ABSTRACT
Hydropower generates electricity by using water, and it is one of the cheapest and eco-friendly ways, especially the use of small hydropower plants. It exploits the vast global water cycle: the water constantly evaporates from lakes and oceans, forming clouds, precipitating as rain or snow, and then flowing back down to the oceans. In this way, it is possible to use water’s potential energy in its natural flow to produce power. The water cycle is an endless, constantly recharging system, and therefore, hydropower is considered a renewable energy. As stated by International Energy Agency (IEA) in 2008, the total installed capacity of hydropower is about 850 GW, and hydro sources produce about 3000 TWh of electricity annually, supplying about 15% of total world’s electricity. The IEA projects that hydro will grow up to 63% for the period 2002–2030. The agency predicts that new hydro plants will continue to be built, not at a rate high enough to maintain hydro’s current percentage of total electricity generation. As a result, hydropower is projected to fall to 13% by 2030, from the present 15%. It is estimated that two-thirds of the world’s economically feasible potential is still to be exploited and it is mainly concentrated in developing countries such as Africa, Asia, and South America. China is using only about one-quarter of its huge hydro potential of 450 GW, and it is the main developer of hydro technology today. Figures from the Chinese government suggest that it will add more than 12 GW of new capacity each year until 2020 to reach 300 GW. This entry highlights the basics of different hydro technologies, with a special focus on small hydro run-of-river plants.
