Abstract
Modular and scalable distributed generation solutions as combined cooling, heating and power (CCHP) systems are currently a promising solution for the simultaneous generation of electricity and useful heating and cooling for large buildings or industries. In the present work, a solar-heated trigeneration approach based on different organic Rankine cycle (ORC) layouts and a single-effect H2O/LiBr absorption heat pump integrated as a bottoming cycle is analysed from the thermodynamic viewpoint. The main objective of the study is to provide a comprehensive guide for selecting the most suitable CCHP configuration for a solar-heated CCHP system, following a systematic investigation approach. Six alternative CCHP configurations based on single-pressure and dual-pressure ORC layouts, such as simple, recuperated and superheated cycles, and their combinations, and seven organic fluids as working medium are proposed and compared systematically. A field of solar parabolic trough collectors (SPTCs) used as a heat source of the ORC layouts and the absorption heat pump are kept invariant. A comprehensive parametric analysis of the different proposed configurations is carried out for different design operating conditions. Several output parameters, such as energy and exergy efficiency, net electrical power and electrical to heating and cooling ratios are examined. The study reveals that the most efficient CCHP configuration is the single-pressure ORC regenerative recuperated superheated cycle with toluene as a working fluid, which is on average 25% and 8% more efficient than the variants with single-pressure simple cycle and the dual-pressure recuperated superheated cycle, respectively. At nominal design conditions, the best performing CCHP variant presents 163.7% energy efficiency and 12.3% exergy efficiency, while the electricity, cooling and heating productions are 56.2 kW, 223.0 kW and 530.1 kW, respectively.
Highlights
One of the potential applications that combine the use of low or medium temperature solar energy and organic Rankine cycle (ORC) is a trigeneration thermal system, which can be defined as combined cooling, heating and power (CCHP) production simultaneously from the same energy source [1]
The objective of this work is twofold: on one hand, to provide a comprehensive guide for selecting the most suitable solar-heated CCHP configuration in terms of system energy and exergy efficiency by means of a fair systematic comparison between the six layouts and the seven working fluids; on the other, to evaluate parametrically all the CCHP alternatives for a wide range of solar field outlet temperature and ORC condensation temperature aiming for the design of the most efficient system that may be coupled with buildings or industries for combined generation, or as a back-up, of electricity, cooling and heating
The CCHP system assessed in this study is mainly composed of an ORC as a power generator, which is driven by a field of solar parabolic trough collectors (SPTCs)
Summary
One of the potential applications that combine the use of low or medium temperature solar energy and organic Rankine cycle (ORC) is a trigeneration thermal system, which can be defined as combined cooling, heating and power (CCHP) production simultaneously from the same energy source [1]. The objective of this work is twofold: on one hand, to provide a comprehensive guide for selecting the most suitable solar-heated CCHP configuration in terms of system energy and exergy efficiency by means of a fair systematic comparison between the six layouts and the seven working fluids; on the other, to evaluate parametrically all the CCHP alternatives for a wide range of solar field outlet temperature and ORC condensation temperature aiming for the design of the most efficient system that may be coupled with buildings or industries for combined generation, or as a back-up, of electricity, cooling and heating
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