Photovoltaic & Solar Energy Planning & Operating Electricty Network with Renewable Generation-2

1. Planning & Operating
Electricity Network with
Renewable Generation

2. 2.Photovoltaic systems and solar energy

3. What’s wrong with this picture?
• Pollution from burning fossil fuels leads to an increase in
greenhouse gases, acid rain, and the degradation of
public health.
 In 2005, the U.S.
emitted 2,513,609
metric tons of carbon
dioxide, 10,340 metric
tons of sulfur dioxide,
and 3,961 metric tons
of nitrogen oxides from
its power plants.

4. 40%
85% of our energy consumption
is from fossil fuels!

5. Why Sustainable Energy Matters
• The world’s current energy system
is built around fossil fuels
– Problems:
• Fossil fuel reserves are
ultimately finite
• Two-thirds of the world' s
proven oil reserves are locating
in the Middle-East and North
Africa (which can lead to
political and economic
instability)

6. Why Sustainable Energy Matters
• Detrimental environmental impacts
– Extraction (mining operations)
– Combustion
» Global warming (could lead to significant changes
in the world' s climate system, leading to a rise in
sea level and disruption of agriculture and
ecosystems)

7. Making the Change to Renewable Energy
• Solar
• Geothermal
• Wind
• Hydroelectric

8. Today’s Solar Picture
Financial Incentives
– Investment subsidies: cost of
installation of a system is
subsidized
– Net metering: the electricity
utility buys PV electricity
from the producer under a
multiyear contract at a
guaranteed rate
– Renewable Energy
Certificates ("RECs")

9. Terminology
• Voltage
– Measured in Volts
– Electrical potential
– “Height” of water on one side of a dam compared
to the other side
• Current
– Measured in Amps
– Rate of electron flow
– “Speed” at which water flows through the dam

10. Terminology
• Resistance
– The opposition of a material to the flow of an
electrical current
– Depends on
• Material
• Cross sectional area
• Length
• Temperature

11. Types of Current
• DC = Direct Current
– PV panels produce DC
– Batteries store DC
• AC = Alternating Current
– Utility power
– Most consumer appliances
use AC
– Electric charge changes
direction

12. Terminology
• Watt
– Measure of Power
– Rate of electrical energy
– Not to be confused with
Current!

13. Typical Wattage Requirements
Appliance Wattage
Blender 350
TV (25 inch) 130
Washer 1450
Sunfrost Refrigerator (7 hours a
day)
refrigerator/freezer (13 hours a
day)
112
475
Hair Dryer 1000
Microwave (.5 sq-ft)
Microwave (.8 – 1 sq-ft)
750
1400

14. Terminology
• Watt-hour (Wh) is a measure of energy
– Unit quantity of electrical energy (consumption
and production)
– Watts x hours = Watt-hours
• 1 Kilowatt-hour (kWh) = 1000 Wh

15. Grid-Tied System
• Advantages
– Easy to install
(less components)
– Grid can supply power
• Disadvantages
– No power if grid goes
down

16. Solar Modules

17. Solar Domestic Hot Water

19. Photovoltaic (PV) Hierarchy
• Cell < Module < Panel < Array

20. Why solar energy?
 Environmental concerns/reduce carbon
emissions
 Save money on electric bills
 General interest in new technologies
 Increase in home value

21. How can you use solar in your home or
business?
 Electricity from Solar
 Solar photovoltaics (PV)
 Heat from Solar
 Passive solar
 Solar thermal/hot water
 Solar air heater

22. Solar photovoltaics
(solar PV)
A solar PV system generally consists of
photovoltaic modules (aka "solar
panels") installed as an array (series of
panels) on a rooftop to generate
electricity to be used by the home or
business.

23. How a solar PV
array captures
the sun’s rays
and delivers
energy to a home
Diagram courtesy NW SEED

24. Solar PV installation overview
 Solar vocabulary
 Issues to consider
 Determining system size
 Solar incentives in Washington
 Costs and benefits

25. Solar vocabulary
 A kilowatt (kW) is an instantaneous measure of power.
(1000 watts = 1kw)
 A kilowatt-hour (kWh) is a unit of energy
 Equivalent to one kilowatt (1 kW) of power expended for one hour
(e.g. Ten 100 watt light bulbs burning for 1 hour)
 1 kW of PV produces about 1,100 kWh/yr in Western
Washington, 1,300 in Eastern Washington
 Average home uses about 9,000 kWh/yr

26. Solar vocabulary, cont.
Module or Panel is a solar photovoltaic panel.
Array is a series of solar panels installed together to
generate electricity.
Inverter converts DC electricity to AC electricity.
Racking connects the solar panels to the roof.
Production Meter measures the amount of kwh generated
by a solar system.
Production Incentive is money that the State will pay for
each kwh generated by solar panels.
Net Metering is a utility program letting solar homeowners
bank unused kwh for future use.

27. Considerations with Solar PV
 Trees or other shade that will fall on the PV array
 Roof considerations: Which direction does your roof face? Is
your roof in good shape? Roof space? Roof tilt?
 Other variables such as structural issues, roof access, other roof
uses: antennas, chimneys, skylights.
 Do you have a Homeowner’s Association? Do they have
requirements for solar installations?
 Utility net-metering policy.

28. Determining system size
 Your goals for electric bill offset
 Roof space available for PV
 Roof shading / orientation / pitch
 Depends on your budget or your investment goals
 Complexity of installation will impact budget

29. Solar incentives (PV)
 Federal 30% tax credit
 Systems must be placed in service before December 31, 2016
 State sales tax exemption
 For solar PV systems of 10kW or less; expires June 30, 2018.
 WA State Production Incentives
 Provides PV system owners with a payment of $0.15 to $0.54 per kilowatt-hour of solar energy
produced Non-WA equipment: $0.15; WA inverter only: $0.18; WA modules only: $0.36; WA
inverter + WA modules:$0.54. Payments will be made until June 30, 2020. Maximum of $5000 per
year.
 Localized incentives
 Check with your local PUD or Utility for additional incentives.
 Net metering (100kw system size limit); does not expire
 Federal Modified Accelerated Cost-Recovery System (aka
accelerated depreciation); only for businesses, not residences

30. Sample PV Costs:
Made-in-WA equipment
Based on a 6 KW system (@ $5/watt): $30,000
30% Federal Tax Credit: $9,000
Start-up Cost: $21,000
Production Incentive over 5 years: $17,820
Net Metering Credit value over 25 years: $14,520
25 year net: $11,340
Not including increased home resale value or rise in electric prices!

31. Sample PV Installation Costs:
Not Made-in-WA equipment
Based on a 6 KW System (@ $4.25/watt): $25,500
30% Federal Tax Credit: $7,650
Start-up Cost: $17,850
Production Incentive over 5 years: $4,950
Net Metering Credit value over 25 years: $14,520
25 year net: $1,620
Not including increased home resale value or rise in electric prices!

32. Other benefits of Solar PV
 Increased home values
 Longer warranties
 No moving parts
 Low maintenance (Inverter replacement)
 Unlimited resource / free fuel (the sun!)
 Creates local jobs
 Low interest loans are available

33. Check with your local utility & city
– Depending on where you live in state, your utility
may have its own, unique interconnection and net
metering requirements and policies.
– Check with your utility and jurisdiction and ask
about the following:
• Interconnection and permitting processes
• Net metering hook up and process
• If your utility participates in the state production incentive
program

34. Going ahead with a PV installation
 Get quotes from installers
 Installers will do a site assessment and take care of getting permits, etc.
 Check your utility’s web site for a list of qualified installers in your area
 Loans
 Check your bank or credit union to see if they offer loans

35. Other considerations to stretch your
electricity further
 Reduce power consumption (turn off lights, etc.)
 Keep PV solar system shade free
 Simple maintenance such as hosing off panels once or twice per year;
otherwise a solar PV system should operate effectively
 Should your house be more efficient?
 Check with your local utility for energy efficiency programs (incentives/ rebates/
low interest loans).
 Efficiency can make solar go further!

36. Additional uses of solar
 Heat from Solar
 Passive solar
 Solar thermal/hot water
 Solar air heater

37. Heat from Solar:
Passive solar
Building a structure that collects
heat from the sun and retains it in
materials that store heat, known
as thermal mass.
Solar heat is transferred from
where it is collected and stored to
different areas of the structure by
conduction, convection, radiation
and even small fans and blowers.

38. Heat from Solar:
Solar thermal/hot water
Used to heat residential, commercial
or industrial water supplies as well as
space heating and pools.
A collector - typically fastened to a
roof or a wall facing the sun – is used
to heat an anti-freeze solution that is
either pumped (active system) or
driven by natural convection (passive
system) through it.

39. Heat from Solar:
Solar air heater
Energy from the sun is captured by an
absorbing medium and used to heat
air.
Works like a greenhouse by
circulating air from inside a home
through the system mounted on the
exterior wall.

40. Other ways to participate in solar
 Community
Solar
Seattle Aquarium/Seattle City Light

41. What is Solar Energy?
• Originates with the
thermonuclear fusion
reactions occurring in the sun.
• Represents the entire
electromagnetic radiation
(visible light, infrared,
ultraviolet, x-rays, and radio
waves).
• Radiant energy from the sun
has powered life on Earth for
many millions of years.

42. Advantages and Disadvantages
• Advantages
• All chemical and radioactive polluting byproducts of the
thermonuclear reactions remain behind on the sun, while only
pure radiant energy reaches the Earth.
• Energy reaching the earth is incredible. By one calculation, 30
days of sunshine striking the Earth have the energy equivalent of
the total of all the planet’s fossil fuels, both used and unused!
• Disadvantages
• Sun does not shine consistently.
• Solar energy is a diffuse source. To harness it, we must
concentrate it into an amount and form that we can use, such as
heat and electricity.
• Addressed by approaching the problem through:
1) collection, 2) conversion, 3) storage.

43. Solar Energy to Heat Living Spaces
 Proper design of a building is for it to act as a solar
collector and storage unit. This is achieved through
three elements: insulation, collection, and storage.

44. Solar Energy to Heat Water
• A flat-plate collector is used
to absorb the sun’s energy to
heat the water.
• The water circulates
throughout the closed
system due to convection
currents.
• Tanks of hot water are used
as storage.

45. Photovoltaics
Photo+voltaic = convert light to electricity

46. Solar Cells Background
• 1839 - French physicist A. E. Becquerel first recognized the photovoltaic
effect.
• 1883 - first solar cell built, by Charles Fritts, coated semiconductor
selenium with an extremely thin layer of gold to form the junctions.
• 1954 - Bell Laboratories, experimenting with semiconductors,
accidentally found that silicon doped with certain impurities was very
sensitive to light. Daryl Chapin, Calvin Fuller and Gerald Pearson,
invented the first practical device for converting sunlight into useful
electrical power. Resulted in the production of the first practical solar
cells with a sunlight energy conversion efficiency of around 6%.
• 1958 - First spacecraft to use solar panels was US satellite Vanguard 1
http://en.wikipedia.org/wiki/Solar_cell

47. Driven by Space Applications in
Early Days

48. The heart of a photovoltaic system is a solid-state device called a solar cell.
How does it work

49. How Solar Cells Work
 Photons in sunlight hit the solar panel and are absorbed by semiconducting materials
to create electron hole pairs.
 Electrons (negatively charged) are knocked loose from their atoms, allowing them to
flow through the material to produce electricity.
p n
- +
- +
- +
- +
- +
hv > Eg

50. Cost/Efficiency of Photovoltaic Technology
Costs are modules per peak W; $0.35-$1.5/kW-hr

51. Cost of Photovoltaic Technology
• Globally, onshore wind schemes are now costing an
average of $0.06 per kilowatt hour (kWh), although
some schemes are coming in at $0.04 per KwH, while
the cost of solar PV is down to $0.10 per KwH.
• o calculate $/W, take the total out-of-pocket cost of
the system that you are considering and divide
it by the number of watts of capacity in the
system. Forexample, a 5kW solar system has 5000
watts. If that system costs $15,000, then the cost
per watt is ($15,000 / 5000W =) $3/W

52. 89.6% of 2007 Production
45.2% Single Crystal Si
42.2% Multi-crystal SI
• Limit efficiency 31%
• Single crystal silicon - 16-19%
efficiency
• Multi-crystal silicon - 14-15%
efficiency
• Best efficiency by SunPower Inc 22%
Silicon Cell Average Efficiency
First Generation
– Single Junction Silicon Cells

53. CdTe 4.7% & CIGS 0.5% of 2007 Production
• New materials and processes to improve efficiency
and reduce cost.
• Thin film cells use about 1% of the expensive
semiconductors compared to First Generation
cells.
• CdTe – 8 – 11% efficiency (18%
demonstrated)
• CIGS – 7-11% efficiency (20% demonstrated)
Second Generation
– Thin Film Cells

54. • Enhance poor electrical performance while maintaining very low
production costs.
• Current research is targeting conversion efficiencies of 30-60% while
retaining low cost materials and manufacturing techniques.
• Multi-junction cells – 30% efficiency (40-43% demonstrated)
Third Generation
– Multi-junction Cells

55. Solar Home Systems
Space
Water
Pumping
Telecom
Main Application Areas – Off-grid

56. Residential Home
Systems (2-8 kW)
PV Power Plants
( > 100 kW)
Commercial Building
Systems (50 kW)
Main Application Areas
Grid Connected

57. Renewable Energy Consumption
in the US Energy Supply, 2007
http://www.eia.doe.gov/cneaf/solar.renewables/page/trends/highlight1.html

58. Top 10 PV Cell Producers
Top 10 produce 53% of world
total
Q-Cells, SolarWorld - Germany
Sharp, Kyocera, Sharp, Sanyo –
Japan
Suntech, Yingli, JA Solar – China
Motech - Taiwan

59. (in the U.S. in 2002)
1-4
¢
2.3-5.0 ¢ 6-8
¢
5-7
¢
Production Cost of Electricity
0
5
10
15
20
25
Coal Gas Oil Wind Nuclear Solar
Cost
6-7
¢
25-50 ¢

60. Future Generation
– Printable Cells
Organic Cell
Nanostructured Cell
Solution Processible Semiconductor

61. Conversion Efficiency

62. PV Array
Components
oPV Cells
oModules
oArrays

63. PV System Components

64. NET METERING

65. PV Array Fields

66. Source: Solarbuzz, a part of The NPD Group

67. • Clean
• Sustainable
• Free
• Provide electricity to remote
places
ADVANTAGES OF SOLAR ENERGY

68. Disadvantages of Solar Energy
• Less efficient and costly equipment
• Part Time
• Reliability Depends On Location
• Environmental Impact of PV Cell
Production

69. Selecting the Correct Module
• Practical Criteria
– Size
– Voltage
– Availability
– Warranty
– Mounting Characteristics
– Cost (per watt)

70. Current-Voltage (I-V) Curve

71. Effects of Temperature
• As the PV cell
temperature
increases above
25º C, the module
Vmp decreases by
approximately 0.5%
per degree C

72. Effects of Shading/Low Insolation
• As insolation
decreases
amperage
decreases while
voltage remains
roughly
constant

73. Shading on Modules
• Depends on orientation of internal module
circuitry relative to the orientation of the
shading.
• SHADING can half
or even completely
eliminate the output
of a solar array!

74. PV Wiring

76. Series Connections
• Loads/sources wired in series
– VOLTAGES ARE ADDITIVE
– CURRENT IS EQUAL

77. • Loads/sources wired in parallel:
– VOLTAGE REMAINS CONSTANT
– CURRENTS ARE ADDITIVE
Parallel Connections

78. Wiring Introduction
• Should wire in Parallel or
Series?

79. Wire Components
• Conductor material = copper (most common)
• Insulation material = thermoplastic (most common)
• Wire exposed to sunlight must be classed as sunlight
resistant

80. Color Coding of Wires
• Electrical wire insulation is color coded to designate its
function and use
Alternating Current (AC) Wiring Direct Current (DC) Wiring
Color Application Color Application
Black Ungrounded Hot Red (not NEC req.) Positive
White Grounded
Conductor
White Negative or
Grounded
Conductor
Green or Bare Equipment
Ground
Green or Bare Equipment
Ground
Red or any
other color
Ungrounded Hot

81. Solar Site & Mounting

82. Learning Objectives
• Understand azimuth and altitude
• Describe proper orientation and tilt angle for
solar collection
• Describe the concept of “solar window”
• Evaluate structural considerations
• Pros and cons of different mounting
techniques

83. Site Selection – Panel Direction
• Face true
south
• Correct for
magnetic
declination

84. Altitude and Azimuth

85. Solar Pathfinder
• An essential tool in finding a good site for
solar energy is the Solar Pathfinder
• Provides daily, monthly, and yearly solar
hours estimates

86. Site Selection – Tilt Angle
Year round tilt = latitude
Winter + 15 lat.
Summer – 15 lat.
Max performance is
achieved when panels
are perpendicular to the
sun’s rays

87. General Considerations
• Weather characteristics
– Wind intensity
– Estimated snowfall
• Site characteristics
– Corrosive salt water
– Animal interference
• Human factors
– Vandalism
– Theft protection
– Aesthetics

88. General Considerations Continued
• Loads and time of use
• Distance from power conditioning equipment
• Accessibility for maintenance
• Zoning codes

89. Basic Mounting Options
• Fixed
– Roof, ground, pole
• Integrated
• Tracking
– Pole (active & passive)

90. Pole Mount Considerations
• Ask manufacturer for wind loading
specification for your array
– Pole size
– Amount of concrete
– Etc.
• Array can be in close proximity to the house,
but doesn’t require roof penetrations

91. Tracking Considerations
• Can increase system performance by:
– 15% in winter months
– 30% in summer months
• Adds additional costs to the array

92. Passive Vs. Active
Active:
– Linear actuator motors
controlled by sensors
follow the sun
throughout the day

93. Passive Vs. Active
Passive:
– Have no motors,
controls, or gears
– Use the changing weight
of a gaseous refrigerant
within a sealed frame
member to track the sun

94. Roof Mount Considerations
• simple and cheap to
install
• offer no flexibility in
the orientation of
your solar panel
• can only support
small photovoltaic
units.

95. Roof Mount Considerations
• Penetrate the roof as little as possible
• Weather proof all holes to prevent leaks
– May require the aid of a professional roofer
• Re-roof before putting modules up
• Leave 4-6” airspace between roof and
modules
• On sloped roofs, fasten mounts to rafters
not decking

96. Building Integrated PV

97. Costs

98. Solar Energy System
 $10,000-$15,000 1 kW system
• $16,000-$20,000 2 kW system
• $35,000-$45,000 5 kW system
• About half the power for a conventional home

99. Solar Energy Incentives
• Tax credits and deductions
– 30% tax credit
• Local & state grant and loan programs
• PA Alternative Energy Investment Fund
– Pennsylvania Sunshine Program
• 35% rebate

100. Energy Efficiency

101. Learning Objectives
• Identify cost effective electrical load reduction
strategies
• List problematic loads for PV systems
• Describe penalties of PV system components
• Explain phantom loads
• Evaluate types of lighting; efficiency
comparison

102. 3. Renewable Energy
2. Efficiency
1. Conservation

103. Improving Energy Efficiency in the Home
• Space Heating:
– Insulation
– Passive solar design
– Wood stoves
– Propane
– Solar hot water
– Radiant Floor/ baseboard
– Efficient windows
• Domestic hot water heating
– Solar thermal
– Propane/natural gas
– On demand hot water

104. Improving Energy Efficiency in the Home
• Washing machines
– Energy efficient front loading
machine
• Cooling
– Ceiling fans
– Window shades
– Insulation
– Trees
– Reflective attic cover
– Attic fan

105. Phantom Loads

106. Phantom Loads
• Cost the United States:
– $3 Billion / year
– 10 power plants
– 18 million tons of CO2
– More pollution than 6 million cars
• TV’s and VCR’s alone cost the US $1
Billion/year in lost electricity

107. Lighting Efficiency
• Factors effecting light efficiency
– Type of light
– Positioning of lights
– Fixture design
– Color of ceilings and walls

108. Incandescent Lamps
• Advantages
– Most common
– Least expensive
– Pleasing light
• Disadvantages
– Low efficiency
– Short life ~ 750 hours
Electricity is conducted through a filament which resists
the flow of electricity, heats up, and glows
Efficiency increases as lamp wattage increases
FROM THE POWER PLANT TO YOUR HOME
INCANDESCENT BULBS ARE LESS THAN 2%
EFFICIENT

109. Fluorescent Bulbs
• Less wattage, same amount of lumens
• Longer life (~10,000 hours)
• May have difficulty starting in cold
environments
• Not good for lights that are repeatedly turned
on and off
• Contain a small amount of mercury

111. Light Emitting Diode (LED) Lights
• Advantages
– Extremely efficient
– Long life (100,000 hours)
– Rugged
– No radio frequency
interference
• Disadvantages
– Expensive (although prices
are decreasing steadily)
– A relatively new technology

112. Batteries

113. Grid-Tied System
• Advantages
– Low: Easy to install (less
components)
– Grid can supply power
• Disadvantages
– No power when grid
goes down

114. Learning Objectives
• Battery basics
• Battery functions
• Types of batteries
• Charging/discharging
• Depth of discharge
• Battery safety

115. Batteries in Series and Parallel
• Series connections
– Builds voltage
• Parallel connections
– Builds amp-hour capacity

116. Battery Basics
 Battery
 A device that stores electrical energy (chemical energy to
electrical energy and vice-versa)
 Capacity
 Amount of electrical energy the battery will contain
 State of Charge (SOC)
 Available battery capacity
 Depth of Discharge (DOD)
 Energy taken out of the battery
 Efficiency
 Energy out/Energy in (typically 80-85%)
The Terms:

117. Functions of a Battery
Storage for the night
Storage during cloudy weather
Portable power
Surge for starting motors
**Due to the expense and inherit inefficiencies of batteries it is
recommended that they only be used when absolutely necessary (i.e.
in remote locations or as battery backup for grid-tied applications if
power failures are common/lengthy)

118. Batteries: The Details
 Primary (single use)
 Secondary (recharged)
 Shallow Cycle (20% DOD)
 Deep Cycle (50-80% DOD)
Types:
 Unless lead-acid batteries are charged up to 100%, they will loose
capacity over time
 Batteries should be equalized on a regular basis
Charging/Discharging:

119. Battery Capacity
 Amps x Hours = Amp-hours (Ah)
Capacity:
100 amps for 1 hour
1 amp for 100 hours
20 amps for 5 hours
 Capacity changes with Discharge Rate
 The higher the discharge rate the lower the capacity and vice versa
 The higher the temperature the higher the percent of rated capacity
100 Amp-hours =

120. Rate of Charge or Discharge
Rate = C/T
C = Battery’s rated capacity (Amp-hours)
T = The cycle time period (hours)
Maximum recommend charge/discharge rate =
C/3 to C/5

121. Battery Safety
• Batteries are EXTREMELY DANGEROUS; handle with care!
– Keep batteries out of living space, and vent battery box to
the outside
– Use a spill containment vessel
– Don’t mix batteries (different types or old with new)
– Always disconnect batteries, and make sure tools have
insulated handles to prevent short circuiting

122. Grid-Tied System
(With Batteries)
• Complexity
– High: Due to the addition
of batteries
• Grid Interaction
– Grid still supplements
power
– When grid goes down
batteries supply power to
loads (aka battery backup)

123. Controllers & Inverters

124. Learning Objectives
• Controller basics
• Controller features
• Inverter basics
• Specifying an inverter

125. Controller Basics
• To protect batteries from being overcharged
Function:
 Maximum Power Point
Tracking
– Tracks the peak
power point of the
array (can improve
power production by
20%)!!
Features:

126. Additional Controller Features
• Voltage Stepdown Controller: compensates for differing voltages
between array and batteries (ex. 48V array charging 12V battery)
– By using a higher voltage array, smaller wire can be used from
the array to the batteries
• Temperature Compensation: adjusts the charging of batteries
according to ambient temperature

127. Other Controller Considerations
• When specifying a controller you must consider:
– DC input and output voltage
– Input and output current
– Any optional features you need
• Controller redundancy: On a stand-alone system it might be
desirable to have more then one controller per array in the event of
a failure

128. Inverter Basics
• An electronic device used to convert direct current (DC)
electricity into alternating current (AC) electricity
Function:
 Efficiency penalty
 Complexity (read: a component which can fail)
 Cost!!
Drawbacks:

129. Specifying an Inverter
• What type of system are you designing?
– Stand-alone
– Stand-alone with back-up source (generator)
– Grid-Tied (without batteries)
– Grid-Tied (with battery back-up)
• Specifics:
– AC Output (watts)
– Input voltage (based on modules and wiring)
– Output voltage (120V/240V residential)
– Input current (based on modules and wiring)
– Surge Capacity
– Efficiency
– Weather protection
– Metering/programming

130. Basic Science Issues in the Development
of Photovoltaics

131. Projected PV Installations and Revenues
 The PV industry has grown of over the last decade.
 However, 2009 looks to be tough year – iSuppli predicts a 32% decrease in PV
installations and a 12% decrease in prices in 2009.
 Lux Research believes average selling prices may fall > 25% in 2009.

132. Forecast for PV Electricity Production
 Sharp forecasts that PV will supply 10% of the world’s electricity by 2032
 Assuming a CAGR of 35% (average over the last few decades), the cumulative PV
production would be ~ 3.5 TWp by 2026.
 3 TWp of solar electricity will reduce carbon emissions by about 1 Gton per year
(7 Gtons of carbon were emitted as CO2 in 2000)

133. The Major Players
 Sharp
 Kyocera
 BP Solar
 Q-Cells
 Mitsubishi
 SolarWorld
 Sanyo
 Schott Solar
 Isofoton
 Motech
 Suntech
 Evergreen
Solar
 GE Energy
 United Solar
 Kaneka
 Fuji Electric
 Sharp
 Mitsubisihi
 Schott Solar
 AMAT
licensees
 SunTech
 PowerFilm
 OptiSolar
 EPV
 Avancis
 Showa Shell
 Wurth Solar
 DayStar
 Nanosolar
 First Solar
 Antec Solar
 AVA
 PrimeStar
Solar
Crystalline Si a-Si/µc-Si CIGS CdTe
 There are currently about 325
companies developing or
producing solar cells.
 Total PV production is
forecasted to be ~10 GWp in
2009, but demand may only be
~ 3.5 GWp (which can be met
by top 10 companies).

134. The Typical Silicon Solar Cell
 This device structure is used by most manufacturers today.
• The front contact is usually formed by POCl3 diffusion
• The rear contact is formed by firing screen-printed Al to form a back-surface field
 The cell efficiencies for screen-printed multicrystalline silicon cells are typically in the
range of 14 – 17%.

135. Research Needs for Photovoltaics
Lower Costs
 Efficiency improvements will help to lower costs of PV electricity
 Low-cost storage required for significant penetration of the grid (>
10%)
 In the case of silicon solar cells, there is a need for a high-quality,
thin silicon wafer or sheet (10 – 50 m) that can be produced at low
cost
 Automated high throughput process with intelligent process control
 We’ll need to replace silver contacts with lower cost materials such
as copper or carbon-based materials (nanotubes?)
• At an annual production of ~ 154 GWp (~ 2016), the PV industry would be using the entire annual
production of Ag (~ 19,000 tons/yr)
 Low-cost (i.e. abundant) materials must be incorporated into
reliable, high performance PV modules and systems (annual total
U.S. electricity demand is ~ 3 x 1012 kWh which can be met by PV
arrays with an area of 100 miles x 100 miles in the U.S. Southwest).

136. PV Experience Curve
Cost of Materials Limit (20% Modules)Cost of Materials Limit (20% Modules)Cost of Materials Limit (20% Modules)Cost of Materials Limit (20% Modules)Cost of Materials Limit (20% Modules)Cost of Materials Limit (20% Modules)
 PV module prices have followed an experience curve with a slope of ~ 80% (a 20%
decrease in price with every doubling of cumulative production).

137. Research Needs for Photovoltaics
Efficiency
 Efficiency is a major driver in reducing costs and meeting
energy requirements in limited areas
 Further efficiency improvements are possible with all PV
technologies

138. Research Needs for Photovoltaics
Environmental Issues
 Some photovoltaic materials are highly toxic and must
be processed with appropriate safeguards and
obsolete/damaged product should be recycled
 Research on new materials and devices should define
all potential hazards before commercialization
Sustainability
 Need to use materials that are plentiful - some PV
materials may be constrained by availability when
production reaches tens of GWp/yr; e.g. In
(byproduct of Zn refining), Se and Te (byproducts of Cu
refining)

139. Research Needs for Photovoltaics
Reliability
 Further reliabilty improvements are required in PV
systems (inverters, batteries, etc.)
 Encapsulation is necessary to protect contacts,
interconnects and some PV materials (crystalline
silicon PV modules are warranted for 25 years)
 Possible failure mechanisms must be identified for
new PV materials and devices
Diagnostics
 There is a need for rapid characterization of critical
parameters such as minority carrier lifetime,
efficiency of light trapping, junction quality, etc. for
quality control of production lines

140. Research Needs for Photovoltaics
Conclusions
 Many of us believe that photovoltaics could become the major
energy source for the world in the later part of this century, but
continued research and development are required in several areas:
 PV system costs must be reduced significantly
 Improved conversion efficiencies
 Long-term reliability must be ensured for new PV materials &
devices
 Future PV systems should be environmentally benign

141. 141
Discussion Questions
• Are PV systems as efficient or economic as
fossil-fueled systems?
• Is PV a viable alternative for all of our power
needs? For homes? For vehicles? For other
needs?
• Is PV the answer to all of the world’s power
needs?