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Folie 1Solar Power Generation, Barcelona 2009
Thermal Energy Storage for Large Scale CSP Plants
Rainer TammeDLR – German Aerospace CenterInstitute of Technical Thermodynamics
rainer.tamme@dlr.de
CUEN – Cambridge – 22.06.2009
Folie 2 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Storage for Large Scale Solar Power Plants
Introducing Storage for CSP - General Aspects
Concrete Storage - Alternative Storage Technologyfor Trough Plants with oil HTF
PCM Storage for Solar Power Plant with DirectSteam Generation
Storage for Central Receiver/Tower Plants
Conclusions
Outline
Folie 3 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Basic Layout of Solar Thermal Power Plant
Folie 4 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Rational for Storage Systems
Providing dispatchable power Increasing share of solar electricity
Reducing cost of LEC
withoutStorage
0%
10%
30%
50%
70%
100%
800 1600 2400 3200 4000 4800
3hStorage
6hStorage
annual full-load operation hours (h/a)
Pow
er p
lant
out
put
Solar onlywithoutStorage
0%
10%
30%
50%
70%
100%
800 1600 2400 3200 4000 4800
3hStorage
6hStorage
annual full-load operation hours (h/a)
Pow
er p
lant
out
put
0%
10%
30%
50%
70%
100%
800 1600 2400 3200 4000 4800
3hStorage
6hStorage
annual full-load operation hours (h/a)
Pow
er p
lant
out
put
Solar onlyor fossil fuel
co- firing
annual operation hours (h/a)
Folie 5 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
TES for CSP Plants - Status
Commercially available storage systems2-Tank sensible molten salt storage based on Nitrate SaltsAlternative materials and concepts tested in lab and pilot scalesensible storage press. water, liquid metals, concrete, ceramic, rocks, metals, sand, others..
latent heat/PCM storagevarious salts systems – Nitrates, Chlorides, Hydroxides, others..chemical storageCH4/CO2-System, N2/H2-Ammonia System, CaO/Ca(OH)2, others..
Why so many different options ?
What is the best solution for areliable, efficient and economic TES system ?
Folie 6 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Storage
Thermal Energy
Thermal Energy
Solar field
Power block
General aspects of thermal energy storage
• TES is interface between solar field and power block• Two dominating parameters to identify most promising TES system
- type of the primary working fluid of the solar field (oil, salt, water/steam, gas)- operation temperature and pressure
Folie 7 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Existing Plants and Future Concepts
Folie 8 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Molten Salt StorageAvailable Storage Technology for Trough Plants with oil HTF
• indirect sensible heat storage- heat transfer fluid and storagemedium are different
- oil/salt heat exchanger- 2-tank concept
• Transfer of SolarTwo experience
• 1st commercial system atANDASOL plant
Folie 9 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Strategies to improve Molten Salt Storage
From 2 tank storage to a single tank storage
Alternative salts• lower freezing temperature• higher thermal stability• lower cost
Folie 10 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Concrete Storage ApproachAlternative new Storage Technology for Trough Plants with oil HTF
Dampfturbine
Kondensator
Niederdruck-vorwärmerEntgaser
SolarerÜberhitzer
SolarerVorwärmer
Zwischen-überhitzer
Dampf-erzeuger
Solarfeld
Ausdehnungs-behälter
Wärme-speicher
Boiler(optional)
Brennstoff
• indirect sensible heat storage- heat transfer fluid and storage medium
are different- integrated heat exchanger
• low cost storage material• solid media approach with no riskof freezing
Folie 11 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
01 05 10 15 20 25 2680
100120140160180200220240260280300320340360380400
Temperature and Flow 01.11 - 26.11.2008
Time in days
Tem
pera
ture
in °
C
01 05 10 15 20 25 26
-20020
Flow
in m
³/h
Oil temperature "hot" sideOil temperature "cold" side
Flow
2008: 2nd Generation Pilot Storage built by
• 400 kWh pilot storage in operation since May 2008• spec. storage capacity 0.65 kWh/(m³·K) verified• over 3300 hours operation above 300 °C• over 230 cycles• Monitoring of thermal and thermo-mechanical behavior• Models for thermal design and system simulation proven • No indication of any degradation effects
Folie 12 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
• Definition a standardized 5 MWh basic module design• Detailed design according to specifications (ΔT, MW, MWh)• Up-scaling to desired capacity by adding modules
Strategy for Commercialization
Large Scale 7h 1000 MWh Concrete Storage
Storage
18 m
2,6 m
4 m
Basic Storage Module Design
Folie 13 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
CSP Plants with DSG - Direct Steam Generation
Power cycleStorage module
Sol
ar c
olle
ctor G
Function of a TES for a DGS plantPreheatingEvaporation / CondensationSuperheating
Folie 14 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Pressurized Water - Ruths Storage at PS10 Plant
20 MWht pressurized water buffer storage for 40 bar saturated steam at PS10• sliding pressure during discharge• sensible storage, thermal capacity proportional to ΔT• high investment cost caused by pressure vessel • No option for up-scaling and high pressure application
Folie 15 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Layout of a Full Scale Storage for DSG Plants
from solarfield
to power block
from power block
to solar field
sensible heat storage unit:preheating / cooling of
condensate
latent heat storage unit: evaporation / condensation
sensible heat storage unit:superheating / cooling of steam
steamdrum
AA
BB
CC
DD
A Preheating unit, feed water inlet / outletB Steam separator, liquid waterC Steam separator, steamD Superheating unit, live steam inlet / outlet
Folie 16 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Features of PCM Storage
Phase change temperature must fit to the evaporation temperatureSalt systems represent possible PCM´s for applications beyond 200 °C Heat transfer of the TES is controlled by thermal conductivity of PCMSalt systems have non-sufficient poor thermal conductivity
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
Finned Tube Designeffective Lamda > 10
W/ mK
PCM/Graphit-Composites
Lamda 5-10 W / mK
Folie 17 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Experimental ValidationLab and pilot test modules with 100 – 2000 kg test modules
• NaNO3 - KNO3 - NaNO2 140 °C melting temperature• NaNO3 - KNO3 220 °C melting temperature• NaNO3 306 °C melting temperature
DISTOR storage integrated in PSA DISS Loop
Folie 18 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Selected ResultsCyclic Operation of NaNO3 PCM-Storage
2000 operating hours172 cycles (280°C – 330°C)Cycles completely reproducible =no degradation of heat transferno degradation of PCM saltHigh specific power level (average of 42 kW/m³ for discharging)Measured storage capacity close to the theoretical value of 100 kWh/m³
Folie 19 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
2009 - Upscaling to MW Scale
PCM Evaporator/Condenser ModuleDimensions: 6 x 1.0 x 1,4 m; 14000 kg sodium nitrate saltCharging/discharging power: 350 kW; Thermal capacity: 700 kWh
Concrete Super-heater ModuleDimensions: 13 x 1.3 x 1,3 m; 23 m³ concreteCharging/discharging power: 120 kW; Thermal capacity: 250 kWh
Folie 20 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Solar Tower Plants with molten Salt HTF + Storage
105875/875 566 288 MS mixtureMS mixtureSolar Two
7 53/53 566 288 MS mixtureMS mixtureCRTF
40 310/310 450 250 HITECTMHITECTMThemis
12 200/200 340 220 steamHITECTMCESA 1
Thermal Capacity [MWht]
Tank Volume[m³]
Cold Tank Temp.
[°C]
Hot Tank Temp.
[°C]
HTFStorage Material
TES System
HITECTM : 40% NaNO2 / 7% NaNO3 / 53 % KNO3 Temp. Range 142 - 450 °CMS mixture: 60% NaNO3 / 40 % KNO3 Temp. Range 220/240 - 600 °C
Folie 21 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Solar Tower Plants with Air Receiver
Open volumetric air receiver plant conceptbeing actually used for the
1,5 MWe Demo Plant Jülich; built by KAM
1 MWh packed bed spherical Al2O3 ceramic
built by DIDIER cost > 100 €/kWh thermal capacity
Folie 22 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
low cost storage materials
Research activities for cost reductionStorage for Solar Tower with Air Receiver
new design concepts
materials with high specific surface
Bulk ceramics Natural rocks
Honey comb ceramicsChecker bricks
Folie 23 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Conclusions
Feasibility of energy storage is the main advantage of Solar Power Plants against large scale PV and Wind Power ONE single storage technology will not meet the requirements of all different solar thermal power plant concepts
Molten salt storage is commercially available for trough/oil technologyHigh investment cost (and risk) are the driver to look for cost effective storage alternativesConcrete storage is a cost effective and low risk approach for trough/oil technology
Future CSP plants will be operated with new fluids at higher temperature to achieve further cost reduction of solar powerPCM storage is most favorable concept for next generation water/steam DSG trough and tower plants
Folie 24 < Rainer Tamme, Storage for CSP > Solar Power Gen, Barcelona 24.02.09
Thank Youfor your attention
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