heat from earth
What is it ……. ?
CAUSE OF SOURCES
- Earth's core maintains temperatures in excess of 5000°C
- Heat gradual radioactive decay of elements
- Heat energy continuously flows from hot core
- Convective flows of molten mantle beneath the crust .
- Mean heat flux at earth's surface
- 16 kilowatts of heat energy per square kilometer
- Dissipates to the atmosphere and space.
- Tends to be strongest along tectonic plate boundaries
- Volcanic activity transports hot material to near the surface
- Only a small fraction of molten rock actually reaches surface.
- Most is left at depths of 5-20 km beneath the surface,
- Hydrological convection forms high temperature geothermal systems at shallow depths of 500-3000m.
Dry Steam Schematic
Dry Steam Power Plants
- “ Dry” steam extracted from natural reservoir
- Steam is used to drive a turbo-generator
- Steam is condensed and pumped back into the ground
- Can achieve 1 kWh per 6.5 kg of steam
- A 55 MW plant requires 100 kg/s of steam
THE GEYSERS-CA-LARGEST DRY STEAM
Direct Use Technologies
- Geothermal heat is used directly rather than for power generation
- Extract heat from low temperature geothermal resources < 150 o C
- Applications sited near source (<10 km)
Borehole Heat Exchange This type uses one or two underground vertical loops that extend 150 meters below the surface.
DISTRICT HEATING SYSTEM
Single Flash Steam
Single Flash Steam Power Plants
- Steam with water extracted from ground
- Pressure of mixture drops at surface and more water “flashes” to steam
- Steam separated from water
- Turbine drives an electric generator
- Generate between 5 and 100 MW
- Use 6 to 9 tonnes of steam per hour
Double Flash Schematic
Double Flash Power Plants
- Similar to single flash operation
- Unflashed liquid flows to low-pressure tank – flashes to steam
- Steam drives a second-stage turbine
- Also uses exhaust from first turbine
- Increases output 20-25% for 5% increase in plant costs
Binary Cycle Schematic
Binary Cycle Power Plants
- Low temps – 100 o and 150 o C
- Use heat to vaporize organic liquid
- E.g., iso-butane, iso-pentane
- Use vapor to drive turbine
- Typically 7 to 12 % efficient
Binary Plant Power Output
Combined Cycle Plants
- Combination of conventional steam turbine technology and binary cycle technology
- Steam drives primary turbine
- Remaining heat used to create organic vapor
- Organic vapor drives a second turbine
- Plant sizes ranging between 10 to 100+ MW
- Significantly greater efficiencies
- Higher overall utilization
- Extract more power (heat) from geothermal resource
Hot Dry Rock Technology
- Wells drilled 3-6 km into crust
- Hot crystalline rock formations
- Water pumped into formations
- Water flows through natural fissures picking up heat
- Hot water/steam returns to surface
- Steam used to generate power
Hot Dry Rock Technology Fenton Hill plant
CASE STUDY-------SABALAN , NW IRAN
KEY- R & D -WORK
- Prioritization of sites for future EGS development and estimating the size of the economic EGS resource.
- Low-risk, economical EGS site selection and characterization capabilities.
- Drilling, casing, and preparing the wells for simulation and production.
ENHANCED GEOTHERMAL SYSTEMS
Tectonic Plate Movements
World Wide Geothermal Uses and Potential
RING OF FIRE
Availability of Geothermal Energy
- On average, the Earth emits 16kW/km 2 . However, this number can be much higher in areas such as regions near volcanoes, hot springs and fumaroles.
- As a rough rule, 1 km 3 of hot rock cooled by 100 0 C will yield 30 MW of electricity over thirty years.
- There is believed to be enough heat radiating from the center of the Earth to fulfill human energy demands for the remainder of the biosphere’s lifetime.
Geothermal Site Schematic
Performance vs. Rock Type