High Temperature Heat Storage for Process Heat and Power Plants

Folie 1 >

High Temperature Heat Storagefor Process Heat and Power Plants

Rainer TammeDLR - German Aerospace Center

Institute of Technical Thermodynamics – Stuttgart/Köln/AlmeriaEUROSOLAR– WCRE “First International Renewable Energy Storage Conference” - IRES I

October 30-31, 2006, Gelsenkirchen, Germany

Folie 2 > Vortrag > AutorDokumentname > 23.11.2004

Folie 2 > High Temperature Heat Storage for CSP – IRES I, Gelsenkirchen, 2006> Rainer Tamme

Definition of “High Temperature”

• Temperature beyond heating and cooling

• Water (non-pressurized) NOT applicable as storage material

> 120 °C

Available storage technology for HT applications

• Storage of sensible heat in fluids and solid materials

• Latent heat storage – PCM storage

Introduction

Available heat transfer media for HT applications

• Single phase fluids – different fluids and gases

• two-phase fluids – water/steam



Rationale - Heat Storage for Process Heat

BMU Studie „Ökologisch optimierter Ausbau der Nutzung erneuerbarer Energien in Deutschland“ DLR, ifeu, WI 2004

Pattern of energy consumption in Germany Future heat generation in Germany

Efficiency improvement

increased contribution from CHP + RES



Pattern of process heat

temperature range 100 – 400 °Cwater/steam as relevant HTF

Examples• Food processing• Manufacturing of construction materials• production of paper, textile industry etc.• Water purification, desalination• double effect sorption cooling

temperature beyond 500 °Cflue gas and air as relevant HTF

Examples• metallurgy • ferrous and non-ferrous metal casting• ceramics manufacturing• glass manufacturing



Rationale - Heat Storage for Power Generation

Future power generation in Germany

BMU Studie „Ökologisch optimierter Ausbau der Nutzung erneuerbarer Energien in Deutschland“ DLR, ifeu, WI 2004

BMU MEDCSP study „Potential and economy of renewable energies in Middle East North African Countries, DLR, 2004

Future power generation in MENA countries

increased CSP plants

increasing RES



Heat Storage for Power GenerationExamples

Heat storage for solar thermalpower plants

Adiabatic compressed air energy storage power plant

Decentralized CHP systems



diversified specificationsPower range from kW to MW Short term storage – minutes to hourLong term storage – several hours to days Capacity from few kWh to GWhTemperature range from 100 to 1000 °Clarge number of primary ad secondary heat transfer media:water/steam, oil, liquid salt, air etc.

Conclusions for designing TES

ONE SINGLE storage technology cannot not meet the huge range of design specifications and operation parameters

Heat Supply

Heat Utilization

Storage

Thermal Energy

Thermal Energy

Storage

Thermal Energy

Thermal Energy



Solid media / Concrete Storage• sensible storage with castable ceramics and concrete• preferred for single phase HTF till 400/500 °C• dual medium indirect storage system with regenerative heat transfer• modular and scalable design from 500 kWh to 1000 MWh

Important applications• parabolic trough solar thermal power plants• waste heat storage < 500 °C• combined heat and power



T_Oil_out, charging

T_Oil_in, discharging

tem

per

atu

re

length

Tt1,c Tt2,c

Ttend,c

Ttend,d

Tt1,dTt2,d

Solid media / Concrete StorageCharacteristic behavior of dual media solid TES

Important issues:• internal heat transfer

• heat conductivityof solid media



Thermal Engineering and Simulation Tools

temperature distribution

power and capacity



2 year operation of 2 modules350 kWh castable ceramic350 kWh concrete

Second generation concrete400 kWh storage moduledeveloped with

Expected investment cost~ 25 €/kWh(large scale, 6 h cycles)

Concrete storage is ready for scale-up and demonstration

System integration and operationstrategy is important issue

Concrete Storage - Current Status



PCM Storage - Motivation

93% Verdampfung

3% Überhitzung4% Überhitzung

55% Verdampfung

33% Vorwärmung 12% Überhitzung

10bar process steamT - range 160°C to 200°C

evaporation temperature 179°C

100 bar Rankine cycle Tmax 400°CReheating and feed water pre-heating

spez. Entropie

Tempe

ratur

Latentspeicher sensiblerSpeicher

sensiblerSpeicher

Preheating evaporation superheatingWater wet steam Superheated

steam

T profile for HTF water/steam

spez. Entropie

Tempe

ratur


sensiblerSpeicher

solid –melting - liquid

sensibelsolid

Latent-heat

sensibelliquid

T profile for solid/liquid PCMspez. Entropie

Tempe

ratur


sensiblerSpeicher


steam


steam

T profile for HTF water/steam

spez. Entropie

Tempe

ratur


sensiblerSpeicher


sensibelsolid

Latent-heat

sensibelliquid

T profile for solid/liquid PCMspez. Entropie

Tempe

ratur


sensiblerSpeicher


sensibelsolid

Latent-heat

sensibelliquid

spez. Entropie

Tempe

ratur


sensiblerSpeicher


sensibelsolid

Latent-heat

sensibelliquid


sensibelsolid

Latent-heat

sensibelliquid

T profile for solid/liquid PCM

Preference for PCM storagetwo-phase flow HTFmainly water/steam

industrial process steamrankine cycle power generation



Approaches for Efficient PCM Storageto solve heat transfer limitations of PCM

Improved heat transferImproved storage materials

PCM composite

PCM with superiorthermal conductivity

Tubular heat exchangerwith externally arranged PCM

PCM composite

PCM with superiorthermal conductivity

Tubular heat exchangerwith externally arranged PCM

Increase heat transfer area

Macro-EncapsulationIsothermal steam accumulatorswith PCM

Tubular heat exchangerwith finned tubes

(Sandwich Concept)

Increase heat transfer area

Macro-EncapsulationIsothermal steam accumulatorswith PCM

Tubular heat exchangerwith finned tubes

(Sandwich Concept)



New improved composite PCM´sFocussing on Nitrate salts and Graphite matrix

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

Intercalation and exfoliation

Grinding

graphite

Expandedgraphite

worm

Ground expandedgraphite

Compressed expandedgraphite plates

Compression

1.

2.3.

Intercalation and exfoliation

Grinding

graphite

Expandedgraphite

worm

Ground expandedgraphite

Compressed expandedgraphite plates

Compression

1.

2.3.

Low pressuresteam systems

High pressuresteam systemsCommercial PCM

composite materialsmanufactured by



PCM Storage – Current StatusProcess steam storage and solar steam generation

• design concept for improved PCMstorage scientifically proven

• new composite PCM with high thermalconductivity developed

• validated in 10 kWh storage modules• 100 kW pilot storage under construction



Compressed air storage technologyfor large scale electricity storage

AdiabaticCAES

Source: Electricity Storage Association

Survey on electricity storage technologies

Specific investment cost



M MotorLP Low Pressure CompressorHP High Pressure CompressorST Steam TurbineG Generator

LP STM GHP

CavernAir Intake

Heat Storage

ST

Air Outlet

Adiabatic CAES - Approach

Pure storage technology, locally emission-freeHigh storage efficiency

Heat storage neededDemanding advancement of turbo engines– compressor and turbine



40 m36 m 35 m

3 m 2 m

sym

met

ric a

xis 9 m

5 m

3 m 1 m

4 m

4 m

22 m

activ

e co

olin

g

Nitrate salt + Mineral oil

Nitrate salt + Mineral oil

Cast ironConcreteChecker brick

Natural stone

Storage medium

IndirectIndirectDirectDirectDirectDirect

One-tank thermocline

Two-tank configuration

Cast iron slabs

Concrete walls

Cowper-type

Rock bedConcept

Liquid media TESSolid media TES

Heat Storage Concepts for ACAES



Basic design concept defined• layout of storage material configuration• pressure vessel-containment design• isolation• Investigation of storage materials

(thermo-physical and thermo-mechanical properties)

• Charging/discharging behavior• Cost estimation

Heat Storage Development for ACAES



structureair l

ayer

wal

l

inve

ntor

y

Heat Storage for ACAES – Current Status

Further development to verify design, materials and simulation tools to establish a basis for a 30 MW demonstration plant

Basic design concept developed by



Conclusions

Continuous and even more research and development effort is needed to bring the new storage approaches to commercial stage

Concrete storage technology is available until 400 °Cfor waste heat storage, CHP and solar trough plants

Energy storage is a key issue for efficient energy utilizationto reduce fossil fuels consumption and CO2 emissionsand increased heat and power generation with RESto balance unequal supply und demand profiles

Advanced storage technologies – PCM or ACAES - have large potential to provide efficient and economic storage for process heat and power plants



Thank Youfor your attention

High Temperature Heat Storage for Process Heat and Power Plants

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