Thermodynamic and Performance Study of Solar Regenerative Organic Rankine Cycle System for Use in Residential Micro-Combined Heat and Power Generation

Abstract

Abstract A continued increase in both energy demand and greenhouse gas emissions (GHGs) call for utilising energy sources effectively. In comparison with traditional energy set-ups, micro-combined heat and power (micro-CHP) generation is viewed as an effective alternative; the aforementioned system’s definite electrical and thermal generation may be attributed to an augmented energy efficiency, decreased capacity as well as GHGs percentage. In this regard, organic Rankine cycle (ORC) has gained increasing recognition as a system, which is capable for generating electrical power from solar-based, waste heat, or thermal energy sources of a lower quality, for instance, below 120 °C. This study focuses on investigating a solar-based micro-CHP system’s performance for use in residential buildings through utilising a regenerative ORC. The analysis will focus on modelling and simulation as well as optimisation of operating condition of several working fluids (WFs) in ORC in order to use a heat source with low-temperature derived from solar thermal collectors for both heat and power generation. A parametric study has been carried out in detail for analysing the effects of different WFs at varying temperatures and flowrates from hot and cold sources on system performance. Significant changes were revealed in the study’s outcomes regarding performance including efficiency as well as power obtained from the expander and generator, taking into account the different temperatures of hot and cold sources for each WF. Work extraction carried out by the expander and electrical power had a range suitable for residential building applications; this range was 0.5–5 kWe with up to 60% electrical isentropic efficiency and up to 8% cycle efficiency for 50–120 °C temperature from a hot source. The operation of WFs will occur in the hot source temperature range, allowing the usage of either solar flat plate or evacuated tube collectors.