Opportunities of High-Temperature Thermal Energy...

Opportunities of High-Temperature Thermal Energy Storage Technologies Dr. Thomas Bauer, Dr. Stefan Zunft, Dr. Marc Linder, Dr. Antje Wörner

German Aerospace Center (DLR) Institute of Engineering Thermodynamics, Stuttgart/Köln Düsseldorf, 16.03.2016 Energy Storage Europe

www.DLR.de/TT • Slide 2 > Thermal Energy Storage > Thomas Bauer

Contents

- High-temperature thermal energy storage (TES) group at DLR - Overview of high-temperature TES technology

- Commercial - Lab/pilot-scale experimental research at DLR

- Molten salt TES technology - Opportunities and applications of high-temperature TES - Summary and conclusion


Institute of Engineering Thermodynamics Prof. A. Thess

Thermal Process Technology Dr. A. Wörner

Electrochemical Energy Technology

Prof. A. Friedrich

System Analysis and Technolgy Assessment Dr. C.Schillings/C.Hoyer-Klick

Computational Electrochemistry

Prof. A. Latz

„... scientific pathfinder for the storage industry...“


Locations and employees

DLR: Approx. 8000 employees across 33 institutes and facilities at 16 sites.

Offices in Brussels, Paris, Tokyo and Washington. Thermal energy storage group: - Stuttgart - Cologne

Cologne

Oberpfaffenhofen

Braunschweig

Goettingen

Berlin

Bonn

Neustrelitz

Weilheim

Bremen Trauen

Lampoldshausen

Stuttgart

Stade

Augsburg

Hamburg

Juelich


Overview of high-temperature TES technology for High Temperatures at DLR

Sensible in Solids

Ceramics, natural rocks

DLR test plant for regenerator type storage

Sensible in Liquids

Molten salt, oil, pressurized

water

DLR test rig for molten salt development

Latent (solid-liquid)

Salt

DLR test plant for PCM-storage

Thermo-chemical

(Gas-solid-reaction)

Salt, salt hydrate, oxide,

hydride

DLR test plant for thermochemical

storage systems


Overview of high-temperature TES technology Key component for sustainable energy supply

Thermal Energy Storage is a Cross-Cutting Technology for renewable energy sources and improved energy efficiency

Heat demand Heat supply


Overview of high-temperature TES technology Technical Approaches

Storage as sensible heat solid liquid heat of fusion heat of sorption heat of reaction

-50°C 100°C 500°C 1000°C 0°C

Temperature Range Maturity

high

low

Energy Density kWh/m3

low

high

20

400

Focus on high-temperature TES: 100 - 1000 °C


- Water/Steam - Steam (saturated, superheated or supercritical) - Pressurized water (40 bar, 250 °C) - Two-phase water/steam (100 bar, 300°C) - Thermal oil (mineral oil, synthetic) - Air/flue gas (unpressurized, pressurized) - Molten salt (unpressurized, 550 °C) - Others (e.g., CO2, ORC fluids)

ONE single storage technology will NOT meet the unique heat carrier characteristics and temperature levels

Overview of high-temperature TES technology Heat carriers: different upper pressure and temperature limits


Overview of high-temperature TES technology Commercial technologies - Sensible heat storage in solids

- Regenerator (1 bar, 1200 °C) - Sensible heat storage in liquids

- Steam Accumulator (40 bar, 250°C) - Molten salt (1 bar, 550 °C) - Thermal oil (1 bar, 300 °C)

Molten Salt, Source: Andasol 1 Steam accumulator/Ruth's, Source: PS10 Regenerator/Cowper


One storage volume (some with stratification)

Two storage volumes (hot and cold tank)

Direct storage of HTF (identical HTF and storage media)

No phase change in the HTF (e.g., hot water tank)

No phase change in the HTF (e.g., two tanks with molten salt) Phase change in the HTF

(e.g., steam accumulator) Direct storage of HTF with additional solid filler

Direct contact of HTF and storage medium (e.g., molten salt/rock; thermal oil/cast iron; water/pebble bed)

This concept is usually not considered, because the filler material can ensure stratification (see left)

Indirect storage with different HTF and storage medium

Direct contact of HTF and storage medium (e.g., Cowper regenerator with gases as HTF)

Direct contact of HTF and storage medium (e.g., two tanks with transport of particles and air as HTF)

Indirect contact of HTF and storage medium (e.g., concrete storage with thermal oil, steam/water as HTF)

Indirect contact of HTF and storage medium (e.g., two tanks with molten salt with thermal oil as HTF)

Commercial technologies

Overview of high-temperature TES technology Classification of sensible heat TES


Sensible heat storage in SOLIDS

Prototype (max. 400 °C)

Pressurized concept

Test rig with integrated heat exchanger

Prototype with clinker (max. 400 °C)

Concrete block with integrated heat exchanger

Adapted regenerators (500-1000°C, 1-65 bar)

Recirculating particle systems (max. 1000°C)

Intermediate air loop and heat exchanger -

CellFlux

Packed bed of natural stones

Experimental DLR research:

DLR test facilities:

Examine solid inventory with air (8 tons solids,

830 °C, 11 bar, 160 kW)

Examine granular flow with integrated

heat exchanger

Quantify particle-wall contact forces in

thermo-cyclic operation

Supply and extract heat for indirect contact TES

with oil (100 kW, 400 °C)

http://de.wikipedia.org/wiki/Bild:RWE-Logo.svg


Experimental DLR research:


Sensible heat storage in LIQUIDS

Chloride salt test rig

20 m³ thermocline tank with filler

Quartzite with and without molten salt

Molten salt development on novel mixtures and process technology

Alternative molten salt TES concept with natural stone as filler

Compatibility of metals and natural stone

Nitrate salt test rig

Validate components and thermocline-filler concept

(4 MWh, max. 560 °C)

Determine phase diagrams, composition and thermal properties

Quantify thermal decomposition limit

of molten salt (100 kg)

Conduct corrosion

experiments

Molten salt Thermocline-filler principle


LATENT heat storage - phase change material (PCM) Experimental DLR research:


PCMFlux prototype

Heat transfer tube with aluminum fins

Moving PCM / constant power concept - PCMFlux

Enhance heat transfer by thermally conductive structure within PCM volume

PCMFlux principle

Supply and extract heat with steam or thermal oil

(25 kW, 250 ºC)

Natural convection effects

Supply and extract heat with thermal oil (4 kW, 400 ºC)

Conduct thermo-mechanical

experiments

PCM-Prototypes (306°C, 0.7/1.5 MWh)

Principle of experiment

Supply and extract heat with thermal oil

(100 kW, 400 °C)


THERMOCHEMICAL heat storage Experimental DLR research: reversible gas-solid reactions RT-1000 °C


Permeability of calcium hydroxide powder

Lime prototype (10 kWh, 450-550°C)

Moving solid particle concepts

Reactor designs considering heat transfer, mass transfer and chemical reaction

Supply and extract heat (by air) and water vapor (max. 1000 °C)

Hydrogen storage test rig

Test rig for salt hydrates with water vapor

(200 °C)

Metal oxide test rig with air

(1100 °C)

Metal hydride prototype for hydrogen

Fundamental transport phenomena in powders

Lime prototype (10 kW, 100 kWh, 450-550°C)

http://www.bine.info/fileadmin/content/News/2015/Bilder/151210_1_kalkspeicher1.jpg


Sensible heat storage in MOLTEN SALTS Characteristics of molten salt - Liquid state over large temperature range (e.g., Solar Salt 260 - 560 °C) - Ability to dissolve a relatively large amount of compounds (corrosion may occur) - Low vapor pressure and high stability - Low viscosity - High heat capacity per unit volume - Several salts are inexpensive/available - Often nontoxic, nonflammable and no explosive phases

Nitrate salt in a glass beaker

Salt crystals at room temperature

Model of molten Sodium Chloride (Source: Baudis 2001)


Sensible heat storage in MOLTEN SALTS Commercial two-tank technology

Direct storage system Indirect storage system for solar tower systems for parabolic trough systems (Storage medium = HTF) (Storage medium ≠ receiver HTF)


Sensible heat storage in MOLTEN SALTS Commercial status of two-tank indirect storage technology

Source: Solar Millennium

Source: Abengoa

- Andasol systems in Spain - 50 MWel

- Storage capacity: 1,000 MWh (8h) - 28,000 t of nitrate salts - 2 tanks: 34 m Ø, 14 m high

- Largest System under construction in

USA (Solana, Abengoa): - 280 MWel

- Storage capacity: 6h - 12 tanks: 37 m Ø, 15 m high


Sensible heat storage in MOLTEN SALTS Focus of the DLR group

System aspects Components

Process technology Material (Upscaling) aspects


Sensible heat storage in MOLTEN SALTS Material aspects

- Development of alternative salt mixtures - Reduced melting temperature < 140 ºC - Thermal stability up to 700 ºC

- Investigation of the decomposition mechanisms of nitrates with parameters such as...

- Temperature - Salt mixture type - Atmosphere type - Surface-to-volume ratio

- Interactions of molten salts with - metals / corrosion - natural stone / filler materials

- Thermal properties determination and post-analysis of composition

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

0 100 200 300 400 500 600 700 800 900 1000Time t [h]

Mol

ar ra

tio N

O2- /N

O3- ,p

O2=

0.21

(air)

[1] 550 °C 100 ml/min

500 °C 600 ml/min (Experiment 1)500 °C 100 ml/min (Experiment 1)500 °C 100 ml/min (Experiment 2)450 °C 100 ml/min


Sensible heat storage in MOLTEN SALTS Alternative thermocline concept with natural stone as filler Aim: - Demonstration of single-tank thermocline concept with filler Operating Parameters: - Operation temperature 150 - 560 °C

with NaNO2, NaNO3, Ca(NO3)2, KNO3, LiNO3 salt mixtures - Storage capacity (ΔT=250K):

200 kWh/m³ with 20 m³ and 4 kg/s Research topics: - Heat / mass transfer, thermomechanics - Material compatibility - Operational aspects, scaling issues - System integration Potential - Previous examination at Sandia

estimate 20 -37 % cost reduction


Sensible heat storage in MOLTEN SALTS TESIS component test-bench Aim: • Test and qualification of molten salt

components for research and industry (e.g. valves, receiver tubes, measurement & control)

• Examine operational molten salt aspects (e.g. freezing events)

Operating Parameters: • Temperature of 150 - 560 °C with

NaNO2,NaNO3,Ca(NO3)2,KNO3,LiNO3 • max. thermal gradient 50 K/s • max. mass flow of 8 kg/s • max. heating power 420 kW • max. cooling power 420 kW


Sensible heat storage in MOLTEN SALTS Test facility for thermal energy storage in molten salt (TESIS)

Process control

Test facility construction

Commis.

2016 2017

Orders


Impact of TES: - Extended operation hours - Reduction of part-load operation - Dispatchable power Example: Crescent Dunes plant 110 MWel

- Commercial operation up to 24/7 - Molten salt as heat transfer fluid

and TES medium - 10 h direct two-tank Solar Salt storage - ΔT = 565 °C - 290 °C = 275 K - Thermal storage efficiency 99 % TES potential: - Cost savings with thermocline/filler concept - Technology transfer to other sectors

Opportunities for High-Temperature TES Improved Concentrating Solar Power (CSP) plants

Source: SolarReserve

Source: SolarReserve


Opportunities for High-Temperature TES Demand-oriented supply of industrial process heat

Impact of TES: - Allows steady waste heat utilization - Can supply backup steam - Supply batch process with steam Example: Electric arc furnace 105 t steel - Utilization of waste heat in the oven gas - TES ensures steady power generation

in the batch process - More than 1000 arc furnaces in the world - TES specifications

- 70 t molten salt NaNO3-NaNO2-KNO3

- ΔT = 400 °C - 225 °C = 175 K


Opportunities for High-Temperature TES Increased Flexibility of Power and Heating Plants

Impact of TES: - Decoupling heat and power production - TES can cover load changes in power

production / steam supply on demand - Contribution to grid stabilization

Example: Collateralisation of process steam in cogeneration power plant - Overall 63 sites (1.963 GWhth, 960 Gwhe) - Thermal energy storage useful

- for heating plants with supply of main steam

- cost efficient provision of power resources

- Temperature 300 °C, 6 MW, 15 MWh

Source: STEAG New Energies GmbH


Opportunities for High-Temperature TES Adiabatic Compressed Air Energy Storage

Impact of TES - Increased efficiency of CAES by integration of

thermal energy storage from 50 to 70 % round trip Example: Electrical storage in power plant scale - 300 MW for grid stabilization - TES specifications:

- Maximum temperature: ca. 400-550 °C - Heat transfer fluid: compressed air (65 bar) - Power output ca. 300 MWth

- Capacity: ca. 1,2 GWh (4 turbine hours) - Constant power level for discharge

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Opportunities for High-Temperature TES Thermal Management in Transportation Impact: - Thermal management / storage is a key issue for electrification of vehicle - Thermochemical TES stores heat at RT and supplies heat on demand - TES can provide comfort heat and extend the operation range of battery vehicles

Example: APU development and demonstration of a H2-Combitank for complex hydrides for coupling with a HT-PEM fuel cell and integration in a vehicle From simulation … to the component … to the demonstration in a vehicle


Opportunities for High-Temperature TES Summary of applications - Energy efficiency improvements

- Improved flexibility of conventional power and heating plants - Demand-oriented supply of industrial process heat - Thermal management for vehicle

- Integration of renewable sources - Storage technologies for solar thermal power plants - Compressed air energy storage for grid stabilization - Power-to-Heat(-to-Power) for grid stabilization


Opportunities for High-Temperature TES Summary and conclusions

1. TES is a vital technology to improve the energy efficiency and to incorporate renewable sources into the grid

2. In addition to commercial TES technologies, several advanced TES technologies are developed to meet the diverse high-temperature demand

3. Decoupling of power (kW) and capacity (kWh) is a major research line for advanced TES (e.g., DLR flux-concepts, recirculating particle concepts)

4. TES is a cross-sectional technology. There is potential of TES technology transfer from recent developments in the solar thermal field to other sectors

5. Power-to-heat(-to-power) gains importance as a new application field

Thank you for your attention !

Institute of Engineering Thermodynamics (ITT), Köln Email: [email protected]

mailto:[email protected]

Opportunities of High-Temperature Thermal Energy...

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