Exergoeconomic comparison and optimization of organic Rankine cycle, trilateral Rankine cycle and transcritical carbon dioxide cycle for heat recovery of low-temperature geothermal water

Abstract

Depleting fossil fuel resources and the horrible environmental impacts due to burning fossil fuels emphasize the importance of using renewable energy resources such as geothermal and solar energies. This paper compares performance of CO2 transcritical cycle, organic Rankine cycle, and trilateral Rankine cycle using a low-temperature geothermal heat source. Thermodynamic analysis, exergetic analysis, economic analysis, and exergoeconomic analysis are applied for each of the aforementioned cycles. In addition, a sensitivity analysis is performed on the system, and the effects of geothermal heat source temperature, evaporator pinch point temperature, and turbine inlet pressure on the cycle's performance are evaluated. Finally, the systems are optimized in order to minimize product cost ratio and maximize exergetic efficiency by using the genetic algorithm. Results indicate that the maximum thermal efficiency is approximately 13.03% which belongs to organic Rankine cycle with R123 as working fluid. CO2 cycle has the maximum exergetic efficiency, equals to 46.13%. The minimum product cost ratio refers to the organic Rankine cycle with R245fa as working fluid. Moreover, sensitivity analysis shows that increasing geothermal heat source temperature results in higher output power, product cost ratio, and exergy destruction ratio in all cycles.

Comparative exergetic sustainability analysis of subcritical and supercritical organic Rankine cycle plants for a waste heat recovery application

“…The exergetic sustainability analysis of an energy system first requires a comprehensive exergy study, 33 entailing the design of all the system components to satisfy the mass and energy balance equations specified by the First Law of Thermodynamics, and the exergy balance equation imposed by the Second Law, given respectively by equations (1)–(3) 34,35 :where normalm˙ represents the mass flow rate of a working substance flowing in a given stream, h denotes the specific enthalpy, normalQ˙ is the heat flow across a component, normalW˙ represents the work rate flow through a component, T is the state temperature, e the state specific exergy, and I˙ connotes irreversibility, which is the same as the rate of exergy destroyed in a given component. The flows in and out of a component are represented by subscripts i and o respectively, while c and a denote respectively the component surface and the ambient environment.…”

“…The exergetic sustainability analysis of an energy system first requires a comprehensive exergy study, 33 entailing the design of all the system components to satisfy the mass and energy balance equations specified by the First Law of Thermodynamics, and the exergy balance equation imposed by the Second Law, given respectively by equations ( 1)-(3) 34,35 :…”

Experimental analysis of organic Rankine cycle power generation system with radial inflow turbine and R245fa

“…Organic Rankine cycle (ORC) power generation is an environmentally friendly power generation technology that does not pollute the environment. 1 ORC power generation systems utilise the low boiling point of organic fluids to generate electricity, such as by using low-temperature industrial waste, 2 geothermal energy, 3 biomass 4 and solar energy 5 as heat sources. As ORC systems use water and air in the environment as cold sources, they do not consume non-renewable resources such as fossil fuels and nuclear energy.…”