Harnessing the Sun and the Wind
Our main energy sources, fossil fuels, are non-renewable and cause pollution. To create a sustainable future, we are increasingly turning to renewable energy sources. A renewable resource is one that is naturally replenished on a human timescale or is essentially inexhaustible. Two of the most promising renewable resources are the sun and the wind.
Solar Power: Energy from the Sun
The sun is a gigantic nuclear fusion reactor that bathes our planet in a huge amount of radiant energy every day. We can capture this energy and turn it into electricity using photovoltaic (PV) cells, which are also known as solar cells.
How it works: Solar cells are made of special materials called semiconductors, like silicon. When sunlight (which is made of particles called photons) strikes the solar cell, the photons knock electrons loose from the silicon atoms. These free electrons are then forced to flow in one direction, creating an electric current. This direct conversion of light into electricity is called the photovoltaic effect.
Advantages:
It is completely clean; it produces no greenhouse gases or air pollution.
The fuel source (sunlight) is free and abundant.
It is very versatile and can be used on a small scale (a single house) or a large scale (a huge solar farm).
Disadvantages:
It is intermittent. It only works when the sun is shining, so it doesn't work at night or on very cloudy days. This means it often needs to be paired with energy storage, like batteries.
Wind Power: Energy from the Air
Wind is simply the movement of air, caused by the uneven heating of the Earth by the sun. Wind contains a lot of kinetic energy, and we can capture it with wind turbines.
How it works: A wind turbine works like a fan, but in reverse. Instead of using electricity to make wind, it uses wind to make electricity. The wind pushes on the large blades, causing them to rotate. The rotating blades are connected to a generator, which converts the mechanical energy of the spin into electrical energy.
Advantages:
It is also a clean energy source with no greenhouse gas emissions.
The land around wind turbines can often still be used for farming.
Disadvantages:
It is also intermittent. It only works when the wind is blowing at the right speed (not too slow and not too fast).
Some people find the large turbines to be noisy or unsightly.
Turbines can be a hazard to birds and bats.
Both solar and wind power are growing rapidly around the world as we seek cleaner ways to power our lives.