What is renewable energy? Definition and examples
Renewable energy comes from a source that never runs out. In other words, its source lasts forever. Renewable energy comes from natural sources that Mother Nature continuously replaces on a human timescale.
The term contrasts with non-renewable energy, which comes from sources that eventually deplete. In other words, we can use them up until there is no more left.
The Natural Resources Defense Council or NRDC has the following definition of the term:
“Renewable energy, often referred to as clean energy, comes from natural sources or processes that are constantly replenished.”
“For example, sunlight or wind keep shining and blowing, even if their availability depends on time and weather.”
Alternative vs. renewable energy
Do not confuse the term with ‘alternative energy.’ Alternative energy refers to an energy source that is an alternative to using petroleum, natural gas, or coal. In other words, an alternative to fossil fuels. While ‘alternative’ means ‘instead of,’ ‘renewable’ means it does not deplete.
Sometimes, however, the two terms may refer to the same energy source. Wind energy, for example, is an alternative to using coal. Also, we never run out of wind, i.e., we could never use all of it up. Therefore, wind energy is both an alternative and renewable energy source.
While alternative energy, by most definitions, does not harm the environment, this is not the case with renewable energy.
An article on the website of Pennsylvania State University says the following regarding the two terms and the environment:
“By most definitions alternative energy doesn’t harm the environment, a distinction which separates it from renewable energy which may or may not have significant environmental impact.”
Renewable energy – types
Renewable energy includes wind power, hydropower, geothermal energy, and biomass power. Solar energy is also a type of energy whose source never runs out.
Wind power describes the process by which we use wind to generate electricity or mechanical power. We also use the term wind energy.
Wind turbines convert the wind’s kinetic energy into mechanical power. We can subsequently use this mechanical power to pump water, grind grain, or generate electricity.
Regarding this type of renewable energy, WindExchange.Energy.gov, part of the US Department of Energy, writes:
“Wind turbines can provide energy for onsite use as well as for export for sale. The energy needs will determine the size of the turbine.”
Solar energy or solar power works by capturing energy from the sun and converting it into electricity. In other words, converting sunlight into energy that we can use in our homes, businesses, and infrastructure.
Infrastructure refers to roads, railway networks, sewers, underground water and natural gas systems, etc. Street lighting, for example, is part of our infrastructure that solar energy can supply with electricity.
When photons hit a solar cell, they loosen electrons from their atoms. If we attach conductors to the cell’s positive and negative sides, we create an electrical circuit.
Electrons generate electricity when they flow through such a circuit.
A solar panel consists of many cells. When we have many panels or modules that we wire up together, we call it a solar array.
The amount of energy you can generate depends on how many panels you deploy.
Solar energy is among the most popular of the renewable energy sources.
According to USA Today, solar energy was the fastest-growing source of power globally in 2016. It accounted for nearly two-thirds of net new capacity worldwide.
Geothermal energy involves using the Earth’s internal heat. We can use, for example, hot rock a few miles beneath our planet’s surface to generate energy. Even deeper down, there is molten rock, i.e., magma, which we can also use to generate energy.
The upper ten feet of the Earth’s surface maintains an almost constant temperature of between 10° and 16°C (50° and 60°F).
We can use geothermal pumps to tap into this resource to regulate the temperature of buildings.
Renewable Energy World explains how we use geothermal pumps:
“A geothermal heat pump system consists of a heat pump, an air delivery system (ductwork), and a heat exchanger-a system of pipes buried in the shallow ground near the building.”
“In the winter, the heat pump removes heat from the heat exchanger and pumps it into the indoor air delivery system. In the summer, the process is reversed, and the heat pump moves heat from the indoor air into the heat exchanger.”
“The heat removed from the indoor air during the summer can also be used to provide a free source of hot water.”
Hydropower is the electricity we can generate by using the energy of water when it is moving. Moving water exists, for example, in rivers. The oceans’ tides and waves also consist of moving water. Humans today use many forms of moving water to generate electricity.
In 2015, 16.6% of the world’s total electricity came from hydropower. Also in 2015, hydropower represented 70% of all renewable energy that we converted into electricity.
Wikipedia says the following about energy from water:
“Since water is about 800 times denser than air, even a slow flowing stream of water, or moderate sea swell, can yield considerable amounts of energy.”
Biomass is fuel that we have developed from organic materials. Scrap lumber, forest debris, and manure, for example, are materials that we use as biomass fuels. We also use certain crops and household waste as biomass fuels.
Biomass is a renewable energy because its fuel sources, i.e., waste residues, never run out. If we properly manage forests and agricultural land, we will always have trees and plants as fuel sources.
ReEnergy Holdings says the following about biomass power:
“Biomass power is carbon neutral electricity generated from renewable organic waste that would otherwise be dumped in landfills, openly burned, or left as fodder for forest fires.”
“When burned, the energy in biomass is released as heat. If you have a fireplace, you already are participating in the use of biomass as the wood you burn in it is a biomass fuel.”
Existing on just renewable energy
Is it possible for a country to exists purely on renewable energy? A few years ago, some people said it was not, and that it would never happen.
However, many countries have adopted plans that are taking them in that direction.
Iceland, for example, already gets eighty-five percent of its electricity from the Earth’s heat. Its electricity depends 100% on geothermal and hydropower. Norway gets approximately 98% of its electricity from renewable energy.
Alternative Energy says regarding achieving a 100% renewable energy status:
“If you think 100% renewable energy will never happen, think again. Several countries have adopted an ambitious plan to obtain their power from renewable energy.”
Scientists from the University of Leiden in The Netherlands explained recently that renewable energy takes up lots of space. It takes up significantly more space than fossil fuel or nuclear energy.
If we built giant wind and solar farms in the Sahara desert, we could generate more electricity than the world needs.