Solar Power &
Energy Independence
By Jamie Newton
Overview
• Solar Energy Potential
• Non-Electric Solar Power
– Technologies
– Implications for Energy Independence
• Solar Generated Electricity
– Technologies
– Distribution Approaches
– Implications for Energy Independence
Solar Energy Potential
• As of February 2006, Photovoltaic technology
accounted for less than 1% of worldwide
electricity generation.
• The amount of solar energy that reaches the
Earth’s surface every hour is greater than
humankind’s total demand for energy in one
year
Non-Electric Solar Power
Solar Water Heating
Passive Solar Heating/Lighting
Solar Water Heating
Solar Water Heating
• Advantages
– Replacing or supplementing
other water heating
methods: natural gas,
electricity
• Disadvantages
– More expensive in cooler
climates
Passive Solar Heating/Cooling
• Passive solar heating
can use overhangs to
shield the home from
the sun in the
summer, and warm
the home when the
sun is lower in the
winter sky
Solar Heating/Cooling
Non-Electric Solar Power &
Energy Independence
• Lowered Energy Consumption
• Broadening of Energy Portfolio
• Reduced Need for Fossil Fuel Imports
Solar Generated Electricity
Concentrating Solar Power
Photovoltaic (PV) Cells
Concentrating Solar Power
• Require Direct Sunlight
– Concentrating solar
power systems cannot
reflect diffuse sunlight,
making them ineffective
in cloudy conditions
• Two Approaches
– Power Tower
– Parabolic Trough
-Direct normal solar resource in the Southwest.
Image courtesy of “Tackling Climate Change In
the US: Potential Carbon Emissions Reductions
from Energy Efficiency and Renewable Energy by
2030” (Charles F. Kutcher ed.). Darker colors
signify greater solar radiance.
CSP Potential
State
Available Area
Capacity (MW)
Arizona
19,200
2,467,700
California
6,900
877,200
Colorado
2,100
271,900
Nevada
5,600
715,400
New Mexico
15,200
1,940,000
Texas
1,200
148,700
Utah
3,600
456,100
Total
53,900
6,877,000
- Direct normal solar resource in the Southwest, filtered
by resource, land use, and topology. Image courtesy of
“Tackling Climate Change In the US: Potential Carbon
Emissions Reductions from Energy Efficiency and
Renewable Energy by 2030” (Charles F. Kutcher ed.)
Existing US Generation Capacity (2003) = 1,000 GW
Total Potential CSP Generation in Southwest = 7,000 GW
Power Tower
• Solar One (CA)
– Steam Heat Transfer
– 10 MW
• Solar Two (CA)
– Molten Salt Heat Transfer
– 10 MW
• Solar Tres (Spain)
– Molten Salt Heat Transfer
– 15 MW
Solar Two
Parabolic Trough
• Sunlight focused on heat transfer fluid
(HTF), which then runs steam turbine
Parabolic Trough Generating Plant
Image of parabolic trough power plant in Kramer Junction, CA, which supplies power for the greater
Los Angeles area. This plant, in conjunction 4 other parabolic trough plants in California, can
produce as much as 354MW of electricity.
Photovoltaic Cells
Photovoltaic Potential
• “The basic resource potential for solar PV
in the United States is virtually unlimited
compared to any foreseeable demand for
energy.”
– Paul Denholm, Robert Margolis, & Ken Zweibel, “Potential Carbon
Emissions Reductions from Solar Photovoltaics by 2030,” in Tackling
Climate Change In The US: Potential Carbon Emissions Reductions
From Energy Efficiency And Renewable Energy By 2030, p.99 (Charles
F. Kutcher, ed., 2007)
• PV is flexible enough that it can be adapted for use in many areas.
Photoelectric Effect
• Basic process by which a
photovoltaic cell converts
absorbed sunlight into
electricity
• “Photons” knock
electrons free from the
silicon structure, freeing
them to enter electric
current and power a
“load” (like a light bulb)
Solar Generated Electricity
Distribution Approaches
• Centralized (CSP)
– Advantages and Disadvantages
• Distributed (PV Roof Installations)
– Advantages and Disadvantages
– Distributed PV Generation & Energy
Independence
Centralized
• Advantages
– Traditional model of
distribution
– No fuel costs
This PV Array is part of the
Sacramento Municipal Utility
District, generating 3.2 MW,
enough for 2,200 homes.
• Disadvantages
– Non-Constant Power
– Vulnerability
Distributed Solar (PV)
• Advantages
– Net-metering
• Grid Storage
– Flexibility
– Reduced vulnerability to
terrorist attack
– Almost no maintenance
– Negligible environmental
impact
– Domestic Production (?)
• Disadvantages
– Cost
• Extensive Individual
Investment
• Low Conversion Efficiency
– CCR’s
– Intermittency
Net-Metering
• Peak generation from PV occurs during the day
• Net-metering allows users to “bank” electricity they
generate, and credit it against the electricity they use
– Most states won’t pay users if they generate more electricity than
they use, but they can “zero-out” their accounts
• As of 2007, net-metering is offered to some degree in 41
states and D.C.
– California, New York, Texas
– Net-metering is offered in Illinois by one or more individual
utilities
• EPAct of 2005 requires all states to offer net-metering by
2008
Grid-Connected PV
PV Flexibility
• Stand-Alone
– Water pumps
– Fans
• Battery Backup
– Isolated Areas
• Generator Backup
• Hybrid
– Remote applications
• Grid Connected
– Grid storage
• Utility Scale
– Easy & Quick to build
PV Applications
Reduced Vulnerability
• Roof-by-roof power generation makes it too
difficult for one strike to have a crippling effect
• Vulnerability of centralized generation was
illustrated in the August 2003 US blackout
– caused by a series of “tripped” generation facilities
and transmission lines
– Within the first 2 hours:
• 3 Coal Fired Power Plants
• 9 Nuclear Power Plants
• 5 Major Transmission Lines
– Estimated loss from the August 2003 blackout has
been placed at $5-6 billion.
Distributed Solar Power and
Energy Independence
• The ultimate in Energy Independence –
self-sufficiency
• Consumers becoming “producers”
PV Disadvantages
• Price
– Efficiency
• Community Associations – CCR’s
• Intermittency
Price
• Still not “price-competitive” with traditional sources of
electricity
– “If you don't include the environmental costs of coal-fired
electricity when comparing them with solar, it becomes very
difficult. [Saving money] is not what motivates me and if that's all
that motivates the consumer, then perhaps solar isn't for them.”
• Dr. Richard Corkish, University of New South Wales, School of
Photovoltaic and Renewable Energy Engineering
• “Paying for Itself”
– Ability of a PV system to “pay for itself” depends on the size of
the installation, electricity demands it is meeting.
– Residential PV system may “pay for itself” within first half of its
estimated lifespan (30 years)
Price Reductions
Year
$/W (Goal)
Residential
Installation
Cost (2-4 kW)
2005
$8.50
$17,000-34,000
2010
$5.50
$11,000-$22,000
2015
$3.25
$6500-13,000
2030
$2.00
$4000-8,000
•Goals for DOE’s Solar America Initiative for cost reduction in PV Residential
(2-4kW) Systems:
•2015 = 10-12 cents/kWh
•2030 = 6-8 cents/kWh
•$148M in 2007 Funding for Solar America Initiative to spark R&D
Efficiency
• Conversion Efficiency – the percentage of
solar energy shining on a device that is
converted into electrical energy
• Typical Efficiencies
– Single Crystalline Silicon = 14%
– Thin Film = 7%
CCRs
• As of 1999, 42 Million Americans lived in
community associations
• Many of these communities seek to establish
aesthetic uniformity, protecting homeowner and
developer investment and lessening the risk of
undesirable activities in the community
• The Declaration of Conditions, Covenants, and
Restrictions are one method used to ensure that
homes retain a common design theme w/in a
community
Typical CCR Provisions Restricting
Solar Systems
• Prior Approval of
Architectural Committee
• Explicit Restrictions on
Placement of Solar
Equipment
• Height Restrictions
• Restrictions on secondary
buildings or structures
• Requirements that utilities
be screened
• Restrictions on the
placement of
improvements
• Specifications regarding
roofing materials
• Restrictions pertaining to
architectural style
Architectural Restrictions
• Arizona HOA is battling
resident over black solar
collector which doesn’t
match his light-brown roof
• Some state laws have
attempted to limit the ability
of CCRs to restrict solar
improvements
Intermittency
• Obviously, solar power requires sunlight to
generate power
• This means that:
– No power is can be generated at night
– Power generation may be reduced by cloud cover
• However, PV will still work with overcast skies
– Generation techniques requiring direct sunlight (CSP)
are ineffective w/o optimum conditions
• Solutions:
– Generators, Batteries, Hybrid Facilities
– Hydrogen
Hydrogen
• Hydrogen can be used as an energy carrier
• Hydrogen can be created from water through a
process called “electrolysis”
– DC current is used to split water into hydrogen and
oxygen
• Energy from renewable sources, like solar
power, can be used to manufacture hydrogen
• Commercial feasibility of solar generated
hydrogen is far off
Solar Power and Energy
Independence
• Lessen Reliance on Fossil Fuel
• Stabilize Energy Costs
• Re-conceptualize Distribution of Energy
– End-user production
– Distributed system lessens large-scale
vulnerability
• Production Method for Hydrogen Economy