ACCENDI L’ACQUA
Sviluppo sostenibile: l’energia idroelettrica.
ACCENDI L’ACQUA
Photovoltaic: energy from sun
Energetic consumpiotns
Every object and every machinery need energy to work and produce. The combustion of carbon, sulphur oxides and hydrocarbons to produce energy causes environmental modification and the rise of breathing diseases. The needs of a three-people family and, consequently, their energetic consumptions have doubled in the last twenty years reaching 3000 kWh/year; that’s equal to a 520 £(1.000.000£) a year(3000kWh/0,17£).
Solar energy
The earth receives a luminous flux from the sun which enables life process, creates winds, makes plants grow, decomposes animals and vegetable remains. The energy which hits the earth can be enough to produce all energetic requirement (an example: one square meter of the Sicilian land receives solar energy equal to the energy contained in a petrol barrel).
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Kyoto protocol
Governments have established to limit the dependence on not-reusable power source in the period from 2001 to 2010. To this purpose, governments have been reciprocally engaged to reduce of one fifth the production of CO2. In order to obtain that, there is only one possibility: the share of reusable power source needs to grow, double the actually share of 6% to 12%.
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What photovoltaic is?
The photovoltaic technology allows to transform directly solar light into electric power without any movement mechanism. It uses the so-called photovoltaic effect which is based on propriety of some semiconductor materials ( that is electric conductor and insulator at the same time, lie a silicon), which are be able to generate electricity when they are hit by a solar radiation.
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Working of a photovoltaic cell
The photovoltaic cell is the union of two thin semiconductor materials. When a light ray hits the cell, protons divide from neutrons creating a potential difference. This generates a small electric current between the two conductor.
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Photovoltaic module
The connection of more cells allows to obtain higher voltages.Once the 36 cells are linked in asuccessionorparallel connection, they are encapsulated in some thickness of EVA (Ethyl-Vinyl-Acetate) and
thenlaminated on a pane of high-resistance, high-transparency and anti-reflection glass to obtainthe moduleframed by an aluminium frame. Linked like that, the cells form a module of a half squaremetre whichproduces 50Wp (because of the connection leaks), at a voltage of 17V(Volts x Amps = Watts). It weighs about 6 kilograms, it has a thickness of 4 centimetres. Several modules form a streak, and several streaks together form a photovoltaic field.
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Historical evolution
The first intuition of the potential of conductive materials goes back to Alessandro Volta, at the end of the XVII century. Turning light into electric energy was possible after A. Bequerel’s experiments in 1839. But there were periods of a greater expansion, such as the 1950’s and the age of space programs development to gain energy reliably in places with no resources. Nowadays the photovoltaic technology is available everywhere: mini-calculators, watches, cameras’ exposure metres and gates photoelectric cells. The first photovoltaic plant was built in Switzerland in 1982..
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Italian paradox
There are at least two great contradictions about photovoltaic in Italy:
Production of photovoltaic market
The world market of photovoltaic energy increased fivefold in ten years (1990-2000), increasing from 45 MWp to 290 MWp.
The most elevated growths are in Japan, the USA and Germany, which not only stimulate the plant installation with subsidies, but also pay for the energy introduced into the system a higher price than the sale one.
In Italy, at the expiry of the first plan “10.000 photovoltaic roofs”, a new project for 50.000 plants is going to start in 2007.
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Ecology of a photovoltaic plant
The photovoltaic station can be used without a territorial waste (on the roofs) or on panels with other functions (acoustic barriers, sunbreaker, cantilever roof .
It’s a material which can substitute the finishing materials of buildings (tiles, corrugated slabs).
It has the big advantage to produce energy where there is need, avoiding dispersion wastes through the wires.
It doesn’t produce any kind of pollution either during his working cycle or because of the disposal of its components (silicon, glass, iron, copper, plastic, aluminium).
At last, its use reduces the CO2 production of the boilers or thermoelectric power plants (1 kWh of electricity produces 0,53 kg of CO2). The FV technology has a great potential in the future: costs reduction, improvements of conversion efficiency.
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