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Arizona Solar Center Blog

Commentary from Arizona Solar Center Board Members and invited contributors.

While blog entries are initiated by the Solar Center, we welcome dialogue around the posted topics. Your expertise and perspective are highly valued -- so if you haven't logged in and contributed, please do so!

Renewable Energy: An Overview - Solar Architecture in Ancient Greece

According to Socrates, the ideal home should be cool in summer and warm in winter. But Socrates' ideal was not easy to accomplish 2,500 years ago in ancient Greece. The Greeks had no artificial means of cooling their homes during the scorching summers; nor were their heating systems, mostly portable charcoal-burning braziers, adequate to keep them warm in winter.

Modern excavations of many Classical Greek cities show that solar architecture flourished throughout the area. Individual homes were oriented toward the southern horizon, and entire cities were planned to allow their citizens equal access to the winter sun. A solar-oriented home allowed its inhabitants to depend less on charcoal - conserving fuel and saving money.

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Renewable Energy: An Overview - The Greenhouse Effect

Ninety-three million miles away, the sun blazes energy toward Earth. When this energy reaches Earth, the energy transmitted in short wave-lengths (visible light, ultraviolet, etc.) penetrates our atmosphere and strikes the Earth's surface. Energy in long wavelengths (such as infrared, thermal radiation or heat) is absorbed by carbon dioxide and other gases in the atmosphere. When penetrating short wavelengths strike Earth, they are converted into long wavelengths (in the form of heat radiation) and reflected back toward space. Some thermal radiation escapes, but most of it remains trapped inside our atmosphere. These long waves build up and keep Earth warm. This phenomenon, known as the greenhouse effect, enables life to flourish on Earth. Its future effects are also the subject of much discussion.

greenhouse

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Renewable Energy: An Overview - Water

Humans have long sought to control power as well as energy. For those that lived near lakes and streams, the advantages of transport by flotation must have been perceived early.

Before and during the Middle Ages, the geared water mill spread from Rome throughout western Europe. The watermill was used to grind grain, saw wood and marble, and for turning grindstones. The scarcity of slaves and the value of draft animals for other uses may have accelerated its acceptance. These watermills formed the power base for civilization prior to the Industrial Revolution.

But the power produced by these mills could not be transported - it had to be used at the mill site. Not until electricity could be generated practically from falling water could this barrier to water power be broken, and by then most of the industrial world had converted to steam power.

Still, the world's first hydroelectric power plant built at Godalming, England, in 1881 signaled a new era in power and energy. This renewable technology quickly took hold and spread throughout the world. Hydroelectric power was scarcely 20 years old when Arizona began to look to it as a means to turn the desert into an oasis.

More on hydropower here.

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Renewable Energy: An Overview - Solar

Updated December 11, 2013

Arizona is the sunniest state in the nation. It receives more than 4,000 hours of sunshine each year. This makes Arizona an ideal state for making solar energy work.

The modern solar industry, founded in 1974 following the Arab oil embargo of the previous year, experienced tremendous growth from the end of the 1970s through the late 1980s. The mainstay of the solar industry during that timeframe was solar water heating. It is estimated that more than 100,000 solar water heaters were installed in Arizona during the 1970s and 80s.

Today, Arizona ranks second only to California in market share for the burgeoning rooftop solar photovoltaic industry. Although solar electricity is only about one percent of the energy mix in Arizona, analysts predict phenomenal growth for solar power over the next two decades.  Traditional market drivers like favorable public policy (rebates and net metering) and tax credits, are getting a boost from falling prices and growing acceptance of alternative financing mechanisms that allow commercial and residential end-users to lease rooftop solar electric systems.

And as the solar industry grows, so does its beneficial effect on society, such as greater energy independence, improved environmental enhancements, and positive economic impact on jobs. In 2012, the Solar Energy Industries Association estimated that 9,800 people were employed in the solar energy industry in Arizona and approximately 120,000 full-time, permanent jobs nationwide.

The US Energy Information Administration (EIA) predicts that nationally the photovoltaic (solar electricity) industry will grow by 11.6 percent a year through 2040 and that the solar thermal industry will grow at 3.6 percent annually.

But, solar energy is more than just equipment. 

Passive solar homes (homes that are designed for natural heating and cooling) are popular in both mountain and desert areas of the state. Some of these homes have adobe, rammed earth, or straw bale as a building material. Others solar homes feature strategies and techniques such as solar porches, greenhouses, solar clearstory windows, trombe walls and solar air heaters.

Whether in rural areas or urban settings, Arizonans throughout the state are proving that solar energy can be used by anybody. Solar energy is not a vision of the future; it is an opportunity for today.

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Renewable Energy: An Overview - Wind

Wind may have been one of the first energy sources harnessed by man. For centuries, windmills have been used to pump water and operate grinding-mills. Less than 100 years ago, windmills provided a significant amount of energy consumed in rural areas.

Wind is often considered an indirect form of solar energy because wind currents are created when the sun unequally heats different areas of the Earth's atmosphere. It is renewable because the wind blows. In one 24-hour period, the wind blowing across the U.S. offers almost 14 times the energy used by the entire country. The problem arises in capturing that energy and putting it to use.

The potential for the commercialization of wind power in Arizona is limited because the average wind speed is between 7 and 10 miles per hour. Wind speeds above 14 m.p.h. are required before utility-grade windmills are feasible.

We have a lot more information on wind energy on the site: Try our "Wind Power" page and our wind links page.

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Renewable Energy: An Overview - Future Greenhouse Effect

As carbon dioxide and certain other gases increase in the atmosphere, more and more of the heat that should escape and radiate into space remains trapped. This trapped heat is the subject of debate within the scientific community. Scientists, lined up on each side of the issue disagree as to whether this heat may cause a rise in global temperatures.

According to the late Carl Sagan, a world-renowned environmental author, the typical global temperature difference between an ice age and an interglacial period is three to six degrees Celsius (5 degrees to 11 degree Fahrenheit). Sagan theorized that if global temperatures were to rise three to six degrees C, water would become warmer and expand, melt polar ice caps and raise sea levels. Under these conditions, many islands would disappear and the oceans would flood such coastal cities as New York, Los Angles and Tokyo. Just a three-foot rise in sea level would triple the size of San Francisco Bay.

Global warming may change precipitation patterns as well. Rainfall could decrease in some areas, causing water shortages and failing crops, while increasing in other areas with attendant flooding and soil erosion. Plants and animals that do not adapt quickly to the changing environment could become endangered species.

Some scientists, however, believe that an increase in global temperature could result in increased crop yields. Higher carbon dioxide levels associated with global warming could be beneficial for plants. If carbon dioxide levels doubled, it is theorized that plants could improve productivity by as much as one-third. Some evidence shows that a rise in carbon dioxide could increase a plant's optimal temperature and allow plants to thrive in warmer temperatures.

Those that subscribe to the greenhouse theory and global warming believe the primary cause of global warming is high emissions of carbon dioxide from industrial processes and the burning of fossil fuels. The U.S. is the world's largest carbon dioxide emitter. The greatest amount of carbon dioxide emitted comes from burning oil, coal and natural gas to produce the electricity that maintains the American standard of living. Transportation is the second largest contributor to the problem. Each car in the United State emits more carbon dioxide per year than the weight of the car.

Some models used by scientists support the theory that an increase in atmospheric carbon dioxide produces global warming. Scientists have been making attempts to measure any difference in global temperature. Researchers at NASA as well as other scientists believe there has been a 0.5 degree C (0.9 degree F) increase in the average global temperature over the last 100 years. Other scientists remain unconvinced. Researchers using the TIROS-N weather satellite to measure the temperature of the lower portions of the atmosphere during the 1980s did not find any detectable warming.

Despite the controversy over whether the global temperature is rising, the greenhouse effect is a well-established theory in atmospheric science. For example, Venus has a dense carbon dioxide atmosphere that could account for its surface temperatures of 426 degrees C (800 degrees F). Mars, with a thin carbon dioxide atmosphere, has an average temperature of -53 degrees C (-63 degrees F). This temperature difference, however, may also be partially explained by the distance of these planets from the sun.

More on the greenhouse effect here:

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Renewable Energy: An Overview - Future Greenhouse Effects

As carbon dioxide and certain other gases increase in the atmosphere, more and more of the heat that should escape and radiate into space remains trapped. This trapped heat is the subject of debate within the scientific community. Scientists, lined up on each side of the issue disagree as to whether this heat may cause a rise in global temperatures.

According to the late Carl Sagan, a world-renowned environmental author, the typical global temperature difference between an ice age and an interglacial period is three to six degrees Celsius (5 degrees to 11 degree Fahrenheit). Sagan theorized that if global temperatures were to rise three to six degrees C, water would become warmer and expand, melt polar ice caps and raise sea levels. Under these conditions, many islands would disappear and the oceans would flood such coastal cities as New York, Los Angles and Tokyo. Just a three-foot rise in sea level would triple the size of San Francisco Bay.

Global warming may change precipitation patterns as well. Rainfall could decrease in some areas, causing water shortages and failing crops, while increasing in other areas with attendant flooding and soil erosion. Plants and animals that do not adapt quickly to the changing environment could become endangered species.

Some scientists, however, believe that an increase in global temperature could result in increased crop yields. Higher carbon dioxide levels associated with global warming could be beneficial for plants. If carbon dioxide levels doubled, it is theorized that plants could improve productivity by as much as one-third. Some evidence shows that a rise in carbon dioxide could increase a plant's optimal temperature and allow plants to thrive in warmer temperatures.

Those that subscribe to the greenhouse theory and global warming believe the primary cause of global warming is high emissions of carbon dioxide from industrial processes and the burning of fossil fuels. The U.S. is the world's largest carbon dioxide emitter. The greatest amount of carbon dioxide emitted comes from burning oil, coal and natural gas to produce the electricity that maintains the American standard of living. Transportation is the second largest contributor to the problem. Each car in the United State emits more carbon dioxide per year than the weight of the car.

Some models used by scientists support the theory that an increase in atmospheric carbon dioxide produces global warming. Scientists have been making attempts to measure any difference in global temperature. Researchers at NASA as well as other scientists believe there has been a 0.5 degree C (0.9 degree F) increase in the average global temperature over the last 100 years. Other scientists remain unconvinced. Researchers using the TIROS-N weather satellite to measure the temperature of the lower portions of the atmosphere during the 1980s did not find any detectable warming.

Despite the controversy over whether the global temperature is rising, the greenhouse effect is a well-established theory in atmospheric science. For example, Venus has a dense carbon dioxide atmosphere that could account for its surface temperatures of 426 degrees C (800 degrees F). Mars, with a thin carbon dioxide atmosphere, has an average temperature of -53 degrees C (-63 degrees F). This temperature difference, however, may also be partially explained by the distance of these planets from the sun.

More on the greenhouse effect here:

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Renewable Energy: An Overview - Solar

Today in Arizona, solar energy is making an ever increasing impact. It is believed that Arizona has the highest per capita number of solar installations of any state in the continental U.S. Most of these installations are for solar hot water, but there are other popular uses of solar energy in Arizona today.

Passive solar homes (homes that are designed for natural heating and cooling) are popular in both mountain and desert areas of the state. Some of these homes have adobe, rammed earth, or straw bale as a building material.

Arizonans also have solar features on their homes such as solar porches, greenhouses, solar clearstory windows, trombe walls and solar air heaters.

Solar cooking is becoming popular in all parts of the state. Approximately 500 solar ovens are sold in Arizona each year. Many schools use solar ovens to teach solar science principles.

For remote locations, photovoltaics are used to provide power in places where constructing new power lines is too expensive or impractical. As the price of this technology falls, new applications become more cost effective in areas that power from a utility is close at hand.

Solar energy can be used by anybody in Arizona today. Solar energy is not a vision of the future; it is an opportunity for today.

Arizona is the sunniest state in the nation. It receives more than 4,000 hours of sunshine each year. This makes Arizona an ideal state for making solar energy work.

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Renewable Energy: An Overview - Wind

Wind may have been one of the first energy sources harnessed by man. For centuries, windmills have been used to pump water and operate grinding-mills. Less than 100 years ago, windmills provided a significant amount of energy consumed in rural areas.

Wind is often considered an indirect form of solar energy because wind currents are created when the sun unequally heats different areas of the Earth's atmosphere. It is renewable because the wind blows. In one 24-hour period, the wind blowing across the U.S. offers almost 14 times the energy used by the entire country. The problem arises in capturing that energy and putting it to use.

The potential for the commercialization of wind power in Arizona is limited because the average wind speed is between 7 and 10 miles per hour. Wind speeds above 14 m.p.h. are required before utility-grade windmills are feasible.

We have a lot more information on wind energy on the site: Try our "Wind Power" page and our wind links page.

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AZ Dept. of Commerce "Bright Ideas" Report on Photovoltaics - Introduction

#azdoc-rprt-hdg#

Photovoltaics (PV) - Introduction

Throughout the history of mankind the sun has inspired worship, awe and fear.  In ancient Egypt, it was the sun god Ra who held the supreme place among all deities as the giver of life.  In Greek and Roman legend, the sun was a fiery chariot driven across the face of the sky.

We can only imagine how those ancient people might respond to the sight of thin, shiny rectangles harnessing the sun’s awesome energy.  Even today with knowledge of scientific principles, observers are astonished by the technology of photovoltaics.

Photovoltaic cells convert sunlight directly into electricity.  They have successfully powered space satellites for more than 35 years and now furnish electricity for a wide variety of applications on earth.

Solar-generated electricity powers water pumps, weather monitoring stations, fire watchtowers, and billboard lights, irrigation system, streetlights, boat battery chargers, and numerous other devices in Arizona and throughout the world.  Glistening photovoltaic panels can easily be seen at Tucson bus stops, atop many roadside emergency telephones, and near artwork along Phoenix freeways.

Solar cells in space work in a vacuum at extremely high or extremely low temperatures while exposed to intense radiation. Other systems have been used on frozen tundra, in scorching deserts and on mountain peaks.  Tougher tests for a young technology would be hard to design.

Nevertheless, photovoltaic systems have established a record of reliability and have proven cost effective for many uses.  They produce no pollution in creating electricity and require no water to operate.  As environmental problems escalate and solar cells costs are reduced, these systems will almost certainly play an important role in our energy future.

The remainder of the "Photovoltaics" pages are here:

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AZ Dept. of Commerce "Bright Ideas" Report on Photovoltaics - Introduction

#azdoc-rprt-hdg#

Photovoltaics (PV) - Introduction

Throughout the history of mankind the sun has inspired worship, awe and fear.  In ancient Egypt, it was the sun god Ra who held the supreme place among all deities as the giver of life.  In Greek and Roman legend, the sun was a fiery chariot driven across the face of the sky.

We can only imagine how those ancient people might respond to the sight of thin, shiny rectangles harnessing the sun’s awesome energy.  Even today with knowledge of scientific principles, observers are astonished by the technology of photovoltaics.

Photovoltaic cells convert sunlight directly into electricity.  They have successfully powered space satellites for more than 35 years and now furnish electricity for a wide variety of applications on earth.

Solar-generated electricity powers water pumps, weather monitoring stations, fire watchtowers, and billboard lights, irrigation system, streetlights, boat battery chargers, and numerous other devices in Arizona and throughout the world.  Glistening photovoltaic panels can easily be seen at Tucson bus stops, atop many roadside emergency telephones, and near artwork along Phoenix freeways.

Solar cells in space work in a vacuum at extremely high or extremely low temperatures while exposed to intense radiation. Other systems have been used on frozen tundra, in scorching deserts and on mountain peaks.  Tougher tests for a young technology would be hard to design.

Nevertheless, photovoltaic systems have established a record of reliability and have proven cost effective for many uses.  They produce no pollution in creating electricity and require no water to operate.  As environmental problems escalate and solar cells costs are reduced, these systems will almost certainly play an important role in our energy future.

The remainder of the "Photovoltaics" pages are here:

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