• What is the photovoltaic phenomenon?

    PV (photovoltaic) Solar Panels generate electricity by the Photovoltaic Effect. Discovered in 1839 by 19yr old Edmund Becquerel, the photovoltaic effect is the phenomenon that certain materials produce electric current when they are exposed to light. For traditional PV solar panels a semiconductor PN junction is manufactured in which two halves of one pure silicon crystal are doped with two different dopants (e.g. arsenic, gallium, aluminium, phosphorus). One half of the crystal is left electron deficient (the p-type layer), and one half is left with an excess of electrons (the n-type layer). The dopants in the semiconductor lead to an electric field across the junction between the two halves of the crystal with electrons able to travel in one direction only – from the electron rich half to the electron poor half.

    Where the two halves of the crystal meet, there is a depletion region, so called because it is depleted of charge carriers (electrons and holes). Electrons move from the n-type (negative) side to the p-type (positive) side of the crystal recombining with holes. Likewise holes move from the p-type side to the n-type side. As the silicon atoms themselves do not move, any holes which remain uncovered by electrons in the n-type side are left positively charged, and any electrons without holes to cover in the p-type side remain negatively charged. This leaves positive material close to the junction in the n-type side, and negative material close to the junction in the p-type side with a potential between the two sides of around 0.6-0.7 volts in a silicon pn junction. This potential barrier between the p and n-type sides of the crystal prevents further electrons and holes from travelling across the junction until sunlight hits the solar cell and releases electrons with enough energy to overcome the barrier.

  • When were the first commercial solar systems built?

    The first photovoltaic systems were used in space applications. The first factories that produced photovoltaic panels for commercial use were build in the seventies. During that decade, the first installations took place, used for applications such as electrification of remoted villages and water pumping. Countries like U.S.A., France and Japan were among the first countries with photovoltaic plants. The first photovoltaic plant installed in Greece was a photovoltaic park of 100 kWp at Kithnos island.
  • What are the most important advantages of photovoltaic systems?

    The most important advantages of electrical energy production from photovoltaic systems are:

    i. The electrical energy is produced in a totally clean and ecological way. The “fuel” in the case of photovoltaic systems is solar radiation. They don’t use any other fuel, they don’t emit any kind of gas or liquid waste, they don’t have any effect on other natural resources and they are not harmful for the vegetation and animal life.

    ii. Photovoltaic systems function is noiseless and there is no optical disturbance in the environment.

    iii. Small photovoltaic plants can be used in unexploited surfaces on roofs, facades and other building envelope’s spaces.

    iv. Solar radiation is a source of energy inexhaustible and available everywhere on the planet. There is no need for transportation of this form of energy from one place to another and it can be used without any treatment. In this way, extra energy is saved.

    v. A photovoltaic system can be dimensioned regarding the energy needs or the available surface while there is always the ability of increasing the installed capacity or moving the photovoltaic system. They are “flexible” systems considering their size, capacity and consequently their applications.

  • In which areas or surfaces can a photovoltaic system be installed?

    Photovoltaic systems can be installed practically on every surface; either it is a field area or a building surface (roof, terrace, facades etc). The only limitation from the Greek state has to do with the protected areas (like Natura regions, archaeological places etc) or forests and agricultural areas of high productivity, where photovoltaic installations are forbidden.
  • Do photovoltaic systems have a harmful effect on the environment?

    Photovoltaic systems do not have any effect on the environment since they are not connected to any kind of optical or acoustic disturbance. According to KYA 19500/2004 (ΦΕΚ 1671 Β΄/11.11.2004, “Modification and completion of correspondence of activities concerning production of electrical energy to the level of disturbance that are mentioned in the urban planning law”), photovoltaic plants of installed capacity under 500 kWp are defined as non disturbing installations while photovoltaic plants over 500 kWp are defined as systems of low disturbance. By this law, photovoltaic systems are excluded from article 7 of the presidential decree that sets the limitation of 500 meters from the defined limits of residential areas for industrial installations of medium and high distrurbance. After all, photovoltaics are a technology that is integrated on buildings and their exclusion from built areas would be contradictory.
  • I am a private individual. For which reasons should I invest on photovoltaic technology?

    Investing on photovoltaic systems is first of all an environmentally friendly action that has as a result, the production of “clean” electricity, either it is used for the energy needs of a house or it is directly fed to the grid. In the first case, in remote dwellings where the connection to the grid is an expensive solution, the use of photovoltaics can be cheaper apart from environmentally friendly. In the second case where the investor chooses to produce electricity that will be fed to the grid, practically there is the ability of selling the electricity. For photovoltaic plants installed on field, the price is defined depending on the plant outpout, the region of the installation and the date of the signed Convention of Sale with the Operator of the Grid and it is presented in the following table:
  • How exactly can I use the electrical energy that my photovoltaic system will produce?

    The electrical energy that is produced by a photovoltaic system can be used in two ways and by their combination. The first way is to covering the energy needs of a house, of an office and generally of a building or of a system that uses electrical energy. The second way is to sell the electrical energy by the price defined by current law frame. There is the possibility of combining these two different ways of exploiting the electrical energy, by covering on one hand the energy needs of a user and by feeding the grid the surplus of electrical energy.
  • What is the amount of electrical energy that a photovoltaic system produces?

    A photovoltaic system of 1 kWp can produce from 1200 kWh (Northern Greece) to 1500 kWh (Crete and Southeast Aegean) per year. The produced energy can increase with the use of automatically oriented trackers that “follow” the sun during the day, capturing larger amounts of solar radiation and consequently leading to higher energy performance of the system, up to 30%
  • What is the average payback time of an investment in photovoltaic systems?

    Given the current Feed-in tariffs and the decrease in the price of the equipment, the payback of an investment in photovoltaics does not exceed 7 to 8 years, even in regions with low radiation. In regions with high radiation, the payback period can be 4 to 5 years.
  • For how many years can I sell the electrical energy to the grid?

    Selling electrical energy produced by a photovoltaic system is guaranteed for 20 years and the feed-in tariff depends on the date of the signed contract between the owner of the PV plant and the eligible Administrator of the grid under the condition of trial functioning or, for the cases where there is no trial functioning, activation of the connection of the photovoltaic system in 18 months for PV plants up to 10 MW and in 36 months for PV plants larger than 10 MW. In the case of Photovoltaic systems on rooftops, instead of a sale contract there is a Counterbalancing Contract that is signed between the owner of the PV plant and the Electricity Provider. This contract has a duration of 25 years starting off the day of the activation of the PV system.

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