A heat transfer system has an energy converter, a heat transfer medium, a transfer part, and a heat exchanger. The energy converter converts an energy of an energy source into an energy in a different state and generates a heat while converting the energy. The heat transfer medium is in a liquid state and receives the heat from the energy converter. The heat exchanger dissipates the heat from the heat transfer medium to an outside of the heat transfer system. The heat transfer medium contains H2O and a solute compatible with the H2O. The solute has a molecular structure including two hydroxyl groups. A length of a binding chain between an oxygen atom of one of the two hydroxyl groups and an oxygen atom of an other of the two hydroxyl groups is shorter than a length of a binding chain between two hydroxyl groups of an ethylene glycol molecule.