The principal concept of the European DeepU project pertains to an innovative drilling technology poised to redefine the parameters of geothermal development and utilization through improved access to deep geothermal resources. The overarching objective is to establish a deep ( greater than 4 km) closed-loop connection in the form of a U-tube exchanger, achieved by developing rapid and efficient laser drilling technology, thus augmenting the availability of deep geothermal resources for low-carbon heating and potential power generation. This document presents the most recent findings from laboratory-scale laser drilling experiments conducted with a newly designed and manufactured drilling system. A laser drill head has been integrated with specialized drill strings that facilitate the coupled action of laser and cryogenic gas, effectively spalling, melting, evaporating, and cooling even the hardest rocks. The fine particles of the drilled rock are expelled to the surface in the gas stream via the borehole annulus. Detailed temperature control analysis and innovative laser lenses are employed to convey heat and sustain drilling. Additionally, it is essential that gases remain cryogenic across extended distances. Laboratory tests with the novel lightweight laser and gas processing drill head were conducted within a press container equipped with monitoring devices. Both an optical camera and a thermal camera monitor the process. The prototype drill head has been developed, merging the laser system with a novel drill-string design capable of enduring the combined action of laser and cryogenic gas. The interactions between the laser and rock, including thermal spallation, melting, and vaporization, were examined utilizing advanced analytical techniques such as thermography, photogrammetry, and electron microscopy to elucidate the physical nature of the drilling process. Subsequently, the feasibility and efficiency of laser drilling were evaluated, allowing for a direct comparison with conventional mechanical drilling methods. Under the current laser configuration, spallation emerges as the most efficient mechanism for rock removal and penetration, while melting and evaporation act as secondary processes. The flow of cryogenic gas facilitates drilling by effectively evacuating spalled particles. The meticulous optimization of laser parameters and experimental setups, in conjunction with microscopic examinations of the drilled rocks, has unveiled macro- and micro-scale phenomena that contribute to the successful development of this innovative drilling method. Additionally, the project assesses the potential for exploitation and economic implications of the developed drilling technology through numerical simulations calibrated according to laboratory data. Furthermore, the legislative considerations and environmental standards pertinent to the proposed solution are also evaluated. The high-risk innovation presented in DeepU can potentially make geothermal energy systems accessible everywhere in a targeted and demand-oriented manner. It would provide a complementary approach and an alternative solution to traditional energy storage, power and heat generation, thus decentralizing the energy supply in areas currently considered uneconomic.

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