High Temperature Thermal Energy Storage Development at DLR ECI Massive Energy Storage Conference, Newport Beach, June 23-26 2013 M. Eck, D. Laing, W.-D. Steinmann, S. Zunft German Aerospace Center Institute of Technical Thermodynamics
www.dlr.de/tt slide 2 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 Outline Introduction / Motivation Phase change media (PCM) storages Compressed air energy storages (CAES) Cell-Flux storage concept Conclusions / Outlook Source: Solar Millennium
www.dlr.de/tt slide 3 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 Introduction / Motivation Technical options for thermal energy storages in CSP plants Heat Transfer Fluid Collector System Pressure Temperature synthetic oil trough/fresnel 15 bar 400 C saturated steam tower/fresnel 40 bar 260 C superhaeted steam trough/fresnel 50-120 bar 400-500 C molten salt tower/trough 1 bar 500-600 C air tower 1 bar 700-1000 C air tower 15 bar 800-900 C new concepts storage system Heat Engine ORC steam turbine gas turbine Stirling engine others ONE single storage technology will not meet the unique requirements of different solar power plants
www.dlr.de/tt slide 4 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 Introduction / Motivation Thermal energy storages under Development at DLR Sensible heat storages Molten Salt Concrete Regenerator Storages Latent Heat Storages Phase Change Media Thermochemical Storages Limestone CellFlux Concept Compressed Air Energy Storages Nitrate Salts
www.dlr.de/tt slide 5 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 Phase change media (PCM) storages Fundamentals Solar Receiver Fresnel solar field Solar tower Parabolic solar field Superheating 19% Preheating 16% 260 C 400 C 107 bar Evaporation 65%
www.dlr.de/tt slide 6 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 Phase change media (PCM) storages Fundamentals 1000 900 Schmelzenthalpie Heat of Fusion [J/g] 800 700 600 500 400 300 200 100 Wasser Salzhydrate Salz- Wasser Paraffine Nitrate Hydroxide Carbonate und Chloride Fluoride 0-100 0 100 200 300 400 500 600 700 800 900 1000 Temperature [ C]
www.dlr.de/tt slide 7 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 Phase change media (PCM) storages Current Materials Nitrate salt represent possible PCMs for applications beyond 100 C Important PCM criteria: thermal conductivity, melting enthalpy, thermal stability, material cost, corrosion, hygroscopy 400 350 LiNO 3 300 Enthalpy [J/g] 250 200 150 KNO 3 -LiNO 3 LiNO 3 -NaNO 3 NaNO 2 NaNO 3 100 KNO 3 -NaNO 2 -NaNO 3 KNO 3 -NaNO 3 KNO 3 50 0 100 150 200 250 300 350 Temperature [ C]
www.dlr.de/tt slide 8 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 Phase change media (PCM) storages Challenges liquid solid Fluid Source: DLR schematic PCM-storage concept Phase Change Material (PCM) Heat transfer coefficient is dominated by the thermal conductivity of the solid PCM Low thermal conductivity is bottleneck for PCM Tube Fins Heat carrier: water/steam Finned Tube Design effective λ > 10 W/mK
www.dlr.de/tt slide 9 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 Phase change media (PCM) storages Development of Prototypes Phase change media Demonstrated at DLR: NaNO 3 -KNO 3 -NaNO 2 142 C LiNO 3 -NaNO 3 194 C NaNO 3 -KNO 3 222 C NaNO 3 306 C Experimental validation 5 test modules with 140 2000 kg PCM Worlds largest high temperature latent heat storage with 14 tons of NaNO 3 (700 kwh) operating 2010-11
www.dlr.de/tt slide 10 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 Phase change media (PCM) storages Latest Demonstrator PCM-Evaporator module: Capacity ~ 700 kwh PCM: NaNO 3 Melting point: 306 C Salt volume: 8.4 m³ Total height 7.5 m Inventory ~ 14 t
www.dlr.de/tt slide 11 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 Phase change media (PCM) storages Current Developments at DLR Enhanced heat transfer by extruded longitudinal fins Cost-effective production and assembly Free flow path in vertical direction => no risk with volume change during phase change Controlled distribution of heat in the storage Source: DLR Concept optimized by FEM analysis Successful demonstration in lab-scale Major cost reduction expected
www.dlr.de/tt slide 12 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 Compressed Air Energy Storages (CAES) Fundamentals Objectives: Peak load/reserve power 300 MWel, 4-8 turbine full load hrs. -> supports grid integration of RE Highly efficient due to storage-based heat management -> ~70% storage round-trip efficiency TES technology: Direct contact solid media storage ( regenerator storage ) Specifications: ~600 C @60 bar Design aspects: best heat transfer, fast start-up, efficient solutions for HT-insulation, solutions for pressurised containment, durability of materials in hot & humid atmosphere
www.dlr.de/tt slide 13 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 Compressed Air Energy Storages (CAES) Chosen Concept Direct contact between HTF and storage medium High temperature applications, simple setup Broad choice of applicable inventory materials Typical setup: stacked bricks, packed beds allow cost reduction Challenges: Thermo-mechanical aspects (packed beds), fluiddynamic aspects, durability/erosion, containment
www.dlr.de/tt slide 14 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 Compressed Air Energy Storages (CAES) Current Development at DLR Develop tools and design solutions for optimized thermal design Tools and design solutions considering the thermally induced mechanical loads in large-scale packed storage (particlediscrete simulation) Develop design solutions for the fluid dynamic aspects (flow distribution, pressure loss) Reduce lifetime uncertainty of materials through extensive material testing Validate TES design solutions through pilot-scale testing
www.dlr.de/tt slide 15 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 CellFlux Storage Concept Motivation Liquid Storage Media (Molten Salt) Solid Storage Media (Concrete) Structure of capital costs Molten Salt 49% Heat Exchanger 57% Limited potential for further cost reductions due to physical constraints New Basis Concept required
www.dlr.de/tt slide 16 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 CellFlux Storage Concept Innovative approach solid state storage media cost effective no freezing Requirements - Large heat transfer surfaces (short path length for heat conduction within solid storage material) - Direct contact between storage medium and working fluid (no expensive piping / coating) - Storage volume at atmospheric pressure (no expensive pressure vessels)
www.dlr.de/tt slide 17 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 CellFlux Storage Concept Innovative approach from solar field Heat exchanger closed air cycle Storage volume Problem: Low volume specific energy density of air large pressure losses part load operation difficult Fan to solar field
www.dlr.de/tt slide 18 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 CellFlux Storage Concept Innovative approach
www.dlr.de/tt slide 19 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 CellFlux Storage Concept Current Development at DLR Theoretical and experimental investigation of sub-system behavior Design and construction of demonstration plant Development of design and sizing tools 400 Start and End Temperature Profile with 2 C Maximum Rise of ExitTemperature Storage Material Temperature [ C] 380 360 340 320 300 2 C Exit Temperature Rise Usage of Storage Initial Temperature Profile End Temperature Profile 280 0 5 10 15 Flow Length of Storage [m]
www.dlr.de/tt slide 20 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013 Conclusions Different technical approaches for different process requirements available Phase change media (PCM) storages Demonstration level (700 kwh) Operating Temperature 300 C Focus on system optimization and cost reduction Compressed Air Energy Storages (CAES) State of the art in commercial operation Optimization by use of thermal energy Thermo Mechanical investigation CellFlux Concept Proof of concept Design and Optimization of components System optimization