In this article, a transient modeling method for the heat extraction process in the rectangular solar ponds is presented by using a finite difference technique. Firstly, the thermal behavior of the pond, during the heat extraction operation is modeled. Then the model is verified using experimental data, and the maximum observed percentage error of this method is 2.03%. This method is used to model the heat extraction from a hypothetical pond in Tehran for three months of August, September, and November. The results present the temperature profiles, the extracted heat and the rate of heat extraction. All of these parameters have the highest value in August, and the lowest values are allocated to November. Moreover, the percentages of the extracted heat during the operation are studied. For all the three months, this parameter has a high value in the first 40% of the time needed to full heat extraction. Between the 40% and 70% of the total time, the heat extraction rate reduces drastically, and after the 70% of the total time, it is almost constant at a low value. Also, the modeling results are used in a low temperature organic Rankine cycle, and it is found that for the designed pond, the pond can be used as the heat source of the cycle only in August and for 7.31 h of operation. (C) 2016 Elsevier Ltd. All rights reserved.