Thermodynamic analysis of the off-design performance of a micro solar organic Rankine cycle trigeneration system

Organic Rankine Cycle (ORC) systems are considered as one of the cost suitable technologies toproduce electricity from low-temperature sources. ORC units can efficiently convert low-temperaturesolar energy into electric and thermal power. Independently from the solar technology used, the hourlyand the seasonal fluctuations of solar energy entail challenging dynamic effects and bring these systemsto operate in off-design conditions. Such effects are even more influential at micro-to-small scalesgranting paramount importance to the comprehensive understanding of their behavior.In this study, the annual performances of a 4 kWe/50 kWth solar ORC trigenerative system forresidential applications are numerically investigated. Four different modeling approaches commonlyused in annual system-level simulations of ORC systems are compared. These models differ in thesystem-level modeling approach and the components modeling method. The analysis has shown thatthe simplest ORC model results in the lowest discrepancy compared to the model with the leastassumption, in which the components are modeled empirically, and the high and low pressures of thesystem are found iteratively. The difference between the produced electric energy using the four modelsis significantly higher in hot months, in which the average temperature of the water tank is high due tothe requirements of the vapor generator of the absorption chiller. In this case, the expander pressureratio drops drastically depending on the system model algorithm, which affects the produced electricpower depending on the adopted expander model. On the contrary, the discrepancy between the modelsfor the produced thermal energy is negligible.     «

Organic Rankine Cycle (ORC) systems are considered as one of the cost suitable technologies toproduce electricity from low-temperature sources. ORC units can efficiently convert low-temperaturesolar energy into electric and thermal power. Independently from the solar technology used, the hourlyand the seasonal fluctuations of solar energy entail challenging dynamic effects and bring these systemsto operate in off-design conditions. Such effects are even more influential at micro-to-small scalesg...     »