Thermodynamic analysis and optimization of a combined cooling, heating, and power system using Organic Rankine Cycles (ORC) and solar parabolic trough collectors

Abstract

At present, the interest in combined cooling, heating and power systems (CCHP) has experienced a significant growth due to their promising performances and the global trend towards renewable energy resources for distributed power generation. The trigeneration system assessed in this study is mainly composed of an ORC for power generation which is driven by a zero emissions renewable energy source coming from a field of Solar Parabolic Trough Collectors (SPTCs). A single-effect H2O/LiBr absorption heat-pump is integrated as a bottoming cycle to meet heating and cooling demands simultaneously. The main objective of this work is to provide a comprehensive guide for selecting the Organic Rankine Cycle (ORC) configuration and the most suitable organic fluid for a solar-heated CCHP system based on an ORC and a single-effect absorption heatpump. Four ORC configurations are evaluated, and twelve organic working fluids are tested in order to achieve an optimal layout from a thermodynamic point of view. For the best performing ORC configuration, a comprehensive parametric analysis is carried out for different design parameters. Several output parameters - electrical energy and exergy efficiency, net electrical power, and electrical to heating and cooling ratios - are examined. The study reveals that the most efficient ORC configuration is the recuperated superheated cycle with toluene as a working fluid. For the CCHP system at optimal design conditions, the electrical energy and exergy efficiency are 19.2% and 77.7% respectively, while the electricity, cooling and heating productions are 69.9 kW, 225.2 kW and 516.8 kW respectively.