• Know Your Rights

    Arizona law protects individual homeowners’ private property rights to solar access by dissolving any local covenant, restriction or condition attached to a property deed that restricts the use of solar energy. This law sustained a legal challenge in 2000. A Maricopa County Superior Court judge ruled in favor of homeowners in a lawsuit filed by their homeowners association seeking to Read more
  • Agua Caliente PV Power Plant Among World’s Largest

    The Agua Caliente solar farm near Yuma features First Solar’s thin-film cadmium-telluride (CdTe) solar modules. Located 65 miles east of the city of Yuma, Arizona, this plant is one of the world’s largest operational PV power plants with 290MW (AC) connected to the electricity grid. Read more
  • Solar Hot Water

    There are two types of solar water heating systems: active, which have circulating pumps and controls, and passive, which don't. The typical solar water heater is comprised of solar collectors and a well-insulated storage tank. The solar collector is a network of pipes that gathers the sun's energy, transforms its radiation into heat, and then transfers that heat to either Read more
  • Federal Residential Renewable Energy Tax Credit

    (Information provided by DSIRE - Last reviewed 02/19/2009) Incentive Type: Personal Tax Credit State: Federal Eligible Renewable/Other Technologies: Solar Water Heat, Photovoltaics, Wind, Fuel Cells, Geothermal Heat Pumps, Other Solar Electric Technologies Applicable Sectors: Residential Amount: 30% Maximum Incentive: Solar-electric systems placed in service before 2009: $2,000Solar-electric systems placed in service after 2008: no maximumSolar water heaters placed in service before Read more
  • Solar Building Design in Arizona

    The idea of using the sun to meet the energy needs in our buildings has been with us since the time of the Greeks, with some of the design manifestations even evident in the prehistoric structures of Arizona and the Southwest. There is a great historic tradition for Arizona buildings that utilize our most abundant resource, and the current increases Read more
  • How Not to- Battery Connections

    Photo shows the situation after a battery discharge test at 300 amps was terminated on a 1530 AH IBE battery string when one post melted. During the discharge test all cell voltages are logged. The sum of the cell voltages was 2.73 volts lower than the 48-volt string voltage. This is an average of 118 mv per inter-cell connection, 5-10 Read more
  • 1 Know Your Rights
  • 2 Agua Caliente PV Power Plant Among World’s Largest
  • 3 Solar Hot Water
  • 4 Federal Residential Renewable Energy Tax Credit
  • 5 Solar Building Design in Arizona
  • 6 How Not to- Battery Connections

Blogs

  1. Solar Center Blog
  2. Guest Blogs
Geoff Sutton
25 November 2017

In the desert south-west the intense sunshine and long summer days result in uncomfortable and even dangerously high temperatures for about four months.

Jim Arwood
28 December 2016

“A lie gets halfway around the world before the truth has a chance to get its pants on.”  --Winston Churchill


Will add Guest Blog content here
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Fri, Dec 15, 2017
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Some things to pay attention to in Arizona

ASEA REBOOT

The Arizona Solar Energy Association (ASEA), State Chapter of the American Solar Energy Society ASES), will be holding meetings in a follow-up to the-long awaited updated ASES‚  Chapters handbook and directives.

ASES evolution, in response to some problematic economic and operational conditions, has resulted in a hearty and robust context for the present and the future. ASEA is now responding with an appropriate updating, through local and statewide discussion. 

Interim Chair, Andy Gerl, a past ASEA Chair and Board member, is making arrangements for Arizona solar advocates and supporters, members and non-members, to receive both an update re: ASES adaptation and changes, and to discuss solar in Arizona and the “reboot" of the ASEA  context, goals and objectives, within the context of varied renewable energy groups within the State, such as AriSEIA (the solar trade association); various sustainability groups; Green Building organizations; the recently formed solar hot water businesses non-profit entity; research and development at the universities; and others.

For more information about the ASEA Reboot discussions, contact Andy at andrew@blazingsolar.com  or 602-799-5942

APS Rate Case - Higher rates, solar changes now effective as of September 1st

APS customers had until August 31st to submit complete interconnection applications to APS in order to be grandfathered under earlier solar policy.  Basic rates have increased and net metering was eliminated, replaced by a fixed purchase rate that starts at $0.129 per kwhr and will decrease in the future.  Further details are posted in a link below.

Quick APS Links:

News Release (Aug. 15, 2017)
Summary for Residential Customers
Summary for Business Customers
Solar Grandfathering Fact Sheet (also see the note below for additional information)

The Arizona Solar Center has put together an unofficial summary of the new APS rate schedules for new solar customers, click here.

On August 21st APS emailed the following information to Stakeholders (but it does not seem to be on the APS website):

Stakeholders,

The Arizona Corporation Commission (ACC) has approved a decision in our rate review, and we are happy to share some details with you affecting our solar customers. We appreciate your support in delivering this message to customers and will be glad to help you with any questions you may have. For your reference, attached are letters that were sent to customers regarding grandfathering. Other resources are available at aps.com/gosolar.

Grandfathering

  • Current solar customers that are interconnected to the APS grid will remain grandfathered for 20 years from the date of interconnection.
    • The grandfathering stays with the premise. Systems transferred to a new premise will require a new application, and the customer would no longer be eligible for EPR-6.
    • Over the terms of the grandfathering period, a customer may not increase the capacity of their grandfathered solar system by more than a total of 10% or 1 kW, whichever is greater.
  • Customers who submit a complete application by 11:59 p.m. August 31, 2017 will be eligible for grandfathering. The system would need to be installed and have AHJ approval by February 28, 2018 in order to qualify. A complete application includes all of the following:
    • Customer Application
    • Executed Contract
    • Disclaimer
    • Consumer Acknowledgement
    • Installer Application
    • Three Line Diagram
    • Site Plan

Public Meetings:

Green Building Lecture - Economic Value of Green: Knowledge is EmPOWERing

Scottsdale’s Green Building Lecture season kicks off with a panel of industry leaders on the economic value of green. 
 
These free programs run from 7 to 8:30 p.m. on the dates listed below at the Granite Reef Senior Center, 1700 N. Granite Reef Road. RSVPs are not needed.

Green Building Lecture Series

Solar Energy and Battery Storage Systems

Date: Thursday, Dec. 7

Time: 7 - 8:30 p.m.

This is an exciting time for renewables and on-site energy storage systems as solar continues to take off in the valley. Just this year, Scottsdale has had a record year with more than 500 residential solar electric installations and a growing number of battery storage system installs.  

ASU Senior Sustainability Scholar Paul Hirt will discuss the solar energy revolution, why solar is coming faster than anyone expected and how it will change our world. His current research includes a history of electric power, transition to renewable energy, and collaborative interdisciplinary research on water use, urban growth and sustainability.

Titan Solar Power Director of Business Development Jack Walker joins Hirt. He’ll discuss residential battery storage options for utility-connected solar photovoltaics systems. Walker is set to address homeowners’ concerns about time of use rates, controlling demand charges and having a backup system in the event of a utility grid failure. For some homeowners it’s about control over time of use rates, for others it may be about controlling demand charges while for others it may be about having a "back up" system in the event of utility grid failure.

For more information see the 'Next Lecture' section of this link: http://www.scottsdaleaz.gov/green-building-program

The  scheduled lecture series includes:

  • Feb. 1, 2018 – Living an Edible Landscape Life
  • April 5, 2018 – Building with earth and Mass in the Desert 
  • June 7, 2018 – Heating and Cooling with Ductless Mini-Splits

Further information on this worthwhile program

General News feed

Caution- News leads open in new windows. Warning- These news links are automatically generated by others such as Google News and are not reviewed by the Arizona Solar Center, Inc. We are not responsible for link content.

Our Twitter Feed

azsolarcenter "A lie gets halfway around the world before the truth has a chance to get its pants on.” --Winston... https://t.co/YZUiXLzsKz
azsolarcenter The Sun Day Blog: The future is not what it used to be. In the aftermath of the 2016 election, the question has... https://t.co/lSR5RFewJm
azsolarcenter Novermber 5, 2016 -- APS, pro-solar group together spend $6 million on Arizona Corporation Commission races: The... https://t.co/5xyq4EsoFm
azsolarcenter November 3, 2016 Solar Battles Playing Out On Arizona Ballot This Election: It may not be at the top of the... https://t.co/uYSRxv97YR
azsolarcenter November 4, 2016: Utility spends $3.5 million to keep Arizona Corporation Commission all-GOP: The state’s largest... https://t.co/imqk6z2sDU
azsolarcenter October 25, 2016: 42 States (and DC) try to screw with solar The 50 States of Solar Policy Report by the NC... https://t.co/JBYTzpf2ui
azsolarcenter October 24, 2016 -- Future of independent solar energy at stake in Corporation Commission raceL The long-term... https://t.co/D6jy4I5Ci0
azsolarcenter October 13, 2016 -- State policy matters: It is very easy to get distracted by the dog-and-pony show of this... https://t.co/MH7mEMg9MC
azsolarcenter October 16, 2016: Arizona Corporation Commission DebateL Five candidates running for three open seats on the... https://t.co/tm0XLl6CqG
azsolarcenter My Sun Day blog is posted to the Arizona Solar Center. https://t.co/vRrxwSSQpw
azsolarcenter There is No Plan(et) B: Climate change is no longer an issue that our politicians can kick down the road for... https://t.co/KHZzajZc9K
azsolarcenter High Noon: Nearly 40 years ago, President Carter proclaimed the dawn of the solar age. If President Carter was... https://t.co/JmZSHlmBUI
azsolarcenter High Noon: Nearly 40 years ago, President Carter proclaimed the dawn of the solar age. If President Carter was... https://t.co/rBgkaWKDs6
azsolarcenter High Noon: Nearly 40 years ago, President Carter proclaimed the dawn of the solar age. If President Carter was... https://t.co/RzXaQACpPR
azsolarcenter High Noon: Nearly 40 years ago, President Carter proclaimed the dawn of the solar age. If President Carter was... https://t.co/t1fKNTPwIB
azsolarcenter High Noon: Nearly 40 years ago, President Carter proclaimed the dawn of the solar age. If President Carter was... https://t.co/dWEKk3QR6H
azsolarcenter High Noon: Nearly 40 years ago, President Carter proclaimed the dawn of the solar age. If President Carter was... https://t.co/y4vhOpjfh1
azsolarcenter September 29, 2016: To cover a utility's fixed costs, are demand charges or time-of-use (TOU) rates superior?... https://t.co/RgneQWNKyM
azsolarcenter September 25, 2016: Arizona Public Service not only rejected an Arizona Corporation commissioner’s request to... https://t.co/iip6RwoOOS
azsolarcenter September 22, 2016: The Salt River Project (SRP) board of directors has agreed to purchase energy produced by... https://t.co/xYegEuiI43
azsolarcenter September 18, 2016: UniSource Energy officials have shelved plans to use of land surroundingMohave Community... https://t.co/eXmHxo03wQ
azsolarcenter September 13, 2016: The city of Sedona spent about 90 minutes at its September 13 council meeting discussing... https://t.co/LHV2QcsvYt
azsolarcenter September 15, 2016: New solar research projects at Arizona State University will receive $3.75 million in funding... https://t.co/N20NYLWxGy
azsolarcenter September 25, 2016: The parable of the frog and boiling water is hundreds of years old. It has been used... https://t.co/O5PYqvxIJg

Barriers to PV Implementation

There are many barriers to wide scale adoption of photovoltaic systems in Arizona.  Some of these are:

  • Costs
  • Suitable installation area
  • Electrical Code limits
  • Building Code requirements
  • Fire Code requirements
  • Homeowner Association rules
  • Electric Utility:
    • Policy/billing
    • Technical Limits
    • Legal

The cost of photovoltaic systems is continuing to decrease due to improvements in the technologies for photovoltaic modules and the inverters required to convert the dc electric power from the photovoltaic modules to regular ac electric power.  Some items are increasing, such as wire, mounting structures, electrical apparatus (switches, meters, conduit).  There are now many financing options to direct ownership that reduce or eliminate the upfront initial costs. The majority of residential photovoltaic systems being installed (2016) are now leased.

Many homes and commercial buildings simply do not have suitable areas for installing photovoltaic modules.  Some residential developers actively design the roof orientations to make photovoltaic modules installation difficult or impossible, mostly because they find it easier to sell new homes in a development when they all look the same.  This is not illegal, but is not in the spirit of an Arizona law (ARS: 33-439.  Restrictions on installation or use of solar energy devices invalid; exception).  There are utility restrictions on transporting electric power and water between properties, such as placing a photovoltaic on nearby property.  More information on this is in <link to new article "Arizona Solar Laws">.

Safety is always a major concern.  Except for some small low voltage photovoltaic systems (yard lights, etc.), many safety codes and standards apply in order to assure safe operation.  The National Electrical Code, re-issued every three years, is the main electrical safety code, but there are requirements in Building and Fire codes that limit photovoltaic system installations.  One relatively new requirement in the Building and Fire codes is to require clear access paths on roofs for first responders (firemen, etc.).  Another relatively new requirement in the National Electrical Code (2017 version) requires that the roof mounted module area have an automatic shutdown such that when the ac power is disconnected all the voltages are reduced to safe levels (the dc voltages would otherwise increase when not connected).  These requirements are generally reinforced in the building permit process.

In Arizona the electric utilities are essentially building barriers to photovoltaic systems by reducing direct and indirect incentives for photovoltaic systems.  See the discussion in our Economics section Economics of Photovoltaics.

In some states, the electric utilities offer a billing option for Aggregated Net Billing wherein photovoltaic energy produced on one property or billing meter can be administratively applied to another account, perhaps with a small transaction fee.

Sometimes the existing utility electrical distribution system simply can not safely accept the proposed photovoltaic output.  Those planning commercial size photovoltaic systems should check with the serving utility.

Recent (2015-2016) experience from an PV contractor: Some Barriers to Implementation of PV Systems

Technology & Science - Technical Documents

The following additional information is available:

Photovoltaic Systems related:

Some How to do it:

Photovoltaic systems present several hazards that are reduced or eliminated by following applicable Codes & Standards.  In Arizona there are no State enforced building and safety codes, this is a local responsibility. Electrical safety is covered by the National Electrical Code that is updated on a 3-year cycle (...2008/2011/2014/2017...).  The photovoltaic specific requirements are in Articles 690 and 705.  Various Arizona jurisdictions have adopted different versions, check with the local building permit to determine which version will apply.

There are also building code and fire code requirements.  Again, various Arizona jurisdictions have adopted different versions, check with the local building permit to determine which version will apply.  California has statewide requirements that have been developed by the Solar America Board for Codes and Standards
(www.solarabcs.org).  The following documents are very helpful in understand how to lay out photovoltaic arrays for safety and fire personnel access:

Understanding the CAL FIRE SOLAR PHOTOVOLTAIC INSTALLATION GUIDELINE

Understanding the CAL FIRE Solar Photovoltaic Installation Guideline (summary)

Some How Not To examples:

Other:

Solar Cells

Types of Solar Cells

There are several ways of producing solar cells and photovoltaic modules.

Single – Crystalline Cells

The oldest and most efficient type of photovoltaic cell is made from single-crystalline Silicon.  It is called single-crystalline because the atoms form a nearly perfect, regular lattice – if you could see into the cell, it would look exactly the same in almost every spot.  In these cells, electrons released during the photovoltaic effect have clear, unobstructed paths on which to travel.

Most silicon comes from ordinary sand and several steps are required to turn it into a crystalline solar cell.  The silicon must first be separated from the oxygen with which it is chemically bound.  Then it must be purified to a point where the material includes less than one non-silicon atom per billion.  The advent of large scale photovoltaic production over the last few years (2010 to 2016) has led to development of solar grade silicon with a price tag of $12 to $20 per kilogram. his is expected to decline even further as some very large production plants are completed.

The process of growing crystalline silicon begins with a vat of extremely hot, liquid silicon.  A “seed” of single-crystal silicon on a long wire is placed inside the vat.  Then, over the course of many hours, the liquid silicon is cooled while the seed is slowly rotated and withdrawn.  As they cool, silicon atoms inside the vat bond with silicon atoms of the seed.  The slower and smoother the process, the more likely the atoms are to bond in the perfect lattice structure.

When the wire in fully removed, it holds a crystal about 8 inches in diameter and 3 feet long – the size of long salami.  It is cut into wafers, 8/1000 to 10/1000 of an inch thick with a diamond-edge blade and much of the silicon crystal, now worth hundreds of dollars per kilogram, is turned into dust in the process.  The wafers are polished, processed into cells, and mounted in modules.

More than a hundred industry and university research teams have worked to upgrade and automate the manufacture of crystalline silicon solar cells.  They try to further reduce the cost of purified silicon, to develop high-speed crystal pullers and wafer-slicing techniques, and to improve the overall design of modules.

There are two or three major steps in producing solar cells from silicon wafers.  The photovoltaic effect is produced by forming a P-N junction <need link here> on the surface.  Some of the higher efficiency solar cells add a third layer of semiconductor, and then a system of contacts are need to provide electrical connections while allowing sunlight to pass through, generally called a grid.

One of the main objectives of PV research, however, has been to increase the efficiency with which photovoltaic modules convert sunlight into electricity.  Commercial solar modules typically turn 15 to 22 percent of the sunlight that strikes them into electricity.  In the laboratory, module efficiencies of more than 30 percent have been achieved.

NOTE: Photovoltaic conversion efficiency is generally based on module output rather than cell output. Modules include many connections and tiny wires in which electricity is lost, and space between the solar cells.  Consequently, modules have lower efficiencies than individual cells.

Polycrystalline Silicon Cells

Polycrystalline photovoltaic cells are exactly what the name implies – a patchwork quilt of single-crystalline silicon molecules.  Connections between these molecules are random and do not form a perfect lattice structure. Polycrystalline cells are less efficient than single-crystalline cells because released electrons cannot follow clear paths.

These cells are produced by pouring hot, liquid silicon into square molds or casts.  The silicon is cooled to form solid blocks, which are sliced like single-crystalline silicon.

These cells are less expensive to produce than single-crystalline cells because their manufacturing process does not require many careful hours of cooling and rotating silicon material.

The main challenge of polycrystalline cells is attaining a sufficiently high efficiency.  Typically, the boundaries between crystals impede the flow of electrons, resulting in module efficiencies of only 12 to 18 percent.

Concentrator cells

Concentrator cells employ lenses and mirrors to focus the sun’s light onto a high-efficiency, single-crystalline cell. Concentrators help gather sunlight so that a smaller-than-normal cell can produce the same amount of electricity as a standard module.  Efficiencies range from 20 to 25 percent with efficiencies as high as 34 percent for a single cell.

Although they use less of the costly photovoltaic material, other elements increase their cost.  Concentrator cells use more expensive materials and processes since they are a small proportion of the system cost. Because of their lenses and mirrors, for example, concentrator cells must aim directly at the sun.  A tracking system is crucial for effective operation.

Thin-film technologies

In the past decade, much progress has been made in developing and refining thin-film photographic cells.  These cells are created by depositing hot, liquid silicon or other semi-conductor materials onto glass, metal or plastic. Separate cells are not generally produced, the process forms photovoltaic modules with the solar cells interconnected.

One thin-film technology, which is already employed in many PV modules, is called “amorphous silicon”. It is composed or randomly arranged atoms, forming a dense, non-crystalline material resembling glass.  The silicon layer is less than a millionth of a meter (a micron) thick requiring considerably less pure silicon then other cell types.

Researchers are working to obtain higher efficiency from this material, which lacks the ordered structure and inherent photovoltaic properties of crystalline silicon.  Today’s commercial efficiency average 5 to 6 percent but efficiencies as high as 14.5 percent have been exhibited in laboratories.

Tandem Cells

These cells are still in the developmental stage but offer great potential for the future of photovoltaics.  Tandem, or multiple-junction cells, are actually several cells stacked on top of each other.  Each cell layer is able to convert a different wavelength, or color, of the light spectrum into electricity.

Tandem cells have displayed efficiencies higher than 25 percent in the laboratory and theorist predict efficiencies as 35 to 40 percent.

 

From Calculators to Power Plants: PV Systems in Action

 

Photovoltaics systems are quite different from traditional methods of generating electricity. Their power production is directly affected by the weather and the time of day – I. e. they can’t produce electricity without sunshine. Ironically, photovoltaic cells are also affected by the sun’s heat becoming less efficient at high temperatures.

One important quality of photovoltaics is their flexibility. Unlike nuclear plants, for example, PV systems can be made small enough to power a hand-held calculator, or large enough to power an entire community. When the demand for electricity increases, a PV system can simply be enlarged, provided the owner can afford it.

Photovoltaic is a young technology and important questions remain as to how it should best be used. Among these questions are:  What kind of backup should be provided for nighttime or cloudy days?  should solar systems be installed at homes or at special generating stations?  and should utilities or individuals own and operate solar electric systems?

Despite these questions, photovoltaics are already used in hundreds of different ways.  Those applications fall into four broad categories: stand-alone systems, grid-connected units, central utility stations, and consumer products.  Each category is discussed below.

  • Stand-alone systems

As the name implies, stand-alone photovoltaic systems are virtually self-sufficient.  They provide all the electricity for a particular application, operating without a utility-line backup.  They are typically small systems, generating less than 10 kilowatts of electricity, but some are substantially larger.

Stand-alone systems are most commonly found in areas far from power lines.  Ranchers, for example, often install solar-powered water pumps to replenish livestock watering holes in distant grazing areas.  These solar systems do not require constant refueling like diesel generators and often cost half as much as power line extensions.

More than 1200 Arizona homes or cabins rely on stand-alone photovoltaics as their main source of electricity.  In particular, PV powered homes are becoming a common sight on Arizona’s Native American reservations.  More than 140 homes on the Navajo Reservation get their electricity from the sun, and the Hopis are working toward 350 such homes.  The Hopis do not allow power lines to enter their villages and have relied for years on diesel generators or batteries, or have simply lived without electricity.

“Four villages have (utility) power lines running 1/8 to 1/4 miles from the village”, said Doran Dalton, sales manager for the Hopi Solar Electric Enterprise.  “We don’t hook up to the power lines because of our long-standing tradition of self-sufficiency.  We don’t have an objection to electricity, we simply want to own the source by which we get it.

Most Hopis live with very little electricity, and rely on small PV systems that power only a few lights and perhaps a television set.  Families that consume more energy install larger PV systems that provide electricity for all the conveniences of a modern home – microwave ovens computers, stereo systems, washing machines, evaporative coolers and lights.  Home PV systems can also power energy-consuming air conditioners and clothes dryers but these sizeable PV systems can cost more than $40,000.

Despite their vast electricity resources, utility companies also use stand-alone photovoltaic systems instead of extending costly power lines.  Many warning sirens at Palo Verde Nuclear Generating Station draw their power from solar panels.  Photovoltaics also furnish electricity for mountaintop microwave repeater stations owned by Salt River Project.

Stand-alone photovoltaics are used for numerous other applications in Arizona, including:  nearly 100 monitoring stations owned by the U.S. Geological Survey, some fire watch towers, a commercial radio station transmitter near Prescott, numerous emergency roadside telephones, billboards, and many irrigation or watering system controls.  At a recreation area near Roosevelt Lake, photovoltaics furnish all the electricity for indoor and outdoor lights and toilet fans.

  • Grid-connected systems

Homes or devices connected to photovoltaic systems as well as utility power lines are called “grid-connected systems.”  The utility can supply power at night, when electricity is cheapest, or simply serve as a backup. Federal law mandates that utility companies must purchase any excess power produced by the PV system, although at a reduced rate.

Homes or devices that employ both types of power are not common in Arizona, and the biggest reason is probably money.  Photovoltaics can be extremely cost-effective when compared to the price of extending power lines.  However, for individuals who live in cities or already have grid electricity, the choice to install PV is more difficult.  Homeowners must weigh the cost of utility bills – a few hundred dollars a month at the most – against the price of a photovoltaic system that can cost thousands of dollars for a typical house and a typical energy lifestyle.

As the price of PV decreases, and the cost of utility power increases, PV systems will compare more favorably for grid-connected applications.  In fact, utility companies like Salt River Project are already preparing for that possibility. 

Individuals who are not connected to the utility grid sometimes install utility lines to power only one or two home items.  One Scottsdale couple lived without utility power for seven years, relying entirely on a PV system and propane generator backup.  This off-grid system was sufficient to power an evaporative cooler and the other electrical devices in their home.  When in 1990, temperatures reached 122 degrees Fahrenheit, they decided to install an air conditioner.  To meet the unit’s electrical demand, the couple had to choose between doubling the size of the solar system (another $17,000), or paying for a power line at less than $8,000.  The rest, as they say, is history.

The same couple discovered an interesting problem that sometimes occurs with photovoltaic systems. Electricity provided by their PV system did not follow perfect sine-wave form, as does utility power.  That change in the quality of electricity ruined their computer printer two times before the couple discovered the reason—a faulty inverter. Low cost, high quality inverters are now available that avoid this problem.

 

  • Central Power Plants

There are now some enormous fields of photovoltaic arrays among the Saguaro and Ocotillo of Arizona’s deserts. Connected to the utility grid, their combined power may equal production at large coal plants such as the Navajo Generating Station near Page. 

Today, however, the world’s largest central photovoltaic power plant generates a maximum of only six megawatts of electricity – 125 times less than each of three units at the Navajo station.  This plant, called the Carrisa Plant project, was built in 1984 by ARCO Solar Corporation (now called “Siemens Solar”) and is connected to the grid owned by Pacific Gas & Electric Company.

The Carissa Plain plant covers dozens of acres of land with photovoltaic arrays mounted on two-axis trackers. Mirrors, placed next to the arrays, help reflect light to increase the potential power output.  Unfortunately, the intense reflected light has partially destroyed the protective module coatings and has actually decreased production of electricity.  Further development of better coatings should solve this problem.

For those reasons, the Carissa Plain plant is slated to be dismantled. Since, 1984, its only revenue has come from electricity sales to Pacific Gas and Electric Company.  The electricity is purchased at PG&E’s “avoided cost” of producing electricity – a price even lower than wholesale.  In the meantime, worldwide demand for photovoltaic panels has dramatically increased and their value has risen.  Consequently, it is more economical for the owners of Carissa Plain to sell the individual modules than to sell the electricity they produce.

Near Sacramento, California is another photovoltaic central power plant that has operated since 1984. The plant was built in two stages, called SMUDPV-1 and SMUD PV-2 and together they generate up to two megawatts of electricity at maximum production – enough to power 400 to 500 homes.  The total plant employs more than 58,000 photovoltaic modules and occupies more than 20 acres of land.

So far, three photovoltaic central power plants have been built in Arizona.  One completed in 1982 at Phoenix’s Sky Harbor Airport, was once the world’s largest grid-connected photovoltaic power plant.  It was designed to produce 225 kilowatts of power using concentrator solar modules.  The plant was dismantled in 1987, when the lease was not renewed.

APS has donated many of the panels from the plant to Arizona high schools and others are still being researched at the Solar Test and Research Center (STAR Center) in Tempe.

The Solar Test and Research Center was established in 1998 to test the effectiveness of different photovoltaic equipment in the Arizona climate.  It features five photovoltaic arrays, each producing 2 kilowatts of power used in the APS grid.  Many different types of photovoltaic cells are represented in the arrays.

Data obtained from the STAR Center provides valuable information about photovoltaic systems and how they operate.  For example APS has found that single-axis sun tracking systems improve electrical output by about 20 percent and double-axis trackers improve output another 20 percent.  They have also found that output decreases about 10 percent in midsummer, when the weather is hottest.

Arizona’s other photovoltaic central power plant is not utility-operated.  It belongs to a 24-home subdivision in Glendale, Arizona called “Solar One.”  The first-of-its-kind subdivision was constructed by John F Long Homes, with a photovoltaic field along its south side.  The 2600-panel system provides 192 kilowatts of electricity at peak output and provides much of the electricity used by homeowners during daylight hours.  The utility company provides nighttime power and purchases any excess produced by the PV system.  Until rates changed in 1991, some Solar One homeowners actually received refund checks from the utility company.  Photovoltaic central power plants have also received attention abroad.  They have been constructed in Denmark, Greece, Spain, Germany, Saudi Arabia and Japan.

Number cells or modules needed to power various applications

Number cells or modules

Item powered by photovoltaics

Electricity (in watts) produced at peak output

1 Small Cell

(1” X 2”

Calculator

.1 Watt

1 Standard Cell

(4” X 4”)

Small Yard Light

.5 Watt

Module  4’ x 1.5”

 

Color TV for 3 hours

60 Watts

110 Modules

(47 watts each)

A 1500-1800 square foot house with an evaporative cooler, not air conditioning

5.2 kilowatts

169 Modules

Same house with an air conditioner

8 kilowatts

2,600 Modules

Solar One, 24-home subdivision in Glendale, Arizona

192 kilowatts (PV system provides only part of total power used here)

58,000 Modules

SMUD PV-1 and PV-2 photovoltaic central power plant in California

2 megawatts

  • Consumer Products

From toys to security systems, ever-growing arrays of consumer products operate on electricity supplied by photovoltaic cells.  These products are available through catalogs, at many Arizona photovoltaic companies, and even in some department stores.

An estimated 200 million people already own PV-powered calculators and wristwatches. Other solar-powered devices include: portable camping lights, Frisbee-sized pool cleaners, small fans that roll up in car windows, and hats with tiny fans for extra cooling.

Car manufacturers such as Mazda and Audi now offer a “solar sunroof” option in some new car models.  These sunroofs, incorporating see-through photovoltaic cells, power ventilation systems that help cool a parked car as much as 20 degrees.  PV cells have also been used to power entire electric cars.

Landscape lights and security systems are practical, photovoltaic-powered products that are growing in popularity.  Depending upon the size and complexity of these systems, owners can avoid hundreds of dollars in expenses for digging power line trenches or hooking-up to a power line.

About

  • Welcome to the Arizona Solar Center

     This is your source for solar and renewable energy information in Arizona. Explore various technologies, including photovoltaics, solar water heating, solar architecture, solar cooking and wind power. Keep up to date on the latest industry news. Follow relevant lectures, expositions and tours. Whether you are a homeowner looking to become more energy efficient, a student learning the science behind the technologies or an industry professional, you will find valuable information here.
  • About The Arizona Solar Center

    Arizona Solar Center Mission- The mission of the Arizona Solar Center is to enhance the utilization of renewable energy, educate Arizona's residents on solar technology developments, support commerce and industry in the development of solar and other sustainable technologies and coordinate these efforts throughout the state of Arizona. About the Arizona Solar Center- The Arizona Solar Center (AzSC) provides a broad-based understanding of solar energy, especially as it pertains to Arizona. Registered Read More
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