The Algae Raceway Integrated Design (ARID) minimizes diurnal and seasonal temperature fluctuations and maintains temperature within the optimal range, between 15 and 30 degrees C, during day and night and during all seasons in Tucson, Arizona. The system regulates temperature by adjusting the water surface area and thus regulates the energy transfer to and from the atmosphere and raceway. A temperature model of the raceway was developed and was based on a standardized energy balance model for agricultural crops. The model includes the Penman-Monteith evapotranspiration equation, long wave radiation, short wave radiation, sensible heat transfer (convection) and soil heat flux. The temperature model predicted minimum daily raceway water temperature within 1-2 degrees C over a range of atmospheric conditions during a 21 day algae growth experiment. Because the model is based on standard agricultural weather station data, it can be used in any location that is in proximity to an agricultural weather station. The model automatically downloads data from any weather station in Arizona, allows specification of various cover and liner conditions, specifies the timing of circulation, and has a dynamic simulation mode. (C) 2012 Elsevier Ltd. All rights reserved.