Renewable Energy from Alternative Sources


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pv panels

Photovoltaic and Energy


how much energy it takes to produce solar panels? It 'true that more energy is used to build a plant than the plant itself will actually produce? It 'true that it is uneconomic?

Someone says that "a photovoltaic module decades to return to work
The energy that was used to produce

It is not true! Very recent studies have demonstrated that the ERR (Energy Return Time) for a photovoltaic panel, ie the relationship between the energy expended to build the panel material, and the energy produced from the panel once it is in place, is between 1.5 and 4.4 years, range that depends of course on the technology used to build it and the place and type of installation (of course in areas with high solar radiation, as Lital, the production of photovoltaic electricity is higher and the Return Time Energy will be less)


what are the production steps?

After oxygen, silicon, is the most widespread element on the Earth's crust (28%). In its pure state has a crystalline structure similar to that of diamond. All modern computer technology are possible with silicon electronics. The microchips, integrated boards, microcircuits are all made with silicon electronics. To obtain the silicon from the quartz sand and siliceous rocks. Through processes of reduction, the silica being cast loses carbon atoms that are treated by reducing agents (sodium, coal). After various stages of fusion / crystallization is obtained by metallurgical silicon used for PV cells, which is a waste product because it is less pure silicon electronics. The silicon used for solar cells can be: polycrystalline, monocrystalline and amorphous (that has no crystalline structure).


The metallurgical silicon cast into ingots (diameter 10-15 cm) is sliced ​​into sections of from 0.25 to 0.35 mm thick. The PV cell consists of two layers of doped silicon (ie silicon with different electrical potential) placed between the two sides of the sections cut from ingots. The potential difference is obtained through the diffusion controlled ovens, atoms of phosphorus and boron atoms on the two opposing layers of the cell. The first creates a shortage of electrons, thus creating the second surplus of electrons. From the first p-type silicon is obtained, of the other n-type silicon The junction between the two layers, due to the bombardment of photons (sunlight), tend to separate the electrical charges creating the electric current flows between the two sides of the cell, ie, the two poles (positive and negative) of the cell. Or electrical contact between the bottom of a screen printing paste obtained by Dargent, and the top electrical contact, consisting of a front grille.


The photovoltaic cell is the junction of two thin semiconductor materials (silicon p-type n-type silicon). When a ray of light strikes the cell, the positive charges and negative charges are separated, creating a potential difference. Between the two semiconductor generates a small electrical current. A cell has an area of ​​100 sq mm, the normal insolation (25 ° C 1 kW / m) produces electric current of 3 amperes intensity, voltage 0.5 volts and 1.5 watts of power. Silicon is basically a machine that produces energy, but, like all machines, has loss of efficiency. The modern internal combustion engines to reach 27%, power plants reach 50%. Thus, the polycrystalline silicon has low yields of 12-14%, the yield was 18% monocrystalline and amorphous silicon has conversion efficiency (7%) of the polycrystalline even lower, costs less but has a running time of a module vitaminore polycrystalline, which has a guarantee of life for 25-30 years.


The connection of several cells allows for voltage (volts) higher. Once connected in series / parallel, the 36 cells are encapsulated in a thick EVA (Ethylene-vinyl acetate) and then laminated to a sheet of glass with high resistance, transparency and anti-reflective coating to obtain the form framed by an aluminum frame . So connected the cells to form the form of half a square meter, which produces 50 Wp (for the loss of coupling), at a voltage of 17V (Volts x Amps = Watts). It weighs about 6 pounds, has a thickness of 4 cm. Several modules have a string, and strings together, have a PV array.


The first glimpse of the potential of conducting materials is attributed to Alessandro Volta at the end of 700. The ability to transform light into electricity was possible after the experiments of A. Becquerel in 1839. But the periods of greatest growth were 50 years lera and development of space programs for energy, reliably, and in places without resources. PV technology is now available anywhere: the minicomputers, clocks, light meters and cameras on the photoelectric cells of the gates. The first solar power for electricity production was built in 1982 in Switzerland.

BUILD A SOLAR PANEL - taken by Greenpeace Italy

Material to work with:
-A welder-tipped stylus (pointed), and not rounded, at least 40W so it should not be doing too much pressure on the cell because it is very sensitive to pressure. The soldering iron is easily the cost of 6 euros
A spool-tin of 300 grams, preferably unleaded. Allincirca should cost five euros.
-Ribbon (serves as a conduit to connect the cells one by one): 15 euros for 15/20 allincirca m
-Plastic panel, or any other electrically non-conducting material resistant to weather (will the support surface of the cells and their final location). Size in the number of cells that are assembled
-Pane glass or clear plastic to fit over the previous panel, but more resistant allesterno doing so to leave a thickness between one and other kernel because in between there are cells
-Hot glue gun, the total maximum cost 25 euros, will be used to paste the cells welded to the plastic panel below
-Apply silicon to silicon and syringe the intersections between the upper and lower transparent panel (you have to create watertight uninscatolatura): 4 / 5 euros
- Cables with a diameter depending on the power panel created: virtually no cost, are happy with the electrical home
- Unit cost of 0.049 usd shokty diodes (use them as many as are the cells) are used to scroll the current properly in all individual cells, since each has diversa.Inoltre shape and size do not damage the cells that would otherwise be subject to surges and then malfunctions. Each diode must be antiparallel to each cell.
- A diode, which bear the panel voltage and current delivered by the panel, to be paid in the positive bias (given by the heads of all the solar panel welded after all cells). cost 0.50 eur at local stores. It serves as not to damage the panel while it is charging a battery so to scroll in one sense the current.
- Digital mutimetro capable of measuring V, A, ecccosto ohm 7 / 8 euros
1. Among all the cells you are able to provide (surely there will be of various shapes and sizes as waste) make a selection based on the shape / size cell (be careful not to cut and very delicate as not to break), which bring together all cells with the same characteristics, like size and shape.
2. Cut the ribbon wire of a length suitable to connect two adjacent cells, dissolve the pond above, then saldardo of a cell at a time only on the blue face of the cell (the negative), following the lead of the main cell. Once the process repeated for different cells, lassemblamento proceed in series, ie a negative pole connected to the positive pole of the next and so on up the chain to a chain of 32 cells (each cell has a voltage of about 0.5 V Thus the entire panel will 0.5 x 32 = 16v vacuum, ie without any load connected)
3. Once connected the whole chain of 32 cells, each cell corresponding to a diode connected schotky with silver band toward the positive pole of the cell and the black to the negative pole of the cell (this point is still to be improved as yet I tested it, then I suggest you personally check who engages in work).
4. Once you have a chain of cells with all the Schottky diodes in parallel, each cell must, through the hot glue to fix everything on the panel that will be the base (plastic, etc. ..), then packing or seal with silicone.

5. Test with the multimeter.


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