Investigation of calcium hydroxide powder for thermochemical storage modified with nanostructured flow agents

•Experimental investigation of calcium hydroxide with nanostructured additives.•Comparison of powder flowabilities before and after thermochemical cycling.•Analysis of heat release, formation of side products and agglomeration.•Formation of calcium aluminates adds to heat release during hydration.•Agglomeration (>1 mm) improves flow behaviour of thermochemical storage material.