1. Solar power The sun is the basic source of energy of our planet. The sun is a star of medium size that because of the big temperatures of its elements which compose it, the hydrogen, the molecules but also their particles are in a stage of “plasma”. In these temperatures, certain millions of o C, the very rapidly moved cores of hydrogen (H) are join together, and create cores of element of helium (He). This nuclear reaction - fusion of cores is “exothermic” and is going with enormous quantities of energy or heat or as is used to be said : solar energy, that radiated to all directions in space. This happens continuously for 5 billions years roughly, the sun contains enormous quantities of hydrogen and it is not expected to be a reduction of energy which is radiated by the sun. In our country the sunlight lasts more than 2700 hours per year. In Western Macedonia and the Ipirus it presents smaller prices from 2200 until 2300 hours, while in Rhodes and southern Crete it exceeds the 3100 hours annually.

2. Solar power The solar power that earth takes from the sun in one week is equal in the energy of all fuels in the planet The Earth receives only the one billion of energy the Sun radiates ( huge quantity )

5. Solar Energy Solar hot water systems use sunlight to heat water. Commercial solar water heaters began appearing in the United States in the 1890s. These systems saw increasing use until the 1920s but were gradually replaced by relatively cheap and more reliable conventional heating fuels. The economic advantage of conventional heating fuels has varied over time resulting in periodic interest in solar hot water; however, solar hot water technologies have yet to show the sustained momentum they had until the 1920s. Solar water heating technologies have high efficiencies relative to other solar technologies. Performance will depend upon the site of deployment, but flat-plate and evacuated- tube collectors can be expected to have efficiencies above 60 percent during normal operating conditions In addition, solar water heating is particularly appropriate for low- temperature (25-70 °C) applications such as swimming pools, domestic hot water, and space heating. The most common types of solar water heaters are batch systems, flat plate collectors and evacuated tube collectors.

6. Heating, ventilation, and air conditioning (HVAC) systems of buildings are closely interrelated. All seek to provide thermal comfort, acceptable indoor air quality, and reasonable installation, operation, and maintenance costs. Conventional HVAC systems account for roughly 28 percent of the energy used in the United States and European Union. [ Many solar heating, cooling, and ventilation technologies can be used to offset a portion of this energy. Thermal mass materials store solar energy during the day and release this energy during cooler periods. Common thermal mass materials include stone, cement, and water. The proportion and placement of thermal mass should consider several factors such as climate, daylighting, and shading conditions. When properly incorporated, thermal mass can passively maintain comfortable temperatures while reducing energy consumption. More advanced thermal mass systems can be also be used for ventilation.

7. Electricity can be generated from the sun in several ways. Photovoltaics (PV) has been mainly developed for small and medium-sized applications, from the calculator powered by a single solar cell to the PV power plant. For large-scale generation, concentrating solar thermal power plants have been more common but new multi-megawatt PV plants have been built recently. Other solar electrical generation technologies are still at the experimental stage.

8. Active Solar Domestic Water Heating The active water systems that can be used to heat domestic hot water are the same as the ones that provide space heat. A space heat application will require a larger system and additional connecting hardware to a space heat distribution system. There are five major components in active solar water heating systems: Collector(s) to capture solar energy. Circulation system to move a fluid between the collectors to a storage tank Storage tank Backup heating system Control system to regulate the overall system operation There are two basic categories of active solar water heating systems - direct or open loop systems and indirect or closed loop systems. Direct Systems The water that will be used as domestic hot water is circulated directly into the collectors from the storage tank (typically a hot water heater which will back up the solar heating). Indirect Systems that use antifreeze fluids need regular inspection (at least every 2 years) of the antifreeze solution to verify its viability. Oil or refrigerant circulating fluids are sealed into the system and will not require maintenance. A refrigerant system is generally more costly and must be handled with care to prevent leaking any refrigerant.

10. Passive Solar Energy Passive solar energy systems require no energy to operate and are an intrinsic part of the home design. Passive systems add little additional cost, operate with almost no supervision and require little or no maintenance. The basic elements of all passive systems are south-facing windows and internal thermal mass. Solar heating is simply sunlight entering the house that is absorbed and converted into heat energy which is later released inside the house as it cools. A passive solar home is one where the design and construction of the home itself is made to keep the house naturally warm in the winter using the sun's energy. The design should also keep the house naturally cool during the summer.The sun is a very intense source of energy. When designed properly, a passive solar home can experience heating costs that are 80% to 95% lower than for the average home. Air conditioning costs can also be reduced to a minimal level. The basic idea of passive solar home design is to invite sunlight into the house during the winter, and once it is inside the home, to hold it in and store it until nighttime. Conversely, the sun needs to be kept out during the summer.

11. Electricity from the Sun Electricity can be generated from solar energy in two ways. The first is to capture heat from the sun and use this to power a conventional turbine or generator. The other is to use the photovoltaic effect, which converts light directly into electricity using materials called semiconductors. Solar Thermal Electric Power Plants The two main types of solar thermal power plants are Solar Chimneys (where heated air in a tower rises to drive turbines) and Concentrating Solar Power (CSP) plants (which use various types of reflectors to concentrate sunlight into a heat absorber). These are both industrial scale applications which are not suitable for the urban environment.

13. Photovoltaic Cells The word photovoltaic is a marriage of the words ‘photo’, which means light, and ‘voltaic’, which refers to the production of electricity. Photovoltaic technology generates electricity from light. Electricity is the existence (either static or flowing) of negatively charged particles called electrons. Certain materials, called semiconductors, can be adapted to release electrons when they are exposed to light. One of the most common of these materials is silicon (an element found in, amongst other things, sand), which is the main material in 98% of solar PV cells made today. All PV cells have at least two layers of such semiconductors: one that is positively charged and one that is negatively charged. When light shines on the semiconductor, the electric field across the junction between these two layers causes electricity to flow - the greater the intensity of the light, the greater the flow of electricity. Although the photovoltaic effect was known to the Victorians, it was not until humanity launched into the space race that the unique qualities of solar PV as a power source began to be fully explored. Following this kick-start the technology has raced along a path to commercialization and the cost of PV generated electricity has plummeted as manufacturing costs have decreased and cell efficiencies have improved.

14. Anatomy of a Solar Cell Before now, our silicon was all electrically neutral. Our extra electrons were balanced out by the extra protons in the phosphorous. Our missing electrons (holes) were balanced out by the missing protons in the boron. When the holes and electrons mix at the junction between N-type and P-type silicon, however, that neutrality is disrupted. Do all the free electrons fill all the free holes? No. If they did, then the whole arrangement wouldn't be very useful. Right at the junction, however, they do mix and form a barrier, making it harder and harder for electrons on the N side to cross to the P side. Eventually, equilibrium is reached, and we have an electric field separating the two sides. This electric field acts as a diode, allowing (and even pushing) electrons to flow from the P side to the N side, but not the other way around. It's like a hill -- electrons can easily go down the hill (to the N side), but can't climb it (to the P side).diode So we've got an electric field acting as a diode in which electrons can only move in one direction. When light, in the form of photons, hits our solar cell, its energy frees electron- hole pairs.photons Each photon with enough energy will normally free exactly one electron, and result in a free hole as well. If this happens close enough to the electric field, or if free electron and free hole happen to wander into its range of influence, the field will send the electron to the N side and the hole to the P side. This causes further disruption of electrical neutrality, and if we provide an external current path, electrons will flow through the path to their original side (the P side) to unite with holes that the electric field sent there, doing work for us along the way. The electron flow provides the current, and the cell's electric field causes a voltage. With both current and voltage, we have power, which is the product of the two. There are a few more steps left before we can really use our cell. Silicon happens to be a very shiny material, which means that it is very reflective. Photons that are reflected can't be used by the cell. For that reason, an antireflective coating is applied to the top of the cell to reduce reflection losses to less than 5 percent. The final step is the glass cover plate that protects the cell from the elements. PV modules are made by connecting several cells (usually 36) in series and parallel to achieve useful levels of voltage and current, and putting them in a sturdy frame complete with a glass cover and positive and negative terminals on the back.

15. Photovoltaic Cells (Solar Cells), How They Work a The encapsulate, made of glass or other clear material such clear plastic, seals the cell from the external environment. b The contact grid is made of a good conductor, such as a metal, and it serves as a collector of electrons. c Through a combination of a favorable refractive index, and thickness, this layer serves to guide light into the PV Cell. Without this layer, much of the light would bounce off the surface of the cell. The RTWCG method of depositing this AR Coating is by far the most desirable technique known to us. d N-type silicon is created by doping (contaminating) the Si with compounds that contain one more valance electrons than Si does, such as with either Phosphorus or Arsenic. Since only four electrons are required to bond with the four adjacent silicon atoms, the fifth valance electron is available for conduction.valance electrons e P-type silicon is created by doping with compounds containing one less valance electrons than Si does, such as with Boron. When silicon (four valance electrons) is doped with atoms that have one less valance electrons (three valance electrons), only three electrons are available for bonding with four adjacent silicon atoms, therefore an incomplete bond (hole) exists which can attract an electron from a nearby atom. Filling one hole creates another hole in a different Si atom. This movement of holes is available for conduction.valance electrons The back contact, made out of a metal, covers the entire back surface and acts as a conductor.

16. The path of the photon. After a photon makes it's way through the encapsulate it encounters the antireflective layer. The antireflective layer channels the photon into the lower layers of the solar cell. Click on the following link if you would like to learn about our novel room temperature wet chemical growth antireflective layer (RTWCG - AR). antireflective layer Once the photon passes the AR coating, it will either hit the silicon surface or the contact grid metallization. The metallization, being opaque, lowers the number of photons reaching the Si surface. The contact grid must be large enough to collect electrons yet cover as little of the solar cell's surface, allowing more photons to penetrate. A photon causes the photoelectric effect.photoelectric effect The photon's energy transfers to the valance electron of an atom in the n-type Si layer. That energy allows the valance electron to escape its orbit leaving behind a hole. In the n-type silicon layer, the free electrons are called majority carriers whereas the holes are called minority carriers. As the term "carrier" implies, both are able to move throughout the silicon layer, and so are said to be mobile. Inversely, in the p-type Si layer, electrons are termed minority carriers and holes are termed majority carriers, and of course are also mobile. The pn-junction. The region in the solar cell where the n-type and p-type Si layers meet is called the pn-junction. As you may have already guessed, the p-type Si layer contains more positive charges, called holes, and the n-type Si layer contains more negative charges, or electrons. When p-type and n-type materials are placed in contact with each other, current will flow readily in one direction (forward biased) but not in the other (reverse biased). An interesting interaction occurs at the pn-junction of a darkened photovoltaic cell. Extra valance electrons in the n-type layer move into the p- type layer filling the holes in the p-type layer forming what is called a depletion zone. The depletion zone does not contain any mobile positive or negative charges. Moreover, this zone keeps other charges from the p and n-type layers from moving across it. So, to recap, a region depleted of carriers is left around the junction, and a small electrical imbalance exists inside the solar cell. This electrical imbalance amounts to about 0.6 to 0.7 volts. So due to the pn-junction, a built in electric field is always present across the solar cell.