This essay describes the possibility to generate electricity by Organic Rankine Cycle (ORC) technology, so far unused waste heat in terms of hot flue gas. The so called ORC technology is able to produce electric power from low grade heat sources. A computer program was developed in PYTHON to calculate the electricity output by given heat source data. The program considers two different plant designs, one with and the other without internal heat exchanger. In the simulation hot flue gas and thermal oil represent the heat sources and cooling water was assumed to be the heat sink. This thesis describes how to apply the program and how to evaluate the results from calculations. Furthermore some parameter studies have been carried out in order to get a first rough magnitude of order about power output and thermal efficiency for given heat source data. Seven different organic fluids have been investigated and implemented into the program. Basically four different fluids (Isobutane, Isopentane, Pentane and Cyclopentane) show ideal performance for flue gas temperatures up to 300C (573.15K) in both plant designs. The developed program considers the interaction of heat source fluids with ORC plant. The program also calculates heat transfer properties from heat exchangers. These data could also be used for further economic studies but this is not content of this essay.