DLR.de • Slide 1 Synthesis and characterization of new nitrate salt mixtures to molten salt storage Thomas Bauer, Alexander Bonk, Antje Wörner, EERA Conference Nov. 25, 2016 – Birmingham
DLR.de • Slide 2 Contents • Thermal energy storage (TES) and the “ Energiewende ” in Germany • High-temperature TES technologies and applications • Material challenges in TES development • Molten salt TES • Systems and applications • Material aspects • Summary and Conclusions
DLR.de • Slide 3 Scenario of Electricity Generation in Germany Source: Energiereferenzprognose 2014, Zielszenario, Bilder von IER, Stuttgart Hr. Hufendiek Power production [TWh el ] Installed power [GW el ] • Excess renewable electricity requires coupling of sectors (Power-to-X) • Volatile power from PV & wind requires flexibility & storage
DLR.de • Slide 4 Options in the Energy System for Storage, Flexibility and Power-to-X End-use Electricity generation Storage Transportation Conventional Chemical Storage E-mobility, Battery, thermal Power-to-gas/ gas network Power plants management , … Electrolysis, Higher flexibility, hybrid fuel/ electricity Power-to- Liquid/Fuel, … operation, decoupling heat and electricity in CHP, … Gases/Fuels Electrical Grid Industry Demand Side Management, Power-to-Heat, Thermal storage, Power-to-Product/Chemical, Renewable Energy Electrical Storage Hybrid gas-electricity operation ,… Shut-down of plants Battery, Pumped hydro, Concentrating solar power plants (CSP), Pumped thermal energy storage, Demand orientated biomass, Adiabatic compressed air storage, Domestic Geothermal with storage ,… Liquid air Demand Side Management, Power-to-Heat + thermal storage, Thermal energy storage as inexpensive cross-sectoral Heat pump + thermal storage , … technology in all fields (electricity generation, storage, end-use)
DLR.de • Slide 5 Institute of Engineering Thermodynamics Prof. André Thess, Director Jörg Piskurek, Vice Director Computational Energy System Thermal Process Systems Analysis Electrochemical Electrochemistry Energy Integration Technology and Technology Prof. A. Latz Technology Prof. A. Thess Dr. A. Seitz Assessment Prof. J. Kallo Dr. Ch. Schillings / C. Prof. A. Friedrich Hoyer-Klick ~ 190 staff in Stuttgart, Köln, Hamburg, and Ulm ~ 20 Mio. EUR annual budget with 50% third party funding „We are the scientific pathfinder for the energy storage industry“
DLR.de • Slide 6 Locations and employees DLR: Hamburg Approx. 8000 employees across Stade Neustrelitz 33 institutes and facilities at Bremen Trauen 16 sites. Berlin Braunschweig Offices in Brussels, Paris, Goettingen Tokyo and Washington. Juelich Cologne Bonn Thermal energy storage group: - Stuttgart Lampoldshausen - Cologne Stuttgart Augsburg Oberpfaffenhofen Weilheim
DLR.de • Slide 7 Department of Thermal Process Technology Dr. Antje Seitz Thermal Thermal Thermal Thermo- Alternative Power Plant Systems Systems with chemical Fuels Components for Fluids Phase Change Systems Dr. Stefan Zunft Dr. Marc Linder Dr. Uwe Dietrich Dr. Thomas Bauer Dr. Dan Bauer Regenerator and Thermochemical Regenerative Molten salt Latent heat solid media Storage power in liquid storage storage storage hydrocarbons Thermal Upgrade High Technoeconomic temperature H2-Storage evaluation heat exchangers ~ 50 staff in Stuttgart and Köln Focus on high-temperature thermal energy storage technologies
DLR.de • Slide 8 Thermal Energy Storage as a Cross-Sectoral Technology Applications 1. Increased efficiency of energy-intense industrial processes by utilization of waste heat streams 2. Additional operational flexibility in power plants and industrial processes 3. Increased share of renewable energies a. Dispatchability of solarthermal power plants b. Power-to-heat for industrial processes
DLR.de • Slide 9 Thermal Energy Storage as a Cross-Sectoral Technology Integration of TES in systems Storage Technology Application Storage Requirements o Temperature level Sensible o Heat transfer fluid Heat o (Dis-) Charging characteristics o Storage capacity o Power density Latent Heat Key Performance Indicators o Storage density (system) o System cost (CAPEX, OPEX) o Space needed Thermo- o CO 2 -mitigation potential chemical o Operation characteristics …
DLR.de • Slide 10 Established TES Technologies • Cowper-Storage (regenerator storage) • Gaseous heat transfer fluids in direct contact • High temperatures above 1000 ºC Steel industry (hot blase for furnaces) • Molten Salt Storage • Thermal oil or molten salt as heat transfer fluid • Temperatures up to 560 ºC Concentrated solar power plants • Ruths-Storage (steam accumulator) • Steam as heat transfer fluid • Floating pressure, typically up to 250 ° C Steam supply in industry, etc.
DLR.de • Slide 11 Importance of Material Research for TES Development Steps for Storage Systems Material screening System integration Thermal properties of Technical material quality storage materials and fluids Thermophysical properties Stability, compatibility Thermo-mechanical design Heat exchanger / Containment, heat transfer enhancement corrosion Lab-scale tests
DLR.de • Slide 12 Importance of Material Research for TES Materials and Sub-Components Storage material Heat transfer fluid Container Heat exchanger Air, flue gas, Pressurized vessels, Finned tubes, Water, natural rocks, water/steam, molten packed bed designs, shell-and-tube heat ceramics, concrete salt, thermal oil corrosive media exchanger salts, metal oxides Additional components: pumps, valves, connection pipes, insolation, foundation, instrumentation and control devices TES requires more than research on the storage material itself
DLR.de • Slide 13 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 ≠ receiver HTF) (Storage medium = HTF)
DLR.de • Slide 14 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 in USA Source: Solar Millennium (Solana, Abengoa): • 280 Mw el • Storage capacity: 6h • 12 tanks: 37 m Ø, 15 m high Source: Abengoa
DLR.de • Slide 15 Sensible heat storage in MOLTEN SALTS Commercial status of direct storage technology 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 Source: SolarReserve • 10 h direct two-tank Solar Salt storage • Δ T = 565 ° C - 290 ° C = 275 K • Thermal storage efficiency 99 % TES potential: • Cost savings with thermocline/filler concept • Technology transfer to other sectors Source: SolarReserve
DLR.de • Slide 16 Sensible heat storage in MOLTEN SALTS Installed global capacity for grid-connected storage Source: https://www.iea.org/newsroomandevents/graphics/2015-06-30-installed-global-capacity-for-grid-connected-storage.html • CSP grid-connected molten salt storage power > 1500 MW el in 2015 • CSP grid-connected molten salt storage capacity > 30 GWh th in 2015
DLR.de • Slide 17 Sensible heat storage in MOLTEN SALTS Focus of the DLR group System aspects Components Process technology Material (Upscaling) aspects
DLR.de • Slide 18 Sensible heat storage in MOLTEN SALTS TESIS:com - component test-bench
DLR.de • Slide 19 Sensible heat storage in MOLTEN SALTS TESIS:com - 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 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
DLR.de • Slide 20 Sensible heat storage in MOLTEN SALTS TESIS:store - Storage Test Section
DLR.de • Slide 21 Sensible heat storage in MOLTEN SALTS TESIS:store - Storage Test Section Aim: • Demonstration of single-tank thermocline concept with filler Operating Parameters: • Operation temperature 150 - 560 ° 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 20 -37 % cost reduction
DLR.de • Slide 22 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 nitrate salts • Interactions of molten salts with • metals / corrosion • natural stone / filler materials • Thermal properties determination and post-analysis of composition
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