A Look at 5 of the Most Prominent Types of Renewable Energy
Fossil fuels have been the primary source of energy worldwide since the Industrial Revolution. Coal, oil, natural gas, and petrol power our homes, workplaces, factories, automobiles, and airplanes. However, the need to stem the tide of climate change has sparked a relatively recent shift in global energy. Around 75 percent of global greenhouse gas emissions come from the burning of fossil fuels, while associated air pollution has contributed to the premature deaths of about 5 million people per year.
Consequently, governments, policymakers, businesses, and individuals have sought to reduce their carbon footprints by pivoting to renewable energy. As of 2019, countries such as Iceland, Venezuela, Switzerland, Sweden, Portugal, and New Zealand sourced at least 20 percent of their primary energy from a combination of the following five renewable energy sources. There are other renewables, but these are the most significant.
Solar
Solar energy is the fastest-growing source of electricity and the most abundant renewable resource. In the United States, solar generation is expected to comprise nearly half of all renewable generation by 2050. Other countries, including Guyana, have introduced strategies to increase the percentage of their electricity generated from solar.
There are three primary types of solar energy systems, each of which capture radiation from the sun to produce electricity or heat. Photovoltaic (PV) systems convert solar radiation into electricity via solar electric cells that are arranged into panels. PV systems can be mounted on rooftops or compiled in designated power plants to generate substantial amounts of electricity. Smaller, single PV cells are also used to power gadgets. Solar thermal power plants are another type of solar energy. These collect and concentrate sunlight to heat a fluid and produce steam to spin a turbine.
In 2020, the International Energy Agency reported that solar power had reached historically low costs and is now the cheapest source of electricity in some regions of the world. Because there is a limitless supply, solar energy could eliminate the need for fossil fuels with enough support and infrastructure. This would help improve public health and address climate change.
Hydropower
Despite increasing usage of solar energy in the US, hydropower still accounted for the largest share of renewable energy generation in the country as of 2020. Understanding how energy is generated via hydro requires an understanding of the water cycle, which involves the following three steps: surface water is heated and evaporates via solar energy; water vapor liquefies into clouds and falls to the earth as either rain or snow; and that precipitation collects in rivers and empties into larger bodies of water before evaporating and beginning the cycle once again.
Run-of-the-river systems are constructed on or adjacent to a river to capture the force of the current, which spins a hydroelectric turbine. Many hydroelectric plants rely on dams and reservoirs. A large river is dammed, creating a reservoir, and the water is released through a small opening in the dam. It rushes through and powers a turbine. The amount of available energy in a water source depends on the volume of water and the change in elevation of the water flow, also known as head. (This is why you generally don’t see dams and reservoirs in flat regions.)
Hydropower is a versatile type of renewable energy that doesn’t generate pollution. However, it can disrupt waterways and negatively affect freshwater ecosystems.
Geothermal
A less common form of renewable energy, geothermal energy refers to heated water or steam escaping from the earth’s interior via fissures in its crust at geysers and hot springs. This energy can be captured in a controlled setting by drilling wells into the earth to power steam turbines. Geothermal power plants function similarly to coal-fired power plants — but natural heat from the earth, rather than burning coal, produces the heat that turns water into steam and turns the turbine. Smaller geothermal coil systems can also be buried in yards to help heat residential properties.
Wind
Wind energy is a clean and limitless source for electricity generation, but can be costly. Commercial scale wind farms are typically constructed in remote areas and require transmission lines to transport energy to densely-populated cities. Energy is generated through a system that involves wind turbines, a drive shaft, and electric generator. The World Wind Energy Association, in March 2021, reported that combined worldwide capacity of wind farms in 2020 reached 744 GW. Ninety-three GW of power generation via wind turbines was installed in 2020, which set an annual record. China, Russia, and the US set new installation records last year.
“We are very encouraged by the strong growth in the wind sector in 2020,” stated WWEA secretary general Stefan Gsänger. “Given that many governments become more committed to greenhouse gas-free renewable energy sources, we are very confident that such growth will also happen in the future, and becomes even stronger.”
Biomass
Biomass refers to non-fossilized organic materials such as wood, biofuels, and municipal solid waste (MSW). A small scale example of biomass energy is the burning of wood in a fireplace. On a larger scale, a residue of paper and pulp known as black liquor is the most prominent source of wood energy. MSW such as food scraps, grass clippings, and plastics, among other items, can also be burned in waste-to-energy plants for electricity generation. This is common in the US, where biomass energy comprises around 5 percent of all energy consumption.
