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 HeatingPassive 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 PowerPhotovoltaic (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

Existing US Generation Capacity (2003) = 1,000 GW

Total Potential CSP Generation in Southwest = 7,000 GW

- 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.)

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

• Disadvantages– Non-Constant Power– Vulnerability

This PV Array is part of the Sacramento Municipal Utility District, generating 3.2 MW, enough for 2,200 homes.

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 ReductionsYear $/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