 By:  Daiou Asimina  Giannakos Efthimis  Ziogas Jannis

Photovoltaics are a very helpful technological achievement, which help out people to convert sun energy into electricity.

 Owing to the growing demand for the use of renewable resources, photovoltaics have become popular and are nowadays used by a large number of people especially in Europe.

Photovoltaics use the method of generating electric power by using solar cells packaged in photovoltaic modules, often electrically connected in multiples as solar photovoltaic arrays to convert the solar energy into electricity.

The photovoltaic panel has as a main part the solar cell, which is a properly processed thin half- conductor at a plane surface. The incidence of the sunlight on the photovoltaic panel creates electric tension and when it is connected to the right charge, it generates electricity.

To make their use more simply and easily understood, photons from sunlight knock electrons of the photovoltaics into a higher state of energy, therefore creating electricity.

In addition, a photovoltaic system contains the following parts: The photovoltaical generator with the proper mechanical support and possibly a system observing the sun’s orbit Batteries (as a storing system) Strength’s definition and an apparatus of control, which care about the measurement and the observation A reserve photovoltaic generator.

ADVANTAGES Photovoltaics use a friendly to the environment technology, and as a result they do not cause filth during the electricity production They can be positioned on already existing constructions, saving a large amount of money In addition, solar energy is a renewable resource and it can be easily found everywhere without the least cost

Their use is completely noiseless Photovoltaic panels have costless demands of maintenance Last but not least, they have large life duration, as well as the future expansion is also possible.

Building a power plant will not only cost much money(when for first time positioned), but also a sheer volume of land, so as to be build. On the other hand, they do not capture so much area when built on the rooftop of an already existing construction Moreover, they are a little bit expensive on account of the fact that they ought to be renewed every other years. Also, it will cost much more when it is moved to another area, even if it is not so far Photovoltaics have even nowadays a small grade of output

World's largest photovoltaic (PV) power plants (30 MW or larger) Name of PV power plant Country DC Peak Power (MW) GW·h /year Capacity factor Notes Olmedilla Photovoltaic Park Spain Completed September 2008 Puertollano Photovoltaic Park Spain Moura photovoltaic power station Portugal Completed December 2008 Waldpolenz Solar ParkGermany ,000 First Solar thin-film CdTe modules. Completed December 2008 Arnedo Solar PlantSpain34 Completed October 2008 Merida/Don Alvaro Solar Park Spain30 Completed September 2008 Planta Solar La Magascona & La Magasquila Spain30 Planta Solar Ose de la Vega Spain30 And now, let’s see how the largest power plants are distributed in the whole world:

Photovoltaics would also be found very helpful in the following situations: In buildings Photovoltaic solar panels on a house roof. Building-integrated photovoltaics (BIPV) are increasingly incorporated into new domestic and industrial buildings as a major source of electrical power..

Typically, an array is incorporated into the roof or walls of a building, and roof tiles with integrated PV cells can now be purchased. Arrays can also be retrofitted into existing buildings; in this case they are usually fitted on top of the existing roof structure. Alternatively, an array can be located separately from the building but connected by cable to supply power for the building

Where a building is located in a remote/isolated area photovoltaics may be the preferred possibility for generating electricity, or even when their use is combined with wind energy and hydroelectric power.

Under such circumstances, batteries will be helpful by storing electric power. In locations near the grid, however, it is advisable that people will locate a photovoltaic system nearby.

The power output of photovoltaic systems for installation in buildings is usually described in kilowatt-peak units (kWp). Most photovoltaics are grid connected. In the event the grid fails, the local system must not feed the grid to prevent the possible creation of dangerous islanding.

In transport PV has traditionally been used for auxiliary power in space. PV is rarely used to provide motive power in transport applications, but is being used increasingly to provide electric power in boats and cars. Recent advances in solar race cars, however, have produced cars that with little changes could be used for transportation.

PHOTOVOLTAICS IN GREECE Owing to the fact that Greece receives much solar energy, our country can use the sun as an renewable source of energy. That’s why there are many photovoltaic systems and panels in Greece. For instance, there are two big photovoltaic systems in Athens (one in Iliupoli and one in Kifisia), one in Thessaloniki, in Kyklades (Santori island), in Kilkis and in Lefkada(an island in Ionio Pelagos).

We can exploit the solar energy, by using simple small flexible photovoltaic elements with size like a mobile phone, to charge a battery(or the same mobile telephone), untilwe will install big PV systems which will meet the needs of electricity of one home or one flat. Small mobile solar energy system is a system with photovoltaics, small in size so that it can be easily moved and it can supply us wherever we want. Usually accumulators are required for storing up the produced energy. Autonomous solar energy system: It includes two parts; it is bigger than the last system and is usually installed permanently. It meets the needs of electricity in cottages and in caravans. Accumulators are required too. The photovoltaic elements convert some of the solar energy into electricity. The electricity which is produced is continuous (DC) and we use it to charge accumulators which supply electronic devices. By using an inverter we can convert continuous electricity into alternating and we supply the devices which are function with alternating electricity. For bigger photovoltaic systems and special systems which are connected with the basic network, the installation must be done by a skillful technician. A basic photovoltaic system includes a solar collector, the regulator which charges the battery and the accumulator. Optionally the accumulator is connected with an inverter. T

We can meet all the needs, although not preferred for devices like cookers, heaters and other huge electronic heating devices in their performance and economic sections. In these cases, gas or solar heaters are recommended. PV systems can be used in connection with the P.E.C. (Public Electricity Company) or autonomous systems independent to the main network. In, connected to the network, PVs, if the energy that the PV system produces is not meet the demands, the network supplies with the rest demanded energy automatically. In autonomous PVs, the energy that be produced is stored in special accumulators (batteries) ensuring electricity even though the weather conditions are not ideal or during the night. PV systems worth in case that we are interested in supplying remote sites away from the main network, in which the cost of an attempt to transfer electricity from this source will be even bigger. They are preferred more than a fuel generator due to the zero use of fuels. They also worth in case that will need a noiseless reserve system during a blackout. Moreover they are preferred in need of a small mobile energy system to be moved wherever somebody wants. Excluding the economic section there is also environmental one. PV systems produce purest energy conducing in reduction of pollution that creates global warming. They are noiseless and they conduce in independence of mineral fuels which are not for ever.

The sun emits on Earth in just one hour the same amount of energy all humanity consumes in one year. The photovoltaic solar energy is a source of clean energy, renewable and free. Let’s use it!!!!

2 ND EXPERIMENTAL HIGH SCHOOL, THESSALONIKI