In this paper a simplified temperature model for raceway reactors is developed, allowing
to determine the temperature of the microalgae culture as a function of reactor design and
environmental conditions. The model considers the major phenomena taking place in raceway
reactors, especially heat absorption by radiation and heat losses by evaporation among others.
The characteristic parameters of the model have been calibrated using genetic algorithms, next
being validated with a long set of more than 50 days covering different weather conditions. It
is worth to highlight the use of the developed model as a tool to analyze the influence of the
temperature on the performance of microalgae cultures at large scale. As example, the annual
variation of the performance of up to five different microalgae strains has been determined
by computing the temperature index, thus the normalized value of performance of whatever
microalgae at the real temperature with respect to that achievable at optimal temperature can
be established. Results confirm that only strains tolerant to wide ranges of temperature can
be efficiently produced all the year around in large scale outdoor raceway reactors without
additional temperature control systems