Hydro power uses water to generate electricity. Most hydro electricity is generated from fresh water, but there is also marine-generated electricity that uses the movement of waves.
Rivers flow from areas of higher elevations (height above sea level) towards lakes or oceans, and as the water moves, it gains kinetic energy. Considering that the water is contained within the confines of a river bed, all the energy is also contained (unlike solar energy, which is very dispersed). By containing rivers through structures (hydro lakes formed by damming a river), we can increase the potential energy of water.
As the water flows through the dam in a controlled manner, the water rushes over turbines that spin, and the kinetic energy is used to generate electricity. Compare running water from a tap (an undammed river) and filling up the basin and pulling the plug (a dammed river forming a lake) – you can see that there is greater energy released from the basin filled with water than just running a tap.
New Zealand already has a number of hydro electricity power plants, and most of our electricity is generated this way. This benefits our country not just in the generation of power but also because hydro power is a renewable resource, and as long as there is enough water in the rivers and lakes, we can generate power. Hydro power also does not release pollutants into the atmosphere or surrounding area, thus making it environmentally friendly.
One of the drawbacks to hydro power is the damming process. This changes the natural flow of the river and is a problem for local plant and animal species.
While some people like the recreational aspects of a lake that has been created from damming water, others will argue that altering the river’s flow is harmful because it can lead to potential flooding, migratory fish can no longer get past the dam, and it also has effects on the ecology of that area.
With an increase of public awareness on how a dam may affect an area, newly proposed dams must go through rigorous planning procedures where members of the public are given opportunities to be heard.
Generating power from waves is still a relatively experimental technology. The underlying idea is that a ‘hollow’ power plant is positioned in alleys off the coast of beaches. Each time a wave enters the chamber, the water pushes air upwards, which drives a turbine. The turbine is attached to a generator, which transforms kinetic energy into electricity.
A fact sheet on marine energy from the NZ Energy Efficiency and Conservation Authority