Micro Geothermal Generation Device

There are many places in the world with access to very high-temperature water effluents and at the same time access very cold water. This happens in many SPA thermal resources in the high mountains. The usual solution to generate electricity for those cases is using the hot source and the cold sink to install an Organic Rankine Cycle (ORC) power plant. This might be a very good solution but usually expensive and complicated to maintain and operate. In this paper, a very practical, simple, novel design is presented where the water from the hot spring is connected to a tube where vacuum pressure is produced by a Torricelli pipe or a small pump. The incoming hot water under vacuum will split in low-pressure steam and hot water. The steam flows upward and passes through a simple design axial turbine connected to a generator. The exhaust steam is sent laterally to another vertical pipe that acts as a direct contact barometric condenser, cooled with cold water from a flowing stream. Since the system itself has a small enthalpy jump, running between low and very low steam pressures, special care is made in the design to avoid as much as possible heat and pressure losses. The design of the axial vertical steam turbine involves several interesting features; the rotor and the diaphragm are 3D printed in thermoplastic. The turbine parts (fixed and rotating) are inserted in a steel pipe. The thrust bearings are made of sintered metal in oil, allowing constant lubrication. The description of the components used for the flash condensing cycle in the Geothermal Micro Generator (GMG) is presented, as well, the design for a steam turbine capable to work between low and very low pressure, concentrating the effort in the thermodynamics of the design. The GMG system contains the main elements of a classic geothermal power plan but designed as a simple distributed energy equipment.