Session 5Session 5Geothermal Power PlantGeothermal Power Plant

What is Geothermal Energy? What is Geothermal Energy?

Geo (Geo (Greek) – Greek) – earthearth

Thermal - relating to, using, producing, or caused by heat.

The EarthThe Earth

•Parts of the earth

•Flow of magma

•Below surface temperatures

•Gradient from hot to cold

•Heat can be ejected as steam or hot water.

•Hydrothermal reservoirs, water

and hot porous rock.

•Yellowstone National Park

Triangles and circles refer to locations that are potent locations for geothermal energy extraction. Triangles are the locations that are already being exploited and circles are locations unexploited (Barbier, 2002)

Expansion of Available Resources

What can we do with heat?What can we do with heat?

Conventional geothermal plants capture Conventional geothermal plants capture hot water from geysers or steam from hot water from geysers or steam from

vents to spin turbines.vents to spin turbines.

Surface Geothermal SystemsSurface Geothermal Systems

There are three different types of There are three different types of surface geothermal system designs:surface geothermal system designs:

1. Flash-steam Power Plant1. Flash-steam Power Plant

2. Dry-steam Power Plant2. Dry-steam Power Plant

3. Binary-cycle Power Plant3. Binary-cycle Power Plant

Flash-steam Geothermal Power Plant

Flash-steam Geothermal Power Flash-steam Geothermal Power

PlantPlant

Hot, High pressure water Hot, High pressure water Turbines generate electricityTurbines generate electricity

Costs 4-6 cents per Kwh.Costs 4-6 cents per Kwh.

Dry-steam Geothermal Power Plant

Dry-steam Geothermal Power PlantDry-steam Geothermal Power Plant

Steam passes through turbineSteam passes through turbine 1050 -1220 degrees F1050 -1220 degrees F

Binary-cycle Geothermal Power PlantBinary-cycle Geothermal Power Plant

Hot water (100 – 300 deg F) Hot water (100 – 300 deg F) Heat Exchanger Heat Exchanger Binary liquid lower specific Binary liquid lower specific

heat (vaporizes)heat (vaporizes)

Limitations of Surface Limitations of Surface Geothermal Power PlantGeothermal Power Plant

Dependent on location. Dependent on location. Most viable sites have been tapped.Most viable sites have been tapped. Not as efficient as coal fired power plant.Not as efficient as coal fired power plant.

Enhanced Geothermal SystemsEnhanced Geothermal Systems

•Temperature profile

•Think about the energy stored in the earth.

•How would one take advantage of this?

Enhanced Geothermal SystemsEnhanced Geothermal Systems

The Enhanced geothermal system designs The Enhanced geothermal system designs for actual electricity generation are for actual electricity generation are similar to surface geothermal system. similar to surface geothermal system.

Flash or Steam PlantsFlash or Steam Plants

Dry Steam Power PlantsDry Steam Power Plants

Binary cycle power plantBinary cycle power plant

Type of plant depends on conditions.Type of plant depends on conditions.

Components and ProcessComponents and Process

Energy FlowEnergy Flow

E = D x Dt x PE = D x Dt x P

E = energy flow (kcal/s)E = energy flow (kcal/s)

D = rate of hot water flow (kg/s)D = rate of hot water flow (kg/s)

Dt = difference between hot water Dt = difference between hot water temperature temperature and condensate temperature (and condensate temperature (00C)C)

P = specific heat (kcal/kg)P = specific heat (kcal/kg)

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EfficiencyEfficiency

• Efficiency functions like conventional coal power plant.

• Efficiency varies by input heat.