BY: ANA BRAR

Residential Geothermal Energy Use

What Is Geothermal Energy?

• Heat from the earth• Can be found almost anywhere• Affordable and sustainable• Hot, molten magma found under the Earth’s

crust• Heat is continuously produced – decaying

radioactive materials (U and K)• 50,000 times more energy than all the oil and

natural gas in the world within 10,000 m of the surface

More About Geothermal Energy

Areas with highest underground temperatures = active/geologically young volcanoes

Also when crust is thin and at plate boundaries

Ring of fire – Oregon, N. Nevada, California

How Geothermal Energy is GeneratedTechnique #1

• Tap into hydrothermal convections systems in which heated water rises to the surface

• Three designs• Pulls water/steam,

uses it, returns as warm water

• 1: Steam goes directly through turbine then into a condenser where the steam is condensed into water

Technique # 2

Very hot water is depressurized or “flashed” into steam

Used to drive turbine to generate electricity

Technique # 3

• Binary system• Hot water passes

through a heat exchanger

• Heats a second liquid (i.e. isobutane) in a closed loop

• Isobutane boils at a lower temperature than water

• More easily converted to steam to run the turbine

Deciding a Technique

• Technique determined by the resource

• If water comes out as steam, the first technique is easiest

• More hot water resources than pure steam or high-temperature water sources

• Most growth potential in heat exchanger system

Current Use

• Largest geothermal system

• The Geysers, CA - North of San Francisco

• 26 power plants – 2,200 megawatts

• Meets nearly 70% of the average electrical demand for California's North Coast region

Current Use in the U.S.

U.S. produces enough electricity for 2.4 million households

Not including contributions from geothermal heat pumps and direct heating uses

U.S. has about 3,000 MW of geothermal electricity connected to the grid

Represents 0.3 % of the world total electrical energy

2007 - Accounted for 4% of renewable energy-based electricity consumption in the U.S.

https://publicaffairs.llnl.gov/news/energy/content/energy/energy_archive/energy_flow_2006/LLNL_US_Energy_2006.png

The U.S. continues to produce more geothermal electricity than any other country, comprising approximately 30 percent of the world total

Residential uses

• Geothermal energy can be used for both heating and cooling purposes

• Klamath Falls, OR and Boise, ID – geothermal water has been used to heat homes and buildings for over a century

• Reno, NV – new houses• Iceland – more than 50%

of energy from geothermal sources

Geothermal Energy Use in Homes

• Called ground-source pumps

• Constant year round temperature of 50°F that is just 5 to 10 feet underground

• Air or antifreeze liquid is pumped through pipes underground

• Summer – pipes move heat from the building and bring in cooler air

• Winter – provide pre-warmed air and water

http://earthcomfort.com/howitworks

Installation

• 4 main ways geothermal system can be installed

• Horizontal Straight Loop – most common, economical, 5 feet underground

• Horizontal Coiled Loop - pipe is spread out in flattened, overlapping coils

Installation - continued

• Vertical loops – buried deep in the ground, ideal for buildings that lack large areas of yard needed for the horizontal loops, more costly

• Pond loops – use existing bodies of water on the property to extract energy

Environmental Benefits

• Burns no fossil fuels• Renewable and

sustainable form of energy

• Study by the Environmental Protection Agency found that it’s 72% more efficient than electric heating and AC

• Uses no flame and doesn’t release toxic fumes into the house

Financial Benefits

• U.S. Dept. of Energy says that heat pumps can save a typical home hundreds of dollars in energy costs each year, with the system paying for itself in 2 to 10 years

• Cost-competitive: 2–10 US cents/kWh

• State and federal incentives under the American Recovery and Reinvestment Act of 2009 - one-time tax credit of 30 percent of the total investment

Geothermal Vs. Other Energy Forms

Geothermal Vs. Fossil Fuels

More eco-friendlyGeothermal: electricity

is produced with an efficiency of 10–17% vs. 36-40% (fossil fuels)

Renewable: As long as we don't pump too much cold water down and cool the rocks too much

Geothermal Vs. Solar

Solar gives energy intermittently – only during the day and without clouds

Unpredictable

Drilling for water

Challenge of limiting heat loss as the water is pumped back up the hole

Water is hotter the deeper down the well is drilled

Disadvantages

Certain techniques (such as the one used in The Geysers, CA) loses 60-80% of the steam to the air, not reinserting it back underground

Hydrogen sulfide, arsenic, and minerals are released in the steam

Geothermal energy site may run out of steam for decades

Conclusion

Future usesHolds promise for the futureCan supply continuous base power much like

fossil fuels but without the harmful emissionsCost for electricity from geothermal is

decreasing

Works Cited

Geothermal Energy Association: http://www.geo-energy.org/aboutGE/currentUse.asp

Earth Comfort – Heating and Cooling: http://earthcomfort.com/howitworks

Geothermal energy technology and current status: An overview: www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VMY

Union of Concerned Scientists: http://www.ucsusa.org/clean_energy/technology_and_impacts/energy_technologies/how-geothermal-energy-works.html