A Simulation Study Of A Solar Thermal Driven Organic Rankine Cycle System

Organic Rankine cycle has not been implemented for low-temperature heat utilization although the opportunity for its application has increased after the recent advancements in solar thermal.This study is focused on thermodynamic analysis and parametric study of two organic Rankine cycles.Furthermore,exergy and energy flow analysis is performed to improve the design and improve energy utilization.For this study,the following achievements has been carried out1)Optimization of each component of the organic Rankine cycle is carried out on Aspen Plus.2)Two different configurations(ORC and RORC)are modeled in Aspen Plus v10.Both models are simulated under the same boundary conditions for the fair comparison of results.Optimization of both configurations is carried out to find out the efficiency improvement factors and limitations.3)Studied the effect of turbine pressure ratio on the power output and also investigated the effect of increasing cooling water temperature on power output and overall efficiency of the system.The results obtained from simulation are as follows1)It is found that Pump discharge pressure increases the overall output of the organic Rankine cycle.For the current study,pressure increases from 5 bar to 10 bar results in the energetic efficiency increase from 6.5 % to 10 %.The increase of efficiency is also the function of hot water outlet temperature which also decreased meaning that better heat transfer is observed by increasing pressure.2)For the same inlet pressure,RORC performed 1.7 % better than ORC.It is found out that the hot water outlet temperature is 15 °C lower for the same boundary conditions as ORC.3)The outlet pressure of turbine effects the power output of the organic Rankine cycle.Decreasing outlet pressure from 2 bar to 1.7 bar results in an increase of 1 k W to 0.5 k W power.But there is the limit below which outlet pressure cannot be decreased.It is found out the model cannot be simulated below 1.5 bar.It is also observed that optimal outlet pressure in RORC is lower at 1.75 bar than the optimal pressure in ORC at 1.95 bar.4)The inlet temperature of cooling water in condenser effect the performance of the system.During the simulation temperature increase from 20-30 °C is tested and it is investigated that more area of the heat exchanger is required to get 100 % liquid at the inlet of the pump.5)During simulation Work output and input for both RORC and ORC are analyzed.In the case of ORC 1 k W and in case of RORC 0.364 k W of power input is required.It is found out that heat gain from regenerator also affect the power consumption of the pumpThis study also formulates a relationship between turbine pressure ratio,heat transfer fluid temperature,and power output.It will provide a guideline for the design and sizing of components of an organic Rankine cycle.For the same boundary condition,regenerative organic Rankine cycle shows a 20.97% exergy efficiency improvement over the organic Rankine cycle.