What Is Renewable Energy And Why Is It Important?

Renewable energy comes from natural sources or processes that are constantly replenished. Some of the most common renewable energy sources are solar, wind, hydropower, geothermal, and biomass. Renewable energy is important because it is a sustainable alternative to fossil fuels, which are non-renewable and major contributors to climate change. According to the World Wildlife Fund, renewable energy can help reduce greenhouse gas emissions and is a key component in slowing climate change. This overview will cover the main types of renewable energy sources and their benefits.

Types of Renewable Energy

There are several major types of renewable energy used today.¹

Solar Energy

Solar energy is harnessed from the sun’s rays and converted into electricity through the use of photovoltaic solar panels. It is one of the fastest growing renewable energy sources.

Wind Energy

Wind turbines convert the kinetic energy in wind into mechanical power that can generate electricity. Wind power is increasingly being used around the world as a renewable energy source.

Hydropower

Hydropower utilizes the energy in flowing water to produce electricity, often through the use of dams. It supplies nearly 20% of electricity production globally.

Geothermal Energy

Geothermal energy taps into the natural heat inside the earth to generate steam and electricity. It provides constant baseload power unaffected by weather conditions.

Biomass Energy

Biomass refers to organic matter such as plants, residues and waste that can be used as fuel sources for energy production. It accounts for about 5% of U.S. energy consumption.

Solar Energy

Solar energy is generated from solar panels that consist of photovoltaic cells made from materials like silicon. When sunlight hits these cells, the photons excite electrons and generates an electric current (1). This electricity can be used to power homes, businesses, and the grid. The amount of sunlight that hits the Earth’s surface in one hour is enough to power the entire planet for a year (2).

The solar industry has experienced massive growth over the last decade. In 2021, solar accounted for 3% of U.S. electricity generation, up from just 0.1% in 2010 (2). There are now over 3 million solar installations in the U.S., with solar panels now installed on 3% of American homes (1). The industry is projected to quadruple in size over the next 10 years (3).

Solar energy has many benefits. It produces no air pollution or carbon emissions while operating. Solar panels can be installed on homes, businesses, and in large-scale solar farms to produce clean electricity. The cost of solar has dropped dramatically in recent years, making it more affordable and competitive with fossil fuels (2). Solar energy promotes energy independence by allowing people to generate their own power. It is also renewable and sustainable, and will be available as long as the sun shines.

(1) https://www.consumeraffairs.com/solar-energy/solar-energy-statistics.html

(2) https://www.thisoldhouse.com/solar-alternative-energy/reviews/solar-energy-statistics

(3) https://www.marketwatch.com/guides/solar/solar-energy-statistics/

Wind Energy

Wind energy has emerged as one of the most rapidly growing renewable energy sources worldwide. Wind turbines convert the kinetic energy in wind into mechanical power that can be harnessed as electricity. According to the U.S. Department of Energy, utility-scale land-based wind turbines account for over 90% of worldwide wind power generation (“Advantages and Challenges of Wind Energy” 2021).

Advancements in wind turbine technology and design have enabled larger turbines and optimization for specific wind conditions. The average turbine generating capacity has increased dramatically from around 600 kW in 1990 to over 2.5 MW for turbines installed in 2014 (Wiser et al. 2016). Offshore wind farms have seen significant growth in Europe and are poised to expand in other regions like the U.S. Floating offshore wind platforms allow deployment in deeper waters further from shore.

The cost of wind energy has decreased substantially in recent years. According to the Department of Energy, the levelized cost of wind energy dropped by about 39% between 2014 and 2017 (“Advantages and Challenges of Wind Energy” 2021). Technological improvements allowing larger turbines, more reliable components, and increased efficiency have contributed to reducing costs.

Overall, wind energy offers a renewable, low emission source of electricity generation. Continued advancements in technology and design will help drive further cost reductions. Offshore wind remains a largely untapped resource, especially in regions like the U.S. that have only recently started developing projects.

Hydropower

Hydropower refers to generating electricity via water. Hydropower facilities come in all shapes and sizes, but rely on the energy of flowing water to power turbines and generate electricity. The most well-known type of hydropower facility is a dam. Dams convert the kinetic energy of flowing water into mechanical energy to spin turbines. The amount of electricity generated depends on the volume of water flow and the vertical distance the water falls.

Large hydroelectric dams have enabled the generation of low-cost renewable electricity for decades. However, dams also alter the natural flow of rivers and can impact wildlife habitats and ecosystems. There are also smaller run-of-river and micro hydropower projects that generate electricity with minimal impacts on rivers and wildlife. Micro hydropower projects generate less than 100 kilowatts of electricity and are frequently used to provide power to rural communities.

Overall, hydropower is a mature, reliable technology that offers many benefits. But all hydro projects must balance electricity production with environmental considerations through careful siting, design and operation.

Geothermal Energy

Geothermal energy utilizes heat from the Earth’s core to generate electricity. This heat can be extracted from natural reservoirs located near tectonic plate boundaries, volcanic regions, and hot spots. Water or steam heated by geothermal energy can be piped directly to run a turbine or used to warm buildings directly. According to ThinkGeoEnergy, the top countries using geothermal power in 2022 were the United States, Indonesia, the Philippines, Turkey, New Zealand, Mexico, Italy, Iceland, Kenya, and Japan.

There are three main types of geothermal power plants: flash steam plants, dry steam plants, and binary cycle power plants. Flash steam plants pull hot water from reservoirs to lower the pressure and convert it to steam to run turbines. Dry steam plants tap reservoirs of steam to directly run turbines. Binary cycle plants transfer the reservoir’s heat to another liquid with a lower boiling point that is vaporized to drive turbines.

Enhanced geothermal systems (EGS) are a growing development that pumps water into hot dry rocks to create artificial geothermal reservoirs. EGS allows geothermal power utilization in areas without natural reservoirs. While geothermal provides consistent baseload power, EGS systems are still in development stages.

According to IRENA, geothermal energy supplied about 0.3% of global electricity generation and about 70 terawatt-hours (TWh) in 2017. Significant potential remains untapped, with only about 11 gigawatts (GW) of installed global geothermal capacity out of an estimated potential capacity of over 200 GW.

Biomass

Biomass refers to organic materials from plants and animals that can be used as a renewable energy source. Some examples of biomass fuels include wood, crops, algae, and waste from plants and animals (1). Biomass contains stored chemical energy from the sun. When burned, the chemical energy is released as heat which can generate electricity with a steam turbine (2).

The most common types of biomass are plant-based. This includes wood, grasses, and waste plant materials left over from agricultural or forestry processes (1). These plant materials can be directly burned for heating or converted into liquid biofuels like ethanol or biodiesel (2). Growing plants absorbs carbon dioxide, so biomass can be considered carbon neutral. The carbon released when biomass is burned is balanced by the carbon absorbed as new plants grow. This makes biomass a clean, renewable fuel (1).

Biomass can also come from biogas produced from animal manure, food scraps, and sewage. Biogas is a mixture of gases like methane that is produced by the breakdown of organic matter by bacteria. The methane gas can be captured and used as fuel. Using waste products to create biogas fuel helps prevent methane from being released into the atmosphere as a greenhouse gas (2).

Other Renewables

In addition to the major renewable energy sources, there are some emerging technologies that show promise for increased adoption in the future. Three of these are tidal power, wave power, and hydrogen fuel cells.

Tidal power harnesses the energy from the rise and fall of ocean tides to generate electricity. Tidal power stations are similar to hydroelectric dams, except they rely on tidal flows rather than rivers. The UK has invested heavily in tidal power projects, including the world’s first large-scale tidal power plant in Swansea Bay, Wales (https://www.theguardian.com/business/2016/feb/01/swansea-bay-tidal-lagoon-power-plant-swansa).

Wave power devices extract energy directly from ocean surface waves. A few different designs have been tested, including oscillating water columns, point absorbers, and overtopping devices. Early prototypes are being tested in Scotland, Portugal, Japan, and Hawaii (https://www.energy.gov/eere/water/marine-and-hydrokinetic-technology-glossary).

Hydrogen fuel cells create electricity through an electrochemical reaction, not combustion. Although most hydrogen today comes from natural gas, it can be produced renewably through electrolysis powered by wind or solar energy. Fuel cells are being used for backup power, vehicles, and could support grid-scale storage in the future (https://www.energy.gov/eere/fuelcells/hydrogen-storage).

Benefits

One of the main benefits of renewable energy is reduced emissions. Unlike fossil fuels, most forms of renewable energy produce little to no greenhouse gas emissions. Widespread adoption of renewable energy sources can significantly reduce emissions from the electricity, heating, and transportation sectors (Top Benefits of Renewable Energy for Your Home). This is crucial for mitigating climate change and reducing air pollution.

Renewable energy also provides energy independence and security. Relying on domestic renewable resources reduces dependence on imported fossil fuels. This insulates a country from global oil and gas price shocks and supply disruptions (Top 5 Benefits of Renewable Energy – Extensia Financial). Local renewable energy production diversifies and decentralizes energy supply as well.

Lastly, renewable energy can lead to long-term cost reductions. Although upfront costs are still higher than fossil fuels, costs have dropped dramatically in recent years. As technology continues advancing and scale increases, the levelized costs of renewables are projected to undercut fossil fuel energy costs (Top Advantages of Renewable Energy). Lifecycle costs over decades of operation are also typically lower for renewables.

Challenges

While renewable energy has numerous benefits, scaling it also faces some key challenges. These include intermittency, grid integration, and upfront costs.

One major challenge is intermittency, or the variability in power generation from sources like wind and solar that rely on weather conditions. The sun does not always shine and the wind does not always blow, so renewable generation can fluctuate throughout the day and seasonally. This makes integrating high levels of renewables onto the electric grid complicated (Source).

Grid integration refers to the technical challenges of incorporating variable and decentralized renewable generation into existing electric systems and energy markets. Significant infrastructure upgrades are often needed to allow grids to handle two-way power flows and maintain stability with large amounts of renewables (Source).

Lastly, renewable energy systems often entail large upfront capital costs, before providing benefits like reduced operating costs over time. The high initial investment required can deter adoption, making financing and incentives important for scaling renewables (Source).