Content Objectives
Defining Energy
Generally speaking, energy is most often defined by textbooks as the ability to cause change or do work. What I have discovered is energy is much more complex than that. Energy, albeit abstract, is relevant to all disciplines of science and applies to all known natural phenomena. The reason it is applicable to all natural phenomena is because it is always conserved. Any process that increases energy must be coupled with another process that decreases energy. This reasoning allows scientists to hypothesize undetected processes opening the field for more scientific discovery.3
Students develop their own conceptions of energy long before they are explicitly introduced to it in my classroom. Most often students’ preconception of energy is that energy is only present in living things or changing things. This does not align to the complete scientific understanding of energy. Thus, before indulging on any topic where energy is the driving concept, it is important to first define energy in a way that will be helpful to reference.
Energy is most easily classified into two different overarching types; kinetic energy and potential energy. Kinetic energy is energy associated with movement. It can be quantified using the formula ½mv2, where m represents the mass of the object and v represents the velocity of the object. From this equation, we can deduce that the quantification of kinetic energy is proportionally related to the mass and velocity of an object; as one increases so does the other. Potential energy is energy associated with height and often referenced as stored energy. Potential energy can be quantified using the formula mgh, where m represents the mass of the object, g represents the acceleration of gravity and h represents the height of the object above a reference height. Again, the relationship between energy and these variables is proportional.
There are other forms of energy that fall under the overarching categories of potential and kinetic energy. For example, kinetic energy can be observed in the forms of mechanical, light, electrical, thermal or sound energy. Potential energy is associated with elastic, chemical, nuclear and gravitational energy. Students are typically most familiar with gravitational potential energy, so in thinking about carbon emissions it is important to introduce students to other types of stored energy like chemical energy. An important characteristic of any type of energy is that it can be transformed, which we will look at in more detail in the next section.
Energy Transformation and Conservation
When you walk into a dark room most likely the first thing you will do is look for a light switch. You flip the switch and instantaneously the room fills with light. You probably don’t think about the processes that are involved for this simple luxury to occur. Humans are constantly interacting with energy all the time. As mentioned in the previous section, there are different types of energy but regardless of what type of energy it cannot be observed directly with the eye. What we as humans do observe about energy is the result of energy transfers and transformations.
What may be hard for students to wrap their head around is the idea that energy is not a physical substance. When thinking about energy conservation, one must first define the system they are observing. There are two types of systems, closed systems and open systems. In a closed system, as processes occur, the amount of energy should remain the same at the beginning and end of the process(es). On the other hand, in an open system the initial quantity of energy that you start with may change as the energy is transformed into other forms of energy leaving that particular system and entering a different system. It is also possible that the initial quantity of energy can increase and in that case it would still imply the system is an open system and energy from another system is entering the observed system.
In everyday life, we mostly observe examples of energy transforming and transferring between different systems. For energy to be transformed, it changes from one type to another. Energy is never lost, though. An example of this would be the chemical energy in a battery, which transforms into electrical energy in a flashlight as it shines, which then emits light energy and thermal energy. The light and thermal energy are the same entity of energy that was initially stored in the battery but that energy is now expressed as two different types of energy as the battery powers the flashlight. The ability of energy to be transformed into the different forms of energy is what makes energy so critical for life. Humans rely on energy transformation to sustain our life in many ways. We utilize energy from the food we eat to carry out complex life processes, we use electrical energy to power our electronics, chemical energy is used for transportation modes, etc.
When talking about carbon dioxide emissions, we can further explain energy transformation throughout the chemical process of combustion of fossil fuels. We as humans burn fossil fuels so that the result is energy that we can use to carry out technological processes like providing heat for homes and buildings, running engines or producing electricity. In the combustion of fossil fuels, hydrogen molecules from the fuel and oxygen molecules in the air collide with enough speed that they break apart releasing the chemical energy stored in the bonds. Because the free atoms are close to each other, they begin to attract one another again in such a way that they form the lowest available potential energy arrangement. The difference in potential energy from the end state to the beginning state is typically manifested in even faster motion of the molecules.4 The resulting higher temperature means that the molecules have greater kinetic energy, which can then be used to initiate other processes. For example to generate electricity, the hot gases can interact with water turning it to steam which in turn will transfer the steam molecules’ kinetic energy to a turbine in a generator transforming the energy into electricity for use. In this process, we started with chemical potential energy in the fossil fuel, it transformed into kinetic energy in the form of heat, which then transformed into chemical energy as it heated water into steam. The steam transformed into mechanical energy as it turned the turbine. Finally, the product of the initial energy was given off as electrical energy and thermal energy.5 This is just one example of how humans are able to harness energy from fossil fuels. Subsequent sections will go more into detail about what other sources of energy are available and how energy is harnessed from them.
Nonrenewable Energy: Fossil Fuels
Nonrenewable energy refers to primary sources of energy that cannot be replenished once they run out. The most common types of nonrenewable energy sources are oil, natural gas and coal. These three types of sources are considered fossil fuels because they are the remains of plants and animals from millions of years ago.
Oil
Oil is a hydrocarbon, meaning that it is composed of hydrogen and carbon. It is formed from when dead organic material, typically plankton, mixes with inorganic material and sinks to the bottom of the ocean. This mixture continues to get buried by sediment and becomes sedimentary rock. The sedimentary rock is also known as organic shale. As this shale continues to be buried and increased in pressure it turns into a substance known as kerogen and this type of shale becomes known as oil shale. “If temperatures of the kerogen are greater than 90°C but lower than 160°C, the kerogen is transformed into oil and natural gas.” In order to accumulate, there must be some sort of reservoir with a top layer that does not allow the oil or natural gas to escape. Oil eventually rises through small pores in rocks where it must be contained in a reservoir until is drilled into and obtained by humans.6
From oil we can make petroleum that is used in gasoline, which means it is essential for use in transportation. “Gasoline is the most consumed petroleum product in the United States. In 2017, consumption of finished motor gasoline averaged about 9.33 million b/d (392 million gallons per day), which was equal to about 47% of total U.S. petroleum consumption.” In an engine, there are different parts to it that allow fuel to enter and begin a combustion reaction by also allowing air into the same compartment. Once the combustion reaction occurs, the product provides the kinetic energy needed to make the mechanical processes of the vehicle work.7
Natural Gas
Methane is the equivalent of natural gas. Methane is composed of hydrogen and carbon, making it a hydrocarbon. Natural gas is formed in the same manner as described for oil. The only difference is the temperature range for its formation. Natural gas can form at temperature ranges of greater than 90°C.8
“Most U.S. natural gas use is for heating buildings and generating electricity.” Once natural gas is extracted for use, it is transported via pipelines to facilities where impurities are extracted and a combustion reaction chamber is used to power a steam turbine or combustion. The turbine then generates electricity for human use. Natural gas can also be used for cooking and heating homes via a central heating system.9
Coal
As plant matter dies and eventually becomes buried, anaerobic bacteria will begin to decompose the matter. It can accumulate for thousands of years forming several meters of decayed plant matter. As time continues to pass and more matter continuously buries the matter, increasing pressure and temperature will transform through a cycle of different types of coal. More time will equate to a higher quality of coal. Each type of coal releases different amounts of CO2.10
About 27% of electricity generation came from coal in the U.S. in 2018. Power plants burn the coal to create steam that in turn will power a turbine to generate electricity. In addition to be used for electricity, coal has other uses. It can be used to create steel or it can be turned into other gases or liquids to be used in fuels or other products.11
Renewable Energy: Solar and Wind
Renewable energy is energy that can be replenished naturally. Some examples of renewable energy sources include: solar, wind, hydropower, geothermal and biomass. “In 2018, renewable energy sources accounted for about 11% of total U.S. energy consumption and about 17% of electricity generation.”12 Using renewable energy sources could significantly reduce our carbon emissions, but I will go further into detail on that in future sections. In this unit, I will introduce students to the different sources of renewable energy but we will dive deeper into exploring sun and wind energy because these two types have the most implications for Chicago energy.
Solar Energy
“Solar Energy is, in fact, the only renewable resource that has enough terrestrial energy potential to satisfy a 10-20 TW carbon-free supply constraint in 2050.”13 In other words, utilizing solar energy alone would be enough to provide a carbon-free solution to energy usage on a global scale. The U.S. is responsible for about 3 TW of this total energy supply. So, why don’t we? One issue is a mismatch of supply and demand. Solar energy is intermittent since it is only available for part of the day. At night and in the winter, when the demand for heat is high, solar energy is not as widely available. A second issue is the amount of land needed to harness the sun’s energy. If we consider the U.S. alone, we would need to cover a land area relative to the size of Iowa in order to produce enough power for just the U.S.’s energy use. Despite these two disadvantages, the advantages are compelling. Solar energy is free, limitless, widely dispersed and has a low-environmental impact. A trending issue that is continuing to be researched is energy storage from solar power. One of the more popular ways to currently harness the sun’s light energy is using photovoltaic cells. Photovoltaic cells are made of many silicon units that are doped with phosphorus or boron. This doping gives a junction that produces a electric field to eventually send electrons through to a circuit in order to create an electric current to provide electricity. Other ways to harness solar energy include solar thermal to produce heat and concentrated solar power to also produce electricity.14
Wind Energy
According to Nate Lewis’s research, the “offshore electrical power potential of wind is larger than 2 TW”.15 Again, this just about matches the amount of energy supply the U.S. is currently using. One of the disadvantages to offshore wind turbines is transmission: transporting the energy to onshore facilities for supply. This idea of mismatched supply location and demand location continues to play a role when analyzing “hot spots” for harnessing wind energy. Of course, energy storage is also still a challenge in utilizing wind energy since it is another source, just like solar, that requires use after generation. Another implication of using wind energy that is still being studied is the effect it would have on local weather and surface temperatures. By harnessing wind, we are mixing different energy levels from the atmosphere. “According to temperature readings from one of the oldest wind farms in the U.S., near Palm Springs, California, the turbines make it warmer at night and cooler during the day, generally speaking.”16 This effect on surface temperatures could have other impacts, but more research is needed to prove any correlations between wind turbines and weather and climate. One definite environmental impact human’s use of wind energy can have is reducing the emissions of carbon dioxide, thus giving this harnessing source contention to be at least one solution to climate change. In order to harness the energy of the wind, the blades are turned by the wind producing kinetic energy. That energy turns a shaft, which transfers the kinetic energy to a generator to generate electricity.17
Earth’s Rising Temperature
Over 80% of America’s energy is supplied by the combustion of fossil fuels.18 Combustion involves burning a hydrocarbon by quickly reacting it with oxygen and producing carbon dioxide, water and heat. The fossil fuels we use to produce our energy are all examples of hydrocarbons.19 Burning fossil fuels is the first contributing factor to the rise in our global temperature. Typically, nature regulates the amount of CO2 in the atmosphere through natural process. This is known as the carbon cycle. In a slow carbon cycle, it takes millions of years for atmospheric carbon to move between the components of Earth’s system. Carbon is stored in fossils and can remain there for millions of years.20 Humans are the major disruptors of this natural process though. As humans continue to burn fossil fuels, they continue to increase the levels of carbon dioxide in the atmosphere. A full analysis on the effect of humans burning fossil fuels requires some history. The first point of history to consider is the Industrial Revolution, which started in 1769 when James Watt patented his steam engine. Britain’s use of coal increased two fold every 15-20 years from 1769 to 1850. Coal was “used to make iron, to make ships, to heat buildings, to power locomotives and other machinery, and of course to power the pumps that enabled still more coal to be scraped up from inside the hills”. The success Britain experienced with coal production spread throughout the world, and even when coal production slowed down in Britain it still increased across the rest of the world.21 The second point in history to consider is data collected by Charles David Keeling. Keeling was one of the pioneers in analyzing atmospheric carbon dioxide levels. In 1959, Keeling began monitoring carbon dioxide levels atop Mauna Loa in Hawaii. At that time, the average concentration of CO2 in the atmosphere was 316 parts per million (ppm). As Keeling conducted his research, each year’s measurement of the CO2 level increased. By 1980 it was about 345 ppm and by 2019 it rose to 409 ppm.22 His data became known as the Keeling Curve, which provided clear evidence that atmospheric CO2 levels were increasing.23 Considering the data, it supports a correlation between an increase in energy production by technologies and an increase in carbon dioxide levels.
Figure 1. Keeling Curve displays the CO2 levels from atop the Mauna Loa research facility. Source: Mauna Loa Observatory, https://www.esrl.noaa.gov/gmd/obop/mlo/ (Accessed July 16, 2019)
How does carbon dioxide relate to global temperatures? First, we must understand the system we live in, Earth. A blanket of gases called the atmosphere surrounds Earth. This atmosphere separates Earth from outer space. It surrounds the Earth and is made up of gases and is a huge factor in what allows Earth to be habitable. There is a multitude of different gases that make up the atmosphere: carbon dioxide, methane, nitrous oxide, industrial gases, water vapor and ozone. The composition of these gases making up the atmosphere blanketing Earth creates something called the greenhouse effect. The sun radiates solar energy towards the Earth, the surface of the Earth radiates heat energy outwards. Some of this heat radiation passes all the way back out through the atmosphere but some is absorbed and re-emitted by greenhouse gases. This cycle is known as the greenhouse effect and is responsible for maintaining the temperature of the Earth. Without the atmosphere, the Earth would not be able to sustain life because it would be far too cold.24 As previously mentioned, nature has a system for cycling this energy from the sun that allows for habitable conditions. However, humans add to this natural amount of CO2 in the atmosphere when they burn fossil fuels. There are other greenhouse gas emissions that contribute to the rise in greenhouse gases, but “in 2016, fossil fuels were the source of about 76% of total U.S. human-caused greenhouse gas emissions”, so I will continue to focus on that cause.25
Figure 2. A diagram that explains the stages of the Greenhouse Effect. Source: "The Greenhouse Effect" in: "Introduction," in: US EPA (December 2012) Climate Change Indicators in the United States, 2nd edition, Washington, DC, USA: US EPA, p.3. EPA 430-R-12-004.
Human Activity and Environmental Consequences
This increased amount of CO2 is almost inarguably what is contributing to climate change. The danger in changing the climate over time is that is has strong effects on weather, which has more immediate consequences for current society. Success of past civilizations depended on the resources provided by nature and the use that humans created for them. The innovation that has come from humans constantly developing new technology from Earth’s resources is undeniably extraordinary. However, this innovation is not without a cost to the environment itself. We refer to nonrenewable resources as “nonrenewable” because they will eventually become finite, even if it’s not within our lifetime. The rate at which humans consume these resources has the most impact on climate. Climate and weather are related but not interchangeable. Weather refers to the day-to-day conditions of the atmosphere, whereas climate refers to a range of a region’s weather. The cause behind the changes in weather and climate stem from the sun’s heat and light energy that is emitted. As the heat from the surface of the Earth heats the atmosphere above it, it “leads to the development of a dynamic mix of water and gases at various temperatures and densities in the atmosphere that move around constantly, creating weather phenomena that are constantly changing yet relatively predictable.”26 Climate change is most exemplified through more extreme weather events like droughts or intense precipitation. As the increased levels of CO2 enter and remain in the atmosphere trapping heat, it results in changing the way the atmosphere absorbs and transports the energy over long distances, while also altering the water cycle. In addition, the increased energy can cause the polar ice sheets to melt which results in a rise in sea level and less reflectivity from the Earth’s surface again inciting another change in the energy balance between the sun and the surface of the Earth. Lastly, another impact to consider is the heat capacity of water. Water has a much higher heat capacity than air and therefore will also trap heat much more easily warming the ocean and affecting the ocean currents.
Reducing the Impact of Human Activities on the Environment
One obvious way to reduce the impact of human activities on the environment is to begin switching our energy sources to renewable energies. From my research, in order to provide the world with enough energy I think the best course of action would be to use a mixture of many types of renewable energy dependent on region. Our world regions can be vastly different from one another, so it makes sense that we should adapt our energy sources to what is most abundant and available in that region. In a study completed by a Stanford engineer, Mark Jacobson, he proposed a state-by-state plan to achieve 100% renewable energy by 2050. It is possible! He listed the biggest challenges to his plan or any plan for a renewable energy transition as social and political barriers.27
There are some examples of major cities around the world that have considered their environmental impact and they have begun to make changes to reduce those impacts. Some examples of what cities are doing to combat carbon emissions include:
- Berlin is phasing out coal use.
- Copenhagen is developing 100 MW of wind power and electrifying their bus fleet.
- New York City is continuously implementing more solar power.
- Rio de Janeiro built a ten-mile metro line and added more bus transit lines.
- Washington D.C. designed a Green Bank to finance local renewable and energy-efficient projects.28
These are just small changes that cities are implementing to begin moving toward a carbon-free future. Ultimately it is up to cities to consider, update and implement new energy policies.
Another way to combat carbon emissions is carbon sequestration, which is a way to capture CO2 from the air and store it. There are two types of carbon sequestration: biologic and geologic. In geologic carbon sequestration, carbon dioxide is captured from stationary sources, like a power plant. The captured gas is compressed until it takes on a liquid state and injected underground into porous rocks.29 In biological sequestration, storage in wood by reforestation or in microalgae that utilize the CO2 captured from flue gases and controlled light to carry out photosynthesis to produce biomass.
A Closer Look at Chicago’s Energy
The Statistics
According to the American Lung Association, Chicago ranked as the 19th most polluted city in the United States.30 91% of Chicago’s emissions came from electricity, natural gas and transportation. “Without mitigation, Chicago’s emissions of 12 tons of carbon dioxide equivalent per capita in 2000 would be expected to grow 35 percent by 2050.”31
Assessment
As with any region, there are many effects that global climate change can have on Chicago. The National Climate Assessment listed six key effects carbon emissions and increasing temperatures will have on the Midwest region. Among the effects are impacts on agriculture, forest composition, public health, fossil-fuel dependent electricity system, rainfall and flooding, and the health of the Great Lakes.
Temperature
If emissions conditions stay the same, Chicago is projected to increase two degrees Fahrenheit in annual average temperature. This would also play a role in lengthening the growing season for agriculture and reduce the number of extremely cold days by 30%. On the other hand, there would also be an increase in extreme heat days, which are days over 90 degrees Fahrenheit. This would be linked to a higher frequency of heat waves, which can mean several every year if high carbon emissions hold. More heat waves could potentially mean more deaths.32
Air Quality
“As temperatures warm and atmospheric circulation patterns change, bringing oppressive summer weather patterns to Chicago earlier in the year and making them last longer, ground-level ozone and particulate matter concentrations are projected to rise.” There is an expected increase in the concentration of ground level ozone anywhere from 10-25% depending on the level of carbon emissions. High carbon emissions would mean higher ozone levels. Increased ozone could mean increased health issues in addition to ecosystem and agricultural instability.33
Public Health
Increased ground level ozone could mean increased health issues, especially for those people with asthma and other respiratory illnesses. “Breathing ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and congestion. It can worsen bronchitis, emphysema, and asthma. "Bad" ozone also can reduce lung function and inflame the linings of the lungs. Repeated exposure may permanently scar lung tissue.”34 Increased health issues without proper access to healthcare can lead to more morbidity.
Precipitation
Increased carbon emissions projects increased precipitation in the winter and spring. Increased precipitation can pose significant flood risks depending on infrastructure. It is noted that Chicago has experienced flooding in the past with rains totaling 2.5 inches in a 24 hour period and continuing to increase carbon emissions will increase the frequency of heavy rain periods. As far as winter precipitation, since temperatures would be expected to warm, this would mean less snowfall or decreased snow cover.35
Chicago Climate Action Plan
As a result of the research on Chicago’s impact on carbon emission, Mayor Richard M. Daley designed a task force to tackle and propose a plan to reduce Chicago’s carbon emissions in 2008. The goal of the Chicago Climate Action Plan is to reduce greenhouse gas emissions by 80% from the 1990 level by 2050. The task force developed the Chicago Climate Action Plan, one of the first organized plans for a major city in the U.S. In the plan were five strategies proposed to lead Chicago to an overall reduced greenhouse gas emissions level. The first strategy is to reduce energy use in all building by retrofitting existing buildings. Retrofitting could include improving insulations, installing energy efficient windows or installing high efficiency furnaces and boilers. The second strategy is to implement clean and renewable energy sources. Chicago has the potential to replace existing energy sources with photovoltaic and wind energy. The third strategy is improving transportation options. This strategy includes investing in transit incentives, expanding clean transit options, improving fleet efficiency, switching to cleaner fuels, etc. The fourth strategy is reduced waste and industrial pollution. This would mean revamping the recycling system and encouraging citizens to reduce, reuse and recycle. The last and fifth strategy is adaptation. This strategy includes managing urban heat islands, protecting air quality and managing storm water. Within each of these strategies there are proposed actions that are suggested at both the industrial and residential levels. It is believed that implementation of these strategies can reduce greenhouse gas emissions over time and if not taken the effects could be dire.36
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