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Photovoltaic Power
The sun emits almost all of its energy in a range of wavelengths from about 2x10^-7 to 4x10^-6 meters. Most of this energy is in the visible light region. Each wavelength corresponds to a frequency and an energy: the shorter the wavelength, the higher the frequency and the greater the energy (which is expressed in electron-volts, or eV). Red light is at the low-energy end of the visible spectrum and violet light is at the high-energy end, where it has half again as much energy as red light. In the invisible portions of the spectrum, radiation in the ultraviolet region, which causes the skin to tan, has more energy than that in the visible region. Likewise, radiation in the infrared region, which we feel as heat, has less energy than the radiation in the visible region.
Solar cells respond differently to the different wavelengths, or colors, of light. For example, crystalline silicon can use the entire visible spectrum, plus some part of the infrared spectrum. But energy in part of the infrared spectrum, as well as longer-wavelength radiation, is too low to produce current flow. Higher-energy radiation can produce current flow, but much of this energy is likewise not usable. In summary, light that is too high or low in energy is not usable by a cell to produce electricity. Rather, it is transformed into heat.

Air Mass

The sun is continually releasing an enormous amount of radiant energy into the solar system. The Earth receives a tiny fraction of this energy; yet, an average of 1367 watts (W) reaches each square meter (m²) of the outer edge of the Earth's atmosphere. The atmosphere absorbs and reflects some of this radiation, including most X-rays and ultraviolet rays. Still, the amount of the sun's energy that reaches the surface of the Earth every hour is greater than the total amount of energy that the world's human population uses in a year.

How much energy does light lose in traveling from the edge of the atmosphere to the surface of the Earth? This energy loss depends on the thickness of the atmosphere that the sun's energy must pass through. The radiation that reaches sea level at high noon in a clear sky is 1000 W/m2 and is described as "air mass 1" (or AM1) radiation. As the sun moves lower in the sky, the light passes through a greater thickness (or longer path) of air, losing more energy. Because the sun is overhead for only a short time, the air mass is normally greater than one—that is, the available energy is less than 1000 W/m² in average for the Earth. For Bulgarian territory the available solar energy is about 1 500 W/m² in average. That is why solar energy investments in Bulgaria are more profitable in the comparison with most of the other WU countries - see sell price here.

Scientists have given a name to the standard spectrum of sunlight at the Earth's surface: AM1.5G (where G stands for "global" and includes both direct and diffuse radiation, described next) or AM1.5D (which includes direct radiation only). The number "1.5" indicates that the length of the path of light through the atmosphere is 1.5 times that of the shorter path when the sun is directly overhead.

The standard spectrum outside the Earth's atmosphere is called AM0, with no light passing through the atmosphere. AM0 is typically used to predict the expected performance of PV cells in space. The intensity of AM1.5D radiation is approximated by reducing the AM0 spectrum by 28%, where 18% is absorbed and 10% is scattered. The global spectrum is 10% greater than the direct spectrum. These calculations give about 970 W/m² for AM1.5G. However, the standard AM1.5G spectrum is "normalized" to give 1000 W/m2, because of inherent variations in incident solar radiation.
Direct and Diffuse Light

As we have noted, the Earth's atmosphere and cloud cover absorb, reflect, and scatter some of the solar radiation entering the atmosphere. Nonetheless, an enormous amount of the sun's energy reaches the Earth's surface and can therefore be used to produce PV electricity. Some of this radiation is direct and some is diffuse, and the distinction is important because some PV systems (flat-plate systems) can use both forms of light, but concentrator systems can only use direct light.

Flat-plate collectors, which typically contain a large number of solar cells mounted on a rigid, flat surface, can make use of both direct sunlight and the diffuse sunlight reflected from clouds, the ground, and nearby objects.

Direct light consists of radiation that comes straight from the sun, without reflecting off of clouds, dust, the ground, or other objects. Scientists also talk about direct-normal radiation, referring to the portion of sunlight that comes directly from the sun and strikes the plane of a PV module at a 90-degree angle.

Diffuse light is sunlight that is reflected off of clouds, the ground, or other objects. It obviously takes a longer path than a direct light ray to reach a module. Diffuse light cannot be focused by the optics of a concentrator PV system.

Insolation

The actual amount of sunlight falling on a specific geographical location is known as insolation—or "incident solar radiation." Insolation values for a specific site are sometimes difficult to obtain. Weather stations that measure solar radiation components are located far apart and may not carry specific insolation data for a given site. We have developed a spatial measurement system (patented) and related software for high accurate calculation of on-site insulation. Using our patented system we can find the best fitted solar module that maximize PV energy yield for given site.

The two types of solar cells used are crystalline or thin film. Crystalline cells are more efficient (less area required), but they are more expensive per square meter. Overall, both cost are similar. Thin film cells are flexible, so - more mounting options for unique roof applications.

There are many options for installing a PV system. Once have the basic system components in place, you can gradually add more solar cell panels as your budget allows. Using inverters, standard 220-volt electricity is available to run lights, electronics, and appliances.

The best and most convenient PV systems use automatic controls and a bank of efficient batteries. If there is a utility power outage, the controls switch entirely to PV power. The electricity will not feed back into the utility wires, which could present a hazard to workers repairing the lines.

A typical PV system will have solar panels on the roof or the ground in a sunny location. They can be tilted up on the roof to face the sun. To produce the most electricity, there are mounting racks available that automatically follow the sun. They use no electricity, just the sun’s heat and gravity to rotate.

A new PV option uses solar cells built directly into shingle panels. They resemble standard shingles and function as the roofing material. If you are building a new house or need a new roof, this option makes a lot of sense. As PV energy is area-dependent (providing approximately 1GWhr per hectare per year) it is extremely suitable for decentralised electricity production.

A new concept for local energy production is envisaged for the future:

* Centralised large-scale electricity production where small and medium sized producers will be connected to electricity grids.
* The development of stand-alone energy systems producing electricity and heat for single houses or apartments with different components such as PV, fuel cells, etc.
* The development of 'mini-grids' for a limited area should be investigated. With these grids, small energy systems such as PV systems and fuel cells in individual houses would be connected together to supply energy. They would be supplemented by conditioning and storage systems and could serve as an interface between the main grid and single houses.

* For large-scale market introduction of PV power, the key issues are to reduce investment costs, ensure easy integration and long-term supply reliability.
* Further pre-market research should be carried out in three main areas:
o Low-cost PV integration into buildings;
o Intelligent and extremely low-cost control systems;
o Research into electricity storage and making new technologies suitable for PV use.

Our expert knowledge for optimal PV tilting and PV cooling based on the advanceed patented and patent pending solutions.
TOP !

39A/2, Jerusalem Blvd., 1784 Sofia, Copyrights by George Tonchev

Phone/fax +3592 8760 431,+3592 8770 481,+3598 9787 2857, +3598 888 40 39 13 Mail to: g@tonchev.org
WEB design: George Tonchev Jr.

About Design Services Photovoltaic Power PV Investment Patented Solutions Wind-PV Systems Hydrokinetic - PV ROTOJET Tech. Distributed Power Automotive Patents		Photovoltaic Power The sun emits almost all of its energy in a range of wavelengths from about 2x10^-7 to 4x10^-6 meters. Most of this energy is in the visible light region. Each wavelength corresponds to a frequency and an energy: the shorter the wavelength, the higher the frequency and the greater the energy (which is expressed in electron-volts, or eV). Red light is at the low-energy end of the visible spectrum and violet light is at the high-energy end, where it has half again as much energy as red light. In the invisible portions of the spectrum, radiation in the ultraviolet region, which causes the skin to tan, has more energy than that in the visible region. Likewise, radiation in the infrared region, which we feel as heat, has less energy than the radiation in the visible region. Solar cells respond differently to the different wavelengths, or colors, of light. For example, crystalline silicon can use the entire visible spectrum, plus some part of the infrared spectrum. But energy in part of the infrared spectrum, as well as longer-wavelength radiation, is too low to produce current flow. Higher-energy radiation can produce current flow, but much of this energy is likewise not usable. In summary, light that is too high or low in energy is not usable by a cell to produce electricity. Rather, it is transformed into heat. Air Mass The sun is continually releasing an enormous amount of radiant energy into the solar system. The Earth receives a tiny fraction of this energy; yet, an average of 1367 watts (W) reaches each square meter (m²) of the outer edge of the Earth's atmosphere. The atmosphere absorbs and reflects some of this radiation, including most X-rays and ultraviolet rays. Still, the amount of the sun's energy that reaches the surface of the Earth every hour is greater than the total amount of energy that the world's human population uses in a year. How much energy does light lose in traveling from the edge of the atmosphere to the surface of the Earth? This energy loss depends on the thickness of the atmosphere that the sun's energy must pass through. The radiation that reaches sea level at high noon in a clear sky is 1000 W/m2 and is described as "air mass 1" (or AM1) radiation. As the sun moves lower in the sky, the light passes through a greater thickness (or longer path) of air, losing more energy. Because the sun is overhead for only a short time, the air mass is normally greater than one—that is, the available energy is less than 1000 W/m² in average for the Earth. For Bulgarian territory the available solar energy is about 1 500 W/m² in average. That is why solar energy investments in Bulgaria are more profitable in the comparison with most of the other WU countries - see sell price here. Scientists have given a name to the standard spectrum of sunlight at the Earth's surface: AM1.5G (where G stands for "global" and includes both direct and diffuse radiation, described next) or AM1.5D (which includes direct radiation only). The number "1.5" indicates that the length of the path of light through the atmosphere is 1.5 times that of the shorter path when the sun is directly overhead. The standard spectrum outside the Earth's atmosphere is called AM0, with no light passing through the atmosphere. AM0 is typically used to predict the expected performance of PV cells in space. The intensity of AM1.5D radiation is approximated by reducing the AM0 spectrum by 28%, where 18% is absorbed and 10% is scattered. The global spectrum is 10% greater than the direct spectrum. These calculations give about 970 W/m² for AM1.5G. However, the standard AM1.5G spectrum is "normalized" to give 1000 W/m2, because of inherent variations in incident solar radiation. Direct and Diffuse Light As we have noted, the Earth's atmosphere and cloud cover absorb, reflect, and scatter some of the solar radiation entering the atmosphere. Nonetheless, an enormous amount of the sun's energy reaches the Earth's surface and can therefore be used to produce PV electricity. Some of this radiation is direct and some is diffuse, and the distinction is important because some PV systems (flat-plate systems) can use both forms of light, but concentrator systems can only use direct light. Flat-plate collectors, which typically contain a large number of solar cells mounted on a rigid, flat surface, can make use of both direct sunlight and the diffuse sunlight reflected from clouds, the ground, and nearby objects. Direct light consists of radiation that comes straight from the sun, without reflecting off of clouds, dust, the ground, or other objects. Scientists also talk about direct-normal radiation, referring to the portion of sunlight that comes directly from the sun and strikes the plane of a PV module at a 90-degree angle. Diffuse light is sunlight that is reflected off of clouds, the ground, or other objects. It obviously takes a longer path than a direct light ray to reach a module. Diffuse light cannot be focused by the optics of a concentrator PV system. Insolation The actual amount of sunlight falling on a specific geographical location is known as insolation—or "incident solar radiation." Insolation values for a specific site are sometimes difficult to obtain. Weather stations that measure solar radiation components are located far apart and may not carry specific insolation data for a given site. We have developed a spatial measurement system (patented) and related software for high accurate calculation of on-site insulation. Using our patented system we can find the best fitted solar module that maximize PV energy yield for given site. The two types of solar cells used are crystalline or thin film. Crystalline cells are more efficient (less area required), but they are more expensive per square meter. Overall, both cost are similar. Thin film cells are flexible, so - more mounting options for unique roof applications. There are many options for installing a PV system. Once have the basic system components in place, you can gradually add more solar cell panels as your budget allows. Using inverters, standard 220-volt electricity is available to run lights, electronics, and appliances. The best and most convenient PV systems use automatic controls and a bank of efficient batteries. If there is a utility power outage, the controls switch entirely to PV power. The electricity will not feed back into the utility wires, which could present a hazard to workers repairing the lines. A typical PV system will have solar panels on the roof or the ground in a sunny location. They can be tilted up on the roof to face the sun. To produce the most electricity, there are mounting racks available that automatically follow the sun. They use no electricity, just the sun’s heat and gravity to rotate. A new PV option uses solar cells built directly into shingle panels. They resemble standard shingles and function as the roofing material. If you are building a new house or need a new roof, this option makes a lot of sense. As PV energy is area-dependent (providing approximately 1GWhr per hectare per year) it is extremely suitable for decentralised electricity production. A new concept for local energy production is envisaged for the future: * Centralised large-scale electricity production where small and medium sized producers will be connected to electricity grids. * The development of stand-alone energy systems producing electricity and heat for single houses or apartments with different components such as PV, fuel cells, etc. * The development of 'mini-grids' for a limited area should be investigated. With these grids, small energy systems such as PV systems and fuel cells in individual houses would be connected together to supply energy. They would be supplemented by conditioning and storage systems and could serve as an interface between the main grid and single houses. * For large-scale market introduction of PV power, the key issues are to reduce investment costs, ensure easy integration and long-term supply reliability. * Further pre-market research should be carried out in three main areas: o Low-cost PV integration into buildings; o Intelligent and extremely low-cost control systems; o Research into electricity storage and making new technologies suitable for PV use. Our expert knowledge for optimal PV tilting and PV cooling based on the advanceed patented and patent pending solutions. TOP !
		39A/2, Jerusalem Blvd., 1784 Sofia, Copyrights by George Tonchev Phone/fax +3592 8760 431,+3592 8770 481,+3598 9787 2857, +3598 888 40 39 13 Mail to: g@tonchev.org WEB design: George Tonchev Jr.

Rotostar JSCo has developed number of advanced rotors for wind and water turbines that described on these pages. For other innovation- see www.tonchev.org