Are Renewable Sources Of Energy?

Defining Renewable Energy

Renewable energy is defined as energy that comes from naturally replenished resources. According to National Geographic, renewable energy includes resources that are naturally replenished within a human timescale such as sunlight, wind, rain, tides, waves, and geothermal heat (https://www.nationalgeographic.org/article/renewable-energy-explained/). The key aspect is that renewable energy sources can be continually replenished in a short period of time. This is in contrast to fossil fuels which take millions of years to form naturally.

The most common types of renewable energy sources are:

• Solar energy from the sun
• Wind energy
• Hydropower from flowing water like rivers or waterfalls
• Geothermal energy from heat generated within the earth
• Biomass energy from organic material like plants and animal waste

These renewable sources provide sustainable clean energy alternatives to non-renewable fossil fuels. As Prysmian Group explains, renewable energy comes from naturally occurring processes that are constantly replenished (https://www.prysmiangroup.com/en/insight/sustainability/renewable-energy-definition-and-types-of-clean-energy). Unlike coal, oil, and natural gas, renewable sources will not run out or be depleted. This makes renewable energy a key part of building a sustainable energy future.

Advantages of Renewable Energy

Renewable energy sources like solar, wind, hydropower, geothermal and biomass offer several advantages over traditional fossil fuels like coal, oil and natural gas. Some key advantages include:

Renewability – Renewable sources like sunlight, wind, and geothermal heat won’t run out. They are constantly replenished by nature and are essentially inexhaustible when properly managed (Source).

Sustainability – Harvesting renewable energy doesn’t deplete finite resources and causes little to no damage to the environment when done properly. Renewables are considered sustainable and environmentally-friendly (Source).

Reduce Fossil Fuel Dependence – Shifting to renewable energy reduces dependence on imported fossil fuels prone to volatile price swings. This increases energy security for a nation (Source).

Lower Emissions – Renewables produce little to no global warming emissions or air pollutants like particulate matter, sulfur dioxide, or mercury compared to fossil fuels (Source). This improves public health.

Solar Energy

Solar energy refers to the radiant light and heat that comes from the sun. There are two main technologies for harnessing solar energy: solar photovoltaics (PV) and solar thermal.

Solar PV converts sunlight directly into electricity through the use of solar panels. These panels contain photovoltaic cells made of semiconducting materials like silicon that absorb photons from sunlight and convert them into an electric current. The electricity generated can be used immediately, fed into the grid, or stored in batteries for later use (Source: https://energy5.com/solar-power-set-to-dominate-global-energy-market-by-2040-what-next).

Solar thermal technologies, like concentrated solar power, use mirrors or lenses to concentrate sunlight in order to produce high temperatures that can then drive a steam turbine to generate electricity. Solar thermal energy can also be used more directly to heat water or spaces (Source: https://energy5.com/shining-a-light-on-solar-exploring-the-global-growth-of-renewable-energy-sources).

Solar energy capacity has seen tremendous growth in recent years. Statistics show solar energy capacity grew by 22% in 2020, with solar providing 8% of the world’s total electricity generation. Countries like Germany, China, USA, Japan and India are leading adopters of solar technology and growth is expected to continue as costs decline (Source: https://energy5.com/shining-a-light-on-solar-exploring-the-global-growth-of-renewable-energy-sources).

Wind Energy

Wind energy harnesses the power of air flow through wind turbines to generate electricity. Wind power capacity has expanded rapidly in recent years, making it one of the fastest growing renewable energy sources globally. Both onshore and offshore wind farms have contributed to this growth.

Onshore wind turbines are installed on land, often in large groups called wind farms. The average onshore wind turbine stands around 200 feet tall and has three blades spanning over 300 feet across. The United States and China currently lead the world in onshore wind capacity.

Offshore wind farms are installed in bodies of water, usually oceans or large lakes. Offshore wind turbines are larger than their onshore counterparts, with heights exceeding 500 feet and blade spans over 600 feet across. Europe, especially the United Kingdom, has pioneered offshore wind development. However, the United States and China are rapidly expanding capacity as well.

According to the American Wind Energy Association (AWEA), the United States doubled its wind power capacity in just over 2 years between 2016 and 2019 (see source). Total wind capacity in the U.S. reached over 121 gigawatts (GW) by 2021. Wind generation surpassed hydroelectric in 2019 to become the top renewable electricity source in the country, providing around 8% of total U.S. utility-scale generation.

Globally, the Global Wind Energy Council (GWEC) reports cumulative wind power capacity increased more than five-fold between 2005 and 2021, reaching over 837 GW. GWEC projects total worldwide wind capacity will double in the next five years to reach over 1600 GW by 2027.

Hydropower

Hydropower is one of the main renewable energy sources and the most widely used worldwide, according to sources (Li et al., 2023). In 2015, China had the greatest hydropower capacity and growth rate globally (Li et al., 2023). Hydropower generation utilizes the potential energy in flowing water or water held in elevated reservoirs created by dams to produce electricity via hydropower turbines. There are several types of hydropower projects:

• Dams – Used to store river water in a reservoir. The water passes through turbines to generate electricity.
• Run-of-river – Channels a portion of a river through a canal and generates electricity without the need for dams or reservoirs.
• Pumped storage – Stores energy by pumping water uphill into a reservoir then releasing it through turbines to generate electricity when needed.
• Micro hydropower – Smaller scale projects that can provide local electrification in rural areas.

Global hydropower capacity reached an estimated 1,308 GW in 2020 and is expected to grow around 2.4% annually through 2030, with much of the capacity additions occurring in emerging economies (Li et al., 2023). However, there are concerns over the environmental impacts of large hydropower dams. Solutions like low-impact run-of-river projects are gaining interest.

Geothermal Energy

Geothermal energy utilizes heat from the earth to generate electricity and provide heating and cooling. There are three main types of geothermal energy plants: dry steam plants, flash steam plants, and binary cycle plants. Dry steam plants use steam from geothermal reservoirs to directly power turbines. Flash steam plants take high-pressure hot water, allow it to reach a lower pressure, and use the resulting flashed steam to drive turbines. Binary cycle plants use hot water to heat a secondary working fluid which vaporizes and drives the turbines. These plants typically have lower emissions compared to fossil fuel plants.

In addition to large power plants, geothermal energy can be harnessed through smaller scale applications like geothermal heat pumps. These pumps use the stable temperatures underground to heat and cool spaces. They can reduce energy costs by up to 70% compared to conventional heating and cooling systems. The geothermal heat pump market grew by about 8% annually from 2007 to 2017. Significant potential remains for growth in the residential and commercial sectors.

The United States is the world’s largest producer of geothermal energy and the resource could meet up to 6% of U.S. electricity demand by 2050 (https://www.energy.gov/eere/articles/going-back-well-again-harnessing-geothermal-energys-potential). While geothermal energy accounts for only 0.4% of energy generation today, technological advances and drilling cost reductions could unlock more of its potential.

Biomass Energy

Biomass energy is derived from organic matter such as plants, agricultural waste, and municipal solid waste. It harnesses the energy stored in biomass to generate electricity, heat, transportation fuels like ethanol and biodiesel, and biogas. The main categories of biomass energy sources are:

• Biofuels: Liquid fuels like ethanol and biodiesel that are made from crops like corn, sugarcane, and soybeans. Biofuels can directly replace gasoline and diesel in vehicles.
• Biogas: A mixture of methane, carbon dioxide and small amounts of other gases produced by anaerobic digestion of organic matter in landfills, sewage treatment plants, and livestock manure management systems. Biogas can be used to generate electricity and heat.
• Wood: Wood waste and forest residues that are burned to generate heat and electricity.
• Energy crops: Crops like switchgrass and poplar trees that are specifically grown for energy production.
• Municipal solid waste: The organic component of household and commercial waste, such as food scraps and paper, that can be burned for energy recovery.

According to estimates, biomass energy production capacity in the United States could reach 90 gigawatts by 2030, up from 22 gigawatts in 2022 (Morris, 2000). However, high production costs due to expensive collection and transportation of biomass feedstocks remain a key challenge. Government support policies like tax credits, grants and loan guarantees can help spur further growth of biomass power (Morris, 2001).

Challenges of Renewable Energy

While renewable energy sources have many benefits, there are some key challenges that need to be addressed for widespread adoption. One major challenge is intermittency – many renewables like solar and wind are variable and unreliable compared to traditional energy sources. This can cause issues with grid stability as supply must match demand at all times [1].

The variability of renewable energy also creates challenges with energy storage. Effective storage solutions like batteries can help mitigate intermittency, but currently remain expensive. Transmission infrastructure also needs upgrading to handle distributed renewable generation [2].

Higher upfront capital costs are another barrier for adopting renewables. While ongoing costs are low once installed, installing solar, wind, and other renewables can cost more compared to fossil fuels upfront. This can deter adoption even though over the lifetime renewables are cost-competitive [3].

Government Policy

Government policies have played a major role in advancing renewable energy by providing financial incentives, regulations, and mandates. Key policies that have driven growth in renewables include production subsidies, investment tax credits, Renewable Portfolio Standards (RPS), and clean energy goals.

Production subsidies provide payments based on the amount of renewable electricity generated. For example, the Production Tax Credit has helped make wind power cost-competitive by paying wind farm owners $0.015 per kWh produced (Source). Investment tax credits like the Solar Investment Tax Credit provide tax breaks for installing renewable systems. The ITC has spurred massive growth in solar by letting homeowners deduct 26% of installation costs from their taxes (Source).

Renewable Portfolio Standards require utilities to source a percentage of their electricity from renewables. As of 2021, 30 states plus D.C. had RPS policies, driving over half of U.S. growth in renewables (Source). Many states and cities have also adopted clean energy or carbon reduction goals, further accelerating the transition.

Future of Renewable Energy

The future looks bright for renewable energy sources like solar and wind power. According to a 2022 report, renewable energy capacity is projected to increase globally by over 60% between 2020 and 2026 (https://earth.org/the-growth-of-renewable-energy-what-does-the-future-hold/). Solar power in particular is expected to grow drastically, with solar capacity projected to triple by 2030. As costs continue to fall, renewables are becoming increasingly cost competitive with fossil fuels.

Renewables have great potential to help fight climate change by reducing carbon emissions from the electricity sector. According to projections, renewable energy could supply up to 85% of global electricity by 2050 if countries accelerate their renewable investments and policies (https://earth.org/the-present-and-future-of-renewable-energy-a-2023-update/). Widespread adoption of renewables will be key for countries to meet their climate goals under the Paris Agreement. With supportive policies and sustained investment, renewable energy can play a major role in building a sustainable energy future.