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Groß Schönebeck Research Power Plant. A. Saadat , S. Frick, S. Kranz, H. Francke , A. Kupfermann, M. Thorade Helmholtz Centre Potsdam GFZ German research Centre for Geosciences Section 4.1 Reservoir Technologies. Location of the reserach well.
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Groß Schönebeck Research Power Plant A. Saadat, S. Frick, S. Kranz, H. Francke , A. Kupfermann, M. Thorade Helmholtz Centre Potsdam GFZ German research Centre for Geosciences Section 4.1 Reservoir Technologies
Location of the reserach well Project funded by Federal Government: development of base load electricity from geothermal resources • old gas exploration well • research well in sedimentary rocks at • 4.3 km depth, 150 °C • Goal: Proof of sustainable use of geothermal energy in sedimentary basins
Lab container Main building Injection wellE GrSk 3/90 20 m Production wellGtGrSk 4/05 Currently planning 3 pressure level ORC GroßSchönebeck research platform Current status
Optimization potential Component level • Heat exchangers • Turbine • Cooling tower Power cycle • Layout • Working fluid • Automation & control Design and Modeling • Holistic design • Coupling of subsystems • Transient behavior
Optimization criteria • Gross power output • Efficiency • Net power output • Consumption of auxiliaries • Investment cost • Heat Exchanger Area • Operating cost • Cost per kWh generated • Return on Investment • Interest rate Design point versus annual load duration curve • Partial load efficiency • Reliability and availability • Annual full load hours Combined heat and power
Pinch Point Minimize 2nd law losses • Supercritical • Fluid mixtures • Pressure levels
Pinch point – 3 pressure levels Three independent cycles • Individual optimization • Fluid selection • Automation and control
550 kW 120°C 21 bar 325 kW 90°C 13 bar 150 kW 70°C 8 bar
Turbo generator prototype • Special design for ORC • Range • Working fluids • Cost • No moving seals • Reliability and efficiency • No gearbox • Simple construction
Cooling tower • Influence of auxiliary power consumption on net power • Influence of climate and weather • Evaporation and replacement water • Operation, automation and control • Water quality, scaling
Cooling tower • Design point 1 • Rel. humidity 75% • Temperature 10°C • Design point 2 • Rel. humidity 65% • Temperature 15°C → Optimization and specification of components should always be done in the context of the system
Types of heat exchangers • Plate Heat Exchangers • Economizer, Evaporator, Condenser • Tube & Shell prototypes • Condenser Source: www.gea-phe.com www.vahterus.com
Instrumentation for each HX: • Mass flow • Pressure in & out • Temperature in & out • → full balance Welded Sealed, Titanium Plate Tube & Shell Brazed Welded, Round Plate Tube & Shell Welded, Round Plate Semi-welded cassettes Semi-welded cassettes
Heat transfer correlations Reduce 3D problem to 1D correlation More than 2200 ISI-papers about heat transfer in 2005! Goldstein, R. et. al. (2010), 'Heat transfer--A review of 2005 literature', International Journal of Heat and Mass Transfer53 (21-22) , 4397 - 4447 .
Water + glycol intermediate cycle • Decoupling of geofluid cycle and power cycle • Well known fluid properties for water + glycol • Well known heat transfer correlations for liquid water + glycol • Possibility to influence temperatures through water + glycol massflow • Only one heat exchanger has contact to aggressive geofluid • About 3 K temperature loss
Boiling Heat Transfer Asymptotic transition between two phenomena: Convective and nucleate boiling Power based addition: Steiner, D. & Taborek, J. (1992), 'Flow Boiling Heat Transfer in Vertical Tubes Correlated by an Asymptotic Model', Heat Transfer Engineering 13 , 43 - 69 .
Optimization of heat exchangers • ΔT related losses • Δp related losses • All losses are thermodynamically irreversible processes • Entropy generation is the common measure for irreversibility H. Herwig and F. Kock. Direct and indirect methods of calculating entropy generation rates in turbulent convective heat transfer problems. Heat and Mass Transfer, (43)3:207--215, 2007
Modelica • Modelling language for physical systems • Everything is possible • Not a ready-to-use power plant simulation software • Object-oriented: • Replace simple model with advanced model as long as connectors are compatible • Inheritance: Re-use code • Debug each object • Export Model to Matlab/Simulink • Acausal Modelling
Property functions and frequency of use + Iterative algorithms !!! Wagner, W. et.al.: The IAPWS Industrial Formulation 1997 fortheThermodynamic Properties ofWater and SteamIn: Journal of Engineering for Gas Turbines and Power , Vol. 122 , Nr. 1 ASME (2000) , S. 150-184 .
Geofluid properties EoS gas phase Gas phase contents Gases + H2O No salt Gas phase properties Geofluid contents: H2O + Gases + Salts Geofluid properties Model for 2-phase fluid Solubility & Equilibrium Processes & Components Liquid phase contents: H2O + Gases + Salts Liquid phase properties EoS liquid phase Mao, S.; Duan, Z.; Hu, J. & Zhang, D. (2010), 'A model for single-phase PVTx properties of CO2-CH4-C2H6-N2-H2O-NaCl fluid mixtures from 273 to 1273 K and from 1 to 5000 bar', Chemical Geology 275 (3-4) , 148 - 160 .
Summary & Outlook • 3 pressure level ORC, independent cycles • Working fluid • Automation • Intermediate cycle • Heat transfer research • Simulate partial load or temperature levels • Comprehensive instrumentation and monitoring • Full balances for all components • Validated models of all subsystems • Model coupling of subsystems • Reservoir, Cooling tower, … → Best practice guide “How to design a geothermal power plant (in northern Germany”