Hydroelectric Power Jackie Richards 1 & Greg Samuels 2 1 Department of Chemical and Biochemical Engineering, 2 Department of Mechanical and Industrial Engineering, 52:133:001 Engineering Analysis of Alternative Energy Systems, The University of Iowa Figure 3. Schematic of (impoundment) hydroelectric power plant Courtesy of HowStuffWorks.com Advantages of Hydroelectric Power Hydroelectric plants can be constructed anywhere there is a water source; so it is a secure form of domestic energy. Hydroelectric power is renewable. No pollution is created by the process. There is no carbon dioxide emission. It is very cheap to maintain a facility which keeps cost of electricity low to consumers (about $0.07 per kWh). How a Hydroelectric Facility Works Kinetic energy in moving water is converted to mechanical energy in turbine machinery and then to electrical energy Water is let into the system through the use of a dam and a reservoir. The moving water spins the blades of the turbine. The shaft spins with the rotating blades. The spinning shaft turns the rotor in a generator, creating A/C current. Electricity is transferred away from the power plant by power lines. References See Hydroelectric Power Wiki for complete list of references: Disadvantages of Hydroelectric Power The initial construction of a hydroelectric power plant requires a large capital cost and a lot of time ($1700 – 2300/kW). Pay back period = 10+ years, depending on plant’s kW size. Hydroelectric dams impact the migration and population of fish because they can become obstructed in the dam. Power plants affect the temperature of the water; adversely affecting the native plants and animals in the water and on land. The construction of dams and reservoirs may require the destruction of homes and relocation of people. The use of a power plant is dependent on climate because it requires rain and precipitation to build a reservoir. Power Generation The actual power generated by a hydroelectric power plant is defined as: P actual = (η total ) ρ Q H g and η total = 80-95% η total is the combined efficiency of power generation including water energy extraction efficiency, mechanical efficiencies, and electrical efficiencies. Figure 4. Definition of power generation variables. Courtesy of Encyclopedia of Alternative Energy and Sustainable Living Hydroelectricity in the U.S. Current U.S. hydroelectric generation amounts to about 95,000 MW, which is enough to power 28 million households. Figure 1. Electricity generation profile for the U.S. Courtesy of U.S. Energy Information Administration Objective The project’s goals were: Research the various aspects of hydroelectric power Compile information into a highly intuitive and instructive web page, or “Wiki.” The research focused on: Hydroelectricity usage in the U.S. Design and operating principles of hydroelectric facilities Advantages and disadvantages of hydroelectric generation Future of hydroelectric power in the U.S. Figure 2. Map of current and potential hydroelectric facilities in the U.S. Courtesy of U.S. Department of Energy Flow Rate Q = V∙A g = gravity accel. ρ = water density The Future of Hydroelectric Power in the U.S. The U.S. Department of Energy concluded that the entire 50 states have approximately 30,000 MW of undeveloped potential hydroelectric capacity. Due to high capital costs, long pay back periods, and extended construction times, large-scale (30+ MW) hydroelectric facilities are economically unattractive. Development of small scale (100 kW – 30 MW) and micro scale (less than 100 kW) hydropower facilities has promise in the future.