Opportunities of High-Temperature Thermal Energy Storage Technologies

Transcription

1 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, Energy Storage Europe

2 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

3 Slide 3 > Thermal Energy Storage > Thomas Bauer Institute of Engineering Thermodynamics Prof. A. Thess Electrochemical Energy Technology Prof. A. Friedrich Computational Electrochemistry Prof. A. Latz Thermal Process Technology Dr. A. Wörner System Analysis and Technolgy Assessment Dr. C.Schillings/C.Hoyer-Klick... scientific pathfinder for the storage industry...

4 Slide 4 > Thermal Energy Storage > Thomas Bauer Locations and employees DLR: Approx employees across 33 institutes and facilities at 16 sites. Offices in Brussels, Paris, Tokyo and Washington. Thermal energy storage group: - Stuttgart - Cologne Juelich Cologne Bonn Bremen Trauen Braunschweig Lampoldshausen Stade Hamburg Goettingen Neustrelitz Berlin Stuttgart Augsburg Oberpfaffenhofen Weilheim

5 Slide 5 > Thermal Energy Storage > Thomas Bauer Overview of high-temperature TES technology for High Temperatures at DLR Sensible in Solids Sensible in Liquids Latent (solid-liquid) Thermochemical (Gas-solidreaction) Ceramics, natural rocks Molten salt, oil, pressurized water Salt Salt, salt hydrate, oxide, hydride DLR test plant for regenerator type storage DLR test rig for molten salt development DLR test plant for PCM-storage DLR test plant for thermochemical storage systems

6 Slide 6 > Thermal Energy Storage > Thomas Bauer Overview of high-temperature TES technology Key component for sustainable energy supply Heat supply Heat demand Thermal Energy Storage is a Cross-Cutting Technology for renewable energy sources and improved energy efficiency

7 Slide 7 > Thermal Energy Storage > Thomas Bauer Overview of high-temperature TES technology Technical Approaches Storage as sensible heat solid liquid Temperature Range 0 C -50 C 100 C 500 C 1000 C Energy Density kwh/m 3 20 low Maturity high heat of fusion heat of sorption heat of reaction 400 Focus on high-temperature TES: C high low

8 Slide 8 > Thermal Energy Storage > Thomas Bauer Overview of high-temperature TES technology Heat carriers: different upper pressure and temperature limits - 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., CO 2, ORC fluids) ONE single storage technology will NOT meet the unique heat carrier characteristics and temperature levels

9 Slide 9 > Thermal Energy Storage > Thomas Bauer 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) Regenerator/Cowper Steam accumulator/ruth's, Source: PS10 Molten Salt, Source: Andasol 1

10 Slide 10 > Thermal Energy Storage > Thomas Bauer Overview of high-temperature TES technology Classification of sensible heat TES Direct storage of HTF (identical HTF and storage media) Direct storage of HTF with additional solid filler Indirect storage with different HTF and storage medium Commercial technologies One storage volume (some with stratification) No phase change in the HTF (e.g., hot water tank) Phase change in the HTF (e.g., steam accumulator) Direct contact of HTF and storage medium (e.g., molten salt/rock; thermal oil/cast iron; water/pebble bed) Direct contact of HTF and storage medium (e.g., Cowper regenerator with gases as HTF) Indirect contact of HTF and storage medium (e.g., concrete storage with thermal oil, steam/water as HTF) Two storage volumes (hot and cold tank) No phase change in the HTF (e.g., two tanks with molten salt) This concept is usually not considered, because the filler material can ensure stratification (see left) 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., two tanks with molten salt with thermal oil as HTF)

11 Slide 11 > Thermal Energy Storage > Thomas Bauer Sensible heat storage in SOLIDS Experimental DLR research: Adapted regenerators ( C, 1-65 bar) Recirculating particle systems (max C) Intermediate air loop and heat exchanger - CellFlux Concrete block with integrated heat exchanger Packed bed of natural stones Pressurized concept Test rig with integrated heat exchanger Prototype with clinker (max. 400 C) Prototype (max. 400 C) 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)

12 Slide 12 > Thermal Energy Storage > Thomas Bauer Sensible heat storage in LIQUIDS Experimental DLR research: Alternative molten salt TES concept with natural stone as filler Molten salt development on novel mixtures and process technology Compatibility of metals and natural stone 20 m³ thermocline tank with filler Molten salt Thermoclinefiller principle Nitrate salt test rig Chloride salt test rig Quartzite with and without molten salt DLR test facilities: Validate components and thermocline-filler concept (4 MWh, max. 560 C) Quantify thermal decomposition limit of molten salt (100 kg) Conduct corrosion experiments Determine phase diagrams, composition and thermal properties

13 Slide 13 > Thermal Energy Storage > Thomas Bauer LATENT heat storage - phase change material (PCM) Experimental DLR research: Enhance heat transfer by thermally conductive structure within PCM volume Moving PCM / constant power concept - PCMFlux Natural convection effects Heat transfer tube with aluminum fins PCM-Prototypes (306 C, 0.7/1.5 MWh) PCMFlux principle PCMFlux prototype Principle of experiment DLR test facilities: Supply and extract heat with steam or thermal oil (25 kw, 250 ºC) Supply and extract heat with thermal oil (4 kw, 400 ºC) Conduct thermo-mechanical experiments Supply and extract heat with thermal oil (100 kw, 400 C)

14 Slide 14 > Thermal Energy Storage > Thomas Bauer THERMOCHEMICAL heat storage Experimental DLR research: reversible gas-solid reactions RT-1000 C Reactor designs considering heat transfer, mass transfer and chemical reaction Moving solid particle concepts Fundamental transport phenomena in powders Lime prototype (10 kwh, C) DLR test facilities: Metal hydride prototype for hydrogen Lime prototype (10 kw, 100 kwh, C) Permeability of calcium hydroxide powder Supply and extract heat (by air) and water vapor (max C) Test rig for salt hydrates with water vapor (200 C) Metal oxide test rig with air (1100 C) Hydrogen storage test rig

15 Slide 15 > Thermal Energy Storage > Thomas Bauer Sensible heat storage in MOLTEN SALTS Characteristics of molten salt - Liquid state over large temperature range (e.g., Solar Salt 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 Salt crystals at room temperature Nitrate salt in a glass beaker Model of molten Sodium Chloride (Source: Baudis 2001)

16 Slide 16 > Thermal Energy Storage > Thomas Bauer Sensible heat storage in MOLTEN SALTS Commercial two-tank technology Direct storage system for solar tower systems (Storage medium = HTF) Indirect storage system for parabolic trough systems (Storage medium receiver HTF)

17 Slide 17 > Thermal Energy Storage > Thomas Bauer Sensible heat storage in MOLTEN SALTS Commercial status of two-tank indirect storage technology - Andasol systems in Spain - 50 MW el - 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): MW el - Storage capacity: 6h - 12 tanks: 37 m Ø, 15 m high Source: Solar Millennium Source: Abengoa

18 Slide 18 > Thermal Energy Storage > Thomas Bauer Sensible heat storage in MOLTEN SALTS Focus of the DLR group System aspects Material aspects Process technology (Upscaling) Components

19 Slide 19 > Thermal Energy Storage > Thomas Bauer 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 Molar ratio NO 2 - /NO3 -,po2 =0.21(air) [1] 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 Time t [h]

20 Slide 20 > Thermal Energy Storage > Thomas Bauer 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 C with NaNO 2, NaNO 3, Ca(NO 3 ) 2, KNO 3, LiNO 3 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 % cost reduction

21 Slide 21 > Thermal Energy Storage > Thomas Bauer 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 C with NaNO 2,NaNO 3,Ca(NO 3 ) 2,KNO 3,LiNO 3 max. thermal gradient 50 K/s max. mass flow of 8 kg/s max. heating power 420 kw max. cooling power 420 kw

22 Slide 22 > Thermal Energy Storage > Thomas Bauer Sensible heat storage in MOLTEN SALTS Test facility for thermal energy storage in molten salt (TESIS) Orders Process control Test facility construction Commis.

23 Slide 23 > Thermal Energy Storage > Thomas Bauer Opportunities for High-Temperature TES Improved Concentrating Solar Power (CSP) plants Impact of TES: - Extended operation hours - Reduction of part-load operation - Dispatchable power Example: Crescent Dunes plant 110 MW el - 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 C = 275 K - Thermal storage efficiency 99 % TES potential: - Cost savings with thermocline/filler concept - Technology transfer to other sectors Source: SolarReserve Source: SolarReserve

24 Slide 24 > Thermal Energy Storage > Thomas Bauer 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 NaNO 3 -NaNO 2 -KNO 3 - ΔT = 400 C C = 175 K

25 Slide 25 > Thermal Energy Storage > Thomas Bauer 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 GWh th, 960 Gwh e ) - 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

26 Slide 26 > Thermal Energy Storage > Thomas Bauer 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 MW for grid stabilization - TES specifications: - Maximum temperature: ca C - Heat transfer fluid: compressed air (65 bar) - Power output ca. 300 MW th - Capacity: ca. 1,2 GWh (4 turbine hours) - Constant power level for discharge

27 Slide 27 > Thermal Energy Storage > Thomas Bauer 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 H 2 -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

28 Slide 28 > Thermal Energy Storage > Thomas Bauer 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

29 Slide 29 > Thermal Energy Storage > Thomas Bauer 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

30 Thank you for your attention! Institute of Engineering Thermodynamics (ITT), Köln