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GEOTHERMAL ENERGY: Is it a viable option in an oilinduced energy crisis? By Adrien T. Robinson
Overview of Policy to Off-set Loss In Oil Imports A Two-Stage Approach: Short Term (Several Years to a Decade) Expand Use of Known Geothermal Resources Using Currently Available Technologies Long-Term (Several Decades?) – Develop, Improve & Implement Technologies to Tap into Deep Geothermal Resources Supplement These Efforts By Providing Gov’t Subsidy, Clean Air Credits and Tightening Pollution Regulations
Overview of Policy Cont’d Short Term Highlights & Achievable Goals: Replace Current Oil Uses for Spacing Conditioning Provide Gov’t Subsidy to Minimize Capital Expenditure – Justifiable Given the Environmental Benefits Develop Last of Known Shallow Geothermal Sources Capable of Electricity Generation – Expansion of Electricity Generation up to 19 GW Overall, Offset Lost Energy 2-10% of Current Oil Imports
Overview of Policy Cont’d Long-Term Highlights & Achievable Goals: Develop, Improve & Implement Technologies to Tap into Deep Geothermal Resources – Magma and Near Core Fluids Capable of Replacing All Electricity Needs in U.S. and All Energy for Space Conditioning
Summary of Conclusion Short Term: Not a Viable Option to Replace 25% Loss in Oil Imports. Perhaps 2-10% Could Be Replaced in a Few Years to a Decade. Long Term (Likely Decades): Capable of Replacing All Electricity Needs, Including All HVAC Applications
What is Geothermal Energy? Geo (Greek for earth) Thermal (heat) Temp. of Shallow Crust (upper 10 ft.) Constant 55-75 F (13-24 C) Up to 14,400 F (8,000 C) at Molten Core (approx. 4,000 mi. to center of core)
What is Geothermal Energy Cont’d? Earth’s Crust Thickness: 3 to 35 Mi. Temperature Increases With Depth – Gradient: 50-87 F / Mile (17-30 C / km) Basic Geothermal Systems Take Advantage of: Heat Differential Between Ground and Indoor Air Temperatures – Heat Pump Earth as a Natural Heat Source – Power Plants
Types of Geothermal Resources? Geothermal Sources are Classified Based on: (1) Temperature, (2) Physical State of H20 (i.e. water or steam), and (3) Type of Energy Usage Primary Classification is Resource Temperature: Low Temperature Reservoir: 50-200 F (1094 C) High Temperature Reservoir: 200 F
Brief History of Geothermal Energy Paleo-Indians Usage Dates Back 10,000 Years Use by Romans – Hot Spas; Hot Running Water, Etc. Early 1800s – Yellowstone Hot Springs and Hot Springs Arkansas 1830 1st Commercial Use; Asa Thompson sold Bath in Wooden Tub for 1
History of Geothermal Energy Cont’d In 1852, the Geysers Resort Hotel in San Fran. CA opened 108 Years later, 1st Geothermal Electricity Plant Opened at the Same Location – “The Gysers”
Basic Types of Geothermal Reservoirs 3 General Classes of Geothermal Uses Ground Source Heat Pump Direct Source Commercial Electricity Generation: Power Plants – Need High Capacity Geothermal Reservoir; Generally Water / Steam 200 F
Types of Reservoirs Cont’d Low Temperature Reservoirs: Available almost anywhere on earth Predominantly Used for Heat Pumps – Space Heating Other Common Uses: – Hot Water Production – Piped Under Roads / Sidewalks (Klamath Falls, Oregon) – In Greenhouses to Grow Flowers, etc. – Industrial Uses: dry wood, pasteurize milk, grow fish, etc.
Types of Reservoirs Cont’d High Temperature Reservoirs: Availability: – Can Occur Within a Couple of Miles of Earth’s Surface Where Earth’s Crust Is Very Thin – i.e., Closer to Molten Magma at Core Suitable for Commercial Production of Electricity – Power Plants Need High Capacity Geothermal Reservoir – Water / Steam 220 F (105 C) Greatest Potential for Energy Output
What Makes a Good Geothermal Reservoir for Generating Electricity? Hot Geothermal Fluids Near Surface ( 1-2 mi.) Preferably in Excess of 300 F, but Electrical Generation Is Occurring at Temps. In the Low 200’s F. Proximity to Population Base Low Mineral and Gas Content Location on Private Land Proximity to Transmission Lines
Needed Technology: Are We Talking Simple, Existing Technology or Star Wars? Answer: Both. Technology for HVAC in All Bldgs. in U.S. and for Electrical Generation From Shallow (1-2 Mi. Deep) Geothermal Reservoirs Already Exists and Is Proven – Drawback: Number of Electricity Sources Is Limited Technology for Tapping Deep ( 3-6 Miles), Hot Dry Sources and Magma Is Not Yet Available – Positive: Unlimited, Renewal Resource
The Geothermal Heat Pump Most Basic Form of Geothermal Usage What – takes advantage of stored heat of near surface soil / water (Const. temp of 55-75 F) Winter Months – uses ground as a “heat source” – Transfers heat from warm subsurface to facility Summer Months – uses ground as a “heat sink” – Transfers heat from facility to ground
Heat Pump Components 3 Main Parts: Underground Piping Pump / Heat Exchanger System Indoor Distribution System System “Concentrates” Natural Heat Instead of Production of Heat by Combustion
Underground Piping Configurations Vertical Installation: 150-500 ft. Ushaped pipe Horizontal Inst.: 1000 ft. pipe buried at 4-8 feet below grade
Heat Pump Uses Predominantly Space Heating / Cooling Currently Over 300,000 buildings in U.S. – Homes, Schools, Commercial Complexes, and Industrial Facilities Water Heating for Hot Water Desuperheaters – uses heat from heat pump’s compressor to heat facility’s hot water Second Heat Exchanger dedicated to hot water
HEAT PUMPS: WHAT DO THEY COST Approx. 2,500 / ton of capacity 7,500 for 3 ton system – 2,500 – 3,000 ft2 home A 3-ton gas-fired furnace and air conditioner would cost approx. 4,000 Positive Cash Flow Investment Monthly Energy Savings Likely to Exceed the Monthly Finance Charge for Borrowing the Additional 3,500
GEOTHERMAL HEAT PUMPS: DO THEY WORK? 1993 EPA Study Conducted in 6 Different Climate Conditions1 Named Heat Pump as Most Efficient Heating and Cooling System Reduction in Energy Consumption of 25%-75% Over Older, Conventional Systems Lowest Annual Operating Costs Little Pollution Produced
HEAT PUMP EFFECTIVENESS IN VARIOUS CILMATES Cold Climate - Minnesota House Owned by Dennis Eichinger 3,400 ft2; Avg. Monthly Energy Bill - 44 Warm Climate – FL House Owned by Keith Swilley 2,000 ft2; Yearly Energy Bill - 253 ( 0.69/day) 1997 Energy Value Housing Award
What do home Owners Say? Even Temperature – no cold spots, no fluctuation Quite Operation Low Maintenance Few Moving Parts – systems typically last 30 yrs. or more; u/g systems frequently warranted up to 50 years.
HEAT PUMPS: HOW MUCH ENERGY SAVINGS? 2-5 kW for each residential application Therefore, 1000 homes avoids the need to generate 2 to 5 MW capacity1 20kW for average commercial installations1 Currently 400,000 Heat Pumps in U.S. 1,500 MW of Heating & Cooling2 – Approx. Savings of 33.3 MM barrels oil/yr. – 40,000 being added each year2
TYPES OF GEOTHERMAL POWER PLANTS Different Types of Plants are Required to Take Advantage of the Particular Characteristics of Each Specific Geothermal Site Main Types of Geothermal Power Plants: Dry Steam Flash Steam Binary Cycle
Dry Steam Geothermal Plants Uses Steam From Geothermal Reservoir Directly Only Requires Removal of Rock Fragments From Steam Prior to Entering Turbines Only Emissions Are Water Vapor
Dry Steam Geothermal Plants Cont’d The “Geysers” in CA Opened in 1960 After 30 yrs. – temp. remains constant; pressure drop from 3.3 to 2.3 MPa near wells Output–2700 MW; enough for San Francisco (pop. 780,000)1
Why Haven’t We Built More Dry Steam Geothermal Plants? Pro: Lowest Technology Required – Lowest Capital Costs Con: Ideal Conditions Required – Few Sites Available (Very Rare) in U.S.
Flash Steam Geothermal Power Plants Injection of Deep, Highpressure Water Into Low-pressure Tanks; Water “Flashes” to Steam Used to Drive Turbines Excess Water Returned to Maintain Pressure in Reservoir
Flash Steam Plants Cont’d Steamboat Springs, NV Plant Initial Conditions – Liquid H2O @ 240 C, Pressures of 24 MPa (hydrostatic pressure)
Binary Cycle Geothermal Power Plants Moderately Hot Water ( 175 C) Passed Through Heat Exchanger Heat Transferred to Secondary Fluid (Low B.P. Fluids (i.e., Propane or Isobutane) Which Is Vaporized (“Flashed”)
Binary Cycle Plants Cont’d Higher Capital Cost Needs High Efficiency Equip. Water Never Contacts Turbine/generator Units Water Returned Directly to Reservoir No Plant Emissions!
Benefits of Geothermal Power Generation Little to No Pollution Flash Plants Emit Only Excess Steam Binary Plants Have No Air or Liquid Emissions! – Expected to Be Dominant Type in Future Lake County – Home of “The Geysers” Geothermal Plants – is One of the Only Counties to Meet CA’s Stringent Air Quality Standards.
Benefits of Geothermal Power Cont’d Emission of Low Quantities of Greenhouse Gasses Homegrown Decreases Dependency On Foreign Energy
Benefits of Geothermal Power Cont’d As Opposed to Burning Fossil Fuels, Current Geothermal Use Prevents the Yearly Emission of:1 22 MM tons of CO2 200k tons of SO2 80k tons of NOx 110k tons of Particulates
Benefits of Geothermal Power Cont’d Some Plants Produce Scale Which Is High in Minerals (Zinc and S) But, The Minerals are Now Recyclable and Can be Sold For a Profit! No Fuel Usage (storage, transfer, disposal, mining)
Benefits of Geothermal Power Cont’d Reliability1: Plants Have Very Little Down Time Avg. Availability is 90% or greater 60-70% for Coal and Nuclear Plants
Benefits of Geothermal Power Cont’d Another Aspect of Resource Reliability “Old Faithful” in Yellowstone National Park Plants Have Been In Use in Italy Since 1913, New Zealand Since 1958 and in CA Since 1960
Benefits of Geothermal Power Cont’d Minimal Land Use Compared to Other Energy Sources Requires 400 M2 of Land Per GW of Power Over a 30 Year Period1 Compare That to Coal and Nuclear Plants Which Require Land for Plant, Mining for Fuel, Storage of Fuel and Wastes, Etc.
Disadvantages of Geothermal Energy Cont’d Start-up Costs Are High Geothermal Plants Require Significant Capital Expenditures, But the Fuel Is Free Cost - 1,500- 5,000 / Installed kW Depending on Plant Size, Resource Temp. And Chemistry1 Cost Of Power to Consumer Currently, 0.05 to 0.08 / Kwh2 Needs to Be 0.03 to Be Competitive
Disadvantages of Geothermal Energy Cont’d Water can be corrosive to plant pipes, equipment If water not replaced back into reservoir, subsidence can occur How Much Water is Needed? Ea. MW requires 500 gpm @ 300 F; 1400 gpm @ 200 F. Some high mineral / metal wastewater and solid waste is produced Smelly gasses – H2S, Ammonia, Boron Release of steam and hot water can be noisy
Disadvantages Cont’d – The Achilles Heel! Limited # of High Temp. Resources Capable of Electric Generation Using Current Technology
Current State of Geothermal Use in the U.S. Currently there is approx. 3,000 MW of Electrical Power being Produced 2 times the production of solar and wind combined 824 MW at “The Geysers” of CA alone There is Approx. 3,900 MW of Direct Use Applications 400,000 Heat Pumps 40 Greenhouses, 30 Fish Farms, 125 District Heating Projects, 10 Industrial Projects, 190 Resorts1
Past Growth of Geothermal Usage
Is There Any Room For Growth? A Gov’t Sponsored Survey Identified: Over 9,000 Thermal Wells and Springs Over 900 low-to-moderate Temperature Geothermal Resource Areas 271 Collocated Communities What is a Collocated Community? City/Community within 5 miles (8 km) of geothermal resource with temps. of at least 50 C (122 F)
Is There Any Room For Growth Cont’d Being A Collocated Community: Gives These Locations Excellent Potential for Near Term Use Makes Them Capable of Supporting Space Conditioning (Heating and Cooling) and Hot Water Applications These 271 Cities/communities Represent 7.4 Million Persons Potential Energy Savings – 18 MM Barrels Oil/year
Is There Any Room For Growth Cont’d Using Today’s Technology, Approx. 6,500 MW Are Available With Modest Technological Advances and Using Known Geothermal Reservoirs, Approx. 18,900 MW Would Be Available
Is There Any Room For Growth Cont’d The 18,900 MW (22k Bar./MW Energy) Of Electric Potential and 18MM Barrels of Oil Savings From the 271 Collocated Communities Represent Approx. 6% of Total U.S. Oil Consumption Is That It? No. The Holy Grail of Geothermal Energy Development Is to Be Able to Tap the Unlimited Energy Closer to the Earth’s Core.
Is There Any Room For Growth Cont’d At Depths of 3-6 Miles, There Is Very Hot, Dry Rock The U.S., Japan, England, France, Germany and Others Are Experimenting With Technologies to Develop This Resource Needed Improvements In Drilling Technologies Needed Ability to Enhance Subsurface Permeability Needed Technology to Detect and Sample Prospective Geothermal Resources
Leave Geothermal Potential in the U.S. The Technology Currently Exists to Provide Almost All Heating and Cooling Using Heat Pumps and About 6% of Total Energy Needs Future Development of Deep Geothermal Resources Can Provide Enough Energy for All Electric and Space Conditioning Needs
Devising a Policy For Accelerating Geothermal Use In the U.S. The Current State of the Geothermal Technology Lends Itself to a Two-phased Approach Targeting Short and Long Term Goals Easy Targets – Achievable in the Short Term (Several Years to a Decade): Phasing Out Systems Currently Using Oil For Heating Which Can Be Replaced With Geothermal Energy Quickly and With Available Technology Implementing District Heating/Cooling Systems in the 271 Collocated Cities
Devising a Policy Cont’d Continued Development of Moderatetemperature Geothermal Resources in 8 Western States With Binary-cycle Power Plants Potential Energy Production – 18,900 MW Overall Potential Savings in Energy From Implementation of the Above Short Term Measures – up to 6% of Total Oil Usage
Devising a Policy Cont’d Long-Term Targets – Several Decades: Phasing Out All Use of Fossil Fuels for Space Conditioning R&D for Technology to access the Unlimited Energy Source Closer to the Earth’s Core - Unlimited Electricity Source Build Power Plants Capable of Providing All Electricity Needs in U.S.
Pros / Cons of Such a Policy Pros: Clean Resource – Very Little Emissions or Overall Environmental Impact Domestic Resource – Not Susceptible to Geopolitical Conflict Economically Sound Alternative – The Fuel Is Free, Rate / KWh Likely to Be Competitive
Pros / Cons of Such a Policy Cont’d Cons: Capital Cost - Significant Initial Investment will be required by Consumers and Industry Duration - May Take Decades to Replace Significant Quantity of the Lost Energy Uncertainty - Replacing More Than a Few Percent of the Lost Energy Relies on Technological Advances, Both in Production and Usage
Mitigation of Policy Negatives: Additional Policy Considerations and Justifications: Gov’t Subsidies to Off-set Capital Costs – Justifiable because of significant potential for environmental savings Provide Increased Clean Air Credits and Reduced Rates for Users of Geothermal Energy – At the Same Time, Increase Rates for Heating Oil and Other Fossil Fuel Users
Conclusion Short Term (Several Years to a Decade): Not a Viable Option to Replace 25% Loss in Oil Imports. At Best, a Valuable Supplement to Replace a Few % of the Lost Energy. Some Valuable Side Effects: Production of Clean Energy – These Policies Are in Concurrence With Goals of Most Pollution-related Statutes Less Reliance on Foreign Sources of Energy Reliable and Renewal Energy Source
Conclusion Cont’d Long Term (Likely Decades for Technology to Provide an Economically Feasible Option): Biggest Impact in Electrical Generation Sectors – the Potential Exists to Provide All Energy Requirements in the U.S. Energy Consumption for Space Heating and Cooling Could Also Change Dramatically