The emissions from power plants burning coal and oil keep heat locked inside of the

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1 Alexandria Holmes Literature Review Clean Energy Global Warming and Climate Change The emissions from power plants burning coal and oil keep heat locked inside of the atmosphere; these greenhouse gases are responsible for an interesting phenomenon known as global warming. When gases linger in the atmosphere, they create a thick wall that limits the amount of heat that is able to escape our environment, thus increasing Earth s temperature (Global Climate Change: Causes, 2008). Global warming has many negative effects on the planet: rises in sea level, weather pattern changes, and an increased number of droughts, wildfires, and heat waves. When many of these effects occur at the same time, the outcome can be detrimental for both the earth and its inhabitants (Global Climate Change: Effects, n.d.). The predominant cause of global warming is the creation of large amounts of carbon dioxide gas by fossil fuels. Humanity has a large dependence on fossil fuels; in the past century, fossil fuels have accounted for over four-fifths of the fuels used in the United States (U.S. Energy Information Administration, 2015). In order to hinder global warming and the damage it brings, renewable energy resource usage must increase. Over time, more renewable energy usage can reduce the use of harmful, yet common and widespread, methods of electricity generation, such as fossil fuels and natural gas. An improvement in clean energy usage can decrease carbon emissions, because the need for these methods of power generation would be far less. In

2 Holmes 2 addition, widespread use of clean energy methods can lower levels of pollution by carbon emissions: a direct cause of global warming (Denchak, 2017). What is clean energy? Clean energy is a source of electricity that is produced in a way that has minimal disadvantageous effects on the environment. Characteristics of clean energy sources are renewability and reducibility, which ensure that these resources never run out (Department of Energy: Clean Energy, n.d.). The perpetuity of clean energy is one of the many qualities that makes it sought after, along with the prominent positive impacts on the environment. Clean energy minimizes or eliminates the negative effects of other methods of electricity generation. If current renewable resources are used responsibly and mindfully, a constant supply of energy on Earth can be ensured for centuries to come (Blanchfield, 2011). What are the major types of clean energy? Solar, hydro, nuclear, and wind power are considered the major producers of clean energy. Solar power harnesses the sun s energy to produce electricity. Similarly, hydro and wind power harness the power of water and wind to produce electricity. Nuclear power creates electricity through nuclear fission. These types of energy produce little to no greenhouse gases, and are much better for the environment than fossil fuels. Harnessing energy from natural resources such as these, and using it to produce electricity, is a beneficial alternative to fossil fuels and other non-renewable resources (Department of Energy: Clean Energy, n.d.). What are the benefits of clean energy? Use of clean energy ensures electricity for a long stretch of time. Fossil fuel resources are depleting and will eventually be eradicated completely. Clean energy reduces carbon emissions,

3 Holmes 3 and along with it, the risks associated with global warming. Severe weather, droughts, floods, and other effects of climate change have negative effects on humanity and cause widespread destruction of infrastructure. The economy is also positively impacted by clean energy, as the development of new power plants creates more job opportunities for workers. Additionally, pollution caused by carbon emissions would be reduced with more clean energy usage. As a result, the health risks associated with pollution, which include respiratory issues and damage to the nervous system, would also decrease. Furthermore, the cost of electricity that is made by clean energy is decreasing at a constant rate, while the costs of electricity created by nonrenewable resources, are prone to fluctuation and can be unreliable. Fifteen percent of electricity generation and ten percent of the energy consumption in the United States in 2016 was credited to clean energy resources (Green Mountain Energy, n.d.). Hydropower Hydroelectric Power Hydroelectric turbines create electricity by converting the kinetic energy of flowing or falling water into mechanical energy, which spins a generator in order to produce electricity (Williams, 2005). Because water is continuously brought back by the water cycle, it is considered a renewable resource. Not only is water important for electricity generation, it is essential for life on Earth as well. Water on Earth will never run out or be used up, allowing hydropower technologies to be classified as a clean energy resource (Water Power Technologies Office, n.d.).

4 Holmes 4 Where is hydroelectric power used? Hydroelectric power is used all over the world, in some regions more than others. China, Brazil, Canada, and the United States are all top producers of hydropower, with Russia, Norway, and India following behind (see Figure 1). Figure 1: Top Hydropower Producing Countries measured in Million Tons of Oil Equivalent (Mtoe). (World Energy Council, n.d.). These are not the only countries that produce electricity by utilizing hydropower; the majority of countries worldwide utilize hydropower in some capacity. International use of this clean energy resource is important in both an environmental and economic stance. (World Energy Council, n.d.). How widespread is use in the United States? The only two places in the United States that do not use some form of hydropower to get electricity are Delaware and Mississippi. The other states use varying amounts of hydropower; in

5 Holmes 5 Washington State, hydropower accounts for almost three-fourths of the total electricity consumed. (Water Power Technologies Office, n.d.). What are the benefits of using hydropower? Unlike power plants that burn gas and coal, which pollute the environment, hydropower is a clean resource for energy. Hydropower s versatility helps to reduce reliance on other countries for energy resources such as oil, because many countries have access to flowing water. Hydropower is not limited to certain times of the day or the year like solar power is, because water flow remains relatively constant. In addition, dams and reservoirs used by some hydropower systems can aid in flood control. In places with extreme weather, this contribution is not only helpful, but also essential (Water Power Technologies Office, n.d.). Small-scale hydropower is claimed to be both more reliable and less costly than larger hydroelectric plants. Another benefit of micro hydropower is that it consumes less space and requires less materials (Whitney, E. C., 2017). Hydropower that is small enough to fit inside a house s piping system however, has not been studied significantly, nor proven effective, but innovative thinkers have created their own hydroelectric systems to produce electricity from streams flowing on their own properties. Fluid Dynamics What is fluid dynamics? Fluid dynamics is the study of how fluids move when acted upon by a force. A fluid is defined as being either a liquid or a gas. The type of fluid, its velocity and pressure, and other characteristics play a role in the way a fluid moves. The fluids that are most commonly studied

6 Holmes 6 are water and air, because they are important in daily life. Fluid dynamics is utilized in a wide variety of fields, including the medical, chemical, and even ecological fields (Datta, 2014). How does fluid dynamics relate to hydropower? The application of fluid dynamics to hydropower is important in determining both the amount of energy water has, and the impact that the design of a hydropower system will have on the water flowing through it. If a hydropower system slows the velocity of water significantly, or the incoming pressure is too high, the effectiveness of a hydroelectric turbine can be impacted. Fluid dynamics, in conjunction with Computational Fluid Dynamics (CFD) software, can prevent fatal flaws in a hydroelectric system (Akinyemi, O. S., & Liu, Y., 2015). What is flow? Flow, or the way a fluid moves, is impacted by several factors, namely, density, viscosity, and compressibility. Density is a measure of the ratio of mass to volume of an object. Viscosity is the ability of a liquid to resist flowing. Compressibility is whether the fluid can be compacted to fit into smaller volumes. These factors all help scientists and engineers to predict the ways that a liquid or gas will behave in specific situations with certain criteria. Computational Fluid Dynamics software takes all of these factors into account when running analyses of theoretical systems. The software also allows specific variables, such as velocity and pressure, to be manipulated (Datta, 2014). Bernoulli s Principle The Bernoulli Equation of fluid dynamics relies mainly on the law of conservation of energy, meaning that the energy of fluid in two different parts of a tube is the same, when energy is conserved. The equation relies on the assumption that a fluid cannot be compressed and is

7 Holmes 7 non-viscous. On both sides of the equation, there is pressure, the potential energy of gravity, and kinetic energy. One common way the equation is written is, P i ρv i 2 + ρgh i = P f ρv f 2 + ρgh f, where P is the pressure, ρ is the density, v is the velocity, g is the acceleration due to gravity, and h is the height. This equation helps in fluid dynamics because any of the variables can be solved for, allowing internal flow of fluids in a system to be understood (Datta, 2014). Computer Aided Optimization Computer Aided Design Computer Aided Design (CAD) allows a user to create, manipulate, and display threedimensional designs with ease. There are many CAD programs available for use, including both software and cloud based services. Some of these programs include simulation packages and optimization techniques that display how a design might fare in real world situations. While digital prototypes do not come with the benefit of having a physical object to hold and observe, they come with other benefits that physical objects do not have. Simulation packages and optimization techniques allow a user to test and manipulate a design easily, eliminating the time and cost of prototyping. (Blackwell & Manar, 2015). What does optimization mean? In engineering, optimization refers to running tests on and altering a model until it gives the best output possible. To achieve ideal results from a design, a specific set of adjustable variables, for example, the thickness or curvature of a blade, are manipulated. During

8 Holmes 8 optimization, the ideal model of a design may have a minimized or maximized output. In some cases, optimization can be completed digitally, reducing costs and time needed to complete the process. Optimization is a vital part of the engineering design process, as it helps to provide optimum results (MathWorks, n.d.). Computational Fluid Dynamics Computational Fluid Dynamics, or CFD, allows for the simulation of liquids or gases in a CAD environment. CFD programs can show fluid flow internally or externally acting upon an object. Fluid calculations are complex and timely; CFD makes analysis of fluid flow on a model concise and simple. With digital fluid dynamics software, model analysis is less complex and allows for more precise digital prototyping. Examples of features that can be used in assessments with some CFD software packages are turbulent and laminar flows, heat transfer, compressible and incompressible fluids, and non-newtonian liquids (SolidWorks, n.d.). Electricity Generation Motors and Generators Magnets and coils of wire are the basis of every motor and generator. The rotation of a magnet around a coil of water forces electron movement. Since the basis of electricity generation is the movement of electrons, this interaction between magnets and wires produces electricity. A regenerative motor can be used as both a motor and a generator. Motors use electricity in order to spin, while generators are spun in order to create electricity. Motors, if mechanically spun can be used as generators, as this would cause electron movement within the motor (Caamano, 1998).

9 Holmes 9 Alternating Current Versus Direct Current Thomas Edison invented direct current (DC) in the late 1880 s, which flows in only one direction. One problem with direct current is that it does not easily convert to higher or lower voltages, but with the help of a transformer, alternating current can change voltages easily. Nikola Tesla invented alternating current (AC), which is current that switches directions. Today, alternating current is the main type used for electricity across the United States (Department of Energy, 2014). Although alternating current is more widely used, the United States Department of Energy provides pros and cons for both types of current. While alternating current changes voltages easily, recent advances in technology have allowed direct current to do the same. In addition, direct current is the more stable of the two currents, meaning it can send electricity long distances more effectively. Direct current is also used in technologies that are essential to daily life: computers. Computers are an integral part of life today, and direct current powers not only these, but also other new and emerging technologies (Department of Energy, 2014). How is electricity stored? The Office of Electricity Delivery and Energy Reliability uses many different technologies to store electrical energy, including batteries, flywheels, and electrochemical capacitors. All of these storage techniques are constantly changing and improving, but the most widely used electrical storage device is the battery, due to its relative simplicity. Electrical storage devices are used to store all types of electricity, including electricity produced by clean energy methods. With improved electrical storage and better methods of producing clean energy,

10 Holmes 10 electricity can be ensured for centuries to come (Office of Electricity Delivery & Energy Reliability, n.d.).

11 Holmes 11 References Akinyemi, O. S., & Liu, Y. (2015). CFD modeling and simulation of a hydropower system in generating clean electricity from water flow. International Journal of Energy and Environmental Engineering, 6(4), doi: CAD. (2015). In A. H. Blackwell & E. Manar (Eds.), UXL Encyclopedia of Science (3rd ed.). Farmington Hills, MI: UXL. Caamano, R. A. (1998). U.S. Patent No. US A. Washington, DC: U.S. Patent and Trademark Office. Datta, S. (2014). Fluid dynamics. In K. L. Lerner & B. W. Lerner (Eds.), The Gale Encyclopedia of Science (5th ed.). Farmington Hills, MI: Gale. Denchak, M. (2017, July 17). How You Can Stop Global Warming. Retrieved November 13, 2017 from Department of Energy. (n.d.). Clean Energy. Retrieved November 13, 2017 from

12 Holmes 12 Department of Energy. (2014, November 18). The War of the Currents: AC vs. DC Power. Retrieved November 24, 2017 from Global Climate Change. (2008, June 15). Causes. Retrieved November 13, 2017 from Global Climate Change. (n.d.). Effects. Retrieved November 13, 2017 from Green Mountain Energy. (n.d.) Benefits of Clean Electricity. Retrieved November 13, 2017 from MathWorks. (n.d.). Design Optimization with MATLAB and Simulink. Retrieved November 17, 2017 from Office of Electricity Delivery & Energy Reliability. (n.d.). Energy Storage. Retrieved November 24, 2017 from SolidWorks. (n.d.). Computational Fluid Dynamics (CFD). Retrieved November 19, 2017 from

13 Holmes 13 U.S. Energy Information Administration. (2015, July 2). Today in Energy. Retrieved from Water Power Technologies Office. (n.d.). Benefits of Hydropower. Retrieved from Whitney, E. C. (2017). Hydroelectric generator. Renewable and Sustainable Energy Reviews, 72, doi: /j.rser Williams, H.L. (2005). U.S. Patent No. US B2. Washington, DC: U.S. Patent and Trademark Office.