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Argonne National Laboratory and project partner Ohio Aerospace Institute, under the National Laboratory R&D competitive funding opportunity, worked to design, develop, and test a prototype high-temperature and high-efficiency thermal energy storage (TES) system with rapid charging and discharging times. By increasing the efficiency of TES systems, this project aimed to lower the capital costs of concentrating solar power (CSP) systems.

Approach

Photo of a black and white porous material magnified 50 times by a microscope.

Current TES technologies use sensible or latent heat storage systems.  In latent heat based systems typically a phase change material (PCM) is used and the heat is stored during melting of the PCM and recovered during its freezing.  Typically, salts with appropriate melting temperatures and high heat of fusion are used as PCMs.  One of the drawbacks with the PCM salts is that they are poor thermal conductors, therefore, require extremely long times to completely melt or freeze for grid scale TES systems. 

Argonne has developed a latent heat based thermal energy storage (LHTES) system that utilizes high conductivity graphite foam to enhance the thermal performance of the PCM.  For laboratory-scale tests, magnesium chloride (MgCl2) PCM was infiltrated into the pores of the graphite foam to form a composite storage media.  Using 3D thermal modeling and prototype testing, thermal performance of the LHTES has been demonstrated. 

Innovation and Results

  • Development of the LHTES system required process innovations such as infiltration of PCM in graphite foam, integration/joining of components, and controls for corrosion mitigation.
  • The thermal performance of TES system is 20 times better than that of currently available salt PCM systems. This performance advantage is key to the system’s rapid charging/discharging results.
  • Using the laboratory test data prediction of full-scale TES system shows it meets the SunShot Initiative’s performance targets.
  • Argonne’s system can realize exergetic and energetic efficiencies greater than 95% with full utilization of the PCM for the target charging/discharging times of 8 hours.
  • Argonne’s LHTES system platform can be tuned to any other temperature range of operation by selecting an appropriate PCM. The current system charges/discharges at ~700°C.
  • The LHTES system can be used as a single tank or as a modular storage system. Leads to reduction in overall capital costs as compared to current TES systems.
  • Modular design of Argonne’s LHTES system means it is easy to service the TES system installation, and individual modules may be replaced/repaired without shutting down the entire storage system.  

Publications, Patents, and Awards

Learn about other DOE competitive awards for concentrating solar power research that are in progress.