Schmidt, H.H.Schmidt2022-03-082022-03-081992https://publica.fraunhofer.de/handle/publica/302631The invention refers to a system for the use of geothermal heat for heating display components, in particular traffic signs by means of a heat pump or a heat pipe. The transfer of the heat from the heat pipe to the display element is adjustable. The heating of the display element is to remove frost, ice or dew.de608621697patent1990-4036729