What Is Renewable Energy?

There is a lot of talk nowadays about the importance of switching from traditional fuel sources, such as coal and oil, to renewable energy. But, what exactly is renewable energy and what form does it take? There is some debate among experts as to what exactly qualifies as a renewable energy source but let’s outline the basic rule before we delve into examples.

Renewable energy is energy that can be replenished as fast or even faster than it is consumed. In other words, we will never run out of that source. Fossil fuels are not renewable because we have a finite amount. Eventually, we will run out of oil, for example, because it takes hundreds of millions of years to form and we are burning through it at an extraordinary pace. If you look at wind energy or solar energy, however, these are renewable because we will never exhaust our supply of wind or sunlight no matter how much energy we generate from them.

Most people equate renewable energy (also known as sustainable energy) with clean energy. Clean energy simply means the energy source does not require the use of hazardous chemicals and does not emit greenhouse gas emissions. However, biogas and nuclear energy are both ‘clean’ energies but are not usually considered renewable because of their chemical dependence.

So, which energy sources are renewable? Here are some of the most common renewable energy sources and how they function.

Solar Power

You have probably heard of solar power and many of you will have also seen solar panels attached to the roof of buildings. When the sunlight hits the panels, the electrons within the wafer thin layers of silicon in the panel start to move around. Electricity is then created as a direct current (DC). In order for us to use it, it must go through an inverter and become an alternating current (AC). It is finally fed into the grid and sent to our homes and businesses.

Wind Power

Once again, you have probably heard of wind power and seen giant wind turbines in fields or out in the sea. Humans have been harnessing the wind for millennia. From the earliest sailboat and windmills, right up to modern turbines. As the blades of the turbine are blown around by the wind, they power a generator within the turbine that creates electricity. While wind power is not the most reliable energy source, energy storage technologies are making it easier to store wind for later use.


Geothermal energy is a way of harnessing the heat that the Earth naturally produces and turning it into electricity. At the core of the Earth, the temperature is around 5,430°C, but you don’t need to go that far to find enough heat to generate energy. Even just two metres deep, the Earth is consistently warm. The heat is extracted from the ground using water pumps and then separated from the water. The water is then sent back into the ground to heat back up in a clean and renewable cycle.


Biomass harnesses the power of organic materials found in the natural environment. Dead leaves, grass clippings, wood shavings, and even animal dung can all be used to generate biomass electricity. Vegetable oil and recycled grease and animals fats can also be used to create biodiesel, which powers vehicles and is being increasingly adopted for public transport in cities. Biomass is not entirely clean, as it does release some greenhouse gases. However, it is completely renewable and scientists are working on ways to reduce its carbon footprint.