Sustainable Design in Engineering

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Sustainable Design in Engineering

• ECE 0909.403 ECE 0909.504.03
• Lecture 4
• Energy Fundamentals Sources of Electricity, the
  Heat Pump, and Sustainable Power Systems
• 22 September 2005
• Dr. Peter Mark Jansson PP PE

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Aims

• Keep Sustainability in Perspective
• Global, Regional, Local, Specific Products
• Introduce Energy Fundamentals and Sustainable
  Power Systems
• Heat Engines, Fossil Fuel Reserves
• Electricity Sources, Heat Pumps
• Sustainable Power Technology 1 - PV

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Heat Engines

• Devices that convert heat energy into mechanical
  energy
• History
• Steam Engine
• Savery 1698 (lt1 efficient)
• Newcomen 1705 (1 efficient)
• Watt 1770 (separate condenser 2 efficient)
• Steam Turbine (Parsons 1880 10 efficient)

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Heat Engine Efficiencies

• Modern Steam Turbines (30 efficient)
• Gasoline Engines (max. 20 efficient)
• Diesel engine (max. 30 efficient)
• Gas Turbines (20-30 efficient)
• Heat Pumps (C.O.P. of 2-12)
• Cogeneration Systems (gt70 efficient)

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Fossil Fuel Lifetimes

• Fossil Fuel Type Proven Reserves Est.
  Remaining Lifetime
•  
• Oil
• Global 999 x 109 bbl 40 years
• U.S. 72 x 109 bbl 16 years
• Natural Gas
• Global 5185 x 1012 ft3 60 years
• U.S. 600 x 1012 ft3 20 years
•  
• Coal
• Global 7.64 x 1012 tonne 200 years
• U.S. 1.5 x 1012 tonne 86 years, 66 years
•  
• SOURCE Jansson 2003

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U.S. Energy Use by Sector
9.4
35.6
28.4
26.7
SOURCE Ristinen and Kraushaar 1999
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Electricity Technologies

• Faraday Generators (gt1.2 Trillion)
• Photovoltaics (1.1 Billion)
• Thermoelectrics ( 500 Million)
• Fuel Cells ( 200 Million)
• Piezoelectrics (lt 20 Million)
• Magnetohydrodynamics

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History of Electricity

• 1831 Michael Faradays Electromagnetic Induction
  Experiment

switch
Soft iron ring
battery
N
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First Evolution DC Generator
Faraday 1831
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Second Evolution AC Generator
Pixii 1832
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AC Generator Output
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Lenz Law

• When an emf is generated by a change in magnetic
  flux according to Faraday's Law, the polarity of
  the induced emf is such that it produces a
  current whose magnetic field opposes the change
  which produces it. The induced magnetic field
  inside any loop of wire always acts to keep the
  magnetic flux in the loop constant. In the
  examples below, if the B field is increasing, the
  induced field acts in opposition to it. If it is
  decreasing, the induced field acts in the
  direction of the applied field to try to keep it
  constant.

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Lenz Law
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Steam Electric Power Plant
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Todays Electricity Mix
Fossil Fuels represent 63 of Total
18.8
16.9
1.5
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All the sources.
DEVICES
ENERGY SOURCE
User
Mechanical power in environment
Turbine Generator
Electromagnetic Induction
Ions
Piezo- Electric
Solar Power
Fossil and Biomass Fuel
Electrical power
Ions
Electro chemical cells
Chemical Energy
Electromagnetic Induction
Heat engine
Gas kinetic energy
MHD
Ion kinetic energy
HEAT
EHD
Free electrons
Thermoionic converter
Thermo electric generator
Semiconductor electrons / holes
Radiation
Infrared photovoltaics
Nuclear, Hydrogen, other thermal
Visible photo voltaics
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Overview of Heat Pumps

• Prime Purpose Move Heat
• Types
• Air to Air
• Water to Air
• Earth to Air
• Water to Water
• COP Energy Moved / Energy Consumed

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Heat Pump - Cooling Mode
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Heat Pump - Heating Mode
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Overview of Sustainable Power

• Nothing is truly sustainable indefinitely
• We actually speak of a technology being
  sustainable in relative terms (many
  centuries, compared to)
• Which power and energy technologies are more
  sustainable (or less) than others?

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Wind Power

• Sustainable
• Potentially Sustainable
• Not Sustainable

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Nuclear Fission Power (U238)

• Sustainable
• Potentially Sustainable
• Not Sustainable

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Coal

• Sustainable
• Potentially Sustainable
• Not Sustainable

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Hydroelectric Power

• Sustainable
• Potentially Sustainable
• Not Sustainable

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Thermoelectric Power

• Sustainable
• Potentially Sustainable
• Not Sustainable

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Photovoltaics

• Sustainable
• Potentially Sustainable
• Not Sustainable

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All Known Sources of Electricity
DEVICES
ENERGY SOURCE
User
Mechanical power in environment
Turbine Generator
Electromagnetic Induction
Piezo- Electric
Solar Power
Ions
Fossil and Biomass Fuel
Electrical power
Electro chemical cells
Ions
Chemical Energy
Heat engine
Electromagnetic Induction
Gas kinetic energy
MHD
HEAT
Ion kinetic energy
EHD
Thermoionic converter
Free electrons
Thermo electric generator
Semiconductor electrons / holes
Infrared photovoltaics
Nuclear, Hydrogen, other thermal
Radiation
Visible photo voltaics
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Sustainable Technology 1 Photovoltaics
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Key Concepts from Chapter 7

• The Solar Spectrum
• Our Star the Sun
• 1.4 million km diameter
• 3.8 x 1020 MW of electromagnetic energy
• Blackbody radiation depends on temperature
• The Sun 5800 oK
• The Earth 288 oK

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Earth receives Sunlight reflects Earthlight

• The Earths atmosphere reacts very differently
  to the much longer wavelengths emitted by the
  Earths surface compared with the relatively
  shorter wavelengths arriving from the Sun. This
  difference is the fundamental factor responsible
  for the greenhouse effect Masters, p. 387

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Solar declination
where n 1(Jan1), 32 (Feb1), 60(Mar1),etc.
Source The American Ephemeris and Nautical
Almanac
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Solar Declination is really .
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Solar declination
NOTE Tropic of Cancer is 23.45o (N Latitude),
Tropic of Capricorn is -23.45o (S Lat.)
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Declination responsible for day-length

• North of latitude 66.55o (the Arctic circle) the
  earth experiences continuous light at the summer
  solstice
• South of latitude -66.55o (the Antarctic circle)
  the earth experiences continuous darkness at the
  summer solstice
• North of latitude 66.55o (the Arctic circle) the
  earth experiences continuous darkness at the
  winter solstice
• South of latitude -66.55o (the Antarctic circle)
  the earth experiences continuous light at the
  winter solstice

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Rule of Thumb

• Maximum annual solar collector performance
• Achieved when collector is facing equator, with a
  tilt angle equal to latitude (north or south
  latitude)
• Why?
• In this geometry (the collector facing the
  equator with this tilt angle) the solar radiation
  it receives will be normal to its surface at the
  two equinoxes

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Maximum Performance on Any Day

• Maximum solar performance
• Achieved when collector is facing equator, with a
  tilt angle equal to 90o - ?N
• What is ?N ? Altitude angle angle between the
  sun and the local horizon directly beneath the
  sun at solar noon

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Solar position in sky

• Suns location can be determined at any time in
  any place by determining or calculating its
  altitude angle (?N) and its azimuth.
• Azimuth is the offset degrees from a true
  equatorial direction (south in northern
  hemisphere), positive in morning (E of S) and
  negative after solar noon (W of S).

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Solar Hour angle (H)

• Solar Hour angle (H) is the number of degrees the
  earth must rotate before the sun will be directly
  above your local meridian (due true south for
  most of us).

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Solar position in sky
where ?altitude, ?S azimuth, Llatitude,
?declination, Hhour angle
Note In spring summer in early morning and
late afternoon azimuth may be greater than 90o,
so must be tested
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Solar position in sky
Note In spring summer, in the early morning
and in the late afternoon azimuth may be greater
than 90o, so azimuth angle ?s must be tested
where Llatitude, ?declination, Hhour angle
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Technology Aid

• Sun Path Diagrams
• Solar PathFinderTM
• Allows location of obstructions in the solar view
  and enables estimation of how much reduction in
  annual solar gain that such shading provides
• We will visit this again in PV system design

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Magnetic declination

• When determining true south with a magnetic
  compass it is important to know that magnetic
  south and true (geometric) south are not the same
  in North America, (or anywhere else).
• In our area, magnetic south is /- 10o west of
  true south

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Total Solar Flux (units)

• kWh/m2
• Most common
• 316.95 Btu/ft2
• 85.98 langleys
• langley
• 1 cal/cm2
• 41.856 kjoules/m2
• 0.01163 kWh/m2
• 3.6878 Btu/ft

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Flux changes based on orientation

• Fixed Panel facing south at 40o N latitude
• 40o tilt angle 2410 kWh/m2
• 20o tilt angle 2352 kWh/m2 (2.4 loss)
• 60o tilt angle 2208 kWh/m2 (8.4 loss)
• Fixed panel facing SE or SW (azimuth)
• 40o tilt angle 2216 kWh/m2 (8.0 loss)
• 20o tilt angle 2231 kWh/m2 (7.4 loss)
• 60o tilt angle 1997 kWh/m2 (17.1 loss)

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Benefits of tracking

• Single axis
• 3,167 kWh/m2
• 31.4 improvement at 40o N latitude
• Two axis tracking
• 3,305 kWh/m2
• 37.1 improvement at 40o N latitude

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Total Solar Flux

• Direct Beam
• Radiation that passes in a straight line through
  the atmosphere to the solar receiver (required by
  solar concentrator systems) 5.2 vs. 7.2 (72) in
  Boulder CO
• Diffuse
• Radiation that has been scattered by molecules
  and aerosols in the atmosphere
• Reflected
• Radiation bouncing off ground or other surfaces

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Annual Solar Flux variation

• 30 years of data from Boulder CO
• 30-year Average 5.5 kWh/m2 /day
• Minimum Year 5.0 kWh/m2 /day
• 9.1 reduction
• Maximum Year 5.8 kWh/m2 /day
• 5.5 increase

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Benefits of Real vs. Theoretical Data

• Real data incorporates realistic climatic
  variance
• Rain, cloud cover, etc.
• Theoretical models require more assumptions
• In U.S. 239 sites have collected data, 56 have
  long term solar measurements (NREL/NSRDB)
• Globally hundreds of sites throughout the world
  with everything from solar to cloud cover data
  from which good solar estimates can be derived
  (WMO/WRDC)

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Solar Flux Measurement devices

• Pyranometer
• Thermopile type (sensitive to all radiation)
• Li-Cor silicon-cell (cutoff at 1100?m)
• Shade ring (estimates direct-beam vs. diffuse)
• Pyrheliometer
• Only measures direct bean radiation

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PV History

• 1839 Edmund Becquerel, 19 year old French
  physicist discovers photovoltaic effect
• 1876 Adams and Day first to study PV effect in
  solids (selenium, 1-2 efficient)
• 1904 Albert Einstein published a theoretical
  explanation of photovoltaic effect which led to a
  Nobel Prize in 1923
• 1958 first commercial application of PV on
  Vanguard satellite in the space race with Russia
  

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Wind PV Production (96-02)
Wind production PV production
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Historic PV price/cost decline

• 1958 1,000 / Watt
• 1970s 100 / Watt
• 1980s 10 / Watt
• 1990s 3-6 / Watt
• 2000-2004
• 1.8-2.5/ Watt (cost)
• 3.50-4.75/ Watt (price)

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PV cost projection

• 1.50 ? 1.00 / Watt
• 2005 ? 2008
• SOURCE US DOE / Industry Partners

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PV technology efficiencies

• 1970s/1980s ? 2003 (best lab efficiencies)
• 3 ? 13 amorphous silicon
• 6 ? 18 Cu In Di-Selenide
• 14 ? 20 multi-crystalline Si
• 15 ? 24 single crystal Si
• 16 ? 37 multi-junction concentrators

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Solar Resources - Direct Beam
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Solar Resources Total Diffuse
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Amorphous Si
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Amorphous Si
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Cadmium Telluride
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Multi-crystalline Si
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Multi-crystalline Si
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Single Crystal Si
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Semi-Conductor Physics

• PV technology uses semi-conductor materials to
  convert photon energy to electron energy
• Many PV devices employ
• Silicon (doped with Boron for p-type material or
  Phosphorus to make an n-type material)
• Gallium (31) and Arsenide (33)
• Cadmium (48) and Tellurium (52)

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p-n junction

• When junction first forms as the p and n type
  materials are brought together mobile electrons
  drift by diffusion across it and fill holes
  creating negative charge, and in turn leave an
  immobile positive charge behind. The region of
  interface becomes the depletion region which is
  characterized by a strong E-field that builds up
  and makes it difficult for more electrons to
  migrate across the p-n junction.

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Depletion region

• Typically 1 ?m across
• Typically 1 V
• E-field strength gt 10,000 V/cm
• Common, conventional p-n junction diode
• This region is the engine of the PV Cell
• Source of the E-field and the electron-hole
  gatekeeper

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Bandgap energy

• That energy which an electron must acquire in
  order to free itself from the electrostatic
  binding force that ties it to its own nucleus so
  it is free to move into the conduction band and
  be acted on by the PV cells induced E-field
  structure.

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Photons have more than enough or not enough
energy

• Sources of PV cell losses (?15-24)
• Silicon based PV technology max(?)49.6
• Photons with long wavelengths but not enough
  energy to excite electrons across band-gap (20.2
  of incoming light)
• Photons with shorter wavelengths and plenty
  (excess) of energy to excite an electron (30.2
  is wasted because of excess
• Electron-hole recombination within cell (15-26)

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p-n junction

• As long as PV cells are exposed to photons with
  energies exceeding the band gap energy
  hole-electron pairs will be created
• Probability is still high they will recombine
  before the built-in electric field of the p-n
  junction is able to sweep electrons in one
  direction and holes in the other

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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 ?
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PV Module Performance

• Standard Test Conditions
• 1 sun 1000 watts/m2 1kW/m2
• 25 oC Cell Temp
• AM 1.5 (Air Mass Ratio)
• I-V curves
• Key Statistics VOC, ISC, Rated Power, V and I at
  Max Power

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PV specifications (I-V curves)

• I-V curves look very much like diode curve
• With positive offset for a current source when in
  the presence of light

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From cells to modules

• Primary unit in a PV system is the module
• Nominal series and parallel strings of PV cells
  to create a hermetically sealed, and durable
  module assembly
• DC (typical 12V, 24V, 48V arrangements)
• AC modules are available

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PV Module Performance

• Temperature dependence
• Nominal operating cell temperature (NOCT)

Tc cell temp, Ta ambient temp (oC), S
insolation kW/m2
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PV Output deterioration

• Voc drops 0.37/oC
• Isc increases by 0.05/oC
• Max Power drops by 0.5/oC

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BP 4175

• Rated Power 175 W
• Nominal Voltage 24V
• V at Pmax 35.7
• I at Pmax 4.9
• Min Warranty 166.5 W
• NOTE I-V Curves

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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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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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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 Fixed, Tracking, 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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Dual Axis Trackers
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(No Transcript)
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Stand-Alone First House
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Remote
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NJ Incentives

• NJ Clean Energy Program
• 70 rebate for grid connected systems up to 10kW
• Smaller rebates for increments above 10kW
• Net Metering to 100kW
• Solar Renewable Energy Certificates
• NJ RPF requires 2 MW 2004 ? 10 MW 2008
• Currently trading about 200/MWh

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Economic / Market Impacts

• Systems would have 25-30 year payback
• With NJCEP reduces to 10 year
• With SREC could be less than 7 year
• Lets see an example