Digging Deep for Geothermal and Other Low Temperature Power Generation

Transcription

1 Digging Deep for Geothermal and Other Low Temperature Power Generation Ajilli J Hardy General Electric Global Research Center 29 June American Controls Conference ACC 2011 San Francisco, CA, USA June 29, 2011

2 Great places for more information DOE The Future of Geothermal Energy Sandia s Geothermal Research Idaho National Laboratory s development of hot dry rock Geothermal Education Office

3 Forecast and motivation The geothermal story Transitioning from today s hydrothermal to tomorrow s engineered geothermal systems (EGS) Power generation, opportunities in thermodynamics and controls

4 US electricity generation by source EIA, 2005

5 Low emissions

6 Large, indigenous resource Drilling accounts for upwards of 70% of total plant costs. Advances in drilling technology and lower temperature power generation are needed to reduce the cost of geothermal power generation m 4000 m More regions throughout the US become viable sites for geothermal power generation at greater drilling depths. DOE, INL

7 Natural vs Engineered A geothermal reservoir requires heat, porous rock, and water. Engineered geothermal systems immulate natural ones and transform geothermal energy into a ubiquitous resource. DOE, Geothermal Education Office

8 Range of geothermal resources The impacts of drilling and reservoir technology advances on EGS exploitation, Tester et al.

9 1 year 100EJ Size of the resource

10 Size of the resource 1 year 100EJ

11 Dry Steam Power Plant The Geysers High grade hydrothermal

12 Flash Steam Power Plant geothermal.id.doe.gov Mid grade hydrothermal CalEnergy Navy 1 flash plant

13 Binary power plant Energy-consuming high-pressure pump Good for low temperature geothermal plants (hydrothermal or EGS) Good for low temperatures generally plenty of waste heat in industry Often paired with isobutane as the working fluid "Geothermal Energy-Clean Power from the Earth's Heat", USGS Circular

14 Subcritical Cycle (the standard organic Rankine cycle)

15 Trilateral Flash Cycle (neat idea but inefficient; low net power)

16 Supercritical Cycle (high performance, potentially high pressure/cost)

17 Working fluid screening properties Molecular weight Number of atoms Density h fg h fg (.85 Pcrit) T crit P crit Saturation temperature at atmospheric pressure Viscosity Thermal conductivity GWP ODP Toxicity Flammability Thermal stability Cost/availability Regulations/legislation We identified ~40 high potential working fluids

18 Performance: Comparison to standard fluid choices 134a n-butane R245fa n-pentane

19 Geothermal power Provides clean and safe energy using little land Is renewable and sustainable Generates continuous, reliable baseload power Conserves fossil fuels and diversifies the energy portfolio Avoids importing and benefits local economies Can be cost competitive with present technology

20 Requires advanced drilling and fluid lifting techniques to be applicable in challenging regions Requires a lot of water, which may not be available Can have capacity fluctuations due to changes in ambient temperatures (great controls problem!) Could benefit from new expander technologies, particularly for ultra-low temperature power generation Can induce seismicity Geothermal power

21 Thank you!