Abstract: A method for obtaining useful energy from geothermal heat. A coaxial tube is provided which includes an inner and outer tube connected to together in an end section of the coaxial tube. The coaxial tube is introduced into a deep bore in the earth and a thermal medium liquid under standard conditions is introduced into the outer tube and flows in the direction of the end section of the coaxial tube. The thermal medium is heated while absorbing geothermal heat, passes through a phase transition in the region of the end section, passes over in gaseous form into the inner tube, and flows upward therein up to an upper end of the coaxial tube located at the Earth's surface. A flow generator for generating electric energy is operated using the flowing, gaseous thermal medium and the kinetic energy of the flowing gaseous thermal medium is converted to obtain usable energy.