Sophomore Clinic

1
Sophomore Clinic

• 0909.202 Renewable Energy Lecture Part 1
• Renewable Power Systems Photovoltaics
• 5 April 2004
• Dr. Peter Mark Jansson PP PE

2
Renewable Lectures

• Technologies
• PV
• Wind
• Geothermal
• Todays Markets
• Costs cents per kWh
• Market Sizes and Growth

3
Todays Aims

• Overview of Costs and Markets
• Fundamentals of Photovoltaics
• Market
• PV Materials / Technologies
• PV Applications
• PV Standards
• PV Industry
• Sizing of PV Systems
• The Resource

4
Green Electric Pricing
Levelized cents/kWh in constant 20001
4030 20 10 0
100 80 60 40 20 0
PV
Wind
COE cents/kWh
1980 1990 2000 2010 2020
1980 1990 2000 2010 2020
70 60 50 40 30 20 100
1512 9 6 30
10 8 6 4 20
Solar thermal
Biomass
Geothermal
COE cents/kWh
1980 1990 2000 2010 2020
1980 1990 2000 2010 2020
1980 1990 2000 2010 2020
National Renewable Energy Lab Energy Analysis
Office (www.nrel.gov/analysis/docs/cost_curves_200
2.ppt)
5
Growing Green Markets
6
Historic Usage of PV

• Year Market Size Module Price
• 1958 First Application 1,000 / watt
• 1970 Satellite Applications 100 / watt
• 1975 lt1 MW per Year 30 / watt
• 1981 lt2 MW per Year 10 / watt
• 1990 lt15 MW per Year lt5 / watt
• 1994 69 MW per Year lt5 / watt
• 2001 320 MW per Year lt4 / watt

7
Todays PV Market
8
PV Market

• 1.1 Billion market
• Still not in mass production
• Numerous competitors
• Significant variation in applications

9
PV Materials / Technologies

• Flat Plate
• Thick Crystalline
• Crystalline Silicon (Si)
• Gallium Arsenide (GaAs)
• Thin Film
• Polycrystalline (CdTe, CIS)
• Amorphous (a-Si)
• Concentrators (Si)

10
Crystalline Silicon

• Single Crystal
• Sliced from single crystal boules
• 200 microns
• Cell efficiency 24
• Module effic 15

11
Crystalline Silicon

• Multicrystalline Si
• Sliced from blocks of cast silicon
• Cell efficiency 18
• Module effic. 14

12
Crystalline Silicon

• Edge-defined film-fed growth ribbons
• Nearly single crystal
• Grown from crucible of molten silicon
• Via capillary action
• Dendritic web
• Single crystal film
• Pulled from crucible of molten silicon
• Between two crystal dendrites

13
Gallium Arsenide

• Semiconductor material
• Often used in space power and concentrator
  systems
• Research cells 25 under 1 sun, 28 con.
• Multijunction cells have exceeded 30

14
Amorphous Silicon

• Non-crystalline form of silicon
• Research modules have 10 efficiency
• Comm. effic 5-7
• Consumer Products

15
Cadmium Telluride (CdTe)

• Thin-film polycrystalline
• Electrodeposition, spraying and high rate of
  evaporation
• Research cells 17
• Commercial modules 7-8

16
Copper Indium Diselenide (CIS)

• Thin-film polycrystalline
• Research cells 18
• Prototype modules 10
• Formation of defects during deposition

17
Concentrators

• Usually silicon
• 10x to 500x
• Fresnel lenses
• Module effic. to 17
• Design effic. gt 30
• Tracking, reflectors

18
PV Applications

• Remote Residential
• Village Power
• General Stand-Alone
• Pumping
• Cathodic Protection
• Communications
• Lighting and Refrig.
• Building Integrated

19
PV Applications

• Building Integrated
• Promise of extensive market penetration
• Replacing conventional façade or roofing
  materials
• Avoiding cost of support structures
• Roof, eyebrows, glass on glass, skylights, view
  walls, and curtain walls

20
PV BoS

• Balance of System
• Represents all components and costs other than
  the PV modules. It includes design costs, land,
  site preparation, system installation, support
  structures, power conditioning, operation and
  maintenance costs, indirect storage, and related
  costs. Big items are
• Inverter (if needed)
• Installation
• Mounting hardware
• Wiring (conduit)
• Batteries (if needed)

21
PV Standards

• ASTM 22 standards
• http//www.astm.org/
• IEEE 10 standards
• http//standards.ieee.org/
• ANSI / IEC 19 standards
• http//www.iec.ch/
• Other NEC (1), UL (2), PVGAP ISO
• http//www.pvpower.com/pvstds.html

22
PV Industry

• Many manufacturers
• http//www.pvpower.com/pvcos.html
• Modules, Inverters, BOS hardware

23
Steps in Sizing a System

• Determine available resource
• Determine load characteristics
• Establish key design criteria
• Reliability

24
Sizing PV Systems

• The solar resources in the US for flat plate
  photovoltaic system applications

25
Design of A Sustainable Power System

• Photovoltaics
• Terminology
• Rules of Thumb
• Solar Irradiance Data
• Site Selection Criteria
• Performance Design Criteria
• Series Strings
• Design Example

26
Terminology

• Cell smallest component of a PV system
• Module collection of cells, wired and arranged
  to provide building block of voltage and current
  and protected from elements
• Array grouping of modules and the wiring to
  interconnect them to achieve overall desired
  system voltage
• PV System types grid interconnected or
  stand-alone (demand or energy storage)

27
Design Rules of Thumb

• PV (highest loss is module efficiency 85)
• Inverter Losses (10-15)
• Array Orientation
• Remember Aesthetics over Optimal Orienting
• Due East or West vs. South (14 loss)
• Azimuth Off by /-20 (2 loss)
• Collectors Flat vs. Optimal (10 loss)
• Wiring Loss (2-5)

28
Solar Irradiance Data

• National Renewable Energy Laboratory
• http//rredc.nrel.gov/solar/old_data/nsrdb/blueboo
  k/state.html
• Solar Data for all 50 US states, many cities
• Pick a city, open the database and save as a text
  file (.txt)
• Open with Excel
• Save as tab delimited file type / Tab and Comma
  delimiters, then save as an Excel file

29
Site Selection Criteria

• South orientation
• No shading from 9a.m. to 4 p.m.
• Use Solar Pathfinder to check orientation and
  shading
• Adjust for magnetic declination
• Minimize wire run from PV to inverter

30
Overall System Performance

• Yearly kWh of PV System
• Total Energy Available from Sun (NREL data) for
  your location, tilt angle and azimuth
• X size of PV Array in total kW
• X efficiency of inverter
• X efficiency of DC wiring

31
Example Atlantic City,NJ

• Solar Resource 4. 6 kWh/m2/day
• Assume 2.4 kW PV Array
• PV System Performance
• 4.6 X 365 days/year X 2.4 X 90 X 98
• 3,544.1 kWh per year

32
PV Cells / Modules

• PV Cells produce 0.5 V and up to 6 amps
• Modules are groupings of cells
• Typically 12-15 Volts
• Varying amperes depending on manufacturer
• Module Specifications
• Voc open circuit voltage (no load)
• V Nominal (nameplate) operating voltage
• Isc Short circuit current (amps to -, no
  load)
• I operating current (amps measured under load)

33
Series String Design

• Series strings increase voltage
• Parallel strings increase current (amps)
• Never let one cell in a module be shaded during
  best sun-hours of day (no current)
• In arrays employ fuses and diodes
• Diode prevent current flow to shaded module
• Fuses prevent strings back-feeding one (fire)

34
Series String Design (grid)

• One path for current flow
• Design your series string so that the nominal
  voltage of the array is in the inverters power
  tracking window
• Assure your array open circuit voltage does not
  exceed inverters maximum voltage rating

35
Design Example 1

• How many Siemens 65W PV modules do you need in
  series to get the best voltage for a GC1000
  inverter?
• Siemens SP65 PV modules
• Vp 16.5 V (maximum operating under load)
• Voc 21.4 (voltage with no load)
• GC1000 Inverter
• Maximum Power Tracking Window 52-92 V
• Max V 92

36
Design Example 1

• Series voltage of modules needs to stay in design
  window therefore
• 16.5 X Number of panels must be gt52V but lt92V
• N 52 ?16.5 3.15
• Therefore 3 is not enough (only 49.5V)
• 4 is OK since 66V is in range
• 5 is OK since 82.5 is in range
• 6 is too many 99V gt 92V
• Check Max Voc for 4 (4 X 21.4 85.6 lt 92V) OK
• Check Max Voc for 5 (5 X 21.4 107 gt 92V) NO

37
How Many Strings?

• Each String of 4 Yields
• 65 x 4 watts 260 watts
• Inverter Capacity
• 1000 watts / 260 3.846 strings
• Must use 3 strings
• Short Circuit current 3 x 4.5 13.5 (lt25A)
• System Size 780 watts

38
Energy Produced

• PV System Performance
• 4.6 X 365 days/year X 0.78 X 90 X 98
• 1,155 kWh per year
• Is this is good match of modules and inverter?
• How might we make it better?

39
Inverters and Interconnection

• Inverters convert DC to AC power
• Utility frequency standard is /- 0.5 Hz
• Utility voltage is variable 108-132 V AC
• Inverters must follow utility sine wave
• Inverters must shut off to prevent islanding
• Inverters must meet technical standards in order
  to interconnect with local utility

40
Utility Interconnection

• Systems must meet
• IEEE 929-2000 standards
• UL Publication 1741 Standards (Power Conditioning
  Units for Use in Residential Photovoltaic
  Systems)
• Applications to local utilities must be filed by
  the customer and approved by the utility

41
Typical Utility Requirements

• All installations must
• Comply with National Electrical Code
• Be inspected for NEC compliance
• Receive all required permits
• Complete Interconnection Application
• Net Metering available up to 100 kW

42
Utility Interconnected PV System Configuration
43
PV Economics

• NJCEP Rebates
• Solar Electric Systems2003
• Incentive Level Systems up to 10kW - 5.50/watt
• Maximum incentive as percentageof eligible
  system costs
• 70
• Systems greater than 10kW
• 1 to 10 kW - 5.50/watt
• gt 10 to 100 kW4.00/watt
• gt 100 to 500 kW3.75/watt
• gt 500 to 1,000 kW0.30/watt
• Maximum incentive as percentageof eligible
  system costs
• 60
• http//www.njcep.com/html/2_incent.html

44
PV Economics -2

• NJBPU Solar Renewable Energy Credits
• Solar Electric Systems 2004 and Beyond
• Utility Payment Level
• from 0 30 cents/kWh generated