Hydroelectric energy is a clean, alternative, and renewable energy source that exploits the transformation of gravitational potential energy (it is the energy that a body possesses at a certain distance from another body due to the presence of the force of gravity), possessed from a certain mass of water at a certain altitude , in kinetic energy upon overcoming a certain difference in altitude. The hydroelectric power station uses large masses of water obtained from rivers or lakes, thanks to penstocks.


There are three types of control panels:

  • The first, called a run-of-river hydroelectric power station , is the most widespread and has continuous operation because it exploits the difference in altitude between the upper and lower water surface, the so-called jump. This type of control panel works 24 hours a day.
  • The second, called a reservoir hydroelectric power plant , exploits the difference in height between an artificial lake with natural inflow and a power plant located further downstream. The water flows through penstocks or tunnels to turbines in the downstream hydroelectric power plant. These power plants are used in periods when there is a greater energy requirement.
  • The last one, called a pumped hydroelectric power station , conveys the water into a mostly artificial basin located upstream. This usually happens at night in order to exploit electricity at times when energy needs are reduced. On the contrary, when energy needs increase, water flows from the reservoir to the turbines of the hydroelectric power plant.

Power plants

The second and third examples of power plants exploit the large drop heights available in mountain areas, while the first exploits river courses which must however guarantee a massive and stable mass of water at all times of the year.

The water is brought downstream through penstocks so as it falls it transforms gravitational potential energy into kinetic energy. The water arrives at the turbine, which transforms the kinetic energy into mechanical energy, and then transforms into electrical energy at the output of the alternator.

The advantages of hydroelectric energy are many. Hydroelectric energy production does not cause gaseous or liquid emissions that can pollute the air or water. Furthermore, water is an abundant, free source and has an electricity production efficiency that exceeds 80%.

The main disadvantages consist in the fact that to build hydroelectric power plants it is sometimes necessary to modify the original layout of the territory and the natural regimes of the waterways of rivers and streams, in some cases causing environmental impacts on ecosystems and economic impacts on other agricultural or industrial.


Another disadvantage is that large reservoirs could change the climate of neighboring places , making it milder. Another negative aspect on the fauna concerns the fish which, going up the rivers to lay their eggs, find barriers in their path which prevent them from going to complete their spawning, thus risking the extinction of a species.

What is about to happen in New York, but also throughout the USA , could be an epochal turning point regarding the release of toxic substances into the atmosphere, mainly derived from the coal-fired power plants still present on US soil. According to new laws from the EPA (American Environmental Protection Agency), factories powered by fossil fuels are destined to close.

This is not a certain fact but nor an unexpected fact because some famous journalistic houses already announced it. The costs for the United States are not insignificant but the environment will certainly benefit. The city of New York is aiming for clean energy, such as the reuse of waste water which, with expensive purification and filtering, would obtain fuel from the mud to be used in heating systems, butanol from the algae in the canals and from the final purification treatment of water methane.


Hydroelectric energy was one of the first sources used to illuminate Italy since the early 1900s; at the end of the 1950s the contribution of hydroelectric energy amounted to almost 80% of the energy produced within the country. Now in Italy the production of electricity occurs mainly with the use of non-renewable energy sources (such as fossil fuels purchased mainly abroad) and to a lesser extent with renewable sources (such as geothermal or wind hydroelectric systems).

Italian electricity needs are greater than the energy produced within the State, so we are obliged to buy it abroad; this is then passed through international power lines.

Italian hydroelectric power plants are located mainly in the Alps and some in the Apennines, accounting for 15.8% of annual energy needs. Considering all energy production that uses renewable sources, it constitutes up to 23.4% of total national production.

At the European conference in Berlin (2004), the EU established its objectives regarding renewable energy sources . The result to be achieved is to cover 20% of total energy consumption with these sources by 2020.

Renewable energy

Another renewable energy, unfortunately still being tested, is marine energy . This, as I have already said, is still being tested because the sea, being salty, creates system problems by damaging the moving mechanical parts and thus making maintenance expensive.

If Italy managed to use this energy in the future it could produce as much electricity as six nuclear power plants. There are many ongoing studies, some still purely theoretical, which involve the conversion of various types of energy present in the sea.

One of these experiments exploits wave energy by converting it into electrical energy . Another includes the use of tides . The moon and, although with less force, the sun influence the lowering and rising of sea levels. Where the difference in height between the maximum and minimum height is consistent, this type of marine “exploitation” can have a better expansion.

Another experiment exploits sea currents, again converting them into electricity. These currents can be compared to large rivers flowing next to each other. These currents, possessing kinetic energy, can be exploited with the same principle as wind energy . The possibility of exploiting the energy of the solar gradient is also being studied, i.e. exploiting the difference in thermal gradient between the surface water heated by the sun and the colder water found in the depths of the sea.

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