Traditional sources of energy have one main problem: they cause big damages to the environment and a waste a great amount of resources. In alternative to these ways to produce energy, there are yet other ways to produce it using renewable resources of energy that are obtained thanks to new technologies that cause less damages to the Earth. It is really important nowadays that governmental institutions invest more money on renewable resources of energy such as: solar energy, wind energy, hydropower, geothermal power or biomass power. However, these alternative energy resources are not widely used because there are different obstacles which are blocking their diffusion:

• the resistance of multinational industries (more interested in producing energy using traditional fuels and materials, partly because those industries own the areas in which petrol derivates are produced);
• relevant economic investments in research fields of renewable energy;
• economic costs (resulting from the substitution of less expensive but non-renewable sources of energy with more expensive ones);
• adoption of a very different energetic management system.

 Possible alternative energy sources are: 

1. SOLAR POWER
2. WIND POWER
3. GEOTHERMAL
4. TIDES
5. HYDROELECTRIC
6. BIOMASS ENERGY

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According to WIKIPEDIA , Solar Power is "the technology of obtaining usable energy from the light of the Sun".

This kind of energy nowadays is used to substitute traditional energy in many fields such as producing heat and electricity, above all, especially in remote locations even if its use is being extended in urban areas as well. Another field for the application of solar energy is the desalination of seawater.

Solar power is produced by using solar panels, which are large flat panels made up of many individual photovoltaic cells, that is what is commonly called solar cells which transforms sunlight into electricity. A photovoltaic cell is a non-mechanical device usually made from silicon alloys.

The energy obtained is clean, renewable and cheap. However, this resource can only be used in a very restricted area, which corresponds to those regions that are located between 45° latitude North and South [from Energie rinnovabili]. The reasons for this limited use are due to cloudiness (clouds absorb a big quantity of radiations), to the incidence of solar beams (the more solar beams are inclined, the less energy reaches the ground) and to the atmosphere mass (because of its pressure on the earth surface). The biggest problem is that of its “dilution”,  because in order to collect and transform the solar power into energy one needs very huge spaces. Only in very big areas one can install numerous solar panels and collect huge quantities of energy. Another problem is that of the irregularity of  solar irradiation because of  the alternation of day and night and the alternation of seasons.

As direct energy resource, the heat of the sun cannot be considered as a recent discovery. Only after the energy crisis of 1973, the sun started to be considered as an alternative resource for the production of electric energy. The most used technology is 'photovoltaic conversion', that means the use of semiconductors or other devices that convert solar radiation (photons) directly into electricity. A large number of houses all over the world use solar energy; however, the amount of energy produced by solar panels is very limited.

 In Europe, the biggest photovoltaic power station is in Puglia, extended on 4000 square meters.

Wind power has been using for a long time. In the Middle Ages, for example, in Europe, windmills were used to produce corn. Nowadays, wind energy is used to produce electricity by the use of wind turbines, which are usually tall towers with a propeller on the top. Firstly, the propeller is turned round by the wind and as a consequence the generator produces electricity.

Wind energy is certainly an important alternative energy resource. However, only 1% of world-wide electricity is produced by wind turbines, which can be mainly found in costal areas, at the tops of hills or in open plains, in other words, in places where the wind is strong and regular. In fact, in order to be used the wind speed should be higher than 4m/s and for at least about hundred days a year. Therefore, in Europe wind power is used, above all, in Germany, Denmark, Spain and Sweden where in 2001, for example, 300 power stations were built in depth of the sea. [Wikipedia, 2007]

Normally, wind energy is produced massively in wind farms, which provide electricity to close areas. However, there exist some individual turbines which supply electricity to isolated homes.

In Italy, the exploitation of wind energy began during the 90s, but it became important only several years later, thanks to the efforts of public institutions and private companies which created the first wind farms.

Wind energy is a kind of solar energy because winds are due to global warming. Since warming is not uniform in the different parts of the Earth, masses of air take various temperatures and pressures, expanding their movements to find an equilibrium. Where the pressure is higher, the mass of air moves faster, originating winds.

The power of wind can be used to move props that are able to produce electrical energy if linked to dynamos. The systems employed for this purpose are called 'aerogenerators' and their peculiarity consists in converting directly the kinetic energy of the wind in mechanical energy. Many aerogenerators linked to each other form the so-called "wind farms", which are just power stations where the biggest generators are installed 200 metres far from each others. One type of wind farms are 'off-shore wind farms' which represent a great opportunity for areas with high population density. In fact, it has been estimated that aerogenerators might provide for 20% of the energy requirements of coastal countries. The places chosen for the installations of off-shore wind farms must have three essential features:

1. the speed of the wind must be 7-8 metres per second (it is from 4 to 5.5 metres per second for normal wind farms);
2. the water must be shallow (5-40 meters);
3. the place must be located 3 km far from the coast. 

Wind energy does not produce only electrical energy but hydrogen, too.

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 Etymologically the word 'geothermal derives from the Greek words geo and therme, which respectively mean earth and heat. So its literally meaning is "earth heat".

Geothermal heat provides the force that spins generators and turbines so that they can produce electricity without polluting the environment. For this reason it is a good alternative source of energy and it is produced in over 20 countries around the world such as Iceland (producing 26.5% of its electricity from geothermal sources in 2006), the United States, Italy, France, New Zealand, Mexico, Nicaragua, Costa Rica, Russia, the Philippines, Indonesia, China and Japan.[Wikipedia, 2007]

The problem with this alternative source of energy is that only consumers who are located close to the area of production can take advantage of the electricity produced.