Sustainable Energy and Smart Grids: Breakthrough in Thinking, Modelling, and Technology

Hydro energy or hydroelectricity is the production of electrical energy by using the gravitational force of falling or flowing water. The best-known form of hydroelectricity is the energy produced in turbines driven by the water from a reservoir behind a dam in a river. However, on a smaller scale, hydroelectricity can also be generated by putting turbines in a river with flowing water. Hydroelectricity is still the most widely used form of sustainable energy. The growth of this source is limited (to roughly 3 per cent per year), probably because of worries about the environmental impact of building dams in rivers and because the most attractive locations are already being used. However, in emerging economies like Africa and South America, a big increase in hydroelectricity is possible because many rivers have not yet been exploited.

The power from a flow of water can be expressed as

$P=Qgh$

where $Q$ is the mass flow (in kg/s) of the moving water, $g$ is the gravitational constant, and $h$ is the height difference between the water behind the dam and the location of the turbines. This shows that the growth of hydroelectricity is mainly profitable at locations with a large height difference and with a large mass flow of water. Among the attractive properties of hydroelectricity from a dam are the fact that hydroelectricity can be well-controlled and that the reservoir can be used to store energy. These reservoirs can also be used for pumped storage, using energy to pump water when more energy is available than is needed and using this energy when necessary. These properties make hydroelectricity a very suitable generation source for smart grids.