Geothermal Energy Production Problems and Possibilities Jessica Lindberg

Geothermal Energy Production, Problems, and Possibilities Jessica Lindberg Kozarek April 23, 2001

Geothermal Energy A “Renewable” Resource.

Sources of Geothermal Electricity

Availability of Geothermal Energy

Geothermal Power Plant Dry Steam Units 5 and 6 at The Geysers, California

Three Types Geothermal Power Plants in Use. n Dry Steam Power Plant n Flash Steam Power Plant n Binary Cycle Power Plant

Dry Steam Power Plant n. Oldest, first built in Lardello, Italy in 1904. n. Uses steam reservoirs (High T) n. Emits only steam and trace gases.

Flash Steam Power Plant n. Originated Zealand. n. T in New > 400 o. F. n. Uses High Temperature and Pressure Water Reservoirs. n. Emits only steam and trace gases.

Binary Cycle Power Plant n. T < 400 o. F n. Closed Loop n. Almost no emissions.

Production n Cost is upfront n $2000 per installed k. Wh n n Well Drilling and Pipeline Construction Resource analysis of drilling information Power plant design Operating Costs n $0. 015 -$0. 045 per k. Wh n Availability of 90%+ of the time increases cost.

Problems n n n Fluid rock chemistry and reservoir characteristics difficult to simulate. Acid content in water. Dissolved salts and gases modify properties of steam. In water-dominated systems, steam must be separated to produce electricity. Cold injection water can produce major problems if it reaches production well.

Problems, cont. n n n Increased seismic activity with exploitation of geothermal reservoirs. Cheap oil and natural gas prices. Resource depletion. Damage and changes to natural tourist attractions. High cost of drilling.

Geothermal vs. Fossil Fuels n Less Emissions n Less Area n More Availability (time) n Less Transportation n Less Availability (geographic)

Geothermal Emissions Geothermal Plants Emit: n 70% less SOx n 33% less NOx n 20% of greenhouse gases This prevents the emission of: ü 22 million tons CO 2 per year ü 200, 000 tons SO 2 per year ü 110, 000 tons PM per year

Area Advanced directional or slant drilling minimizes impact on land. n Several wells can be drilled from one pad. n Typically 400 m 2 per gigawatt over 30 yrs. n 1 -8 acres/MW for geothermal vs. 5 -10 acres/MW for nuclear and 19 acres/MW for coal. n

Availability Ø Geothermal plants ~ 95%+ Ø Coal plants ~ 60 -70+% This results in a higher cost but enables the plant to charge more during peak times.

Possibilities n n n Recovery and Recycling of byproducts. Biological Treatment for disposal of Geothermal Sludge. Wastewater recycling. Chemical Tracers for reservoir understanding. Use of hot dry rock for electricity generation. Use of deeper wells and magma for electricity generation.

Recovery and Recycling n H 2 S is separated and used for sulfuric acid production. n Metals such as zinc are recovered and sold for profit. n Silica from microbial processes can be recycled as concrete filler.

Biological Treatment of Geothermal Sludge n Biological treatment can be used for: n n n Solubilization and removal of of many metals including radionuclides. Selective removal of a few metals. Concentration of metals. Recovery of Salts. Water can be used for reinjection/irrigation.

Wastewater Recycling Santa Rosa California

Chemical Tracers n Provide an insight into the pathways that reinjected fluid will take in the geothermal reservoir. n Must be stable enough to endure weeks to years of geothermal testing. n Are usually non-toxic, and nonradioactive to avoid groundwater contamination.

Hot Dry Rock and Magma n These resources are being examined in other countries. n Hot Dry Rock has actually been used to produce electricity, but the technology is limited. n Drilling techniques are not yet advanced enough to utilize magma energy.

Future for Geothermal Energy ØClean power for developing countries. ØMore geothermal power production in the western U. S. through programs such as “Geopowering the West”. ØEven cleaner production through better technology and understanding of geothermal reservoirs, recycling, and reinjection.