For the last decade interest in these power sources constantly increases as in many respects they are unlimited. As supply of fuel becomes less reliable and more expensive, these sources become more and more attractive and more economic. Increase in prices for oil and gas served as the main reason of that we paid the attention to water, a wind and the Sun again.
Water from a reservoir arrives via the long direct channel called by the pressure head pipeline down and goes to horizontally rotating turbine blades. The vertical shaft of the turbine is connected to the generator block. At typical station many turbine and generating units are used. The efficiency quite often makes about 60-70%, i.e. 60-70% of energy of the falling water will be transformed to electric energy.
The problem of regulation of all system of power plants is more difficult. Also as on tidal stations, there are here periods when generators develop not enough energy or absolutely it is not made. In such time it is necessary to increase somewhere development of current by usual power plant to cover need for it.
From the point of view of environment and a sustainable development these alternative sources of electricity are quite reliable. Unfortunately, they do not solve a problem in any way reductions of reserves of crude oil which is still necessary for transport.
Heaps of rainfall, invisible till time, which become visible only during low standing of water in a reservoir, - not the only reason for which many oppose construction of dams. There is also other, more important reason: after filling of a reservoir under water there are valuable lands which are lost forever. Also valuable animals and plants, and it not only overland types disappear; the fishes occupying the river which is partitioned off by a dam too can disappear as the dam blocks a way to spawning places.
The person, certainly, has impact on the environment surrounding it, however in the nature there are natural counterbalancing mechanisms which support Wednesday and the communities living in it in an equilibrium state when all changes happen rather slowly. Nevertheless in many cases economic activity of the person breaks the balance created by these mechanisms that leads to fast changes of conditions of environment with which neither the person, nor the nature cannot successfully cope. The traditional energy production giving huge quantities of pollutants of water and air - one of types of such activity of the person.
Physical consequences. When we look at inflow with their frightening energy, we should think of impact on environment of tidal basins. Let's concentrate on physical changes which can happen from the sea party of tidal power plant
Accumulation of too large amount of rainfall in a reservoir can be prevented partially. The erosion and transfer of rainfall represent natural and continuous processes, however agricultural works, laying of roads construction of houses and deforestation – all this accelerates erosive processes, baring the soil. Careful control of a condition of the soil promotes reduction of amount of the detrital material which is carried away by streams and by that prevents fast accumulation of a deposit in reservoirs.
In search of alternative energy sources in many countries considerable influence is given to wind power. The wind served mankind throughout the millennia, providing energy for sailing vessels, for grind of grain and pumping of water. Now the main place is taken by power generation. Already today in Denmark wind power covers about 2% of needs of the country for the electric power. In the USA about 17 thousand vetroagregat with a general power up to 1500 MW work at several stations. Wind power devices are issued not only in the USA and Denmark, but also Great Britain, Canada, Japan and some other countries.
On the river the dam for a delay of waters of high inflow is constructed. When tidal waters recede, the water detained by a dam is issued to the ocean via pear-shaped turbines under a dam and the electric power is developed. However it is possible to develop the electric power both at outflow, and at inflow.