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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 CenterInstitute 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 / MotivationTechnical options for thermal energy storages in CSP plants
storagesystem
ONE single storage technology will not meet the unique requirements of different solar power plants
Heat Transfer Fluid Collector System Pressure Temperaturesynthetic oil trough/Fresnel 15 bar 400°Csaturated steam tower/Fresnel 40 bar 260°Csuperhaeted steam trough/Fresnel 50-120 bar 400-500°Cmolten salt tower/trough 1 bar 500-600°Cair tower 1 bar 700-1000°Cair tower 15 bar 800-900°C
new concepts
Heat EngineORC
steam turbinegas turbine
Stirling engineothers
www.DLR.de/TT • slide 4 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013
Sensible heat storages Molten Salt Concrete Regenerator Storages
Latent Heat Storages Phase Change Media
Thermochemical Storages Limestone
Introduction / MotivationThermal energy storages under Development at DLR
Nitrate Salts
Compressed Air Energy Storages
CellFlux Concept
www.DLR.de/TT • slide 5 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013
Evaporation 65%
Preheating 16%Super-heating
19%
Parabolicsolar field
Fresnelsolar field Solar towerSolar Receiver
260°C – 400°C 107 bar
Phase change media (PCM) storagesFundamentals
www.DLR.de/TT • slide 6 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013
Phase change media (PCM) storagesFundamentals
0
100
200
300
400
500
600
700
800
900
1000
-100 0 100 200 300 400 500 600 700 800 900 1000Temperatur [°C]
Sch
mel
zent
halp
ie [J
/g]
Wasser
Fluoride
Carbonate und Chloride
Hydroxide
NitrateSalz-
hydrateSalz-Wasser
Paraffine
Hea
tofF
usio
n [J
/g]
Temperature [°C]
www.DLR.de/TT • slide 7 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013
Nitrate salt represent possible PCMs for applications beyond 100 °C
Important PCM criteria: thermal conductivity, melting enthalpy, thermal stability, material cost, corrosion, hygroscopy
0
50
100
150
200
250
300
350
400
100 150 200 250 300 350Temperature [°C]
Enth
alpy
[J/g
]
KNO3
NaNO3NaNO2
KNO3-NaNO3
LiNO3-NaNO3
KNO3-LiNO3
KNO3-NaNO2-NaNO3
LiNO3
0
50
100
150
200
250
300
350
400
100 150 200 250 300 350Temperature [°C]
Enth
alpy
[J/g
]
KNO3
NaNO3NaNO2
KNO3-NaNO3
LiNO3-NaNO3
KNO3-LiNO3
KNO3-NaNO2-NaNO3
LiNO3
Phase change media (PCM) storagesCurrent Materials
www.DLR.de/TT • slide 8 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013
solid
liquid
Fluid
solid
liquid
Fluid
Heat transfer coefficient is dominated by the thermal conductivity of the solid PCM
→ Low thermal conductivity is bottleneck for PCM
Heat carrier: water/steam
Phase Change Material (PCM)
Tube
Fins
schematic PCM-storage concept
Finned Tube Design
effective λ > 10 W/mK
Source: DLR
Phase change media (PCM) storagesChallenges
www.DLR.de/TT • slide 9 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013
Phase change mediaDemonstrated at DLR:
NaNO3 - KNO3 - NaNO2 142°CLiNO3 - NaNO3 194°CNaNO3 - KNO3 222°CNaNO3 306°C
Experimental validation5 test modules with 140 – 2000 kg PCMWorlds largest high temperature latent heat storage with 14 tons of NaNO3 (700 kWh) operating 2010-11
Phase change media (PCM) storagesDevelopment of Prototypes
www.DLR.de/TT • slide 10 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013
PCM-Evaporator module: Capacity ~ 700 kWh PCM: NaNO3 Melting point: 306°C Salt volume: 8.4 m³ Total height 7.5 m Inventory ~ 14 t
Phase change media (PCM) storagesLatest Demonstrator
www.DLR.de/TT • slide 11 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013
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
Concept optimized by FEM analysis
Successful demonstration in lab-scale
Major cost reduction expected
Enhanced heat transfer by extruded longitudinal fins
Source: DLR
Phase change media (PCM) storagesCurrent Developments at DLR
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 forpressurised 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), fluid-
dynamic 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 (particle-discrete 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
Liquid Storage Media (Molten Salt) Solid Storage Media (Concrete)
Molten Salt 49% Heat Exchanger 57%
Structure of capital costs
Limited potential for further cost reductions due to physical constraints New Basis Concept required
CellFlux Storage ConceptMotivation
www.DLR.de/TT • slide 16 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013
CellFlux Storage ConceptInnovative approach
- 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)
solid state storage media
cost effectiveno freezing
Requirements
www.DLR.de/TT • slide 17 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013
CellFlux Storage ConceptInnovative approach
Problem:Low volume specific energy density of air
• large pressure losses• part load operation difficult
Stor
age
volu
me
closed air cycle
Heat exchanger
Fan
from solar field
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 ConceptInnovative approach
www.DLR.de/TT • slide 19 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013
0 5 10 15280
300
320
340
360
380
400
Start and End Temperature Profile with 2°C Maximum Rise of ExitTemperature
Flow Length of Storage [m]
Sto
rage
Mat
eria
l Tem
pera
ture
[°C
]
Initial Temperature Profile
End Temperature Profile
Usage of Storage
2°C Exit Temperature Rise
CellFlux Storage ConceptCurrent Development at DLR
• Theoretical and experimental investigation of sub-system behavior
• Design and construction of demonstration plant
• Development of design and sizing tools
www.DLR.de/TT • slide 20 > Thermal Storage Development at DLR > Markus Eck > Massive Energy Storage > Newport Beach >June 2013
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
Conclusions
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