Deep Eutectic Salt Formulations Suitable as Advanced Heat Transfer Fluids

8/18/2019 Deep Eutectic Salt Formulations Suitable as Advanced Heat Transfer Fluids

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1 | Program Name or Ancillary Text eere.energy.gov

Solar Energy Technologies Program Peer Review

Deep Eutectic Salt Formulations Suitable as

Advanced Heat Transfer FluidsJustin W. Raade, PhD

Halotechnics, Inc.

[email protected]

May 26, 2010

Award No. DE-FG36-08GO18144CSP

This presentation does not contain any proprietary, confidential, or otherwise restricted information


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2 | Solar Energy Technologies Program Halotechnics, Inc. eere.energy.gov

Overview

• Project start date: January 1,2009

• Project end date: December31, 2011

• Percent complete: 34%

• This project will enable the cost ofCSP electricity to be reduced by15%. We are developing a heattransfer fluid that will allow hightemperature operation of CSPplants.

• Total project funding

– DOE share: $1.5 million

– Contractor share: $564,000

• Funding received in FY09:$500,000

• Funding for FY10: $500,000

Timeline

Budget

Barriers

Partners• Halotechnics, Inc.

• Sandia National Laboratories willpartner in Phase 3 for field testing.


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Background and objective

• Concentrating Solar Power (CSP)is lowest cost solar electricity

– 13-17 ¢/kWh

• Must reduce cost of CSP tocompete with fossil fuels

•

Novel materials needed for heattransfer fluid (HTF) and thermalenergy storage (TES)

HTF

TES

Project Objective: Conduct

an R&D program focusing ondeep eutectic (low-melting)

salt formulations suitable as

advanced heat transfer fluids


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Project milestones

• Milestone 1: Approximately 250 (100 minimum) primary candidate formulationsCandidates must meet the following criteria:

– freezing point less than 80°C (100°C maximum)

– thermal stability as a liquid to about 500°C (450°C minimum)

• Milestone 2: Approximately 10 (5 minimum) secondary candidate formulations.Candidates must meet the following criteria:

– viscosity of about 1 centipoise (10 centipoise maximum) to about 500°C

– vapor pressure of about 5 atmospheres (10 atmospheres maximum) to about 500°C

– specific gravity in the range of 0.7-1.7 (0.5 minimum, no maximum) to about 500°C

– heat capacity in the range of 2-5 J/g/K (1 J/g/K minimum, no maximum) to about 500°C

• Milestone 3: At least 1 commercial production candidate. Candidate(s) must meetthe following criteria (as determined by field testing at Sandia):

– sufficient pumpability

– thermal cycling tolerance

– sufficient long-term thermal stability

– chemical compatibility with common stainless steels


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Project timeline

Status May 2010


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Materials discovery workflow

Powdernium powderdispensing robot

Parallel Melting PointWorkstation (PMP) with

96 channel capability

High temperaturefurnace formelting/mixing

• Symyx software and R&D tools enable automatedworkflow

• Maximum throughput of 500 blends/week• High throughput workflow can be leveraged to

develop advanced materials similar to HTF suchas thermal energy storage materials

Automation Studio tocreate experiments andmanage data


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Thermal properties characterization

• Thermal stability

– High temperature thermogravimetricanalysis (TGA)

– TA Instruments Q500 with 16position autosampler

• Heat capacity – Differential scanning calorimeter

(DSC)

– TA Instruments Q200 with 50position autosampler

• Viscosity

– Brookfield viscometer (to beacquired)

– Capable of testing up to 300 °C,may modify for higher temperature

• Molten salt chemistry

– Symyx Low Thermal Mass Reactorfor testing salts up to 500 °C

TGA with 16 position

autosampler

DSC with 50 position

autosampler

High temperature

viscometer

Low Thermal Mass Reactor



Milestone and results

•

Milestone 1: Approximately 250 (100minimum) primary candidate formulations

• Candidates must meet the following criteria:

– freezing point less than 80°C (100°Cmaximum)

– thermal stability as a liquid to about 500°C

(450°C minimum)

Meltingpoint

Thermalstability

Primary candidate

formulations

Primary screen

189

5030

138

5030 blends screened for melting point189 blends met melting target 500 °C

Phase 1 results



Heat transfer fluid for trough plants

• Must increase plant operating temperature to 500 °C to increase thermalefficiency and reduce levelized cost of electricity would enable$0.02/kWh reduction according to Sandia study

• Current plants limited to 390 °C by synthetic oil heat transfer fluid (VP-1)

• Existing salt-based heat transfer fluids have unacceptably high meltingpoint, typically 142 °C (Hitec), preventing any CSP applications

• Can combine best attributes of both with “deep eutectic” salt formulations high thermal stability of salt with low melting point of synthetic oil

Recent breakthrough: Discovered formulations with melting

point less than 75 °C and thermal stability to 500 °C

6005004003002001000 °C

synthetic oil

traditional salt

Halotechnics Solar Salt Patent Application No. 61325725



Deep eutectic salt formulations

• Eutectic salt formulations exhibit low melting points

• Screened over 5000 unique blends of nitrates, nitrites, and other salts

• Discovered many eutectic blends with melting points below 75 °C

• Large number of possible salt formulations is a combinatorial problem andsignificant barrier to entry

Binary mixture Ternary mixture Quaternary mixture High order mixtures

Na + K = 220 °C Binary + Li = 120 °C Ternary + Ca = 90 °C Quaternary +++ = 75 °C



Thermal stability

• Blends containing nitrite are susceptible to oxidation in air

• TGA screening method produces relative ranking of thermal stabilityof blends, not absolute measurement

• Long term field testing is planned for Phase 3

TGA thermal stability behavior of Hitec nitrate-onlyblend in air and nitrogen.

TGA thermal stability behavior of Hitec nitrate/nitriteblend in air and nitrogen.



Data flow

CONSTRAINTS• Cost• Safety• Stability• Previous results

EXPERIMENT DESIGN

DATA ANALYSIS

Library Studio Screening workflow Data

FEEDBACK



Baseline Li-Na-K-NO3 system

Typical PMP data All values in mol%



Visualization of quaternary phasespace

• Each end face of triangular prism is ternarysystem (Li-Na-K-NO3 and Li-Na-K-NO2 inthis example)

• Plot series of cross sections at constant NO2level to visualize melting point data

Li

Na

K

40%



Visualization of quinary phase space

ion 5

ion 6



Visualization of 7 ion phase space

Ion 5

ion 6

Ion 5

ion 5

ion 7


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From lab to plant

• Next phases will build upon successof Phase 1 (2009) to transfertechnology from the lab to field testing

• Phase 2 (2010) focus on secondaryscreening for other desirableproperties

• Phase 3 (2011) focus on blendoptimization and field testing withSandia National Laboratories

• Will work closely with customers totest HTF in pilot plants before full

scale deployment



From lab to plant

R&DComponent

testingSystemtesting

Pilot plantCommercial

plant

1-10 g 10 kg 1000 kg 100 tons 10,000 tons

Must work with leadingCSP technology

developers to bringHTF from lab to plant


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Summary

• Halotechnics has developed a novel salt mixture suitable for use as a heattransfer fluid in CSP plants, increasing their efficiency and reducing theircost

• The heat transfer fluid has a broad operating range (75 °C to 500 °C)

• Halotechnics will continue to optimize and field test the heat transfer fluid

with industry partners in order to bring the material to market

Documents

Deep Eutectic Salt Formulations Suitable as Advanced Heat Transfer Fluids