Unit 2
Energy
Content:
Fossil fuels are hydrocarbons, primarily coal, fuel oil or natural gas, formed from the remains of dead plants and animals.
In common dialogue, the term fossil fuel also includes hydrocarbon-containing natural resources that are not derived from animal or plant sources.
These are sometimes known instead as mineral fuels.
The utilization of fossil fuels has enabled large-scale industrial development and largely supplanted water-driven mills, as well as the combustion of wood or peat for heat.
Fossil fuel is a general term for buried combustible geologic deposits of organic materials, formed from decayed plants and animals that have been converted to crude oil, coal, natural gas, or heavy oils by exposure to heat and pressure in the earth's crust over hundreds of millions of years.
The burning of fossil fuels by humans is the largest source of emissions of carbon dioxide, which is one of the greenhouse gases that allows radioactive forcing and contributes to global warming.
A small portion of hydrocarbon-based fuels are biofuels derived from atmospheric carbon dioxide, and thus do not increase the net amount of carbon dioxide in the atmosphere.
Fossil fuels include coal, petroleum, natural gas, oil shale’s bitumen’s, tar sands, and heavy oils. All contain carbon and were formed as a result of geologic processes acting on the remains of organic matter produced by photosynthesis, a process that began in the Archean Eon (4.0 billion to 2.5 billion years ago). Most carbonaceous material occurring before the Devonian Period (419.2 million to 358.9 million years ago) was derived from algae and bacteria, whereas most carbonaceous material occurring during and after that interval was derived from plants.
All fossil fuels can be burned in air or with oxygen derived from air to provide heat. This heat may be employed directly, as in the case of home furnaces, or used to produce steam to drive generators that can supply electricity.
In still other cases for example, gas turbines used in jet aircraft the heat yielded by burning a fossil fuel serves to increase both the pressure and the temperature of the combustion products to furnish motive power.
One of the main by-products of fossil fuel combustion is carbon dioxide (CO2). The ever-increasing use of fossil fuels in industry, transportation, and construction has added large amounts of CO2 to Earth’s atmosphere. Atmospheric CO2 concentrations fluctuated between 275 and 290 parts per million by volume (ppmv) of dry air between 1000 CE and the late 18th century but increased to 316 ppmv by 1959 and rose to 412 ppmv in 2018. CO2 behaves as a greenhouse gas that is, it absorbs infrared radiation (net heat energy) emitted from Earth’s surface and reradiates it back to the surface. Thus, the substantial CO2 increase in the atmosphere is a major contributing factor to human-induced global warming. Methane (CH4), another potent greenhouse gas, is the chief constituent of natural gas, and CH4 concentrations in Earth’s atmosphere rose from 722 parts per billion (ppb) before 1750 to 1,859 ppb by 2018. To counter worries over rising greenhouse gas concentrations and to diversify their energy mix, many countries have sought to reduce their dependence on fossil fuels by developing sources of renewable energy (such as wind, solar, hydroelectric, tidal, geothermal, and biofuels) while at the same time increasing the mechanical efficiency of engines and other technologies that rely on fossil fuels.
Uses of fossil fuels
Three types of fossil fuels exist in three different forms. Oil being in liquid form. Coal being in solid form and natural gas being in gaseous form. Below are the fossil fuels uses in different fields:
Uses of Oil
Uses of coal
Uses of natural gas
Uses of oil: Crude oil or petroleum is also called as “black gold”. There are various uses of petroleum. It is used in the generation of electricity, used in transportation as fuel for automobiles and jets. The by-product of oil is used to produce chemicals, plastics, lubricants, tars, waxes, medicines etc. Also, many of the fertilizers, as well as pesticides, are made from either oil or its by product.
Uses of coal:
Coal is a solid state fossil fuel. It consists of five elements. They are sulphur, nitrogen, hydrogen, carbon and oxygen. Three different types of coal with different energy properties are anthracite, bituminous and lignite. Anthracite is hard with more carbon than the other two and has the highest energy. Coal could exist for 200 years more. It is mostly extracted from the mines. Coal use has almost doubled since the 20th century. Many countries cannot afford natural gas or oil as they are expensive, and so they depend on coal for energy. It is used in the generation of electricity. Also, used in electrical utilities, and products like dyes, aspirins, soap, fibres, plastics and solvents have coal or coal by product. It is used in steel industry, pharmaceutical industry, cement manufacture, manufacturing of paper etc.
Uses of natural gas:
It is a gaseous fuel and primarily consists of methane. It is much cleaner than oil and coal. It is used in air conditioning, cooking appliance like fuel stoves and heat homes and buildings, heating water etc. It also provides electricity and is used in industries like steel foundries, glass foundries other manufacturing, aluminium smelters. It also produces paints, fertilizers, plastics and dyes. It is also used in transportation as CNG or LNG. These were some fossil fuels and their uses.
Nuclear fuel is the fuel that is used in a nuclear reactor to sustain a nuclear chain reaction. These fuels are fissile, and the most common nuclear fuels are the radioactive metals uranium-235 and plutonium-239.All processes involved in obtaining, refining, and using this fuel make up a cycle known as the nuclear fuel cycle.
Uranium-235 is used as a fuel in different concentrations. Some reactors, such as the CANDU reactor, can use natural uranium with uranium-235 concentrations of only 0.7%, while other reactors require the uranium to be slightly enriched to levels of 3% to 5%. Plutonium-239 is produced and used in reactors (specifically fast breeder reactors) that contain significant amounts of uranium-238. It can also be recycled and used as a fuel in thermal reactors. Current research is being done to investigate how thorium-232 can be used as a fuel.
Production
Fuel fabrication plants are facilities that convert enriched uranium into fuel for nuclear reactors. For light water reactors, uranium is received from an enrichment plant in solid form. It is then converted into a gas and chemically converted into a uranium dioxide powder. This powder is then pressed into pellets and packed into fuel assemblies. A mixed oxide fuel can also be created when the uranium powder is packed along with plutonium oxide. The hazards present at fuel fabrication facilities—mainly chemical and radiological—are similar to the hazards at enrichment plants. These facilities generally pose a low risk to the public.
Use
When used in a reactor, the fuels used can have a variety of different forms a metal, an alloy, or some sort of oxide. Most nuclear reactors are fuelled with a compound known as uranium dioxide. This uranium dioxide is put together in a fuel assembly and inserted into the nuclear reactor where it can stay for several months or up to a few years. While in the reactor the fuel undergoes nuclear fission and releases energy. This released energy is used to generate electricity. Neutrons released during the fission process allow for a fission chain reaction to occur, allowing energy to be generated continually. The fuels are removed from the reactor after large amounts of the fuel whether it is uranium-235 or plutonium-239 have undergone fission. The "used" nuclear fuel is known as spent or irradiated fuel. After use, the fuel must be cooled for a few years as it is extremely hot.
The spent fuel is placed in large, deep pools of water that act as a coolant and a radiation shield. The coolant property allows the water to remove the decay heat and the shielding abilities protect workers from the radioactivity of the fuel. After cooling, the fuel can be re-purposed or sent to storage depending on regulations.
Advantages and Disadvantages of Nuclear Fuels
Worldwide, there are extensive reserves of uranium left to mine. While nuclear fuel is not renewable, it is sustainable since there is so much of it. It will run out eventually, but not for centuries. Unlike fossil fuels, using nuclear fuels to produce energy does not directly produce carbon dioxide or sulphur dioxide. It should be mentioned that the processes of mining, transporting, and refining the fuel have carbon emissions associated with them,[2] comparable to those of wind and solar power. Although the carbon footprint of using nuclear fuels is smaller, there are still disadvantages of using nuclear fuel. The waste while a much lower volume must be handled very carefully because of its radioactivity. Nuclear fuels require far more complicated systems to extract their energy, which calls for greater regulation. These complex systems and regulation make for very long build times. In addition, public opinions on nuclear energy tend to be more negative than with other energy sources. The over-estimation of the dangers associated with releases of radioactive material is a significant issue, as large-scale nuclear incidents are rare.
Hydroelectricity is electrical energy generated when falling water from reservoirs or flowing water from rivers, streams or waterfalls (run of river) is channelled through water turbines. The pressure of the flowing water on the turbine blades causes the shaft to rotate and the rotating shaft drives an electrical generator which converts the motion of the shaft into electrical energy. Most commonly, water is dammed and the flow of water out of the dam to drive the turbines is controlled by the opening or closing of sluices, gates or pipes. This is commonly called penstock.
Hydropower is the most advanced and mature renewable energy technology and provides some level of electricity generation in more than 160 countries worldwide. Hydro is a renewable energy source and has the advantages of low greenhouse gas emissions, low operating costs, and a high ramp rate (quick response to electricity demand), enabling it to be used for either base or peak load electricity generation, or both.
Hydroelectric power, also called hydropower, electricity produced from generators driven by turbines that convert the potential energy of falling or fast-flowing water into mechanical energy. In the early 21st century, hydroelectric power was the most widely utilized form of renewable energy; in 2019 it accounted for more than 18 percent of the world’s total power generation capacity.
In the generation of hydroelectric power, water is collected or stored at a higher elevation and led downward through large pipes or tunnels (penstocks) to a lower elevation; the difference in these two elevations is known as the head. At the end of its passage down the pipes, the falling water causes turbines to rotate. The turbines in turn drive generators, which convert the turbines’ mechanical energy into electricity. Transformers are then used to convert the alternating voltage suitable for the generators to a higher voltage suitable for long-distance transmission. The structure that houses the turbines and generators, and into which the pipes or penstocks feed, is called the powerhouse.
Hydroelectric power plants are usually located in dams that impound rivers, thereby raising the level of the water behind the dam and creating as high a head as is feasible. The potential power that can be derived from a volume of water is directly proportional to the working head, so that a high-head installation requires a smaller volume of water than a low-head installation to produce an equal amount of power. In some dams, the powerhouse is constructed on one flank of the dam, part of the dam being used as a spillway over which excess water is discharged in times of flood. Where the river flows in a narrow steep gorge, the powerhouse may be located within the dam itself.
In most communities the demand for electric power varies considerably at different times of the day. To even the load on the generators, pumped-storage hydroelectric stations are occasionally built. During off-peak periods, some of the extra power available is supplied to the generator operating as a motor, driving the turbine to pump water into an elevated reservoir. Then, during periods of peak demand, the water is allowed to flow down again through the turbine to generate electrical energy. Pumped-storage systems are efficient and provide an economical way to meet peak loads.
Solar energy is the most abundant energy resource on Earth. It can be captured and used in several ways, and as a renewable energy source, is an important part of our clean energy future.
The sun does more than for our planet than just provide light during the daytime – each particle of sunlight (called a photon) that reaches Earth contains energy that fuels our planet. Solar energy is the ultimate source responsible for all of our weather systems and energy sources on Earth, and enough solar radiation hits the surface of the planet each hour to theoretically fill our global energy needs for nearly an entire year
Where does all of this energy come from? Our sun, like any star in the galaxy, is like a massive nuclear reactor. Deep in the Sun’s core, nuclear fusion reactions produce massive amounts of energy that radiates outward from the Sun’s surface and into space in the form of light and heat.
Solar power can be harnessed and converted to usable energy using photovoltaic or solar thermal collectors. Although solar energy only accounts for a small amount of overall global energy use, the falling cost of installing solar panels means that more and more people in more places can take advantage of solar energy. Solar is a clean, renewable energy resource, and figures to play an important part in the global energy future.
There are many ways to use energy from the sun. The two main ways to use energy from the sun are photovoltaic and solar thermal capture. Photovoltaic are much more common for smaller-scale electricity projects (like residential solar panel installations), and solar thermal capture is typically only used for electricity production on massive scales in utility solar installations. In addition to producing electricity, lower temperature variations of solar thermal projects can be used for heating and cooling.
Solar is one of the fastest growing and cheapest sources of power in the world, and will continue to spread rapidly in the coming years. With solar panel technology improving each year, the economic benefits of solar improve, adding to the environmental perks of choosing a clean, renewable energy source.
Harnessing solar energy for usable power
There are many ways to use energy from the sun. The two main ways to use energy from the sun are photovoltaic and solar thermal capture. Photovoltaic are much more common for smaller-scale electricity projects (like residential solar panel installations), and solar thermal capture is typically only used for electricity production on massive scales in utility solar installations. In addition to producing electricity, lower temperature variations of solar thermal projects can be used for heating and cooling.
Solar is one of the fastest growing and cheapest sources of power in the world, and will continue to spread rapidly in the coming years. With solar panel technology improving each year, the economic benefits of solar improve, adding to the environmental perks of choosing a clean, renewable energy source.
Photovoltaic solar energy
A common way for property owners to take advantage of solar energy is with a photovoltaic (PV) solar system. With a solar PV system, solar panels convert sunlight right into electricity that can be used immediately, stored in a solar battery, or sent to the electric grid for credits on your electric bill.
Solar panels convert solar energy into usable electricity through a process known as the photovoltaic effect. Incoming sunlight strikes a semiconductor material (typically silicon) and knocks electrons loose, setting them in motion and generating an electric current that can be captured with wiring. This current is known as direct current (DC) electricity and must be converted to alternating current (AC) electricity using a solar inverter. This conversion is necessary because the U.S. Electric grid operates using AC electricity, as do most household electric appliances.
Solar energy can be captured at many scales using photovoltaic, and installing solar panels is a smart way to save money on your electric bill while reducing your dependence on non-renewable fossil fuels. Large companies and electric utilities can also benefit from photovoltaic solar energy generation by installing large solar arrays that can power company operations or supply energy to the electric grid.
Solar thermal
A second way to use solar energy is to capture the heat from solar radiation directly and use that heat in a variety of ways. Solar thermal energy has a broader range of uses than a photovoltaic system, but using solar thermal energy for electricity generation at small scales is not as practical as using photovoltaic.
There are three general types of solar thermal energy used: low-temperature, used for heating and cooling; mid-temperature, used for heating water; and high-temperature, used for electrical power generation.
Low-temperature solar thermal energy systems involve heating and cooling air as a means of climate control. An example of this type of solar energy usage is in passive solar building design. In properties built for passive solar energy use, the sun’s rays are allowed into a living space to heat an area and blocked when the area needs to be cooled.
Mid-temperature solar thermal energy systems include solar hot water heating systems. In a solar hot water setup, heat from the sun is captured by collectors on your rooftop. This heat is then transferred to the water running through your home’s piping so you don’t have to rely on traditional water heating methods, such as water heaters powered with oil or gas.
High-temperature solar thermal energy systems are used for generating electricity on a larger scale. In a solar thermal electricity plant, mirrors focus the sun’s rays on tubes containing a liquid that can hold heat energy well. This heated fluid can then be used to turn water into steam, which then can turn a turbine and generate electricity. This type of technology is often referred to as concentrated solar power.
Take advantage of solar energy on your property the best way for individual property owners to save money with solar energy is to install a home solar photovoltaic system. To find the right system for the right price, you should shop on the Energy Sage Solar Marketplace. After signing up, you will receive free solar quotes from qualified, pre-vetted solar installers near you. Looking at quotes in our apples-to-apples setup is a great way to understand offers and compare key metrics such as energy needs met and cost per watt.
Wind Energy is the most mature and developed renewable energy. It generates electricity through wind, by using the kinetic energy produced by the effect of air currents. It is a source of clean and renewable energy, which reduces the emission of greenhouse effect gases and preserves the environment.
Wind power has been used since antiquity to move boats powered by sails or to operate the machinery of mills to move their blades. Since the early twentieth century, it produces energy through wind turbines. The wind drives a propeller and through a mechanical system, it rotates the rotor of a generator that produces electricity.
Wind turbines are often grouped together in wind farms to make better use of energy, reducing environmental impact. The machines have a lifespan of twenty years.
Wind speed
Wind Speed is measured in km's or miles per hour using an anemometer. An anemometer looks like a weather vane, but instead of measuring which direction the wind is blowing with pointers, it has four cups so that it can more accurately measure wind speed. Each cup is attached to the end of a horizontal arm, each of which is mounted on a central axis, like spokes on a wheel.
Wind speed generally increases with height above the earth's surface and is affected by variations such as the roughness of the ground and the presence of buildings, vegetation and other obstacles in the area.
Wind direction
Wind Direction is the direction the wind blows from. North, East, South or West. If the wind is coming from a North direction and blowing to the South, the wind is called a Northerly Wind.
Wind is measured in degrees clockwise from due north and so a wind coming from the south has a wind direction of 180 degrees; one from the east is 90 degrees.
Biofuel any fuel that is derived from biomass that is, plant or algae material or animal waste. Since such feedstock material can be replenished readily, biofuel is considered to be a source of renewable energy, unlike fossil fuels such as petroleum, coal, and natural gas. Biofuel is commonly advocated as a cost-effective and environmentally benign alternative to petroleum and other fossil fuels, particularly within the context of rising petroleum prices and increased concern over the contributions made by fossil fuels to global warming. Many critics express concerns about the scope of the expansion of certain biofuels because of the economic and environmental costs associated with the refining process and the potential removal of vast areas of arable land from food production.
Types of Biofuels
Some long-exploited biofuels, such as wood, can be used directly as a raw material that is burned to produce heat. The heat, in turn, can be used to run generators in a power plant to produce electricity. a number of existing power facilities burn grass wood or other kinds of biomass.
Liquid biofuels are of particular interest because of the vast infrastructure already in place to use them, especially for transportation. The liquid biofuel in greatest production is ethanol (ethyl alcohol), which is made by fermenting starch or sugar. Brazil and the United States are among the leading producers of ethanol. In the United States ethanol biofuel is made primarily from corn (maize) grain, and it is typically blended with gasoline to produce “gasohol,” a fuel that is 10 percent ethanol. In Brazil, ethanol biofuel is made primarily from sugarcane, and it is commonly used as a 100-percent-ethanol fuel or in gasoline blends containing 85 percent ethanol. Unlike the “first-generation” ethanol biofuel produced from food crops, “second-generation” cellulosic ethanol is derived from low-value biomass that possesses high cellulose content, including wood chips, crop residues, and municipal waste. Cellulosic ethanol is commonly made from sugarcane bagasse, a waste product from sugar processing, or from various grasses that can be cultivated on low-quality land. Given that the conversion rate is lower than with first-generation biofuels, cellulosic ethanol is dominantly used as a gasoline additive.
The second most common liquid biofuel is biodiesel, which is made primarily from oily plants (such as the soybean or oil palm) and to a lesser extent from other oily sources (such as waste cooking fat from restaurant deep-frying). Biodiesel, which has found greatest acceptance in Europe, is used in diesel engines and usually blended with petroleum diesel fuel in various percentages. The use of algae and cyanobacteria as a source of “third-generation” biodiesel holds promise but has been difficult to develop economically. Some algal species contain up to 40 percent lipids by weight, which can be converted into biodiesel or synthetic petroleum. Some estimates state that algae and cyanobacteria could yield between 10 and 100 times more fuel per unit area than second-generation biofuels.
Other biofuels include methane gas and biogas which can be derived from the decomposition of biomass in the absence of oxygen and methanol, butanol and dimethyl ether which are in development.
Global warming
Global warming is a term used for the observed century-scale rise in the average temperature of the Earth's climate system and its related effects. Scientists are more than 95% certain that nearly all of global warming is caused by increasing concentrations of greenhouse gases (GHGs) and other human-caused emissions.
Within the earth's atmosphere, accumulating greenhouse gases like water vapour, carbon dioxide, methane, nitrous oxide, and ozone are the gases within the atmosphere that absorb and emit heat radiation. Increasing or decreasing amounts of greenhouse gases within the atmosphere act to either hold in or release more of the heat from the sun.
Our atmosphere is getting hotter, more turbulent, and more unpredictable because of the “boiling and churning” effect caused by the heat-trapping greenhouse gases within the upper layers of our atmosphere. With each increase of carbon, methane, or other greenhouse gas levels in the atmosphere, our local weather and global climate is further agitated, heated, and “boiled.”
Global warming is gauged by the increase in the average global temperature of the Earth. Along with our currently increasing average global temperature, some parts of the Earth may actually get colder while other parts get warmer—hence the idea of average global temperature. Greenhouse gas-caused atmospheric heating and agitation also increase the unpredictability of the weather and climate and dramatically increase the severity, scale, and frequency of storms, droughts, wildfires, and extreme temperatures. Global warming can reach levels of irreversibility as it has now, and increasing levels of global warming can eventually reach an extinction level where humanity and all life on earth will end. Irreversible global warming is partially defined as a continuum of increasing temperature that causes the global climate to rapidly change until those higher temperatures become irreversible on practical human time scales. The eventual temperature range associated with triggering and marking the beginning of the irreversible global warming processes is an increase in average global temperature of 2.2°-4° Celsius (4°-7.2° Fahrenheit) above preindustrial levels.
Extinction level global warming is defined as temperatures exceeding preindustrial levels by 5-6° Celsius (9-10.8° Fahrenheit) or the extinction of all planetary life, or the eventual loss of our atmosphere. If our atmosphere is also lost, this is referred to as runaway global warming. The result would be similar to what is thought to have happened to Venus 4 billion years ago, resulting in a carbon-rich atmosphere and minimum surface temperatures of 462 °C.
The concentration of the human-caused carbon pollution of our atmosphere has nearly doubled in 60 years and it is continuing to escalate at faster and faster rates. Carbon in the atmosphere from fossil fuel burning isn’t our only problem. While the situation is critical, it is still possible to slow and lessen global warming enough for the climate to establish a new, stable equilibrium. However, that equilibrium may be unlike anything previously seen in Earth’s history and it may not be suitable for humanity to thrive.
The most important greenhouse gases (GHGs)
The most common and most talked about greenhouse gases is CO2 or carbon dioxide. In fact, because it is so common, scientists use it as the benchmark or measure of things that warm the atmosphere.
Methane, another important GHG, for example, is 28-36 times as warming as CO2 when in the upper atmosphere (USEPA GWP – Global Warming Potential – estimate over 100 years), therefore, 1 ton of methane = 28-36 tons eCO2 or CO2 equivalents.
The most commonly discussed GHGs are: CO2 or carbon dioxide is produced any time something is burned. It is the most common GHG, constituting by some measures almost 55% of total long-term GHGs. It is used as a marker by the United States Environmental Protection Agency, for example, because of its ubiquity. Carbon dioxide is assigned a GWP or Global Warming Potential of 1.
Methane or CH4 is produced in many combustion processes and also by anaerobic decomposition, for example, in flooded rice paddies, pig and cow stomachs, and pig manure ponds. Methane breaks down in approximately 10 years, but is a precursor of ozone, itself an important GHG. CH4 has a GWP of 28-36.
Nitrous oxide in parean (laughing gas), NO/N2O or simply NOx is a by-product of fertilizer production and use, other industrial processes and the combustion of certain materials. Nitrous oxide lasts a very long time in the atmosphere, but at the 100 year point of comparison to CO2; its GWP is 265-298.
Fluorinated gases were created as replacements for ozone depleting refrigerants, but have proved to be both extremely long lasting and extremely warming GHGs. They have no natural sources, but are entirely man-made. At the 100 year point of comparison, their GWPs range from 1,800 to 8,000 and some variants top 10,000.
Sulphur hexafluoride or SF6 is used for specialized medical procedures, but primarily in what are called dielectric materials, especially dielectric liquids. These are used as insulators in high voltage applications such as transformers and grid switching gear. SF6 will last thousands of years in the upper atmosphere and has a GWP of 22,800.
Depletion of the Ozone Layer
An ozone molecule (O3) is composed of three atoms of oxygen. Ozone in the upper atmosphere (the stratosphere) is referred to as the “ozone layer” and protects life on Earth by absorbing most of the ultraviolet (UV) radiation emitted by the sun. Exposure to too much UV radiation is linked to skin cancer, cataracts, and depression of the immune system, and may reduce the productivity of certain crops. Accordingly, stratospheric ozone is known as “good ozone.” In contrast, human industry creates “ozone pollution” at the ground level. This “bad ozone” is a principal component of smog. The ozone layer is reduced when man-made CFC molecules (comprised of chlorine, fluorine, and carbon) reach the stratosphere and are broken apart by short-wave energy from the sun. Free chlorine atoms then break apart molecules of ozone, creating a hole in the ozone layer. The hole in the ozone layer over the Antarctic in 1998 was “the largest observed since annual holes first appeared in the late 1970s.”10
CFCs were once used in aerosol sprays and as foam blowing agents. Their manufacture is now banned by an international treaty, the Montreal Protocol, signed by 160 nations. But because CFCs have a long atmospheric lifetime (about 50 years), those manufactured in the 1970s continue to damage the ozone layer today. The amount of CFCs in the stratosphere is now peaking. The good news is that scientists forecast that the ozone layer will return to its earlier, stable size by the middle of the 21st century assuming that nations continue to comply with the treaty. When the ozone hole was first detected, there was emotional debate in which many U.S. Industries fiercely resisted a ban on CFCs. It took a few years for scientists to show conclusively that human activity was causing the damage. It did not take long for scientists to invent other chemicals that could replace CFCs for industrial and commercial purposes, but would not harm the ozone layer. CFCs used as propellants were first banned in the United States in 1978.
Ozone is destroyed by chlorine released from manufactured chlorofluorocarbon gases (CFCs) used widely since 1965 as refrigerants, spray-can propellants, solvents, and fire suppressants. Increasing production of CFCs was stopped by 1993 as a result of the United Nations Montreal Protocol on Substances that Deplete the Ozone Layer. This stopped increasing ozone depletion by 1995, stopping increases in global temperature by 1998. Ozone depletion caused by CFCs explains the onset and termination of recent global warming.
Ozone is also depleted by chlorine and bromine gases emitted by active volcanoes, explaining many of the recent regional details in climate change as well as climate change throughout Earth’s history. Explosive volcanoes form aerosols near the ozone layer, reflecting sunlight and cooling Earth. But effusive volcanoes common in Hawaii and Iceland deplete the ozone layer causing global warming. This is good news. We can develop all available sources of energy to meet growing demand without worrying about greenhouse gas emissions. But we do need to find ways to reduce pollution, especially in China, India, and much of Southeast Asia. Ozone depletion increases the risks of sunburn and skin cancer. Understanding that global warming is caused by ozone depletion, not greenhouse gases has major implications for investments in energy.
