Innovative CHP concept for ORC and its benefit compared to conventional concepts. (1st December 2016) - Wieland, Christoph
Highlights: Two-stage ORC with turbine bleeding is investigated for combined heat and power. Two-stage concept shows high flexibility for representative isentropic fluids. Performance with siloxane is investigated for different ORC-CHP concepts. Annual produced electricity is used to compare revenues for different concepts. Two-stage concept produces more electricity for high cover ratios of heat demand. Abstract: Combined heat and power is highly favorable in order to prevent harmful CO2 -emissions. Besides that, economic benefits go along due to higher full load operation hours. The present work investigates the flexibility and suitability of different Organic Rankine Cycles for combined heat and power concepts, since it can play a significant role to achieve climate goals. An integrated concept for heat decoupling based on a two-stage Organic Rankine Cycle with regenerative preheating from turbine bleeding is introduced. The heat extraction to the district heating system is directly in line with the receiver tank for the preheating. The flexibility of this integrated concept is determined for different isentropic fluids and siloxanes. Under general circumstances it is more favorable to apply a recuperator for dry fluids such as siloxanes, due to the high amount of sensible heat after the turbine outlet. It has been shown in this work, that the proposed regenerative preheating concept is more beneficial for combined heat and power. While other concepts are only applicable for base load heat demand or for peak load heat demand, this concept is suitable for the entire range of cover ratios of a district heating system. Thus, this concept offers highest flexibility in application and a good capacity utilisation.