Assessment and modelling of the waste heat availability from gas turbine based CHP systems for ORC systems

This paper presents the findings of modelling of waste heat availability from a Combined Heat and Power (CHP) system with a rated electrical output of 4.35 MW and steam production of 8,165 kg/hr at 16 barg. The model has been developed using HYSYS Dynamics™. The amount of waste heat available from the CHP system is dependent on the ambient air, steam production, and gas turbine power output. A Pitot traverse measurement across the duct was undertaken to determine the actual amount of waste heat available from the CHP system. The measurements were conducted in accordance to BS EN 15259:2007 standards. The simulation results of waste heat availability have been compared to experimental data at various CHP power outputs. The HYSYS Dynamics™ model waste heat calculation was shown to be 5.3% lower than experimental waste heat measurements. An analysis of the waste heat availability by both modelling and experiment was done which shows that the CHP system waste heat available between 3.82 MW and 5.09 MW. Recovering this low grade heat from the CHP system using Clean Cycle™ 125 ORC systems generates between 217 kW and 344 kW of electricity, respectively. Increases of 2.3% in electrical efficiency of the CHP system are predicted.