Extraction of heat from multiple-fractured dry hot rock

A brief summary of theoretical solutions for the extraction of heat from multiple-fractured dry hot rock is presented. The analysis is based on an infinite series of parallel vertical fractures of uniform aperture and separated by blocks of homogeneous and isotropic impermeable rock with a uniform spacing between fractures. Cold water enters at the bottom of the fractures and the solutions are given in terms of dimensionless parameters from which the exiting water temperature at the top of the fractures can be determined. An example of the application of the theory is given to demonstrate how a multiple, fractured system provides a more efficient mechanism for heat extraction than a single fracture in dry hot rock.