The performance of a prism shaped storage solar collector with a right triangular cross sectional area was investigated numerically. The ANSYS software release 5.4 was used for this purpose. Modifications were introduced embodying water properties and making the software compatible with the different types of loads.The behavior of parameters related to performance such as temperature, velocity distributions, mean tank temperature, total stored energy and the best location of the inlet and outlet water flows were investigated systematically. A new idea of introducing an internal horizontal adiabatic partition was investigated. The length of the partition and its location along the height of the storage collector was analyzed to give optimum stored energy and maximum possible mean tank temperature. The results showed that the performance of the storage collector can be improved by using the partition.The mean tank temperature reached 37 degreesC in the 1st of January and 46 degreesC in the 21st of June without partition. The results of this study showed good agreement with the theoretical and experimental results available in the literature. (C) 2003 Elsevier Ltd. All rights reserved.