On an office building, roof areas can be covered with glass PV modules, which can be semi-transparent to provide shaded light. On a factory or warehouse, large roof areas are the best location for solar modules. If the roof is flat, then arrays can be mounted using techniques that do not breach the weatherproofed roof membrane. Also, skylights can be partially covered with PV.
The vertical walls of office buildings provide several opportunities for PV incorporation, as well as sunshades or balconies incorporating a PV system. Sunshades may have the PV system mounted externally to the building, or have PV cells specially mounted between glass sheets comprising the window.
Monday, March 28, 2011
Residential uses of Solar Energy
The number of PV installations on buildings connected to the electricity grid has grown in recent years. Government subsidy programs (particularly in Germany and Japan) and green pricing policies of utilities or electricity service providers have stimulated demand. Demand is also driven by the desire of individuals or companies to obtain their electricity from a clean, non-polluting, renewable source. These consumers are usually willing to pay only a small premium for renewable energy. Increasingly, the incentive is an attractive financial return on the investment through the sale of solar electricity at premium feed-in tariff rates.
In solar systems connected to the electricity grid, the PV system supplies electricity to the building, and any daytime excess may be exported to the grid. Batteries are not required because the grid supplies any extra demand. However, to be independent of the grid supply, battery storage is needed to provide power at night.
Holiday or vacation homes without access to the electricity grid can use solar systems more cost-effectively than if the grid was extended to reach the location. Remote homes in sunny locations can obtain reliable electricity to meet basic needs with a simple system comprising of a PV panel, a rechargeable battery to store the energy captured during daylight hours, a regulator (or charge controller), and the necessary wiring and switches. Such systems are often called solar home systems (SHS).
In solar systems connected to the electricity grid, the PV system supplies electricity to the building, and any daytime excess may be exported to the grid. Batteries are not required because the grid supplies any extra demand. However, to be independent of the grid supply, battery storage is needed to provide power at night.
Holiday or vacation homes without access to the electricity grid can use solar systems more cost-effectively than if the grid was extended to reach the location. Remote homes in sunny locations can obtain reliable electricity to meet basic needs with a simple system comprising of a PV panel, a rechargeable battery to store the energy captured during daylight hours, a regulator (or charge controller), and the necessary wiring and switches. Such systems are often called solar home systems (SHS).
History of Solar Energy
Very often there is confusion about the various methods used to harness solar energy.Energy from the sun can be categorized in two ways: (1) in the form of heat (or thermal energy), and (2) in the form of light energy. Solar thermal technologies uses the solar heat energy to heat substances (such as water or air) for applications such as space heating, pool heating and water heating for homes and businesses. There are a variety of products on the market that uses solar thermal energy. Often the products used for this application are called solar thermal collectors and can be mounted on the roof of a building or in some other sunny location. The solar heat can also be used to produce electricity on a large utility-scale by converting the solar energy into mechanical energy.
So, fossil fuels is actually solar energy stored millions and millions of years ago. Indirectly, the sun or other are responsible for all our energy. Even nuclear energy comes from a star because the uranium atomsused in nuclear energy were created in the fury of a nova - a star exploding. Let's look at ways in which we can use the solar energy.
So, fossil fuels is actually solar energy stored millions and millions of years ago. Indirectly, the sun or other are responsible for all our energy. Even nuclear energy comes from a star because the uranium atomsused in nuclear energy were created in the fury of a nova - a star exploding. Let's look at ways in which we can use the solar energy.
Saturday, February 26, 2011
Our Sun - A Closer Look
In this section, we will discuss some of the more prominent features of the Sun. And we will also discuss the Solar Eclipse (found on its own page).
Here is a nice summary of some of the important features. Just click on the image to see a large version. The layers in this image is not to scale.
Corona This outer layer is very dim - a million times dimmer than the photosphere and oddly enough, it is the hottest. At 106 K it would seem the heat would be unbearable for us, but remember in Physics heat is a measure of molecular energy - the movement of molecules within a space. Because the Corona extends several million kilometers into space, there is a lot of room for molecules to move. It is this movement that is the source of the solar winds. The high temperature of the Corona can force ions to move as fast as a million kilometers per hour.
Chromosphere Chromosphere means "sphere of color," but this layer is 10-4 as dense as the photosphere so it is not that bright. In fact, the best way to view the chromosphere it to use a special narrow band filter called a Hydrogen-Alpha (Hα) filter. The wavelength is 656.3 nm which is in the red (lower energy) part of the spectrum. This wavelength is given by the single electron in the Hydrogen atom dropping to the second orbit (more in the physics section). The temperature of the inner portion of this layer is lower (at 4400 K) than the photosphere, but jumps suddenly to 25,000 K. From this point to the transition into the Corona, the temperature jumps sharply to 400,000 degrees. The reason for this is not clearly understood and remains an active subject to Astronomers studying the Sun, but suspect the magnetic flux as a result of (as well as resulting in) sunspot formation might provide some clues.
Photosphere The Photosphere, Chromosphere and Corona are the three layers that make up the "atmosphere" of the Sun. The Photosphere is the inner-most layer and is the layer we easily see every day. It burns at 5800 K. Oddly enough, the photosphere is opaque to light, only allowing transferred energy from the convection layer below. It is the opaque feature of the photosphere that shields us from directly viewing the thermonuclear core and provide the shape of the Sun. The transferred energy from the convection zone below occurs in the form of granules (see the photo above). As the hotter gas rises up, the cooler gas descends only to be re-heated by the convection layer and the process repeats itself. Sometimes disturbances in the magnetic field will produce sunspots, which occur within this layer, but more on that later.
Convective Zone We cannot visualize past the photosphere, but we can create models and examine particles emanating from the Sun to get an idea to the Sun's interior structure. Three internal layers dominate the anatomy with the outer layer (just under the photosphere) called the convective zone. Radiation is not an effective mean of generating the heat energy produced by the core, so the convective layer acts as the buffer to stabilize this energy. Once a photon enters the convective zone, it can take 170,000 years for it to reach the photosphere. The action of the photon is something called the "random walk" where the photon collides with other photons mainly because the opacity of this zone it a bit high. While there is some pretty unforgiving mathematics involved in determining exactly how much opacity there it, it is important to know the convective zone helps maintain the hydrostatic equilibrium within the Sun by acting as a buffer.
Radiative Zone This layer of the Sun is responsible for delivering the photons from the Core to the Convective layer. The radiative layer "radiates" the energy by the emission and reabsorbtion of photons.
Core The heart of the Sun is the core. Not much to say here accept the gravity was strong enough to bring Hydrogen together to initiate fusion. The magic temperature for fusion is 10,000,000 K. The energy released is balanced by the radiative and convective layers of the Sun to create the hydrostatic equilibrium necessary to prevent the Sun from flying apart or to burn its fuel to fast.
Here is a nice summary of some of the important features. Just click on the image to see a large version. The layers in this image is not to scale.
Corona This outer layer is very dim - a million times dimmer than the photosphere and oddly enough, it is the hottest. At 106 K it would seem the heat would be unbearable for us, but remember in Physics heat is a measure of molecular energy - the movement of molecules within a space. Because the Corona extends several million kilometers into space, there is a lot of room for molecules to move. It is this movement that is the source of the solar winds. The high temperature of the Corona can force ions to move as fast as a million kilometers per hour.
Chromosphere Chromosphere means "sphere of color," but this layer is 10-4 as dense as the photosphere so it is not that bright. In fact, the best way to view the chromosphere it to use a special narrow band filter called a Hydrogen-Alpha (Hα) filter. The wavelength is 656.3 nm which is in the red (lower energy) part of the spectrum. This wavelength is given by the single electron in the Hydrogen atom dropping to the second orbit (more in the physics section). The temperature of the inner portion of this layer is lower (at 4400 K) than the photosphere, but jumps suddenly to 25,000 K. From this point to the transition into the Corona, the temperature jumps sharply to 400,000 degrees. The reason for this is not clearly understood and remains an active subject to Astronomers studying the Sun, but suspect the magnetic flux as a result of (as well as resulting in) sunspot formation might provide some clues.
Photosphere The Photosphere, Chromosphere and Corona are the three layers that make up the "atmosphere" of the Sun. The Photosphere is the inner-most layer and is the layer we easily see every day. It burns at 5800 K. Oddly enough, the photosphere is opaque to light, only allowing transferred energy from the convection layer below. It is the opaque feature of the photosphere that shields us from directly viewing the thermonuclear core and provide the shape of the Sun. The transferred energy from the convection zone below occurs in the form of granules (see the photo above). As the hotter gas rises up, the cooler gas descends only to be re-heated by the convection layer and the process repeats itself. Sometimes disturbances in the magnetic field will produce sunspots, which occur within this layer, but more on that later.
Convective Zone We cannot visualize past the photosphere, but we can create models and examine particles emanating from the Sun to get an idea to the Sun's interior structure. Three internal layers dominate the anatomy with the outer layer (just under the photosphere) called the convective zone. Radiation is not an effective mean of generating the heat energy produced by the core, so the convective layer acts as the buffer to stabilize this energy. Once a photon enters the convective zone, it can take 170,000 years for it to reach the photosphere. The action of the photon is something called the "random walk" where the photon collides with other photons mainly because the opacity of this zone it a bit high. While there is some pretty unforgiving mathematics involved in determining exactly how much opacity there it, it is important to know the convective zone helps maintain the hydrostatic equilibrium within the Sun by acting as a buffer.
Radiative Zone This layer of the Sun is responsible for delivering the photons from the Core to the Convective layer. The radiative layer "radiates" the energy by the emission and reabsorbtion of photons.
Core The heart of the Sun is the core. Not much to say here accept the gravity was strong enough to bring Hydrogen together to initiate fusion. The magic temperature for fusion is 10,000,000 K. The energy released is balanced by the radiative and convective layers of the Sun to create the hydrostatic equilibrium necessary to prevent the Sun from flying apart or to burn its fuel to fast.
Our Sun - A Closer Look
In this section, we will discuss some of the more prominent features of the Sun. And we will also discuss the Solar Eclipse (found on its own page).
Here is a nice summary of some of the important features. Just click on the image to see a large version. The layers in this image is not to scale.
Corona This outer layer is very dim - a million times dimmer than the photosphere and oddly enough, it is the hottest. At 106 K it would seem the heat would be unbearable for us, but remember in Physics heat is a measure of molecular energy - the movement of molecules within a space. Because the Corona extends several million kilometers into space, there is a lot of room for molecules to move. It is this movement that is the source of the solar winds. The high temperature of the Corona can force ions to move as fast as a million kilometers per hour.
Chromosphere Chromosphere means "sphere of color," but this layer is 10-4 as dense as the photosphere so it is not that bright. In fact, the best way to view the chromosphere it to use a special narrow band filter called a Hydrogen-Alpha (Hα) filter. The wavelength is 656.3 nm which is in the red (lower energy) part of the spectrum. This wavelength is given by the single electron in the Hydrogen atom dropping to the second orbit (more in the physics section). The temperature of the inner portion of this layer is lower (at 4400 K) than the photosphere, but jumps suddenly to 25,000 K. From this point to the transition into the Corona, the temperature jumps sharply to 400,000 degrees. The reason for this is not clearly understood and remains an active subject to Astronomers studying the Sun, but suspect the magnetic flux as a result of (as well as resulting in) sunspot formation might provide some clues.
Photosphere The Photosphere, Chromosphere and Corona are the three layers that make up the "atmosphere" of the Sun. The Photosphere is the inner-most layer and is the layer we easily see every day. It burns at 5800 K. Oddly enough, the photosphere is opaque to light, only allowing transferred energy from the convection layer below. It is the opaque feature of the photosphere that shields us from directly viewing the thermonuclear core and provide the shape of the Sun. The transferred energy from the convection zone below occurs in the form of granules (see the photo above). As the hotter gas rises up, the cooler gas descends only to be re-heated by the convection layer and the process repeats itself. Sometimes disturbances in the magnetic field will produce sunspots, which occur within this layer, but more on that later.
Convective Zone We cannot visualize past the photosphere, but we can create models and examine particles emanating from the Sun to get an idea to the Sun's interior structure. Three internal layers dominate the anatomy with the outer layer (just under the photosphere) called the convective zone. Radiation is not an effective mean of generating the heat energy produced by the core, so the convective layer acts as the buffer to stabilize this energy. Once a photon enters the convective zone, it can take 170,000 years for it to reach the photosphere. The action of the photon is something called the "random walk" where the photon collides with other photons mainly because the opacity of this zone it a bit high. While there is some pretty unforgiving mathematics involved in determining exactly how much opacity there it, it is important to know the convective zone helps maintain the hydrostatic equilibrium within the Sun by acting as a buffer.
Radiative Zone This layer of the Sun is responsible for delivering the photons from the Core to the Convective layer. The radiative layer "radiates" the energy by the emission and reabsorbtion of photons.
Core The heart of the Sun is the core. Not much to say here accept the gravity was strong enough to bring Hydrogen together to initiate fusion. The magic temperature for fusion is 10,000,000 K. The energy released is balanced by the radiative and convective layers of the Sun to create the hydrostatic equilibrium necessary to prevent the Sun from flying apart or to burn its fuel to fast.
Here is a nice summary of some of the important features. Just click on the image to see a large version. The layers in this image is not to scale.
Corona This outer layer is very dim - a million times dimmer than the photosphere and oddly enough, it is the hottest. At 106 K it would seem the heat would be unbearable for us, but remember in Physics heat is a measure of molecular energy - the movement of molecules within a space. Because the Corona extends several million kilometers into space, there is a lot of room for molecules to move. It is this movement that is the source of the solar winds. The high temperature of the Corona can force ions to move as fast as a million kilometers per hour.
Chromosphere Chromosphere means "sphere of color," but this layer is 10-4 as dense as the photosphere so it is not that bright. In fact, the best way to view the chromosphere it to use a special narrow band filter called a Hydrogen-Alpha (Hα) filter. The wavelength is 656.3 nm which is in the red (lower energy) part of the spectrum. This wavelength is given by the single electron in the Hydrogen atom dropping to the second orbit (more in the physics section). The temperature of the inner portion of this layer is lower (at 4400 K) than the photosphere, but jumps suddenly to 25,000 K. From this point to the transition into the Corona, the temperature jumps sharply to 400,000 degrees. The reason for this is not clearly understood and remains an active subject to Astronomers studying the Sun, but suspect the magnetic flux as a result of (as well as resulting in) sunspot formation might provide some clues.
Photosphere The Photosphere, Chromosphere and Corona are the three layers that make up the "atmosphere" of the Sun. The Photosphere is the inner-most layer and is the layer we easily see every day. It burns at 5800 K. Oddly enough, the photosphere is opaque to light, only allowing transferred energy from the convection layer below. It is the opaque feature of the photosphere that shields us from directly viewing the thermonuclear core and provide the shape of the Sun. The transferred energy from the convection zone below occurs in the form of granules (see the photo above). As the hotter gas rises up, the cooler gas descends only to be re-heated by the convection layer and the process repeats itself. Sometimes disturbances in the magnetic field will produce sunspots, which occur within this layer, but more on that later.
Convective Zone We cannot visualize past the photosphere, but we can create models and examine particles emanating from the Sun to get an idea to the Sun's interior structure. Three internal layers dominate the anatomy with the outer layer (just under the photosphere) called the convective zone. Radiation is not an effective mean of generating the heat energy produced by the core, so the convective layer acts as the buffer to stabilize this energy. Once a photon enters the convective zone, it can take 170,000 years for it to reach the photosphere. The action of the photon is something called the "random walk" where the photon collides with other photons mainly because the opacity of this zone it a bit high. While there is some pretty unforgiving mathematics involved in determining exactly how much opacity there it, it is important to know the convective zone helps maintain the hydrostatic equilibrium within the Sun by acting as a buffer.
Radiative Zone This layer of the Sun is responsible for delivering the photons from the Core to the Convective layer. The radiative layer "radiates" the energy by the emission and reabsorbtion of photons.
Core The heart of the Sun is the core. Not much to say here accept the gravity was strong enough to bring Hydrogen together to initiate fusion. The magic temperature for fusion is 10,000,000 K. The energy released is balanced by the radiative and convective layers of the Sun to create the hydrostatic equilibrium necessary to prevent the Sun from flying apart or to burn its fuel to fast.
Our Sun
At the heart of our Solar System is the Sun. Every day, the Sun rises and sets and ancient astronomers used this consistency to erect temples to predict seasonal changes for the harvest. The warmth of the Sun is vital to life on Earth because of photosynthesis and its warmth heats the surface to help with weather changes. But what is the Sun made of? How does the Sun generate its energy? Will the Sun shine forever? The answers are within....
Image of Sun in white light Mean Distance from Earth: 149,598,000 km
Mean angular diameter: 32 arcmin
Radius: 696,109 km
Mass: 1.9891 x 1030 kg
Composition: 74% Hydrogen
25% Helium
1% Other
Mean Density: 1410 kg/m3
Mean Temperature: 5800K
Luminosity: 3.86 x 1026 Watts
Orbit about Galaxy: 220 million years
Orbital Speed: 220 km/s
Image of Sun in white light Mean Distance from Earth: 149,598,000 km
Mean angular diameter: 32 arcmin
Radius: 696,109 km
Mass: 1.9891 x 1030 kg
Composition: 74% Hydrogen
25% Helium
1% Other
Mean Density: 1410 kg/m3
Mean Temperature: 5800K
Luminosity: 3.86 x 1026 Watts
Orbit about Galaxy: 220 million years
Orbital Speed: 220 km/s
Solar System Formation
Everything has a beginning, and our story begins when the cloud that was the Solar Nebula began to contract. All stars exist in islands called galaxies, and galaxies contain old and new stars as well as clumps of dust clouds. These clouds contain mostly hydrogen and some heavier metals (any elements that are heavier than helium is considered a metal by Astronomers). As we will learn the the Sun section, stars create their energy by a process called fusion. When a star ends its life, it explodes in a tremendous phenomenon called a supernova. A supernova has so much energy that heavy metals are formed - metals like iron and gold. These elements "seed" surrounding hydrogen clouds so that newer stars will contain more heavy elements in their atmospheres.
It is believed that for a system of planets to form around a star during cloud contraction the cloud must contain heavy elements.
It is believed that for a system of planets to form around a star during cloud contraction the cloud must contain heavy elements.
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