Water Power

There are three types of water currents (the movement of water on the Earth’s surface):

  1. river currents
  2. tidal currents
  3. marine current

High tides, currents and waves produce mechanical energy. This energy can be transformed into electrical energy by means of various technologies.

Fig. 4.1
High tides and low tides are different from all the other energy sources as they are the result of the «Earth–Moon-Sun» system. It is well known that the influence of the Moon on Earth causes the oceanic high tides and low tides to appear. Therefore, the level of the marine waters changes all along the shoreline. Water level changes two times a day, ‘covering’ and ‘clearing’ a part of the littoral, consequently, creating basins.

Water currents, formed in these basins, can be used in order to cause the hydroturbines to move. As the latter are connected to generators, they can produce electrical energy. The higher the high tides, the more energy is produced. The technology which uses this source, resembles the hydroelectric technology with low-speed currents.
The immense ocean waves possess massive amounts of energy, but this energy is difficult to exploit efficiently and cheaply. The conversion of hydraulic energy into electrical energy is non-polluting, involves low maintenance costs and represents a long-term solution. However, it causes some ecological problems.
The principle of obtaining electrical energy by using the power of water is the following: water is collected in a reservoir and then, canalised through an inlet pipe directly into the turbine. The vertical fall of water creates the necessary pressure at the lower end of the inlet pipe in order to actuate the turbine. There is a relationship of direct proportionality between the resulting energy, the volume flow rate and the fall of water.
Figures 4.1, 4.2 si 4.3 present __hydroelectric power stations.
The approximate power of a hydroelectric power station, is given by the following relation: P [ kW ] = Q [m3/s]•H [m]•7 [kN/m3] , where:Q- volume flow rate;H-height of fall;
7 [kN/m3]-coefficient resulted from efficiency, turbine resistance and gear transmission.
Types of hydroelectric power stations:
common river hydroelectric power stations, used exclusively to produce the electrical energy
pump-accumulating hydroelectric power stations
tidal power stations


Fig. 4.2
Hydroelectric power stations have a series of positive influences on the environment, for example
  1. no discharges with a negative impact on the environment
  2. adjustment to the river’s volume flow rate
    no possibility of inundating the localities situated downstream the power station
  3. development of the irrigation system
Fig. 4.3

Hydroelectric power stations also have a series of negative influences on the environment, for example:

  1. elimination from the agricultural system of some fertile areas
  2. the change in flora and fauna
  3. the change in the hydrologic regime of the rivers and the reduction of the downstream volume flow rate