Storage Technology for Process Heat Applications€¦ · • Indirect storage: Thermal energy...

Folie 1ISEC-2005

Storage Technology for Process Heat Applications

Rainer TammeDLR – German Aerospace Center

Institute of Technical Thermodynamics – [email protected]

PREHEAT SymposiumJune 21, 2007 - Freiburg

Folie 2 Storage for Process Heat – Preheat Symposium Freiburg 2007 > Rainer TammeISEC 2005

Presentation directed to:

Energy Storage for Process Heat

Higher temperature than required for domestic heating Temperature range 100 – 300 °C

Water (at low pressure) not applicable as TES material

single phase or 2-phase flow fluids as HTF

Emphasis on PCM storage

Introduction


Process heat T < 100 °C Process heat 100 °C < T < 300 °C Process heat T > 400 °C

Survey - Industrial Process Applications


Requirements

Generation of Solar Heat for Process Heat Applications

Extension of solar heating to higher temperature range

Concentrating collector elements needed

CPC Collector Fresnel Collector Trough Collector


Efficient and economic storage technology neededto meet energy demand and required operation conditions of a specific process

Storage Integration Aspects

Selection of storage concept depends on system aspects


• Direct storage of the primary working fluid:- single phase fluid (thermal oil, pressurized water)- fluid with phase change (Steam accumulator)

• Indirect storage: Thermal energy transferred to separate storage medium- sensible heat storage medium (solid or liquid)- phase change material

Classification of storage systems

2-phase fluid / water-SteamSingle phase fluidHTF Medium

Salt (single component)Eutectic Mixtures

ConcreteThermal oilMolten SaltPressurized Water

Storage Medium

Latent Heat StorageSensible Heat Storage


Direct Storage – Sensible Heat

2- tank storage Single tank storage

Thermal Process

Hot Tank

Cold Tank

5 - 10100 - 200Pressurized Water1 - 5100 - 300Thermal Oil

Pressure [bar]

Temperature range [°C]

Storage Concept


Direct Storage - Steam Accumulator / Sensible Heat

Steam Discharging

Isolated Pressure Vessel

Liquid Phase

Steam

Steam Charging

Liquid water Charging / Discharging

Charging processraising temperature inliquid water volume bycondensating steam

Discharging processgeneration of steamby lowering pressure insaturated liquid watervolume

5 - 100100 - 300Steam AccumulatorPressure [bar]Temperature range [°C]Storage Concept


Indirect Storage – Sensible Heat / Concrete

Test storage at Almeria100 kW, 350 kWh

Test storage at Stuttgart100 kW, 400 kWh

Max. Operation temperature: 400°C


Storage for Process Heat with Steam

Important AREA for process heat applications for the temperaturerange 100-250 °C

• Generation of process steam at low or intermediate pressure for isothermalprocesses

• Food processing• Manufacturing of construction materials• Production of paper, textile industry etc.• Water purification, desalination• Double effect sorption cooling


Potential for high effective cooling systems

Dampfkreislauf

150-155°C

Spei

cher

Kälte

mas

chin

e

Dampfkreislauf4 bar


Characteristic Issues of Steam

93% Evaporation

3% Superheating4% Preheating

10bar steamT - range 160 to 200°C

evaporation temperature (10bar): 180°C0 5 10 15 20 25

80

100

120

140

160

180

200

220

240

Druck [bar]S

iede

tem

pera

tur

[°C

]


Working fluid water/steam:=> Evaporation phase (T=const)

Phase change storage medium=> Melting phase (T=const)

Significant advantage of PCM technology in steam productiondue to constant temperature

Correlation of storage medium and working fluidWhy using Phase Change Material (PCM) ?

spec. enthalpy

tem

pera

ture

solid phaseliquid phase

two phasesolid / liquid

spec. enthalpy

tem

pera

ture

pressurized water

superheated steam

saturated steam


Survey of potential PCM storage materials

0

50

100

150

200

250

300

350

400

100 150 200 250 300 350Temperature [°C]

Ent

halp

y [J

/g]

KNO3

NaNO3NaNO2

KNO3-NaNO3

LiNO3-NaNO3

KNO3-LiNO3

KNO3-NaNO2-NaNO3

LiNO3

Ca(NO3)2-KNO3

KSCN

KSCN

0

50

100

150

200

250

300

350

400

100 150 200 250 300 350Temperature [°C]

Ent

halp

y [J

/g]

KNO3

NaNO3NaNO2

KNO3-NaNO3

LiNO3-NaNO3

KNO3-LiNO3

KNO3-NaNO2-NaNO3

LiNO3

Ca(NO3)2-KNO3

KSCN

KSCN


Flexible PCM`s with Binary Systems

Advantage to cover broad range of temperature and applications


Challenge for PCM: Heat Transfer

solid

liquid

Fluid

Heat transfer coefficient is dominated by the thermal conductivity of the solid PCM

→ Low thermal conductivity is bottle neck for PCM´s


PCM

Kapsel mit PCM

Druckbehälter mitgekapseltem PCM zusätzliche Wärmeübertragungsflächen

Wärmeübertragerrohre

PCM - Composite Material

Increasing heat conductivity

Increasing specific heat transfer surface

Design Options für PCM StorageBasic Concepts


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.

Manufactured by

Inceasing Thermal ConductivityComposite material approach PCM/Graphit

Infiltration

Extrusion+

Compression


Achievements

0

5

10

15

20

25

30

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7Graphitanteil [g/cm3]

Wär

mel

eitfä

higk

eit [

W/m

K]

EG Formkörper ohneSalz

VM EG Formkörper(infiltrieren) ρges=1,6-1,8 g/cm3 (Route 1)

VM EG Pulver(verpressen) ρges=1,9-2,0 g/cm3 (Route 2)

VM NG Schüttung(infiltrieren) ρges=2,1g/cm3 (Route 3)


300 kg Storage Module with composite Salt-Graphite

Heat exchanger tubes with first PCM/Graphite Segment without external containment (left)

Storage module during integration in the test facility (right)


„Sandwich“ design

PCMPCM PCM

PCMPCM PCM

Graphite-foil

PCM

Steam pipe

10 mm

0,5 mm

Graphite-foil

Increasing specific heat transfer surface High effective thermal conductivity through heat conducting elements


Experimental Verification with Nitrate salts

before filling with PCM Im beladenen Zustand

Graphitfolie

PCM liquid


400 kg “sandwich Design” Storage Module


Status of PCM Storage at DLR for the range 120 - 250 °C

100 kW 2)2000 kgKNO3-NaNO3Sandwich concept

10 kW 1)400 kgNaNO2 -NaNO3 - KNO3Sandwich concept

10 kW 2)300 kgCompressed EG / KNO3-NaNO3Composite EG/salt

2-4 kW 1)100 kgKNO3-NaNO3Sandwich concept

Power rangeSizeStorage materialDesignConcept

1) national BMWi Project 2) FP 6 Project


ExampleContainment and TES Material Volume- 100 kWh, providing saturated steam at 140°C –- Impact of exit temperature of the solar field during charging - impact of different HTF`s – oil, pressurised water, steam

Comparison storage systems

heat transfer oil

13.5m ³

0.8m ³

solid media

pressurized water

steam accumulator

PCM

4.2m ³

0.7m ³Case 1: 160°C Case 2: 200°C


Conclusions

large potential for heat storage in the process heat sector

type of the selected collector/HTF has significant influence on thestorage concept

Significant potential for PCM storage in connection withwater/steam systems

New “sandwich design “ and/or new Salt/Graphite compositematerials are solving the bottleneck of the low salt heat conductivity

the Nitrate salt based PCM storage technique is ready for pilot scale demonstration


Further Information

http://www.dlr.de/tt/institut/abteilungen/thermischept/DISTOR

http://www.dlr.de/tt/institut/abteilungen/thermischept

http://www.iea-eces.org/

Joint IEA Annex19 / FP6 DISTOR Workshop in September in Spain

Storage Technology for Process Heat Applications€¦ · • Indirect storage: Thermal energy...

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