With the objective of addressing issues related to the temperature control of a solar closed photobioreactor (PBR), a laboratory set-up representative of an intensified closed flat panel PBR was designed. Only its thermal behaviour was considered, with no cultivation of microalgae. It was characterized indoors under controlled artificial irradiation and outdoors under solar irradiation on sunny days in summer. A simplified thermal model to predict the temperature time course was developed and validated by comparison with experimental results. The thermal model was then used as a simulation tool to investigate relevant parameters influencing thermal behaviour, such as the optical properties of the illuminated surface and the surrounding wind speed. A heat balance was applied for different cases to determine the energy consumption during one year of operation with temperature regulated in a range suitable for microalgae growth. (C) 2011 Elsevier B.V. All rights reserved.