Flat reservoirs are usually great on the area change an environment in considerable territories. The sanitary condition of reservoirs worsens: sewage which were taken out by the rivers earlier, collect in reservoirs, it is necessary to apply special measures to washing of beds of the rivers and reservoirs. The construction of hydroelectric power station on the flat rivers is less profitable, than on mountain, but sometimes it is necessary, for example, for creation of normal navigation and an irrigation.
Though solar energy is also free, receiving electricity from it is not always rather cheap. Therefore experts continuously seek to improve solar elements and to make them more effective. The new record in this regard belongs to the Center of progressive technologies of the Boeing company. The solar element created there will transform 37% of the sunlight which got on it to the electric power.
About 1/5 part of the energy consumed around the world is developed on hydroelectric power station. It is received, transforming energy of the falling water to energy of rotation of turbines which in turn rotates the generator developing electricity. Hydrostations happen very powerful. So, the station to Itap on the Parana River on border between Brazil and Paraguay develops the power of do13 000 million kW.
It is necessary to notice that use of sources of alternative, renewable types of energy can reduce rather effectively percent of emissions in the atmosphere of harmful substances, that is to some extent solve one of important environmental problems. Energy of the sea can be ranked as such sources with good reason.