Absorber coatings, which switch their emissivity depending on the temperature, offer a wide protection against overheating of solar thermal collectors. At temperatures in the operating range of a collector, these coatings have a very low emissivity for heat radiation to reach low heat losses and a high collector efficiency. At higher temperatures, the emissivity increases up to multiple, raising the collector heat losses significantly. This ensures that the collector cannot overheat. We develop these new coatings and support industrial realization.