Evaluation of Formate Salt PCM’s for Latent Heat Thermal Energy Storage

Samuel Gage, Prashant Sharan, Craig Turchi and Judy Netter
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Samuel Gage: National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA
Prashant Sharan: Los Alamos National Laboratory, M711, Los Alamos, NM 87545, USA
Craig Turchi: National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA
Judy Netter: National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA

Energies, 2021, vol. 14, issue 3, 1-10

Abstract: This work examines formate salts as potential phase change materials (PCMs) for middle-high temperature (≤250 °C) latent heat thermal energy storage applications. The thermophysical properties of three formate salts were characterized: pure sodium formate and binary blends of sodium/potassium formate and sodium/calcium formate. The stability of formate PCM’s was evaluated by thermal cycling using differential scanning calorimetry where sodium formate and sodium/potassium formate appeared stable over 600 cycles, while sodium/calcium formate exhibited a monotonic decrease in heat of fusion over the test period. A longer test with sodium formate led to gas release and decomposition of the salt. FTIR analysis of the PCM showed degradation of formate to oxalate. T-history experiments with 50-g PCM quantities demonstrated a bulk supercooling of only 2–3 °C for these salts. Thermal conductivity enhancement of over 700% was achieved by embedding aluminum in the solid PCM. Finally, mild carbon steel was immersed in molten sodium formate for up to 2000 h. Sodium formate was found to be non-corrosive, as calculated by mass loss and confirmed by cross-sectional high-resolution microscopy. FTIR analysis of the PCM after 2000 h shows oxidation at the free surface, while the bulk PCM remained unchanged, further indicating a need to protect the formate from atmospheric exposure when used as a PCM.

Keywords: phase change materials; formate salts; latent heat thermal energy storage; thermal cycling; supercooling; thermal conductivity enhancement; corrosion (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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