Low-CO2 Energy

http://www.sciencecartoonsplus.com

Geothermal Energy in Perspective

6% of 8%

Most People’s Idea of Geothermal Energy

Lone Star Geyser,Yellowstone

Mammoth Terraces,Yellowstone

Why is Earth interior hot?• Heat from

rocks & atmosphere slow heat loss

≈ 4.6 b.y. ago

• gravitational collapse• radioactive decay

Geothermal Gradient

Plate Tectonics & Geothermal power plants worldwide

• Circulate hot water or stream thru buildings

• Generate electricity– Hot water or steam to turn turbines – convert secondary fluid to vapor to turn

turbines

Heat is an energy transfer from hot (higher T) objects to cold (lower T) objects

The Geysers, CA - largest single source of geothermal power

Dry Steam Power Plant• fluids are primarily steam• oldest type of geothermal power plant• gases can include H2S• very noisy

• The Nesjavellir Geothermal Power Plant in Iceland

wikipedia.org/wiki/Geothermal_power

Air emissions• radon gas • H2S• CO2• methane• ammonia

Thermal pollution (low thermal efficiency (20%); low steam temperatures

Noise

Potential pollution Problems – depends on type of geothermal

http://www1.eere.energy.gov/geothermal/gpp_animation.html

Hot, Dry Rock Animation

Animations of Geothermal Electric Power Plants

http://www.youtube.com/watch?v=kjpp2MQffnw&feature=related

http://www.youtube.com/watch?v=vSZ1dIBdOIs&feature=related

Noisy Steam Release

Wells and Power Plant – longer animation

http://uk.youtube.com/watch?v=ehRgYs9qOvk

Wells and Power Plant

thefraserdomain.typepad.com/

Few areas with hot rocks near the surface

Geothermal Heat Pumps• Earth T nearly constant 50-60 oF near surface

www.daviddarling.info

www.igshpa.okstate.edu

http://swgeothermal.com/Images/GeoAnimation.gif

Summer, cooling almost free

Winter, heating cheaper than standard heat

pump

20o

20o

50o

20o

homeimprovement.resourcesforattorneys.com

System costs are returned in energy savings in 5–10 years. System life is estimated at 25 years for the inside components and 50+ years for the ground loop. There are approximately 50,000 geothermal heat pumps installed in the United States each year.

The initial cost of installing a geothermal heat pump system can be 2-3 times that of a conventional heating system in most residential applications.

Horizontal ground loops

Thermal energy from lakes, abandoned mines

http://www.oscette.com/Tunnel.jpg

• Ocean thermal energy conversion (OTEC) – exploits T difference between warm

surface water and deep cold water

Ocean thermal energy conversion

alternateformsofenergy.com/Geothermal

A geothermal heat pump (also called GeoExchange, earth-coupled, ground source or water-source heat pump [1]) system is a heating and/or cooling system that uses the earth´s ability to store heat in the shallow ground or water thermal masses.Geothermal heat pumps are known also as "GeoExchange" systems, or "ground source heat pumps", to clearly distinguish them from air source heat pumps. It is important to understand that ground source heat pumps draw energy from shallow ground. The energy originates from the sun: none of the energy originates from the centre of the Earth, in spite of the name "geothermal heat pump". Genuine geothermal energy from the centre of Earth is available only in places where volcanic activity comes close to the surface.These systems operate based on the stability of underground temperatures: the shallow ground, this is the upper 10 feet (3.0 m) of Earth´s surface, has a very stable temperature throughout the year - between 10 and 16 °C (50 and 61 °F), depending upon location's annual climate [2]. Like a cave, the shallow ground temperature is warmer than the air above during the winter and cooler than the air in the summer [3]. A geothermal heat pump uses that available heat in the winter (heating) and puts heat back into the ground in the summer (cooling).The system cost are returned in energy savings in 5–10 years. System life is estimated at 25 years for the inside components and 50+ years for the ground loop. There are approximately 50,000 geothermal heat pumps installed in the United States each year [4].

The heat pump itself, explained more fully in the article on heat pumps, consists of a loop containing refrigerant. The refrigerant is pumped through a vapor-compression refrigeration cycle that moves heat from a cooler area to a warmer one.

The initial cost of installing a geothermal heat pump system can be two to three times that of a conventional heating system in most residential applications

Hydrogen (H2) as fuel

2H2 + O2 = 2H2O Why is this a nearly ideal fuel!Pure water is the only waste!

How do we make it?

H2 is explosive – engineering challenges

2H2O = 2H2 + O2

energy

What kinds don’t make CO2?

solarnuclearhydropower

Fig. 15.32a