A dynamic model of a solar driven trigeneration system based on micro-ORC and adsorption chiller prototypes

Abstract

The aim of this work is to present a dynamic model of an innovative small-scale trigeneration system implemented by means of TRNSYS. The modelled system is composed of a solar field, a low-temperature micro-Organic Rankine Cycle plant (ORC) and an adsorption chiller (AC). In particular, the main innovation of the model is the utilization of a micro-ORC machine and adsorption chiller implemented on TRNSYS by user-defined types that use experimental performance data obtained by a full characterization of ORC and AC prototypes, implemented at University of Bologna and at CNR - ITAE respectively. The considered micro-ORC system is driven by a reciprocating piston expander prototype, made of three radial cylinders with total displacement of 230 cm3. The other components are two brazed plate heat exchangers as evaporator and recuperator, a prototypal gear pump and a shell-and-tube condenser. The adopted working fluid is HFC-134a, suitable for heat source temperature up to 100 °C and characterized by a global warming potential (GWP) equal to 1430. The adsorption chiller prototype is characterized by an innovative architecture, employing 3 adsorbers connected to a single evaporator and condenser and by the use of hybrid adsorbers, realized embedding microporous Silica Gel loose grains into aluminium flat tube heat exchangers, previously coated with the Mitsubishi AQSOA FAM Z02 sorbent. The cooling machine has a nominal capacity of 4.4 kWc. Both the AC and ORC prototypes can be driven by low grade thermal energy (<90°C) from waste heat, industrial processes or renewable energy sources. The model realized is easily adaptable to any other plant by redefining the different subsystems of the desired technology and, in conclusion, this study has highlighted the promising characteristics of ORC and AC technologies in tri-generative configuration, with a 63% of global efficiency.