Geothermal Energy - AP Environmental Science
- State the formula for geothermal gradient.
- Geothermal gradient = . Measures rate of temperature increase with depth, typically 25-30°C per km.
- What is the primary economic benefit of geothermal energy?
- Reduced dependence on fossil fuels. Domestic renewable energy reduces imports and price volatility.
- What is the role of heat exchangers in geothermal systems?
- To transfer heat between fluids. Enable efficient heat transfer in binary cycle and other geothermal systems.
- What is the primary source of geothermal energy?
- Radioactive decay of elements in the Earth's core. Uranium, thorium, and potassium decay continuously, generating heat in Earth's core.
- Identify an environmental benefit of geothermal energy.
- Minimal land footprint. Small surface area compared to other renewable energy installations.
- Identify a major advantage of geothermal energy.
- Low carbon emissions. Nearly zero greenhouse gas emissions compared to fossil fuel power plants.
- What is a binary cycle power plant?
- A plant using a secondary fluid with a lower boiling point than water. Secondary fluid vaporizes at lower temperatures, enabling power from moderate heat sources.
- What geological feature is often associated with geothermal sites?
- Volcanoes. Volcanic activity indicates subsurface magma and high geothermal potential.
- Identify a common use of geothermal energy.
- Electricity generation. Steam drives turbines to generate clean electricity from Earth's heat.
- What is the term for the process of water returning to its original state in geothermal systems?
- Reinjection. Cooled water returns underground to maintain reservoir sustainability.
- What is the main function of a condenser in a geothermal plant?
- To convert steam back into water. Cooling steam to liquid water completes the thermodynamic cycle.
- How is heat extracted in a geothermal heat pump system?
- By circulating a fluid through pipes underground. Ground temperature remains constant year-round, providing efficient heating/cooling.
- State the efficiency range of geothermal power plants.
- 10% to 20%. Lower than fossil fuel plants due to thermodynamic limitations of heat sources.
- What is the role of an injection well in geothermal systems?
- To reinject the cooled water back into the reservoir. Maintains reservoir pressure and sustainability by returning used water underground.
- What is the typical depth range for geothermal wells?
- 1 km to 4 km. Deep drilling required to reach high-temperature geothermal resources.
- Identify a component of a geothermal power plant.
- Turbine. Steam from geothermal wells spins turbine blades to generate electricity.
- Which element is commonly released in geothermal emissions?
- Sulfur. H₂S gas creates odor and corrosion issues in geothermal operations.
- What is the typical capital cost range for geothermal installations?
- $2,500 to $5,000 per kW. High upfront costs but low operating expenses over plant lifetime.
- What is geothermal energy?
- Heat derived from the Earth's interior. Thermal energy stored beneath Earth's surface from core formation and radioactive decay.
- Which country is the largest producer of geothermal energy?
- United States. Leads global geothermal capacity with over 3,700 MW installed.
- What is a geothermal field?
- An area with a high concentration of geothermal activity. Multiple wells and power plants concentrate in zones of high heat flow.
- Identify a renewable aspect of geothermal energy.
- Sustainable heat supply. Earth's internal heat regenerates continuously over geological time scales.
- Which type of geothermal power plant uses both steam and hot water?
- Flash steam power plant. High-pressure hot water flashes to steam when pressure drops in separator.
- What is a disadvantage of geothermal energy?
- Limited to regions with suitable geothermal activity. High-quality geothermal resources exist only in specific geological zones.
- What is a geothermal power plant?
- A facility that converts geothermal energy into electricity. Uses steam or hot water from underground to drive turbines for electricity.
- Identify a key factor in the feasibility of geothermal energy.
- Geological conditions. Rock permeability, temperature, and water availability determine project viability.
- What is the typical temperature range of geothermal reservoirs?
- 20°C to 370°C. Range varies from low-temperature direct use to high-temperature power generation.
- What is a geothermal aquifer?
- A water-bearing geological formation used in geothermal systems. Underground rock layer containing heated groundwater for energy extraction.
- What is the purpose of a production well?
- To extract steam or hot water from the geothermal reservoir. Brings hot fluids to surface for power generation or direct use.
- What is Enhanced Geothermal System (EGS)?
- A technology to extract heat from dry, impermeable rocks. Water injection creates fractures in hot dry rock to enable heat extraction.
- What is an example of a geothermal resource?
- Geysers. Hot springs that periodically erupt steam and water from underground pressure.
- Identify one benefit of geothermal heating in residential areas.
- Reduces heating costs. Stable ground temperatures provide consistent, efficient home heating.
- Identify a risk of geothermal energy production.
- Induced seismicity. Fluid injection can trigger small earthquakes in fault zones.
- How does geothermal energy contribute to grid stability?
- Provides baseload power. Operates continuously unlike intermittent solar and wind power sources.
- Identify a method to mitigate seismic activity from geothermal drilling.
- Careful site selection and monitoring. Proper location assessment and gradual drilling reduce earthquake risks.
- What is the primary environmental concern of geothermal energy?
- Release of hydrogen sulfide gas. H₂S creates rotten egg odor and can be toxic at high concentrations.
- What is a common method of geothermal exploration?
- Seismic surveys. Detect underground heat sources through seismic wave analysis.
- Describe a direct use application of geothermal energy.
- District heating. Hot water directly heats buildings and communities without electricity conversion.
- Which type of rock is typically associated with geothermal energy?
- Igneous rock. Formed from cooled magma, often containing high subsurface temperatures.