Session 5 Geothermal Power Plant

What is Geothermal Energy? Geo (Greek) – earth Thermal - relating to, using, producing, or caused by heat.

The 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? Conventional geothermal plants capture hot water from geysers or steam from vents to spin turbines.

Surface Geothermal Systems There are three different types of surface geothermal system designs: 1. Flash-steam Power Plant 2. Dry-steam Power Plant 3. Binary-cycle Power Plant

Flash-steam Geothermal Power Plant

Hot, High pressure water Hot, High pressure water Turbines generate electricity Turbines generate electricity Costs 4-6 cents per Kwh. Costs 4-6 cents per Kwh.

Dry-steam Geothermal Power Plant

Steam passes through turbine Steam passes through turbine degrees F degrees F

Binary-cycle Geothermal Power Plant Hot water (100 – 300 deg F) Hot water (100 – 300 deg F) Heat Exchanger Heat Exchanger Binary liquid lower specific heat (vaporizes) Binary liquid lower specific heat (vaporizes)

Limitations of Surface Geothermal 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 Systems Temperature profile Think about the energy stored in the earth. How would one take advantage of this?

Enhanced Geothermal Systems The Enhanced geothermal system designs for actual electricity generation are similar to surface geothermal system. Flash or Steam Plants Dry Steam Power Plants Binary cycle power plant Type of plant depends on conditions.

Components and Process

Energy Flow E = D x Dt x P E = energy flow (kcal/s) D = rate of hot water flow (kg/s) Dt = difference between hot water temperature and condensate temperature ( 0 C) P = specific heat (kcal/kg)

22Efficiency Efficiency functions like conventional coal power plant. Efficiency varies by input heat.