Economic system optimization of air-cooled organic Rankine cycles powered by low-temperature geothermal heat sources

• System optimization of organic Rankine cycles powered by low-temperature geothermal heat.
• Models of shell-and-tube heat exchangers, air-cooled condensers and axial turbines are included.
• Maximization of the net present value.
• Combined optimization of cycle, configuration of heat exchangers and air-cooled condensers.

In this paper, an economic system optimization of an air-cooled organic Rankine cycle, powered by geothermal heat, is performed. The goal is to find the configuration of the ORC (organic Rankine cycle) which gives the highest possible net present value for the project. The cycle parameters, heat exchanger geometry and air-cooled condenser geometry are optimized together. The developed method is applied to a case study, based on a Belgian geothermal project, after which the most important parameters are varied. It is shown that the air-cooled condenser is a crucial component from both a thermodynamic and economic point of view. The discount rate, electricity price, brine inlet temperature and annual electricity price evolution have a strong influence on the configuration and efficiency of the ORC and on the economics of the project.