Power from Water and Earth's Heat
Beyond the sun and wind, there are other powerful renewable energy sources we can harness. Two of the most reliable are hydropower, which gets its energy from moving water, and geothermal energy, which comes from the heat deep inside the Earth.
Hydropower: Energy from Moving Water
A hydroelectric power plant captures the energy of falling or flowing water to generate electricity. Most hydropower comes from building a dam on a river.
How it works:
1.A dam is built to block a river, creating a large artificial lake called a reservoir behind it. The water in the reservoir now has a lot of gravitational potential energy.
2.The water is allowed to flow from the reservoir through a large pipe called a penstock. As it flows downwards, its potential energy is converted into kinetic energy.
3.The fast-moving water pushes against the blades of a turbine, causing it to spin.
4.The spinning turbine is connected to a generator, which produces electricity.
Advantages:
It is a very reliable and consistent source of power. It's not intermittent like solar and wind; a dam can generate power 24/7.
Once the dam is built, the electricity is very cheap to produce.
The reservoir can also be used for recreation, flood control, and water storage.
Disadvantages:
Building a large dam is extremely expensive and can have a huge environmental impact, flooding a large area of land and changing the river's ecosystem.
Dams can block the migration of fish, like salmon.
It is geographically limited; you need a large, powerful river in a suitable location.
Geothermal Energy: Energy from Earth's Heat
The word geothermal comes from the Greek words geo (Earth) and therme (heat). Geothermal energy is the thermal energy that is generated and stored within the Earth's interior.
How it works:
1.In tectonically active areas, magma (molten rock) is close to the surface. This magma heats up underground rock and water.
2.Wells are drilled deep into the ground to reach these reservoirs of hot water and steam.
3.The hot, high-pressure steam is brought to the surface and used to spin a steam turbine.
4.The turbine is connected to a generator, which produces electricity.
5.The used steam is often cooled and pumped back underground to be reheated.
Advantages:
Like hydropower, it is a very reliable and consistent source of clean energy.
Geothermal plants have a very small physical footprint on the land.
Disadvantages:
It is highly geographically limited. It is only practical in places with volcanic or tectonic activity, like Iceland, California, and parts of Italy.
The startup costs, especially for drilling, can be very high.