thermal energy storage for large scale csp plants - cuen csp.pdf · folie 1 solar power generation,...

Folie 1Solar Power Generation, Barcelona 2009

Thermal Energy Storage for Large Scale CSP Plants

Rainer TammeDLR – German Aerospace CenterInstitute of Technical Thermodynamics

[email protected]

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


Basic Layout of Solar Thermal Power Plant


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%

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100%

800 1600 2400 3200 4000 4800

3hStorage

6hStorage


Pow

er p

lant

out

put

0%

10%

30%

50%

70%

100%

800 1600 2400 3200 4000 4800

3hStorage

6hStorage


Pow

er p

lant

out

put

Solar onlyor fossil fuel

co- firing

annual operation hours (h/a)


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 ?


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


Existing Plants and Future Concepts


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


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


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


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


• 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


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


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


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


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


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


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


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


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


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


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


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


Thank Youfor your attention

thermal energy storage for large scale csp plants - cuen csp.pdf · folie 1 solar power generation,...

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