What Is Considered A Renewable Source Of Energy?

Renewable energy sources refer to energy derived from natural processes that are constantly replenished. Some examples include solar, wind, geothermal, hydroelectric, and biomass energy. Renewable energy is considered clean energy because it does not produce harmful byproducts like fossil fuels do. Renewable energy is extremely important for several reasons:

First, renewable energy helps combat climate change by reducing greenhouse gas emissions. Unlike fossil fuels, renewable sources like solar and wind do not release carbon dioxide and other pollutants that contribute to global warming. Widespread adoption of renewables is critical for transitioning to a low-carbon economy.

Second, renewable energy promotes energy independence and security by relying on domestic sources. Many countries are reliant on imported fossil fuels that are subject to price volatility and supply disruptions. Developing local renewables reduces this dependence on imports.

Third, renewable energy spurs new jobs and economic growth, especially in rural areas. Constructing wind farms, solar fields, and hydroelectric dams creates employment opportunities while providing cheaper and more reliable power.

In summary, renewable energy is essential for environmental sustainability, energy security, and economic development. This article will explore major renewable energy sources and their growing importance.

Solar

Solar energy comes directly from the sun and is considered a renewable resource. There are two main technologies used to harness solar energy: solar photovoltaics (PV) and solar thermal.

Solar PV systems use solar panels made up of photovoltaic cells to convert sunlight into electricity. The photovoltaic effect causes these cells to produce an electric current when exposed to sunlight. Solar PV systems can range from small rooftop systems on homes and businesses to large utility-scale solar farms.

Some key statistics on solar PV in the United States according to this source:

• Solar PV capacity has grown at an average annual rate of 49% over the past decade.
• In 2021, solar PV accounted for 3.3% of total U.S. electricity generation.
• Over 107 gigawatts (GW) of solar PV capacity were operating in the U.S. at the end of 2021.

Solar thermal systems, also known as solar hot water systems, use collectors to absorb heat from the sun to warm water or another heat-transfer fluid. This heated fluid can then provide hot water, space heating, or electricity generation.

According to the U.S. Department of Energy, the United States has over 1.5 million solar water heating systems installed. Key applications include heating swimming pools and domestic hot water.

Wind

Wind energy comes from air flow through wind turbines, usually in large groups called wind farms. Wind turbines convert the kinetic energy of wind into mechanical power, which then generates electricity. Wind power has seen tremendous growth in recent decades as a renewable energy source. In 2020, wind generated over 1,129 terawatt-hours of electricity globally, meeting close to 10% of the world’s total electricity demand.¹

Many wind farms today are onshore, but offshore wind farms are growing rapidly as well. Floating offshore wind farms allow turbines to be placed further out at sea where winds are stronger. Wind power is considered a green, renewable source of energy since no fuels are burned and minimal environmental impacts occur once a wind farm is built. The wind resources in an area determine how productive a wind farm can be. Advances in turbine technology, like larger rotors and taller towers, also contribute to greater energy generation.

Looking ahead, wind power capacity is forecast to grow substantially to meet renewable energy goals aimed at reducing greenhouse gas emissions and reliance on fossil fuels. The Global Wind Energy Council predicts worldwide wind power capacity will reach 2,110 GW by 2030, more than double 2020 levels.² With sufficient investment and policy support, wind energy will continue expanding as a major renewable electricity source.

Hydroelectric

Hydroelectric power is generated from water flow and is considered a renewable energy source. Some key aspects of hydroelectric power include:

Dams are a common feature of hydroelectric power plants. By constructing a dam on a river, water can be stored in a reservoir and released through turbines to generate electricity. Many large dams exist worldwide, such as the Three Gorges Dam in China, which has a massive capacity of 22,500 MW.

Tidal power utilizes the rise and fall of ocean tides to generate electricity. Tidal barrage power plants are built across an estuary or bay, using gates to control water flow through turbines. Major tidal power facilities exist in South Korea, France, and Canada.

Wave power harnesses energy from ocean surface waves. Technologies like point absorbers and oscillating water columns convert wave motion into mechanical power to turn electrical generators. Wave power holds significant potential but requires more development and full-scale facilities.

Overall, hydroelectricity provides around 16% of global electricity generation. With limited site availability in many regions, growth potential exists in small/low-head hydro, pumped storage, and emerging ocean technologies.

Geothermal

Geothermal energy comes from the natural heat inside the earth. It can be used to generate electricity in geothermal power plants or provide heating and cooling for buildings directly through geothermal heat pumps (Source). There are three types of geothermal power plants:

• Dry steam plants that use steam from reservoirs to turn turbines.
• Flash plants that pull deep, high-pressure hot water into lower-pressure tanks and use the resulting flashed steam to drive turbines.
• Binary cycle plants that pass lower-temperature water by a secondary fluid with a much lower boiling point, causing it to vaporize and spin turbines.

For heating and cooling, geothermal heat pumps move heat between the earth and buildings. In winter, the pumps draw heat from the ground into the building. In summer, they transfer heat from the building back into the cooler ground (Source).

The top countries generating electricity from geothermal sources include the U.S., Indonesia, Philippines, and Kenya. Global geothermal capacity was around 16 GW in 2021, providing a stable, renewable baseload power source.

Biomass

Biomass refers to organic materials that come from plants and animals that can be used as an energy source. It is considered a renewable energy source because the plants and other organic materials used to create biomass energy can be regrown over relatively short periods of time compared to the hundreds of millions of years needed for fossil fuels to form. Common sources of biomass include wood from forests, material left over from agricultural or forest processes, and methane from landfills or animal waste. ¹

One major use of biomass is for biofuels. Biofuels are fuels produced directly from living matter and include ethanol, biodiesel, and biogas. Ethanol is an alcohol fuel made by fermenting the sugar components of plant materials and is commonly made from corn or sugarcane. It can be blended with gasoline to reduce petroleum consumption. Biodiesel is typically made from vegetable oils or animal fats and can power diesel engines when blended with conventional diesel. Biogas refers to gases like methane produced from the decomposition of organic wastes and can be purified to produce renewable natural gas. ²

Another major biomass energy application is using agricultural crop waste and residues like corn stover, wheat straw, rice straw, and sugarcane bagasse for energy production. These materials are abundant and inexpensive sources of biomass that would otherwise be discarded. Converting crop wastes into usable energy helps utilize these organic materials efficiently and provides renewable power. ³

Hydrogen

Hydrogen is a clean fuel that does not emit carbon dioxide or pollutants when used in fuel cells (Bhandari, 2021). Fuel cells combine hydrogen and oxygen to generate electricity and heat, with water and heat as the only byproducts. Although hydrogen does not occur naturally as a gas, it can be produced through methods like electrolysis using renewable energy like solar and wind. The hydrogen can then be stored and transported for use in vehicles or stationary applications like power generation (Bossel & Eliasson, n.d.).

One of the main advantages of hydrogen is its high energy density by weight, though it has a low density by volume which requires compression or liquefaction for storage and transportation. Converting renewable electricity into hydrogen enables long term storage to help manage intermittent supply and demand. Hydrogen fuel cell vehicles can achieve similar performance to gasoline vehicles, with faster refueling. However, challenges remain such as the high costs of producing, transporting and storing hydrogen (OwnerTeamConsultation, 2020).

Comparison

When comparing renewable energy sources, some of the key factors to consider are cost, efficiency and sustainability. Many experts argue that solar and wind are currently the most cost-effective renewable energy sources. The costs of solar panels and wind turbines have declined dramatically in the past decade making them competitive with fossil fuels. Hydroelectric power can also be cost effective, especially at large scale dams, but opportunities for new hydroelectric facilities are limited. Other renewables like geothermal, biomass and hydrogen tend to be more expensive currently.

In terms of efficiency, the most efficient renewable energy sources are geothermal and hydroelectric power which have capacity factors around 50-60%. Capacity factor measures the amount of energy generated compared to the maximum possible. Wind turbines have capacity factors around 35% while solar PV is lower at around 20%. However, solar and wind efficiencies are improving with better technology and operations. Biomass and hydrogen have varying efficiencies depending on the technologies used.

When looking at sustainability, sources like solar, wind, geothermal and hydroelectric power tend to be favorable since they rely on indefinitely renewable resources. Biomass can be sustainable if crops and forestry are properly managed. Hydrogen is considered renewable when produced using renewable electricity rather than natural gas. Overall, experts suggest diversifying with a mix of renewable sources to balance out the costs, efficiencies and sustainability of each.

Growth Potential

Renewable energy sources have immense potential for growth in the coming years and decades. According to the International Energy Agency (IEA), under current policies and market conditions, global renewables capacity is forecast to grow to a total of 7,300 GW by 2028. However, to reach global climate goals and limit global warming, renewables capacity will need to expand even faster.

The IEA projects that renewables need to supply over 90% of global electricity generation by 2050 in order to achieve net zero emissions. This will require renewable energy capacity to triple from current levels to over 25,000 GW globally. Solar power is expected to dominate capacity growth, with solar PV capacity projected to expand from 760 GW in 2021 to over 8,500 GW by 2050. Wind power capacity would also need to quadruple to around 5,900 GW.

While ambitious, this level of renewable energy growth is achievable with the right policies, investments, and technologies in place. Key factors that will enable this transition include continued cost reductions, grid integration solutions, energy storage advances, and policy support mechanisms such as carbon pricing and clean energy mandates. With resolute efforts to scale up renewables and electrify energy end uses, the IEA’s net zero pathway is technically and economically feasible.

Sources:

https://www.reuters.com/sustainability/climate-energy/renewable-energy-growth-must-accelerate-reach-2030-goal-iea-2024-01-11/

https://www.iea.org/news/the-energy-world-is-set-to-change-significantly-by-2030-based-on-today-s-policy-settings-alone

Conclusion

In summary, renewable energy sources like solar, wind, hydroelectric, geothermal, biomass, and hydrogen offer immense potential benefits compared to fossil fuels. Renewables produce little to no greenhouse gas emissions, reduce air pollution, diversify energy supply, provide energy security, and create jobs. The costs of renewables continue to fall dramatically while performance improves. Government policies, investments, and further technological advances can accelerate the transition. Using more renewable energy is critical for mitigating climate change, preserving the planet for future generations, and building a sustainable energy future.

It is clear the world must ramp up investments in renewable energy substantially in the coming years and phase out fossil fuel use. Each of us can play a role by supporting renewable energy policies, adopting renewable power in our homes, and spreading awareness of the benefits. With smart policies and public engagement, renewables can transform our energy systems, economies and societies for the better.