Clean energy is the generation of energy from sources that produce virtually no greenhouse gas emissions, which in turn reduces the effects of global warming. So, we had to ask: What is clean energy really, and how could it help us mitigate climate change?

Clean energy is the generation of energy from sources which emits little to no carbon emissions (11 and 48 gCO₂ on a life-cycle basis) and no greenhouse gas emissions. All types of clean energy (solar, wind, geothermal, tidal, wave, and nuclear) combat climate change and promote energy independence.

Keep reading to find out all about what clean energy is, its global capacity, its carbon footprint, its environmental benefits and drawbacks, and how it can combat climate change.

The Big Picture of Clean Energy

Clean energy is the generation of energy from sources that emit virtually no GHGs, which in turn reduces the effects of global warming.

How Is Clean Energy Defined

Clean energy is an energy substitute for fossil fuels (e.g., coal, oil, natural gas) that can reduce the effects of global warming by limiting global greenhouse gas emissions (GHGs). It is derived from processes that do not release GHGs into our atmosphere. 

“Clean Energy: energy, as electricity or nuclear power, that does not pollute the atmosphere when used, as opposed to coal and oil”

Collins Dictionary

Clean energy produces virtually no GHGs or any other environmental pollution upon operation, which aids in the fight against global climate change. However, clean energy can possess geographic limitations and offer intermittent production peaks depending on weather conditions.

What Are the Different Types of Clean Energy 

The 6 types of clean energy are: solar, wind, geothermal, tidal, wave, and nuclear energy. They are all defined as clean energies because no greenhouse gasses are emitted during their operation.

• Solar energy is the conversion of sunlight into electrical energy either through the use of photovoltaic (PV) panels or solar radiation concentrating mirrors. 

“Solar Energy: energy that uses the power of the sun to produce electricity”

Cambridge Dictionary

• Wind energy is the conversion of moving air into electrical energy. It is a form of solar energy that is caused by the uneven heating of the earth’s surface, irregularities of the earth’s surface, and the earth’s rotation. 

“Wind: a current of air moving approximately horizontally, especially one strong enough to be felt”

Cambridge Dictionary

• Geothermal energy is the conversion of heat inside of the earth into electric energy. It is created by the decay of radioactive materials in the rock and fluid of the earth’s core. 

“Geothermal: involving or produced by the heat that is inside the earth”

Cambridge Dictionary

• Tidal energy is the conversion of the earth’s tides into electrical energy. It is created by the gravitational pull of the sun and moon coupled with the rotation of the earth.

“Tidal Power: power that comes from the movement of the tide (= the rise and fall of the ocean that happens twice every day) and that can be used especially for producing electricity”

Cambridge Dictionary

• Wave energy is the conversion of the up and down motion of waves into electrical energy. It is created when the wind blows over the surface of the water on oceans or lakes. 

“Wave Power: electrical energy generated by harnessing the up-and-down motion of ocean waves”

Britannica

• Nuclear energy occurs when a neutron strikes the nucleus of an atom, thereby breaking the atomic center into pieces and releasing energy in the form of radiation and heat. 

“Nuclear Power: the power produced when the nucleus (= central part) of an atom is divided or joined to another nucleus”

Cambridge Dictionary

These 6 types of clean energy could play an important role in mitigating climate change, so let’s have a closer look at them next.

How Does Clean Energy Work

In general, clean energy works by harvesting the kinetic energy of a specific clean energy source which turns a turbine and spins a generator to produce electricity. 

How Does Clean Energy Actually Produce Energy

More specifically, each clean energy source is harvested in different ways.

Solar energy uses either photovoltaic (PV) solar cells or concentrating solar thermal plants (CSP) to produce electricity. The former absorbs energy from sunlight, creating an electrical charge which moves in response to an internal electric field in the cell, causing electricity to flow. The latter reflects and concentrates sunlight onto receivers that collect and convert solar energy into heat. 

• Enough sunlight strikes the surface of the earth in an hour and a half to account for the world’s energy consumption in a year. Because solar energy has such a large electricity generation potential, it is important to understand how it works.

Wind energy is generated when wind turns onshore or offshore wind turbine blades, producing electricity. 

• The global installed capacity of wind energy increased by a factor of 75 between 1997 and 2018, growing from 7.5 GW to over 564 GW. Because wind energy is one of the cheapest and fastest-growing renewable energy technologies with a low carbon emissions profile, it is important to understand how it works.

Geothermal energy is generated when drilling down to hot water reservoirs up to a mile below the surface creates steam which is used to produce electricity.

• Because geothermal systems have a life-cycle global warming emission of approximately 0.2 pounds of carbon dioxide (CO₂) equivalent per kilowatt-hour, compared to 1.4-3.6 pounds for coal, it is important to understand how it works..

Tidal energy is generated when tidal turbines, barrages, and lagoons use the rise and fall of tides to produce electricity.

• Because estimates for the life-cycle global warming emission of tidal energy are below 0.05 pounds of CO₂ equivalent per kilowatt-hour, compared to 1.4-3.6 pounds for coal, it is important to understand how it works.

Wave energy is generated when float/buoy, oscillating water columns, and tapered channel systems use the rise and fall of waves to produce electricity. 

• The market for wave energy is expected to reach $141 million by 2027. Because the generating potential for wave energy is so high, it is important to understand how it works.

Nuclear energy is generated when a neutron strikes the nucleus of an atom, thereby releasing energy in the form of radiation and heat. This creates steam which is used to produce electricity.  

• Nuclear power makes up 10% of global energy generation. Because it is often described as an efficient, safe, and clean energy substitute for fossil fuels,  it is important to understand how it works.

What Is the Global Capacity of Clean Energy

Solar, wind, geothermal, tidal, and wave energy are by definition both clean and renewable energy. Renewable energy is infinite by definition because the resources naturally replace themselves over time. It is mostly non-polluting, low-maintenance, and promotes the decentralization of energy supply.

Driven by decreasing costs and improved technology, renewable energy capacity grew over 4 fold from 2000-2021, increasing from 754 gigawatts (GW) to 3,064 GW. This is as more and more effort is put into reducing global GHG emissions to mitigate climate change

However, only a few countries have renewables as their primary energy source, while the vast majority of countries still have a long way to go. Approximately 11% of global primary energy came from renewable energy technologies in 2019. 

Nuclear energy, the remaining type of clean energy, is not classified as renewable energy because it uses Uranium-235 (U-235), of which supply is finite. U-235 has a concentration of 2.8 parts per million (0.7% abundance) in Earth’s crust, but we have already used up most of it because it has a half-life of about 700 million years. 

Globally, nuclear capacity increased to 415 GW in 2020, and 439 reactors were in operation in 2021. According to current trends and policy targets, nuclear capacity in 2040 will total 582 GW, which is still below the 730 GW required to become net zero by 2050.

What Is the Carbon Footprint of Clean Energy

The carbon footprint is one of the ways we measure the effects of human-induced global climate change. It primarily focuses on the GHG emissions associated with consumption, but also includes other emissions such as methane (CH4), nitrous oxide, and chlorofluorocarbons.

“Carbon footprint: the amount of greenhouse gasses and specifically carbon dioxide emitted by something (such as a person’s activities or a product’s manufacture and transport) during a given period”

Merriam Webster

On a life-cycle basis, the carbon footprint of green energy ranges anywhere from 11 to 48 grams of CO₂ equivalent per kWh (gCO₂/KWh) of electricity produced.

Have a look at the illustration below to compare the average life-cycle CO₂ equivalent emissions from clean energies to those of different types of energy.

When discussing the carbon footprint of certain clean energy types, we must take into account carbon emissions across the energy’s building, operating, and building back phases.

Because clean energy is becoming a greater part of our energy mix, it is important to understand what its carbon footprint is. And what its environmental benefits and drawbacks are.

How Environmentally Friendly Are Clean Energy Sources

The overall environmental friendliness of clean energy depends on which specific type of energy is being discussed.

“Environmentally friendly: (of products) not harming the environment.”

Cambridge Dictionary

There are collective, as well as unique, benefits and drawbacks to clean energy. 

What Are the Environmental Benefits of Clean Energy 

All 6 clean energies have the following environmental benefits:

• Climate change mitigation: The above-mentioned clean energies have an average life-cycle CO₂ equivalent emission value between 4.5 and 48 gCO₂/KWh, which is much less than, e.g., coal at 820g of CO₂ equivalent per kWh. This reduction in CO₂ emissions, in turn, reduces the effects of global climate change including increasing temperatures, rising sea levels, melting of sea ice, changing precipitation patterns, and ocean acidification.

• Energy independence: Being able to produce our own electricity in the US without the aid of foreign countries is an important step to help us become more self-sufficient. Former President George W. Bush signed the Energy Independence and Security Act of 2007 to reduce U.S. dependence on oil, expand the production of renewable fuels (and confront global climate change). 

• Employment opportunities: The renewable energy sector collectively employed 12 million people worldwide in 2020. Renewable energy jobs continue to increase as we start to realize just how beneficial renewable energy is for our environment. 

There are also specific benefits unique to each clean energy type: 

• Solar: Throughout its life cycle, concentrated solar energy produces 0.04%, PV roof solar energy produces 0.05%, and PV utility solar energy produces 0.06% of the CO₂ emissions per unit of electricity that coal produces. 

• Wind: Throughout its life cycle, wind energy produces 0.02% of the CO₂ emissions per unit of electricity than coal produces. And after 3 to 6 months of operation, a wind turbine has effectively offset all emissions from its construction, which means it can operate virtually carbon-free for the rest of its lifetime.

• Geothermal: Throughout its life cycle, geothermal energy produces 5% of the CO₂ emissions per unit of electricity that coal produces. In the US alone, annual geothermal energy resources effectively offset the emission of 4.1 million metric tons (t) of CO₂, 200,000 t of SO₂, 80,000 t of nitrogen oxides, and 110,000 t of particulate matter when compared to conventional coal-fired plants.

• Tidal and Wave: Tidal and wave energy together could help reduce global CO₂ emissions from fossil fuel electricity generation by around 500 million tons by the year 2050. 

• Nuclear: Nuclear power produces 0.02% of the CO₂ emissions per unit of electricity that coal produces. Over the past 50 years it has helped to avoid around 55 gigatons (Gt) of CO₂ emissions, which is equal to nearly 2 years of global energy-related CO₂ emissions. One U-235 pellet 1 inch tall is the equivalent of 1 ton of coal. And since 1 ton of coal creates 2.086 tons (4,172 lbs) of CO₂ when it is burned, a 1-inch U-235 pellet directly avoids the emission of over 2 tons of CO₂ from our atmosphere.  

What Are the Environmental Drawbacks of Clean Energy 

Each clean energy type comes with its own set of environmental drawbacks that should be taken into account when discussing its carbon footprint. 

• Solar: The scale of land degradation and habitat loss depends on the technology, site topography, and intensity of the solar resource. Siting large-scale solar farms on abandoned land and small-scale farms on top of buildings or homes can minimize negative environmental impacts. Water is used for the construction of PV components, and CSPs require water for cooling. Hydrochloric acid, sulfuric acid, nitric acid, hydrogen fluoride, 1,1,1-trichloroethane, and acetone are all used to manufacture PV cells. If not handled and disposed of properly, these hazardous materials could present a serious risk to environmental and public health.

• Wind: Wind farms use a substantial amount of land, but the areas between and around turbines can be used for livestock grazing, agriculture, highways, and hiking trails. Turbine blades are large and can pose a threat to flying wildlife such as birds and bats. Extensive research and technological advances have reduced turbine-caused wildlife death. Turbines can also cause mechanical and aerodynamic noise pollution when constructed close to residential areas. Siting wind farms in remote locations or on abandoned lands can reduce this effect.

• Geothermal: Geothermal reservoirs occur deep underground and are not detectable from the surface. Areas where geothermal does come to the surface are only found near tectonic plate boundaries. Also, high-pressure fluid injections close to neighboring fault lines have the potential to trigger earthquakes. 90% of all earthquakes occur in the Ring of Fire, an area that coincides with the highest concentration of geothermal resources. 

• Wave: The main environmental concern with tidal and wave energy is the impact on aquatic wildlife. Construction and operation of marine energy technology may negatively impact estuarine ecosystems via underwater noise pollution, habitat changes, and wildlife collisions with turbines. Because tidal and wave energy is a relatively new technology, more research needs to be done to fully understand this environmental impact. 

• Nuclear: The main environmental drawbacks associated with nuclear power are uranium mining and nuclear waste. Uranium mining contaminates the environment with radioactive dust, radon gas, water-borne toxins, and increased levels of background radiation. Exploratory drilling and mining also heavily increases the risk of water contamination. The waste that nuclear energy does produce is radioactive and can remain hazardous for many thousands of years. These radioactive waste products include uranium mill tailings, spent (used) reactor fuel, and other radioactive wastes Proper handling, transportation, storage, and disposal of radioactive waste can help ensure that it does not leach into the environment. 

Why Is Clean Energy Important to Fight Climate Change

Fossil fuel combustion is the main contributor to atmospheric CO₂ levels. Climate Change occurs when CO₂ and other air pollutants absorb sunlight and solar radiation in the atmosphere, trapping the heat and acting as an insulator for the planet. Since the Industrial Revolution, Earth’s temperature has risen a little more than 1 degree Celsius (C), or 2 degrees Fahrenheit (F). The current global annual temperature rise is 0.18C, or 0.32F, for every 10 years. 

Using clean energy (solar, wind, geothermal, tidal, wave, and nuclear energy) instead of fossil fuel energy helps mitigate the following negative effects of climate change:

• Increasing temperatures: Earth’s atmosphere has warmed 1.5℃ since 1880. This may not seem like a lot, but these degrees create regional and seasonal temperature extremes, reduce sea ice, intensify rainfall and drought severity, and change habitat ranges for plants and animals.

• Rising sea levels: Global sea levels have increased approximately 8-9 inches since 1880, displacing people living along coastlines and destroying coastal habitats. Roads, bridges, subways, water supplies, oil and gas wells, power plants, sewage treatment plants, and landfills remain at risk if sea level rise goes unchecked. 

• Melting of sea ice: Since 1979 arctic sea ice has declined by 30%. Sea ice plays a major role in regulating the earth’s climate by reflecting sunlight into space and providing habitat for animal species. If all of the glaciers on Earth melted, sea levels would rise by approximately 70 feet, effectively flooding out every coastal city on the planet. 

• Changing precipitation patterns: Extreme weather events (e.g., hurricanes, floods, droughts) are becoming more common and more intense. Storm-affected areas will experience increased precipitation and flooding whereas areas located further from storm tracks will experience decreased precipitation and droughts.

• Ocean acidification: The ocean absorbs 30% of the CO₂ released into the atmosphere, which decreases the pH (increases the acidity) of the ocean. In the past 200 years, the pH of oceans has decreased by 0.1 pH units, which translates to a 30% increase in acidity. Aquatic life unable to adjust to this rapid acidification will die off. A prime example of this is coral bleaching, where coral expel the algae (zooxanthellae) living in their tissues as a result of changes in temperature, light, or nutrients. 

Experts claim that to avoid a future plagued by rising sea levels, acidified oceans, loss of biodiversity, more frequent and severe weather events, and other environmental disasters brought on by the hotter temperatures, we must cut current GHG emissions by 50% by 2030 and reach net zero by 2050, as outlined in the 2015 Paris Climate Agreement.

The more we reduce CO₂ emissions, the more we slow the rate of temperature rise, sea-level rise, ice melting, and ocean acidification. When these rates are slowed, the earth’s biodiversity does not have to struggle to adapt to temperature and pH changes. People will not be displaced due to the flooding of coastal areas. And icebergs will continue to provide climate regulation. 

Final Thoughts

Harnessing the kinetic energy of clean energy (solar, wind, geothermal, tidal, wave, and nuclear energy) spins a turbine and powers a generator to produce electricity. The capacity for clean energy is great, but few countries currently source most of their energy from clean energy sources. 

Clean energy has a lower carbon footprint than fossil fuels (coal, oil, natural gas), combats climate change, creates jobs, and promotes energy independence, making it an environmentally friendly energy source. Any environmental concerns can all be mitigated by careful siting of power plants and proper disposal of any nuclear waste materials. Clean energy benefits both our atmosphere and Earth’s biota.

Stay impactful,

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