Advanced Power Systems

1
Advanced Power Systems

• ECE 0909.402-01, 0909.504-01
• Lecture 8 Wind, Solar Power Basics
• 28 March 2005
• Dr. Peter Mark Jansson PP PE
• Associate Professor Electrical and Computer
  Engineering

2
admin announcements

• 3-weeks until Final Project Reports due
• Mid-Term returned next week

3
See revised class schedule

• Posted on Web
• Final Presentation Dates
• 18 April, 25 April, 2 May, 9 May

4
New homework

• HW 7 due next Monday 4 Apr
• now posted on web
• 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.8, 7.17
• 8.1, 8.5, 8.6, 8.7

5
Aims of Todays Lecture

• Part One complete summary of ch. 6 concepts
• Wind-turbine Generators
• Overview of Chapter 7 Solar Resource
  Calculations
• break at 600 p.m.
• Part Two
• Complete Chapter 7
• Introduce Chapter 8 PV cells/module technology

6
Wind Power Classifications
7
Southern New Jersey Wind Map 50 m
Source http//www.awstruewind.com/inner/windmaps/
windmaps.htm
8
Wind Farms and Parks

• What are good engineering design standards for
  efficient power extraction from a windy site?
• Goals maximize power output, minimize downstream
  turbulence and inefficiencies, optimize overall
  site utilization (cost of equipment, power
  output, maintenance)

9
Wind Farm Optimization

• For farm output higher density is better
• For maintenance higher density is better
• For land costs higher density is better
• For wind turbulence lower density is better
• For turbine output lower density is better

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Wind Farm Rules of Thumb

• Recommended spacing
• Parallel to Pre-Dominant Wind Front
• 3-5 Rotor Diameter Spacing
• Next Row(s) Behind Frontline
• 5-9 Rotor Diameter Spacing
• Stagger alternate rows downwind between upwind
  turbine shadows

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Wind Farm Example

• Suppose a wind farm has a 4 rotor diameter
  spacing along its front row and 7 rotor diameter
  spacing between rows. Assume 78 array
  efficiency and turbine efficiency of 32.
• Find the annual production per acre for 400W/m2
  winds at hub height (the edge of 50m, Class 4
  winds)
• If the farmer leases the land for 100/acre-year
  (which is 10x what he makes on cattle) what is
  the lease cost per kWh?

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Wind Farm Solution

• Find the annual production per acre for 400W/m2
  winds at hub height

13
Wind Farm Solution

• If the farmer leases the land for 100/acre-year
  (which is 10x revenue on cattle) what is the
  lease cost per kWh?

14
LM 1

• What is the production potential (kWh/acre) of a
  Class 3 wind site (assume 350 W/m2) in the
  Delaware Bay at 50-m hub height?
• Assume 4 x 7 spacing, 80 array efficiency and
  30 turbine efficiency.
• If the State of NJ offers 200/year leases to
  offshore developers how much would these leases
  add to production costs (per kWh)?

15
LM 2

• What is the production potential (kWh/acre) of a
  Class 4 and 5 wind sites (assume 450 and 550 W/m2
  respectively) in the Delaware Bay at 50-m hub
  height?
• Assume 4 x 7 spacing, 80 array efficiency and
  30 turbine efficiency.
• How do Classes 3, 4 and 5 compare with each
  other?

16
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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Plancks and Stefan-Boltzmann Laws
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Wiens Displacement Rule
?max wavelength at which the spectrum reaches
its maximum point
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What is peak wavelength of Sun?
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What is peak wavelength of Earth?
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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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LM 3

• What are peak radiation wavelengths from the
  Moons dark side (assume -35o C) and from its
  bright side (assume 45o C)?

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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
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

28
LM 4

• Today is 28 March (n87), if we wanted to
  optimize our collection of solar radiation today
  what tilt angle would we have used on our modules
  here in Glassboro?
• Assume latitude 39.7o

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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
32
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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LM 5

• Find the altitude angle and azimuth angle for the
  sun at 300pm solar time in Boulder CO (latitude
  40o) on the day of the summer solstice
• L 40, H -45, ? 23.45

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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

36
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

40
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)

42
LM 6

• Using Table 7.8 on page 426, determine the June
  monthly production of a 20 efficient PV system
  with only 25 loss of sun due to cloudy weather
  under the following conditions
• 20 m2 w/ single axis tracker
• 20 m2 south facing at 20o tilt angle
• 20 m2 laying flat on a horizontal roof

43
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

44
Key Concepts of Chapter 8

• Photovoltaic history
• PV technologies materials
• Semiconductor physics
• Generic PV cell IV Curves
• From Cells ? Modules ? Arrays
• Series and Parallel configurations

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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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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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LM 7

• Estimate Cell temperature, open circuit voltage,
  and maximum power output for a 150-watt BP2150S
  module (see Table 8.3, p. 475) under conditions
  of 1 sun (1 kW/m2) and ambient temperature of 30
  oC, NOCT for module is 47 oC
• At 25 C Voc 42.8

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New homework

• HW 7 due next Monday 4 Apr
• now posted on web
• 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.8, 7.17
• 8.1, 8.5, 8.6, 8.7