Synergetic characteristics of three-dimensional transient heat transfer in geothermal reservoir combined with power conversion for enhanced geothermal system

Abstract

This paper establishes a complete enhanced geothermal system (EGS) during 30 years system life cycle. The power generation system is established by an ORC (Organic Rankine Cycle) system. Then, the two-dimension numerical model with the injection well and production well is established on the basis of circular cylindrical coordinates by FVM (Finite volume method). Meanwhile, a geothermal reservoir with one primary fracture is established based on the porosity model by FEM (Finite element method). On the basis of this complete numerical model, the coupled relationship between heat transfer and power generation is investigated by temperature difference θ, mass flow rate, and the structure of primary fracture, respectively. The temperature difference θ is defined by the temperature difference between the outlet temperature of production well and the evaporating temperature to analyze the performance of power generation. Then, the flow rate of the injection well and the structure of fracture are investigated to analyze for the performance of power generation. For the structure of fracture, the plane angle α and the plane angle β are employed to describe the vertical fracture and the horizontal fracture, respectively. The results show that a higher temperature difference θ leads a higher net work output and exergetic efficiency. And the flow rate has a more significant impact on the performance of power generation than the temperature difference θ during the 30 years system life cycle. For the primary fracture, a vertical fracture has a stronger impact on the outlet temperature of production well than that of a horizontal fracture.