Solar steam in an aqueous carbon black nanofluid

[Display omitted] •Aqueous carbon black nanofluid (CBNF) is produced.•CBNF composition is set to provide maximum evaporation efficiency (EE).•Solar steam of CBNF is produced in a parabolic concentrator at 0.76 sun.•The steam was superheated by 25 K, EE was 73%.•The experiment was carried out in Nordic solar conditions. A limited number of experimental studies report intensive steam generation in direct adsorption solar collectors with nanofluids. Most nanofluids used for these applications are produced with expensive gold nanoparticles. This contribution proposes a low-cost alternative solution made of water and carbon black nanoparticles. Our nanofluid-generated yet nanoparticle-free steam is produced in a parabolic collector with 73% efficiency and 25 °C superheat under the solar conditions in the Nordic region.