Hydropower: Generate Energy with Rivers and Ocean Tides - dummies

Hydropower: Generate Energy with Rivers and Ocean Tides

By Alecia M. Spooner

An important source of alternative energy is hydropower: converting the flow of rivers and ocean waves and tides into electricity through dams and turbines. The best part about both of these water sources is that they’re 100 percent renewable.

Generate energy with hydropower dams

All rivers and streams flow downhill across the land surface. Humans can convert this motion of water, which is a form of kinetic energy, into electricity by building dams across rivers. Each dam directs the water flow of the river through a system that generates electricity. This figure shows a simple hydropower dam system.


So how exactly does a dam generate electricity? The dam creates a large lake, or reservoir, of water. The river water then flows from the reservoir through the dam’s penstock (control gate or pipe) into a turbine or large water wheel. As the water pushes the turbine, the kinetic energy is transferred into a generator that converts it into electric energy.

Electric companies can then send the electric energy along wires to provide power to industries or households. Many regions around the world currently depend on hydropower dams to produce electricity.

The Three Gorges Dam in China illustrates both the advantages and the disadvantages of using hydropower energy. The main advantages are that the dam provides China with huge amounts of renewable, clean energy with low monetary costs (other than the initial construction costs). Unfortunately, though, when the Three Gorges Dam was built, it flooded extensive watershed regions, drowning whole villages, whose populations had to relocate above the reservoir waterline.

The building of the dam also destroyed millions of acres of habitat and, thus, had negative effects on biodiversity. The verdict is still out on whether meeting the growing energy needs of China’s people through a clean and renewable energy source (hydropower) is worth the destruction of habitat and the other negative outcomes.

Because many people criticize large hydropower dams for the environmental damage they cause (such as destroying habitat and changing the nature of the river ecosystem), some scientists have started developing new technologies that apply the same principles to capture river energy as a traditional dam without causing as much damage.

For instance, small floating systems such as microhydropower dams and run-of-the-river systems capture kinetic energy from flowing rivers without causing dramatic ecosystem disruption. These smaller hydropower systems use tiny turbines to capture the natural flow of water instead of creating a lake or causing flooding. The smallest systems sit under the surface of the water and have very little impact on the environment around them.

Small-scale systems such as these are examples of what the future of hydropower may look like.

Generate energy with ocean tides and waves

The oceans are another source of hydropower energy. Twice a day as the Earth rotates, the ocean waters move into and away from the coast in what you know as tides. To take advantage of this water flow, scientists have come up with a way to convert the kinetic energy from the tides into electric energy, similar to the way they use river hydropower systems (or dams).

When water flows toward the shore with the incoming tide, it flows through a tidal energy system, turning a turbine that generates electricity. When the tide shifts and flows in the opposite direction, away from shore, the tidal energy system again captures the energy with a turbine and converts it into electricity.

The main advantage of using ocean tides for energy is that tides and waves are a constant, unchanging, clean source of energy. The main disadvantage is that tidal energy systems may impact the environment by changing the flow of water into shoreline and estuarine ecosystems.