title: Introduction by guest editors.
authors.affiliation: Institut de chimie et procédés pour l'énergie, l'environnement et la santé (ICPEES), CNRS, University of Strasbourg, 25 rue Becquerel, 67087 Strasbourg, France. nkeller@unistra.fr.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Keller
authors.affiliation: PSA (Plataforma Solar de Almería), CIEMAT, Crta Senés km 4, Tabernas, Almería 04200, Spain. Sixto.Malato@psa.es.
authors.forename: Sixto
authors.initials: S
authors.lastname: Malato