Adding phase change nanoparticles into fluid enhances heat capacity, but supercooling of nanoparticles requires fluid working with large temperature difference, which limits heat transfer benefit. This Letter describes a method to reduce supercooling by encapsulating indium nanoparticles in non-melting shells of semi-crystalline silica derived from sodium silicate. Not only can the rough surface and matching structure of shells prevent molten cores from leakage or agglomeration, they allow heterogeneous nucleation during, solidification of nanoparticles and reduce supercooling up to 30 degrees C. The operating parameter including overheating, heating and cooling rates can be adjusted to reduce supercooling by 7 degrees C for silica shells derived from tetraethylorthosilicate. Published by Elsevier B.V.