Geothermal energy has emerged as one of the viable options in a future clean energy based society. It poses a nearly inexhaustible resource with a worldwide potential. As pointed out in several recent publications, engineered geothermal systems (EGS) represent the future development of geothermal energy. These systems are still in the development stage while commercialization is lurching in the near future. The common concept representing an EGS relies on engineered fractures for permeability and heat transfer area. This paper elaborates on a different and novel approach to the EGS concept, where wellbores instead of fractures are used. The system consists of a production well and an injection well interconnected by drilled wellbores. The wellbores act as a subsurface heat exchanger with a limited, but well defined heat transfer area. The result is a system that can be controlled and adapted to the specific thermal and geological structure of the site and that reduces the uncertainties regarding reservoir lifetime, thermal breakthrough, connectivity and short-circuiting. Since there is no fracturing involved, the construction of the system does not cause seismic events, the system can, therefore, be built directly within populated areas to provide heat and power where it is needed. The thermal performance of this type of system is characterized by an initial decline in thermal effect which reaches a semi-steady state after a few years. Thus the system has to be dimensioned for it’s performance at year 20 or 30 of operation. Interestingly, the performance between 30 and 50 years degrades with only 1 %, thus showing the long term sustainability of the concept. This paper presents the concept and demonstrates its performance based on geological prerequisites.

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