Lecture 26 Chapter 18 Tapping the Earth’s Heat: Geothermal Energy

http://geothermal.marin.org/GEOpresentation/ http://geothermal.marin.org/geopresentation/sld030.htm

History of Geothermal Use Geothermal steam and hot springs have been used for centuries for bathing and heating Prince Piero Ginori Conti tested the first geothermal power plant on 4 July 1904, at the Larderello dry steam field in Italy. The first Geothermal power plant in the United States was made in 1922 by John D. Grant at The Geysers Resort Hotel. After drilling for more steam, he was able to generate enough electricity to light the entire resort. Eventually the power plant fell into disuse, as it was not competitive with other methods of energy production.[16] In 1960, Pacific Gas and Electric began operation of the first successful geothermal power plant in the United States at The Geysers. It lasted for more than 30 years and produced 11 MW net power.[16] Geothermal power is generated in over 20 countries around the world Heat transferred to the surface of the earth is 1/20,000 that of heat from the sun reaching the earth.

3 basic types of geothermal power plants: Dry steam plants - use steam piped directly from a geothermal reservoir to turn the generator turbines. Flash steam plants - take high-pressure hot water from deep inside the earth and convert it to steam to drive the generator turbines. When the steam cools, it condenses to water and is injected back into the ground to be used over and over again. Most geothermal power plants are flash plants. Binary power plants - transfer the heat from geothermal hot water to another liquid. The heat causes the second liquid to turn to steam which is used to drive a generator turbine.

http://fossilfreedom.com/geothermal.html

Copyright 1997, American Society Of Heating, Air-conditioning and Refrigeration Engineers Inc., www.ashrae.org. Reprinted by permission from Ground-Source Heat Pump Systems: Design of Geothermal Systems for Commercial and Institutional Buildings

Types of Heating/Cooling Geothermal Units Source

http://en.wikipedia.org/wiki/Ground-source_heat_pump

Interactive Map http://geoheat.oit.edu/dusys.htm

Figure 18. 2: Regions of potential geothermal sites, the “ring of fire Figure 18.2: Regions of potential geothermal sites, the “ring of fire.” These regions correspond roughly to the zones of earthquakes and volcanic activity. Fig. 18-2, p. 580

Figure 18. 3: Tectonic plate boundaries Figure 18.3: Tectonic plate boundaries. The earth’s crust is made up of six major plates and a number of smaller ones. These plates are in a state of constant relative motion (at rates of several centimeters per year). Near the junctions of the plates, heat travels most rapidly from the interior. Fig. 18-3, p. 580

Figure 18. 5: Model of a geyser Figure 18.5: Model of a geyser. Water at the bottom of the container is under great pressure and will not boil until temperatures above 100°C are reached. When boiling begins, the pressure is released, causing the water to boil very rapidly. The steam-driven water rushes up the neck and is sprayed into the air in the form of steam. Fig. 18-5, p. 582 Fig. 18-4, p. 581

Geysers Geothermal Plant – N. CA. Figure 18.6: The Geysers Geothermal Power Plant in northern California. Most of the steam seen here comes from the condensers of the individual units. Geysers Geothermal Plant – N. CA. Fig. 18-6, p. 583

Pipes carrying steam to a generator.

Figure 18. 7: Vapor-turbine cycle Figure 18.7: Vapor-turbine cycle. Water is circulated through a hot dry rock system. The heated water is pumped through a heat exchanger, boiling the working fluid, which is isobutane. The cooled water is reinjected into the ground. The vapor expands through a turbine and then is condensed back to a liquid in the water-cooled condenser. Fig. 18-7, p. 585

Table 18-1, p. 578

Source

Solar (thermal electricity) 12 - 18 3000 - 4000 Tidal 8 – 15 Energy and investment costs for electric energy production from renewables (from Fridleifsson, 2001) Current energy cost US¢/kWh Potential future energy cost Turnkey investment cost US$/kW Biomass 5 - 15 4 - 10 900 - 3000 Geothermal 2 - 10 1 - 8 800 - 3000 Wind 5 - 13 3 - 10 1100 - 1700 Solar (photovoltaic) 25 - 125 5 - 25 5000 - 10 000 Solar (thermal electricity) 12 - 18 3000 - 4000 Tidal 8 – 15 1700 - 2500 Energy and investment costs for direct heat from renewables (from Fridleifsson, 2001) Current energy cost US¢/kWh Potential future energy cost Turnkey investment cost US$/kW Biomass (including ethanol) 1 - 5 250 - 750 Geothermal 0.5 - 5 200 - 2000 Wind 5 - 13 3 - 10 1100 - 1700 Solar heat low temperature 3 - 20 2 - 10 500 - 1700

Table 18-2, p. 586

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