The present invention provides renewable and sustainable materials suitable for solar thermal energy conversion. Provided are methods for isolating melanin or melanin particles from the ink sac of a Cephalopoda animal as well as parameters for characterizing melanin or melanin particles, particularly their physic-chemical properties. Further provided is a solar thermal energy selective absorber material comprising melanin or melanin particles, a solar lacquer or a solar paint comprising as a pigment melanin or melanin particles and a solar thermal system comprising melanin or melanin particles. In addition, there is provided the use of melanin or melanin particles as pigment, for example for solar lacquers or solar paints, or as selective absorber for direct absorption solar collectors or for use in a heat transfer fluid and/or within a solar thermal system in general.
