Economic Value a NJ Farm

• PV Systems would have 25-30 year payback without
  CORE rebates from NJBPU or SRECs from the NJ
  Market
• With NJCEP Rebates and/or SRECs the payback
  reduces to less than 10 years
• PV Systems can produce between 1100 and 1350 kWh
  per installed kW annually across New Jersey
• Todays Pricing
• 6.50-8.00/Watt depending on size

12
PA 3MW photovoltaic array
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Solar panels - BP 4175

• Rated Power 175 W
• NOCT 47 C
• Length 1.58 m
• Width 0.808 m
• maxP Voltage 35.2V
• maxP Current 4.95A

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LAB Information
http// www.rowan.edu/cleanenergy/RISE http//map
s.google.com
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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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Azimuth-?s and Altitude-?N
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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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Another Module

• SunPower
• PV Module Conergy S 175MU
• Pmp 175 Wp
• Vmp 35.2 V
• Imp 4.85 A
• Voc 44.2 V
• Isc 5.2 A
• Voc at -20 C cell temp 51.0 V
• Vmp at 75 C cell temp 29.2 V
• Technology monocrystalline
• Max series fuse 15A
• UL1703 listed

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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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Combiner 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 HIGHER 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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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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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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Grid Connected System Sizing

• See Sample PV System Wiring Diagram

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Stand-Alone PV System Designs
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Grounding
50
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/