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Enhanced Geothermal Systems

Enhanced Geothermal Systems. Physics 160 Rodney Jamie Davies Daniel Lam Kyle Mai. Outline. Technological Background Electrical Capacity and Costs Environmental Impacts Recommendations. What is Geothermal Energy? . Geo: ( Greek) - Earth.

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Enhanced Geothermal Systems

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  1. Enhanced Geothermal Systems Physics 160 Rodney Jamie Davies Daniel Lam Kyle Mai

  2. Outline • Technological Background • Electrical Capacity and Costs • Environmental Impacts • Recommendations

  3. What is Geothermal Energy? Geo: (Greek) - Earth Thermal: Of, relating to, using, producing, or caused by heat.

  4. 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

  5. What can we do with heat? conventional geothermal plants capture hot water from geysers or steam from vents to spin turbines

  6. Surface Geothermal Systems There are three different types surface of Geothermal system designs Flash / Steam Plants Dry Steam Power Plants Binary cycle power plant

  7. Flash or Steam plants • Hot, High pressure water • Turbines generate electricity • Costs 4-6 cents per Kwh.

  8. Dry Steam Plants • Steam passes through turbine • 1050 -1220 degrees F

  9. Binary Cycle Power Plant • Hot water (100 – 300 deg F) • Heat Exchanger • Binary liquid lower specific heat (vaporizes)

  10. Efficiency • Functions like a conventional coal power plant. • Efficiencies vary by • input heat. • At 400 deg. expect ~ 23%, not including parasitic load. • In 2006 the US produced 2850 MW of geothermal electricity

  11. Limitations of surface geothermal • These are surface based • Represent “low hanging fruit” • Most viable sites have been tapped • Not as efficient as Coal, by the numbers

  12. Enhanced Geothermal SystemsAn Idea • Temperature profile • Think about the energy stored in the earth. • How would one take advantage of this?

  13. Enhanced Geothermal Systems in practice • Basically the same technology as surface geothermal for electricity production • Some different nuances • Take advantage of heat ANYWHERE

  14. Nuances • Use drilling technology to access heat of the earth. • Create fractures in rock under ground. • Allows for the flow of water. • Creates an artificial well through which water or fluid can be pumped.

  15. Drilling Depending on depth different solutions are available.

  16. Fracturing • Looking for hot, tectonically stressed, and fractured rock. • over time fractures seal due to secondary mineralization. Low permeability. • Reopen fractures with hydraulic, thermal, and chemical processes.

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

  18. Electrical capacity and Cost

  19. Geothermal capacity • Heat flow though the earth’s crust with: • Flow rate of 59 mW/m2 or 1.9 x 10-2 Btu/h/ft2 • Due to: • Convection and conduction from the mantle core • Radioactive decay of U, Th, K • Useful rock temperature • 150-200 C for electricity production • 100-150 C for other heating purposes

  20. Heat flow map of the US MIT Panel of EGS

  21. Based on MIT report in 2006 • The world’s total geothermal resource is 13,000 ZJ, with 200-2000 ZJ extractable • 65-138 GWe for the worlds (1999) • Capacity of generating 100GWe or more for the US by 2050 • Investment in researches cost 1billion for 15 years in the US • The geothermal energy at 10km under the surface of the US can supply the world’s need for 30,000 years

  22. Electricity production • Different types of cycle give efficiency from 5%-14% depend on temp • Electrical output Where output at 40 C output geofluid

  23. Recoverability ( useful energy) MWe = ɳth xQ rec x 1MJ/1000kJ x 1/t where Qrec= recoverable thermal energy (heat) in kWs (or kJ) = rho*m*C*∆T ɳth= net cycle thermal efficiency (fraction) t = seconds in 30 years = 30 yr x 365 days/yr x 24 hrs/day x 3600 s/hr. = 9.46 x 108 s

  24. Drilling cost • Same for oil, gas and geothermal wells • Depends on: • Well type • Depth • Location of wells

  25. Drilling of oil/gas wells vs. EG wells

  26. Cost and performance of 1MW geothermal plant as a function of temp

  27. Geothermal energy and economics • Reduce in energy price • Meet market price after 2nd year • long-term stability • and characteristic power curve : run all year round

  28. Power curves Traditional electrical power EGS electrical power

  29. Economics-the long run High capital cost (fixed cost) Low variable cost Low maintenance Heating/cooling capacity

  30. Deep Geothermal Energy The Environmental Impacts

  31. Solid and Gas Emissions • No chance of contamination from solid discharge. • Geothermal fluids contains less harmful greenhouse gases. • No Nitrogen Oxide and Sulfur Dioxide. Less acid rain. • Binary Plants have no Carbon Dioxide, however others have 0.2lb/kW-h.

  32. Comparison of Gas Emissions

  33. Landscape Impact and Land Use • Requires relatively less land. • Less environmental alterations and adverse effects. • Produces more power per surface acre compared to nuclear and coal.

  34. Comparison of Land Requirement for Baseload Power Generation

  35. Thermal Pollution • It is one of the biggest concerns due to considerable loss of thermal heat. • Taller cooling towers are needed to contain the waste heat.

  36. Noise Pollution • Noise does occur during initial construction and drilling. • Noise is minimum.

  37. Land Subsidence and Induced Seismicity • In early days of geothermal energy sinking of land was a major problem (subsidence). This was caused by severe drop in reservoir pressure due more fluid removal. However, now through re-injection we keep the pressure balanced. • Possibility of microseismic events from opening of fractures and acoustic noise when drilling.

  38. Disturbance to Wildlife Habitat and Vegetations • Loss of habitat and vegetation is relative minor and non-existence. • Although there will be some alteration to the vegetation, most can restored. • Available technology and waste management significantly reduces and damage to the ecosystem.

  39. Geothermal Plants In Harmony with Nature

  40. Recommendations: An analysis on the reasons to move forward in the development of deep geothermal systems

  41. Expansion of Available Resources 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)

  42. New potential Deep Geothermal extraction or Enhanced Geothermal System locations:

  43. Immense potential • Although Geothermal Energy is not renewable, the available resource is large • 2,000 zettajoules available for extraction. (MIT) Enough to power human civilization for thousands of years • 100,000 MWe is projected to be extracted in the next 50 years

  44. Environment • Low risks of water contamination and low air pollution • Most of the major noise pollutions are during construction only • Seismicity due to EGS operation is minor and not definite

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