Hybridisation of biomass and concentrated solar power systems in transcritical organic Rankine cycles: A micro combined heat and power application

The purpose of the work is to analyse the performance of an innovative fully renewable micro-hybrid energy system for combined heat and power generation. The apparatus is based on a transcritical Organic Rankine Cycle unit, fuelled by a conventional biomass boiler and a concentrated solar power system consisting of parabolic trough collectors. A thermodynamic model has been developed and the proper plant configurations have been defined through a parametric analysis. The possible application to the residential sector has been investigated considering typical domestic users in Southern Italy. The performance of the innovative micro combined heat and power system has been compared with the corresponding single-source systems (solar-only and biomass-only units). The investigation demonstrates that biomass/solar hybridisation allows reducing the biomass consumption, increasing the maximum operating hours, and improving the global system efficiency. Furthermore, the biomass integration raises the annual net solar-to-electric efficiency. In fact, hybridisation enables a better exploitation of the lowest solar radiations that are not sufficient to drive a full-solar Organic Rankine Cycle and to overcome the intermittency of the solar source.