Understanding the Shift to Renewable Energy and Looking into its Many Sources
Electricity plays an important role in powering today’s world. Whether it’s lighting up our homes, keeping our devices running, or fuelling industries. Over the decades, we’ve developed new methods to meet our growing energy needs, but the latest shift towards renewable energy is the most important change yet. Let’s go back 100 years to the early 20th century, and quickly understand why this shift took place.
The 20th Century
The 20th century was dominated by fossil fuels for electricity and transportation. Coal-fueled steam engines, trains, and power plants, especially in coal-rich regions like the U.S. and Europe.
As automobiles became more common, oil became essential, powering cars, ships, airplanes, and trucks, and by mid-century, it was the dominant transportation fuel. Natural gas also gained traction, offering a cleaner alternative to coal but still emitting CO2.
By mid-century, hydroelectric and nuclear power began contributing more to the energy mix, but fossil fuels remained the primary source. However, burning fossil fuels releases large amounts of carbon dioxide, driving climate change through rising temperatures, extreme weather, and biodiversity loss.
The figure shows the cumulative electricity generation by source from 1900 - 2000
Source: Visualizing Energy
Additionally, fossil fuels are not renewable and will eventually run out. As global energy demand increases, the need for sustainable, long-term energy sources is becoming critical, along with the geopolitical and environmental risks of fossil fuel reliance. These issues prompted a global shift towards cleaner, renewable energy sources.
The New Hero – Renewable Energy
To put it simply, Renewable energy is energy derived from natural sources that are replenished at a higher rate than they are consumed. Sunlight and wind, for example, are such sources that are constantly being replenished.
At the start of the renewable energy transition, there was a lot of skepticism. Renewables faced challenges in matching the efficiency of traditional thermal power plants (those powered by fossil fuels), which typically operate at around 40% efficiency. This means that only about 40% of the energy produced from the fuel’s heating value is converted into usable electricity.
But with technological advancements, renewables are quickly catching up with wind energy capable of achieving around 30 to 40% efficiency, and solar panels are producing upwards of 22% efficiency.
Now, let's look at the different types of renewable energy sources and get to know them better
1. Solar: Solar radiation is light – also known as electromagnetic radiation – that is emitted by the sun. While every location on Earth receives some sunlight over a year, the amount of solar radiation that reaches any one spot on the Earth’s surface varies.
Solar technologies capture this radiation and turn it into useful forms of energy. The most common methods are solar photovoltaic (PV) systems and concentrated solar power (CSP).
Solar PV is the most widely used technology for converting sunlight into electricity. Solar PV systems consist of solar panels, made up of many photovoltaic cells, these generate electricity directly from sunlight via an electronic process that occurs naturally in certain types of material, called semiconductors. Electrons in these materials are freed by solar energy and travel through an electrical circuit, powering electrical devices or sending electricity to the grid.
Concentrating solar power (CSP) plants use mirrors to concentrate the sun’s energy to drive traditional steam turbines or engines that create electricity. The thermal energy concentrated in a CSP plant can be stored and used to produce electricity when it is needed.
Working of a solar PV module
Source: Waaree
2. Wind: Wind Energy is the process by which the wind is used to generate mechanical power or electricity. A wind turbine turns wind energy into electricity using the aerodynamic force from the rotor blades, which work like an airplane wing or helicopter rotor blade. When wind flows across the blade, the air pressure on one side of the blade decreases. The difference in air pressure across the two sides which causes the rotor to spin. The spinning rotor is connected to a generator. In some turbines, the rotor is connected directly to the generator. The motion of the rotor ultimately drives the generator, producing electricity.
Wind farms, or wind power plants, consist of groups of wind turbines located in areas with favorable wind conditions. These turbines are placed strategically to maximize energy production, with factors like wind speed, terrain, and proximity to power transmission lines all influencing the location. In utility-scale wind farms, the electricity generated by each turbine is sent to a substation, where it is then transmitted to the grid to power homes and businesses.
Source: US Department of Energy
3. Bioenergy: Bioenergy is a form of renewable energy generated when we burn biomass fuel. Biomass fuels come from organic materials such as harvest residues, purpose-grown crops, and organic waste from our homes, businesses, and farms. Biomass sources for energy include: Wood and wood processing waste, crops and waste materials Biogenic materials in municipal solid waste, Animal manure, and human sewage for producing biogas (renewable natural gas).
Biomass is converted to energy through various processes, direct combustion is the most common method for converting biomass to useful energy. All biomass can be burned directly for heating buildings and water, for providing industrial process heat, and for generating electricity in steam turbines.
Thermochemical conversion of biomass includes pyrolysis and gasification. In both processes biomass feedstock materials are heated in closed, pressurized vessels called gasifiers at high temperatures.
A chemical conversion process is used for converting vegetable oils, animal fats, and greases into fatty acid methyl esters to produce biodiesel.
Biological conversion of biomass includes fermentation to make ethanol and anaerobic digestion to produce biogas.
According to the International Energy Agency (IEA), as of 2023, Modern bioenergy is the largest source of renewable energy globally, accounting for 55% of renewable energy and over 6% of global energy supply.
Biofuel demand growth by fuel and region, 2022-2024
Source: IEA
4. Geothermal Energy: Geothermal energy is heat energy from the earth, Geothermal resources are reservoirs of hot water that exist or are human-made at varying temperatures and depths below the earth's surface. Wells, ranging from a few feet to several miles deep, can be drilled into underground reservoirs to tap steam and very hot water that can be brought to the surface for use in a variety of applications.
In geothermal power plants, fluids are extracted from these underground reservoirs, where they are heated by the Earth’s natural heat. This steam or hot water is then used to drive turbines that generate electricity. Afterward, the steam is reinjected back into the reservoir to maintain the system’s sustainability.
In addition to electricity generation, geothermal energy can be used for heating and cooling buildings.
5. Green Hydrogen: Hydrogen is the most abundant element on Earth, and when produced using renewable energy, it’s referred to as green hydrogen.
Green hydrogen is typically produced through a process called electrolysis, where an electrical current is passed through water to separate hydrogen from oxygen. This method relies on renewable electricity, such as solar or wind energy, making it a clean and sustainable way to produce hydrogen.
Another method for producing hydrogen is pyro-gasification. This process involves heating organic materials, like wood biomass, crop residue, and various carbon-based waste (such as old tires, non-recyclable plastics, and dried sludge from wastewater treatment), to high temperatures between 900°C and 1,200°C. This occurs in the presence of a small amount of oxygen, breaking down the materials into a complex gas mixture that contains hydrogen.
According to IEA projections, renewable energy consumption across the power, heating, and transport sectors is expected to grow by nearly 60% between 2024 and 2030. This growth will raise the share of renewables in global energy consumption to almost 20% by 2030, up from 13% in 2023. The transition to renewable energy marks one of the most significant shifts in the energy landscape over the last hundred years.