Novel design for tri-generation cycle with Parabolic Trough Collector: An exergy-economic analysis

Abstract

In this work, a new design for the tri-generation cycle with solar energy resources using Therminol 66 in its parabolic thermal solar collectors has been proposed. The solar collectors absorb the solar energy and pass that to the Organic Rankine Cycle (ORC) with n-octane, n-pentane, n-hexane, and n-heptane working fluids. Besides, the energy loss of the evaporator of the organic Rankine cycle has been used for producing thermal load and that of condenser has been utilized for the cooling load generation. In this research, the main innovation is the use of an organic Rankin cycle condenser as the energy source of the absorption refrigeration cycle. Also, the effect of different fluids such as n-octane, n-heptane, n-pentane, and n-hexane on the operation of the whole system has been investigated. The validation of the results has been carried out which showed acceptable agreement and confirms the accuracy of the proposed model. The power coefficient and exergy factor of the cycle have been obtained as 32.72 and 23.83%, respectively. Furthermore, the highest exergy destruction of the proposed tri-generation system occurs in the steam generator, the generator of the absorption refrigeration cycle, and turbine of organic Rankine cycle by 14742 KW, 3974 KW and 3374 KW with the exergy destruction percentage of 54%, 15%, and 12%, respectively. In the economic aspect of the proposed system, the highest cost is for the evaporator of the absorption refrigerator system with 69.71 dollars per hour and the second and third highest cost are for HRSG and the turbine with 32.4 and 30.33 dollars per hour which have 41%, 19% and 18% of the total cost of the proposed system, respectively. Also, the results show that the most costs of waste are for the generator, turbine, and SHX heat exchanger which waste 6.639, 5.586 and 4.22 dollars per hour with 34%, 29%, and 22% of the total cost of waste, respectively. Moreover, it can be seen that by increasing the temperature of the solar collector from 200° to 500°, the first-law efficiency decreases from 37.6% to 28.6%, the second-law efficiency decreases from 40.15% to 17.29% and the total cost decreases from 4.78 to 4.77 dollars per Gigajoule.