Organic rankine cycles combined with thermochemical heat transformers to enhance the power output from waste heat

The conversion of waste heat into electricity in organic Rankine cycles (ORCs) is often limited by the incomplete utilization of the heat source due to the lack of adequate heat sinks below the pinch point. In this context, low temperature thermochemical sinks could provide new opportunities of heat integration, which have been largely overlooked until now. This study investigates the coupling of organic Rankine cycles with chemical heat pumps (i.e. thermochemical heat transformers). By taking advantage of the pressure dependence of the chemical equilibrium, a low grade heat source drives an endothermic reaction, leading the production of higher temperature heat source (heat upgrade) through an exothermic reaction. The upgraded heat can then be converted to power. Different chemical compounds and integration schemes have been investigated to optimise the ORC performance. The proposed integrated system improves by 7.5% the power output of an optimized ORC.