Geothermal-Energy-lec

Introduction to Geothermal Energy

  • Definition: Geothermal energy is the heat produced continuously within the Earth from its interior.

  • Terminology:

    • Geo - Earth

    • Thermal - Heat

  • Characteristics: It is a clean and sustainable energy source, where heat also replenishes through rainfall.

Historical Context

  • First Geothermal Power Plant: Established in 1904 at Larderello, Italy.

Sources of Earth's Internal Energy

  • Main Sources:

    • Radioactive Decay (70%): Long half-life radioactive nuclei contribute significantly to Earth's heat.

    • Residual Heat: Leftover heat from Earth's formation.

    • Meteorite Impacts: Contributes additionally to the Earth’s energy.

Internal Structure of the Earth

  • Layers:

    • Inner Core: Solid iron.

    • Outer Core: Composed of magma.

    • Mantle: A combination of magma and rock.

    • Crust: Insulative layer that prevents heat escape.

Temperature Distribution Inside Earth

  • Temperature by Depth (in °C):

    • 2000m: 400°C

    • 4000m: 600°C

  • Plate Dynamics:

    • Crust divided into tectonic plates.

    • Magma flows to the surface at plate boundaries, causing geological activities such as eruptions and earthquakes.

Geothermal Energy Locations

  • Geographic Concentration:

    • Ring of Fire: Major geothermal resource area around the Pacific Ocean; active regions also exist in Asia, Europe, North America, Africa, and Australia.

  • Distribution: Geothermal resources are predominantly found near volcanoes and seismic activity zones.

Plate Tectonic Processes

  • Landscape Processes:

    • New crust formation at ocean ridges.

    • Plate collisions that push magma upward, heating surrounding rocks without often reaching the surface.

Geothermal Reservoirs

  • Formation of Reservoirs:

    • Hot water and steam accumulate in permeable rocks capped by impermeable rock layers.

    • Rainwater seeps through faults, heating and potentially coming back as springs, geysers, and fumaroles.

Types of Geothermal Energy Sources

  • Hot Water Reservoirs: Large volumes of underground hot water suitable for heating.

  • Natural Steam Reservoirs: Rare in the U.S.; steam rises naturally from wells.

  • Geopressured Reservoirs: Brine saturated with natural gas under pressure for dual heat and gas extraction.

Geothermal Gradient

  • Normal Gradient: +30°C per km of depth.

  • Hot Dry Rock: Exists in some U.S. regions; higher gradient of 40°C/km.

  • Magma: Significant unharvested heat reserves; potential sites are primarily Alaska and Hawaii.

Exploration and Drilling Technologies

  • Techniques:

    • Satellite imagery and volcanological studies guide geothermal exploration.

    • Rocks analyzed for temperature gradients, indicating geothermal potential.

  • Typical Temperature Gradient: Data collection to determine depths and heating potential.

Direct Uses of Geothermal Energy

  • Applications Below 150°C:

    • Space heating

    • Air conditioning

    • Industrial processes

    • Greenhouses and aquaculture

    • Thermal resorts and pools.

Heat Pump Technologies

  • Geothermal Heat Pumps (GHP):

    • Horizontal and vertical loops for exchanging heat between the ground and living spaces.

    • Advantages: Energy efficient, low maintenance, significant energy savings.

Electricity Generation from Geothermal Energy

  • Types of Plants:

    • Dry Steam Plants: Direct use of steam to drive turbines.

    • Flash Steam Plants: High-pressure hot water turned into steam.

    • Binary Cycle Plants: Lower temperature water vaporizes a working fluid to generate steam.

Environmental Impact of Geothermal Energy

  • Positive Effects: Minimal land use, lower emissions compared to fossil fuels, potential for job creation and energy independence.

  • Negative Effects:

    • Soil salination from brine

    • Land subsidence

    • Seismic activity from extraction processes.

Global Geography of Geothermal Energy

  • Significant Countries:

    • Iceland: 87% of heating and 26% of electricity from geothermal energy.

    • Other countries include the USA, Philippines, Italy, and Indonesia.

    • Global Potential: Explored resources could meet energy demands for millennia.

Conclusion

  • Geothermal energy is a promising and eco-friendly resource with heating, cooling, and electricity-generation capacities. Its utilization can greatly reduce reliance on fossil fuels and support sustainable energy goals.