Defining optimal configurations of geothermal systems using process design and process integration techniques

This paper presents a systematic methodology for the optimal design of geothermal systems. First, the different components of the system superstructure are separately modeled using flowsheeting software. The superstructure includes the different conversion technologies, the potential resources and the demand profiles in energy services. It covers a wide panel of conventional resources and technologies like deep and shallow aquifers, heat pumps, organic Rankine cycles for combined heat and power production, as well as emerging resources and technologies, like enhanced geothermal systems. Then, resources, technologies and demand profiles models are integrated together using process integration techniques. The configuration of the geothermal system is hence extracted from the superstructure. Finally, the performance of the integrated system is calculated and includes energy and exergy efficiency, investment costs, operating costs and district heating or electricity levelized costs. To account for the seasonal variations of the demand, a multi-period approach is used for the simulation of the superstructure, its integration and the performance calculation. The overall sequence is implemented in a multi-objective optimization framework. The methodology is illustrated by an application case study. The implications of the results are discussed in terms of important effects to be accounted for in the design of geothermal systems.