Preserving Marine Life While Increasing Hydroelectric Efficiency: Four Lower Snake River Dams
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Preserving Marine Life While Increasing Hydroelectric Efficiency: Four Lower Snake River Dams Kaitlyn DeGroot Rajas Karajgikar [email protected] [email protected] Max Milone Pranav Penmetcha [email protected] [email protected] Olivia Wang [email protected] July 22, 2016 The New Jersey Governor’s School of Engineering and Technology Abstract Kaplan turbines, and temperature regulat- ing systems, were implemented into an ideal Hydroelectric dams are the most widely dam design. This design also includes mod- used source of clean energy, but they are ified turbine screens, Western White Pine also harmful to the marine life in the rivers trees along the bank of the water, and a and reservoirs the dams are built on; for siphon spillway system with a piano key these reasons, an exploration of dams is weir. The ideal dam design serves to pro- necessary. The four Lower Snake River mote features of dams that would enhance dams were identified as dams with mul- hydroelectric production and marine life tiple issues including hydroelectric ineffi- sustainability. Though the ideal dam design ciency, dangers in the turbine pathway for was made to resolve problems specific to the fish, sedimentation buildup, flooding, and four Lower Snake River dams, the overall temperature fluctuations in the water. The system can be implemented in other dams complications that arise from the construc- to address similar issues and to prevent the tion of dams threaten marine life popula- same problems. tions, and they can permenently damage an ecosystem. People living near dams may face problems such as property damage 1 Introduction and power shortages. To address these is- sues, original components of the four Lower The first known dam was built in Egypt Snake River dams, such as bypass systems, around 2950-2750 B.C., and since then, 1 dams have transformed and are being built area, specifically the juvenile salmon popu- for the purpose of generating power through lation. These disadvantages present issues hydroelectricity [1]. Unlike fossil fuels, hy- that would ultimately threaten the wildlife droelectric dams can complete various tasks and humans in the Snake River ecosystem. without producing greenhouse gases and By identifying specific components of the harming the environment. Although hy- four Lower Snake River dams and research- droelectricity itself is not dangerous for the ing the applications of those specific compo- environment, recent research demonstrates nents, the ultimate causes of the major is- that dams can have drastic consequences. sues of the dams could be addressed. Re- The allocation of water in reservoirs cre- search in the four Lower Snake River dams ated by dams disrupts native fish popula- offers the potential to establish solutions to tions that use the rivers as a breeding and varying issues involving hydroelectric effi- living area, in essence destroying the habi- ciency and marine life preservation. tat of marine species. In addition, dams erode the downstream river banks by caus- ing a buildup of sedimentation [2]. Hydro- electricity, although inexpensive when com- pared to other clean energy obtaining meth- ods, is still considered costly due to the ex- penses of construction, maintenance, and future repairs of dams. As a result, civil en- gineers that work with dams are confronted with the question of efficiency versus cost; therefore, it is important for civil engineers to visualize a dam which can generate a large amount of electricity without harming the aquatic ecosystem, while also considering the cost of its construction. Four large hydroelectric dams were built by the federal government on the Snake River in the 1960s and early 1970s. The four Lower Snake River dams are storage Figure 1.1: dams which are used as reservoirs for wa- This map shows the Snake River system, ter [3]. The four Lower Snake River dams which includes the four lower Snake River have numerous benefits essential for the dams and the Dworshak Dam [5]. community surrounding the Snake River. The benefits of the dams include provid- ing emission-free renewable energy and power to the Northwest, stabilizing the 2 Background Snake River system, contributing to trans- mission system reliability, supporting wind 2.1 Hydroelectricity power, and assisting in irrigation [4]. De- spite their advantages, the four Lower Snake With various energy transformations, River dams have drawbacks which nega- dams can generate a substantial amount tively affect the marine life that inhabit the of hydroelectric power. When water flows 2 from a high to low elevation, potential en- bine. Examples of gravity turbines include ergy is converted into kinetic energy. The the reverse Archimedes Screw and the over- resulting kinetic energy is then converted to shot water wheel. mechanical energy by the turbines in a dam. The most efficient types of turbines are When a generator turns, the mechanical en- the Pelton and Kaplan turbines, which work ergy formed by the turbine is then converted well even below the design flow, or the into electrical energy, which is essentially amount of water the turbine was meant to be the hydroelectric power. Electric efficiency used for. Unlike these turbines, the Cross- is enhanced when large quantities of poten- flow and Francis turbines only work effec- tial energy are stored. For instance, when tively for the design flow [8]. Thus, in sit- dams have larger heads, or longer distances uations where dams may be holding less between the source of the water and the tur- water than their full potential, the Cross- bine, the water gains more potential energy flow and Francis turbines will be ineffec- as it travels farther. If dam pipes are larger, tive. Between the Pelton and Kaplan tur- more water volume is present, which causes bines, which have proven success rates, the a larger amount to pass through the turbines Pelton turbines are generally cheaper. The and generate hydroelectricity. The dams cost of these turbines can be modeled by the manipulate energy transformations to gen- formula: erate hydroelectric power for the surround- 0:54 ing community [6]. C = 8300(QH) (1) ”Q” is the flow rate in meters cubed per sec- ond and ”H” is the length of the head in me- 2.2 Turbines ters. The cost of Kaplan turbines can be modeled by the formula: Dams generate hydroelectricity by using turbines. The type of turbine selected for C = 15000(QH)0:68 (2) a given dam has a direct correlation with cost, efficiency, and marine life. Turbines ”Q” and ”H” take on the same units as in come in three varieties: impulse, reaction, the aforementioned formula [9]. However, and gravity. Impulse turbines work because in terms of preserving marine life, neither they are driven by jets of water which travel the Pelton nor the Kaplan turbines would at high velocities. Examples of impulse tur- be the best choice. Pelton turbines, due to bines are the Pelton and Crossflow turbines. their design, cause virtually 100% fish mor- Unlike impulse turbines, reaction turbines tality and Kaplan turbines have a fish mor- utilize a rotor which is submerged in wa- tality rate between 5-20%. Large, lowhead ter and placed in a casing. Pressure differ- turbines lead to eel mortality rates of 10- ences on opposing sides of the blades of the 20%, and smaller turbines found in typical turbine cause the rotor to rotate. Examples hydroelectric power plants cause fish mor- of reaction turbines include the Francis and tality rates of 50%. Mortality rates are high Kaplan designs, which are similar in compo- because fish are unable to survive passing sition and are commonly used due to their through turbines which can cause shearing efficiency [7]. Gravity turbines are driven effects and abrasion [9]. The best alterna- by the water which falls from the top of the tive is the Alden turbine, which is consid- turbine to the bottom. The water’s weight is ered fish-friendly due to its 98% survival the force behind the functionality of this tur- rate. In terms of efficiency, Alden turbines 3 are only 1% less efficient than Kaplan tur- ence of their heads, juvenile fish have an bines, coming in with a 94% rate [10]. increased chance of passing through the The four Lower Snake River Dam sys- holes of the turbine screens. Since the four tem consists of the following dams: the Lower Snake River dams have Kaplan tur- Ice Harbor, the Lower Monumental, the bines, once a fish passes through the screen, Lower Granite, and the Little Goose. Each it has a high chance of dying by the tur- of these dams have Kaplan turbines, with 6 bine. Another predicament is that the cur- blades each. Due to the amount of blades, rent turbine screens, themselves, pose a life- large structure, and complex composition, threatening risk to the fish. Since the size of the turbines produce, on average, 212,400 the turbine screen is not much larger than horsepower, or 158,390,000 Watts [11]. the actual turbine itself, the fish are exposed to an area where they can easily be sucked in or get stuck on the turbine screen and 2.3 Turbine Screens be unable to escape. Stainless steel is most effective for the turbine screens, because it Turbine screens are a crucial component is highly effective, inexpensive, and com- of many dams that serve the purpose of in- monly available [14]. Stainless steel is ap- creasing the survival rate of fish traveling proximately 489 pounds per cubic foot [15], through a turbine passage. These screens and costs $300 per metric ton [16]. serve to divert fish away from the turbine while still allowing water to flow through the turbine. 2.4 Spillways The four Lower Snake River dams have turbine screens that generally resemble a A spillway is a structure used to provide conveyor belt.