Geothermal Energy Exercises

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Exercises I. Essay Questions 1. What countries have the most potential for using geothermal energy? 2. Describe the principal of operation of geothermal heat pumps. Where can they be used? 3. Can geothermal energy be considered a renewable energy? Explain. 4. What are the uses for low-temperature geothermal resources? 5. How can we use the earth’s temperature gradient to drive a heat engine? 6. What are the factors that constitute a good geothermal location? Where are such sites located? 7. Explain how chemical geothermometry works and how it is used to explore the ideal sites for geothermal excavation? 8. With current technologies, which types of geothermal sources can be exploited? 9. Is geothermal renewable? Sustainable? Explain. 10. What are the environmental considerations of geothermal energy? II. Multiple Choice Questions 1. How do temperature and pressure vary with depth inside the earth? a. Both temperature and pressure increase with depth. b. Temperature increases with depth, but pressure decreases. c. Pressure increases with depth, but temperature decreases. d. Temperature increases with depth, but pressure remains relatively constant. e. Both temperature and pressure decrease with depth. 2. What distinguishes earth’s inner and outer cores? a. Because of its extreme temperatures, the inner core is a gas. The outer core is cooler and remains liquid. b. Both the inner and outer cores are liquid. The only difference is their temperatures. c. Both the inner and outer cores are solid. The only difference is their temperatures. d. The inner core is liquid. It solidifies gradually as temperature drops toward the surface. e. The inner core is solid. The outer core is liquid. 3. The inner core is composed mostly of a. Iron b. Silicon c. Sulfur d. Oxygen e. Steam 4. The average thickness of the crust is a. Less than 1 km b. 30-50 km c. 100-200 km d. 200-1000 km e. More than 1000 km 5. Where is the source of earth’s magnetic field? a. Crust b. Mantle c. Inner core d. Outer core e. Electromagnetic radiation from the sun 6. Today, which renewable energy sources provide the US with the most energy? a. Solar b. Wind c. Hydropower d. Geothermal e. Waves and Tides 7. On average, the energy available from geothermal resources a. Is much greater than the solar influx b. Is about the same as the solar influx c. Is much less than the solar influx 217 Chapter 9 - Geothermal Energy 8. The source of geothermal energy is a. Radioactive decay of elements below the earth’s crust b. Heat still left from the time when the earth was formed c. Chemical reactions among gases trapped below the earth d. Underground nuclear explosions e. Both a and b 9. The temperature in the upper mantle and crust falls at the rate of a. 1°C/m b. 1°C/km c. 5-10°C/km d. 20-30°C/km e. More than 100 °C/km 10. Which layer of the earth’s interior is liquid? a. Crust b. Mantle c. Inner core d. Outer core e. None is liquid 11. Which layer of the earth’s interior has the greatest density? a. Crust b. Mantle c. Inner core d. Outer core e. All about equal 12. Which layer of the earth’s interior has the greatest volume? a. Crust b. Mantle c. Inner core d. Outer core e. About the same 13. Which layer of the earth’s interior has the least thickness? a. Crust b. Lower mantle c. Upper mantle d. Inner core e. Outer core 14. The major obstacle(s) associated with the use of geothermal energy is/are a. That many sites are difficult to access b. That they produce hydrogen sulfide which is an environmental pollutant c. That no technology exists for exploiting temperature gradients in hot solid rocks d. High initial cost e. All of the above 15. Most of the geothermal energy available today is from a. Volcanoes b. Hot water springs and geysers c. Hot dry rocks d. Desert surfaces e. All of the above 16. Binary-cycle power plants are most often used a. When the geothermal source is at a temperature below 100°C b. When the geothermal source is at a moderate temperature, between 100-200°C c. Only when steam is available at temperatures above 300°C d. Only when they are in association with hybrid design plants e. Only when underground sources contain large fractions of alcohol and other refrigerants 17. Depending on their size, geothermal plants can be a. Used for base load electricity production b. Designed to follow daily load demands c. Used for mini-grid and rural electrification d. Used for direct thermal use e. Used for all of the above 18. The largest geothermal power plant in the United States is located near a. San Francisco b. The Rocky Mountains c. Hawaii d. Los Angeles e. New York 218 19. Geothermal heat pumps can be used for a. Space heating b. Space cooling c. Both space heating and cooling d. Processing steam e. All of the above 20. Geothermal energy a. Is essentially a zero emission source of energy b. Produces some pollution, but not as much as fossil fuels c. Produces some radioactive waste, but with a short half-life d. Produces more pollution than fossil fuels, but with no radioactive waste e. None of the above III. True or False? 1. Boron, mercury, and arsenic are all types of pollution that come from geothermal plants. 2. Earth receives most of its life-supporting energy from geothermal sources. 3. Temperatures within the earth’s inner core could reach millions of degrees. 4. The outer core is composed of liquid molten metals, mostly iron and nickel. 5. Most geothermal resources lie only a few meters below the earth’s surface. 6. Binary geothermal plants usually use geothermal water at high pressures and moderate temperatures. 7. HDR is an innovative technology that can possibly meet many of the energy needs of the 21st century. 8. Geysers are considered renewable only if they are used at a sustained rate. 9. Binary plants are advantageous over non-binary plants, because they can be designed virtually pollution-free. 10. It is best to decide on the use of geothermal plants before a building is constructed. IV. Fill-in the Blanks 1. Geothermal resources can be categorized as hydrothermal, ___________, ___________, and ____________. 2. The largest concentration of hydrothermal activities lie in ____________________. 3. __________ are vents in the earth’s surface that release only steam. 4. The fluid often used in geothermal heat pumps is a mixture of water and __________solution. 5. Geothermal plants produce trace amounts of _____________, a gas that smells like rotten egg. 6. _________ installation of heat pumps is most cost-effective for residential sites and new construction where sufficient land is available. 7. Geothermal plants produce little carbon dioxide and practically none of the _______________ commonly produced in power plants using fossil fuels. 8. Upwelling of ground water with temperatures above surrounding atmospheric temperature but lower than body temperature is called ___________. 9. The water spewing out of hot springs have temperatures _______ that of human body. 10. The performance of a geothermal heat pump is measured by its ________________.