Renewable energy is what is produced using natural sources such as sunlight, wind, and water, which are able to ‘reload’ themselves over time and, in theory, are eternal, unlike finite fossil fuels.
Fossil fuels (coal, oil, and gas) are the greatest contributors to growing greenhouse gas emissions, which is why adopting more renewables can help to solve this issue.
Renewables are a very complex and broad topic. In this article, we explore their main characteristics, sources, and their role in mitigating climate change, as well as their pros and cons.
Defining Renewable Energy: Types and characteristics
Understanding the concept of renewable energy
As already explained, renewable energy is the power generated from natural processes, and this power is constantly replenished at a pace equal to or faster than it is consumed.
Common examples include solar power, wind power, hydropower, geothermal energy, and biomass energy.
Key characteristics of renewable energy sources
Renewable energy sources generally share certain key characteristics that distinguish them from conventional fossil fuels:
1️⃣ Naturally replenished
They capture the energy of ongoing natural processes that will not run out quickly, such as the water cycle, wind, sunlight, and Earth’s internal heat.
2️⃣ Low carbon emissions
Power stations that run on renewables such as solar panels and wind turbines generate electricity without burning fuel, so they emit no carbon dioxide while in operation.
This, however, does not mean that these technologies are 100% green and sustainable, but let’s discuss that further in this article.
3️⃣ Intermittency
Some power installations that run on renewable resources depend heavily on weather – wind turbines only produce power during windy weather and solar panels only when the sun is shining.
This is why renewable energy needs backup power or storage devices to provide a steady power supply.
4️⃣ Geographic dependence
Renewable energy sources are not equally available across the globe due to Earth’s geological and geographical peculiarities. While some regions are more suited for hydropower (Brazil, Canada) or geothermal heat (Indonesia, Iceland), others have plenty of sunshine or strong winds.
That said, China, the EU, and the U.S. are not so dependent on geographical location and boast large hydropower, solar, and wind power projects.
5️⃣ Sustainability and permanence
We can access these sources of energy for as long as the Earth and Sun exist.
Renewable energy power systems: Not entirely impact-free
Large installations (wind and solar farms, for instance) may have an impact on wildlife or land use.
In addition, the construction of these farms and the use of other equipment (for hydropower or bioenergy, for example) demands resources and energy.
Much of the energy needed to build power plants that run on renewables still comes from fossil fuels which is called embedded carbon. Moreover, solar panels contain heavy metals that could become hazardous waste if disposed of in large quantities.
At the same time, other experts state that wind turbines and solar panels promptly offset their construction emissions.
Common sources of renewable energy: An in-depth look
Solar energy
Solar power installations make use of the radiation from the sun and turn this into energy with the help of technologies such as photovoltaic (PV) panels, which generate electricity, and solar thermal systems, which generate heat.
Solar is the energy source that currently has the quickest rate of growth on the globe, due to rapidly falling technology costs, according to the International Energy Agency.
Wind energy
Wind power harvests the kinetic air energy that goes through wind turbines, some of which boast massive sizes, that then start to spin to generate energy. These can be mounted either onshore or offshore (in sea- or freshwater).
Massive onshore and offshore wind farms currently provide a significant amount of electricity in many nations, including China, Brazil, Finland, Australia, and Argentina, due to the recent global increase in wind power capacity, according to the World Wind Energy Association.
Hydropower
Hydropower (one of the oldest renewable sources), also known as hydroelectric power, transforms the energy of flowing water into electric energy.
It can be produced from reservoirs and rivers. Reservoir hydropower facilities use the water stored in reservoirs, whereas run-of-river hydropower plants use the flow of a river to generate electricity.
Today, the largest share of electricity from renewable resources is generated using hydropower.
Bioenergy energy
Bioenergy is made from biomass, which includes a range of organic materials like wood, charcoal, dung, and other manure, which generates heat and electricity, and liquid biofuels for agricultural crops.
A great deal of biomass is used for cooking, illumination, and heating in rural regions, usually in developing nations.
What is biodiesel?
Biodiesel is a type of diesel fuel that comes from plant and animal products. According to Advanced Biofuels Canada, biodiesel is a ‘drop-in biofuel’, meaning it can be utilized with existing diesel engines and distribution systems.
Biodiesel has physical characteristics that are analogous to those of petroleum diesel. This makes it useful for powering various vehicles, such as diesel engines for various vehicles, including trucks, buses, and off-road machinery.
It is also used as heating oil in boilers in homes and businesses.
Global electricity production (2024)
Source: OurWorldInData
Geothermal energy
Geothermal energy uses the heat from beneath the surface of our planet. Electricity is produced by power turbines, which run on hot water or steam obtained from drilled wells.
Ocean energy
Ocean energy includes the various devices that produce energy from a range of marine sources:
- Ocean currents
- Waves
- Temperature variations (ocean thermal energy conversion or OTEC)
- Salinity difference between freshwater and saltwater (osmotic energy)
Ocean energy is sometimes referred to as ‘blue energy’, although this phrase is used ambiguously. In some contexts, it indicates ocean-derived energy, whereas in others, it actually refers to osmotic (salinity gradient) power.
Here’s an example:
The role of renewable energy in sustainability
Global energy sector statistics
By the second half of the 21st century, the world’s energy sector must shift from fossil fuels to carbon-free sources in order to:
- Lower CO2 emissions
- Slow down climate change
- Limit the increase in temperature to 1.5°Cover pre-industrial levels.
According to IRENA’s World Energy Transitions Outlook, the 1.5°C pathway has a clear roadmap: electrification and efficiency will drive the change, supported by renewables, hydrogen, and sustainable biomass. The ultimate goal is to cut emissions in half by 2030.
From this pie chart, it can be seen that the world could slash CO2 emissions by 36.9 billion tons (Gt) per year by 2050 compared to business-as-usual trends. This overall reduction is the result of six primary technologies that can potentially can ‘clean up’ the energy industry.
Source: IRENA’s World Energy Transitions Outlook
Let’s analyze the data in the chart:
- Energy efficiency (25%): Concentrating on making machinery, buildings, and transportation more efficient and less wasteful in order to use less energy overall.
- Renewables (25%): Increasing the use of sustainable energy sources to replace polluting fossil fuels.
- Electrification (20%): Replacing the burning of fuels for daily necessities with eco-friendly energy.
- Hydrogen (10%): Clean hydrogen fuel for hard-to-electrify areas such as heavy trucks or steelmaking – generated without releasing additional CO2.
- Fossil fuel-based carbon capture and storage (CCS) (6%): To prevent global warming, CO2 emissions from existing fossil fuel plants should be captured and buried underground.
- Renewable-based CO2 removals (BECCS) (14%): Using bioenergy-producing plants while absorbing and storing the CO2 they emit.
This shift has the potential to provide jobs, growth, and common prosperity with the correct policies being in place, demonstrating that we can truly achieve a climate-safe future.
Source: IRENA’s World Energy Transitions Outlook
Mitigating climate change through renewable solutions
Renewable energy sources create little or no greenhouse emissions while in operation. Replacing coal, oil, and gas with renewable energy sources can reduce global carbon dioxide emissions and limit the pace of climate change.
According to studies, a significant increase in renewable energy is required to satisfy international climate targets such as the Paris Agreement.
By 2030, the world’s electricity mix is expected to change
By the end of this decade, the amount of power generated by renewable sources is expected to reach over 17,000 terawatt-hours, a jump of about 90% from 2023.
It is anticipated that a number of renewable energy milestones will be accomplished within the next five years. This includes:
- In 2025, electricity generated from renewable sources is expected to surpass coal-fired capacity, according to the IEA.
- In 2026, both solar and wind power output are expected to overtake nuclear power generation.
- In 2029, solar PV energy output is predicted to overtake hydropower, making it the world’s largest renewable power source
- In 2030, wind power is projected to move ahead of hydropower.
Source: IEA
Benefits of renewable energy
Renewable energy resources offer affordable, sustainable substitutes that promote economic resilience and net-zero objectives.
Environmental benefits
Renewable energy sources can displace fossil fuels, which are the principal source of anthropogenic greenhouse gas emissions, mostly from burning CO2.
Using these alternatives can contribute to climate change mitigation by reducing overall carbon footprints which, in turn, reduces greenhouse gas emissions and helps to address extreme weather events, as human-caused climate change worsens heatwaves, storms, and droughts.
Economic benefits
The renewable energy sector provides jobs in production, installation, and maintenance and promotes innovation while lowering long-term energy costs.
- Nearly 35 million people are employed globally in the clean energy sector, which already has more jobs than the fossil fuel industry, according to the United Nations data. The number of workers in the renewable energy industry, which is a sub-sector, increased from 13.7 million in 2022 to 16.2 million in 2023, according to the International Renewable Energy Agency.
- Costs for solar and wind power plants have plummeted.
- Investments in renewables now exceed those in fossils.
In 2025, it is anticipated that global energy investment will reach an all-time high of US$3.3 trillion, with investments in clean technologies expected to reach US$2.2 trillion, according to the International Energy Agency.
Sources: IEA
Health and social benefits
Renewable energy sources improve air quality by reducing emissions from gas and coal, which lowers respiratory ailments and benefits public health.
Through local projects and decentralized systems such as microgrids, they encourage community development and advance energy equity, particularly in underprivileged areas.
Energy security and reliability
Renewables improve national security by reducing the reliance on imported fuels.
With better storage and hybrid systems, renewables can now deliver reliable power even as demand rises from extended electrification.
Challenges and limitations of renewable energy
Despite its quick development, huge investments, and impressive adoption rates, renewable energy still faces a number of obstacles, with systemic, financial, and technical problems limiting its widespread adoption.
Intermittency and variability
Because solar and wind are weather-dependent, their output varies, and their timing does not correspond with demand.
Energy storage constraints
Reliability for grid-scale applications is suffering from a lack of scalable storage options, such as batteries. Lithium and other types of batteries for storing energy still come at a high cost.
Grid and infrastructure issues
Old power grids cannot keep up with renewables.
A paper published on ScienceDirect by experts from the School of Mechanical and Aerospace Engineering, School of Electronics, Electrical Engineering and Computer Science at Queen’s University of Belfast, and School of Engineering at the University of Manchester states that currently there are difficulties in keeping electrical grids stable in systems that rely primarily on renewable energy sources, which lessen “inertia” and can result in problems with frequency and voltage during failures.
Upgrades are needed, but are being slowed by permits and regulations.
Financial constraints
Financial barriers may prevent developing nations from widely implementing renewable energy, which means that adequate support systems and funding will be required.
Increased demand for large land areas
Large land areas may be required for installations such as wind turbines or solar farms in order to scale up renewable energy.
This may result in conflicts over land usage, the effects on the environment, and possible disruption to ecosystems.
Problems for fossil fuel-dependent nations
Making the switch to renewable energy will be extremely difficult for economies that rely significantly on fossil fuels. In certain areas, rapid changes may lead to employment losses and economic instability.
Emerging trends and innovations in the renewable energy sector
Advances in renewable energy have the potential to make it cheaper, more efficient, and as a result increase its adoption.
1️⃣ Energy storage innovations
Although lithium-ion is still the most common storage technology, the power industry is diversifying by exploring technologies that may be adapted to specific situations while still satisfying grid demands.
Electro-chemical storage:
- Iron-air batteries: Low-cost, long-duration (up to 100 hours) storage using iron, water, and air.
- Hydrogen storage: Salt caverns and solid-state metal hydrides provide long-duration, high-density storage; commercial implementation is still in the works.
Electro-mechanical storage:
- Gravity-powered energy storage: Lifts/lowers composite blocks for four-hour storage with 80% efficiency; projects in China.
- Pumped storage hydropower (PSH): A form of hydroelectric power storage. PSH functions similarly to a huge battery, storing power and then releasing it when necessary.
Thermal energy storage:
- Sensible heat: Sensible heat storage, which makes use of solid and liquid materials including rock, sand, clay, soil, water, and oil, is the most popular method of storing thermal power.
- Latent heat: When a material undergoes a phase shift such as melting or solidification, heat is either retained or released at a temperature that is nearly constant.
Artificial Intelligence (AI) in energy storage
AI improves grid stability and system efficiency through comprehensive performance adjustment.
AI algorithms can also help to optimize battery charging and discharging, which in turn will improve their lifespan and efficiency.
2️⃣ Alternative manufacturing technologies
Laminated veneer lumber (LVL) is a sustainable, wood-based material used to make wind turbine blades, and it can help to reduce both costs and emissions.
Senvion and Voodin Blade Technology are aiming to produce the world’s longest wooden wind turbine blades, created using LVL, which will produce 78% less CO2 and are robust, lightweight, and biodegradable.
3️⃣ Offshore innovations
Remotely-controlled robots and drones can be used to evaluate and help to repair installations located away from the mainland. Here’s an example of their use today:
Standing 210 meters above the North Atlantic, off the coast of Portugal, is Europe’s first floating wind farm:
- Three turbines
- Power generated is sufficient for 60,000 households
- 33,000 tons of CO2 a year are saved
Researchers at the University of Limerick have created advanced remote-operated robots to inspect and maintain offshore wind farms. Using underwater remotely operated vehicles (ROVs), drones, and surface robots, they have managed to capture high-resolution 3D models of structures above and below the water.
4️⃣ Hybrid wind farms: Wind, solar, and their storage
Hybrid wind farms combine wind energy with additional power sources, such as solar energy, energy storage, and occasionally fossil fuel generators.
These systems enhance the consistency of energy output while lowering energy intermittency by fusing various technologies that play to each other’s advantages.
5️⃣ “Silent” accessories
Wind and solar farms depend not only on turbines and panels but also on the reliability of the ‘silent’ accessories that make renewable energy systems more resilient, safer, and longer-lasting:
- Corrosion- and vibration-resistant connectors
- Pre-connected cable systems
- Sensorized accessories with built-in monitoring for predictive maintenance
- Self-healing polymers
Self-healing polymers are cutting-edge materials that can fix damage autonomously, thus improving performance, sustainability, and durability.
Developments like shape-memory materials have increased the range of applications for these materials, from enhancing solar panels and wind turbine blades to fixing aerospace structures.
Other trends in the renewable energy sector
Drone monitoring
Unmanned aerial vehicles (UAVs) have been successfully used on-site by the wind industry for extended surveillance and monitoring. When used in conjunction with AI and machine learning, drones offer practical and reliable ways to investigate wind turbines and the infrastructure that supports them.
Smart grids
Real-time tracking, smart meters, and demand-response programs all contribute to increased efficiency, reliability, and renewable integration.
Bioenergy
Waste-to-energy technologies such as incineration, gasification, pyrolysis, and anaerobic digestion transform organic waste into usable biogas, which aids in garbage management and rural development initiatives.
