Binary and ternary alkali polyphosphates (MPO3, M = Li, Na, K) for thermal energy storage

Hieu Pham Sy (1, 2) , Doan Pham Minh (3, 2) , Abdoul Razac Sane (2) , Hoan Nguyen Xuan (1) , Nawal Semlal (4) , Rachid Boulif (5) , Alain Germeau (6) , Claudia Toussaint (6) , Patrick Sharrock (2) , Ange Nzihou (2)

1 VNU - Vietnam National University [Hanoï]
2 RAPSODEE - Centre de recherche d'Albi en génie des procédés des solides divisés, de l'énergie et de l'environnement
3 DTU - Duy Tan University
4 OCP SA
5 UM6P - Université Mohammed VI Polytechnique [Ben Guerir]
6 Prayon SA

Up-to-date, solar salt (a mixture of 60 mass% NaNO3 and 40 mass% KNO3) is practically the only media for thermal energy storage (TES) in concentrated solar power (CSP). This commercial product’s utilization is limited below 550 °C to avoid an irreversible thermal decomposition. The development of new performing TES materials is decisive for the deployment of CSP technology. Our recent work reported promising results obtained with mono-alkali polyphosphate (M-PO3) as TES materials. These materials can work up to around 900 °C, but their melting point is still high, which is at least 628 °C. In order to lower their melting point, binary and ternary mixtures of alkali polyphosphates are investigated in this work. Dif- ferent mixtures made of two or three alkali polyphosphates were prepared and studied using thermal analysis methods. The most promising mixture found in this work was the ternary Li-Na-K-PO3, which contained 33.3% (mol%) of each alkali metal. This mixture can be used as a liquid TES material in the temperature range of 398 to 900 °C. The results open new prospects for the development of the thermal energy storage field.

Mots clés: Alkali polyphosphate; Thermal energy storage; Ternary; Na-K-Li-PO3; Na-K-Li-PO 3

Domaines: Sciences de l'ingénieur [physics]

Hieu Pham Sy, Doan Pham Minh, Abdoul Razac Sane, Hoan Nguyen Xuan, Nawal Semlal, et al.. Binary and ternary alkali polyphosphates (MPO3, M = Li, Na, K) for thermal energy storage. Journal of Thermal Analysis and Calorimetry, 2021, 146, pp.2027-2033. ⟨10.1007/s10973-020-10346-1⟩. ⟨hal-03012742⟩