Chuck Kutscher National Renewable Energy Laboratory Geothermal Power Potential Energy and Climate Mini-Workshop November 3, 2008

Source: EIA Annual Energy Review 2007 Geothermal in the Energy Portfolio Net Generation – 2006

U.S. Renewable Energy Electric Capacity Sources: Chalk, AWEA, IEA, NREL, EIA, GEA

Geothermal Resources Hot granite Geopressured Enhanced Geothermal System Hot water Wells Magma Volcanic Hydrothermal

Carbon Benefits

Advantages of Geothermal Energy Environmentally sound Resources last the life of the plant High plant availability (over 95%) Provides steady base load power Relatively low cost (5 to 8 cents per kWh)

Todays Status 8,000 MW generated in 21 countries In U.S. 3,000 MWe installed, 4,000 MWe under development DOE funding 21 companies $43 million over 4 years for EGS projects Cost 5-8¢/kWh with no PTC Capacity factor typically > 90%, base load power

G E O T H E R M A L Hydrothermal Resource

Geothermal Power Plants

Plant Type vs. Temperature 0 o C 32 o F) 90 o C (195 o F) 175 o C (350 o F) Flash steam Binary cycle

Plant Costs

Favorable Geothermal Areas and Known Systems

Geographic Distribution of Hydrothermal Resources Identified Geothermal Resources Undiscovered Resources USGS, 2008

U.S. Hydrothermal Electric Power Potential Williams, et al., USGS Fact Sheet, Assessment of Moderate- and High-Temperature Geothermal Resources of the United States, September 2008

Heat Fluid ContentPermeability Geothermal Domains Enhanced Geothermal System Hot Dry Rock (HDR) – Fracturing and water injection required Note: System must have fluid content, permeability, and heat to be potentially viable. This combination can be natural (Hydrothermal) or created in an enhanced geothermal system. Water Injection Required Fracturing Required Hydrothermal

Geographic Distribution of EGS USGS, 2008

EGS Resource Temperatures at 6 km Depth

EGS Steps Source: NREL

The U.S. Enhanced Geothermal System Resource Source: MIT Study- The Future of Geothermal Energy

MIT EGS Supply Curve: 10% of U.S. Capacity by Mid-Century MIT EGS model predictions with todays drilling and plant costs and mature reservoir technology at 80 kg/s per production well 2004 US $

EGS Challenges Technical Site selection - regional exploration techniques for EGS Creating EGS under various geologic environments –achieving low flow impedance –achieving sufficiently large sustainable reservoir without short circuiting (80 kg/s at 200°C) –minimizing water loss –microseismicity Few EGS field experiments yet conducted worldwide; only 25 kg/s achieved at Soultz Geologic variability and uncertainty make the technical challenges of EGS very different from other renewable energy sources.

Economic Exploration cost and risk Drilling, completion and reservoir stimulation costs Capital cost of surface facilities No commercial EGS site for benchmarking Commercialization Validating EGS technology requires high risk field experiments in a variety of geologic settings Limited Federal R&D funding EGS Challenges

U.S. EGS Electric Power Potential Williams, et al., USGS Fact Sheet, Assessment of Moderate- and High-Temperature Geothermal Resources of the United States, September 2008

ASES Study Supply Curve current technology basis with projected DOE gains Bases for market penetration studies using NEMS. Hydrothermal 27 GW Sedimentary EGS 25 GW Co-produced fluids 44 GW Basement EGS 4 GW

Geothermal Power Savings Carbon Savings: 83 MtC/yr 50,000 MW by % existing resources, 25% expanded, 50% from oil & gas wells 5 to 10 ¢/kWh