Updated: February 2, 2023
Renewable energy refers to power sources that are endless. Some types of renewable energy, like wind and solar power, come from sources that are not depleted when used. Others, like biomass, come from sources that can be replenished. Common types of renewable energy are wind, solar, hydropower, biomass and geothermal.
Renewable energy has two advantages over the fossil fuels that provide most of our energy today. First, there is a limited amount of fossil fuel resources (like coal, oil and natural gas) in the world, and if we use them all we cannot get any more in our lifetimes.
Second, renewable energy produces far less carbon dioxide (CO2) and other harmful greenhouse gases and pollutants. Most types of renewable energy produce no CO2 at all once they are running. For this reason, renewable energy is widely viewed as playing a central role in climate change mitigation and a clean energy transition.
Renewable vs. carbon-free
Most kinds of renewable energy are also “carbon-free”: they do not emit CO2 or other greenhouse gases into the atmosphere. Because of this, and because renewables like wind and solar power are so popular in climate activism, the terms “renewable energy” and “carbon-free energy” are sometimes confused. But not all renewable energy is carbon-free, and not all carbon-free energy is renewable.
Biofuels and bioenergy are renewable: we can regrow plants that we burn for fuel. But they are not necessarily carbon-free. Growing plants absorbs CO2; burning plants releases CO2. The total impact on CO2 in the atmosphere depends on how sustainably the bioenergy is produced.
Nuclear energy is carbon-free: a nuclear power plant does not emit any CO2, or any other greenhouse gases. But it is not renewable. Nuclear reactors use uranium, and if we run out of uranium, we can never get it back.
Transforming the electric grid
Certain forms of renewable energy can serve as fuel for vehicles (like biofuels) or provide heating and cooling for buildings (like geothermal systems). However, most renewable energy is used to make electricity.
In 2020, renewable energy accounted for more than 28% of the world’s electricity, and this percentage is increasing annually.
Around 60% of global renewable electricity comes from hydropower, a technology that’s been in use since the early days of electric grids. Nonetheless, wind and solar power are currently experiencing the most rapid growth in the renewable energy sector.
Renewable energy brings both significant challenges and promising opportunities to the realm of electricity generation. Certain sources of renewable energy, like wind and solar, exhibit a “variable” nature, meaning the amount of electricity they produce fluctuates based on the availability of wind or sunlight. This variability can pose issues for those managing the energy system, especially when the electricity needed doesn’t align with the wind or sun conditions.
Another hurdle arises from the fact that the best locations for producing renewable energy often differ from the areas that actually use the electricity. This geographic disparity presents a challenge in getting energy from where it’s generated to where it’s needed.
To accommodate these challenges, incorporating more renewable energy into our power grids will necessitate additional adjustments. These include the implementation of enhanced energy storage, backup power sources, strategies to align electricity usage with times of peak generation, and the development of infrastructure for transmitting power over long distances.
A growing source of energy
Renewable energy also needs to compete with well-established and cheap fossil fuels. Renewable energy has grown quickly over the last decade, driven by policy support (tax incentives, R&D funding and mandates requiring the use of renewables) and falling costs (especially in solar photovoltaics and wind turbines).
Globally, wind and solar electricity grew from just 32 terawatt-hours in 2000 to over 2,400 terawatt-hours in 2020: more than enough to power the entire country of India. Nonetheless, together they still only provide 9% of electricity worldwide.
As societies work to lower their greenhouse gas emissions, renewable energy is expected to play a large role, especially if we switch more heating and transportation to run on electric power and solve the problem of affordable, large-scale energy storage. How much of our energy we ultimately get from renewables will also depend on their ability to compete with other low-carbon technologies, such as nuclear, carbon capture and storage and hydrogen.
Source: MIT Climate Portal and International Energy Agency, Electricity Information 2022.
